&EPA United States Environmental Protection Agency Industrial Environmental Research EPA-600/7-79-1Q5a Laboratory April 1979 Research Triangle Park NC 27711 Comparative Assessment of Residential Energy Supply Systems That Use Fuel Cells (Executive Summary) Interagency Energy/Environment R&D Program Report ------- RESEARCH REPORTING SERIES Research reports of the Office of Research and Development, U.S. Environmental Protection Agency, have been grouped into nine series. These nine broad cate- gories were established to facilitate further development and application of en- vironmental technology. Elimination of traditional grouping was consciously planned to foster technology transfer and a maximum interface in related fields. The nine series are: 1. Environmental Health Effects Research 2. Environmental Protection Technology 3. Ecological Research 4. Environmental Monitoring 5. Socioeconomic Environmental Studies 6. Scientific and Technical Assessment Reports (STAR) 7. Interagency Energy-Environment Research and Development 8. "Special" Reports 9. Miscellaneous Reports This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT RESEARCH AND DEVELOPMENT series. Reports in this series result from the effort funded under the 17-agency Federal Energy/Environment Research and Development Program. These studies relate to EPA's mission to protect the public health and welfare from adverse effects of pollutants associated with energy sys- tems. The goal of the Program is to assure the rapid development of domestic energy supplies in an environmentally-compatible manner by providing the nec- essary environmental data and control technology. Investigations include analy- ses of the transport of energy-related pollutants and their health and ecological effects; assessments of, and development of, control technologies for energy systems; and integrated assessments of a wide-range of energy-related environ- mental issues. EPA REVIEW NOTICE This report has been reviewed by the participating Federal Agencies, and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Government, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. This document is available to the public through the National Technical Informa- tion Service, Springfield, Virginia 22161. ------- EPA-600/7-79-105a April 1979 Comparative Assessment of Residential Energy Supply Systems That Use Fuel Cells (Executive Summary) by R.V. Steele, D.C. Bomberger, K.M. Clark, R.F. Goldstein, R.L Hays, M.E. Gray and G. Ciprios, R.J. Bellows, H.H. Horowitz, C.W. Snyder (Exxon) SRI International 333 Ravenswood Avenue Menlo Park, California 94025 Contract No. 68-02-2180 Program Element No. EHB534 EPA Project Officer: Gary L Johnson Industrial Environmental Research Laboratory Office of Energy, Minerals, and Industry Research Triangle Park, NC 27711 Prepared for U.S. ENVIRONMENTAL PROTECTION AGENCY Office of Research and Development Washington, DC 20460 ------- SRI INTERNATIONAL COMPARATIVE ASSESSMENT OF RESIDENTIAL ENERGY SUPPLY SYSTEMS THAT USE FUEL CELLS EXECUTIVE SUMMARY What Are Fuel Cells? Are Fuel Cells Commercially Available Today? Fuel cells are devices capable of converting the chemical energy stored in a fuel directly into electrical energy without a step involving combustion. Hydrogen contained in the fuel is chemically combined with oxygen from the air to produce water and an electric current that can be regulated and used. Fundamentally, the process is just the inverse of the electrolysis of water into its component parts, a process often demonstrated in high school chemistry classes. Practically, a fuel cell consists of two electrodes, a catalyst used to promote the chemical reaction, and an electrolyte (a chemical substance that conducts electricity) separating the electrodes. As might be suspected, a device of such fundamental simplicity was first conceived long ago—in 1839 by Sir William Grove, a British jurist. Although old in concept, as practical devices for producing electricity in significant amounts, fuel cells are in their infancy. For space missions, fuel cells have been shown to be ideal power sources, partly because they convert on-board stores of hydrogen and oxygen to electrical power without producing excessive heat or vibration-producing mechanical motion. In fact, they provided electrical power in Gemini and Apollo spacecraft, but were still considered novel and exotic devices. ------- Made in limited quantities, and to extreme reliability standards, fuel cells for space craft are understandably expensive. Nevertheless, much has been learned from the space program about fuel cells and that knowledge is beginning to find earthbound applications in much-improved and less costly devices. More than 60 small (12.5 kW) fuel-cell power plants were field tested in 1972 and 1973. A 40-kW device was demonstrated in 1975, and now work is underway to demonstrate a 4.5-MW fuel cell in the Consolidated Edison (New York) utility system