A SIMULATION MODEL FOR FEASIBILITY ANALYSIS OF DUAL-PURPOSE POWER PLANTS PROVIDING THERMAL ENERGY TO URBAN COMMUNITIES A DisserIaNon {or the Degree oI DI}. D. MICHIGAN STATE UNIVERSITY David Harold Curtice I977 LIBRARY \\\\‘l\\\\ m \\ \\\\\\\l Mggagmitye This is to certify that the thesis entitled A SIMULATION MODEL FOR FEASIBILITY ANALYSIS OF DUAL-PURPOSE POWER PLANTS PROVIDING THERMAL ENEng//”/ TO URBAN COMMUNITIES 4 presented by David Harold Curtice has been accepted towards fulfillment of the requirements for Ph . D degree in Systems Science Major professor Datefir 4; /77] A 07639 v ”.w‘m—fi‘ v v “.w ._.—-+.v-—_... w- . v . ""“‘ govt .I . ._.I A”, -- w.,,,,m_._-.. w"'”" Axel-purpose E at electrical ene1 atechnology that ( :iency. This study Sing dual-purpose Zemal energy to L ezergy. ABSTRACT A SIMULATION MODEL FOR FEASIBILITY ANALYSIS OF DUAL-PURPOSE POWER PLANTS PROVIDING THERMAL ENERGY TO URBAN COMMUNITIES By David Harold Curtice Dual-purpose power generation, simultaneous production of steam and electrical energy by an electric power plant (cogeneration), is a technology that offers the potential for high overall energy effi- ciency. This study details thetechnicalmand economic feasibility of using dual-purpose power plants to supply substantial amounts of thermal energy to urban communities during the production of electric energy. Possible applications of dual-purpose power plants in urban com- munities requires extensive consideration of the couplings between three basic thermodynamic components; the dynamics of electric power generation, steam transport, and the time-dependent demand for thermal energy by the community. To explore the interconnected dynamic be- havior of these urban energy systems, I develop a simulation model for use in deriving energy and economic parameters within the constraints imposed by various community and power plant characteristics. The laws of thermodynamics constrain the design of the urban energy systems considered. As a result of Second Law analysis, parameters of t'r. 10v extraction p turbine power on eluded; supplyin of low enthalpy : the total demand heating and cool: Three generi estimating techni 138 and cooling, in a variety of d cPérates to contfl community constru energy into the 1 obtained from smal Parameters of cap range potentially David Harold Curtice parameters of the steam transport components were designed to require low extraction pressures at the power plant, thus minimizing affects on turbine power output. Benefits resulting from this design scheme in- cluded; supplying a thermal energy source to the community in the form of low enthalpy steam after producing some electric energy, and reducing the total demand for low entropy energy sources normally used for space heating and cooling, and water heating. Three generic community components were designed, incorporating estimating techniques for determining their energy use for space heat- ing and cooling, and water heating, to test the dual-purpose technology in a variety of different communities types. The base-load power plant operates to continuously supply the thermal energy demand for any given community constructed from generic components, while exporting electric energy into the local utility grid. Energy and economic results are obtained from small urban communities without industrial steam users. Parameters of capital, materials, and fuel costs were varied over a range potentially applicable to the year 1980. Depa A SIMULATION MODEL FOR FEASIBILITY ANALYSIS OF DUAL-PURPOSE POWER PLANTS PROVIDING THERMAL ENERGY TO URBAN COMMUNITIES By David Harold Curtice A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Electrical Engineering and Systems Science 1977 The unreler is gratefully 8C friend indeed, E for their advice provided by the and Management 1 Development Adm: Finally, tl ACKNOWLEDGMENTS The unrelenting support and encouragement of Dr. Herman E. Koenig is gratefully acknowledged. Thanks also to Dr. Gerald L. Park, a friend indeed, and to Dr. Roberte. Schlueter and Dr. William E. Cooper for their advice and support. Financial support for this study was provided by the National Science Foundation through the project Design and Management Environmental Systems, and the Energy Research and Development Administration. Finally, this thesis is dedicated, with affection, to my family. ii Orapter II III IV l INTROI OVERVI 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 11.10 11.11 11.12 11.13 REVIE III. 1 111.2 111.3 Chapter II III IV TABLE OF CONTENTS INTRODUCTION . . . . . . OVERVIEW OF THE ENERGY 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9 11.10 11.11 11.12 11.13 REVIEW 111.1 111.2 111.3 011 . . . . . . . Coal. Natural Gas . . . Electric Power. . Our Energy Future C081 0 O O O O O 0 Nuclear Power . . Alternative Sources Summary . . Methodologies . . Energy Models . . Summary . THE DUAL-PURPOSE PLANT . IV.1 1V.2 1V.3 1V.4 1V.5 1V.6 1V.7 District Beating . Advantages of the Dual-Purpose Plant. 0 0 OF ENERGY MODELING. Oil Electricity Consumption Coal Consumption. . . . Natural Gas Consumption The Long-Term . . . . . Applications of Dual-Purpose Plant Turbine Systems. . . . . . . . . . Automatic Extraction . . . Energy of Steam and Electric Power Summary. . . . . . . . . . . . . ENERGY USE IN THE UNITED STATES. . . . . . . <<<fi<< OU§U¢NH Energy Statistics for Space Heating . . . . Degree-Day Method . . Insulation Standards. Water Heating . . . . Demand for Heated Water the iii United States 0 C O O Page 10 12 13 14 15 16 18 18 20 21 23 25 25 28 3O 33 36 37 38 40 42 44 47 48 55 57 59 63 66 7O 71 71 Chapter VII VIII IX <4 EH Vql.6 REIUER lFII. 1 \FII. 2 Chapter <<<< Hoax: 0 VI STEAM V1.1 V1.2 V1.3 V1.4 V1.5 V1.6 Steam Demand for Air Conditioning Steam Demand for Summary. . . . . DISTRIBUTION . Components . . . Pressure Drop. . Heat Losses. . . Water Heating . Air Installation Costs Steam Losses from an System . . . . . Summary. . . . . VII REFERENCE AREAS. . . . VII-1 VII.2 VII.3 VIII VIII.1 VIII.2 V111.3 VIII.4 VIII.5 VIII.6 VIII.7 VIII.8 V111.9 Conditioners. 0 Operat ing Physical Layout of the Reference Areas 0 O O O O O O O O I O O O 0 Steam Consumption in Reference Areas . . . . . Summary . . . . Methodology. . DESCRIPTION OF THE MODEL Model Boundaries Aggragation Level. Pressure Drop Program. Demand Component . . . Dual-Purpose Plant Component Cost Components. Validation . . Summary. . . . 1X CASES AND RESULTS. . . IX.1 1X.2 1X.3 IX.4 IX.5 IX.6 1X.7 .APPENDIX - . - ° REFERENCES . . . Case 1 - Multi-Family Dwellings. Case 2 - Single-Family Dwellings Case 3 - Commercial Area . Case 4 - Small Urban Community Steam Displaces Other Fuels. Generalizations. Summary. . . . . iv Page 75 76 79 82 84 84 84 85 88 94 96 97 97 104 106 108 108 111 112 113 123 129 136 146 150 151 152 157 159 163 165 167 177 178 182 Table 11 Petro 12 1985 Barre. L3 Estime Sand ( source i1 Major 12 Energ Use A: TOtal i3 End-U i4 Major L5 EStim "Stan: is Mean ‘ LansL i7 StEam in Bu is Perce Energ 19 Estim Build 510 Maxim Water ' Pital 5J1 le ater . Homes I12 EStim 113 Onth Norma I44 C0011 345 U11. tion May 1 516 Estit diti( 517 Tenn; n 31 A1 6‘2 ReCO] Esti] Table NM .0 NH MU! NH LflU‘U‘ U150.) 5.7 5.8 5.9 5.10 5.11 LIST OF TABLES Petroleum Consumption Across Prices. 1985 Coal Consumption at $13 Per Barrel Oil Prices. Estimated Resources of Shale Oil, Tar Sand Oil, and Coal Compared with Re- sources of Conventional Hydrocarbons . Major Uses of Energy in the Household. Energy Consumed, By Sector and End Use As a Percentage of National Total 1968 . End-Use Energy in the U.S. Major Steam Process Users. Estimated Energy Requirements for a "Standard House" . Mean Degree-Days in Michigan-East Lansing Station. Steam Consumption for Space Heating in Buildings . Percentage Distribution of Personal Energy-By Use-1968 . Estimated Hot Water Demand for Various Buildings. . Maximum Daily Requirements for Hot Water in Office Buildings and Hos- pitals . . . Maximum Daily Requirements of Hot Water in Apartments and Private Homes. . . . Estimated Hot Water Us Monthly and Annual Cooling Degree Days Normals. . . Rates. Cooling Load Check Figures . . Full-Load Operating Hours of Refrigera- tion Equipment Used for Summer Cooling May 15 to October 15 . Estimated Hours per Month for Air Con- ditioning. . Tonnage of Air Conditioning Required in Building for the Reference Areas. Recommended Thickness. Estimated Cost of Installed Buried Steam Lines. Page 17 19 22 58 60 61 62 66 68 69 72 73 73 74 74 77 78 80 81 82 89 92 eels L3 Estim. hi Meter | 7.1 Housir LZ Total LI InveS‘ 12 Base- per kl 901 9.2 L3 LA 15 Estimated Tunnel Cost. . . . . Meter Cost . . . . . . . . . . Housing Parameters . . . . . Total Annual Steam Demand. . . Investment in New Plants (5 Per kilowatt). Base-load Electric Generation Cost, Mills per kWh, 1975 dollars. . . . . Energy Cost in 1975 Dollars. $/MBTU ($IG jOUlE). s s o o s s s o o s s s o a Higher Operation and Maintenance Costs and the Cost of Steam. . . . . Percentage of Fuel Use by Residential sector 0 O O O I O O O O O O 0 Installed Cost of Unit and Cost of Steam . Installed Cost of Unit and Cost of Elec- triCityO O O O O O O O O O O I Increased Fuel Costs and the Cost of Producing Steam and Electricity. . . . vi 102 104 146 149 154 161 166 173 174 176 Figure L1 L1 L2 L3 L4 L5 L6 L7 L1 L2 L3 6-4 L5 L1 12 La 15 he hr Urban Turbir Back-1 Extra: Autom. Reducr Turbir Dual-1 Press: for v; Condu: Heat; Cost 1 Steam Distr Eight Tho S (17m ; TYpic Hulti Comme Physr Lugs Estim I”and 1 Estim ea Estim Famd]_ LIST OF FIGURES Figure Page urban Energy System Components . . . . . . . . . . . . . 4 Turbine Types. . . . . . . . . . . . . . . . . . . . . . 43 Back-pressure Turbine. . . . . . . . . . . . . . . . . . 46 Extraction TUrbine System. . . . . . . . . . . . . . . . 47 Automatic Extraction Turbine . . . . . . . . . . . . . . 48 Reduction in Thermal Rejection . . . . . . . . . . . . . 49 Turbine Expansion Curve. . . . . . . . . . . . . . . . . 51 Dual-purpose Turbine Heat Balance. . . . . . . . . . . . 52 b3~§t~bbb H O NGUwah-l p—o 6.1 Pressure Drop per 1,000 Feet of Pipe for Various Pipe Diameters . . . . . . . . . . . . . . . 86 6.2 Conductivity of Insulation.Materia1. . . . . . . . . . . 86 6.3 Heat Loss from a Single Buried Pipe. . . . . . . . . . . 87 6.4 Cost Factors of Insulation Material. . . . . . . . . . . 88 6.5 Steam Losses from Operating Steam Distribution sync-O O O C C C C O O O O O O O O I I O O 95 7.1 Eight Apartment Buildings per Block, Two Stories, Each Building 55' X 175' (17m X 53m). . . . . . . . . . . . . . . . . . . . . . . 93 7.2 Typical Residential Square Mile Multi-Familwaelling.................. 99 7.3 Commercial Area . . . . . . . . . . . . . . . . . . . . 101 7.4 Physical Layout of Single-Family Dwell- ings . . . . . . . . . . . . . . . . . . . . . . . . . . 103 7.5 Estimated Monthly Steam Demand Single- Family Dwellings . . . . . . . . . . . . . . . . . . . . 105 7.6 Estimated Monthly Steam Demand Commercial Area . . . . . . . . . . . . . . . . . . . . . . . . . . 105 7.7 Estimated Monthly Steam Demand Multi- Family Dwellings . . . . . . . . . . . . . . . . . . . . 106 8.1 General Structure of the Energy Flow System . . . . . . . . . . . . . . . . . . . . . . . . . 111 8.2 Flow Chart of Pressure Drop Program. . . . . . . .., , , 116 8.3 Flows and Lengths for Pressure-Drop Program . . . . . . . 118 8.4 Flow Chart of Pressure Drop and Heat Loss Program . . . . . . . . . . . . . . . . . . . . . . 121 8.5 Transport Radius . . . . . . . . . . . . . . . . . . . . 122 8.6 Main Steam Distribution - Multi-Fanily “8111088. 0 o a a a o o a a o s o a a a a a a a a q a o 124 vii SJ L8 L9 L10 All L12 113 Ll 12 13 11 Main cial Main Tamil 24-8: 24-Hc Cause Plant Heat Turbi Cost Plant Cost Extra Cost Flows Cost 0f To Progre Figure 8.7 8.8 9.3 A1 Main Steam Distribution - Commer- cial Area. . . . . . . . Main Steam Distribution - Single- Family Dwellings . . . . 24-Hour Electric Demand. 24- Hour Steam Demand . . . . . Causal Loop Model of the Dual- -Purpose Plant System . . . . . . . . . . Heat Balance Diagram - Extraction Turbine. . . . . . . . . . . . Cost Separation Model of Dual- -Purpose Plant. . . . . . . . . . . . . Cost of Producing Steam at Various Extraction Pressures . . Cost of Steam at Various Extraction Flows . . . . . . . . . . . Cost of Producing Steam Cost of Fuel. . . . . . . . . . . . . Program Structure . . . . . . . . . viii Page 125 126 128 128 130 134 137 169 171 175 179 During the variety of unan resource shorta. dividuals have 1 society aggravat the root cause t ponder, what son manifested as st. current environn centralized app] canservation of This study CHAPTER I INTRODUCTION During the past few years the United States has been host to a variety of unanticipated problems; environmental pollution, energy and resource shortages, and a stagnated economy. As a result, numerous in~ dividuals have questioned whether our highly centralizedeuuispecialized society aggravates an already complex situation and, on some cases, is the root cause of our problems. These students of all aspects of society ponder, what some believe, are more critical structural problems that are manifested as shortages of energy and raw materials. And in light of our current environmental, energy and economic problems, they advocate a de- centralized approach to resource utilization with a heavy emphasis on conservation of all our resources. This study, which focuses on efficient utilization of energy, was borne out of the centralized/decentralized debate. While it does not propose to resolve this debate by some analytic formulation; there are alternative ways to supply energy to society that fall within the scope of either a decentralized or centralized approach. And it is the objec- tive of this study to examine one alternative energy-producing/energy- using technology that is more decentralized in nature than the existing centralized technology currently employed by society. Dual-purpose power generation, supplying thermal energy and a sub- stantial amount of electricity, provides a technology to combine the attributes of t energy efficier locally placed of space consi overall efficie centers. Althc feasible system dustrial complf POVEI‘ plant ap; users to the pj Parks, and exar cuses on Small feaSibility of residential an Toward th spect to Tesid View of how we scenarios with is used to an; 111 reviews e 11‘ Presents p; of actiVity b1 CIQDCY of Eng attributes of both a decentralized approach to power generation and high energy efficiency. Decentralized in the sense that a greater number of locally placed dual-purpose power plants, many of smaller size because of space considerations, could generate electric power at higher . overall efficiencies instead of a few large plants located far from load centers. Although studies in the past have shown dual-purpose plants as feasible systems, their focus has been on large population areas or in- dustrial complexes, more or less an extension of the large centralized power plant approach. Instead of connecting a multitude of steam heat users to the plant, e.g., greenhouses, sewage treatment plants, industrial parks, and examining a grand urban/industrial community, this study fo- cuses on small urban communities to determine the technical and economic feasibility of dual-purpose power plants supplying thermal energy to residential and commercial complexes. Toward that end, Chapter 11 presents our energy situation with re— spect to residential/commercial and electric power. It provides an over- view of how we arrived at our current energy short-fall and future scenarios with respect to availability and use. Since a simulation model is used to analyze the feasibility of using dual-purpose plants,Chapter 111 reviews energy modeling with emphasis on methodology and scope. Chapter IV presents past applications of the dual-purpose technology, a description of activity by district heating companies, and a discussion of the effi- ciency of energy production comparing conventional and dual-purpose power plants. Chapter V examines the techniques used to estimate energy use in the residential and commercial sectors of society. Of particular importance is energy used for space heating, air conditioning, and water heating. The critical lin distribution SYS blocks or test c VII, which inclt the simulation 1 with operation 1 Chapter VI? of the simulati- analyzing compl sented in Chap: V37 to vary map feasibility of the test result ing in Small u the results. 1101’ those lar energy Sys steps required troduction is There are 8 Capone“ reqtl “Signs 1 and IF ea QICOmPODEn e C0011“ 0 and The critical link between the power plant and the community, the steam distribution system, is presented in Chapter VI. And then the building blocks or test cases for the feasibility study are presented in Chapter VII, which include three different communities that will be connected in the simulation model to derive economic parameters of cost associated with operation of the system. Chapter VIII brings together the preceding chapters in a description of the simulation model. All prior chapters provide the basic tools for analyzing complex problems not directly related to the test cases pre- sented in Chapter VII. The simulation model in Chapter VIII provides a way to vary many parameters of the problem and determine the economic feasibility of different community configurations. Chapter IX presents the test results of economic feasibility for dual-purpose plants operat- ing in small urban communities and generalizations that can be drawn from the results. For those readers desiring to do a feasibility analysis of a simi- lar energy system Figure 1.1 indicates schematically the sequence of steps required to use the simulation model. The remainder of this in- troduction is addressed to these readers. There are three basic components of the energy system, the community, steam transport and distribution, and the dual-purpose power plant. Each component requires analyzing a variety of information, making design de- cisions, and finally bringing together a finite set of alternatives for each component for use in the simulation model. Starting with the community,Chapter V details methods for estimating energy use by urban communities with reference to space heating and cooling, and water heating. These three energy uses represent a I II DI _ mewE—:_>.5E..£u .mo :31; ~ WN ammonia—Jae mam. mfiukcwn L menu “aucamcmuu was Snowmanmhumufi Efimmw will- Eula-0 m... -.us .21 tall-um- . Pip- i.‘ u s... m u out... p on g 1 In! new m ud-o!..aaa- :IIQ.J moi harm's ul I onxl vs.l - .m Inst-1... nu ‘ ..u u .I l m stun-usunsn «. s mucmcoaaoo Eoummm hwuocm anew: H.H snowflm .numoo hwuoso unuumuxo cu“: o>muwuom500 .xuwu«uuuuao new ensue no umou “nauouuuo zuaaununnom AD zuwuuuu Foam Lo unou V. needs new anoum acqosvoum «o unou .ucsmm ouomusmramav may we «seguussu Issue one Huuwuuooao mo munou asuumuu Summon soda new openness scanusu can cowuonuuxo.oo«mawnuco suns amused moumuocou aaoum osunusu “woman moaom voxum .aamauouml was non-H .aoxmu _ . .Hauamsu uo uaou .mucoaouaau tau seam can ousaaoum abouoaouv new asumsoa dawn numonassuu new conga-«nus; amoum now-achvomuoeu we sang w ounaaoua sssanus “mumsaasou on: sauna you concussed» mcuuslquau_ nouns unseen Issue was subStantial P3 can be made mo case, collecti should be used mnities not y energy needs a or warmest day for the type 0; restaurants, er large amounts 1 The Commur 0f the Steam dj reCrllirements mt Knowing the eng 59:5 these limi enmity, and the Chapter VIII (1 sures f0r the Pressure and f distribution 1 substantial part of the energy picture for urban communities. Estimates can be made more exact if the community is already established. In this case, collecting energy bills from potential users of the energy system should be used to develop time dependent demands for steam. For com- munities not y8t constructed, estimating techniques provide minimum steam energy needs and must be tempered with worst seasons case, i.e., coldest or warmest day and longest period. Consideration should also be made for the type of task for which steam is to be used. Some laundries, restaurants, etc., potentially located in the community, will require large amounts of steam, these possibilities must be considered. The community places one important constraint on the operation of the steam distribution system, and the power plant. Minimum pressure requirements must be maintained at all possible points of steam use. Knowing the energy tasks for which steam is to supply the energy source sets these limits for pressure drop in steam lines placed in the com- munity, and the pressure needed at the plant to maintain these pressures. Chapter VIII describes a program for finding pipe diameters, and pres- sures for the steam distribution and transport component given minimum pressure and flow rates. The coupling between the community and the distribution is strong, this program can be used to examine a variety of pipe diameters, and pressures. I have placed one more constraint on the design of the steam dis- tribution system not generally considered in the past. The Second Law of thermodynamics was used in the specification of the pressure demanded at the plant. Since extracting high-pressure steam from the turbine and throttling it through the steam transport and distribution system has the benefit of requiring smaller pipe diameters and thus lower 1 11 -. Lil 'Lnfij'i than: ., . installation cos: decrease first cc to the generator design the steam est reasonable pr the work produci largerpipe diane tribution and tr pressure steam t pressures. In t Sine comunities economically SU The PIESSU] steam tranSport quires the spam“ between Potentj needs, and flow 05 . L plpesa and . Wired to use and find the 1 $11 168 , 01. give [1&9de t0 S . at] installation costs, many systems in the past were designed in this way to decrease first costs. But as a result of this approach power delivered to the generator is reduced, increasing electricity costs. I chose to design the steam distribution and transport system to require the low- est reasonable pressure at the power plant and take full advantage of the work producing ability of high-pressure steam. This resulted in larger pipe diameters, on average, and higher costs for the steam dis- tribution and transport component, but had the advantage of using high— pressure steam to do shaft work instead of throttling steam to lower pressures. In the final analysis this may have made it difficult for some communities, e.g., communities of single-family dwellings, to be economically supplied with steam. The pressure-drop program for determining pipe diameters in the steam transport and distribution system, detailed in Chapter VIII, re- quires the spatial layout 0f the community. This means that distance between potential steam users must be known along with minimum-pressure needs, and flow rates. Inside pipe diameters, minimum pressure, length of pipes, and a table of average steam densities are all that is re- quired to use the program. The designer can then chose pipe diameters and find the initial pressure required at the plant to maintain pres- sures, or