06/07/2006
Metal, Not Hydrogen?
[Dr. Bortrum returns June 21]
Am I doomed? Yesterday I awoke, looked at the clock and it was 6:06 AM on 6/06/06 – how Satanic can it be? Last week I discussed hybrid vehicles, and as an example chose the Toyota Prius, the first hybrid to garner any significant market here in the U.S. At the polls yesterday (it was primary election day in NJ), one of the poll workers is our friend who owns a Prius. I told her that I thought I heard of a recall on the news last week. She hadn’t heard any such news and said they’d have to take it away from her by force – she loves the car! Keeping the ominous 666 date in mind, I checked on msnbc.com and, sure enough, there is a massive worldwide recall by Toyota that includes about 170,000 Priuses in the U.S. for a possible steering defect. Maybe I’ll keep my 1997 VW Jetta a bit longer.
In last week’s column, I expressed skepticism about the future of hydrogen fuel cells as power sources for cars and about the future of pure battery-powered electric vehicles. Then I realized that for quite some time I have not been following the battery field as closely as I should. For example, an article by Owen Edwards in the June issue of Smithsonian told me that I’d missed a battery-related funeral at the Hollywood Forever Cemetery in Los Angeles in 2003. To the strains of a bagpipe, a white hearse circled the cemetery followed by a procession of mourners driving their General Motors EV1s. The EV1 was GM’s sleek production model battery-powered electric vehicle. There were about 1,100 of them manufactured and they were leased to drivers in California and Arizona starting in 1996. The mourners in LA found their leases expiring and almost all the EV1s were to be destroyed. So much for GM’s electric vehicle, with its range of about 100 miles.
At the bottom of my pile of unread journals, I found the Autumn 2005 issue of Batteries & Energy Storage Technology (BEST), a magazine targeting manufacturers and users of electrochemical power. One of the articles, “Hydrogen future? What Future?”, dealt with the views of one Ulf Bossel of the European Fuel Cell Forum. Ulf concludes that cars powered by hydrogen fuel cells don’t have a chance. He considers biomass fuels such as ethanol or biodiesel in hybrid vehicles as the way to go.
What really caught my attention in the BEST magazine was a section on a different kind of fuel cell, the zinc-air fuel cell (ZAFC). If you’re hard of hearing, you’ve used many small button cells to power your hearing aid. The overwhelming majority of these cells are zinc-air batteries. Zinc is the active material in one electrode while oxygen (from the air) is the active material in the other electrode. The hearing aid battery is neat in that you don’t have to store the oxygen in the battery. It’s free, comprising about 20% of our air.
When you put the battery in your hearing aid, you open a tab to let the air in and the battery starts working. Because you don’t have to pack oxygen in the battery initially, you have room for more zinc and the battery lasts longer. Although the chemistry is a bit more complicated, as the battery discharges zinc reacts with oxygen to form zinc oxide. In the hydrogen fuel cell, hydrogen reacts with oxygen to form a “hydrogen oxide”, water.
With a hydrogen fuel cell in your car, when you run low on hydrogen you would stop at your “gas” station and fill up your (pressurized) tank with hydrogen. Having had a relatively mild hydrogen explosion in my lab at Bell Labs, I wouldn’t feel all that comfortable with the operation. Suppose, instead of a hydrogen fuel cell, we use a very large version of a hearing aid battery to drive our car. What happens when most of the zinc has turned to zinc oxide? We drive into a “zinc” station, pull out the zinc electrode and replace it with a new one. Now we have a zinc-air fuel cell, ZAFC, with zinc being the fuel we replace. Oxygen in the air is the other fuel.
What happens to that zinc oxide? It’s returned to the plant where it’s converted back to zinc for refueling another vehicle. The ZAFC compares favorably with the hydrogen fuel cell. The latter forms water, a benign compound, and the ZAFC forms zinc oxide, a nontoxic and recyclable material. Zinc also has the advantage that the most of your common “dry” cells, e.g., those ubiquitous AA and 9-volt batteries, have zinc electrodes – we’re comfortable with zinc and know how to handle it.
ZAFCs have received little media attention in spite of some promising results in powering vehicles. The costs of ZFAC technology were not competitive until the recent run-up in gas prices. However, at current levels, ZAFCs become more competitive and several companies have entered the arena with serious programs in the automotive field.
One of the companies is the Electric Fuel Transportation Company (EFTC), which conducted an impressive two-year test of zinc-air powered postal vans in Germany and Sweden back in the late 1990s. A subsidiary, Electric Fuel Ltd., built a full-size (40-foot) bus capable of a full day’s operation on battery power. General Electric cooperated in the development of the propulsion system. The bus was demonstrated in various cities including Washington, D.C. and reportedly received positive responses from the public as well as various government officials. With today’s fuel prices, it may be that zinc-air powered buses will be cheaper to run than diesel-powered buses. EFTC hopes to have a thousand of their buses running in North America by 2013.
A subsidiary of Reveo, Inc. called eVionyx has worked with smaller vehicles. The company’s “Vision” as detailed on its Web site is certainly a laudable one. It points out the problems inherent in the much touted “hydrogen economy” in which hydrogen fuel cells play the key role. The problems include the high cost of producing, handling and shipping of hydrogen. The company’s solution is a “metal economy” in which metals such as zinc, aluminum and magnesium are the energy carriers.
In a zinc metal economy, the zinc oxide from the zinc-air fuel cells would be recycled and converted back to zinc metal by using electrochemical means. The power to do this would be derived from hydro, wind or solar in the ideal scenario. The company envisions using metal-air technology to power small and larger vehicles and has demonstrated ZAFCs in vehicles ranging from motor scooters to cars. In 2000, eVionyx set what they say is the Guinness Book of Records world record of 214.7 miles on public roads for a modified production automobile powered by a metal-air fuel cell on a single charge/refueling.
In 2003 in Malaysia, eVionyx ran a trial of a hybrid Honda Insight, a two-seater car, modified to have an all-electric drive. In this case a zinc-air fuel cell was combined with a nickel-zinc rechargeable battery. The range on public roads was over 300 miles, another world record, according to the BEST article. With ranges of 200-300 miles, metal-air powered vehicles seem a more practical approach than the lamented battery-powered EV1.
Years ago when I was in the battery game, an aluminum-air battery was hot for a while. We used to joke that if we ran out of power we could round up discarded beer cans to power our way home. In a “metal economy” that might not be as ridiculous as we thought.
NOTE: No column next week – Bortrum’s attending his 60th college reunion and visiting his wife’s relatives in Pennsylvania.
Allen F. Bortrum
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