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.
A non-conventional energy conversion technique was explored under a NSF Phase 1 SBIR grant from January 2011 to June 2011. This novel concept had great potential to harvest low-grade heat (LGH) energy, which accounts for the majority of today’s wasted heat and falls into a blank area of today’s technology. Waste heat is defined as temperatures below the thermal to electric economic envelope. This is typically under 200 Celsius. Sources of waste heat include, but are not limited to, geothermal, solar thermal, and exhaust heat from power plants. This can be a benefit to alternative/clean tech energy. Prior to the start of the grant, an evaluation of the technology was made. This determined what the grants research objectives were and current status of the technology. During grant project, which lasted over the next six months, a number of experiments were carried out. They were performed under lab conditions. The energy conversion density and working temperature ranges were tested. As a result, they have been greatly increased, closer to deployment levels. The recharging methods were also systematically investigated. After completion of the grant, the milestones and technical challenges were identified. This has given a better understanding of the technology and its broader impact.
