Hydrogen is an attractive alternative to carbon-based fuels. Part of its attraction is that it can be produced from diverse resources, both renewable (hydro, wind, solar, biomass, geothermal) and non-renewable (coal, natural gas, nuclear). Hydrogen can then be utilised in high-efficiency power generation systems, including fuel cells, for both vehicular transportation and distributed electricity generation. Fuel cells convert hydrogen or a hydrogen-rich fuel and an oxidant (usually pure oxygen or oxygen from air) directly into electricity using a low-temperature electrochemical process.