Sunday, March 27, 2011

Nukes and artificial leaves

Ah, it seems my original ambitions fell a bit short and its been a year since my first post. Oops. Lets hope I can do better in the future.

My thoughts have been turning to energy this last week, mostly due to the Fukushima nuclear power plant problems. I'd briefly considered putting "power plant disaster" there, but the scope of the damage from radiation seems so relatively small that it feels like doing so would trivialize the tsunami. Some back of the envelope calculations make me think that even if you assume a linear no-threshold dosage model for how radiation causes cancer (i.e. the silly conservative assumption) the plant meltdown will end up causing some tens of cancers.

I'm generally a supporter of nuclear energy. Its a lot better than, say, coal which in the US kills tens of coal miners each year, and over ten thousand people through pollution. Its certainly possible to do better than that, but its possible to make nuclear plants much safer as well. Nuclear power does produce radioactive waste and its impossible to make that waste perfectly safe... but its not very hard to make the waste far safer than the Uranium ore that was mined to create it. I mean, Uranium ore is just sitting near the surface in Colorado where it can get into groundwater and everything.

But realistically, I suspect that after Fukushima there is little hope for the development of new nuclear reactors in the US any time soon. But really, I'm starting to think that renewable energy might just end up being good enough in the long run. And by long run I mean fifteen years or so. Here is a very nice article from Scientific American about how much solar electricity has been improving. They say that the cost of generating solar electricity will be as low as what consumers pay by 2021. This is misleading for a few reasons: first the cost that consumers pay includes things like transmission as well as generation and second its when solar gets as cheap as what we have now that it becomes economical to start building solar instead of oil or whatever, not to rip up all our existing fossil fuel infrastructure. But the point stands that even if photovoltaics are impractical at the moment, it seems likely that their time will come.

In the shorter term, natural gas is the least bad of the fossil fuels and we've recently discovered that the US has much more extractable gas than previously thought. Wikipedia mentions a hundred years worth, but if we're going to cut down on coal use that number is going to have to drop. Still, things are looking much better there than there than they were a few years ago.

And then there's the artificial leaf that some researchers at MIT have announced recently. It is apparently "10 times more efficient...than a natural leaf" which would put it somewhere around a 30% energy conversion, since wikipedia says that photosynthesis is usually 3-6% efficient. That isn't great compared to solar cells, until you realize that this elides all the inefficiency involved in storing the energy a photovoltaic produces. This isn't the only technology we need to develop before hydrogen powered cars become feasible, but it was the one I would have been most skeptical about. It still remains to be seen how economically these things can be produced in bulk, but in the long run I'm optimistic.

2 comments:

  1. I just wrote a long comment and Blogspot ate it. Let me test this before I try to re-write it.

    ReplyDelete
  2. I haven't read any of the information about the artificial leaf, which embarrasses me given that it's fairly close to my field of research. That said, it seems appropriate to bring up something that a chemistry professor I knew as an undergrad said about similar research he was doing:

    We know how to make hydrogen fairly efficiently from electricity, but even if we had a cheap, clean, renewable source of electricity (i.e. cheaper photovoltaics), it is unlikely that it would make a sufficient basis for a hydrogen energy economy, because electricity is a particularly high-value form of energy at present, and petroleum is still fairly cheap, so there would be a preference for selling cheap solar electricity to the grid or using it for high-consumption industrial uses like the Haber process or refining aluminum over using it to make fuels.

    Thus, if we want to try to create a hydrogen economy now--before we push global warming past a threashhold-of-no-return--what we need is a way to convert solar energy directly to hydrogen without electricity as an intermediate.

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