How does a fuel cell work?
All types of fuel cells require a fuel that reacts with oxygen and in the process releases the chemical energy contained in the fuel. However, the energy is not discharged in the form of heat but as electrical energy. The electrons released in this process are transported by an external electric circuit to the load, thus providing electric energy.
Compared to conventional power plants in which heat from the combustion of fuels is converted into electricity mechanically (by means of generators), in fuel cells, a substantial part of the energy losses involved in the power plant process is avoided because there is no combustion step.
Although in principle, fuel cells have a very simple structure, it is a challenge to identify materials that have the required properties, and are able to convert fuel and oxygen into usable electricity. Even when suitable materials have been found, another difficulty consists of giving them the right shape and making sure that the device built from these materials are robust and have a long lifetime.
Fuel flows on the anode side of the SOFC, and air on the cathode side. The oxygen from the air is ionized, which allows it to permeate the membrane (i.e. the electrolyte). In the solid oxide electrolyte, this is only possible at temperature of at least 600 °C. If hydrogen is used as a fuel, the oxygen reacts with the hydrogen to form water in an efficient conversion process that does not require combustion or produce harmful exhaust gases. If methane or gases containing methane are used, such as natural gas, biogas, or mine gas, some carbon dioxide is released, but much less than in conventional electricity generation.