Enhancing thermoelectric output power via radiative cooling with nanoporous alumina

In this work, we demonstrate an enhanced thermoelectric output power using nanoporous alumina grown on aluminum (Al) surfaces. The improved power is due to enhanced thermal emissivity and passive radiative cooling associated with nanoporous alumina. We show that a careful balance between conduction, convection, and radiation heat transfer processes leads to optimal passive cooling for 30-40 mu m thick alumina layers, while the nanopore size has a negligible effect. By growing a conformal alumina layer on an Al heatsink surface, the output power of a commercial thermoelectric generator (TEG) showed about 55%-70% increase for temperature range of 150 - 250 degrees C compared to using an untreated Al heatsink. With minimal footprint and no additional energy input, our passive cooling optimization method is a simple and facile way to enhance the TEG output power and can be extended to other applications that utilize Al heatsinks, e.g., computers, cell-phones, and refrigerators.