Daniel Nocera tells James Mitchell Crow about harnessing solar energy to make fuel from water
Daniel Nocera tells James Mitchell Crow about his research into harnessing solar energy to make fuel from water
Could you briefly describe your own research?
My research is pretty easy to describe: water + light = oil. It is literally to figure out how to get light to act on water to split it into hydrogen and oxygen, which you can then use as a fuel.
Are there many groups working on this problem?
There are other groups working on it, but not enough, and that’s what holds solar back. The way that science works, and this is what makes it beautiful, is that a discovery can come from anywhere. So if you want to up the ante in terms of discovery, you want to have as many people working on the problem as you can. There’s a lot of really bright young people who could be working on it, but they don’t because the money isn’t there for them. I wish I had 150 competitors, because that’s in the end how this problem will get solved.
The ITER experimental fusion reactor is having $12 billion and 30 years invested to try to solve the fusion problem - would that money have been better spent on water splitting?
Well, there’s always bias in energy research, so of course I wish there was more money in my area. I would rather go with water splitting and photovoltaics (PV), because we know how to do this already, we have the technology - people have built photovoltaics that work at over 20 per cent efficiency, and 18 per cent efficient systems for water splitting - but they’re just too costly. So the big difference between ITER and solar is, scientifically, with solar we already know how to do it and we know there’s no show-stopper [that would prevent us from reaching our goal]. What I worry about with ITER is there could be a lot of show-stoppers. So, being conservative, I would say to go with PV and solar.
But we practically spend no money on research in the world, especially on this problem. You should be able to run ITER and do all this other stuff, because the problem is too compelling to ignore it. My guess is it won’t be the environment, it will be geopolitics and energy security that will turn people to this problem, and then the money will start flowing.
What do you see as the main hurdles to water splitting becoming a viable energy solution?
There are two keys - one is you have to make photovoltaics cheaply, so you can mass-manufacture rather than have to make them a panel at a time. The second thing to figure out is the reaction chemistry on how to split water to hydrogen and oxygen. We don’t know how to do that yet, even though plants do it every day. We can do the hydrogen part pretty well, but we still have no idea how to get the oxygen out - and you want to do that because you want a closed thermodynamic cycle. You want to be able to give somebody a gallon of water in the desert, make hydrogen and oxygen, and then have it recombine in a fuel cell to get water back again. It’s going to take a concerted effort, we’re going to need theoreticians, computational scientists, molecule builders - we really need to come together to make this happen. And there’s no question these collaborations are forming; a spirit in the community is forming.
You mentioned that plants have already mastered water splitting - shouldn’t we just let them get on with it, and collect the biofuels?
Well, here’s the key with plants - their theoretical limit of energy conversion is 10 per cent efficiency. Practically, the best stuff people hope to see some day is 2-3 per cent efficiency out of a plant. With solar PV, people walk in the door expecting 10 per cent efficiency - so they’re starting off at the theoretical limit of a plant, and they expect to top out at 20-25 per cent efficiency. So that’s the big difference, and the reason why I chose this problem and I didn’t become a biofuels person. It’s simple maths, you want to go where the ceiling is highest.
Are you optimistic that we’ll solve these problems?
I know science will get there - we already know how to do it, it’s just a question of doing it cheaply. And that’s not easy, it’s going to take massive new discoveries to make it cheap, but we can do it, I’m sure of it.