Fuel Cells AJ Appleby, Texas A&M University, College Station, TX, USA & 2009 Elsevier B.V. All rights reserved. Introduction This article covers post-prototype fuel cell (FC) systems in stationary or ‘on-site’ applications, for use in non-grid-con- nected dispersed generation, or grid-connected distributed generation. Both are referred to here as DG. They include a range of sizes from kilowatt to megawatt scale, and may be in combined heat and power (CHP, cogeneration or dual en- ergy use systems), or as electricity-only units. Trigeneration (combined heat, power, and cooling) is a further possibility. The article starts with a general discussion of on-site power systems, and introduces the different types of FC devices for these applications. This is followed by general sections on on-site power systems and their characteristics, and on fuels for DG applications. Sections follow on the subsystems’ aspects of FC systems, and on their scaling characteristics. Detailed sections on each FC technology, named for the electrolyte used in the electrochemical fuel gas-to-direct current (DC) power converter (the FC stack), are then given. The FC systems considered are the phosphoric acid fuel cell (PAFC), the molten carbonate fuel cell (MCFC), the solid oxide fuel cell (SOFC), the proton-exchange membrane or polymer electrolyte membrane fuel cell (PEMFC), and the alkaline fuel cell (AFC). Except for the PAFC, each technology is reviewed up to that of prototype stationary systems in Fuel Cells – Overview: Introduction. The PAFC up to this stage is discussed in Fuel Cells – Phosphoric Acid Fuel Cells: Overview. In the case of the PAFC, the most important devel- oper has been International Fuel Cells (IFCs, a part- nership of United Technologies Pratt and Whitney Aircraft Division, South Windsor, CT, and Toshiba Corporation, Kawasaki, Japan), which is now UTC Power Corporation. Other important work has taken place at Westinghouse (Pittsburgh, PA, USA) and successor companies. Work in Japan took place at the Fuji Electric Company and Mitsubishi Electric Corporation (both Tokyo, Japan), Toshiba, and Hitachi (Hitachi-shi, Japan). The prime US developer of the post-prototype MCFC was Energy Research Corporation (ERC; Dan- bury, CT, USA), which became FuelCell Energy in 1999. The second US MCFC developer in the late 1980s was MC-Power (Burr Ridge, IL, USA), a consortium of the Institute of Gas Technology (IGT, Des Plaines, IL, providing technology), Bechtel Corp. (engineering), and Stuart and Stevenson (packaging), associated with Ishi- kawajima-Harima Heavy Industries (IHI, Tokyo, Japan). The latter had an early exchange agreement with IGT, but it did not share MC-Power’s technology. The pioneer SOFC developer was Westinghouse Electric Company (now Siemens Westinghouse Fuel Cells, Pittsburgh, PA, USA), but in recent years a large number of other de- velopers have come into the field, both in the United States and overseas. The PEMFC was originally de- veloped at the General Electric Company R&D La- boratories (Schenectady, NY, USA), and then by Ballard Power Systems (North Vancouver, BC, Canada). Again, there are now numerous developers of this technology. In contrast, the stationary AFC is represented by only a handful of developers. The AFC section includes an extensive discussion of future sources of hydrogen (H 2 ) fuel for this (and possibly other) FC technology. Following this discussion are sections on electrical issues for stationary FCs, economics, and the conclusions. Throughout costs have been adjusted to third-quarter 2007 US dollars, unless otherwise stated. General The electric utility industry has been traditionally based on large central generating stations feeding a radiating transmission and distribution system. A process of de- regulation, liberalization, and privatization is now in place worldwide. This started in 1978 in the United States with the Public Utility Regulatory Policies Act. The deregulation process allows wholesale and retail power trading, which is tending to make central power generation and transmission trend toward a distributed power supply with decentralized power generation. There are arguments beyond the existence of de- regulation for the evolution toward decentralized gen- eration and a distributed power supply. These involve economics, ecology, and security. Large central power plants have operational and cost advantages, particularly economies of scale. However, unless they are integrated into industrial complexes, the waste heat that they produce cannot be used, because of the high cost of long-distance heat transport to populated areas, since environmental considerations demand that new plants must be remote from these. One solution to this problem is decentralized generation, that is, the cogeneration of electrical energy and heat energy at the place where both are required, consistent with environ- mental requirements. Decentralized plants will be much smaller than central stations, and will require the use of clean fuel for use on-site. Their pollutant emissions must 76 . that of prototype stationary systems in Fuel Cells – Overview: Introduction. The PAFC up to this stage is discussed in Fuel Cells – Phosphoric Acid Fuel Cells: Overview. In the case of the PAFC,. electrochemical fuel gas-to-direct current (DC) power converter (the FC stack), are then given. The FC systems considered are the phosphoric acid fuel cell (PAFC), the molten carbonate fuel cell (MCFC), the. carbonate fuel cell (MCFC), the solid oxide fuel cell (SOFC), the proton-exchange membrane or polymer electrolyte membrane fuel cell (PEMFC), and the alkaline fuel cell (AFC). Except for the PAFC,