given an initial pressure at the plant find the pipe diameters needed to satisfy minimum pressures in the community. Simple modifica- tion to the program to eliminate flows to steam users and the program can be used to specify the transport steam lines. To determine the final time dependent steam demand to be supplied from the power plant, it is necessary to compute steam losses from the steam transport and distribution system during full-year operation. chapter VI show drop program to which is drawnf panies and is u With the t required at the power generatio describes the 5 cost of steam a dependent upon Single or multi Single unit p13 native. The model the capital cos not subsidize e Plant cage, an costs t° i“Sure trical functior Capabilities f1 Chapter VI shows the procedure for using results from the pressure drop program to determine steam losses. Two methods are shown, one of which is drawnfrom the operating experiences of District Heating com- panies and is used in this study. With the total time dependent demand for steam, and the pressure required at the plant now determined, the feasibility of dual-purpose power generation for a given design can be determined. Chapter VIII describes the simulation model in detail. From it the final break-even cost of steam and electricity can be determined. These costs are dependent upon plant size, cost of fuel, and whether the plant is a single or multiple unit. The analysis in this study considers mainly single unit plants, as it generally represents the more costly alter- native. The model separates costs of producing steam and electricity and the capital costs associated with each to insure that steam users do not subsidize electricity users and vice versa. In the single unit plant case, an extra steam generator is added to the steam function costs to insure adequate steam supply during maintenance of the elec- trical function of the plant, along with additional water treatment capabilities for water returned to the plant from the community. Also, the steam function of the plant must pay for modifications to the tur- bine and controls to facilitate extraction. The cost of producing steam for any given plant size is a function of extraction pressure at the plant, flow rates, and fuel costs. Chap— ter VIII details the thermodynamic variables that must be known from turbine size and how to use them to determine the final cost of produc» ing steam and electricity. Varying plant size, and the cost of fuel, :he model C3: and steam tré Capital by utilities. direct, conti tal costs of and maintenan given the anm design of the competitive wj of a Plant cor. the model can be used to examine optimal plant size for a given community, and steam transport and distribution system. Capital costs are determined by use of standard economic analysis used by utilities. The steam function of the plant incorporates direct, in- direct, contingency, and an escalation factor to determine the total capi- tal costs of the steam system. An annual fixed charge and an operation and maintenance cost are used to compute to break-even cost of steam, given the annual output of steam. Economic feasibility for any given design of the energy system is then determined by whether or not steam is competitive with other fuels and if electricity costs are representative of a plant connected into the grid. Over the series of cris economic decli Solution to tr; inposing P0111. lating the fec Clear that the the economic 5 us is not a s. fine-1’8? p; System, the p driVes the ac Production Sy increased “Se that energy 1 systems; the the availab 11 System, where CHAPTER II OVERVIEW OF THE ENERGY PROBLEM Over the last ten years the United States has been confronted by a series of crises; environmental pollution, the shortage of energy, and economic decline characterized by high unemployment and inflation. The solution to these problems is usually seen as a set of separate policies; imposing pollution controls, finding new energy resources, and manipu- lating the federal budget, taxes and interest rates. It is increasingly clear that the problems with the ecosystem, the production system, and the economic system are completely interdependent. And what confronts us is not a separate set of crises, but a faulty design of modern society. Energy plays a decisive role in the interactions between the eco- system, the production system, and the economic system. Solar energy drives the ecosystem, and energy derived from fossil-fuels drives the production system. The rate of economic activity is intensified by the increased use of energy to produce greater output. Moreover, the fact that energy is in short supply has repercussions for all three of these systems; the high yield we enjoy from the ecosystem is dependent upon the availability of energy for machines and fertilizer, the production system, where machines have tended to replace human energy, is now al- most totally dependent upon energy to maintain high levels of output. And the intensified uses of energy in the ecosystem, and the production system, are associated with the economic difficulties of unemployment and inflation. What is len. It is 17 the problem a The purpose b the following can be evalua 11.1 Oil Up until of foreign oi: in the world. Here growing. Floration and availability 0 comPanies Cut slightly after increasing at fiddle of 1950 oil comPanies a PeriOd of pc Profitability permit in 1 [1mm now 10 What is offered in this chapter is an overview of the energy prob- lem. It is not exhaustive by any means, but provides a description of the problem as it relates to oil, coal, natural gas, and electric energy. The purpose being,to place in the mind of the reader a context in which the following analysis of an alternative energy producing/using system can be evaluated. 11.1 Oil Up until the 1960's, the United States was essentially independent of foreign oil, producing and consuming more oil than any other country in the world. Its domestic supplies were plentiful and proven reserves were growing. However, production from older fields peaked and new ex- ploration and development of domestic oil diminished because of the easy availability of less expensive 011 found in foreign countries. Oil companies cut back on exploration efforts as the price of oil declined slightly after 1962, and in light of the fact that oil prices were not increasing at the rate of 11 percent per year, like they did in the middle of 1950 (increasing only 4 percent between 1957 and 1962). The oil companies decided to reduce domestic exploratory efforts, following a period of poor economic returns on domestic oil, and follow the higher profitability of foreign operations. Import dependency grew from 18 percent in 1960 to about 43 percent in 1976. Direct imports from OPEC nations now constitute about two-thirds of all oil imports with Nigeria, Canada, Venezuela, Saudi Arabia, and Indonesia supplying most of our immorted oil (FHA, 1976). These rising imports increased the U.S. balance of payments from $3 billion for foreign oil in 1970 to about $27 billion ($125 per capita) in 1975. Increased oil prices, since the Arab oil embargo of 1973, affected all P9 1973 (m, 1976 Higher cru oil. The numbe about 37,000 in in 1973 to over creased drillin because of the dropping from o barrels a day 1' a day from the "ill still only Cmlslfinptic by 4 Percent 1p Embargo, demand a day Over wha out, my hav| to belieVe tha 111% factOr. covemmen Energy Policy oil‘depletion Com ll affected all petroleum products with gasoline increasing 50 percent since 1973 (PEA, 1976). Higher crude oil prices have now stimulated exploration for domestic oil. The number of oil wells drilled has risen from 26,000 in 1973 to about 37,000 in 1975 (FEA, 1976). More drilling rigs are in use, 1,200 in 1973 to over 1,600 rigs in 1975 (FEA, 1976). However, despite in- creased drilling activity the domestic oil production continued to decline because of the several years time lag between exploration and production. dropping from over 9 million barrels a day in 1973 to less than 8 million barrels a day in 1975. Even with the addition of about 2 million barrels a day from the Trans-Alaskan Pipeline in 1977, domestic oil production will still only be near the 1970's levels. Consumption of petroleum products since the 1973 oil embargo fell by 4 percent in 1974 and an additional 2.5 percent in 1975. Without the embargo, demand would have pushed oil consumption to 3 million barrels a day over what it was in 1975 (PEA, 1976). While lower economic ac- tivity may have contributed to the slowing of demand there is good reason to believe that consumer response to higher prices was a major contribut- ing factor. Governmental responses to the oil situation were passage of the Energy Policy and Conservation Act (EPCA) and partial removal of the oil-depletion allowance. The EPCA law provides for a statutory domestic composite oil price of $7.66 per barrel that is escalated by a GNP de- flator and other incentives to increase production. The price control authorities convert from mandatory to standby after 40 months. If price controls expire in 40 months and world oil prices are $13 per barrel, the conservation measures in the EPCA would reduce import needs to 3.4 million bar through 1985, 1' other hand, nat these alternat: barrels a day, ‘ 11.2 Coal Essential the last five (613 billion P (FHA. 1976). Over the trial and res: for steam Pro 835. removal Ported Price Power have a] 1960's and ea 12 3.4 million barrels a day by 1985. If price controls remain in effect through 1985, imports would be 6.5 million barrels a day. If, on the other hand, natural gas price regulations also continued, imports under these alternative oil price control cases would be 6.2 and 8.3 million barrels a day,respectively (FEA, 1976). 11.2 Coal Essentially, coal production has remained at a constant level for the last five years. Production in 1970 was about 603 million tons (613 billion kg) and about 640 million tons (650 billion kg) in 1975 (FEA, 1976). Over the past 20 years coal consumption has declined in the indus- trial and residential sectors while the use of coal as a primary fuel for steam production has increased. The regulated price of interstate gas, removal of import controls on residual fuel oil and its cheap im- ported price (until the 1973 embargo), and the development of nuclear power have all combined to limit the growth of coal use. In the late 1960's and early 1970's, state and local air pollution regulations dis- couraged power companies from burning coal. Reliability and costs of stack gas scrubbers, legislative changes to the Clear Air Act, surface mining reclamation laws and uncertainty about environmental issues are still affecting the growth in coal use. While oil prices rose dramatically, coal prices on long-term con- tracts have been relatively stable. Some coal prices rose rapidly to $32 per ton ($35 per 1000 kg) in the latter part of 1974 because of a pending coal strike, but have declined since 1975. Contract prices of coal have risen steadily since the end of 1973 reaching $.75 per million BTU's ($.71 per giga joule) in 1975 (FEA, 1976). II.3 Natural Approximat natural gas W81 Canada are impc than 5 percent Because 01 compared to otl after the 1960 22.6 trillion r Captly in 1974' After 196 per Year than EXCEpt for the in Alaska in 1 marketed ProdL not add to the tveen wells 81 Low regu EXPIOratiOD f for natural g priCES . As a at an average 1000 Cubic m interstate p MEter) (PEA bee n the is found S 13 11.3 Natural Gas Approximately 21 trillion cubic feet (595 billion cubic meters) of natural gas were used in 1974. Although pipeline line imports from Canada are important in the Pacific Northwest, they account for less than 5 percent of annual consumption. Because of its clean burning properties and low regulated price compared to other fuels, demand for natural gas increased dramatically after the 1960's. Marketed natural gas production peaked in 1973 at 22.6 trillion cubic feet (640 billion cubic meters) and dropped signifi» cantly in 1974. After 1968, the United States has been consuming more natural gas per year than producers have been able to find in the form of new wells. Except for the 26 trillion cubic feet (736 billion cubic meters) found in Alaska in 1970, annual additions to reserves have failed to equal marketed production over the last seven years. The Alaskan find will not add to these reserves until the 1980's due to the missing link be- tween wells and the lower 48 states. Low regulated prices have encouraged consumption and discouraged exploration for new gas for the interstate market. Intrastate prices for natural gas have risen much faster than the regulated interstate prices. As a result, producers have been selling gas under new contracts at an average $1.00 to $1.50 per thousand cubic feet ($.35 to .53 per 1000 cubic meters) in the intrastate market compared to the regulated interstate price of $.52 per thousand cubic feet ($.18 per thousand cubic meter) (PEA, 1976). The main result of the regulated lower price has been the development and sale of natural gas in the state where it is found. Since 1970, 90 percent of all new additions to reserves have been sold to it California, Ne‘ production in I In 1974 nearly Industrial relt are some of th llJo Electri Higher fu operating cost oil prices and has shifted t trim? have future Capacit We? envirmm1E the utility 1r gIWth of elE( In the 1- about 7 Perce additions int nuclear rate electricity f (YEA: 1976). 183801] for t} The fin(’ affected by and a harden 1 Over Capaci 14 been sold to intrastate markets. Six states, Texas, Louisiana, Oklahoma, California, New Mexico and Kansas accounted for 93 percent of domestic production in 1974 - Texas and Louisiana alone provided for 73 percent. In 1974 nearly 50 percent of domestic consumption was in these six states. Industrial relocation and the use by electric utilities in these states are some of the reasons for this large percentage. 11.4 Electric Power Higher fuel costs, with already escalating plant construction and operating costs, have forced higher rates for electricity. With today's oil prices and the shortage of natural gas, the economics of new plants has shifted to coal and maybe nuclear power. The higher rates for elec- tricity have also reduced demand and this in turn is likely to reduce future capacity needs. These effects, along with the continuing debate over environmental siting and safety issues, and financial problems in the utility industry have introduced significant uncertainties into the growth of electric power. In the recent past, electric power demand grew at an annual rate of about 7 percent (as high as 10 percent in some areas). Projected plant additions into the early 1980's were based on a pre-embargo, pre-anti- nuclear rate of demand growth. In 1974, the growth in the demand for electricity fell to zero and only increased about 2 percent in 1975 (FEA, 1976). The economic slowdown and higher rates are given as the reason for the low growth. The financial situation of electric utilities has been dramtically affected by higher fuel costs, which necessitated large rate increases and a hardened response to further rate adjustments. At the same time, lower capacity utilization, longer lag times for licensing and construction. 5 required even p plants (many a before the embr electric utili of money cause The fuels. Nuclear's shar in 1973 to abo PUClear power 13’8“ capital Consequently, cameEllationg, of planned nuc accounted for the dr0p in e] capaCity 18 DC cent (“1A. 19'} 15 construction, and high inflation associated with new plant construction required even greater rate increases if utilities were to finance new plants (many already in construction as a result of high growth rates before the embargo). When rates did not increase fast enough, the electric utilities ability to raise equity was impaired and the shortage of money caused cancellation or deferral of many new plants. The fuels used to generate electricity have shifted in recent years. Nuclear's share of electricity production grew sharply from 4.5 percent in 1973 to about 8.6 percent estimated for 1975 (FEA, 1976). Although nuclear power has the lowest variable operating costs, they require larger capital investment and the longest construction to operation time. Consequently, nuclear power has been the most heavily affected by plant cancellations and deferrals. Since June 1974, over 100,000 megawatts of planned nuclear capacity have been cancelled or postponed. They accounted for almost 70 percent of planned additions. Nevertheless, with the drop in electricity growth and the additions of new plants, reserve capacity is now 34 percent, compared with a traditional level of 20 per- cent (FEA, 1976). This idle capacity is expensive for consumers, since the carrying and overhead costs must be paid whether or not the equip- ment is used. 11.5 Our Energy Future- 011 It seems clear that little can be done between now and the 1980's to alter the supply and demand relationships between OPEC and consuming nations enough to weaken the cartels' exclusive control over world oil prices. And since any analysis of the future domestic oil outlook must be influenced by world oil prices, the possibility of lower oil prices must start with the OPEC nations. Political cope with highe forecasting the FEA projections rel for the nea rand should inc 1974 to 98.9 qt Petroleum particularly er Per barrel, in tricky Wherea to generate 81 Prices bECaUSQ I | than from an CI The indusl SitiVe to Prifil where alternatl Portaticm secdj may See lower-ll efficient aut: function of electric gene PricEs . II.6 Electr . Electri SOUTQES in t 16 Political factors and consumer nation's initiation of programs to cope with higher prices, and excessive dependence on foreign oil make forecasting the future very uncertain. But most estimates follow the FEA projections that prices will be in the range of $8 to $16 per bar- rel for the near future. If current prices continue, total energy de- mand should increase from 72.9 quadrillion BTU's (77 x 1018 joules) in 1974 to 98.9 quadrillion BTU's (104 x 1018 joules) in 1985 (PEA, 1976). Petroleum demand is naturally sensitive to oil prices. This is particularly evident in the electric power generation sector. At $8 per barrel, in 1985, more oil is projected to be used to generate elec- tricity whereas at $13 per barrel, almost 70 percent less oil is used to generate electricity (PEA, 1976). Coal replaces oil at higher import prices because electricity from a new baseload coal plant is cheaper than from an oil-fired plant if oil is above $9 per barrel (PEA, 1976). The industrial demand for petroleum tends to be relatively insen- sitive to price since about 30 percent of the demand is for feedstocks where alternative fuels cannot be physically substituted. The trans- portation sector, accounting for more than half of petroleum demand, may see lowered demand as a result of higher gasoline prices and more efficient automobiles. Different projections for petroleum use as a function of price are given in Table 2.1, and it appears that only the electric generation sector can really respond quickly to changes in oil prices. 11.6 Electricity Consumption Electricity has grown about twice as fast as the total of all energy sources in the last twenty years, and will probably continue to do so, Sector Household / c omr. Industrial Transportation Electrical gen TOTAL Reference: 3% REport no. FE although at It will grow at world Oil Pri et a1 ’ thEy h pEI'Cth 1321‘ The larg affect Coal. Shortages and Of eleCtricit and sirIce nu lead”: 1mes f coal become 17 TABLE 2 . 1 Petroleum Consumption Across Prices (million barrels per day) 1985 demand 1985 demand 1974 @ $8/barrel @ $13/barrel Sector Usage (growth rate) (growth rate) Household/commercial 3.4 4.8 (4.6) 4.0 (2.8) Industrial 3.1 4.6 (3.8) 4.2 (3.1) Transportation 8.7 12.4 (3.3) 11.5 (2.1) Electrical generation 1.5 3.8 (8.3) 1.2 (-2.3) TOTAL 16.6 25.6 (4.0) 20.7 (2.0) Reference: National Energy Outlook, 1976. Federal Energy Administration. Report no.7 FEA-N-75/7l3. U.S. Government Printing Office, page 17. although at lower rates. The PEA estimates that the use of electricity will grow at a rate of 5.4 percent per year from 1974 to 1985 if present world oil prices continue. A higher projection is estimated by Pelley et a1 , they project the growth of electricity demand through 1990 at 6 percent per annum (Pelley etal, 1976). The large uncertainties with respect to the demand for electricity affect coal, nuclear, oil and gas consumption. But with natural gas shortages and higher petroleum prices, the reliability and availability of electricity make it a premium energy source. Electricity tends to displace direct use of oil and natural gas in households and industry and since nuclear power is constrained by great uncertainties and long lead-times for new plants, the next cheapest source of electric power - coal, becomes the fuel for swing capacity. For each 1 percent change in electriciti jected to char coal plants ca A strong less than 5 pt greater use 0 cent per year can be expec t. 11.7 Coal Co The bulk to 1985 perio. 2.2). The ac dePend Upon e: surface minim; caPital, othEr s COal. OppOrt litrited by t and the highe fUEls frOm C 11.8 Natura 18 in electricity growth rate from 1974 to 1985, coal consumption is pro- jected to change by 150 million tons (136 billion kg) in 1985, provided coal plants can be completed in time (PEA, 1976). A strong conservation effort could reduce electricity growth to less than 5 percent annually. Alternatively, if a strong shift towards greater use of electricity occurs, demand could grow at almost 6.5 per- cent per year (PEA, 1976). Under the latter scenario, coal production can be expected to increase. 11.7 Coal Consumption The bulk of the projected increase for coal consumption in the 1974 to 1985 period will occur in the electric generatitnt sector (see Table 2.2). The actual coal consumption in the electric generation sector will depend upon environmental standards, availability of coal transportation, surface mining regulations, and the ability of the utilities to obtain capital. Other sectorsmare anticipated to have little growth potential for coal. Opportunities for coal consumption by the industrial sector are limited by the cost of complying with air pollution control requirements and the higher cost of handling smaller quantities of coal. Synthetic fuels from coal are not yet competitive at $13 per barrel for oil and are not expected to develop until the late 1980's. (PEA, 1976) 11.8 Natural Gas Consumption Natural gas usage is projected to change only slightly over the next ten years, assuming deregulation of new natural gas prices. In 1974, about 21 trillion cubic feet (595 billion cubic meters) were pro- ciuced and in 1985 this figure is projected to be 23.4 trillion cubic feet (665 billion cubic meters) (PEA, 1976). 