Radiative Cooling for Nighttime Electricity Generation
Radiative cooling is a natural phenomenon where the Earth’s surface emits infrared radiation into space, creating a temperature difference between the Earth and outer space. This temperature difference can be harnessed to generate electricity at night using thermoelectric generators (TEGs).
Principle
The principle behind radiative cooling involves exploiting the temperature difference between the Earth and outer space. On a clear night, a surface facing the sky can emit thermal radiation into space, which is at a very low temperature (about 3K). As a result, the surface cools down below the ambient temperature, creating a temperature gradient that can be used by thermoelectric devices to generate electricity.
Process
- Radiative Emission: A thermal emitter, typically designed to enhance radiative emission within the atmospheric transparency window (8–13 μm), faces the sky. This allows efficient heat loss into space.
- Temperature Gradient: The temperature of the emitter drops below the ambient air temperature due to radiative cooling, creating a temperature gradient.
- Thermoelectric Conversion: Thermoelectric generators are used to convert this temperature difference into electricity. They produce an electric voltage in response to the temperature gradient between the emitter and the surrounding air.
Advancements and Efficiency
- Recent advancements have focused on optimizing the design of thermoelectric systems to maximize power density. Techniques include minimizing parasitic heat transfer and using multiple TEGs to enhance efficiency.
- Power densities generated through radiative cooling have ranged from about 25 mW/m² to over 100 mW/m², with potential for higher outputs under optimal conditions.
Applications
Radiative cooling for electricity generation is especially promising for off-grid applications, such as powering sensors, lights, and communication devices in areas without access to traditional power sources.
Challenges
While radiative cooling offers a unique opportunity for nighttime energy generation, challenges include maintaining efficiency across varying atmospheric conditions (like humidity) and achieving higher power densities comparable to other renewable sources.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-radiative-cooling-work-in-generating-electricity-at-night/
