Nanoscale pillars could help convert heat to electricity

February 22, 2014 by  
Filed under Solar Energy Tips

The Physical Review Letters journal recently published a study that may send nanotechnology in a new direction: aiding with a potential source of energy. In their work, Professor Mahmoud Hussein and doctoral student Bruce Davis of the University of Colorado at Boulder, demonstrate an entirely different way to slow heat transfer without affecting the motion of electrons, using an age-old principle of physics known as the thermoelectric effect.

First described in the 19th century, the thermoelectric effect refers to the ability to generate electrical current from a temperature difference between one side of a material and the other. Applying an electric current to thermoelectric material can cause one end of the material to heat up while the other stays cool. Unfortunately, the reverse is also true, and overheating electrical devices run the risk of weakening the current they rely on in order to run.

The researchers built nanoscale-sized pillars, which were then placed over a sheet of silicon, material known for its thermoelectric properties and also regularly used in nanotechnology, to create what the authors referred to as “nanophononic metamaterial.” Using a sequence of very minimal vibrations, heat was transported through the material. Davis and Hussein used a computer model to show that the vibrations of the pillars would interact with the vibrations of the phonons, slowing down the flow of heat. The pillar vibrations are not expected to affect the conductivity of the electrical current, while the materials reduce the output of heat.

Nearly all electronic devices give off excessive heat when they run, be it electric stoves, laptops or cell phones. Now, however, researchers have a way to convert that heat into energy that can be used. In fact, the team estimates that the pillars they built could reduce heat flow through a material by half, but because they used their most conservative calculations, the reduction could actually be much higher, according to Hussein, who is a material physicist.

In addition to reducing the safety risk that is associated with using an overheating laptop, this new technology could improve the device’s efficiency, harvesting more power from solar panels.

Already having faced a successful test run, the next step is for Hussein and his colleagues in the physics department to reproduce the pillars that they used in the initial tests, which may eventually result in an improved design, as Hussein continues to study the physics involved, hoping that the end result will mean the best possible product on the market.

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