1985 Sector Nectric Util household / cor: Industrial Metallurgical Synthetics ExPorts 19 TABLE 2.2 1985 Coal Consumption At $13 Per Barrel Oil Prices (million tons - 109 kilograms) growth rate Sector 1974 1985 (percent/year) Electric Utilities 390-354 715-649 5.7 Household/commercial 11-10 5-4.5 -6.9 Industrial 94-85 151-137 4.4 Metallurgical 63-57 73-66 1.3 Synthetics 0 16-15 - Exports 60-54 80—73 3efl 618-561 1040-943 4.8 Reference: National Energy Outlook, 1976. Federal Energy Adminstration. Report no. FEA-N-75/713. U. S. Government Printing Office, page 21. Natural gas use is constrained by the very limited availability of inexpensive supply. Much of the more readily accessible domestic supply is already dwindling before imports, synthetic fuels, and Alaskan gas can have much of an impact on resources. The national trend in the past few years has been a growth in gas consumption in the industrial sector and reduced use in the residential sector. The residential consumption declined in 1972-1975 because gas deliveries to the interstate market declined, while intrastate markets, where a growing industrial market is located in the six producing states, has increased. With industrial users of natural gas in the interstate market on the lowest priority,many industries have voluntarily switched from natural g a reliable sup" The effec demand as gas (EA, 1976). constant (in r keep the growt low. Project: dustrial sectr sector, contir 11'9 The Lon A panel of the Nation, of potefltiall li(Illids) in t shelves, Th1 United States 883 liquids c meters) of ga “tractable mated by Hub 20 from natural gas to electricity, coal, and in some cases oil to assure a reliable supply of energy. The effects of higher deregulated natural gas prices will reduce demand as gas prices are expected to increase more than other fuels (PEA, 1976). Since electricity prices are expected to remain relatively constant (in real terms), increasing natural gas prices will probably keep the growth of gas use in the residential/commercial sector very low. Projections to 1985 predict gas consumption will grow in the in- dustrial sector'and continue to decline in the residential/commercial sector, continuing the behavior of the last ten years (PEA, 1976). 11.9 The Long-Term A panel of the Committee on Mineral Resources and the Environment of the National Academy of Sciences has analyzed the numerous estimates of potentially extractable hydrocarbons (oil, natural gas, natural gas liquids) in the United States, including Alaska and the continental shelves. This panel concludes that the hydrocarbon resource base of the United States approximates 113 billion barrels of crude oil and natural gas liquids combined and 530 trillion cubic feet (15 trillion cubic meters) of gas (NAS, 1975). Although the estimate for the ultimate extractable quantity of crude oil is somewhat greater than that esti— mated by Hubbert, it is nevertheless well within reasonable bounds (Hubbert, 1971) . Something like the equivalent of 500 billion barrels of petroleum (oil, natural gas and natural gas liquid eqivalents) appears to be ultimately extractable, of this, somewhat over 40 percent has already been removed. An appreciation of the significance of these numbers is essential for understanding of the difficult energy situation now confronting the United Sta against the ul Alaskan discm continue their sill also con! tion of the AI completion of not likely to years ve mus utilizing gre like coal, an m and other latter decisi depend for on 11.10 Coal One of 1 Content, an d is “Early o POlluri sulfur an d n converting c 21 the United States. We are clearly, by anybody’s estimate, pushing against the upper limit of our domestic extractable hydrocarbon resources. Alaskan discoveries can be only temporary as reserves are destined to continmetheirdownward path in the long run. Production of hydrocarbons will also continue downward after a brief upsurge following the comple- tion of the Alaska pipeline. There will be another jump upward upon completion of several gas lines about 1979. Since our energy demands are not likely to decrease to any appreciable degree during the next few years we must compensate for the decreased domestic production either by utilizing greater quantitiesof other energy resources in the United States, like coal, and solar energy, or by importing greater quantities of crude oil and other hydrocarbons from other countries. Suffering by this latter decision the power of the oil cartel and others upon whom we will depend for our energy. 11.10 Coal One of the principal drawbacks to the use of coal is its sulfur content, and this is particularly troublesome for the future since coal is clearly our most abundant physical energy resource (see Table 2.3). Pollution from the burning of coal, particulate matter, oxides of sulfur and nitrogen oxides are of great concern. Methods now exist for converting coal to combustible gas, to synthetic hydrocarbon liquids or to methanol (methyl alcohol). Whether or not these technologies can pro- duce an inexpensive product from coal remains an unanswered question. Of course, coal can also be burned directly to generate electricity, but unless the fuel is relatively free of sulfur, special provision must be made to remove the sulfur dioxide formed during combustion. In addition, the partuclate matter formed by the ash must be removed to wcwamkzfisvw mcowwwwm .ch we mmmhhtm econ—CalamzcelmccvfivaC u: mTtLLcm wmwo3 mmumum nmuficb mconthOhfi%: H6CCHUCU>GOU MO EUUHDOWQM Sufi} UGMWQEOU H500 D55 .HuC UCQW hfifi .HHO QHQSW N0 GPUNUOEGZ UfiufiEflumm an 0N MHuhzcm ozu mam moousomom HmuoCHz .mmma .moousomom Hounumz co scammwaaou .mooaowom mo maovmo< Hmcowumz .oofiwmo masocfium ucoecuo>ou .oww .mmm .woum emuquqdaumldmmocfiz moumum woman: .mmma .»o>u=m Hmowwoaoou .m.= .o.a .couwaanmmz .oN omen .mwauouwamu .OuH4 oamm ..ocH .msmw>om Hmsca< «quocm mo 3oa>ox Hmacc< .oHSusm woo ca mwuocm .emaa momfiuum: .caoum "monopomom oom.mm owm.m 000.5 oon.a oea own e on ooo.nq 090.cqm 0mm.m cow.m~ nae ooo.m omm ooo.~ ome coo.m we con Aoapuoav Hmoo mc0u Amcofiaafinv Aowuuosv Hmoo mcou AchaHHHnV ucoaw>wsoo meowaaam ago we maoupmm ucoam>a3oo mcowaaam Has «0 «Howumm mHuoz moumum woman: mcopumoouv>m HmCOfiuao>coo mo moouaomom Suez noummaou Hmoo mam .Hwo vsmm any .Hmo mamnm mo moousomom voumawumm m.~ m4muomou ouoamaoocH Hfio mango mo mo>uomou ~vouo>oomwvca Hao manna mo mo>uomou HmoamwuaovH mconumoouvzm Hmcoauco>aou prevent pollutix since scrubbers is capable of h electric plants long term. One possib in the fact the slowly with the of the combust: the atmosphere 0f the concent earth's surfac mechanisms, po This Sing Should be m0“. cation of Eros Stantially tr “0 matt declining. because of ‘ of prohib i t versim’ 01 all threQ. we will be very lat ge 11.11 NuQ Any 23 prevent pollution of the atmosphere. These problems appear to be solvable since scrubbers now collect over 90 percent and the natural environment is capable of handling a given amount of gases given off by coal-fired electric plants. Thus, coal appears to be a possible alternative for the long term. One possible danger associated with the expanded use of coal lies in the fact that the carbon dioxide in the atmosphere equilibrates very slowly with the bicarbonate of the deep oceans. Apparently,as a result of the combustion of fossil fuels, the carbon dioxide concentration in the atmosphere has increased. Theoretical studies indicate that a doubling of the concentration could effect an increase of the temperature near the earth's surface by about 60F (2°C). Such a change could trigger other mechanisms, possibly leading to irreversible climatic effects. This single aspect of greatly increased consumption of fossil fuels should be monitored very closely. Any clear physical or theoretical indi- cation of emerging adverse effects may make it advisable to lessen sub- stantially the global rate of fossil fuels consumption. No matter how you analyze the problem, fossil fuel use will start declining. It is too early to say whether this change will come about because of decreasing availability of fossil fuels in the ground, because of prohibitively high costs (both monetary and energy) of mining and con- version, or because of adverse environmental effects or a combination of all three. But even before we reach that time, it seems probable that we will be using solar energy or nuclear power, or perhaps both, on a very large scale. II.ll Nuclear Power Any casual student of the nuclear power issue will quickly recognize that not one of from attack for Estimates the ability of situation. So yellw cake, U sion of nuclea only about 1 1”, utilized, the Quantities of kilogram) or grams) (Brown million kiIOg per kilogram)' technologies total Energy limit“ by t} BreEder Administrati‘ isotope of u available En SOlVed if b There are p aCtlve by are problem 3 S 24 that not one of the processes involved in the nuclear fuel cycle is free from attack for one reason or another. Estimates of the resource availability for nuclear power question the ability of nuclear power to have a real impact on the total energy situation. Some more pessimistic forecasts see the possiblity that yellow cake, U308, could be seriously limited by the year 1980 if expan- sion of nuclear electric power proceeds as planned (Lieberman, 1976). As only about 1 percent of the total energy available in the uranium is utilized, the quantities of uranium needed for nuclear power are large. Quantities of uranium that can be obtained for $14 per pound ($30 per kilogram) or less, are no more than one million tons (907 million kilo- grams) (Brown, 1976). Perhaps, an additional five million tons (4536 million kilograms) could be obtained at costs under $45 per pound ($90 per kilogram) (ITC, 1971). It is likely that for as long as nuclear technologies are employed that make use of such a small fraction of the total energy available, the spread of nuclear power will be basically limited by the cost of uranium. Breeder reactors, advocated by the Energy Research and Development Administration as the long-term solution to limited uranium - 235 resources, will be able to feed on plutonium derived from the most common isotope of uranium (uranium 238), releasing as much as 60 percent of its available energy. However, there are numerous problems that must be solved if breeder reactors are to play a role in energy production. There are problems of waste disposal, since huge quantities of radio- active by-products will be generated. Last, but by no means least, there are problems of preventing plutonium from falling into the hands of un- scrupulous persons. Not much plutonium is needed to make a bomb of substantial explosive force. 11.12 Alterna Without a social and tec radiation, cos "what ought t production haw solar heating ideas to use solve the enei The pote1 effective Uti intensity, Va location for Pects for “H ful. 25 11.12 Alternative Sources Without a doubt the nuclear/faster-breeder power issue is a complex social and technical problem that has as much to do with the problems of radiation, costs, and capital, etc., as it does with the question of "what ought to be." The uncertainties associated with nuclear power production have spurred new interest in solar energy. Wind generators, solar heating and cooling, photovoltaics and an endless stream of new ideas to use renewable resources of energy have been proposed to help solve the energy crisis. The potential supply of solar energy is practically unlimited. Its effective utilization suffers from the fact that it is of relatively low intensity, variable in its availability, and not available in any one location for the entire day. In spite of these difficulties, the pros- pects for the use of solar energy on a large scale seem reasonably hope- ful. 11.13 Summary Oil and natural gas are clearly going out of thelong-term energy picture, Electricity consumption is expected to continue to grow with coal-fired and nuclear-fired plants being built to meet demand based on a complex set of environmental, safety and economic issues. The nuclear power impact is very difficult to measure at this time. After so many years of debate, nuclear power is stillproblematic. The impact of solar energy is not likely to come about until after the 1980's. Even then, its replacement of other fuels will be slow to develop. The real hope for solar energy is in the very long term. united States has coal reserves amounting to more than three times the energy contained in the Middle East oil. This coal reserve is approximately 9 Yet over the 12 use of coal for and natural gas energy which is ports have made The avail. crease the exp 9.6 million ba barrels a day, 1960's and ear straints on th By1975, chm “1 made Up th the Shock of t charged by 0le SW) for impel The dem. rate of 3.6 the Unite d S of energy. of twice the means that J 26 approximately 90 percent of all proven United States energy reserves. Yet over the last 75 years, the United States has shifted away from the use of coal for 90 percent of its energy needs to dependence upon oil and natural gas for 75 percent of its energy. Thus, the nation now uses energy which is least abundant in the United States and for which im- ports have made us almost totally dependent upon the OPEC nations. The availability of the expensive Middle East oil served to de- crease the exploration and production of domestic oil, which peaked at 9.6 million barrels a day in 1970 and now stands at only 8.2 million barrels a day. Meanwhile demand continued to grow at 4.6 percent in the 1960's and early 1970's in response to low prices, environmental con- straints on the use of coal, and the growing dependence on automobiles. By 1975, thirty-seven percent or 6 million barrels a day of imported oil made up the difference between demand, and domestic supply. After the shock of the Arab oil embargo, and the increased price for oil charged by OPEC, the United States paid about $27 billion ($125 per per- son) for imported oil in 1975 - up from $3 billion in 1970. The demand for all forms of energy grew in the United States at a rate of 3.6 percent in the 20 years before the 1973 oil embargo. By 1975 the United States used about 73 quadrillion BTU's (77 quintrillion joules) of energy. During this period, electricity grew at an average annual rate of twice the rate of all energy demand (about 7 percent per year). This means that if we continue to demand energy at a rate of 2.8 percent, we will use 98.9 quadrillion BTU's (104.2 quintrillion joules) in 1985. Lowering the historical growth rate from 3.6 percent to 2.8 percent can be accomplished because the residential/commercial and transporta- tion sectors can make adjustments to higher energy prices.. An active I. conservation e it would take 30 re . In the m gas prices co Domestic oil by1985. All produce and a Electric mice the ex are allowed ; Power is in strainted by The “Se of 1 Phased Out this "Ould have to be. environmeI Cens Year 19 85 27 conservation effort could cut this rate to 2.2 percent through 1985, but it would take a different policy at the Federal level to reduce it much more. In the near future, between now and 1985, deregulation of oil and gas prices could reduce imports to about 5.9 million barrels a day. Domestic oil production could increase to 12.3 million barrels a day by 1985. All of which depends upon the amount of oil we discover and produce and whether or not prices are high enough to justify production. Electricity could continuetngrow at a rate of 5.4 percent or about twice the expected growth of all energy if coal and nuclear power plants are allowed free access to supply demand. But the future of nuclear power is in doubt and the future growth of coal-fired plants is con- strainted by environmental standard, and the availability of capital. The use of natural gas and oil-fired power plants will probably be phased out due to higher fuel costs. Coal can take their place, but this would mean about 700 million tons (635 billion kilograms) would have to be mined in 1985. Whether or not this is possible depends upon environmental as well as Federal decisions. Conservation, although having no real impact on energy use by the year 1985, in the long run, is man's best policy for all resource utili- zation. Switching from fossil and nuclear fuels in the future may make the axiom, "less is more" an every day reality. But, between today and the not-so—distant future, the United States will have to exploit re- sources while moving in the direction of making better use of the abun- dant resources available. Using these abundant resources so as to produce the maximum amount of work possible while recovering any useful by-products produced to lessen the demand for energy and resources. In the pa energy models l such a vital p has enjoyed a in research am fate 0f man, sets 0f techn Energy 8} lytical me tho economics . 0P of machem'auc and network a international short reVEiu selected ener The face usually eVok, of Waugh elm; Pal-so“. CHAPTER III REVIEW OF ENERGY MODELING In the past, only government regulatory agencies developed and used energy modelstx>any great extent. But since energy is now recognized as such a vital part of the economic well-being of society, energy modeling has enjoyed a great boom in interest. For P011CY makers, people involved :haresearch and analysis, and the many prophets trying to forecasttthe fate of man, energy modeling provides ways to construct complex integrated sets of technical and economic information. Energy system models have been formulated using theoretical, ana- lytical methods and data from a variety of disciplines. Engineering, economics, operations research, management science,using the techniques of mathematical programming, with some use of statistics and econometrics, and network analysis, have developed models for regional, national, and international forecasting, and policy formulation and analysis. In this short reveiw we will examine the application and methodology of some selected energy system models. The fact that a model has been developed for this or that process usually evokes the image of complex mathematical equations and some form of overwhelming complexity that is not understandable to the average person. Sometimes the smallest result of a model can have great impact on society because models are viewed by many as complex and thus, some- how truthful. Yet models may be complex or simple depending upon the needs of the question for which the model is attempting to give an answer. 28 Sme judgment 1' simple judgment} performance of a minimum as w‘: ride electrici theoretical de are more appro aethods, and l I from the scier‘ Energy 5:, cmlwersion prcl mdels of inte and just about modeled, and ti 80ns_ Many Er intereSt in e this review . HOI fman “bl Ch they a} 29 Some judgment is always involved in developing a model and in some cases, simple judgmental models can provide good information if only overall performance of a process is needed; in other cases, judgment is kept to a minimum as when deciding optimal allocation of generation mix to pro- vide electricity to a varying electrical load. In these cases, the theoretical description from relevant disciplines and applied mathematics are more appropriate. The choice of theoretical structure, analysis methods, and level of detail are part of the art of modeling as distinct from the science of modeling. Energy system models have been developed for engineering models of conversion processes, like electric power plants, all the way up to models of international supply and demand of energy in its various forms, and just about everything in between. The nation's economy has been modeled,and the energy sector itself has been modeled for different rea- sons. Many energy-related models have been developed with the primary interest in ecosystems, or physical processes, they are excluded from this review. Hoffman and Wood classify energy system models according to the purpose, normative or descriptive analysis and predictive purposes, for which they are employed. When normative analysis is the objective, the impact on the system of changing some element or process, that is an exogenous event in the model, is sought. Whereas, predictive models are used primarily to forecast energy states of supply and/or demand and associated constraints for future time periods (Hoffman and Wood, 1976). In truth, almost all models have both normative and predictive abilities and this type of classification is only useful to indicate the relative objective of a model. Validatior power of the ml is always presl events can det | methods used f | evaluating the | ample, normati respond to evel usually concerl fication of irI 10Sical structl Three lex, Wood. First, SYStem will t; predict the m. faCtOl‘ and th magnitude to Enet-gy SI 30 Validation and the treatment of uncertainty are important for the power of the model and is related to the methodology used. Uncertainty is always present in any real system and how the model handles these events can determine the usefulness of the results. The variety of methods used for dealing with problems of uncertainty are important in evaluating the predictive capability and validating the model. For ex- ample, normative*models deal mainly with how the given system should respond to events, given an objective, and validation issues are then usually concerned with the structural grouping of components and speci- fication of input parameters. Whereas, for predictive models, the logical structure of the model and its predictive power are important. Three levels of predictive capability are identified by Hoffman and Wood. First, there is the ability to predict the direction which the system will take given changes in some factor. Secondly, the ability to predict the magnitude and direction to different policies of some other factor and thirdly, the ability to predict the direction and absolute magnitude to a perturbing factor. Validation on the first two levels is a minimum for any predictive model, while validation on the third level is not always possible or necessary. In fact, many models cannot be validated on the third level, but are quite useful. III.1 Methodologies Energy system models are derived using theoretical and analytical descriptions of components taken from a wide range of disciplines; engi- neering, economics, operation's research, and management science. Gen- eralizing a little bit, economic models tend to deal mainly with the * Normative, as in the dichotomy between normative and descriptive. Natural science excludes the normative to concern itself solely with how things are. behavioral the! Engineering ens nical aspects ‘ models tend to, new technologi see FEA, 1976, and Process co, System. In th new technologi SUPPlY/dEmand Methodolc mathematiCal h and statistic4 Hath"mat: ques and email In the majOI-i a gI'OUP Of 3'1. “this of straints , am sent reality function 0 mized’ Le ' s algori thms a e “‘08 line ar Frog} Sc ale probh as I SOClated \ 31 behavioral characteristics of policies to produce and/or use energy. Engineering energy models have tended to deal with physical and tech- nical aspects of conversion processes. The objective of behavioral models tend to deal with alternatives, modification, or creation of new technologies that are better then existing alternatives. Lately, see FEA, 1976, energy system models have