Published recently in Nature Communications, the discovery of a new artificial material could be the key to generating clean electricity at all hours of the day. A new metamaterial discovered by physicists at the Australian National University/ARC Center of Excellence CUDOS and the University of California Berkeley actually gathers energy when exposed to heat.
This, being the most important aspect in creating Thermophotovoltaic cells, is a huge discovery. Rather than needing direct sunlight (photovoltaic), cells created with this nanomaterial can potentially produce electricity from radiant heat in an extremely efficient manor.
“Physicists have discovered radical new properties in a nanomaterial, opening new possibilities for highly efficient thermophotovoltaic cells that could one day harvest heat in the dark and turn it into electricity” – Australian National University
The new metamaterial is comprised of structures of nanoscopic gold and magnesium fluoride which radiate heat in specific directions. With the ability to tweak it’s geometry, it’s possible for radiation within a specific spectral range to be given off.
In contrast, standard materials emit their heat in all directions as a broad range of infrared wavelengths. This ability to change the geometry makes the new metamaterial perfect as an emitter to be coupled with a thermophotovoltaic cell.
“Our metamaterial overcomes several obstacles and could help to unlock the potential of thermophotovoltaic cells” Sergey Kruk, ANU
Dr. Kruk of ANU actually predicted that the new material would act in this way if it existed, and so he set out to create it. Needing to construct a nanomaterial, he sought out the best at creating such things, UC Berkeley. Dr. Kruk and his ANU team then worked with the scientists from Berkeley to correctly manufacture the new material.
“To fabricate this material the Berkeley team were operating at the cutting edge of technological possibilities. The size of an individual building block of the metamaterial is so small that we could fit more than 12,000 of them on the cross-section of a human hair.” – Dr. Kruk, ANU
The reason that the metamaterial has such remarkable behavior is a unique physical property known as magnetic hyperbolic dispersion.
Dispersion is the interaction of light with certain materials. For materials such as glass and crystals, the dispersion surfaces have simple forms of spherical or ellipsoidal.
The new metamaterial’s dispersion is drastically different though, and is hyperbolic in form. This is due to the fact that the new material has an unusually strong interaction with the magnetic aspect of light.
The efficiency of thermophotovoltaic cells based on the metamaterial can be further improved if the emitter and the receiver have just a nanoscopic gap between them. In this configuration, radiative heat transfer between them can be more than ten times more efficient than between conventional materials. – ANU
Early research has shown that thermophotovoltaic cells are more efficient than solar cells. Collecting energy from any heat source, clean energy can be produced from natural heat sources, and energy being wasted by non clean energy can be harvested and utilized. For example a car engine could be surrounded by these cells which collects the residual heat.