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Thorium and inefficient solar power? That's good enough for me

I'm talking technology, not politics

A load of hot water

Hydro and geothermal have promise: but they're not generally deployable. You can do them in certain places but you can't do them everywhere and there aren't, at least as far as we know just yet, enough places where you can to power us all. There are minor useful sources like biogas but they are, in the face of energy demand, most definitely minor. Biofuels just starve poor people which isn't the aim at all.

Which leaves us really with the big three. Some advocates of fossil fuels like to talk about carbon capture and storage but that meets what is probably an insuperable problem. You end up spending 40-50 per cent of your fuel in the capture of the carbon and this doesn't reduce with scale. So even if it can be made to work (something no one has as yet managed) it's going to be expensive.

Nuclear, uranium type nuclear, many of us here will think that it's just a great idea. Unfortunately many who share the planet with us don't. It may even be true (actually, it is) that the radioactive release from Fukushima is, per hour, half that from the hourly consumption of bananas around the world. But that sort of logic just isn't going to convince people.

Here comes the Sun

Which really leaves us just with solar as the final possible choice. Which could be very depressing: it's expensive and it's intermittent again. We've no decent storage system (batteries would be waaaay too expensive at any scale) and so we might have to do what certain Greens so dearly hope we will do – go back to using energy when it's available rather than this luxury of using it when we want to. Except it is possible to see a system that would indeed work: or at least could do so.

The really interesting point about solar PV is that it's getting cheaper: it's been around 20 per cent a year (or 4 per cent a quarter) for a decade or more. This isn't just reliant on that glut of stuff from China. This is much more like a variant of Moore's Law, and why shouldn't it be? Making a solar cell is analogous to making a computer chip.

We've also got at least one more major design change possible: the switch to multi-junction cells. Use some indium, some gallium, some germanium, all in the same cell in order to collect photons of different energy levels and we can, already in the lab, get efficiencies of 40 per cent. And there's so much damn sunlight falling on the planet that we really wouldn't need to cover much of it at that level to power us all.

Which still leaves us with our intermittency problem. And this is where I rather break step with everyone else. I think that solid oxide fuel cells will be the solution here. They too are subject to a variant of Moore's Law. It is drawing circuits on a chip and we should get better at it over time, so I do expect them to plummet in price over said time. And the system would be to run solar, some electricity is used at the moment of production, some to electrolyse water. Yes, an inefficient process, but that hydrogen is then used to power the fuel cells as and when needed.

Now before an engineer starts shouting at me about how inefficient electrolysis is, I'd like to offer up a reminder that what we actually care about is cost, not efficiency. There's so much energy available that we'd be entirely happy with that efficiency loss as long as it is cheap enough. And that is what I think is going to happen.

Not, obviously, next year. But if the current price of solar PV is $1 per W, which is about the current capital cost, I can't actually see a reason why that won't be 50 cents within the decade and then going on getting ever lower. At which point that electrolysis is going to look pretty good as the basis of our battery or storage system utilising the fuel cells.

Such a hydrogen economy won't work if it's centralised: the problems of long term storage or transport of H2 are just too large. But as a decentralised system, at any one point trying to hold a day or two's worth of hydrogen it could, I think. Which really brings me to the real point of this piece. Above I've given you an outline of my thinking. But you guys know a great deal more than I do about energy and Watts and power and joules 'n' stuff. So why am I wrong, why am I full of it?

If solar gets cheap enough then we'll be happy with the inefficiency of electrolysis as a method of storage and fuel cells as the extraction from storage method. What is wrong with this idea? ®

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