Hydrogen fuel cells are starting to show up in homes around the U.S., providing consumers with an additional alternative energy option. Though residential installations to this point have been primarily custom-engineered setups, several companies are developing or already are offering products that could expand the technology to broader applications. Fuel cells generate electricity by stripping electrons from hydrogen fuel; only water and heat are emitted after the spent hydrogen combines with oxygen (see illustration, above). When tied to solar systems, fuel cells use hydrogen created when excess solar power passes through an electrolyzer; the hydrogen is then stored to power the fuel cell when the PVs aren’t generating enough to meet the demand. In grid-connected systems for main or backup power, the hydrogen is extracted from natural gas or propane.

With estimated per-kilowatt costs of $3,000 to $4,500, it could be a while before residential systems hit the mainstream. A federal tax credit can be used toward 30% of the cost, up to $1,000 per kW.

Questions have been raised about the amount of energy consumed to make hydrogen and the CO2 generated when hydrogen is extracted from natural gas or propane, but industry advocate Fuel Cells 2000 says those concerns are made up for in the higher efficiency of fuel cell operation (47% efficient versus 35% for central utility), lower emissions, and cogeneration of heat that increases energy efficiency to around 85% to 90%. The industry is working to develop renewable forms of hydrogen—such as from biomass, solar, and wind energy—that also would reduce production emissions. (Residential systems tied in with PVs already accomplish this, using solar power to extract the hydrogen.)

To learn more, visit Fuel Cells 2000 at www.fuelcells.org and the U.S. Fuel Cell Council at www.usfcc.com.  —Katy Tomasulo