Will Storage Discovery Make Hydrogen-Powered Cars a Reality?
Two problems face those who want the lightest element, hydrogen, to be the transportation fuel of the future. One is finding a way to store it and there MAY be new hope in that area. The other, of course, is just where the hydrogen will come from (see below for a note on this).
Hydrogen seems as if it would be the perfect fuel for cars using fuel cells. Simply feed hydrogen and air into the cell and water comes out. But compressed hydrogen is incredibly dangerous so a new way to store it in a car is essential.
The problem with hydrogen is that to store very much energy you need extremely high pressures which make the "fuel" tank very dangerous. The best way to carry large quantities around safely is by having it stored in some sort of metallic sponge.
Photo: Department of Energy
A useful fuel tank would need to store about 4% hydrogen by weight and also release it, both at reasonable temperatures.
Chinese and American researchers announced in a recent paper that they have found a way to do this.
(Kun Lü, et al. "Sc-phthalocyanine sheet: Promising material for hydrogen storage." Applied Physics Letters 99, 163104 (2011). DOI:10.1063/1.3653465)
The material will hold 4.6% hydrogen by weight, exceeding the U.S. Dept. of Transportation goal of 4.3% and will do it at 283 degrees Kelvin, or about room temperature, and at a reasonable pressure of 100 bars (1400psi.). (One bar is about sea level air pressure.)
So far, so good, but there may be a fly in the ointment, the same one which faces virtually ALL proposed green technologies - the material uses a rare earth element - Scandium.
China, as has been well publicized, owns most of the world's supply of rare earth elements and is planning to use most of it for domestic production.
Refueling a government forklift
Photo: Department of Energy
But linked to supply problems is the price which will tend to go up as demand increases. Just a few years ago you could pick up a Kilogram of Scandium for about $1600, the 2005 price was $70/gram. A recent price quote was $270/gram, or about $120,000 per pound.
When you factor in the low current demand - a small amount is used in high intensity lights or in an alloy of aluminum - you can see that although the new material has nice physical properties, the financial realities mean it probably won't be used in 5-10 million cars anytime soon.
Even if the problem of storing hydrogen is overcome, there remains the basic problem of just how to get the hydrogen. You can't mine it any place closer than Jupiter. Generating hydrogen is easy either using a catalyst and common hydrocarbons (which leaves the carbon) or from water - simple, just pass electricity through some clean water - lots of kids do that in high school.
One slight problem if you want hydrogen to reduce the carbon footprint of cars and trucks - where do you get the electricity? Today we get it by burning coal, oil, and natural gas - include the losses involved in converting one energy storage source to another and using hydrogen to power cars means MORE carbon in the air, not less. TANSTAAFL gets you every time.
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