Work on still another idea, which seems to be something of a breakthrough, was reported in early October by Lawrence Livermore National Lab (LLNL) scientists in four papers given at a meeting of the Electrochemical Society in Hollywood, Fla. (following previous papers given at the Intersociety Conference on Energy Conversion in Seattle, August 1980.]
The cell uses aluminum, air and (tap) water, and its developers call it a battery
¾which it is, in the sense that no fuel is fed into it continuously from the outside. Yet we would rather look at it as a fuel cell, for what seems more important is that its energy can be replenished almost instantaneously by inserting new fuel rather than charging it electrically. But let's not quibble and just call it a power cell.Like other fuel cells and batteries, this cell makes hydrogen (hydroxyl) ions flow to one electrode, and positive ions to the other, the flow of electrons through the external circuit completing the current loop. But the chemistry is different from other cells: Caustic water plus oxygen (from air pumped through the cell) combines with aluminum, producing electricity, and leaving a reaction product called hydrargillite [chemical formula Al (OH)4], which is recyclable; in fact, it is a product regularly used in the manufacture of aluminum.
GRAPHIC: A11_8001.TIF
This reaction product is formed and collected by a crystallizer to prevent it clogging up the cell.
As the reaction proceeds, the aluminum plate (16 by 10 by ¾ inches) is uniformly eaten away and becomes thinner. Eventually a new aluminum plate must be inserted
¾a 15 to 30 minute job. Depending on the thickness of the plates used, this would have to be done only every 1,000 to 3,000 miles of driving, a frequency comparable to today's engine oil changes. Otherwise, the vehicle consumes only water (and air), and a supply of 6 gallons will last from 250 to 500 miles of driving, at which time the car must stop to tank up on fresh (tap) water.The primary energy put into this power cell is electrical: Aluminum is an energy intensive product manufactured from bauxite and other raw materials by consuming large amounts of electrical energy. Thus, the energy is carried into the car via an aluminum plate rather than via an electric current that charges the battery.
LLNL's schedule calls for a vehicle powered by the air-aluminum cell to be on the road by 1989, though it is thought that with an accelerated program it could be ready by 1986. There are, of course, drawbacks, primarily economic. "No car can beat the cost and performance of a gasoline-powered car," says Dr Ervin Behrin, who manages the metal-air research jointly with Dr J.F. Cooper. Operation of a vehicle powered by this battery will not become competitive until gasoline costs $2 to $3 per gallon.
But it would certainly remove the major disadvantages of conventional battery-powered cars. Its range is virtually unlimited
¾even the water replenishment is done at twice the range of lead-acid battery recharges, and in seconds rather than hours.But the decisive advantage is given by the energy and power densities of the cell. The aluminum plate packs about six times the energy content of gasoline per cubic inch, and 10 to 15 times the energy of a lead-acid battery per pound. As for power density, it produces enough power (rate of energy flow) to handle acceleration on its own
¾and that is the point where the hydrogen-oxygen fuel cell car needs the help of batteries, and where a battery-driven car needs the help of a flywheel if it is to accelerate reasonably well.Transportation is one of the major items in the US energy budget, consuming about 26% of all energy, and about 54% of all petroleum products, so that any type of transportation running on fuel other than petroleum is of great interest. But this one, we feel, is particularly hopeful, since it promises hitherto unattained energy and power densities, a point of deep significance as shown in the following item.
[Sources: LLNL news release of 8 Oct 1980, preprints of papers given by LLNL scientists at meetings in Seattle, Wash., and Hollywood, Fl., as mentioned above, and private communication with Dr Ervin Behrin.]
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Vol. 8, No. 3
Newsletter: Access to Energy Newsletter Archive Volume: Volume 8 Issue/No.: Vol. 8, No. 3 Date: November 01, 1980 04:18 PM Title: Electing peace
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