The gun blogosphere is pretty quiet today, so I thought I’d take some time to take a look at a new technology. While I’m a gun blogger normally, by training and profession I’m an engineer, so this will be a rare occasion when I get to use that skill in the blogosphere.
Instapundit points to a technology that claims to be able to make hydrogen from magnesium and water. This is interesting, but I consider this another example of a company cashing in on the alternate fuel craze. The big reason not to get excited about this is the second law of thermodynamics will always demand that you lose. You will need to put more energy into cleaving the water molecule into hydrogen and oxygen that you will ever get back from putting it back together either by burning it in a conventional internal combustion (IC) engine or fuel cell. In short, this system is essentially turning magnesium into an energy source, with hydrogen as an intermediary, to be turned into a usable form of energy in a fuel cell or IC engine. Interesting idea, but is magnesium cheap enough and sufficiently energy dense to be a practical motor fuel?
Magnesium seems to cost about $2.75 per kilogram. A kilogram of magnesium contains about 24.7 megajoules of energy. To compare to gasoline, we really need to measure energy by volume, which is 43 megajoules for a liter of of magnesium, compared to 34.6 megajoules for a liter of gasoline. Magnesium wins on energy density!
A liter of magnesium has a mass of 1.74 kilograms, and a cost of $4.79 based on recent pricing. It would take 1.24 liters of gasoline to have the same amount of energy that’s in a liter of magnesium. Gasoline in my area is about $2.60 a gallon, which comes out to about 69 cents per liter. Therefore the energy equivalent for gasoline comes out to cost 86 cents, compared to magnesium’s $4.79. So magnesium costs about five and a half times what gasoline does if you use equivalent energy.! If you do the unit conversions, to get the same amount of energy that’s in a gallon of gas, it would cost you $14.48. A little pricey for driving the kids to soccer practice, wouldn’t you say?
Also consider this is based on the current price of magnesium. No doubt common use of magnesium as a motor fuel would drive the price through the roof. Magnesium mining also requires energy, and is not exactly environmentally friendly.
So unless Ecotality has found a way to get around the second law of thermodynamics, this technology is a dead end. I’m sure the government would gleefully throw lots of grants (tax dollars) in their direction, but I certainly wouldn’t invest.
My source material was largely this Wikipedia article on energy density, plus a little Googling for prices. Someone go ahead and check my math if you want.
UPDATE: Glenn updated the article with a bit from a chemist who reveals where the energy is going in the process; making the elemental magnesium in the first place, and then recycling the oxides back into free metal.Â If you submerge magnesium in water, it will react with the water as a matter of course, releasing hydrogen. Â Didn’t know that.Â My background isn’t in chemistry. Â But the physics still says you lose.