Keeping a cool head helps power sensors day and night

A new strategy for powering sensors using environmental energy ensures that currents flow in the same direction day and night.

Sensors are increasingly being used to monitor all kinds of things, from outdoor temperature to traffic volume. Self-powered sensors that collect energy from the environment are desirable as they can be installed anywhere and don’t need batteries.

Thermoelectric materials generate electricity whenever their top and bottom surfaces are at different temperatures, making them attractive for powering sensors. But since the temperature difference flips between day and night, so does the sign of the voltage they generate.

Now, a scientist at the University of Tsukuba in Japan and two collaborators have overcome this limitation by putting an aluminium-coated glass layer on the top surface of the thermoelectric material. This layer cools the thermoelectric material through radiating radiation in a certain wavelength range. The top surface is thus always cooler than the bottom surface, ensuring that the voltage always has the same sign.