This uses the thermoelectric effect and radiative cooling at night to power an LED. However, if cooling radiation is real then it should be possible to concentrate it from the sky onto the top of the device and produce a greater temperature difference and therefore more electricity.
Harry Generating Light from Darkness MARCH 19, 2020 https://www.energy.gov/science/bes/articles/generating-light-darkness paper https://www.sciencedirect.com/science/article/pii/S254243511930412X
