God, I love writing about renewable energy. (Moan)

I keep seeing a statistic being thrown around by advocates of renewable energy: "20% of our energy already comes from renewable sources".

Well, yes, that turns out to be true. But they're palming a card when they say that.

There are two kinds of renewable energy: hydro, and sources which can't be used for base load. When they say 20% of our energy comes from renewable sources, it's true, but nearly all of that is hydro.

Hydro is very practical and there is a lot of it. We've been using it for a hundred years, and, unfortunately, nearly all the potential hydro has now been developed. It's not an infinite resource, and to get much more we'd have to do things like turn Hell's Canyon into a lake.

The Columbia River is probably the single biggest source of hydro power in the US, and there's only one site remaining on the Columbia where a new dam could be built. The government made a conscious decision not to use it because it's the last remaining stretch of wild water on the river, and they decided to preserve it.

The Mississippi contains more energy, but it can't be dammed for most of its length. The terrain is wrong for that. (Also true for the Missouri.) The Colorado is fully developed, and it doesn't actually produce all that much power because it doesn't actually run all that much water. (My local river, the Willamette, runs 50% more water.) The main reason the Colorado is so valuable is that it runs right through the middle of the biggest desert in North America, so it's a prime source of irrigation and tap water. (And all of it gets used. It's been decades since the Colorado reached the sea. It dries up 10 or 15 miles short.)

The Rio Grande is similarly overutilized, and there have been times when it hasn't reached the sea, either. And it doesn't run enough water to be worth using for hydro. There just isn't much power there. (It's less than our Santiam River, which none of you have even heard of.)

The St. Lawrence river and the other large rivers in the NE (e.g. the Connecticut river) are like the Mississippi; the terrain they run through doesn't permit dams to be built.

There are a lot of decent rivers in Quebec which have been dammed, and the power they produce is mostly sold to the US.

So yeah, 20% of our power comes from hydro. But it isn't going to increase any more, and as our energy use increases, it will make up a smaller and smaller proportion. By 2050 it will probably be less than 10%.

And the other kinds of renewable energy are too intermittent and/or unreliable to be used for base power. (What do you do in the middle of the night when the wind isn't blowing?)

I hate this, but seeing that factoid over and over again got my temper up. It's so deceptive as to approach an outright lie.

UPDATE: "So you use intermittent energy sources and store a lot of it, and use the stored power when the primary source can't be used."

The problem is that storing vast amounts of energy isn't easy. I know of only one practical way of doing it that can handle the amount of energy needed, which can consume or produce power at the kinds of rates needed.

You use excess electricity to run pumps and push water up to a reservoir or a system of tanks at the top of a hill. When you need to get power back, you run water back down the hill and push it through a turbine. Leakage is negligible; we know how to build tanks that don't leak. So the water can be stored at high elevation for however long is required.

Siting is a bit of a headache, but not too bad. You need a reasonable hill or small mountain next to a reasonable river (which runs ten or more times your pump rate). But there are a lot of places like that. (Of course, such sites are nowhere near where people propose to build big solar plants.)

That works, and it scales nicely. Need more capacity? Build more pumps, tanks, and turbines. The reason I don't like it is efficiency: most of the energy put into it to pump the water is lost. You only get a minority of the energy back at the end.

"So make it more efficient" says the renewable energy freak who hasn't heard of the Second Law of Thermodynamics. It can't be made super efficient. The laws of Physics don't permit it.

And that's true for any energy storage system which is large enough to make a difference. Which means it isn't a practical solution.

Posted by: Steven Den Beste in Weird World at 03:07 PM | Comments (9) | Add Comment
Post contains 811 words, total size 5 kb.