Silicon chip breaks "blackbody limit" to produce more electricity from heat than thought possible
Energy conservation is a no-brainer and more important than ever, but it's not just about environmental implications. If we're to successfully create smaller, better, more efficient technology, then the thermal energy that our gadgets waste needs to be put to much better use. This new device, which works at the nanoscale where the theoretical "blackbody limit" falls apart, could be the answer.
The blackbody limit (formulated in 1900 by German physicist Max Planck) is a theory which describes the maximum amount of energy that can be produced from thermal radiation (heat), but when objects get very, very close, the law breaks down and thermal transfer from one object to another increases exponentially.
So, in short, the closer the objects, the better the energy transfer, but the mechanical difficulty of keeping two objects as close as possible without letting them actually touch has been a significant challenge. A challenge a team at the University of Utah has risen to with its Near-Field Radiative Heat Transfer Device.
Associate professor Mathieu Francoeur and his team created a tiny chip (5 x 5 mm), comprising two silicon wafers with a stable gap between them of 100 nanometers and held in a vacuum. The team then heated one wafer while cooling the other, and this in turn created a heat flux which can be used to generate an electric current. The heat flux method of generating electricity isn't new in and of itself, but the method the team developed for maintaining such a microscopically close, uniform hesitance between the silicon wafers is.
"Nobody can emit more radiation than the blackbody limit," says Francoeur. "But when we go to the nanoscale, you can."
The team see a myriad of applications for the heat transfer device. From cooling processors in computers and mobile phones (improving their operation and their functional lifespan) to turning the waste heat into electricity to improve battery life. The chip could also be used to create power for technology where the physical environment has its own heat source, such as implantable medical devices. And of course, the environmental benefits are massive for economic technology such as this.
"You put the heat back into the system as electricity," says Francoeur. "Right now, we're just dumping it into the atmosphere. It's heating up your room, for example, and then you use your AC to cool your room, which wastes more energy."
The paper on the near-field radiative heat transfer device is available via the journal Nature Nanotechnology.
Source: University of Utah