A new approach to passive power generation takes the shape of a thermoelectric generator (TEG) that can continuously generate electricity using solar heat and a radiative element that releases heat into the air. The self-powered TEG engineered in China operates under nighttime and cloudy conditions and could deliver reliable power supplies for small electronic devices such as outdoor sensors.

TEG devices produce an electric current as a thermoelectric material experiences a temperature gradient, causing electrons to flow from hot portions to cold portions. However, available systems tend to produce unstable temperature differences and do not yield enough electricity to be useful. The new TEG design incorporates an ultra-broadband solar absorber (UBSA) to capture sunlight, which heats one side of the generator. Simultaneously, a planar radiative cooling emitter (RCE) cools down the other side by releasing heat. Both components can be applied to a flexible substrate, which could be useful for powering wearable devices.

The TEG generates power by means of the RCE mounted on top of the UBSA. Source: Haoyuan Cai/Jimei University

On exposure to sunlight, the unshaded parts of UBSA absorb the sun's energy to heat up while the RCE on top begins to cool. The combination of heating and cooling creates a temperature difference that is converted into electricity. While the temperature difference is significantly reduced under dark or cloudy conditions, a sufficient temperature difference remains that can be tapped to generate electricity.

As reported in Optics Express, outdoor experiments confirmed the continuous production of power by the TEG both during the day and at night. A peak voltage output of 166.2 mV was documented during clear daytime conditions, enough to power a small sensor or device. During clear nighttime and cloudy daytime conditions, it generated 14.7 mV and 95 mV, respectively.

Researchers from Jimei University, Zhejiang University, University of Electronic Science and Technology of China and Fujian Provincial Key Laboratory of Oceanic Information Perception and Intelligent Processing contributed to this development.