Fuels contain stored chemical energy that can be released through burning (combustion) or electrochemical conversion - as in the case of a fuel cell.
In the case of hydrocarbon fuels, or Hydrogen, energy is stored in the form of chemical energy. If the fuel is burnt, the chemical energy is converted into heat and light. In a fuel cell, the chemical energy is electrochemically converted into electrical energy (electricity) and heat. As a result, fuel cells are much more efficient at converting fuels into electricity than combustion engines.
Fuel cells are able to run on a variety of different fuels. Most Fuel Cell Vehicles contain PEM Fuel Cells which require pure Hydrogen, and as a result there is a perception that fuel cells always require Hydrogen. This is not the case - the majority of Primary Power Systems Fuel Cell Systems are designed to run on light hydrocarbon fuels such as Natural Gas or biogas. Portable Power and Micro Power fuel cell systems are often designed to run on liquid fuels such as Methanol, or propane.
All hydrocarbon fuels - such as fossil fuels like oil and coal - contain Hydrogen. It is possible to isolate the Hydrogen from such fuels which can then purified and used as a fuel for PEM fuel cells and Alkaline Fuel Cells (AFC). Gaseous fuels like Natural Gas can be Reformed to separate the Hydrogen from other elements such as carbon, and contaminants such as sulphur which are can poison sensitive fuel cell Membranes and Catalysts.
Solid fuels such as biomass and coal can be gasified into Synthesis Gas - a mixture of Hydrogen and carbon monoxide - referred to as syngas, which can then either be used directly in high temperature fuel cells such as Solid Oxide Fuel Cells (SOFC) and Molten Carbonate Fuel Cells (MCFC), or converted into liquid fuels via the fischer-tropsch process. Alternatively the Hydrogen can be separated from the carbon monoxide (through a palladium membrane), where it can then be used to power PEM fuel cells and Alkaline Fuel Cells (AFC). |
