This is then used to run a turbine to produce electricity. Thus there are many intermediate steps each with certain efficiency (always less than 100%) associated with each of them. This is because thermal energy is the worst form of energy with maximum entropy and therefore can never be converted fully into useful work.
Now the overall efficiency of chemical potential energy to electricity conversion is a product of efficiency of each of the intermediate steps and therefore is much smaller. The best thermal power plants operate at maximum conversion efficiency of about 40%. Also, the combustion products are highly polluting adding to carbon emission and global warming. Fuel cells on the other hand convert the chemical potential energy directly into electricity and thus have very high conversion efficiency which is typically 70%. Besides, the reaction products are relatively harmless and in many cases completely harmless. Thus fuel cells are being seen as power plants of future and a tangible potential solution for containing the menace of carbon emission and therefore, global warming. These are already into many specialized and high end applications. In this report the basic principle, related developments and current and potential applications of fuel cells are briefly discussed.
A fuel cell is like a galvanic cell. It directly converts chemical energy into electricity and is highly efficient. It is now possible to make such cells in which reactants are fed continuously to the electrodes and products are removed continuously from the electrolyte compartment. Galvanic cells that are designed to convert the energy of combustion of fuels like hydrogen, methane, methanol, etc. directly into electrical energy are called fuel cells.
Such a fuel cell was used for providing electrical power in the Apollo space program.