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Melanie Gonick
MIT doctoral student Daniel Kraemer, right, and Professor Gang Chen display a prototype of a flat-panel solar-thermoelectric generating device.
With the aid of nanotech materials, scientists have engineered a new way to convert the sun's heat into electricity that is roughly eight times more efficient than previously reported solar thermoelectric devices.
What's more, the device could be added to existing solar water heaters, giving people a jolt of electricity to power their gadgets along with warm bath water, noted Gang Chen, an engineer at the Massachusetts Institute of Technology.
"We just changed the existing system a little bit," he told me today. "Then we generate electricity and supply hot water."
Chen and colleagues at MIT and Boston College described the technology in a paper published online May 1 in Nature Materials.
Thermoelectric devices
Solar thermoelectric devices typically involve vast arrays of movable mirrors that track the sun and focus its rays on a small area. In solar thermal power plants, another type of solar energy, the sunlight is focused on tubes that heat fluid inside that is then used to boil water in a conventional steam-turbine generator.
The new system takes advantage of a thermoelectric principle "where when there is a temperature difference across a solid it actually generates a voltage," Chen explained.
He and his colleagues placed a flat heat absorber — a piece of copper coated with a nanostructured material — into in a vacuum so that the "absorbed radiation doesn't have any place to go," Chen said. This forces the absorbed heat to flow along two legs with thermoelectric properties.
The combo generates and harnesses a temperature difference of about 200 degrees Celsius between the interior of the device and the ambient air. That temperature difference is what drives the electricity along the legs, Chen explained.
Solar hot water integration
The device is well suited for integration with solar hot water systems, allowing a quicker payback for the cost of installation, according to the research team.
Solar hot water systems today already consist of a black absorber to heat up water flowing through a copper pipe.
"Now, what we do instead of directly attaching [the absorber] to a copper pipe, we put on those two legs to take out part of the energy as electricity," Chen said. "The rest goes to hot water, so you now have two-in-one."
In such a setup, the ambient side of the system is actually the hot water, which at about 60 degrees C is warm enough for a shower. "We can use the additional 140 degrees to get the electricity out," Chen noted.
Current photovoltaic efficiency is greater than that achieved with this system, so it is not going to replace rooftop solar panels, Chen noted. But adding to existing solar hot water systems make sense.
"The additional incremental cost of electricity is really cheap," he said. "In fact, according to our modeling it is cheaper than photovoltaics."
More stories on solar energy technologies:
- GE to build nation's largest solar power plant
- How serious is space solar power
- Chicago getting a tower of power – solar power
- Solar power coming to a store near you
- Origami boosts solar panel productivity
John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).
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Good Idea!! just let me know when its on the market!
That's exactly what I was thinking. I love hearing about advancements in science, but I'd love it even more if they EVER made it to the consumer market! At least once every three to six months I hear a story about how solar cell efficiency has been improved 45-80%, but I never hear about those improvements making it to the solar cells being sold.
The length of time to the break-even point, (cost savings to initial cost ratio), coupled with the life span of this device is key. If the ratio can be made favorable, (less than half the expected life of the device would be good), and the environmental cost of making it and disposal/recycling of the worn out units aren't unacceptable, this will be a success.
That's hot!
Excellent news. I am always amazed at people who can look at something like a hot water heater and turn it into something like in this article. And I always say, WHY DIDN'T I THINK OF THAT? DOH!
Actually, the idea has been around and in use for a very long time already.
I'm hoping that this technology, or any technology that will allow us to completely eradicate our need to use fossil fuels or coal or whatever to heat our homes, our water, etc., will be available inexpensively as soon as possible.
It will never be a viable alternative to fossil fuels. There is nothing today that can fill the versatility required. It may be a minor option of specific regional use, but basically a toy of limited application.
I would disagree with you on this.
Unfortunately, we are ten years away from having solar power available to us... I know that this is a fact because I have been told so for the past 30 years, and it is even more true today than it was then. In another ten years, I am sure we will be only ten years away from having solar power. At that point, it's just a matter of a decade or more that we will have to wait. The problem is that solar power takes money away from oil billionaires, and they have the money to make sure solar never ever interferes with their profits.
That is exactly opposite of reality. If it was a viable money maker the "oil billionaire's" would be the first to adopt a new method in order to make large amounts of money as early adopters. It is just a toy with limited application at this time and probably never will be anything else. The concept is from 1816 which was long before the mythical "big oil" conspiracy, if it was a better option dont you think it would have been the method of choice?
This is NOT new technology just an application of an external combustion engine (using the sun as the heat source) from 1816, its called a Stirling engine. The only thing new is the advance in technology computer systems that allow tracking the heat source. In general application its not really different from internal combustion, what makes this viable is the heat source but its cumbersome because of the number and complication of the mirrors. There is a pilot plant built for electrical production which takes banks of computers and acres of mirrors to work .... think of the environmental impact those mirrors have as well as the limited number of regions the system is viable option in, another toy when you consider what is required to replace conventional methods.
Gee
What will we do when there is no oil being pumped?
What would we do for plastics,roads,fertilizer,insecticides,toothpaste,and a myriad of other things that we depend on for our daily lives???
Be careful what you wish for,it may come true. Old Confuses saying.
synthesize? I am sure man will find new ways to make things we have come to know. Who says oil cant still be used, we can cut oil as our major energy source and change to solar and still use oil in other applications.
Besides its not like oil will just no longer be used, it will most likely be phased out and replaced.
It doesn't matter what technology you have as long as you have greed and corruption, someone will be socking it to the public. Oil is not the problem it never was, our problem is that mankind as a whole is a selfish, greedy, vicious, narrow minded creature.
@Mark - I agree, but then, what do you expect from millions of years of evolution? Survival/reproduction of the fittest. It works in the animal world, the human world follows most of the same rules.
Well if evolution is the rule then extinction is most likely our fate because we certainly are not evolving.
I like the idea of combo tech. If you combine the right ideas more areas of productivity will be abailable. For instance, take wind power in areas where solar is not as available, and use small home units to charge the batteries for backup power. It was working many years ago on mountain top radio repeaters. The tech has much improved since then. Come on you older tech people, you know what I mean. Sound off, we need all the good old ideas that still work.