Fuel cells resemble both a battery and an engine. Like batteries, they provide electricity from chemical reactions without combustion or moving parts. But they never need recharging because like an engine they run off a fuel source. The fuel source is hydrogen, most abundant element in the universe. Combining with oxygen, the reaction pumps out electricity, heat and pure water.
Most fuel cells use fossil fuels, breaking hydrogen from carbon.
So fuel cells release some climate-altering greenhouse gases, but less than if the fuel is burned. A company called Energy Conversion Devices is working on an even safer solid-form hydrogen. Fuel cells can be scaled from postage-stamp size to utility power plant. Several companies plan to market home systems around the size of a major appliance. Today a couple of hundred 200-kilowatt fuel cells are part of the power supply at institutional sites ranging from a New York City police station to Vandenberg Air Force Base.