Measured Against Reality

Monday, December 17, 2007

Hydrogen follies

This video of a solar-powered hydrogen generator got me thinking about something I've been wanting to write for a long time: why hydrogen is stupid.

It all comes back to one principle: everything is a battery. Any source of energy that we have is essentially just energy from the sun repackaged. Solar is obvious, but even biofuels, wind, oil and coal are (oil and coal are from plants, and wind is from pressure differences from heating, although some is probably from the earth's rotation). The only exceptions to this rule are geothermal and nuclear, (and geothermal is really nuclear, radioactive decay is what heats the earth), but neither of those can power the world.

Why does this matter? I think it matters because when you realize that no matter what we do, we're taking energy from the sun and storing it a battery of some form, certain types of fuels just stop making sense. Hydrogen has so many problems beyond this it hardly merits mentioning, but it's also the cleanest parallel. Hydrogen is a really bad battery, it stores about 40% of energy that comes into it (meaning if you use 100 J to separate water into hydrogen and oxygen, then burn the hydrogen to get water and energy, you'll get about 40 J back) (you might wonder where these numbers come from, which is a presentation I saw last year. I can't find them online, take them with a grain of salt. The point still stands that electrolysis will always be less efficient than a simple battery for energy returns, some other way of generating hydrogen may be better than electrolysis, but then all the other problems with it remain). Considering that current batteries are much, much better than that (and getting better), hydrogen just doesn't make any sense. Even more so when you consider that we'd still need to get energy from somewhere to separate the hydrogen from something (currently it comes from natural gas), and it's not an energy-generator, just a battery.

Biofuels are just as stupid. We're using plants as solar-cells, then chemically modifying them into batteries. Why not just use solar cells and batteries? Those can be placed anywhere, and we don't have take precious food out of the world's farms for fuel (which, by the way, is part of the reason food prices are at all-time highs). Biofuels may be promising in some regards, but I don't think we'll ever be able to generate appreciable amounts of fuel with them, simply because we'll run out of arable land, even if we turn the entire earth into a large farm (which would be beyond stupid).

My simple point is this: all of our energy ultimately comes from the sun, so we should collect it directly and store it in the best possible medium. We should still research and consider other methods, but I'm convinced that none of them will prove tenable.

3 Comments:

  • It's true that hydrogen isn't particularly efficient, but energy efficiency isn't the only concern. Theoretically, hydrogen fuel cells have other desirable qualities. (In practice, hydrogen is still a new enough idea that it barely works at all. On the other hand, about a century ago you could have said the same thing about gasoline-powered internal combustion engines.)

    A battery takes a lot of resources to make. In fact, the more efficient the battery, the more exotic the materials involved. The process of manufacturing a battery generates a lot of toxins, and sooner or later, a battery turns into a little chunk of toxic waste, which requires special handling. (And a lot of little chunks of toxic waste add up very quickly. Most desktop computers contain a little tiny battery to serve as backup for the clock. These things are miniscule -- but there are millions of computers!)

    Hydrogen fuel cells, at present, have some exotic components. But the waste product of the fuel is, famously, water [vapor], rather than some heavy-metal-bearing corrosive compound. Furthermore, a fuel cell tends to degrade more slowly than a rechargeable battery; even the best battery will eventually hold less power than it did when it was new, while a fuel cell will keep converting fuel to power at about the same rate for a long time. Even given the potential toxicity of worn-out fuel cell components, they represent less of a problem than batteries do.

    Furthermore, most rechargeable battery technologies don't play well with variable power sources; the less reliable the current is, the more power is lost in charging the battery. (Because you have to keep tinkering with it to tune it into the battery's accepted range, with power loss at each step.) A fuel cell, on the other hand, burns its fuel at a steady pace; it doesn't care how quickly it was generated. So if you hook a battery up to a solar cell, you may not get very good results if it's a cloudy day, but a fuel cell won't have any problems with fuel that came from a solar cell.

    By Anonymous Anonymous, at 3:29 PM, December 17, 2007  

  • All very good points, my only real response would be that I expect technology to advance faster for chemical batteries than hydrogen, but technological advances are pretty much unpredictable. I guess in 20-30 years we'll see what the best course of action was, and why it was oh-so-obvious.

    By Blogger Stupac2, at 3:51 PM, December 17, 2007  

  • Biofuels have the advantage that they don't require us to build new types of cars. In Europe (well, at least in Germany) a lot of gas stations already offer biodiesel that can be used by any diesel car (admittedly, those cars are not as common in the US...though they should be, but that's a different story).

    By Anonymous Anonymous, at 11:38 PM, December 18, 2007  

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