by 1980. Fuel-cell technology has come a long way and is nearing commercial readiness. Do Fuel Cells Possess Much of the present interest in fuel cells derives from Attractive Attributes? their unusually low environmental impact and their high efficiency. Because no combustion is involved, even fuel cells that use common fuels produce very low emissions of nitrogen or sulfur oxides; the emissions are many times below federal standards. Moreover, fuel cells generally consume no water and operate very quietly. As a result of its environmental good- neighborliness, a fuel-cell power plant can easily be located very near the power demands it serves, thereby lessening the need for high voltage electric transmission lines. ii ------- The ability to site fuel-cell power plants locally is much enhanced by their modular design (which allows off-site manufacturing) and their rapid installation. Accordingly, electric power utilities may soon have commercially available a device that enables system expansion in small increments. How Might Fuel Cells Fit into Electric Power Systems? Besides being suitable for small, dispersed, locally sited power stations, fuel cells can easily operate in applications that require output to follow demand closely. In fact, electric utility interest in fuel cells often centers on mid-1980s deployment for load-following. Again, because of their cleanliness, fuel cells may be installed in buildings or residential complexes where the combined production of electric power and heat could be used to satisfy heating and cooling demands in an integrated (or "cogeneration") fashion. The fuel-cell-derived electricity would be used to operate heat pumps to provide cooling and supplemental heating. Can Fuel Cells Use Coal or Coal-Derived Fuels? Fuel cells, like most fuel-consuming devices are indifferent to the origin of the fuel—as long as in final form it conforms to the chemical requirements of the device. Accordingly, natural gas, petroleum products, or similar fuels are perfectly acceptable in fuel cells provided that the fuels are first reformed to hydrogen and carbon dioxide and that harmful sulfur contamination is removed before the fuels enter the fuel cell proper. iii ------- Fuel cells, therefore, can have a place in a largely coal-based U.S. energy future. What Are Leading Coal-Based Already, U.S. electrical power is largely generated in Alternatives to Fuel Cells? coal-fired plants and the federal government is pushing for even more in an effort to save relatively scarce and expensive oil and natural gas for other uses. Larger, conventional coal-fired power plants, often located in remote areas and connected to urban load centers by high voltage transmission lines, certainly provide a well-proven alternative to electric power generated from fuel cells. So-called "combined-cycle" electrical power generation—a conventional boiler and steam turbine generator supplemented by a high-temperature gas turbine—is an improving technology gaining considerable attention among utilities. Certainly, by the time fuel-cell systems are perfected sufficiently to allow commercial deployment, combined-cycle systems will already be in use and fuel-cell systems will have to compete with them. Much of the U.S. space heating demand is met by the combustion of natural gas. Because so many consumer-owned heaters are already in place, gas utilities have strong incentive to supplement natural gas supplies with coal-derived substitutes that would not require alteration of either consumer appliances or habits. iv ------- Synthetic natural gas, (SNG) derived from coal, then, offers strong competition for the electric heating role a fuel-cell/heat pump combination could play in the market place. Can Fuel Cells be Compared with the Alternative Technologies? Because fuel cells must compete with so many electric power and heat-producing fuel and technology combinations, the relative advantages and disadvantages of fuel cells have proven difficult to discern clearly. Consequently, as a part of its mission to preserve and enchance environmental quality, the U.S. Environmental Protection Agency commissioned this study precisely to learn more about what might be expected from fuel cells when actually deployed in utility systems. To address this question, SRI International conceptually designed twelve energy systems able to provide residential heating and cooling using technologies projected to be available toward the end of this century. Only a few systems used fuel cells. As in most comparisons, some constraints were imposed to eliminate unnecessarily confusing complexities while providing a uniform framework for comparison. Accordingly, all systems use western coal as the primary energy resource, and all residences are assumed to have identical heating and cooling demands typical of the mid-continent United States. After winnowing out the clearly least attractive combinations, we selected five systems