This week, Speaker of the House Dennis Hastert was shown driving off in a hydrogen-powered vehicle, and two blocks later hopping out and getting into his gigantic gas-guzzling SUV. Politicians being mendacious and venal is not news. But, the news continues to refer to the hydrogen “energy source” of the future.
Hydrogen is not and will never be an energy source. It is an energy storage system, like a battery that you can charge with a hose instead of an outlet. And, it’s not a very good replacement for gasoline anyway.
Gasoline stores nearly 10 killowatt-hours worth of power in a liter of space. Liquid hydrogen can only store one quarter that density. What’s amusing is that gasoline actually has more hydrogen embedded in it chemically per liter than liquid hydrogen does. Yes, gasoline is a way to store and transport hydrogen that is more efficient than the raw hydrogen. Brain hurt yet?
If you were wondering about the other alternate fuel vehicles, liquid natural gas (which is an energy source) holds about 75% of the energy per liter as gasoline; liquid propane holds about the same.
So, why do I say hydrogen is not an energy source? Because, unlike natural gas or petroleum or coal, we don’t harvest or discover hydrogen. The way we produce hydrogen today is to create it from other molecules, through electrolysis (splitting water molecules), or microbes exhaling it, or gasification of peanut shells and the like. Regardless, the difference between making gasoline and making hydrogen is pretty stark. We drill for oil, and refine it to make gasoline. This wastes a little energy in the process, but is necessary because crude oil doesn’t explode very well (gasoline does explode under pressure very nicely). Assuming we use natural-gas fired electrical generators to make hydrogen, we would use the entirety of our current natural gas consumption to make the hydrogen to power the current level of transportation that uses gasoline. Shoot, that leaves no electricity for keeping our houses lit and comfortable. Well, whatever shall we do?
Current nuclear reactors are considered low-temperature reactors, and produce mostly hot water as waste. These reactors can produce electricity approximately four times more expensively as natural gas (which explains why nukes are so rare still). A new direct thermodynamic conversion can produce hydrogen with only a 30% penalty compared to natural gas (at least with today’s prices for natural gas – as NG becomes more expensive, nukes become more attractive). Japan, Korea, and China are all working on these and also on pebble-bed reactors. The Japanese estimate they’ll have an operational high-temperature reactor producing somewhere around 100-200 tons of hydrogen per day.
So, those hydrogen-powered cars are actually electric cars with hydrogen fuel-cells storing the energy which was originally produced by burning natural gas or oil, more likely than not. Any time you see “hydrogen-powered” in the news, think “hydrogen-battery electric” instead.