incorporated both behavioral and process components to provide a more complete description of the system. In the case of FEA, this was done to evaluate the emergence of new technologies, i.e., gasification of coal, oil shale, etc., on the supply/demand and price of energy in the United States. Methodologies used to implement energy system models ranges from mathematical programming (LP and nonlinear programming), econometrics and statistical methods, to methods related to network analysis. Mathematical programming methods have been used to describe techni— ques and engineering details of energy processes with economic factors. In the majority of cases, mathematical programming exhibits the model as a group of simultaneous equations, the variables of which represent the activity of specific processes. Activity variables are grouped in a matrix which defines such things as demand requirements and supply cdn- straints, and other technical descriptions that are intended to repre- sent reality as close as mathematical equations allow. An objective function or performance function is defined, which is minimized or maxi- mized, i.e., cost, profit, supply or demand, and any number of computer algorithms are used to solve the equations. The most popular of the mathematical programming techniques is linear programming, mainly because LP methods can efficiently solve large- scale problems. Also, the dual problem formulated in terms of prices, associated with any LP problem formulated in terms of quantities, is a direct and Mt aethods, such used for gener clude environrr. determining op Input-out analysis of th I economic actix Unit. The has and zero price level of Query EOOds and Sefi Economet Sentation and The Principal fiodel derive which the ob. testing the 32 direct and attractive link between processes and economics. Other methods, such as LaGrange multiplies, and variational methods are used for generally normative purposes. These later methods can in- clude environmental or regional characteristics, which result in determining optimal strategies for specific objectives. Input—output methods, that started with Leontief's input-output analysis of the economic system, have been applied using conversions of economic activity into a standard unit of energy, the British Thermal Unit. The basic assumptions for these models include a fix technology and zero price eleasticity. Their primary use is in determining the level of energy use required to reach a certain level of demand for goods and services. Econometric methods are generally concerned with empirical repre- sentation and validation of economic theories (Hoffman and Wood, 1976). The principal method is regression analysis combining the economic model derived from theory with a statistical model of the process from which the observed data are assumed to be generated. Examples include testing the hypothesis that a particular parameter is not significantly different from zero, that parameters in different equations of the model are not significantly different, or that combinations of parameters are equal to some specific value. The system dynamics approach evolved from the study of industrial operations. These models use simultaneous linear and nonlinear equations to describe components of the model with the use of feedback relation- ships included in the structure of the model. The biggest problem con- fronting these models has to do with validation. The functional relationships between components in system dynamics models, demand that modelers make judgments that are not always shared by other stude powerful, they their scope. I energy, resouri vich and Pestc 111.2 Energy The vast This review wi S‘jstem dynami‘ Many of or demand for electricity 3 recemly Surv tricky (TayJ ”‘31ng the is dependent the regulate The gas vation polic dependent u driven. automObiie demand mode 33 by other students of the system. Although system dynamic models are powerful, they have been evaluated through a jaundiced eye because of their scope. One of the latest models includes world development in energy, resources, economics, the environment, and population (Mesaro- vich and Pestel, 1974). 111.2 Energy models The vast majority of energy system models are of the economic type. This review will consider a few different types of economic models then system dynamic models. Many of the economic models have as their primary focus, the supply or demand for specific fuels or energy forms. The demand for gasoline, electricity and oil receiving much of the modeling attention. Taylor recently surveyed the econometric demand models of the demand for elec- tricity (Taylor, 1975). He reviewed the special problems associated with modeling the demand for electricity, complicated by the fact that demand is dependent upon the utilization rates of equipment and the effects of the regulatory process and price schedules. The gasoline demand model developed by Sweeney examined the conser- vation policies affecting automobiles. Gasoline use is a derived variable dependent upon average miles per gallon and the total number of miles driven. Where real disposal income, unemployment, and cost per mile of automobile travel determine demand for vehicle miles. Other petroleum demand models have been developed by Lay and Verleger. The study of the need for industrial expansion or the need to under- stand the impact of different regulatory policies on the energy industry has produced much modeling of industrial markets. For example, Adams and Griffin combined as LP model of the U.S. refining industry with an econometric moc demanded, and ‘. and Griffin, 1’ Mathemati of electric ut over 50 models of dynamic prc sing (Andersor Analysis 13‘3“? by the used the app“ was on quanti1 an accounting com[JIEte acco conversion pr COBSumptiOn a efficiencies West, 1972) . 34 econometric model for determining endogenously the prices, quantities demanded, and inventory adjustments for major petroleum products (Adams and Griffin, 1972). Mathematical programming has been used extensively in the analysis of electric utility operations and expansion plans. Anderson reviewed over 50 models used by that industry and found models using the methods of dynamic programming, linear programming (LP), and nonlinear program- ming (Anderson, 1972). Analysis and modeling of the overall energy system were stimulated largely by the need to forecast total demand. Barnett, Dupree and West, used the approach of energy balancing for all energy forms. The emphasis was on quantity flows expressed in a common physical unit, the BTU. As an accounting approach, the energy balance system focuses attention on a complete accounting of energy flows from original supply sources through conversion processes to end-use and the approach accounts for intermediate consumption and losses of energy during conversion processes as well as efficiencies at various points in the energy supply system (Dupree and West, 1972). When process models are used with the energy balancing approach the model encompasses all alternative fuels and energy sources, and frequently employs network analysis in order to represent technical detail. The net- work is used to describe the spatial flows of energy as well as the alter- native processes and fuels that may be used in specific demand sectors. In addition, these models of energy systems can be augmented with optimi- zation or simulation techniques to examine behavior and options. Baughman used a system dynamic model to study interfuel competition by simulating the flow of resources like coal, oil, gas, and nuclear fuels .fl to the various (Baughman, 197i and to determi: and the availa A system Neill, Miller role of coal i resources to r. 35 to the various demand sectors, residential, commercial and industrial (Baughman, 1972). The model is used to simulate interfuel competition and to determine quantities, prices of fuels, and energy sources as demand, and the availability and cost of changing resources. A system dynamics model of the coal industry has been developed by Naill, Miller and Meadows. The purpose of the model was to study the role of coal in the transition of the U.S. energy system from non-renewable resources to renewable resources up to the year 2100 (Neill, et a1, 1974). Time delays associated with R 5 D and plant construction for the synthetic fuels sector add to the models' realism. Where, the demand for energy anui the markets share of various fuels are determined endogenously as a functitnl of price, GNP, and population. The last type of energy system models covered in this short review are the world or global models championed by the Club of Rome. The first of these energy/society models was developed by Meadows, et al, in 1972. :I'_h_e_ Limits to Growth was a simulation model using the methods of industrial dynamics developed by J. Forrester. While the energy sector is only a some part of the models developed by Forrester, Meadows and followers, later world models would consider the energy system explicitly. The most significant example of this is the global model of Mesarbvich and Pestel. This model encompasses energy, resources, economics, the environment, and population. The energy submodel consists of an energy resource model, a demand model, and an energy supply model. Statistical information on energy resources allowing for uncertainty of the resource and the feasi- bility of recovery, and a simulation of the production of resources are included in the resource model. The demand model describes the demand for energy as a function of GNP and the supply model covers 13 primary and 7 secondary forms of energy along with the associated conversion process. 111.3 Sum This I some energy sing, line; vich statis and networi trial markl gests that and regula models. P cision of 36 111.3 Summary This review has examined the methodologies, and applications of some energy system models. Methodologies included mathematical program- ming, linear programming, nonlinear programming, econometric methods some with statistical methods added, input-output methods, system dynamics, and network analysis. Applications reach from regional analysis, indus— trial markets analysis to national and world models. All of which sug- gests that a broad range of possibilities exists for supporting policy and regulatory behavior at all levels with the proper use of energy models. Policy makers, and planners can benefit by the power and pre- cision of energy models. The lirr. and uranium, sometime in to adjust tc use energy, of the 20th tragedies 01 “easy of e, Today average hea Diesel engi used in Pas way we “Se lights are PErcent 9f CHAPTER IV THE DUAL-PURPOSE PLANT The limitation on physical forms of energy, coal, hydrocarbons, and uranium, is clearly a reality (Hubbert, 1971). This means that sometime in the future inhabitants of the space ship earth will have to adjust to many energy related problems, as a result of the way we use energy. Future generations, after examining the industrial society of the 20th century, will surely recognize that one of the greatest tragedies of that era was the almost complete disregard for the effi- ciency of energy use. Today our electric power plants convert only 32 percent (based on average heat rate) of the primary fuel burned into electric energy. Diesel engines, considered better then the internal combustion engine used in passenger cars, have efficiencies of around 36 percent. The way we use energy in the house is even more appalling. Incandescent lights are only 5 percent efficient, and an electric clothes dryer 50 percent efficient (not including the efficiency of the plant). The home furnace, while 60 percent efficient in top condition, is probably considerably less efficient in actual operation because of poor main- tenance and installation. There are strict upper levels to efficiency of use for every fuel, as defined by the laws of thermodynamics. But with energy so cheap and seemingly plentiful in the past, we paid little attention, until lately, to the efficiency of energy use. We now face the real 37 prospects of I this implies. plants at suc‘i used, and wha special quali tinue to use Many prc doing more of efficient aiJv Sistems and c 3911 and hydri- CEHS. VhGre ax furnace ; The app energy is a savings in e cmfld be USe AS an altern- from load Cel load Centers In this USEd to prOg a dual‘puer 38 prospects of running out of oil and natural gas, and the drastic changes this implies. Can we afford to continue to burn fuels in electric power plants at such low efficiencies? Where should oil and natural gas be used, and what efficiency of use should we expect? Since there are special qualities associated with oil and natural gas, can society con- tinue to use these fuels to generate electricity? Many proposals to increase the efficiency of energy use involve doing more of what we already do; insulating, recycling, making more efficient air conditioners, etc. Other proposals point to alternative systems and devices. For example, a molecular sieve for separating oxy- gen and hydrogen is a device idea, possibly opening the way for fuel cells. Whereas, pumping ground water through coils inside a forced air furnace is a system's idea. The application of heat produced during the production of electric energy is a system's idea which provides possibilities for significant savings in energy use. Heat energy in the form of steam or hot water could be used, after producing some electrical energy for other tasks. As an alternative to large electric power plants located great distances from load centers, smaller dual-purpose plants could be located near load centers providing steam as well as electricity. In this chapter the activities of the district heating business, the current applications of dual-purpose plants, the turbine systems used to produce electricity, and the energy efficiency associated with a dual-purpose plant are presented. IV.l District Heating District heating is the use of large steam generators (boilers) to provide steam for residential, commercial, and industrial consumers of steam. Toda steam genera by the use 0 idea favorat the district to meet a g] separated ej business of "13 Power. DiStri b11110n P0u (SChUSter, showed a he 1950's, Uti appears the of energy. Pei-{Owed V steam, and The d1: produce e1 USEful’ 11: t0 low‘tem ing. 39 steam. Today, most district heating companies use packaged industrial steam generators to produce steam which is distributed to steam users by the use of underground steam pipes. For many years district heating was a form of public—utility ser- vice that prospered after a slow beginning due to the lack of engineer- ing develOpment. District heating has been popular in the Middle West, with both small and large cities of Ohio, and Indiana receiving the idea favorably. As time passed, electric power companies got out of the district heating business and concentrated on larger power plants to meet a growing demand for electricity. The majority of companies separated electric and steam production, while others got out of the business of trying to supply anything other than cheap reliable elec- tric power. District heating systems in the United States sold more than 81 billion pounds of steam in 1970, and served almost 15,000 customers (Schuster, 1971). For the 15 years prior to 1950, district heating showed a net gain, but the rate of growth was erratic. After the 1950's, utilities began to promote district heating, and since then steam sales have increased 53 percent (Schuster, 1971). Thus, it appears that there are plenty of tasks for which steam is a useful form of energy. With the growth of district heating proof that many tasks performed with the use of other fuels can be performed with the use of steam, and that there are many potential consumers. The dual-purpose electric power plant is a technology that can produce electricity, for which electricity is the only form of energy useful, like for lighting, computers, etc., and steam, to provide energy to low-temperature tasks like space heating and cooling, and water heat- ing. n.2 Appli The du power stati significant steam users the dual-pi center", or purpose pl; Jersey, Ohj One 01 Operated b} Ethyl Corp< Electric w: hm” (IECS In Ne! been SUPPlj Pounds of are fumis' steam, Exx Publi tion to Dr to Supply oratio“. with no re located 80 supplied t} trict heat 40 IV.2 Applications of Dual-Purpose Plants The dual-purpose plant is a particular type of central electric power station, usually built by the utilities, which also furnishes a significant amount of steam to one or more steam users. When several steam users, typically industrial customers, are grouped near or around the dual-purpose plant it is frequently referred to as an "energy center", or a "nuplex" if the plant is nuclear-fired. Examples of dual- purpose plants can be found in the states of Michigan, Missouri, New Jersey, Ohio, Washington, Indiana, Delaware, Louisiana, and California. One of the oldest dual-purpose plants was built in 1930 and is operated by the Gulf States Utilities Company. Supplying steam to the Ethyl Corporation and Exxon Company, the plant produces 240 megawatts electric with a total steam generation capacity of 5 million pounds per hour (IECS, 1975). In New Jersey, the Public Service Electric and Gas Company has been supplying Exxon with steam since 1957. Between one and two million pounds of steam per hour, at 150 psi (1 M newtons per square meter), are furnished with the use of extraction turbines. In exchange for steam, Exxon supplies fuel to the utility. Public Service Indiana did not originally design the Cayuga sta- tion to produce process steam, but in 1975 completed the change over to supply 225,000 pounds per hour of steam to the Inland Container Corp- oration. By tapping the cold reheat header, process steam is produced with no return condensate received from Inland. Inland Container is located some 9,000 feet (2743 meters) from the Cayuga plant. Steam is supplied through a piping system, much like the system used by dis- trict heating companies. The smners Po‘ share of dual-purp Expected supply 4 of electr An a the dual- helped vi Israel, ar ROE, and t the Energ from 3 d1 other im 41 The first nuclear dual-purpose plant is being built by the Con- sumers Power Company of Michigan. This company has had more than its share of problems with nuclear power in the past, and problems with the dual-purpose nuclear plant at Midland have delayed it until the 1980's. Expected to come on-steam much sooner, the Midland plant is designed to supply 4 million pounds per hour to Dow Chemica1,and generate 1300 MW of electrical power (EICS, 1976). An agro-industrial complex, designed for developing countries, uses the dual—purpose plant technology. Oak Ridge National Laboratory has helped with studies of agro-industrial complexes for India, Pakistan, Israel. and Egypt (Beall, 1971). A Puerto Rican study done by Burns and Roe,and the Dow Chemical Company for the Atomic Energy Commission - now the Energy Research and Development Administration - planned to use heat from a dual-purpose nuclear plant for petroleum refining, irrigation,and other industrial uses. The Southern Interstate Nuclear Board and the State of Texas have undertaken studies, the one in Texas supporting a large group at Texas A G M University, to produce conceptual designs of a nuplex. Kentucky and Maryland have done similar studies (Beall, 1971). Many of the re- sulting studies have concluded that electric-heat, or dual-purpose plants, are an attractive option from economic, conversion, and environ— mental points of view (Beall, 1971). Urban applications of dual-purpose plants have been investigatedtnr the Department of Housing and Urban Development. The problems of in- stalling a central heating supply system, pipes, valves and meters, in any existing city was thought to be too difficult and studies were. limited to a hypothetical new city. The resulting study by Miller et a1 postulated 2 Philadelphi by the dist water heati meters) hea hectares) 0 total popul cared about examined th than just 1;} favorable p. Vater can er considered , IV.3 AdVan' The ba: Utilization plant Produ. “Grams. ( the environ some of the and Sends i 1M0 eleCt r heat only iIIUStrat 1Q the primary 42 postulatedaanew city of 389,000 people living in a climate similar to Philadelphia's. Sixteen square miles (41 square kilometers) is served by the district heating system using heated water for space heating, water heating, and air conditioning. Within a 5-mile radius (8 kilo- meters) heated water is supplied to a sewage plant, and 200 acres (81 hectares) of greenhouses. Two hundred fifty-eight thousand of the total population reside within 12 square miles (31 square meters) lo- cated about 7 miles (11 kilometers) from the nuplex. This grand study examined the economics of applying a large nuclear plant to other tasks than just the production of electricity. And results indicated that at favorable population densities of 21,000 people per square mile, heated water can economically be supplied to large cities within the design considered. IV.3 Advantages of the Dual-Purpose Plant The basic advantage of the dual-purpose plant lies in the increased utilization of energy. Simplified in Figure 4.1, the conventional power plant produces only about 40 percent of the input energy as electric energy, E. Over 60 percent of the primary fuel burned is dissipated to the environment as waste heat at the p1ant,H- The second design extracts some of the steam, after it has produced some shaft work in the turbine, and sends it into a steam distribution system where the remaining energy is used. In the design shown, 35 percent of the primary fuel is turned into electricity, 35 percent is extracted for other purposes, and waste heat only accounts for 30 percent. The ultimate design would be the last illustration where a back—pressure turbine is used and 30 percent of the primary fuel is produced as electricity, and the remaining 70 percent ' o is used in t euvironmen c0nsi energy and commercial TESOUrCes Stituting triCity t( tasks are 43 is used in other processes. No waste heat must be discharged to the environment at the plant when using the back-pressure turbine. Bunyan anmuhuuw i-u>E-405 4GB -H>fl -605 Commie"! 