|MadSci Network: Chemistry|
Greetings: I believe that the technology that you have asked about is the Hydrogen - Oxygen fuel cells that were developed by NASA in the 1970s for use on the Space Transportation System (STS) commonly called the Space Shuttle. Extensive detailed information about the STS fuel cells can be found at the following NASA URL: http://www.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-eps.html#sts- fuel-cell Each STS orbiter has three fuel cells to generate the prime electrical power. Each fuel cell power plant is 14 inches high, 15 inches wide and 40 inches long and weighs 255 pounds. The voltage and current range of each is 2 kilowatts at 32.5 volts dc, 61.5 amps, to 12 kilowatts at 27.5 volts dc, 436 amps. Each fuel cell is capable of supplying 12 kilowatts peak and 7 kilowatts maximum continuous power. Each fuel cell is serviced between flights and reused until each accumulates 2,000 hours of on-line service. Water and electricity are the products of the chemical reaction of oxygen and hydrogen that takes place in the STS fuel cells. The water must be removed or the cells will become saturated with water, and it is stored in water storage tanks for use by the crew (drinking, washing etc..) The major problem for commercial use of the STS fuel cell is that the hydrogen and oxygen fuels are very explosive and they must be stored at very cold (cryogenic) temperatures in the liquid state to fit the fuel tanks within the STS vehicle. If the fuels are stored in gas form at high pressures and at room temperature the tanks would become extremely large. An alternative is to use the oxygen in the air as an oxidizer and only store the hydrogen gas. Hydrogen powered aircraft an terrestrial vehicles would be very efficient and would produce mostly water and very small amounts of nitrogen compounds compared to today's cars and aircraft. The problem with this concept is that large fuel tanks of explosive hydrogen stored at high pressure are required to equal the range of current internal combustion or turbine powered vehicles. The city of Riverside California has several hydrogen fueled busses in service that use large fuel tanks filled with nickel hydride. Nickel hydride has the unique ability to absorb several atmospheres of hydrogen gas in a low pressure tank. (The chemical effect is similar to putting lots of sugar into a glass of water without changing the volume of the liquid).The busses still require a very large fuel tank the size of the bus frame but they are about one quarter the size of a hydrogen pressure tank with the same volume of fuel. I have not heard if there have been any car crashes into the Riverside busses yet to see what would happen to the released hydrogen gas. The major automobile companies have formed consortia with the Federal Government to develop hybrid fueled vehicles (electric and petroleum), more efficient batteries and new fuel cell concepts to extend the 60 to 100 mile range of current electric vehicles. However, these fuel cells will efficiently burn conventional petroleum based fuels to generate hydrogen fuel. This enables the current petroleum based infrastructure to provide the fuel and service stations for electric vehicles.A great deal of research is still required to make this concept viable. The head of the General Motors Research Group has a paper on GM's experience with the EV1 electric car and the future directions GM is taking in this area at the following URL: http://www.gm.com/about/info/overview/RD_Center/websiter/intro/ 9712kb_EV.html There is an interesting Web site with links to dozens of projects at large and small companies along with links to commentaries on many of the political issues involved - "If you are interested in Solar cars, Electric and Hybrid Vehicles, Renewable Energy, Whistleblowing, or political intrigue" the URL is: http://hgea01.hgea.org/~daver/evschpv.htm At this URL both American and foreign companies are linked along with flywheel, solar and other alternate energy projects. Best Regards, your Mad Scientist Adrian Popa
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