Wednesday, December 2, 2009

Stop with the hydrogen already, it's stupid.

I love hydrogen, really I do. It's a prime ingredient in the biggest bombs we can make. It makes a wonderful bang when you fill a balloon with it and then poke it with a match. It burns clean, producing nothing but chemically pure DHMO. But for the love of god, stop with the 'hydrogen economy' crap. It's terribly inefficient. Don't take my word for it, go ask a physicist.

Electric transportation is the way of the future, and it's awesome, but we need to ditch this fixation on hydrogen. Fuel cells are good for two things: Sounding cool, and distracting the public from battery electric vehicles. This whole hydrogen thing was started by car manufacturers back in the late '90s so they could look like they were saving the environment while they continued to build lounge-room-sized SUVs, and it was encouraged by the U.S. government because they couldn't figure out how to appropriately tax EVs. Petrol taxes elegantly combine paying for road wear caused with an incentive for efficiency by the vehicle in a way that is nigh impossible with EVs. But I digress.

Let's face it, physics is not on the side of hydrogen. First, you have to generate the hydrogen, which today is generally done by processing 'natural gas', the primary source of which is fossil fuels. Yes, your hydrogen fuel cell car will run off dinosaur farts just like your old banger does now. The only carbon neutral sources of hydrogen are processing biogas (unlikely to ever provide the quantities required) and electrolysis of water, which in the very best case is still less than 50% energy efficient.

Next, once you have your supply of pure hydrogen, you have to store it. This bit is a pain in the ass. The main technologies we currently have for hydrogen storage are high pressure tanks, cryogenic storage, and storage as metal hydrides. Compressing hydrogen to between 350 and 700 bar. for high pressure storage requires a large energy input, which is wasted as heat when the hydrogen cools to ambient temperature after compression. Cryogenic storage requires similar energy inputs to both compress and cool the hydrogen. Metal hydride storage systems are safer than high pressure systems but are heavy and require heating to 120-200°C to release the stored hydrogen.

Now, you can get to the cool bit, which is recombining the hydrogen with oxygen to produce actual turning of wheels and so forth. The only problem is that by now, less than a quarter of the energy you had in the first place is still available to you in the form of hydrogen. 75% of that energy is gone.

Compare this with a battery electric vehicle running with nanophosphate lithium batteries. Charging and discharging the battery requires power electronics which are typically around 80-90% efficient. Other than that, energy losses are minimal. Overall, a hydrogen infrastructure would require around three times as much input power as a battery-based infrastructure. And that's terrible.

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