Fuel cells are a proven power source for manned spacecraft where they generate electric power from stored hydrogen and oxygen that are carried in cryogenic-liquid form. The world's petroleum production is about to pass its peak, so a worldwide development effort is being directed into adapting these high-efficiency fuel cells into powering automobiles, buses, and trucks. A fuel cell can, theoretically, deliver 500 kilowatt-hours (kWh) per kilogram of hydrogen plus oxygen. Today's best lithium batteries can deliver around 120 kWh per kilogram. Fuel cells can convert fuel to electric power with an efficiency of over 80%. Even a diesel engine cannot do better than 40% at its optimum speed and load. In the past, fuel cells contained a platinum catalyst that costs $700 a troy ounce. This year, researchers at the University of Wisconsin announced the discovery of a nickel-tin catalyst that works! As a result, fuel cells can be a possible substitute for batteries in spacecraft. Fuel cell progress was the topic of three technical sessions at the 2003 International Energy Conversion Engineering Conference (IECEC). In plenary sessions, leaders in US industries and pertinent government laboratories discussed new applications for power-generating fuel cells. This conference, sponsored by the American Institute of Aeronautics and Astronautics, dealt with energy conversion for generating electric power in Earth-orbit satellites, space stations, Mars-surface exploration, propulsion of deep-space probes, as well as for earth-surface vehicles, and other applications. The latest developments in the energy and power fields were described in the 206 technical papers presented. Three very thorough presentations at this IECEC provided instructions and quantitative data that can be useful to an aerospace engineer who needs to evaluate fuel cells for his power-generating application. These papers, summarized in the sections that follow, cover: 1) the present and future performance of fuel cells; 2) the options in design configurations of an aerospace power source; and 3) how to develop performance, weight, and cost data for comparing fuel cells to alternatives for meeting the requirements of a given aerospace application.