and compared them in great detail. ------- For all the comparisons, we examined the entire chain of the system, starting with the coal mine and ending with the heating and cooling of residences, to be sure that the claimed environmental advantages of the fuel cells at the point of electric power generation did not distract us from some important environmental impacts elsewhere in the system. Our five surviving systems, four of which use heat pumps for heating and cooling are: o System 1—A coal-fired power plant supplies electricity and a coal gasification plant supplies SNG to residences; electricity powers air conditioners and SNG is burned in gas furnaces. o System 2—A 26-MW fuel-cell power plant fueled by coal-derived SNG supplies electricity to residences with heat pumps. o System 3—A 26-MW fuel-cell power plant fueled by coal-derived naphtha supplies electricity to residences with heat pumps. o System 4—A combined-cycle power plant fueled by coal-derived fuel oil supplies electricity to residences with heat pumps. o System 5—A 100-kW fuel-cell power plant fueled by coal-derived SNG, sited in a housing complex, supplies electricity to townhouses with heat pumps; heat recovered from the fuel cell supplies supplemental space heating and hot water. Of these five, the first one most resembles the existing order in the utility industry, and the fourth constitutes an already evident evolutionary change of the industry. vi ------- What do the Comparisons Show? The scorecard for the various systems is mixed—no single system stands out as superior in all the attributes that will ultimately decide which systems will be deployed. Nevertheless, some very interesting facts emerge about energy systems that use fuel cells. Which System Costs the Consumer More? Are There Differences in the Capital Investment Required? Which Has the Best System Performance? The three fuel-cell systems provide heating and cooling to our standard residences at considerably higher cost that the two more conventional systems. In fact, the annual energy bill to a consumer using System 5 is over 63% higher than for one using System 1, the most conventional and lowest cost option. The order of cost, from the least expensive system to the most expensive, is 1,4,2,3,5. The scorecard for the capital intensiveness of the five systems largely follows the pattern of the annual cost to consumers. In order, from least to most capital intensive, are Systems 1, 4, 3, 2, 5. Because capital is itself a scarce resource, utilities most likely will show most interest in Systems 1 and 4. Because all five systems contain at least one element not yet proven in commercial service, such things as reliability, the degree of redundancy needed in a system, and the ability to integrate smoothly the new devices into a system are difficult to assess, more so than for most other comparison attributes. We judge, however that, overall, the most conventional system is most likely to give the best performance. System performance, from best to worst comes in this order: Systems 1, 2, 4, 3, 5. vii ------- Which System is Most Efficient? What About Air Quality? Are There Differences in Water Quality? When making a comparison of system efficiency, we were careful to account for energy losses at every step in proceeding from the coal mine to the heated and cooled residence. All fuel-cell systems are considerably more efficient than the most conventional system, System 1. Indeed, System 5 is 75% efficient, while System 1 is only 41% efficient. Systems 2, 3, and 4 possess nearly equal efficiencies in the 64% to 67% range. This attribute is particularly important because it shows that the systems using fuel cells required less coal to accomplish the same end—a virtue that, besides conserving resources, carries over into lessened environmental impact. Because maintenance of air quality around electric power generation plants is a vexing and costly problem, the relative scores for this indicator could prove especially important to utilities in the years ahead. We weighted equally pollutants emitted at the fuel production site and the fuel consumption site (both overwhelm the emissions from fuel transportation). Again, all three systems using fuel cells are superior to the two more conventional systems, with System 5 being the cleanest and System 1 emitting the most pollutants. In order, from least to most polluting are Systems 5, 2, 3, 4,1. For this indicator we weighted equally effluents and water consumption at the fuel production and the fuel consumption locations. vlii ------- All three fuel-cell systems are cleaner than the two more conventional systems. Again, System 5 is the cleanest, but this time System 4 degrades water quality the most. In order of cleanliness are Systems U} Zy «5j ly 4* How Do They Compare on Solid Waste? Most solid waste for this set of five systems is produced as ash in converting the coal to a more useful energy form. Consequently, scores