Power plants, fuel-cell

Fhosphoric acid does not have all the properties of an ideal fuel cell electrolyte. Because it is chemically stable, relatively nonvolatile at temperatures above 200 C, and rejects carbon dioxide, it is useful in electric utility fuel cell power plants that use fuel cell waste heat to raise steam for reforming natural gas and liquid fuels. Although phosphoric acid is the only common acid combining the above properties, it does exhibit a deleterious effect on air electrode kinetics when compared with other electrolytes ( ) including such materials as sulfuric and perchloric acids, whose chemical instability at T > 120 C render them unsuitable for utility fuel cell use. In the second part of this paper, we will review progress towards the development of new acid electrolytes for fuel cells. 

The fuel eell is a nineteenth eentuiy invention in the twentieth eentury it heeame the heart of an eleetroehemical power plant and power souree, whieh is now in a stage of advaneed technology development. Its first and only applieation since the early 1960s, has been as an auxiliary power souree for spaee flights by the National Aeronautics and Space Administration (NASA). During the past decade, development for terrestrial (eivihan and defense) applieations has led to its commercialization and research on utilization in a variety of applications. Programs in the United States, Japan, Europe, and some other eoimtries are focused on the development of fuel cell power plant/power sources for (1) base-load,... 

The enthusiasm for developing DMFCs (the fuel cell researcher s dream) evolved in the 1960s, which was really the boom period for R D activities on all types of fuel cell technologies, mainly because of NASA s vital need for fuel cell power plants for space vehicles. As early as the 1960s it was recognized that the major challenges in developing DMFCs... 

Callahan, M., Hydrocarbon fuel conditioner for a 1.5 kW fuel cell power plant, Proc. 26th Power Sources Symp., Red Bank, NJ, 181,1974. 

Figure 6.2 Simplified process of a fuel cell power plant.

Figure 6.3 provides a simplified block diagram of a fuel cell power plant system. Gasification is used to convert the solid fuel to gas, which is processed to remove sulfur compounds, tars, particulates, and trace contaminants. The clean gas is then converted to electricity in the FC. Waste heat from the FC is used to generate steam, which can be used to run the gasification process and to generate additional power in the bottoming cycle. 

In the United States, in the commercial sector, the most attractive application for near-term fuel cell technology is onsite cogeneration. In this application, the fuel cell power plant is located at the site of the end user, providing both electric and thermal energy. On-site applications in the commercial... 

Ghezell-Ayagh et. (2001) Operation and control of direct reforming fuel cell power plant, Proc. IEEE Power Eng. Soc. Winter Meeting. 

Ghezell-Ayagh et al. (1999) Development of a stack simulatioin model for control study on direct reforming molten carbonate fuel cell power plant, IEEE Trans. Energy Conversion, Vol. 14, No. 4. 

The fuel cell coolant system uses a liquid fluorinated hydrocarbon and transfers the waste heat from the cell stack through the fuel cell heat exchanger of the fuel cell power plant to the Freon-21 coolant loop system in the midfuselage. Internal control of the circulating fluid keeps the cell stack at an operating temperature of approximately 200°F. 

Figure 1-5 Fuel Cell Power Plant Major Processes... 

The fuel processor efficiency is size dependent therefore, small fuel cell power plants using externally reformed hydrocarbon fuels would have a lower overall system efficiency. 

Figure 1-6 Relative Emissions of PAFC Fuel Cell Power Plants Compared to Stringent Los Angeles Basin Requirements...

PAFC systems achieve about 37 to 42% electrical efficiency (based on the LHV of natural gas). This is at the low end of the efficiency goal for fuel cell power plants. PAFCs use high cost precious metal catalysts such as platinum. The fuel has to be reformed external to the cell, and CO has to be shifted by a water gas reaction to below 3 to 5 vol% at the inlet to the fuel cell anode or it will affect the catalyst. These limitations have prompted development of the alternate, higher temperature cells, MCFC, and SOFC. 

J. M. King, N. Ishikawa, "Phosphoric Acid Fuel Cell Power Plant Improvements and Commercial Fleet Experience," Nov. 96 Fuel Cell Seminar. www.intemationalfuelcells.com. 

Investigation of Design and Manufacturing Methods for Low-Cost Fabrication of High Efficiency, High Power Density PEM Fuel Cell Power Plant," prepared by International Fuel Cells, Final Report FCR-11320A, June 10, 1991. 

Overview of 11 MW Fuel Cell Power Plant," Non-published information from Tokyo Electric Power Company, September 1989. 

Electric Power System Design For specific applications, fuel cells can be used to supply DC power distribution systems designed to feed DC drives such as motors or solenoids, controls, and other auxiliary system equipment. The goal of the commercial fuel cell power plant is to deliver usable AC power to an electrical distribution system. This goal is accomplished through a subsystem that has the capability to deliver the real power (watts) and reactive power (VARS) to a facility s internal power distribution system or to a utility s grid. The power conditioning... 

Connection to the utility grid provides many advantages to on-site power producers such as reliability improvement and increase of load factor, as well as giving the electric utilities a chance to improve the supply capability. When a fuel cell power plant is used for electric utility applications, the inverter is the interface equipment between the fuel cell and the electrical network. The inverter acts as the voltage and frequency adjuster to the final load. The interface conditions require the following characteristics for the inverter ... 

V. Minkov, et al., "Topping Cycle Fuel Cells Effective Combined with Turbines," Power Engineering, July 1988, pp. 35-39. "Design and Economics of Large Fuel Cell Power Plants," presented at 1986 Fuel Cell Seminar, Tucson, AZ, p 255. 

Thomas L. Buchanan, John H. Hirschenhofer, David B. Stauffer, and Jay S. White, "Carbon Dioxide Capture in Fuel Cell Power Systems," September 1994, G/C Report 2981. "Overview of 11 MW Fuel Cell Power Plant," Non-published information from Tokyo Electric Power Company, September 1989. 

T.J. George, K.D Lyons, and R. James m, "Multistaged Oxide Fuel Cell Power Plant Concept," May 1998. 

Three major contributors are considered in the computation of the COE for a fuel cell power plant 1) capital cost, 2) fuel cost and 3) operation and maintenance costs. The cost of electricity ( /MWh) can be calculated using these parameters as follows ... 

There is a need for an easily understood, flexible, and reasonably accurate methodology for rapidly estimating the cost of conceptual fuel cell power plants. 

One method proposed for estimating the cost of fuel cell power plants is to calculate distributive (bulk) costs as a function of the equipment cost using established factors based on conventional generating technologies. When applied in such a way as to compensate for the differences associated with a fuel cell plant, this approach can yield reasonable results. NETL has elected, based on the international prominence of the Association for the Advancement of Cost Engineering (AACE), to utilize this approach in estimating the costs for fuel cell/turbine power plant systems currently under study. 

T.J. George, R. RJ James HI, K. D. Lyons, "Multi-Staged Fuel Cell Power Plant (Targeting 80% Lower Heating Value Efficiency)," Power Generation International 1998 Conference, December 9-11, 1998, Orange County Convention Center, Orlando, Florida. 

American National Standards Institute (ANSI) ANSI has served in its capacity as administrator and coordinator of the United States private sector voluntary standardization system for 80 years. The Institute is a private, nonprofit membership organization supported by a diverse constituency of private and public sector organizations. ANSI Z21.83 has been published and provides a means of testing and certifying the safety of stationary fuel cell power plants having a capacity of less than 1 MW. 

ANSI Z21.83-1998 ANSI Product Standard - Provides detailed test and examination criteria for fuel cell power plants that make use of natural and liquefied petroleum gases. 

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