Courtesy of the American Chemical Society and World Science staff
A phenomenon noted by an ancient Greek philosopher has become the basis for a device designed to generate electricity from the immense amounts of energy wasted as heat every year.
The ‘pyroelectric nanogenerator’ is the topic of a report in the research journal Nano Letters, published by the American Chemical Society.
In the paper, Zhong Lin Wang and colleagues at the Georgia Institute of Technology explain that more than half the energy generated in the US each year is wasted. Much of it drifts away as heat released by everything from computers to cars to electric transmission lines.
Theophrastus saw it first
However, heat can be converted back to electricity using something called the pyroelectric effect. This was first described by the Greek philosopher Theophrastus in 314BC, when he noticed the gemstone tourmaline produced static electricity and attracted bits of straw when heated.
Heating and cooling rearrange the molecular structure of certain materials, including tourmaline, and create an imbalance of electrons, or electrically charged subatomic particles. As nature attempts to correct the imbalance, electrons start to flow, making an electric current.
Wang’s group wanted to apply the principle to make a generator that could take advantage of heat changes in the modern world. The researchers made molecular-scale wires, or nanowires, out of zinc oxide, a compound added to paints, plastics, electronics and even food. Using an array of short lengths of nanowire standing on end, they found a device that produces electricity when heated or cooled.
The scientists suggest the nanogenerators could even produce power as temperatures fluctuate from day to night. It ‘can be the basis for self-powered nanotechnology that harvests thermal [heat] energy from the time-dependent temperature fluctuation in our environment for applications such as wireless sensors, temperature imaging, medical diagnostics and personal microelectronics,’ they wrote.
Source: World Science, http://www.world-science.net