Fuel Cells For The Masses
A recent fuel cell success story has hit the mass media in a whirlwind–fuel cells that run on gasoline, courtesy of the Department of Energy (DOE) and Arthur D. Little. These cells would allow electric vehicle (EV) users to utilize the existing fuel infrastructure, eliminating a big hurdle in the EV race. They would also eliminate the “battery” dilemma. No more long recharging times, expensive charging infrastructure or distance worries. It is truly a public relations coup for DOE and Little. Chrysler is also a big player in this R&D nirvana, riding high on the widely touted breakthrough.
But just how close are these cells to commercialization? Chrysler has announced plans for a demonstration vehicle in only two years, with possible commercial availability in five. This seems a bit optimistic, especially coming from the firm that has been teasing the public with photographs of its Plymouth Prowler for a good two years. I have yet to see one of those on a car lot with a price tag in the window. So far Chrysler`s Internet site still says the price is “TBA.” Fuel cell aficionados shouldn`t hold their breath on that two-year window for a fuel cell vehicle.
This technology does sound promising, however. A vehicle powered by one of these fuel cells would offer approximately double the fuel efficiency of an internal combustion engine and as little as 30 percent of the carbon emissions. “This discovery is important in that it also incorporates a fuel flexible design,” said Jefferey Bently, Arthur D. Little vice president. “Our fuel processor design is capable of converting a variety of hydrocarbon fuels such as gasoline and ethanol into hydrogen.” Laboratory testing has verified its performance on several fuels.
The basic steps in the process include: fuel vaporizer–The fuel is heated to convert it from a liquid to a gas to ensure cleaner, soot-free combustion; POX–The vaporized gasoline is processed in a partial oxidation (POX) reactor, essentially a metal canister with a spark plug. By limiting the amount of air in this low-pressure environment, hydrogen and carbon monoxide (CO) are produced.
Sulfur in the gas is converted into hydrogen sulfide gas and filtered from the vapor; water-gas shift–Since CO poisons fuel cells, it must be eliminated or reduced to less than 10 ppm. Water is introduced as steam and, acting with copper oxide and zinc oxide catalysts, converts nearly all of the CO to CO2. Additional hydrogen fuel is produced in this stage; and PROX–While the vapor has been converted from about 30 percent CO to a hydrogen-rich gas containing only about 1 percent CO in the water-gas shift, that is still 10,000 ppm. In the preferential oxidation (PROX) stage, air is injected into this gas, which reacts with the remaining CO over a platinum catalyst to produce CO2, leaving only a trace of CO. This process requires heat exchangers to maintain effective performance since the clean gas must then be cooled for the fuel cell.
The fuel cell stack, according to predictions from Chrysler, could be a 5-foot long, 8-inch diameter cylinder, which could be in a tunnel in the center of a mid-sized sedan. The fuel tank, battery packs and motor controller might be under the trunk. The fuel processor components could be housed under the hood.
The biggest obstacle that remains for this technology is cost. Mass produced fuel cells would cost more than $200/kW using today`s technology. Conventional powertrain costs are less than $30/kW today. “Ten years ago, fuel cells were 10,000 times too expensive and now they`re about 10 times too costly,” said Christopher E. Borroni-Bird, Ph.D., Chrysler Advanced Technologies specialist.
A less trumpeted application of this fuel cell technology is the in-home power plant, being developed by Plug Power LLC. “In the same way personal computers have replaced mainframes, we believe fuel cells will reduce the electric industry`s reliance on large, centrally located power plants,” said Anthony Early, a Plug Power director. Plug Power plans to use the technology to convert natural gas into electricity for residential use.
The residential system visualized would be about the size of a dishwasher and capable of meeting the energy demands of a 3,000 square foot house. No connection to a power plant would be needed. Under the current development plan, customers wouldn`t pay for the device, but would be charged for the power used. The company has announced plans for demonstration units within one year. Plug Power is partly owned by DTE Energy. p