A thermoelectric device that can simultaneously harvest radiative cooling and solar heating is being developed. The key component is a vertically placed transparent thermoelectric module. The device is capable of harvesting radiative cooling and solar heat simultaneously during the day and radiative cooling at night. Our device can be an efficient method of judiciously harvesting solar heating and radiative cooling simultaneously, which can be used as stand-alone power supplies for off-gird sensor modules.

As thermal radiation is heat transfer by electromagnetic waves, it is possible to control thermal radiation with nanostructures. One of the examples we have demonstrated in the past is wavelength-selective thermal radiation, where thermal radiation spectra are narrowed down to submicron bandwidth. Currently, we aim to enhance radiative heat transfer by taking advantage of transparent multilayers with an effective high refractive index in the mid-infrared. Calculations based on flectional electromagnetics show that thermal radiation can be comparable to thermal conduction when the temperature difference between the hot and cold sides is small. We also try to enhance thermal extraction from high-refractive index materials to ambient by patterning micron-scale pyramids on the surface.