35% huufiUI 'h finnyun gunning E-JW! IN! N -flfl5 Dallas's Figure 4.1 Turbine Types Reference: Beall, S. E. 1973. Total Energy - A Key to Conservation. Consulting Engineer 40 (2): 180. Considered at the community level, dual-purpose power generation can decrease overall fuel requirements for the generation of electric energy and the supply of low-temperature energy used in the residential, commercial, and industrial sectors. Also the use-of very limited fossil-fuel resources like gas, and oil are also removed from the community, sub- stituting hot water or steam. In addition, the misapplication of elec— tricity to provide space heating and cooling, water heating, and other tasks are eliminated, and these terribly inefficient (when plant effic- iences are included in the total efficiency calculation) processes are replaced by in the whole community is pated to the IVA Turbi‘ Three electrical condensing expands prj and 538°C) from lakes the Rankine 40 to 60°F by Creatin prOhlb i t t 44 replaced by the use of steam or hot water. Since less fuel is burned in the whole community, the release of combustion products in the urban community is also decreased, and at the plant less waste heat is dissi- pated to the environment through cooling towers, ponds, etc. IV.4 Turbine Systems Three types of turbines can be used to generate electricity in an electrical power plant; condensing, back-pressure, and extraction. The condensing turbine, used in the vast majority of today's power plants, expands prime steam at around 2,400 psia and 1000°F (16.548 M newtons/m2 and 538°C) through a turbine and condenser. Condenser cooling water, from lakes, rivers and streams, plays an important part in determining the Rankine efficiency of the turbine. Water at ambient temperatures, 40 to 60°F (4 to 16°C), increases the available energy (work producing) by creating low-temperature conditions in the condenser. Where laws prohibit the use of natural bodies of water, cooling ponds or cooling towers are used. Since towers return condensing cooling water at 100°F (38°C) to the condenser, they have the distinct drawback of decreasing Rankine efficiency. Production of electric energy with the condensing turbine results in 60 to 70 percent of the primary fuel burned ultimately discharged as waste heat to the environment. Putting to practical use this enor- mous amount of energy has charmed many investigators (Jensen 1971, Miller 1971, Beall 1970) in the past. Only a few low-temperature uses like greenhouse heating, waste treatment, and fish ponds are technically able to use this degraded heat. While uses of this low-temperature heat are rather limited, the low cost and small affects on plant operation ad of possible The ba number of cl to a predett then moved is used by ment is use The ba can be tern heat exchan the steam jJ no waste h( The only e: transPort, in teI‘ms OJ equipment ‘ maticauy o The b Panies and Steam is p maintenanc EUOUBh t O I the many r 45 operation and efficiency, make continued economic and technical analysis of possible applications worthwhile. The back—pressure turbine system is practical in only a limited number of cases. In general, prime steam is expanded through the turbine to a predetermined lower pressure, generating some electricity. Steam is then moved to the rest of the system by pumps where the remaining energy is used by industrial, commercial, and residential users. This arrange- ment is useful if there is a large demand for steam at high temperatures. The back-pressure turbine can be designed so that steam expansion can be terminated at almost any pressure and permitted to exhaust into heat exchangers or a piping system at the desired pressure. Since all the steam is exhausted into a system using the remaining energy, ideally no waste heat must be discharged to the environment at the plant site. The only energy loss in this type of system is the result of losses in transport, heat exchangers, etc. The overall efficiency of the system, in terms of energy use, approaches 100 percent (Beall, 1973). The equipment arrangement for a back-pressure turbine system is shown sche— matically in Figure 4.2. The back-pressure system works well for both electric power com- panies and steam users only if the steam users are always ready when steam is produced, and if steam users can be cut-off during power plant maintenance periods. But the constraints of locating steam users close enough to the power plant to be economical, the problems of planning and construction time differences between users and the power plant, make the back-pressure system quite inflexible, and are counted among the many reasons why power companies are not involved in selling steam. Steam Gene F—_— PI The ext dEmand is Sn m0re than 0! Piling, and E Demits elec turbine and preSSUr'e s EXtract the Steam 1( the turbine, SChematiC d] The ex: 138 the 11mm 46 Steam Generator Generator Load Turbine I '—<3— Industrial Pégé J! Commercial :: Users Heat Exchanger Figure 4.2 Back-pressure turbine The extraction turbine system by contrast can be used where steam demand is small to moderate. Steam can be taken from the turbine at more than one point enabling industrial steam to be extracted at one point, and steam at lower pressures to be taken at other points. This permits electrical power to be generated by steam expansion through the turbine and removed at the desired pressure instead of throttling high- pressure steam to a lower pressure for some Steam users. Extraction turbines have the flexibility to be designed so that as the steam load decreases, the reduced steam load can be expanded through the turbine, increasing electrical power generation. Figure 4.3 is a schematic diagram of the equipment arrangement for the extraction system. The extraction system offers the greatest flexibility for increas- ing the number of steam users in the system,and as the system grows it may justify the case, the ex STEAM CHEER; ‘L'nr' 47 justify the addition of a back-pressure unit. but in the meet general case, the extraction turbine is the most useful. STEAK GENERATOR EXTRACTION TURBINE SYSTEM LOAD L__T_. _. ¢ ‘i GENERATOR EXTRACTED STEAM L“\» INDUSTRIAL, l (3 COMMERCIAL PUMP \\\\‘-;::/r USERS HEAT EXCHANGER JK Figure 4.3 Extraction'Turbine System IV.5 Automatic Extraction Automatic extraction units bleed off part of the main steam flow at one, two or more points. Valved partitions between selected turbine stages control extracted steam pressure at the desired level. When ex- tracted steam flows through the turbine does not produce enough shaft work to meet demand, more steam flows through to exhaust, increasing the electrical output. These turbines are put between the steam supply and process steam headers, diagrammed on the following page, Figure 4.4. Automatic governing systems correlate steam flows, pressures, shaft speed and shaft output for any one unit. 48 \ f V V V Singlooomomatic- Double-automatic- extraction omodion Figure 4.4 Automatic Extraction Turbine The extraction turbine has advantages over the back-pressure tur- bine system because it allows steam to be withdrawn at any needed pres- sure. Back-pressuring turbines also have no flexibility if the heat-users are temproarily removed from the system. The power plant can not economi- cally operate if there is a chance that the heat-users are unable to use the steam produced. Therefore, the extraction turbine is considered a better choice for the system under consideration since it can be expanded to meet demand from new heat-users added to the system. The extraction turbine reduces the amount of steam reaching the last stages of the turbine, thus, it also decreases the amount of waste heat produced, see Figure 4.5. The efficiency of electrical energy produc- tion is decreased, but overall efficiency of energy use is increased. IV.6 Energy of Steam and Electric Power The energy available in steam is the maximum work-producing capa- bility of steam when exhausted to a cold heat sink. In steam turbines the available energy of the steam is the work produced by the steam between the initial steam conditions from the steam generator to the level of the lowest attainable turbine exhaust pressure. In general, steam at the outlet is not capable of producing useful work unless a colder sink is used. RBducti ReJ'ecti at Cond on Cons trical Referen‘ 49 100 1.0 90 80 .75 70 60 Reduction in Thermal Rejection (percent) at Condenser Based on Constant Elec- .50 trical Generation 50 40 30 Ratio of Steam ~25 Extracted to Steam Input of Single-Purpose Plant 10 0 100 200 300 400 500 0F (38) (93) (149) (204) (260)0C Saturated Temperature of Extracted Steam Figure 4.5 Reduction in Thermal Rejection Reference: Miller, A. J., et a1. 1971. Use of Steam-Electric Power Plants to Provide Thermal Energy to Urban Areas. Report no. ORNL-HUD-14, UC-80 Reactor Technology, Oak Ridge National Laboratory, U. S. Department of Housing and Urban Develop- ment, Washington, D.C. 50 Ideal Rankine cycle work assumes that the steam is expanded through the turbine abiabatically to the condenser with no change in the entropy. In real processes, the expansion of steam must be accompanied with an increase in entropy, see Figure 4.6. Therefore, the useful work per unit mass of steam expanding in the turbine per unit time is: Turbine Work = hi - hf' where sf' > si and, _ 0 Electrical Power = h13z1%£- = kw, where kw = 3414 BTU/hour Because extracted steam is not available for electric power gen- eration, an extraction turbine has the same maximum work producing capacity as a single-purpose turbine, when no steam is extracted. When no steam is extracted, the maximum electrical output Bo and the mechnical output of the turbine, W max, would be: t W max . mi (hi - hf') EC 3414 341a where, mi = mass flow rate of steam generator, pounds per hour hi - initial enthalpy, BTU's per pound hf'= final or exhaust enthalpy, BTU's per pound If steam mx is extracted, the actual output of the turbine is: W actual . mi (hi - hf') - mm (hx - hf') Ea ‘ 3414 3414 The energy lost to electric power generation by the extracted steam is the difference between Ec and Ea, mx (hx - hf') EC ' E3 3 3414 8 Ex For Conditic tons /m2) (126 kg, kg/Sec,} district lbs/p10m PIesSurE comm“,lit newtODS/ ter has 51 ' Saturation Line Enthalpy h adiabatic actual J 1 l l L Entropy s MOLLIER CHART Figure 4.6 Turbine Expansion Curve For example, the dual-purpose plant shown in Figure 4.7 has throttle conditions of 4,000,000 lbs/hr. (504 kg/sec.) at 2400 psia (16.548 m new- tons/m2). Process steam is extracted in the amounts of 1,000,000 lbs/hour (126 kg/sec.) at 335 psia (2.310 M newtons/m2) and 2,000,000 lbs/hour (252 kg/sec.) at 150 psia (1.034 M newtons/m2). The later could be used for district heating and the former for industrial processes. Another 500,000 lbs/hour (63 kg/sec.) is extracted at 35 psia (.241 M newtons/m2) for low- pressure district heating and chillers producing cooling water for the community, and another 500,000 lbs/hour (63 kg/sec.) at 35 psia (.241 N newtons/m2) is used in the deareator and feedwater cycle.' The steam renorm— tor has a first law efficiency of 91 percent. thOMwm. K ..IUOP. a mama omH A was coo.ooo H moook name one 52 oocmamm umom magnuss unconsolamso n.< ouowwm moooouo Hmwuumov Home: on oxma use one monsoon uoopumoo mom ooo.ooo.H HORN wuwmfimfifiou fiHDuQH o ooo ‘ - a ow~ . r was ooo.oon.~#;c moo ooo ooo o woumouooo mam WV .moabo .wnwuoon wouuaoouu n «Hmu . - on: ooo.oom%m£ coo con RONnm ll. mama mm mmszmaa Hm. I : acumuoooo owed owuuomao annum 7 a ~49: and ooo ooo k. n can“ - hooooa A mom oooqoooqa mama coca moomn rel. a mom“ mama end A mpH oooaoooqa moooa «one man If a C an attainat assumed. and final : Computatio Ultin turbine: Elect Ea The Small is The tllrbine 1 “early 3C Electric extraCt 1C extracteC has an 0' “38d fOr Put of tl To tllrbine 53 If a condensing turbine was used instead of the extraction system, an attainable condenser back-pressure of 1.75 in Hg (604.28 kg/mz) is assumed. The exhaust enthalpy, hf', is 1,032 BTU/lb. (.398 M joules/kg), and final feedwater enthalpy is 228 BTU/1b. (.530 M joules/kg). Computation: Ultimate electrical output for the condensing (non-extraction) turbine: = 4,000,000 (1461.2 - 1032) EC 3414 = 502,870.53 kw Electrical output of the extraction turbine: Ea = [1,000,000 (1461.2 - 1388) + 2,000,000 (1461.2 - 1316) + 1,000,000 (1461.2 - 1214)] ——l—-= 178,910.37 kw 3414 The loss of energy for electric power generation by the extracted steam is the difference between: Ec - Ba 8 502,870.53 - 178,910.37 = 323,960.16 kw The efficiency of electric energy production from the extraction turbine is decreased. While the non-extraction turbine would convert nearly 30 percent of the prime steam energy, in this example, into electric energy, only 10 percent is converted to electric energy by the extraction turbine. The overall efficiency is quite different since extracted steam is used for other tasks. The extraction turbine system has an overall efficiency of nearly 70 percent since extracted steam is used for other energy requiring tasks, increasing the total useful out- put of the system. To compare the efficiencies of the convertional, and extraction turbine it is necessary to introduce the concept of available energy or active concept wh ' atmosphere result wo : in the se is a conc the 3Y8t8.,- this ’ We 5‘ m r1 (D c: l meaSLu-e tl 54 or active energy. Available energy is a second law of thermodynamics concept which specifies only harnessable work, not work done on the atmosphere. Work is the highest "quality" form of energy, and work is the best overall measure of the capacity for doing any task. If we measure the available energy and the useful work output of the conventional power plant with that of the dual-purpose plant, the result would indicate that the dual-purpose plant was not as efficient in the second law measure, as the conventional plant. What is needed is a concept which measures not only the available energy input to the system, but also the utilization of energy by the system. To do this, we define the following ratio. A): U A where U = the utility of the system y 8 utilization, W useful + Q applied (useful work + heat energy applied) A a availability The utility of a system as defined above, is a meaningful measure of the total benefit derived from a system in comparison with the ideal maximum which might be obtained and the utility measure provides a way to measure the effect of cascading energy systems. The conventional power plant has a utilization measure, y, that is electrical energy output. Whereas, in the case of the cascaded system of the dual-purpose or ex- traction turbine system, y is electric and heat energy output. Thus, not only has the utility concept included the work output, but it has also taken into consideration the use of energy in other connected systems. The available energy A of the steam inputted to the turbine is a theoretical measure of the maximum work producing quality of energy. Assumir can be vhere, Tf (5.73 )4 ply the energy Th t”109 t: Utility the 10W4 PUt (U84 like Sp; to, Cha busineSS 55 Assuming a cold heat sink of atmospheric conditions, the available energy can be found from the following relation 8 Q (TH - Tc) A TH where, A = available energy Q = heat energy added TH = hot input temperature Tc cold sink temperature The available energy of the system in Figure 4.7 is 5.44 X 109 BTU's (5.73 x 1012 joules). The utility, u, of the non-extraction or conventional turbine is sim- ply the work, electric energy output divided by the available energy A. u . y_= 1.72 X 109 (1.81 X 10lzjoules) = 9 12 32 5.44 X 10 (5.73 X 10 joules) The utility of the extraction turbine is the sum of the electric energy plus the usefully applied extracted steam, 9 12 9 12 u = y = .61X10 (.64X10 joules) + 2.80X 10 (2.95 X 10 joules)= .63 A 5.44 x 109(5.73 x 1012 joules) The utility of the extraction or dual-purpose plant can be nearly twice that of the conventional non-extraction system. To increase the utility of the dual-purpose plant, it would be best to extract steam at the lowest possible pressures. Thus increasing the electric energy out- put (useful work) and using the extracted steam for low-temperature tasks like space and water heating where useful work is not important. 1V.7 Summary Chapter IV has presented the activities of the district heating business, and has shown a desire on the part of consumers to use steam. Althou. mainly in t'. has been do he efficie yoxional p United ene vide low-ta a community 56 Although past applications of dual-purpose power plants has been mainly in the area of supplying steam to industrial uses, some research has been done to consider uses of the dual-purpose plant technology. The efficiencies of these plants is quite high, when compared to con- ventional plants, and with the added affect of reducing the use of limited energy resources and the inefficient use of electricity to pro- vide low-temperature heat energy, the total efficiency of energy use in a community using a dual-purpose plant can be greatly increased. The e America wi' ber readin ing coal t cellar or erally dic cleaning a In 1‘. the land t bed clothv Children buses and EVen illuminat hOmes we I Cities (E On fanns I CEntUry’ fires an( TeC 1925, 0v CHAPTER V ENERGY USE IN THE UNITED STATES The energy revolution in the twentieth century has transformed America within a lifetime. Over twenty million Americans still remem- ber reading by an oil lamp, gas lamp or candle, splitting wood or carry- ing coal to feed a pot-bellied stove. Storing perishables in the cool cellar or window box, they used tin basins or tubs to wash in and gen- erally did the tedious time-consuming chores of cooking, washing, and cleaning as everyday necessities. In 1900, the country farmers, which were most everybody, worked the land with muscle power, human and animal. Wives and daughters scrub- bed clothes, beat rugs, cooked in big pots over slow-demanding fires. Children walked to school, and after a few years walked to work. Motor buses and street cars were not common in cities until after the 1920's. Even though electric power was a reality by the turn of the century, illuminating some wealthy homes in 1880, only 8 percent of all American homes were wired for electricity by 1907, and then only in the larger cities (EPP, 1975). Mbst Americans were rural dwellers, 60 percent lived on farms and had no electricity and during the next few decades of the century, almost everyone still used kerosene for light, split wood for fires and walked just about everywhere. Technological changes came swift, making everyone's task easier. By 1925, over half of all homes were wired for electricity, mostly in the 57 58 cities. Natural gas was common in the thirties, and the number of cars had reached two million in 1920 (EPP, 1975). In 1943, FDR madelrhsfamous fireside chats to the nation by radio and by 1973, virtually every home in America had a television (Makhijani, et al, 1973). By the 1970's, Americans used directly in their homes over 23 quadrillion BTU's of energy (24 x 1018 joules) in one year. Consider- ing only electricity, natural gas, and gasoline, they used about 20 quad— rillion (1015) BTU's (21 x 1018 joules) (EPP, 1975). Today, energy used in the home, the residential sector, is estimated to be about one-fifth of all energy used in the United States (SRI, 1972). The major uses of energy in the household are shown in Table 5.1. On average, over 70 percent of the total energy used in the household is for space heating and water heating. TABLE 5.1 Major Uses of Energy in the Household space heating 57.52 water heating 14.92 cooking 5.52 refrigeration 6.02 air conditioning 3.72 television 3.02 clothes drying 1.72 food freezing 1.92 other 5.8% Reference: Patterns of Energy Consumption in the United States. 1972. Stanford Research Institute. Report no. 4106-0034, GPO: 33. Air conditioning, shown as 3.7 percent in 1968, is quickly approaching the position of the third largest user of energy in the household. Satura- tion levels for air conditioners, central and room, rose from 12.8 percent 59 in 1960 to 36.7 percent in 1969 (Makhijani, 1973). With the result that in a typical household energy used by air conditioning is now almost 12 percent of the total. Despite today's energy servants, it is debatable whether Americans have more leisure time than they did a generation ago. Time spent is housework, for example, is substantial, and has not changed for most American women since their grandparents era (Vanek, 1974). v.1 Energy Statistics for the United States Between 1950 and 1970, the United States use of energy resources (coal, hydrocarbons, falling water and uranium) doubled at an average annual growth rate of 3.5 percent, more than twice the pOpulation growth rate (EPP, 1974). By 1968, the transportation of people and freight accounted for 25 percent of total energy use, with space heating of homes and commercial establishments using almost 20 percent of the total (SIR, 1972). Industrial use accounted for 41 percent with the remaining 14 percent used in the commercial and residential sectors for water heating, air conditioning, refrigeration, cooling, etc. see Table 5.2. The growth of electricity use has been increasing at break-neck speed. Between 1960 and 1970, while the use of primary fuels, coal, hydrocarbons, etc., grew by 51 percent, the use of electricity grew by 104 percent (Edison Electric Institute, 1971). In 1970, electric power generation accounted for 24 percent of total energy resource use as compared to 19 percent in 1960 (Hirst, 1973). This increasing use of electricity, much of it by substitution for other fuels, is important when accounting for increased energy growth rates, because of the in— herently low efficiency of electric power production. Residential W Water he Cooking Clothes Refriger Air con Other 1 60 TABLE 5.2 Energy Consumed, By Sector and End Use As A Percentage of National Tota1* 1968 Purchased Electrical Direct Energy Residential Space heating 10.22 0.72 Water heating 1.9 1.0 Cooking 0.7 0.4 Clothes drying 0.1 0.2 Refrigeration nil 1.6 Air conditioning nil 0.3 Other nil 2.1 Total 12.92 6.32 Commercial Space heating 7.0 nil Water heating 0.6 nil Cooking 0.1 0.3 Air conditioning 0.3 1.5 Feedstock 1.6 --- Other nil 3.1 Total 9 62 4.92 Industrial+ Process steam 20.7 Electricity generation 0.7 Direct heat 7.0 Feedstock 3.6 Total 32.0% 9.22 Transportation 25.0 0.1 Total 79.52 20.52 * Including heat wasted in production of electricity + Purchased electricity not allocated separately. Sources: Bureau of Mines. Stanford Research Institute Total N NOI—‘Ol-‘NO HUG‘UHQO 19.22 WHHCCN HChmJ-‘O‘O 1-‘ 9 Ln N 41.2% 25.1 100.02 Reference: Patterns of Energy Consumption in the United States. 1972. Stanford Research Institute. Report No. 4106-0034, GPO:16. End- From this natively electric heating, use stear percent 1 Refere 61 End-use of energy in the United States is presented in Table 5.3. From this table it can be seen that many end-uses of energy could alter- natively be supplied by the use of steam taken from a dual-purpose electric power plant. Space heating, process steam, direct drive, water heating, some air conditioning, some cooking and refrigeration could use steam as an energy source This group alone accounts for over 50 percent of the total energy used in 1970. TABLE 5.3 End-Use Energy in the U.S. Item 1970 Percent of Total Transportation 24.7 Space heating 17.7 Process steam 16.4 Direct heat 11.0 Electric drive 8.1 Raw materials 5.6 Water heating 4,0 Air conditioning 2.9 Refrigeration 2.3 Cooking 1.2 Electrolytic processes 1.2 Other 4.9 Reference: Efficiency of Energy Use in the United States. 1973. Hirst, Eric and John C. Moyers. Science, 179 (4080): 1300. 