Afuel cell combines hydrogen and oxygen to produce electricity, heat, and water. fuel cells are often compared to batteries. both convert the energy produced by a chemical reaction into usable electric power. however, the fuel cell will produce electricity as long as fuel (hydrogen) is supplied, never losing its charge. nasa uses hydrogen fuel to launch the space shuttles. fuel cells are a promising technology for use as a source of heat and electricity for buildings. where else are hydrogen fuel cells used? all, but one, apply.