Wednesday, October 22, 2014

The Incredible True Story of a “Solar Cell” That Works in the Dark

Despite the lurid title, this is a true story, and I will do my best to tell it here today, for the first time,
starting from everyday life but building up to the new stuff one needs to know to actually make it work and really understand it. I know all the reasons why it is supposed to be impossible, why it is impossible despite that, and why it is a huge opportunity – and I will get to that.

I can explain the key new parts in just one paragraph – to a world-class quantum optics person (like the one I just spoke to while typing this), but I will push that paragraph to the end of this blog entry, because most people don’t have that background.

Where to start?


First, with the benefits that WOULD arise if people built such a thing.

Years ago, when we at NSF were setting up a new program in quantum theory for new electronic and optical devices, we first organized a workshop bringing together respected world leaders in that kind of research. The details of that workshop are summarized at:

One of the well-known speakers, Dr. Bob Trew of North Carolina State University (NCSU), reported on his collaboration with Ki Wook Kim of the same place. He was the one who explained: “The kind of chip we are working on is just like a solar cell, a new source of electricity – except that it works in the dark. We know that heat generates infrared radiation inside of any object, and we think we can convert infrared light to electricity.” That team submitted a proposal to NSF, which reviewed well, and was funded. (If you go to, and click on “awards”, you can search on awards for Trew and Ki Wook Kim, and see the details.)

Trew and Kim estimated that a chip just one centimeter by one centimeter could generate something like 2 watts of electricity, in theory. So try to picture a plug-in car with ten slabs of this stuff attached to the inside of the metal car body, each ten centimeters by ten centimeters, with little PC-style fans to keep them from freezing. Imagine having 2 kilowatts to recharge your battery, day and night – a plug-in car which doesn’t need to be plugged in.

Or, think of it in economic terms. The most reliable sources of data (OECD/IEA) say that the world consumes more than 20,000 terawatt hours of electricity per year. At a “typical’ price of 10 cents per kilowatt hour (kwh), that multiplies out to more than $2 trillion PER YEAR. That’s a whole lot of money. It’s also a whole lot of greenhouse gasses, which some of us regard as a threat to all human life on earth. Most folks say that ordinary solar energy would raise the total cost of electricity to the end user to more like 50 cents per  kwh, for the lucky countries which HAVE enough solar energy to meet all their needs; that’s because solar energy in most places is not so reliable, because clouds get in the way, and it’s not 24 hours in any case. But with a steady 24-hour source… well, it would be a really big deal. Lots of people have sacrificed their lives for gains a whole lot smaller than this. (That’s part of why I am crazy enough to write this up TODAY, just for my obscure personal blog, even though I know all the many stages people are supposed to go through before talking about stuff like this in a serious way.)

Sadly, there are lots of cultural and political barriers here, which take time. If we don’t solve some of our energy and environment problems within the next 20 years, we might not be here anyway.  I might die of old age by the time the present crises are taken care of, and the groundwork for this well enough prepared. Technically, there are important steps we could take TODAY to move on this new energy source, but it seems I am called elsewhere. So I leave this for the next generation, just in case I DO die of old age before I can do more with it, just in case someone notices.

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