techSunday, December 04, 2005
You may have read about the Israeli company that's developing a car that produces hydrogen from water and (aluminum or magnesium).
The article claims that the car's performance will be equivalent to that of a conventional gasoline burning car. This seems hard for me to believe. The article states that the metal coil required for equivalent range would weigh some 200 lbs. What about the water? Unless the system does not emit the water produced from burning and instead recycles it through the "metal-steam combustor" to again split off the hydrogen, I figure they need about 38 gallons of water to provide the range of a 15 gallon gas tank. If they do recycle the water, the same hydrogen atoms will be used over and over again - combined with oxygen being drawn from the air. In this case the size of the required water reserve is insignificant and the car will actually gain weight as it oxidizes the metal, effectively combining it with the oxygen drawn from the air.
Also there must be some method for initializing the metal-steam combustor. The system requires intense heat to oxidize the metal. This heat is apparently produced by the burning of the hydrogen. There must be some fuel reserve to get the system up to the necessary temperature to oxidize the metal. There could be some kind of hydrogen holding tank which is refilled during oxidation, but it seems that the size of such reserve must be fairly large to allow the system to reach the proper temperature. Also, if the car is shut off before the reserve has refilled, it would be possible to deplete the reserve to the point that the car can't run long enough to begin the oxidation. The other possibility is an electric heater that is powered by a battery which is recharged by an alternator. I am assuming that the metal-steam combustor is very small so that the mass of the combustor could be heated by the electric heater rather rapidly and with relatively low drain on the battery. Perhaps it would be roughly equivalent to the drain required to start a conventional engine. In this case, there may still need to be a hydrogen reserve, but it wouldn't need to be very large.
The main problem that I have with this approach is the efficiency of the oxidation process. How much energy is required to cause the metal to oxidize (with steam alone) at a rate that will produce enough hydrogen to run the whole system and power the car. If it takes more energy to oxidize the metal than is obtained from the burning of the hydrogen obtained from the oxidation, then the system is impossible. It seems, to me, like a fancy perpetual motion scheme.
I could be wrong - I need to do some research on oxidation.
There is very little information (on the internet) about the company Engineuity R&D LTD, the technology they are developing, or the state of the development.
The article claims that the car's performance will be equivalent to that of a conventional gasoline burning car. This seems hard for me to believe. The article states that the metal coil required for equivalent range would weigh some 200 lbs. What about the water? Unless the system does not emit the water produced from burning and instead recycles it through the "metal-steam combustor" to again split off the hydrogen, I figure they need about 38 gallons of water to provide the range of a 15 gallon gas tank. If they do recycle the water, the same hydrogen atoms will be used over and over again - combined with oxygen being drawn from the air. In this case the size of the required water reserve is insignificant and the car will actually gain weight as it oxidizes the metal, effectively combining it with the oxygen drawn from the air.
Also there must be some method for initializing the metal-steam combustor. The system requires intense heat to oxidize the metal. This heat is apparently produced by the burning of the hydrogen. There must be some fuel reserve to get the system up to the necessary temperature to oxidize the metal. There could be some kind of hydrogen holding tank which is refilled during oxidation, but it seems that the size of such reserve must be fairly large to allow the system to reach the proper temperature. Also, if the car is shut off before the reserve has refilled, it would be possible to deplete the reserve to the point that the car can't run long enough to begin the oxidation. The other possibility is an electric heater that is powered by a battery which is recharged by an alternator. I am assuming that the metal-steam combustor is very small so that the mass of the combustor could be heated by the electric heater rather rapidly and with relatively low drain on the battery. Perhaps it would be roughly equivalent to the drain required to start a conventional engine. In this case, there may still need to be a hydrogen reserve, but it wouldn't need to be very large.
The main problem that I have with this approach is the efficiency of the oxidation process. How much energy is required to cause the metal to oxidize (with steam alone) at a rate that will produce enough hydrogen to run the whole system and power the car. If it takes more energy to oxidize the metal than is obtained from the burning of the hydrogen obtained from the oxidation, then the system is impossible. It seems, to me, like a fancy perpetual motion scheme.
I could be wrong - I need to do some research on oxidation.
There is very little information (on the internet) about the company Engineuity R&D LTD, the technology they are developing, or the state of the development.
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It may seem like a fancy perpetual motion scheme, but not quite. When you read the article, you may have missed that the metal-steam combustor produces waste in the form of metal oxides (solids which can be recycled) so after a while you'd need to change the magnesium or aluminium in the combustor. A perpetual motion machine would not produce any waste. I think the boron fuel article above sounds more promising.
In other words, the O2 formed by splitting the water molecues is lost to the metal in the combustor. New O2 (from the air probably) must be added to burn the hydrogen. When that water is sent back for splitting, the O2 is lost to the metal, and still new O2 needs to be added. A perpetual motion machine would reuse both O2 and H2.
This does eliminate the problem of storage and transportation of H2, which is a huge consideration. What I would like to see is an analysis of the collection and recycling process for the metal oxides. The boron fuel article provides such an alalysis as part of its argument. Also, your point about the mass of water was a good one, but also there is the additional mass of the metal-steam combustor and the associated collection chamber for its waste. Is the energy density of H2 enough greater than that of gasoline to offset this increase in mass? I don't know, and the article didn't say, beyond the vague claim you mention.
This does eliminate the problem of storage and transportation of H2, which is a huge consideration. What I would like to see is an analysis of the collection and recycling process for the metal oxides. The boron fuel article provides such an alalysis as part of its argument. Also, your point about the mass of water was a good one, but also there is the additional mass of the metal-steam combustor and the associated collection chamber for its waste. Is the energy density of H2 enough greater than that of gasoline to offset this increase in mass? I don't know, and the article didn't say, beyond the vague claim you mention.
Yes, I realize that it's not actually perpetual motion - it just seems a bit fishy that way, like it would take nearly as much (or more) energy to oxidize the metal (intense heat required), than would be gained from burning the hydrogen
After writing the post (or perhaps while writing the post, but I didn't mention it), I realized that effectively, the car isn't burning hydrogen at all, it's really "burning" the metal in a roundabout way.
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After writing the post (or perhaps while writing the post, but I didn't mention it), I realized that effectively, the car isn't burning hydrogen at all, it's really "burning" the metal in a roundabout way.
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