Fuel Cells Come Home

Figure 1. A fuel cell produces electricity by reacting hydrogen and oxygen with a catalyst, forming water while producing electricity and heat. Hydrogen is fed to the anode of the fuel cell, and oxygen (usually from ambient air) to the cathode. The reaction drives a flow of electrons from the anode to the cathode through an external electric circuit.

The American Power Corp. Residential Power Generator, closed (top), and open (above). On the left side is the reformer that extracts hydrogen from natural gas or other hydrocarbon fuels. Fuel cells, batteries, the inverter, the heat exchanger, the compressor, and the electronic controls are located on the right side.

Like batteries, fuel cells are electrochemical devices that produce electricity without combustion. They can produce electric power as long as they are supplied with fuel--namely, hydrogen-- and oxygen from air. The basic fuel cell reaction gives off only water and waste heat.

Combustion-Free Electricity

Reformers extract hydrogen from natural gas, propane, gasoline, methanol, or ethanol, releasing carbon dioxide. The process has few or no combustion byproducts such as nitrogen- and sulfur-oxides.

Raw hydrogen for fuel cells may eventually become available from renewable sources, for example from biomass, which has been processed in much the same way as fossil fuels. It is also possible to acquire hydrogen from water through a process called electrolysis. In this process, an electric current is passed through water to split the molecules into hydrogen and oxygen. The initial electric current can come from any source.

After the hydrogen is fed into the RFC, the device combines it with oxygen in a special membrane. As the gases combine, they produce energy; the membrane converts the energy to electricity. The process also releases heat and water (see Figure 1).

According to the manufacturers, RFCs require very little maintenance. They need an annual checkup for replacement of air filters, and a new stack of membranes every seven years. The device as a whole has a predicted life-span of twenty years. She says the current prototype is operating with very little maintenance.

Home Power Plants

Both Plug Power and APC's early RFCs are equipped with batteries to cover peak loads; the batteries will recharge during low-load periods. The two companies expect their RFCs to cost $3,000-$5,000, plus installation.

According to Plug Power spokesperson Debra Rock, the company is aiming for commercialization to begin in 2000. At that time, homeowners will be able to receive lower power rates by leasing fuel cells from their electric service providers. They will still have electric bills, but they will be lower. This type of service will be promoted especially in areas that do not currently have grid connection or are prone to transmission and distribution problems. Rock predicts that by 2003, the units will cost around $3,000, and homeowners will be able to buy them at stores, like appliances.

Utilities Get in the Act

While manufacturers have not precisely estimated total life cycle costs, a recent study done by Small-Scale Fuel Cell Commercialization Group Incorporated showed that the average total cost to generate electricity using a residential fuel cell would be 7¢/kWh when operating on natural gas and 11¢/kWh when using propane (based on costs of $3.25/MCF for natural gas 83¢/gallon for propane). Residential electricity in the United States currently costs between 3¢ and 15¢/ kWh. EPRI estimates that RFCs could generate electricity for 20% to 30% less money than centralized power plants.

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