62 In many communities across America there is great potential for the use of steam extracted from the electric power plants, witness the growth of the district heating business. Space heating, water heating, and in some cases air conditioning in the residential sector, could use steam as an energy source. And the commertialzuuiindustrial sectors could make very good use of steam in their processes. In Table 5.4, some of the possible process steam uses are listed for the commercial and industrial sectors. TABLE 5.4 Major Steam Process Users Asphalt companies Plastics company Chemical companies Restaurants Dairies Snow melting Flour drying . Soft drink and breweries Heat treating Steam cleaning Humidification Steam hammers (forging) Laundry Sterilization Leather tanning Stills Lumber drying Tire vulcanizing Organic fertilizer company Water heating One of the real positive benefits of substituting steam for other energy resources used in the residential, commercial,and industrial sec- tors is that many of these tasks require only low temperatures ( 500°F, 260°C). To use electricity, natural gas, or oil as an energy source to heat water (150°F, 60°C) or to warm a structure to 70°F (21°C) is a waste- ful application of energy. Especially if one looks at the community as 63 a whole unit. For example, in one location, the community's electric power plant wastes about 60 percent of the primary fuel burned, dissipating this low-temperature heat into the environment, and at separate locations throughout the community various potential users of low temperature heat use electricity and natural gas to heat water, warm buildings and to do other low temperature tasks. Clearly, we cannot tolerate this waste in the future. Consider the electric water heater, the first choice for water heaters in the residential sector, after the primary fuel has been burned to produce electricity at 32 percent efficiency the temperature of the water in the water heater is raised to only about 150°F (66°C) and left to sit most of the day. When one adds in the losses incurred in trans- mission and distribution of electricity,at best this use of energy is only 32 percent efficient. And even then the electricity used provides only the same service, wood, coal or even the sun could have provided. Elec- tricity has unique prOperties for which only electricity is the energy source. Lighting, running computers, business machines, etc., are tasks that can only be done by electricity and it is a poor choice of energy re- sources to use electricity to heat water. V.2 Space Heating Space heating in the residential sector requires about 11 percent of the total national energy use, while the space heating in the commercial sector uses an additional 6.9 percent of the total (SR1, 1972). Energy use in home heating is influenced by the design of the dwell- ing, the climate, and the ways people use their homes. The most signifi- cant climatic parameter for energy consumption in the home is average daily temperature. To estimate the amount of heat required to keep the interior of a structure warm, given fluctuations in outside temperature, it is inst in the tem Assum of floor 5 msmm tha the outsid fer proper the wall a about 1 (E thickness? times larg. considera SUlatlon, the them face resi I which de; PEr unit inside ar has "8115 inches (: thermal 1 The resu additIOn ab°ut 15 (70C)_ 64 it is instructive to consider the energy balance of a "standard house" in the temperate part of the United States. Assume the "standard house" has 1500 square feet (140 square meters) of floor space, with dimensions 25 X 30 X 20 feet (7.6 X 9.1 X 6 M). Assume that the inside temperature is maintained at 70°F (21°C),iwh11e the outside temperature averages 32°F (0°C). To calculate the heat trans- fer properties of the wall structure, one treats the layers that make up the wall as a set of resistances in series. Wood has a resistivity of about 1 (BTU/hr ft2°F)-1 per inch of thickness [.069(W/m2°C)-'1 per cm. of thickness]. The thermal resistivity of fiberglass insulation is about 4 times larger. Of course, a more careful consideration would take into consideration the non-uniformities of the studs and air holes in the in- sulation, but this should give a fairly close approximation. Added to the thermal resistances of the solid materials and trapped air are sur- face resistances, describing the heat transfer from the wall to the air, which depend on air velocity. Typical values for surface resistances, per unit area, are .8 and .2(BTU/hr ftzoF)"1 [.14 and .035(W/m2°C)-1] inside and outside faces of the walls, respectively. The "standard house" has walls with about 2 inches (5 cm.) of insulation and a roof with 4 inches (10 cm.) of insulation. Unit areas of the wall and roof have thermal resistances of 10 and 18(BTU/hr ft2°F)-1 [1.8 and 3.2(W/m20C)-1]. The resulting heat loss through the walls and roof of the ”standard house" is 9943 BTU/hr (2912 watts). Conductive losses to the ground add an additional 1875 BTU/hr (555 watts) if floor materials are about the same as wall materials. The effect of a basement is to lower this figure to about 1500 BTU/hr (438 watts). Ground temperature is assumed to be 45°F (7°C). Vi or they If 200 overall value f Since t surface across with 2( watts) TEducit total ‘ A' ing of f0! ch incomi k“Gym. BTU/hr OUtSit atlea watts} Stanc amOUnt With E 65 Window heat losses cantnevery large if the windows have no curtains or they are left uncovered during the night, even if they have curtains. If 200 ft2 (18.6 m2) of wall area is replaced by windows, there is an overall increase transfer of heat to the outside. A typical resistance 20r)‘1 [.l6(W/m2°C)-1]. value for single-pane windows is around .91(BTU/hr ft Since the transfer of heat through a window is dominated mainly by the surface resistances of the inside and outside layers, temperature drops across glass are usually only about 1°F (.5°C), the "standard house", with 200 ft2 (18.6 m2) of windows loses an additional 8352 BTU/hr (2446 watts) by conduction through the windows. But the wall area is decreased, reducing by 760 BTU/hr (223 watts) the heat loss through the walls, or a total of 9183 BTU/hr (2689 watts) for the walls and roof. Air enters the house, called infiltration, through cracks and open- ing of doors. One air exchange per hour is a reasonable approximation for the "standard house" (ATP, 1975). Since heat must be added to the incoming air to raise it to 70°F (21°C), the total air space must be known.- The "standard house" has 15,000 ft3 or 1,100 pounds (500 kg) of air, one air exchange per hour requires another 10,032 BTU's or 10,032 BTU/hr (2938 watts). Assuming that the relative humidity is 60 percent outside and 20 percent inside, the humidity of incoming air must be raised atleast 40 percent. To evaporate water, another 2800 BTU/hr (111 watts) is required. We can now examine the total energy lost by the "standard house". This figure, 33,242 BTU/hr from Table 5.5 represents the amount of heat required to keep the "standard house" at about 70°F (21°C) with an average outside temperature of 32°F (0°C). Clearly, the effects of insulation and reducing the number of air exchanges experienced by a house can greatly reduce the amount of energy 66 required for space heating. The effect of insulation standards will be examined shortly. TABLE 5.5 Estimated Energy Requirements for a "Standard House" Percental BTU/hr (watts) of total Heat lost through walls and roof 9183 (2,689) .28 Heat lost to ground 1875 (555) .06 Heat lost through windows 8352 (2,446) .25 Heating of incoming air (air exchange) 10,032 (2,938) .30 Humidication of incoming air 3800 (1,113) .11 TOTAL 33,242 (9,736) V.3 Degree-Day Method The calculations involved in determining the energy required for space heating just outlined are much too long and cumbersome for whole residential and commercial areas. Another method, called the degree- day method, provides satisfactory results for computing the energy re- quired for space heating. This method, referred to sometimes as one of the short-cut methods, consists of comparing a given structure to be estimated with a similar structure, the actual steam requirements of which are known. Assuming that steam usage for buildings of the:same general type of occupancy, e.g., office buildings, and apartments, will be governed by similar over-all factors, which determine heat losses, i.e., inside temperature, 67 and ventilation, and provided adjustment is made for any difference in size and weather conditions, steam requirements for space heating can be determined. The degree—day method of estimating steam requirements utilizes a simplified method for measuring temperature differential and time. The unit of measure is called the degree-day. When the temperature is 65°F (18°C) generally no heat is required for space heating; the experience of heating and air-conditioning engineers.And‘when the mean daily temp- erature falls below 65°F (18°C) heating requirements tend to vary directly in prOportion to the differences between the mean outside temperature and 65°F (18°C). The number of degree-days in a single day is found by subtracting the average of the high and low temperature for that day from a reference temperature, usually 65°F (18°C). For example, if the high for a single day was 40°F (4°C) and the low 20°F (—7°C), the total number of degree days for the day is 35. The number of degree-days in an interval of several days is then found by summation, including only positive values in the sum. The degree-days, as compiled by the weather service for East Lansing, Michigan are shown in Table 5.6. The degree-day method for estimating steam requirements for space heating is expressed by the following formula: S - N X R X D where, S = steam consumption for the estimate period in pounds N - experienced steam requirement; load limits expressing the size of the heating load, such as: (a) 1,000 BTU of calculated hourly heat loss (b) 1,000 cubic feet of heated content (c) square feet of connected equivalent radiation surface 68 R = rate of steam consumption in pounds per degree-day per load unit as expressed by N, usually cubic feet of heated space. D = number of degree-days in the estimate period. TABLE 5.6 Mean Degree-Days in Michigan East Lansing Station January 1302 July 16 February 1147 August 34 March 986 September 138 April 561 October 415 May 288 November 795 June 75 December 1172 Reference: Climate of Michigan by Stations. 1971. Michigan Weather Service, Revised edition. Michigan Department of Agricul- ture. For estimate purposes, in the residential and commercial areas, the degree-day method was used to predict energy use for space heating in terms of pounds of steam. Data from the District Heating Handbook was compiled for the reference area, usually based on Detroit experiences,, along with personal contact with the Board of Water and Light in Lansing, Michigan. The coefficients used are presented in Table 5.7. The "standard house" in the preceeding section can now be estimated using the degree-day method and compared with the results obtained in that section. The month of March in East Lansing has a monthly mean temperature of about 32°F (0°C). The number of degree-days in March from Table 5.6 is about 986. The "standard house" has 15,000 cubic feet of heated space (415 square meters). Using the figure 1.43 pounds of steam per 1,000 cubic feet per degree-day, from Table 5.7, we calculate that in the month of March the average steam requirements for space heating 69 TABLE 5.7 Steam Consumption for Space Heating in Buildings average volume of steam required: pounds per Type of Building heated space (1000 cu. ft.) degree-day per 1000 cu. ft. Office 2160 .685 Bank 806 .786 Department stores 3400 .480 Stores, retail 310 .624 Hotel, motel 1795 .990 Apartment building 1425 1.400 Motion picture 1240 .482 Garage 1540 .202 Factory, small 1350 .808 Hospital 3306 1.830 School 1115 .660 Single-family 20 1.430 Reference: District Heatinngandbook. 1951. National District Heating Association, 3rd edition, page 343. Data is for Detroit, modified for newer insulation standards. Average annual number of degree-days in Central Michigan is about 6950. Climate of Michigan by Stations. 1971. Michigan Depart- ment of Agriculture. Revised edition. would be about 21,150 pounds. Or about 29.37 pounds of steam per hour. Remembering that a pound of steam has about 1,000 BTU (1 X 106 joules), we calculate that the "standard house" needs about 29,370 BTU/hour (8600 watts). From Table 5.5, the "standard house" required 33,242 BTU/hour (9736 watts) calculated by a heat balance method and the difference can 70 be accounted for by the better insulation required of the "standard house" used in the reference area. v.4 Insulation Standards Federal Housing Administration, FHA, minimum property standards of 1965 permitted average heat losses of 2,000 BTU's per thousand cubic feet per degree-day. The "standard house" used in the heat balance estimate of the previous section would require over 41,000 BTU's/hour (12,031 Watts) under these standards. Whereas, from Table 5.5 the "standard house" re- quired a minimum of 1,620 BTU's per thousand cubic feet per degree-day, newer standards have decreased the allowable heat losses considerably since 1965. Since the majority of houses built in the reference area will be constructed after 1976, they should meet the newer standards. These standards, required by the Housing and Urban Development (HUD) Operation Breakthrough of 1970, were 1,500 BTU per 1,000 cubic feet per degree-day. And the latest requirement, set by FHA, sets the property standards at 1,000 BTU per 1,000 cubic feet per degree-day (Berg, 1973). The figure used for the reference area represents a compromise be- tween 1,500 and 1,000. The 1,430 figure reflects the fact that new housing has not generally complied with standards, since in 1972 less than 17 percent of new housing complied with FHA requirements (EPP, 1975). Coefficients used for different buildings in the reference areas, shown in Table 5.7, comply with the newest standards set by FHA, except for the single-family houses as mentioned above. Some commercial buildings are assumed to be well insulated as the coming days of higher energy prices will probably increase the need to lower overhead costs. 71 v.5 Water Heating As part of the national energy picture water heating, in 1968, used almost 4 percent of the total U.S. energy budget (see Table 5.2 in the section, Energy Statistics for the United States). By 1968, saturation levels for water heaters reached almost 95 percent with the growth of electric water heaters leading that of natural gas water heaters. But in spite of this faster growth rate, natural gas water heaters still. outnumber electric water heaters by almost 3 to 1 (EPP, 1975). As more households add dishwashers and automatic washing machines to their list of household equipment, both gas and electric water heaters have increased their per unit consumption of energy (SRI, 1972). The amount of energy used by water heaters increased from about 43 million BTU's (45 billion joules) per year to operate an electric water heater, to 46 million BTU's (48 billion joules) in 1969 (EPP, 1975). Now with the increased use of quick-recovery units this figure is nearer 52 million BTU's (55 billion joules) per year. The average natural gas water heater, in 1971, used almost 32 million BTU's (34 billion joules) per year (EPP, 1975). From an energy convervation standpoint, the general rule that direct burning of fossil-fuel for the production of thermal energy is more conservating than the use of electricity is applicable to the water heater. This rule, however, does not mean that fossil-fuel energy use should not be minimized, because there are many alternative ways to supply thermal energy for water heating. v.6 Demand for Heated Water In terms of personal energy use, water heating accounts for nearly 8 percent of the total, see Table 5.8. 72 TABLE 5.8 Percentage Distribution of Personal Use Energy in the home Space heating Water heating Appliances Cooking Refrigeration All other Transportation Energy - By Use - 1968 Percent 56 32 8 15 3 3 9 44 lieeference: Energy Policy Project of the Ford Foundation. 1975. 'Thg American Energy Consumer. eds. Dorothy K. Newman and Dawn Day. Ford Foundation, Ballinger Publishing Company, Cambridge, Massachusetts: page 34. The amount of heated water used by individuals varies greatly accord- irig to factors such as socio-economic status, and personal habits. In a rsacent study done in Michigan communities, families average around 302 géillons (1,144 liters) of water a day (Field, 1974). Nearly half of the "'titer used or approximately 36 gallons (136 liters) per day per person, was heated . The demand for hot water in the commercial area has been estimated by' the American Society of Heating, Refrigeration, and Air Conditioning E“gineering and is shown in Tables 5.9 and 5.10. These estimates were \flBed to develop the final estimates shown in Table 5.12. Final figures ‘flere arrived at by the use of Miller, et a1, because they were from a flKDre recent study (Miller et a1, 1971). 73 TABLE 5.9 Estimated Hot Water Demand for Various Buildings Hot water required per person per day, Tugpe of Buildipgs ‘gallons per dayJ (liters)' Residential 40 - 80 (152 - 303) Commercial 4 - 6 (15 - 23) Iruiustrial (Factories) 10 (38) Reeferences: ASHRAE Guide and Data Book Applications for 1966-1967. American Society of Heating, Refrigerating, and Air Con- ditioning Engineers, page 255. TABLE 5.10 Maximum Daily Requirements for Hot Water in Office Buildings and Hospitals Egfigggkof Buildings Hot water usage,pgallons (liters) c)ffice Buildings: White-collar worker (per person) 3 - 9 (11 - 34) Other workers (per person) 4 - 9 (15 - 34) Cleaning per 10,000 ft2 36 - 50 (136 - 189) Hospitals (per bed) 125 - 200 (473 - 758) Reference: ASHRAE Guide and Data Book Applications for 1966-1967. American Society of Heating, Refrigerating, and Air Conditioning Engineers, pp. 979-980. 74 TABLE 5.11 Maximum Daily Requirements of Hot Water in Apartments and Private Homes Number Hot water usage, gallons (liters) of Number of Bathrooms 322113 1 2 3 4 1 60 (227) 2 70 (265) 3 80 (303) 4 90 (341) 120 (455) 5 100 (379) 140 (530) 6 120 (455) 160 (606) 200 (758) 7 140 (530) 180 (682) 220 (833) 8 160 (606) 200 (758) 260 (985) 250 (947) Adopted from Reference: Megley, J. W., 1968. Heat Pumps Provide Economi- cal Services for Apartment Tenants. Heating, Pip- ing_and Air Conditioning 40 (1): 124-131. TABLE 5.12 Estimated Hot Water Use Rates Apartments 36* gallons per day per person Shops and Offices 3 gallons per day per employee Hospital 100 gallons per day per bed Hotel 50 gallons per day per room Public schools and Universities 35 gallons per week per student Cleaning 30 gallons per day per 10,000 square feet Reference: Miller, A. J., et a1, 1971. Use of Steam - Electric Power Plant Provide Thermal Energygto Urban Areas. ORNL-HUD-14, Reactor Technology, Oak Ridge National Laboratory, page 151. Anne Field. 1974. Household Water Consumption, Research Report 249, Agricultural Experiment Station, East Lansing, Michigan. Hot difficult estimated crease hc Table 5.] dw indix future hc v.7 Ste; EstJ' a known ( per unit rule of t averaged 0f water Steam is (60°C); . (DHH. 19 Insx better a baat 10$. The follow] where, S C 75 Hot water requirements for apartments and homes can present a more difficult problem because other factors can play a part in the final estimated demand. Table 5.11 shows how the number of bathrooms can in— crease hot water use. The figure for apartment hot water use, shown in Table 5.12, represents the best judgment, given the unknown character of the individuals living in the reference area, tempered with a guess for future hot water use. V.7 Steam Demand for Water Heating Estimated steam requirements for water heating can be figured from a known quantity of hot water per unit of time and approximate steam per unit time needed to heat a gallon of water in a water heater. The rule of thumb used was to assume a ground water temperature of 40°F (4°C) averaged for the year, and since it takes 100 BTU's to raise one pound of water from 40°F (4°C) to 140°F (60°C) in a water heater, one pound of steam is capable of raising 10 pounds of water from 40°F (4°C) to 140°F (60°C); assuming one pound of steam has about 1,000 BTU's (1,054 k joules) (DHH, 1951). Insulation of water heaters is assumed to be orders of magnitude better than current standards as a result of higher fuel prices, and heat loss from water heaters used in the reference areas is negotiable. The amount of steam used for water heating is found by using the following formula: S - G X C X R where, S = steam required, pounds per unit time (day, week, month) C) II hot water demanded, gallons C a constant, 8.3 pounds per gallon R = ratio constant, 1/10 76 Table 5.12 contains the estimated hot water demand for per unit of time, G, used to estimate steam requirements for apartments, schools, and commercial establishments. v.8 Air Conditioning Several methods have been developed for determining the energy require- ments of air—conditioning systems. Most are like the methods outlined in the section on space heating. Hourly weather bureau data are useful for determining the hours of operation based on say, a temperature of 70°F (18°C). Also, cooling-degree hours above a fixed temperature, say 80°F (29°C) is another criterion. When the cooling—degree hours are available, they can be used to determine cooling requirements, and the energy needed similar to the method described in the section on the degree-day method. Cooling degree-days for Michigan are shown in Table 5.13. Many of the factors outlined in the section on space heating also apply to air conditioning. But, as internal environments of buildings have changed in the last decade, the internal environment has become al- most totally separated from the external environment. Increased lightly, more office equipment, computers that require special environments, and controlled climate air flow systems have all combined to increase energy demands for air conditioning beyond the needs measured by climatic vari- ables. Methods used to determine air conditioning needs, like the cool- ing degree day method, and the modified cooling-degree day method have been replaced by cooling load check figures. Refrigeration for applica- tions in specific classifications are shown in Table 5.14. All of the previously mentioned methods except the cooling—load check figure, will probably underestimate the requirements for air condi- tioning since the practice in residential and commercial sectors has been to leave air conditioners on 24 hours a day. Even though the energy crisis MHQEhOZ mka UUMMQQ WCHHOOU H03CC< DEN fiHSuCOX NH on mmflmmd‘fi 77 .mawaoumu nuuoz .oHHH>mnm< .uMuaou oaumafiau Ho:o«umz .uow>umm mama Housmaaoua>am .cowumuuounwau< uwuunamoau< van vasomoo Hmaoaumz .ohma u qua «man mounds was .moumfifioo mo ucmauumamn .m .D .mnma uHoou can wcfiumom mam dmowumuwmwouum «unaumummams mo mamahoz thucoz ”ouauuuwom NoH o 0 ac ow mm OH nouamuoumz ooo m um mma NNN mca we muu>fim dough own a «n mwa omH MOH mm ao>mm suaom «QN m o moH om om n cowucouno own 5 mm mud OHN mHH MN panama: mmm o «m com mad Haa om wawoama com o nu and woa on ma upon men OH no mNN ~oN moa mm vacuum: mac 0H me mad emu omH an muwo zom 005 w on com mom «ma HQ wonu< cq< Hmo 0 mm com mmw oca om cmaup< amaaq< Av m < n n z acaumum mH.n mAman acceptable level without raising the installation costs too high. Heat loss from steam pipes is dependent upon the specific heat of the steam, its density, flow rate, pipe diameter, the heat transfer co- efficientcfi'the insulation material, and ground temperature. Figure 6a28hows the relationship between conductivity of insulation material and mean temperature. And Figure 6.3 shows heat loss as a function of temperature and pipe diameter. In addition to heat loss, economic thickness of insulation based on fued.cost, cost of capital, and maintenance must also be considered. 