Thermally-driven Electrokinetic Power Generation System Utilizing Microporous NiO Wicks and Nanoporous AAO Membranes for Low-Grade Heat Harvesting

Low-grade heat (T<100 degrees C) exists ubiquitously in the environment, but it is difficult to harvest and utilize due to existing technology's limitations. It would be significant to harvest this kind of energy through effective acquisition techniques. Here, we propose a micro/nano porous membranes low-grade heat harvesting system based on the thermoelectric effect, which uses the temperature gradient to induce the separation and transmission of electrolyte solution ions in the porous membrane to convert low-grade thermal energy into electrical energy. Two power generation materials of microporous nickel oxide (NiO) wicks and nanoporous anodic aluminum oxide (AAO) membranes were investigated experimentally. In the porous NiO wick experiment, it is observed that the wick significantly improves the thermoelectric conversion performance. In particular, when the temperature difference is 50 degrees C, the open circuit voltage of the system reaches 215 mV, which is about 300 % higher than the case without the porous NiO wick. In addition, in the AAO porous membranes experiment, we found that at the low concentration, by collecting ambient heat with a temperature difference of 5 degrees C, the system obtained the output power of about 6 nW, which improved the 2 similar to 3 orders of magnitude compared with the previous research reports. This work offers a promising method for developing high-performance and low-cost low-grade heat harvesting systems.