A mere factor of two

Kevin Drum does some vague noodling on energy matters:

[V]irtually every form of energy seems to be almost as efficient as burning oil, but not quite.

For example, on either a power/weight basis or a cost basis, batteries are maybe 2x or 3x bigger and less efficient than an internal combustion engine. Not 50x or 100x. Just barely less efficient. And you see the same thing in electricity generation. Depending on how you do the accounting, nuclear power is maybe about as efficient as an oil-fired plant, or maybe 2x or 3x less efficient. Ditto for solar. And for wind. And geothermal. And tidal power.

I’m just noodling vaguely here. Maybe there’s an obvious thermodynamic explanation that I’m missing.

Let’s give everything the benefit of the doubt and say that it’s a straight 2x across the board. (If we were being rigorous about the whole thing, we’d never say “2x less efficient”; we’d say “half as efficient,” which is at least as accurate and a lot less clumsy.) Now: based on six years’ experience with my current ride, I have determined that I can drive to and from work, one round trip, on one gallon of gas, which as of yesterday at the Shell station at 36th and Portland was $3.64. (V-Power, you damn betcha.) I will be the first to tell you that internal-combustion engines are not particularly efficient, for which there’s an obvious thermodynamic explanation. However, I cannot, and will not, feign any enthusiasm for any technology or policy which increases my costs to $7.28 or beyond.

Warren Meyer attempts to explain how Drum could come up with this sort of thing:

[I]n engineering, a 2-3x difference in most anything — strength, energy efficiency, whatever — is a really big deal. It’s the difference between 15 and 45 MPG. Perhaps this is Moore’s Law corrupting our intuition. We see electronic equipment becoming twice as powerful every 18 months, and we start to assume that 2x is not that much of a difference.

Our “energy policy,” and I use the term loosely, is seldom if ever left up to engineers: instead, the task is farmed out to policy wonks with a capacity for vague noodling and an enthusiasm for evangelizing beyond anything you’ll ever find in a young-earth creationist. I’m surprised the two groups haven’t combined their efforts yet: “It takes many thousands of years for organic matter to turn into oil, and, well, the Earth is barely six thousand years old. No wonder we have no oil.”


  1. McGehee »

    6 May 2012 · 9:34 pm

    Internal combustion engines are more efficient than electric engines for one fairly obvious thermodynamic reason: the power in the batteries is made through internal combustion, and then must be transmitted through the grid to the vehicle that’s going to use it.

    Friend Drum might want to check out Conservation of Energy for more detail. Suffice it to say that doing the internal combustion onboard eliminates a lot of opportunities for entropy.

  2. Barks in the Country »

    10 May 2012 · 10:39 am

    Finally, someone else offended (however mildly) by the use of ‘2x less’. This peculiar construction seems to be used by younger people. It may have something to do with the government schools absenting themselves from teaching mathematics, to say nothing of graceful writing.

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