Science, Tech & Environment

Cheap energy from the sun

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GELLERMAN: In one hour enough sunlight falls on the earth to power the world for a year. There are just two problems with solar energy: it's still expensive- and night. But now researchers at the Massachusetts Institute of Technology have figured out a way to store solar energy when the sun don't shine. To accomplish the technological trick, the scientists sort of turned over a new leaf: their innovative process imitates what nature does: photosynthesis. The breakthrough appears in the latest edition of Science. MIT's Dan Nocera is lead author. Professor Nocera, welcome to Living on Earth. NOCERA: Thanks, it's great to be here. GELLERMAN: So tell me about your discovery. This is exciting stuff. NOCERA: Yeah, it is exciting. The neat thing about this discovery is we do sort of what nature does. We store sunlight in chemical bonds of hydrogen and oxygen so we can split water to hydrogen and oxygen. And we do it with a catalyst that's really cheap and we do it under conditions that are really cheap, so that's what makes this discovery interesting and important. GELLERMAN: So how do you do artificial photosynthesis? NOCERA: In place of the leaf we put a photovoltaic, so the photovoltaic catches the light and it makes a wireless current and then it can feed that current to our compound. Our compound takes water to oxygen, but the main part is splitting that water and that's what we can do now- and we can do it in a glass of water. GELLERMAN: You know you got me searching back in memory for my high school chemistry. NOCERA: Yeah, that's right. Go ahead, tell me about it. You remembered seeing a teacher probably use electrodes and put 'em in water and make hydrogen and oxygen using electricity from the wall. GELLERMAN: Exactly. NOCERA: They were using the platinum to make hydrogen- that was the thing that was dipping in the water. And on one side you saw the hydrogen bubbles coming out but the thing they didn't tell you is on the other side, where you were making the oxygen at another platinum electrode, that doesn't work so well. So what the teacher was doing, was she or he was goosing the cell, and they were just turning the electricity up and that's how they got the O2- that's called overpotential. They had to use a lot of extra energy to get the O2 out and that's what you don't want to do if you're building an energy economy, you don't want to waste any of that kind of energy. And this new catalyst doesn't waste that much energy. GELLERMAN: Well you still gotta put energy into the system. NOCERA: Sure do, nothing comes for free. And so what we're really doing is if we're getting that hydrogen and oxygen, where's the current coming from? Well in this paper we just published we did it out of the wall- and remember the electricity from the wall comes from a coal fire power plant- but we were doing that just because we're scientists and we were working on the catalyst. What you want to do is get rid of the wall current. The catalyst doesn't care where the current comes from so the next thing is put the photovoltaic there, and that photovoltaic is getting powered by the sun. GELLERMAN: So what you've come up with really is the catalyst, that's they key here. NOCERA: That's right, it's just the catalyst and the neat thing about this catalyst is that it's a glass of water. GELLERMAN: It's a big deal, isn't it? NOCERA: It's a big deal in that it's cheap. We still have a way to go for technology but I'm kind of hopeful. You know there's a lot of companies who have contacted me, big ones, who say, 'Look, we know how to deal with hydrogen and oxygen and we know how to do small power systems but the way we do our hydrogen is we do what's called reforming.' They have big plants and they get their hydrogen from fossil fuels and make CO2 and then they get their oxygen by cryogenically freezing it, by making the air cold and taking it out. That's really expensive and you need big plants. So that little village hut in India, you can't set up those plants. But now if you can make hydrogen and oxygen out of a glass of water, you can start to envision a widely distributed energy system and for me, I want to start in the third world that's where I'm most interested in and then we can start moving it to other places. GELLERMAN: What do they say about imitation- it's the sincerest form of flattery? NOCERA: Um, sure is. GELLERMAN: Well, here you are, imitating nature. NOCERA: And I love nature. At the end, plants are super-efficient at using and converting energy. But guess what they don't do? Store it. And you know that. Did you ever see a fat tree? I haven't. And so they're using most of that energy to live and it only stores a little bit of energy. This thing, I can take all that energy and use it for storage. So I really, I couldn't be more happy than imitating nature because she's my hero. GELLERMAN: Professor Nocera, I heard that you were a big Dead-Head. NOCERA: I am. GELLERMAN: Grateful Dead fan, huh. NOCERA: Yup, since I was a little kid, fourteen years old. GELLERMAN: Well is there a song that comes out of that catalog that might suit our topic here? NOCERA: You know, there's a lot of them, but I think about "Touch of Grey" and it was Jerry Garcia and he was basically saying, 'it's gonna be okay as I get older.' And that's what I'm hoping, that it's going to be okay as I have more touches of grey in my hair too. And I wish Jerry were here. I know he'd be happy. [LAUGHTER] GELLERMAN: Well thank you very much Professor Nocera, it's been a real pleasure. NOCERA: Thanks so much, too. We're going to keep working hard for you guys. GELLERMAN: Dan Nocera is the Henry Dreyfus Professor of Energy and Professor of Chemistry at MIT. His co-author is Matt Kanan. His article is published in the Journal of Science.

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