86‘ N" 10 E (69) U) z 0 E 8.5 2 (59) 25 :1: :“z’ 7 H (48) m n: < D o r U) J a: (34) in] 94 8 3 S (21) CL. 5 2 Q. g (14) Q g .01 g (.07) m 6 8 10 12 14 16 18 (15) (20) (25) (30) (35) (40) (45) PIPE DIAMETER IN INCHES (CM) Figure 6.1 Pressure Drop per 1,000 Feet of Pipe for Various Pipe Diameters. Assumes super heated steam at 50 psia and 10,000 lbs/hour flow. MEAN TEMPERATURE, F 100 200 300 400 500 600 700 CONDUCTIVITY BTU IN. PER sq FT PER °F PER HR Figure 6.2 Conductivity of Insulation Material Reference: Insulation Systems. 1976. Johns-Manville, Report on Hydrous Calcium Silicate. Denver, Colorado. (MEGAWATTS) HEAT LOSS PER MILE MBTU/HR. Reference: 87 (1.17) 0 10 20 30 40 50 60 (25) (50) (76) (101) (126) (151) PIPE DIAMETER INCHES (CM.) Figure 6.3 Heat Loss from a Single Buried Pipe. Miller, A. J., et a1. 1971. Use of Steam-Electric Power Plants to Provide Thermal Energy_to Urban Areas, Report No. OFNL—HUD-l4, Reactor Technology. Oak Ridge National Labora— tory, page 142. 88 Figure 6.4 shows the relationship between cost factors and lost heat COSC. lost heat cost ~—‘ c 9 c9 05 minimum cost 06° 2% v S l :1 ma 4 I no >1 0: l [1.] a. e‘ 8 t l t) c°9 I ’10“ t 033 I INSULATION THICKNESS Figure 6.4 Cost Factors of Insulation Material To get an estimate on the thickness of insulation, we have chosen to use the hydrous calcium silicate pipe insulation. This should give "ball-park" estimates on the cost of insulation based on recommended thicknesses by the insulation manufacturers. The recommended thickness are shown in Table 6.1. VI.4 Installation Costs The underground steam pipe distribution system used in all the reference areas were designed with the following assumptions: 1) the pipes are schedule 40 since the design is for a low-pressure system buried 6 feet (1.8 meters) below ground surface. Nominal Pipe Size Inches (cmh)_ 2.00 2.50 3.00 4.00 6.00 7.00 8.00 9.00 10.00 12.00 14.00 16.00 18.00 20.00 24.00 30.00 36.00 (5.04) (6.30) (7.56) (10.08) (15.12) (17.64) (20.16) (22.68) (25.20) (30.24) (35.28) (40.32) (45.36) (50.40) (60.48) (75.60) (90.72) 100 (38) to 1.924131 1.5 (3.8) 1. l. 5 5 (3. (3. (3. (5. (5. (5. (5. (5. (6. (6. (6. (6. (6. (5 (5. (5. a Recommended thickness installation, cost of Reference: 8) 3) 8) 0) 0) 0) 0) 0) 3) 3) 3) 3) 3) .0) 0) 0) 89 TABLE 6.1 200 (93) to 299 (148) 2 2. .0 5 (5. (6. (6. (7. (8. (8. (8. (10.1) (10.1) (10.1) (10.1) (10.1) (10.1) (10.1) (8.8) (8.8) (7.6) 300 3.0 3.0 3.5 4.0 4.5 4.5 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 4.5 4.0 Recommended Thickness* TEMPERATURE °F (°C) (149) to 399 $204) (7.6) (7.6) (8.8) (10.1) (11.3) (11.3). (12.6) (12.6) (12.6) (12.6) (12.6) (12.6) (12.6) (12.6) (12.6) (11.3) (10.1) 400 (204) to 499 (260) 3.5 4.0 4.5 Ln 0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 5.5 5.0 (8.8) (10.1) (11.3) (12.6) (12.6) (13.9) (13.9) (15.1) (15.1) (15.1) (15.1) (15.1) (15.1) (15.1) (15.1) (13.9) (12.6) 500 (260) to 699 (371) 4.5 (11.3) 5 S. .0 0 (12 (12. (13. (16. (16. (17. (17. (18. (17. (17 (l7. (17 (17 (17. (16. (15. .6) 6) 9) 4) 4) 6) 6) 9) 6) .6) 6) .6) .6) 6) 4) 1) includes cost considerations associated with heat loss, money, Insulation Systems. Calcium Silicate, Johns-Manville. etc. 1976. Johns Manville, Report on Hydrous Denver, Colorado. 90 2) design pressures are in the range of 5 to 150 psi (34 to 1034 kilo- newtons/m2). 3) supply lines temperature of 400°F (204°C) 4) return condensate at 1500 to 200°F (66°C to 93°C) used in all ref- erence areas. 5) installation cost based on digging in dirt and not through road surfaces. Costs estimates were developed from Miller et 31, information from Boston Edison Company, Consolidated Edison Company of New York, and Detroit Edison Company. To getzipicture of the costs involved, in 1967 in downtown Boston, 24-inch steam pipe was installed at $210 per linear foot. Outside the downtown area l6-inch steam pipe cost $120 per linear foot to install. An estimate of $180 per linear foot for installation of 8-inch pipe in an unspecified location in New York and $150 per linear foot in Detroit indicates the high cost of installing pipe in an exist- ing city. These costs are almost the same as the costs of installing complete tunnel systems, per linear foot, in a newly expanded part of the steam system at the University of Virginia. It may be seen from the above data that the installed cost of under- ground piping in an existing city is sensitive to specific interferences with other underground utilities. In contrast, the cost of underground piping of "new cities" can be estimated as a function of pipe sizes, meter sizes, etc., and information regarding the nature of the earth to be trenched. Two different "new city" installed underground piping systems are examined by this study. One is the "regular" buried steam pipe system and the other is a modified tunnel system. 91 The desirability of tunnels for steam distribtuion systems is obvi- ous. Ease of access to all pipes, joints, valves, expansion joints, and supports makes operation and maintenance of these facilities highly sat- isfactory. Another important aspect of this system is longevity and reliability; less elaborate jackets can be installed initially, very little mechanical damage of insulation is experienced, and dry surfaces minimizes corrosion. Whereas trenched piping systems, like the one men- tioned previously, problems of water damage, unknown motion and stresses caused by start-up, and shut-down temperature changes, and protection against ground elements, increase operation and maintenance costs. The tunnel system is examined because it has possibilities of lower maintenance cost and because the community with a tunnel system would have a certain aesthetic appeal. Underground tunnels could provide space for all services; natural gas, telephone and electric cables, etc., thus removing over-hanging utilities from the community. If the dual-purpose plant technology was adopted by the community, then the other services using the underground tunnels could help make the system economical by paying for the right-of-way. All services using the tunnels would enjoy decreased maintenance costs, which they could pass along to pay for the system. Cost of underground tunnels used in the reference areas are cost accounted to the steam function part of the dual-purpose plant. No discount is included as revenue from other services using the under- ground tunnels. The "standard" buried steam pipe systemrwasdesigned with insulation as shown in Table 6.1, surrounded by about 5 inches (12.6 cm.) of con- crete, according to pipe diameter. The thermal conductivity of the 92 insulation is .44 BTU/hr-ftZ-OF per inch of insulation (0.3 watts/mZ-OC per cm.) at about 300°F (149°C). Return condensate lines are buried without insulation in the concrete conduit and are designed to accommo- date maximum flow periods. The network of modified tunnels originates at the power plant. They are routed through major building centers in the commercial area and through as main steam lines in other cases. Inside diameters are 66 in- ches, 60 inches, and 54 inches (1.7 m, 1.5 m, and 1.4 m). They are a modified walk-through tunnel made of pre-cast concrete which are less ex- pensive then the costly walk-through tunnels. TABLE 6.2 Estimated Cost of Installed Buried Steam Lines Pipe Diameter of Cost in Dollars per Main or Supply Linear Foot ($/m) 2" (5 cm.) $ 54.41 (178.52) 4" (10 cm.) 56.45 (185.21) 6" (15 cm.) 84.50 (277.24) 8" (20 cm.) 90.69 (297.55) 10" (25 cm.) 104.44 (342.67) 12" (30 cm.) 130.93 (429.58) 14" (35 cm.) 190.38 (624.64) 16" (40 cm.) 221.17 (725.66) 18" (45 cm.) 237.15 (778.09) 20" (50 cm.) 270.39 (887.15) 24" (60 cm.) 315.92 (1,036.53) 30" (76 cm.) 402.68 (1,321.19) 36" (91 cm.) 496.69 (1,629.64) ‘2' .E l 93 Cost estimates for "regular" buried steam lines are shown in Table 6.2 All costs include concrete conduit, main or supply steam line, return condensate line, expansion joints, insulation, valves, and labor costs based on trenching in dirt. Miller et a1 estimated the cost for a similar system in 1969. An 8 inch (20 cm.) pipe, return, concrete conduit, etc., cost $57 per linear foot. Costs estimated in this study are nearly 60 percent higher. Estimated costs of installing tunnels are shown in Table 6.3 Again, all costs are included — insulation, return condensate lines, anchors, expansion joints, and labor. ‘TABLE 6.3 Estimated Tunnel Cost* Pipe Diameter of Cost in Dollars per Main or Supply Linear Fobt ($/m) 4" (10 cm.) 213.90 (701.81) 6" (15 cm.) 232.50 (762.83) 8" (20 cm.) 251.10 (823.86) 10" (25 cm.) 279.00 (915.40) 12" (30 cm.) 297.00 (974.46) 16" (40 cm.) 325.50 (1,067.97) 20" (50 cm.) 390.60 (1,281.56) 24" (60 cm.) 427.80 (1,403.61) 30" (76 cm.) 502.20 (1,647.72) * estimates were inflated to 1976 dollars. Reference: University Heating and Utilities Committee Report. 1968. Proceedings of the National District Heating Association. District Heating Association, Pittsburgh, Pennsylvania. 94 TABLE 6.4 Meter Cost Meter, Capacity in Pounds Gravity Type - Dollars per Hour 3 273.00 250 316.00 500 401.00 750 524.00 1500 841.00 3000 1053.00 6500 1246.00 12,000 Reference: The Cadillac Condensate Meter. 1976. Cadillac Meter Division Central Station Steam Company, Detroit, Michigan. Meters are installed at each steam energy user. The costs for metersare shown in Table 6.4 V1.5 Steam Losses from an Operating System Since it is impractical to determine an average value of the manu- facturer's rated heat loss for all the different sizes and lengths of steam lines involved, the National District Heating Association recom- ments using a method which represents steam loss from an operating system (DHH, 1951). This approach includes the theoretical heat loss estimates tempered by actual operating experience of district heating systems. It includes pin hole leaks, outages and other contingencies experienced dur- ing full-year operation of steam lines. Winter steam losses are in the range of .04 to .06 pounds of steam per hour per square feet of surface area (126 to 189 W per square meter of surface area) and summer losses are.O4 pounds of steam per hour per square feet of surface area, shown 95 in Figure 6.5. These figures were used to estimate the steam losses in the steam distribution systems used in the reference areas. .06‘r winter condition steam losses .OS‘P’ ,’:’A a ,’ 1. ” ..’ summer conditions 0044’ D (heat loss according to manufac- turer's laboratory tests POUNDS 0F STEAM PER HOUR PER SQUARE FEET OF PIPE SURFACE J 1 1 1‘1 1 Y 150 160 170 180 190 200 TEMPERATURE DIFFERENCE BETWEEN INSIDE PIPE AND GROUND Figure 6.5 Steam Losses From Operating Steam Distribution System. Reference: District Heating Handbook. 1951. National District Heat- ing Association. Pittsburgh, Pennsylvania. 96 V1.6 Summary Steam transport from the power plant and distribution within a given community is dependent upon the steam requirements and spatial organiza- tion of steam users. Providing adequate flows and pressures requires analysis of pressure drop and steam losses during operation of the system. Usually pressure drop in reasonably well selected pipes is minimal, except for very long pipe lengths. Steam losses during operation range between 10 and 15 percent of total output, and is considered a cost of operation. Even with economically sound choices for insulation, taking into consideration fuel costs, capital investment, maintenance, etc., increasing insulation thickness increases the cost of the system without any real decrease in steam losses during operation. Two alternative systems have been presented. The costs associated with both indicate that distributing steam from the power plant to steam users is very expensive. And at larger pipe diameters, the "standard" buried pipe and tunnels system are equally costly. The difficult design problem is then to use as many small diameter pipes as possible with the shortest distance between the power plant and the steam users. CHAPTER VII REFERENCE AREAS The purpose of incorporating the reference areas is to demonstrate the feasibility of the dual-purpose power plant. The design of the areas is conceptual and provides enough information to test the system as a whole unit. Residential and commercial areas used are more like planned expansion to existing cities than totally new cities per se, since pro- viding steam to an existing city is very problematic. Rights-ofdway, other services buried in the street, etc. make retrofitting older cities costly. The reference area presents a good choice to test the system because it is realistic in the demand for steam and provides baseline data with which more complex examples can be approached. VII.1 Physical Layout of the Reference Areas Buildings in the residential and commercial areas were developed from general characteristics of the Michigan area and with consideration for energy conservation. Location of buildings as well as increased in— sulation standards were used to help minimize energy requirements. Also, the central commercial area was designed with many establishments within a collected area to minimize travel to work, home, and recreation. The characteristics and number of commercial services in the reference area reflect the Michigan per capita average for cities of 20,000 or more population. The only simplification imposed was the use of uniform residential and commercial blocks and repetitive square-mile layouts. 97 98 660'(201m) l I <%~ 600'(183m) ‘I7I l 600' 660' Figure 7.1 Eight Apartment Buildings per Block, Two Stories, Each Building 55' X 175' (17m X 53m). This was done to facilitate changing the parameters of population, dis- tance from the power plant, and population density. The physical layout of the multi-family dwellings (apartment complex) is shown in Figure 7.1. Each apartment has 1200 ft.2 (lllmz) of usable space or enough room for about 4 people. Apartment buildings are two stories tall with eight apartments per floor. The arrangement of apart- ments on a residential square mile is shown in Figure 7.2 along with open areas, shopping areas and schools. Schools were sized to provide facili- ties for the population within the residential square mile. The resulting population density is 16,500 people per square mile (259 hectares). Enlarg- ing the apartments to three stories does not change the physical layoutcif 99 mmaaaamsa sfiaswmuauflaz u «Ha: «annum Hmauawvaaam Hmuaame ~.e gunman a. d < m < .< 4 Hooaum Hoozom muuuauauam manuauaoam < 4 AB ooe.av IIIIIJ, Hoonom Hoonom .om~.n swam «Head: d < ['1 , Hoonum doosom muoucuau~u annuaoauam < < ,c m ¢ < A a wm~.Hv «uoou on~.o~ ouaoauuudo MNE cm~.mv Nuoou ooo.coc.~ monoum Aaa mmH.ocv Nuuau con.~so .Hoonum qua: can oases: Ana cease Nuouw onh.~H adoosue annuauadam manna woody voooaoso «Hanan: uoz 100 the shopping, recreation areas or the steam distribution system. The only change is to raise the population density to about 25,000 people per square mile (259 hectares) and increase the steam demand. The main commercial area has a shopping mall with surrounding office buildings, commercial establishments and a hospital. The ser- vices were sized according to the average needs of Michigan residents for a population total of about 20,000. The physical layout of the central commercial area is shown in Figure 7.3. Extrapolation to large populations is accomplished by repeating square mile blocks, shown above, to create the desired total population level. Increasing population density can be accomplished by raising the height of apartment buildings or decreasing the available space per person from 300 ft.2 (28m2) to a minimum of 200 ft.2 (l9m2) per person. Within reasonable limits these variations do not change the physical layout of the square mile reference areas or the steam dis- tribution system. Although using a "typical" single-family dwelling will probably raise some eyebrows, the necessity of considering an area with only single-family homes was considered more important than trying to find the right "typical" home. The parameters of the single-family dwell- ings are shown in Table 7.1. They were taken from the Bureau of Census Data for the Northeast region (TES, 1972). The physical layout of the single—family dwellings is shown in Figure 7.4. Each block has 20 houses, each house on a lot 135' x 60' (41m x 18m). There are 128 blocks in the square mile for a total of 2,560 houses. The population is about 10,240 people per square mile. 101 mop< Hmwopmseou m.n mpswam m a No No No am m m a No No Hm ~o Mo mm m ao mm mm mm < Ho m < sooaa you “as oa~.mv ~.uu ooo.ooo.a «was aumoauam .aowummuumuuuaoaomsam Amoumuomn oav .oouuo on unopouxuma amuOu Ame www.cv ~.uu ooo.om .mvoa nu .Hmuunmo; xuoHa use Awe om~.av ~.um ooo.ooo.a .mmuauoan aouuoa .mucmusoumou owumfl .mouOum voow .oumm nonabfi kuou Ame mam.~mV ~.um ooo.omm Hams wawaaoam xuoaa awn Ame oo~.av ~.uu ooo.ooo.a .moHSuoaa cofiuoa .momaosoums .mucoszmaanmumo mammoaons .mmwmumw .mwmamov ouam xooan you Ame cm~.N~V ~.uw ooo.oq~ .mooauuo mugs .Hmumvmu .mxcmn .mwcwvaaan mowwmo H o venom manna: uoz House floor area House style House construction exterior wall construction surface sheathing insulation inside ceiling insulation basement type attic window area window type storm windows door area (3 doors) door type storm door area patio door window covering external landscaping house facing external colors roof construction heating system cooling system garage (enclosed) people 102 TABLE 7.1 Housing Parameters 1500 square feet two-story wood frame wood shiplap 1/2" insulation board R-7 batting 1/2" dry wall 5" blown-in full (unfinished) ventilated - unheated 122 of floor area A1 casement none 60 £c.2 wood panel with 1/2" ft.2 of glass pane 40 ft.2 40 ft.2 (single pane) 702 draped 202 shaded 102 Open no awnings no shading effect north white roof and walls asphalt shingle forced hot-air, natural gas central-electric attached, slab, unheated 2 adults, 2 children Reference: Total Energy Systems, Urban Energy Systems, Residential Energy Consumption, 1972. Federal Council on Science and Technology. Department of Housing and Urban Development, page 275. 103 mwcHHHm3Q xafiEmwnmamch mo usoxmg Hmowmmnm «.5 ouswwm ABwHV AJOG IV Aaaav .mma AN - _ 28$ .80 L4 w” ES: .08 w— _ _ 104 VII.2 Steam Consumption in Reference Areas Energy in the form of low—pressure steam is used in the reference areas for space heating and cooling, and water heating. Steam demand for the single-family dwelling reference area reflects the use of steam for only space heating and water heating. Estimated steam demand was determined by the methods outlined in Chapter V. The total annual demand for steam is shown in Table 7.2. TABLE 7.2 Total Annual Steam Demand (Pounds of steam X106) air space heating water heating conditioning multi—family dwellings 597.559 249.372 249.718 (apartments) schools 31.316 6.824 99.760 (used year round) commercial area in 6.651 .180 13.362 multi-family dwelling area commercial area 181.396 28.308 339.793 single-family dwellings 380.485 152.986 - - - - Estimated steam demand was figured on a monthly basis to find maxi- mum and minimum demand periods. The resulting figures for each reference area are shown in Figures 7.5, 7.6 and 7.7. From these graphs, it is clear that without using steam for air conditioning, there is a burden on opera— tion in the single-familv dwellings reference area. The single—family- dwellings demand for steam drops nearly 85 percent from maximum demand to minimum demand, remaining at minimum demand for almost four months. 