Stardate 20040604.1353

(Captain's log): I guess I should have predicted this. Every time I talk about energy generation, the letters pour in suggesting innovative/cool/strange alternatives which the letter writer thinks might actually solve the problem. Usually I try to write back to point out one or two major reasons why it won't, but then they will answer those objections (they think) and triumphantly ask, "So now what do you think?"

Since my original list of objections wasn't exhaustive, about all I can do is to wearily point out other objections which I hadn't bothered listing in the previous letter.

For instance: why not put a solar power plant on the moon instead of in geosynchronous orbit? Because it would be in darkness half the time, and because it would no longer hang over the power receiver on earth, so even when it was in sunlight it would only be able to beam power down about a third of the time, and because the moon is a lot further away so the power beam would spread more and cover a much bigger area which would increase wastage and potentially affect the health of people living there, and because the moon is a lot further away and the cost of putting such a facility on the moon would be even greater, in money and energy, than putting it in geosynchronous orbit. And even that is not an exhaustive list. I did not, for instance, mention any issues relating to security and the hazard such a system would represent if it malfunctioned or was taken over by inimical forces.

James wrote to me suggesting that wind power and/or some sort of terrestrial conversion of solar power actually can be scaled up enough to make a difference.

I responded by linking to another article of mine not included in the last post about this. What that article discussed was the fact that electric power has unique properties, and one of the most important is that at any given instant the amount of electric power being generated will always exactly match the amount of power being consumed. If you don't deliberately balance the system, the laws of physics will do the balancing for you in ways you won't like.

Electric power has to be generated at the time it is needed, and the electric power grid overall has to have the ability to add generation capacity as demand rises, and to reduce generation when demand falls again. Demand actually rises and falls by as much as 30% every day.

The biggest drawback of wind/solar is that they generate power when conditions permit them to do so, not when demand requires them to do so. And there's no practical way to store electric energy in adequate quantities to deal with this without unacceptable losses or unreasonable capital and/or operating expense. (This is a major flaw of most of the fad alternate electrical energy sources we hear so much about.)

It is by no means the only serious objection I have to solar/wind, but it is a major one and was the only one I listed in my response to him.

James thought that could be solved by tacking on another piece. He responded, in part:

The really large scale solar/wind power generation model assumed some big invention in storage. I suggested it in the same spirit as you suggested your 40km deep geothermal idea. Which will be more practical in the future? A machine that converts CO2 + water + electricity into methane/propane/hexane, or the really deep hole that produces steam? Certainly not obvious to me.

I don't think James is looking at this the way an engineer must look at things. (Engineers have a term for pieces added to a system to fix existing problems which create entirely new problems at least as severe. We call 'em "Kludges".)

The last time I got involved in discussing alternative energy sources I kept running up against the fact that most of my readers didn't understand the scale of the problem, and didn't understand the fundamental problem of scaling.

Something which may work really well at one scale may not work at all well when scaled up 6 orders of magnitude, even if it is possible to scale it up that far.

For instance, in the last article I mentioned that there would be huge losses involved in conversion of electricity in a solar power satellite into microwaves for downlink. TMLutas found an online reference to a circuit which was able to convert DC to microwaves with 90% yield. That's all well and good, but their approach was designed to operate at 20 watts. It isn't possible to scale it up nine orders of magnitude to 20 gigawatts.

"Converting electric power, CO2 and water into methane" is certainly an appealing idea. I don't think we actually know how to do that now with anything like an acceptable yield, if we know how to do it at all. But as James says, we presume that one result of the "Energy Manhattan Project" is development of such a technology. Unfortunately, as tough as that might be, it's the easy part.

What would we need to design and build in order to implement that technology at useful scales? In one of the articles linked last time, I defined "useful scales" as being average power levels at least 1% of current US power consumption. The US right now consumes about 3.3 terawatts of power average, and any energy technology which can't deal with 1% of that will have negligibl