Hydrogen on Demand
Two of the biggest hurdles to switching to hydrogen-powered equipment, from lawn mowers and chain saws to cars and trucks have been transporting and storing the hydrogen. But what if that wasn't a problem? What if hydrogen was produced on an as-needed basis from a chemical reaction?
That's the subject of new research from Purdue University. The engineers have developed a method that uses an alloy of aluminum and gallium which reacts with water to produce hydrogen. That hydrogen could then be fed directly to an engine. The gallium prevents the aluminum from oxidizing which allows the reaction between the aluminum and water to continue until all the aluminum has been converted to aluminum oxide. The waste products? Gallium, which can be recycled, aluminum oxide, and water. The aluminum oxide can also be recycled, but electricity is required for that process, called salt electrolysis. To make the process carbon neutral, that electricity would need to be generated by a carbon-free source such as nuclear or wind power.
Comments (7)
Gallium is only found in trace amounts (
There is a fairly large amount of gallium associated with the bauxite ores, but you have to mine the bauxite to come up with the additional gallium. So, there is a rather hefty investment in startup costs for aluminum-gallium alloys. You also need to factor in the energy needed to process the bauxite (1050 deg C temps needed) and the electricity needed in the smelting of the alumina ore. If you use recycled aluminum for the pellets, you're not going to need as much aluminum from bauxite thus reducing the supply of gallium. Since there is no primary source of abundant gallium, the initial gallium source to supply this fuel source is going to be quite large.
Let's say that you fill your tank up with 350 lbs of aluminum-gallium alloy (350 lbs). The remaining cars in the US (144,000,000 or so) will also need that amount. So that is 24.5 lbs of gallium per tank times 144,000,000 cars is a bit over 3.5 billion lbs (1.764 million tons) of gallium to fuel just the cars in the US. Current world production of gallium is 160 metric tons with a recycling capacity of 73 metric tons, annually. (http://minerals.usgs.gov/minerals/pubs/commodity/gallium/gallimcs07.pdf)
In order to get the first tankful in just the cars in the US we are going to have to increase our gallium production by a factor of about 11,000. Oh,the US produces exactly 0% of the world's supply of gallium with 37% coming from China and 10% or so from Russia.
At this point in time, I think we have some major supply hurdles to overcome before we can use this technology.
Posted by Paul | May 21, 2007 7:43 PM
Nice thing to continue researching, since Woodall himself points out the usual problems that all alternative fuels share. It isn't economical at this time and expanding it to industrial scale would cost even more. It also isn't as efficient as gasoline by far.
However, this does look real promising if some of the other problems with fuel cells can be solved. Fixed generation applications would be interesting.
Posted by Kamatu | May 21, 2007 9:58 PM
This idea ROCKS!!!!
That is all....
Posted by plish | May 21, 2007 10:27 PM
Sorry, looks like part of the first sentence was left out of the post above. It is supposed to say,
Gallium is only found in trace amounts (less than 50 ppm) in bauxite (an aluminum ore), sphalerite (a zinc sulfide), various other minerals, and in flue dust (fly ash from coal oxidation).
Posted by Paul | May 22, 2007 9:47 AM
Another omission.
The article did not give us the composition of the alloy, but I found a website that sells aluminum-gallium alloy with a composition of 93 percent aluminum and 7 percent gallium. Aluminum currently sells for around $1.11 per pound and purified gallium sells for approximately $227 per pound. The article states that a 350 mile trip would take approximately 350 lbs of the alloy and would cost $60 for the trip. I did my own calculations and came up with a cost of a little over $5900 for the trip. Of course that's using 99.9999 percent pure gallium.
Next time I'll preview my posts. Sorry.
Posted by Paul | May 22, 2007 9:55 AM
This are exactly the kind of innovative research we need to solve problems. Running around hand ringing and pointing fingers gets us nowhere.
Paul- You bring up good points, but remember when cars were first being built there were major problems with refining enough fuel to supply the new demand. In fact gasoline was considered a solvent and not a fuel. There also were a lack of stations to fuel up at but entrepreneurial people saw the need for them and they capitalized on the new market. Nobody claimed supplying gallium or aluminum would be easy or cheap. Great minds think outside the box and come up with solutions to problems others think are insurmountable.
Posted by SM | May 22, 2007 9:59 AM
SM,
When I first read the article, I thought that it sounded almost to good to be true. The big problem here is a plentiful supply of gallium. Given the current attitude about mining and energy consumption in the world, this sounds like a fairly energy intensive venture that would meet with a fair amount of resistance. I would bet that many would oppose the mining of aluminum (bauxite) to produce an adequate supply of gallium. Sphalerite (zinc sulfide) mining is despised probably more than bauxite mining. If you can think of a way to produce gallium through alchemy, more power to you. But gallium seems to be the limiting factor in this process and trust me, there ain't no way you can make gallium more plentiful without digging it out of the ground one way or the other.
Posted by Paul | May 22, 2007 1:35 PM