105 10 90 . Steam pounds X10 J F M A M J J A S O N D Month Figure 7.5 Estimated Monthly Steam Demand Single-Family Dwellings 100 Steam pounds X10 l 1 a l L L4 J J A S 0 N D g . '11} xii >., 3n» Month Figure 7.6 Estimated Monthly Steam Demand Commercial Area 106 150 ' 140 F 130 ’ Steam 120 . pounds 110 * X10 100 ' 90 f 80 . l 1 1 L 1 1 L a J 1 1 J J F M A M J J A S 0 N D Month Figure 7.7 Estimated Monthly Steam Demand Multi-Family Dwellings Steam demand in the commercial area is completely dominated by the use of air-conditioners. As seen in Figure 7.6 during the months of summer, steam demand reaches a maximum. The separate affects of single-family dwellings and the commercial areas's steam demand for air-conditioning come together in the multi- family dwellings reference area. Steam demand is similar to the single- family dwellings until summer, when the use of air-conditioning increases. Optimal operation of any system supplying steam would be charac- terized by almost constant output all year. This might be accomplished if the right mix of single-family-dwellings, commercial establishments, multi-family-dwellings, and industry were located in the community. VII.3 Summary The reference areas used to test the dual-purpose power plant have been presented. They are urban communities which show different time demands for steam. Taken together they show that a more diverse com- munity, in terms of residential, commercial, and industrial sectors has 107 a better chance of providing the environment where the dual-purpose plant might work economically. Later we will consider the economics involved in operating a dual-purpose power plant serving these urban reference areas, singularly and in combination. CHAPTER VIII DESCRIPTION OF THE MODEL In preceding chapters we have examined the use of energy in the United States as it relates to urban communities, and developed methods for estimating energy use in the residential and commercial sectors. Later reference areas were designed and estimates were made of the energy required by various communities. The purpose being, to put forth the tools necessary for examining other complex communities and to provide test cases for the dual-purpose plant as a system. Now that we have energy requirements for various communities with known structural and population characteristics, we now turn directly to considerations of the dual-purpose power plant. To describe the whole system, i.e., the dual-purpose plant with known steam demands from chosen communities, a simulation model of the dual-purpose plant has been developed. This chapter presents the economic and energy relation- ships of the components of the model and the assumptions incorporated in its development. VIII.1 Methodology In order to develop a model of any system, it is important that some theory or theories of behavior exist to explain the interaction be- tween the variables of the model. Since it is the logical structure of the model and the theory used to describe the behavior of its components which finally determines the behavior of the model, the resulting model 108 109 is only as good as the theory used. And the theory only as good as its ability to explain real world behavior. For example, one might assume that the technologies used by society for the extraction, refining, transport, and utilization of energy resources is fixed, and from an input/output model find the necessary amounts of energy required to produce a given output level of goods and services. The results of this input/output model would be only as good as the assumption of fixed technologies. Any complex model constructed necessarily forces the modeler to make judgments and simplications. Models are simplified to keep them within manageable bounds and as a result, the final decision on the value of the modeling effort is usually mixed. Some parts are good and accurate and other parts are not so accurate. But if it is realized that a model is just one step in the long attempt to understand which theories best describe the behavior of real world systems, then it is easier to take the modeling exercise with no reservations about its applicability. The first step in the modeling sequence is to formulate the ques- tion, "What behavior do I want the model to explain?" Without first defining this question, modeling can be a very long exercise in bound- less futulity. Armed with the answer to this question, one can begin to use or discard variables and relationships between variables, keep- ing the ones that appear to be important for describing the behavior of the system and discarding the ones with no significance. The ability to know which variables and relationships are most significant and which are not so important is dependent upon knowledge of the system. The 110 greater the knowledge, the easier the modeler's task. Without knowledge about the determinants of behavior, the modeler must make more decisions. Without a clear cut alternative, sometimes the modeler must take an assumption and then later try to validate or destroy that assumption. The final test comes when the model is used to describe the behavior of the real system within the limits of the original assumptions. The objective of the model developed in this study is to test the feasibility of using small dual-purpose electric power plants to supply low-pressure steam to urban communities. In order to do this, the model must describe the dynamics of a dual-purpose power plant and the effects of changing steam demands on electric energy production. The basic theory used to describe the behavior of the system is taken from thermo- dynamics. And any simplifying assumptions used in the model are done so as a result of experience gained by practitioners of the technology under consideration. To test the feasibility of the model, different cases, using reference areas developed previously, are examined. The energy flows between the components of the model are handled as an energy balance, or an accounting scheme. The development of any model of a complex system is an iterative process of construction, simulation, evaluation, modification, construc- tion, simulation, evaluation, modification, etc. With each iteration, the modeler gains new insight into the behavior of the system and, hope- fully, a better model emerges. The model presented here describes the results of this process to analyze the dynamics of a dual-purpose power plant supplying steam to small urban communities and the associated eco- nomics involved. electric energy output _______________________________ .. I l I demand | for team I transport losses I steam steam | | I return condensate I I l | l I system boundary | L____A<_ _______________________ .1 Figure 8.1 General Structure of the Energy Flow System. VIII.2 Model Boundaries The purpose of the model is to test the feasibility of using steam extracted from the heat cycles used to produce electricity in an elec- tric power plant for low-temperature energy tasks in an adjacent com— munity. Therefore, the model must contain the interactions between the demand for energy in the community and the power plant. The test of feasibility is a problem of supplying adequate quantities of steam to a given community at reasonable prices for both steam and electricity. Figure 8.1 depicts important components of the system. Shown are the flows of energy, steam and electric, and demand for steam. The model uses an energy balancing scheme to account for all energy flows within the system. 112 The boundary of the energy flow and demand system can be easily drawn, since steam demand, as seen by the power plant, includes losses in transport and the demand for steam in the community. Although many individual factors come together to determine the final community de- mand, a systematic way is available to estimate this demand as shown previously in Chapter V. For the energy demand system then, the com- plex interactions with the community and the transport component come together to represent an input to the power plant. The power plant component is a converter of fuel into steam and electric energy. Fuel is an exogenous input variable and electric energy is an endogenous output variable. Since the power plant operates as a baseload plant, electric energy output is a function of steam demand and not related to the demand for electric energy in the com- munity served by the steam system. VIII.3 Aggragation Level Steam demand was estimated on a monthly basis and, therefore, the models' results are characteristic of an average year. The method used to find the demand is a function of average fluctuations about 65°F (18°C) and not directly responsive to exogenous temperature changes. Therefore, the simulation model cannot be used to predict costs and energy output during long hot summers, every cold winter, etc., without recalculating total aggragate steam demand. Aggragated hourly steam demand is a function of average space heat- + X + X . l 2 3 2 decreases by q, the model behaves the same. ing and cooling, and water heating demand, such that Y = X If X1 increases by q, and X That is, the model cannot be used to directly identify perturbing 113 events in the demand component, whether they are behavioral changes in the way people use energy or exogenous events like extremmetemperatures. Geographical considerations are considered explicitly in the development of materials used in the transport and distribution of steam, and in the type of communities used to test the system. Although thernices for fuels and the cost of construction are not geographically particular to Michigan, they are escalated to cover a range of different capital and Operating costs to test sensitivity under other cost's situations. VIII.4 Pressure Drop Program Before we get into a detailed description of the energy flow and feasibility model of the dual-purpose plant, an important part of the steam transport and distribution system will be considered. Three preceding sections on water heating, space heating, and air conditioning detailed procedures for estimating steam requirements of low-temperature energy tasks for a variety of buildings. The purpose being, to provide the necessary tools for estimating steam requirements for any community design, population density, and living style. Once these steam estimated have been made, the next set of questions, i.e., distance trade-offs to the power plant, can the system operate economi- cally, etc., are provided answers through operation of the model. The distribution system in any community is a critical factor in the feasibility analysis. Because the direct cost of installing steam pipes, condensate return lines, meters, etc., can be very high, it is important that the designer consider alternatives based on accurate information. For this reason, a program was developed to determine pipe parameters for each section of steam line used in the reference areas. 114 Pressure drop within the underground steam pipe system must be handled such that the end-most user is provided with a minimum required pressure. For example, in the multiple-family dwellings and the com- mercial area the minimum pressure is constrained by air conditioners - 20 psi (138 kLnewtons/mz). Whereas in the single-family dwelling area minimum pressure is not constrained by air conditioners and pressure can drop to 5 psi (34 lanewtons/mz). Pressure drop in a given length of pipe is a function of the flow rate, steam density, pressure at the sending end of the pipe, and the inside diameter of the pipe. Several formulas have been developed for use in calculating the size of steam pipes to accommodate specified rates of flow. An Urwin chart is a direct and simple method for. determining flow rates and pressure drop (DHH, 1951). Another method is to use the Urwin formula directly, providing more accurate results. The mathematical description, the Urwin formula, for pressure drop is given by the following equation: Q . 0.0001306 $1.41 + 3.6/D) r 05 where, Q - pressure drop, pounds per square inch w - steam flow, pounds per minute L - length of pipe, feet Y 8 average density of the steam, pounds per cubic feet D - diameter of the pipe, inches The Urwin formula is used to calculate the drop in pressure for each length of pipe in the steam distribution system. The calculated pressure drop is used to determine the pressure in the sending and of the next section of pipe. And this process is repeated along the sec- tions of pipe to the last or farthest steam user. 115 An iterative program has been developed to find the pressure through the system, given pipe diameters, initial pressure, a minimum pressure, and pipe lengths. A description of this program and the in- formation aspects for its use arewhat follows. The flow chart of the program is shown in Figure 8.2. The set of steam flows and pipe length are determined by the community being con- sidered, where the spatial arrangement of the community determines the length of pipes needed to connect steam users into the distribution system. The lengths of pipe are inputted as B(KK) where, B(l) = first length of pipe, feet B(2) = second length of pipe, feet B(N) = Nth length of pipe, feet B(l) is generally the first steam line in the community nearest the plant, and the B(N)th section serves the farthest steam user from the plant. Itshould be noted that the Urwin equation can give pressure drops from 10 to 20 percent above actual if extremely high velocities are used. The Urwin chart is useful here for checking the range of flows in the system and recognizing when the results are overestimated. The steam demand for each steam user in the community is known via the information presented in Chapter V. The estimated maximum steam demand, in pounds per hour, is converted to the units of pounds per minute. With the sum of the expected maximum demand for all users in the community used to derive the initial steam flow into the circuit. Initial flow required by the total system is reduced by the demand for steam by each user, and steam flow to the first steam user is subtracted 116 ——-— FUR) .3000 Initialize P(1), D(KK), M N - 1 Z I .0001306 Find R from KP(IN) for 1’00 density R for P(N) I c-z*r(u)2 * B(N * (l+3.6/D(N) Q(N)-C/R*D(N)5 (N+l) ' P004201} Table of KP(IN) and B(IN) No N - N‘+ 1 No last B(N) Yes 7 No Run over "Yes Heat loss cal- rculations Figure 8.2 Flow Chart of Pressure Drop Program 117 from the initial flow F(l) to find F(2) for the next section, and F(2) is reduced by the flow to the second user to find F(3), etc. F(l) 8 initial steam flow, pounds per minute F(2) - steam flow in the steam line after the first steam user in the circuit is supplied, pounds per minute F(N) = steam flow in the last pipe section supplying the steam user farthest from the plant, pounds per minute. The initial pressure P(l), the pressure at the sending and of the first section of pipe, is selected by the designer. Knowledge of the possible pressures available from the plant and the minimum pressures required by the steam users in the community guide this decision. For example, in this study the multiple-family dwellings and the commercial area, minimum pressure is constrainted by air conditioners, about 20 psi (138 K newtons/m2). Whereas, in the single-family dwelling reference area minimum pressure can be as low as 5 psi (34 K newtons/m2). The minimum pressure M is initialized in setting up the program and is used to find that section of pipe where the pressure was too low. This is done by comparing the derived pressure for each section with M. Where the steam pressure P(J) in any steam pipe section is found by suc- cessive reductions of the initial pressure P(l) by the calculated pressure drop in each section preceeding P(J). If the pressure in any section is less than or equal to M, then a new higher initial pressure P(l) is read in, and the series of pressures and pressure drops are re-calculated around the circuit. Or the same initial pressure is used with a new set of pipe diameters, and the pressure and pressure drops are re-calculated for the system. Figure 8.3 shows the flow, F(KK), and the pipe lengths, B(KK), needed to use the program for the multiple-family dwellings reference 118 9(1) -__,__ __________________________ _“V r (1) () I 1*. B F l or L 1 I <— l B(2) F(2) F(28) B(28) - I l 1, 3(3) F(3) ' 27 YB 27 ‘ |F< ) < > 3(4) m) 'F(26) B(26) I‘?--‘ 1%.... I B 5 F 5 lp<25> 13(25) 6 ( ) < > I B 6 F 6 | < >' < ) F(24) B(24) I is) ‘4 3(7) F(7) IF(23) B(23) 3(8) F(8) | test the economic feasibility of the system. As outlined in Chapter IV, the amount of energy extracted as steam for use in the community affects the production of electricity. This "stealing" of electric power is shown schematically in Figure 8.11. As steam demand increases, the production of steam must be increased accord- ingly. Resulting in a decrease in the production of electricity. Be— cause the energy in steam is used to turn the turbine-generator, extract- ing more steam reduces the amount of steam passing through the last blading stages of the turbine, reducing the power output. In like fashion, increasing the amount of steam reaching the last stages of the turbine, in- creasing the power output, necessarily requires that less steam be l 30 Steam Electricity Demand demand + + Steam - Elecricity Production _ Production Figure 8.11 Causal Loop Model of the Dual-Purpose Plant System extracted. This can be done by shutting down the extraction valve at the partition between stages of the turbine. Steam at high enthalpy levels, higher energy per pound, has the ability to produce shaft work and electric power. At lower enthalpy levels steam has not practical ability to produce shaft work. In order to keep the efficiency of electric energy production at its highest level, steam should be extracted at the lowest possible enthalpy levels. In addition, if we choose to price extracted steam according to its ability to produce electric energy, it is clear that extracting at high pressures, i.e. high enthalpy levels, increases the unit cost of steam. Efficiency and cost considerations prescribe that steam be extracted at lowest possible pressures. The reference areas were designed within these constraints. 131 The model of the extraction turbine-generator calculates the amount of electric power produced per hour as the demand for steam varies. Demand for steam from the community is inputted per hour and the result- ing output of electric power is calculated from the characteristics of the turbine, and the extraction pressure and flow. The amount of power output from a particular turbine design can be calculated from the mass flow rate, initial and final enthalpies of the steam, and the heat balance relationships for the turbine under consid- eration. The following equation describes this thermodynamic relation- ship for a single-purpose turbine-generator with a reheat cycle. Turbine work = GF * (GFH-GH) + GFR * (GFRH-GRH) 8.6.1 where, GF steam generator flow rate, pounds per hour GFH steam generator enthalpy, BTU's per pound CH = final steam enthalpy of the power cycle obtainable in the plant, BTU's per pound GFR = steam generator reheat flow rate, pounds per hour CFRH steam generator reheat enthalpy, BTU's per pound GRH final steam enthalpy of the reheat cycle, BTU's per pound. See Figure 8.12, generalized heat balance diagram with relative location of variables. The amount of electric power is found from dividing equation 8.6.1 by 3414 £22. to get kilowatts. our Electric power: Turbégi4work = kilowatts 8.6.2 132 It should be noted that equations 8.6.1 and 8.6.2 are not the same as the gross heat rate calculation. These equations describe the power cycle of the turbine-generator and not the total heat added to produce a kilowatt-hour of electric energy. Extracting steam from the turbine has the effect of reducing shaft work and thus electric power output. Extracting at a mass flow rate determined by the demand for steam, DEMAN, from the community, at the enthalpy level, XENTH, determined by the requirements of the steam dis- tribution system, modifies equation 8.6.1 as follows: Turbine work = CF * (CFH-GH) + CFR * (CFRH-CRH) - DEMAN * (XENTH-GH) 8.6. The power output with the effect of extracting steam is then, Turbine work from equation 8.6.3 Electric power = = kilowatts 8.6. 3414 The model calculates the effects on the power cycle of extracting steam by determining the kilowatt equivalence of the extracted steam as follows: DEMAN * (XENTH - CH) 3414 ENEXKW = where, DEMAN demand for steam from the community, pounds per hour XENTH enthalpy of extracted steam determined by the pressure requirements, BTU's per pound 8.6. 5 CH = final enthalpy of the power cycle obtainable in the plant, BTU's per pound ENEXKW power equivalence of the extracted steam lost from the power cycle, kilowatts. Extracting at more than one point along the turbine can be simulated by finding the power equivalence of each extraction point from the demand 133 flow rate and the enthalpy of extraction. The sum of the kilowatt equivalence for all the extraction points is the total power lost from the power cycle. The resulting output of electric power per hour is calculated by subtracting the power lost to extracted steam, ENEXKW, from the non- extraction output, calculated from equation 8.6.2, that is: ENERACT = ENERNON - ENEXKW 8.6.6 where, ENERNON non-extraction electric power output, power output if the plant is single-purpose, kilowatts ENEXKW = power lost to the power cycle due to extracted steam, kilowatts ENERACT = actual power output of the extraction turbine-generator, kilowatts The model of the power cycle for the extraction turbine-generator is general enough so that various sized turbine-generators can be simu- lated. This can be done by substituting the characteristic mass flow, and enthalpy values, taken from heat balance diagrams, for the variables in equation 8.6.1 and proceeding through to equation 8.6.6. See Figure 8.12 for the relative location of variables. The model of the turbine-generator is not a complete description since it does not include directly the affects of the feedwater cycle, the deaerator or the boiler feed pump. The total auxiliary power re- quired by these and other equipment is on the order of 10 percent of the generating unit rating and does not change continuously during operation of the plant. The results derived from the model deal with the affectscnithe power producing cyclezuuiefficiencies of conversion 134 ocHAMSH cowuomuuxm I Emummwa oocmHmm ummm NH.w wuswfim coauomuuxm mo mama 30am mmma maflmsuco cofiuomuuxo Homcmocoo CH Manamamuno maamcuco Hosea haamsuco umocou mum» 30am moms moons» zeamnuco acumumcmw Emoum mum» 30am moms Houmumcww Emmum mummcovcoo museum macho umumSommm z<2mo g omoH uwuuomam ms. socsaoamum who mu a 242mm mfizmx mo mmmu mum tho no mm. aucmsuauum acumuocoo amouw mmho .mmu ummcmm 135 through the system. The affects of auxiliary equipment is considered as a constant reducing the total electric power output of the system. That is, power used in auxiliary equipment is treated as if it were an inefficiency of conversion just like the boiler, which has a first law efficiency of 88 percent. The model of the dual-purpose plant system provides a vehicle for understanding the dynamics of an alternative design for energy production and use in a community. The physical realization of the system can be simulated under a variety of conditions. We can change steam demand characteristics to represent different community life styles or we can take an existing community and estimate steam demand based on methods outlined in Chapter V. With these parameters we can answer questions with respect to the energy losses,and output of the turbine-generator with respect to steam and electricity. The physical realization is only one part of the feasibility analy- sis, now we must examine the behavior and results of the model within economic constraints. Technically, the dual-purpose plant can provide steam to an urban community, and it can be located at just about any distance from the load center. But, can the system operate in the marketplace and what are the trade-offs in plant size, number of units, distance from the load center, and what are the costs of producing and distributing steam? And what is the cost of producing electric energy from these plants? To answer these questions, and others, an economic model of the dual-purpose plant was developed to predict the cost of producing elec- tricity and steam. 136 VIII.7 Cost Components The feasibility analysis of the dual-purpose power plant is literally a test to determine whether the system is of sufficient value to repay the effort and investment. We have seen the physical realization of the system and developed a model to describe its behavior under a variety of different conditions. Now we must add the economic variables to also determine the economic worth of the system. Can this system produce elec- tricity and steam at competitive prices, and what happens to these prices if costs change? These are questions the feasibility model must answer. The feasibility analysis of the dual-purpose plant includes two separate cost considerations. The capital cost of the total steam system and the total capital cost of the electric part of the plant comprise one of the cost components. The other consideration has to do with the cost of producing steam and electric energy. Together the feasible operation of the dual-purpose plant can be determined under a variety of economic conditions. First, we will examine the cost separation component for producing electric energy and steam of the feasibility model. There are two ways to cost allocate steam and electricity produced from a dual-purpose plant. One is the energy equivalence method of fuel cost allocation and the other is a fuel cost allocation to steam based on an established electricity cost (Leung, 1973). The method of energy equivalence of fuel cost allocation was used in the model to determine the cost of producing electricity and steam. Figure 8.13 shows the cost separation component of the model. The mathod based on an established cost of electricity will also be briefly Explained later. 137 unmam mmommamuaman mo Homo: Gofiumumamm umoo ma.m shaman xoam Amaomvoz