SBIR Phase I: Developing Ultrahigh-Efficiency Thermal-to-Electric Energy Conversion Technique for Harvesting Geothermal Energy

This Small Business Innovation Research Phase I project will develop a novel technique using nanoporous materials to harvest energy from low-grade heat. Because of their ultra-large surface areas (100-2000 m2/g), nanoporous materials can absorb a large number of ions when immersed in electrolyte solutions. This capacitive effect is thermally dependent. If two nanoporous electrodes are placed at different temperatures, they confine different amounts of ions, generating a net voltage difference. The thermally driven ion motion causes a transient current, which can be reactivated through temperature fluctuation, position shifting, or internal grounding. The two electrodes (high and low temperature poles) are isolated; that is, the direct heat loss between them is minimized. Experimental data has shown encouraging results: the output voltage/power and the energy conversion efficiency are higher than that of conventional thermoelectric materials by orders of magnitude. The goal of this project is to develop a commercial-ready high-performance thermal energy harvesting system that is cost effective and highly efficient. Studies will characterize performance at low temperature differences of 40 to 200 degrees centigrade, including charging/discharging reliability, and material and system costs will be gauged. The broader impact/commercial potential of this project will be a new scalable method to convert waste heat to electrical energy. The system will be optimized for operation at low temperature differences (less than 200 deg. C), which will allow operation, for example, in the thermal regime of common turbine generators. The development of a high-efficiency energy harvester will enable the push to harvest waste energy from this and other low-temperature waste heat sources. This project will also explore converting automotive, solar thermal, and other waste heat that involves temperature fluctuations. This will in turn have a significant social impact by reducing greenhouse gas emission and the use of fossil fuels.