PROVIDING AND PROCESSING FUEL

摘要

Hydrogen, the preferred fuel for fuel cells, can be obtained from many sources. Fossil fuels such as oil, natural gases and coal, as well as bio-fuels can all be chemically converted to hydrogen. The basic chemistry of the various steps in the conversion is well known. However, each type of fuel cell has different fuelling requirements and therefore the design of fuel processors depends not only on the availability and form of fuel but also the application. For stationary power plants natural gas is an ideal fuel. It is best converted to hydrogen as close to the fuel cell as possible. In the case of the MCFC and SOFC this ensures high efficiency by using heat that would otherwise be lost from the stack. Recent advances in micro-channel catalytic reactor design may also lead to higher efficiencies and more compact stationary and portable systems. For transportation applications, hydrogen appears to be the preferred fuel in the long term. In the near term, methanol is a good fuel to use in vehicles, since it can be converted relatively easily on-board to hydrogen. Hydrogen can be generated by electrolysing water, and in combination with a fuel cell, this offers a means of storing energy from intermittent renewable power sources. In the future, hydrogen may be generated by direct solar electro-photolysis, or by biological methods. As such technologies advance, the transportation and storage of hydrogen stands out as perhaps the major barrier to the realisation of commercial fuel cell systems.