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Cooling mechanism increases solar energy harvesting for self-powered outdoor sensors

An illustration of thermoelectric devices using a wavelength-selective emitter and a broadband emitter. The device using a broadband emitter experiences a voltage drop due to environmental temperature changes, while the device with a selective emitter remains constant thanks to daytime radiative cooling. Credit: Satoshi Ishii Sensors placed in the environment spend long periods of time outdoors through all weather conditions, and they must continuously power themselves in order to collect data. Many, like photovoltaic cells, use the sun to produce electricity, but powering outdoor sensors at night is a challenge.

Thermoelectric devices, which use the temperature difference between the top and bottom of the device to generate power, offer some promise for harnessing naturally occurring energy. But, despite being more efficient than photovoltaics, many thermoelectric devices flip the sign of their voltage, meaning the electrical current changes the direction of its flow, when environmental temperatures change, so the voltage drops to zero at least twice a day.

“The sign of the thermoelectric device depends on the temperature difference between the top and bottom of the device,” author Satoshi Ishii said. “Cooling can be used to create a temperature difference compared to the ambient temperature , and if there is a temperature […]

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