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New heat-harvesting material made in $40 microwave oven


September 30, 2011

Researchers have created an efficient new thermoelectric nanomaterial, that could be used to harvest waste heat for conversion into electricity (Image: Rensselaer/Ramanath)

Researchers have created an efficient new thermoelectric nanomaterial, that could be used to harvest waste heat for conversion into electricity (Image: Rensselaer/Ramanath)

Virtually all electrical devices and industrial processes create heat as they operate, which is typically wasted. In the past several years, various thermoelectric technologies have been developed to address that situation, by converting such heat into electricity. The ideal material for the purpose would be one that has a high electrical conductivity, but a low thermal conductivity - that way, it could carry plenty of electricity without losing efficiency through overheating. Unfortunately, electrical and thermal conductivity usually seem to go hand in hand. With some help from an ordinary microwave oven, however, researchers from New York's Rensselaer Polytechnic Institute have created a nanomaterial that appears to fit the bill.

The team started with zinc oxide, which is already pretty well-suited to heat harvesting, as it is nontoxic, cheap, can have its electrical conductivity boosted, and has a high melting point. It is also, however, fairly thermally conductive.

In collaboration with the University of Wollongong, Australia, the researchers proceeded to add tiny amounts of aluminum to samples of zinc oxide, then processed the two materials together in a microwave oven. The resulting aluminum-doped zinc oxide nanocomposite retained the original zinc's electrical conductivity, but had a much lower thermal conductivity.

Several grams of the pelletized nanocomposite could be produced in just a few minutes, which is reportedly enough to create a heat-harvesting device several centimeters long. The process is also said to be environmentally-friendly, while also less costly and more scalable than conventional alternatives. It can also be made and then applied to surfaces, unlike other heat-harvesting materials that have to be fabricated directly onto a surface.

"Harvesting waste heat is a very attractive proposition, since we can convert the heat into electricity and use it to power a device - like in a car or a jet - that is creating the heat in the first place" said team leader Professor Ganpati Ramanath. "This would lead to greater efficiency in nearly everything we do and, ultimately, reduce our dependence on fossil fuels."

Scientists at Northwestern University have also recently had a similar success, with a thermoelectric material that they created by adding nanocrystals of rock salt to lead telluride.

The Rensselaer research was recently published in the journal Nano Letters.

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

This sounds exciting and hopefully \'more scalable\' means it can be scaled up to industrial production levels. So how long before I can paint the walls/roof of my house and harvest electricity? Could it be a realistic alternative in hot countries, to photo voltaic systems?


One more \'notch\' in the handle of the litany of devices serially presented , representing new advances in the field of electricity, a notch representing nothing of value but contributing in a small way to the acceptance of \'Anderson\'s Law\', which states that 100 \'inventions\' are announced before a single real market product exists. The dearth of actual data on this latest pseudo-product does not foster a shred of confidence that this is \'the one\' that endures.


Hey not fair - I want to try this! I have both raw materials at home - where is the process?


Perhaps if this is made into a dinky chainmail material and then a bikini it will be as popular as the solar panel bikini?

Eh? Brrrllent, ne pas?

Karsten Evans

I assume the aluminum should be in metallic form, not oxide; so I believe the first challenge would be obtaining the metallic aluminum powder and processing the material before the aluminum oxidizes. It would be nice to know what the proportions are, but that\'s the real trick, right?

William Lanteigne

Most of the Peltiers available in market have poor Heat to Electricity conversion efficieny. Say around 5%-10% max. This does not explains anything about how it is excatly converted and efficieny factror. Also cost of such a module. There are many such \'claims\' but hardly anything is yet commercialized! :-(

Prashant Chandanapurkar
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