Turning electrical power to heat is easy. It regularly happens in your toaster, for instance. The reverse, turning heat into electrical power, isn’t so easy.
That’s what makes the gizmo shown in the picture above – called an infrared rectifying antenna, or rectenna – so special. The tiny wafer aluminium, silicon dioxide and silicon is about 3 millimetres on a side and has a microscopic pattern etched into its surface that acts as an antenna to catch heat energy in the form of infrared radiation. The radiation creates oscillations in the silicon dioxide that in turn create an asymmetric movement of electrons – an electric current – between the aluminium and silicon.
Though the device is still quite inefficient, the researchers who developed it – from Sandia National Laboratories in the US – hope to have an improved version available in the next five years that can effectively transform waste heat, from a car engine for example, into useable electricity.
The rectenna is described in a paper in Physical Review Applied.