in this category essentially mirror the overall system energy efficiency ratings—the most efficient System 5 also produces the least solid waste and the least efficient System 1 produces the most solid waste. Systems 2, 3, 4 are nearly tied, and produce about the same intermediate quantities. What About Land Use, Noise and Aesthetics? Is There a Pattern in the Comparison? The three parameters are closely linked because aesthetics and human exposure to noise produced are greatly affected by location and the amount of land occupied or disturbed. Overall, least obtrusive is System 5 and the most obtrusive is System 1. A striking pattern emerges when we assemble the scores for all categories of comparison. The fuel-cell systems are the most costly—to build and install as well as in end-use cost to consumers—but are the most environmentally benign and consume the least coal to get the heating and cooling job done. ix ------- We expected from the outset of this study that the fuel cells themselves would be clean compared to alternatives, but our finding that entire fuel-cell systems from resource extraction to final demand offer overall environmental benefits is new. Will Fuel Cell Systems Actually Be Used? How the trade-off between environmental cleanliness and economic cost will be valued in the next several decades will prove crucial to the question of whether fuel-cell systems resembling those we have examined will actually be deployed in meaningful numbers. One thing is certain: Fuel-cell systems possess a mixture of attributes much different from the more conventional electric power systems. As a result, U.S. utilities will have available an important new electric power option in the years ahead. Full analysis is available in the 500-page report: "Comparative Assessment of Residential Energy Supply Systems That use Fuel Cells," Environmental Protection Agency, Report No. 600/7-79-105b, 1979. ------- TECHNICAL REPORT DATA (Please read Instructions on the reverse before completing) REPORT NO. EPA-600/7-79-105a 2. 3. RECIPIENT'S ACCESSION NO. J. TITLE ANDSUBTITLE Comparative Assessment of Residential Energy Supply Systems That Use Fuel Cells (Executive Summary) 6. REPORT DATE April 1979 6. PERFORMING ORGANIZATION CODE R v. Steele,D. C. Bomberger ,K. M. Clark, R. F. Goldstein, R. L. Hays, M. E. Gray, G. Ciprios*, R.J.Bellows*.H.H.Horowitz, and C.W.Snyder* 8. PERFORMING ORGANIZATION REPORT NO. I. PERFORMING ORGANIZATION NAME AND ADDRESS SRI International 333 Ravens wood Avenue Menlo Park, California 94025 10. PROGRAM ELEMENT NO. EHB534 11. CONTRACT/GRANT NO. 68-02-2180 12. SPONSORING AGENCY NAME AND ADDRESS EPA, Office of Research and Development Industrial Environmental Research Laboratory Research Triangle Park, NC 27711 13. TYPE OF REPORT AND PERIOD COVERED Final; 9/76 - 1/79 14. SPONSORING AGENCY CODE EPA/600/13 ^.SUPPLEMENTARY NOTES JERL-RTP project officer is Gary L. Johnson, MD-63, 919/541- 2745. (*) Coauthors are Exxon personnel. 16. ABSTRACT The rep0rt gives results of a comparison of residential energy supply sys- tems using fuel cells. Twelve energy systems, able to provide residential heating and cooling using technologies projected to be available toward the end of this cen- tury, were designed conceptually. Only a few systems used fuel cells. All systems used Western coal as the primary energy source, and all residences were assumed to have identical heating and cooling demands typical of the mid-continent U.S. After screening, five systems were analyzed in detail. The entire energy cycle, from coal mine to end use, was examined for costs, efficiency, environmental im- pact, and applicability. The five energy systems are: (1) a coal-fired power plant supplying electricity and a coal gasification plant supplying SNG; (2) a 26-MW fuel- cell power plant fueled by coal-derived SNG supplying electricity; (3) a 26-MW fuel- cell power plant fueled by coal-derived naphtha supplying electricity; (4) a combined cycle power plant fueled by coal-derived fuel oil supplying electricity; and (5) a 100-kW fuel-cell power plant fueled by coal-derived SNG, sited in a housing com- plex, supplying electricity to heat pumps, with heat recovered from the fuel cell supplying supplemental space heating and hot water. Results indicate that the fuel cell systems are most costly, most efficient, and have least environmental impact. 7. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS >.IDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group pollution Assessments Fuel Cells Coal Gasification Energy Conversion Coal Techniques Naphthas Residential Buildings Fuel Oil Heating Cooling Systems Pollution Control Stationary Sources Substitute Natural Gas Natural Gas Heat Pumos 13B 10B 10A 13M 13A 14B 13H 21D 07C DISTRIBUTION STATEMEN1 Unlimited 19. SECURITY CLASS (This Report) Unclassified 21. NO. OF PAGES 12 20. SECURITY CLASS (Thispage) Unclassified 22. PRICE EpA Form 2220-1 (9-73) xi ------- |