Electricity has been generated in largely the same way since the 1800s. Heat is used to boil water to make steam, the steam turns a turbine, and the turbine turns an electrical generator. Each of those stages introduces inefficiencies of lost heat and energy as well as moving parts that break and need to be replaced. Thermophotovoltaic cells (TPVs) are a new type of device that can reduce or eliminate some of these inefficiencies. They are similar to the more familiar solar cells that are widely used to generate electricity. Whereas solar cells primarily absorb visible light, TPV cells absorb infrared light (radiated heat). They can potentially be used to generate electrical power from any heat source, without moving parts or any of the stages between generating heat and electricity. This project will develop each of the primary components of the TPV generator system to bring this technology to fruition. Once realized, these TPV generators can be used to improve the efficiency of existing energy conversion technologies (natural gas, coal, nuclear, and solar thermal) and allow for the harvesting of waste heat from heat source such as furnaces and engines. It may even be possible to power implanted medical devices like pacemakers with one's own body heat.
Thermophotovoltaic (TPV) systems are similar to solar (photovoltaic, PV) cells in that they function through the photovoltaic effect. Incident light promotes charge carriers across the bandgap, which are driven apart by the built in voltage of the photodiode. These carriers become electrical current. However, whereas PV cells absorb primarily visible light, TPV cells function primarily in the infrared and include additional "host machinery," consisting of three primary components: 1) a frequency-selective emitter; 2) a filter; and 3) a TPV photodiode. These elements are combined to create a highly efficient energy conversion process. In this work, we are addressing the significant challenges in each of the three components 1) frequency-selective emitters do not function well at higher temperatures, so we are employing new materials that will solve that problem; 2) filters that are separate are less efficient, so we are incorporating them into the photodiode; and 3) TPV photodiodes do not work well at longer wavelengths (i.e. smaller bandgaps), so we are using new materials and device structures to extend the operational wavelength. In general, if successful, these TPV devices will make possible a new array of technological applications. They will increase the efficiency and reduce the waste heat from a multitude of devices; including, civilian and naval nuclear power plants, computer chips, car engines, and many industrial processes. It may even be possible to power implanted medical devices (e.g. pacemakers, and neural implants) with one's own body heat.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
