Like many recent visitors to China, Sadeg Faris was appalled by the quality of the air in the big cities. "In Beijing," he said, "the air was so terrible, I couldn't see the sun."
Unlike most visitors to the Middle Kingdom, however, Faris is in a position to do something about that situation. His company, eVonyx Inc. (so spelled to reflect its intended pronunciation, ee-vee-onyx), Hawthorne, N.Y., is developing metal-based fuel cells that Faris hopes will one day help improve air quality by powering electric cars and trucks in crowded cities around the world.
To get his plan moving, though, Faris will begin in a more modest way: by making small fuel cell systems for powering electric scooters in Southeast Asia [figure]. If successful, these fuel cells could go a long way toward cleaning up the air in that part of the world, where scooters and motorbikes powered by highly polluting two-stroke engines are the most common form of motorized transport.
In choosing electric vehicles as the principal application of his fuel cells, Faris is bucking a trend. Most fuel-cell manufacturers agree that while EVs will eventually be an excellent application for fuel cells, that market will not materialize for years.
A more immediate application for metal-based fuel cells is as backup and emergency electricity sources to replace generators driven by internal combustion engines. As Jeff Colborn, president and chief executive officer of Metallic Power Inc., Carlsbad, Calif., sees it, one of his company's zinc-air fuel cell systems could sit in an office during a power outage, powering computers, lights, and other gear while generating neither noise nor pollutants.
Another maker of metal-based cells, Aluminum-Power Inc., Toronto, sees backup power systems for telecommunications centers as the most immediately profitable use for its products. The key application, according to Rafael Ferry, Aluminum-Power's marketing vice president, will be in metropolitan-area networks, where it is very expensive to rent space for conventional lead-acid batteries. Fuel cells have much higher volumetric energy densities than those batteries and therefore require much less real estate to provide the same amount of backup.
Although these executives don't agree on all the details in applying this technology, they do have a common belief: better fuel cells can be made by basing them on metals like aluminum or zinc instead of on hydrogen gas. So far, all three companies are still in the prototype stage of fuel-cell development, with commercial products a year or so away. Those products will include small battery-like units suitable for powering cell phones and laptop computers, medium-sized (around 5-kW) portable systems for emergency use, and large (on the order of 1-MW) stationary systems.
The best-known fuel cells, the ones based on hydrogen, feed a continuous stream of the gas to the anode [see "Fuel Cells for Dummies"]. The waste product is water vapor, which can be freely discharged into the atmosphere and is recycled for free by Mother Nature, a neat advantage. Such cells are being deployed today on a more-or-less experimental basis in vehicles, especially buses, and in stationary applications.
Another plus for these hydrogen-based systems (and others based on flowing gases or liquids) is easy thermal management--no need to add a separate liquid or air heating or cooling system. On a weight basis, too, hydrogen is a very efficient fuel; each kilogram of it packs 42 kWh of energy--three times as much as the same weight of gasoline and a thousand times as much as a lead-acid battery of the same weight.
In the near-term, metal-based fuel cells could replace backup generators driven by internal combustion engines
So why all the interest in metal-based fuel cells? Briefly stated, they store a lot of energy in a small space both conveniently and safely.
Although hydrogen does indeed have a specific energy of 42 kWh/kg, it is such a light substance that squeezing a kilogram of it into a reasonable amount of space presents quite a challenge. At the not inconsiderable pressure of 35 megapascals (over 345 atmospheres), a liter of hydrogen weighs only 31 grams and contains 1.3 kWh of energy. The result is that the containment vessel weighs considerably more than the gas.