“Dark” Photovoltaic Cells for Space Power Generation

Advanced Cooling Technologies, Inc. (ACT) proposes to develop a novel ldquo;darkrdquo; photovoltaic cell technology that can generate electricity when there is no sunlight.nbsp; The proposed ldquo;darkrdquo; PV technology exploits the thermo-radiative (TR) cell, which is also made of semiconductor p-n junctions and can be viewed as a reversed PV cell, as a new way to efficiently convert heat to electricity when radiatively coupled to a low temperature heat sink. In a previous NASA sponsored program, ACT has successfully demonstrated the proof-of-concept by using commercial narrow-gap semiconductor p-n junctions as thermo-radiative cells to generate electrical power. These results strongly suggested that thermo-radiative cells can be used as a ldquo;darkrdquo; photovoltaic technology to generate electrical power when the cells face the extremely cold deep space. For example, we could use it to generate electricity during lunar night by utilizing the waste heat from the radiator. We could also use it as an alternative high temperature photovoltaic technology for near-Sun missions that the backside of the cells faces the sun to absorb the solar-thermal energy and the frontside of the cells faces to the dark space. Our modeling results showed that thermo-radiative cells can have a power density up to 1200 W/m^2 when the cell temperature is about 700 K, with an efficiency around 30-40%. To increase the maturity of this technology, ACT, in collaboration with University of Michigan, plans to develop a customized thermo-radiative cell with an area orders of magnitude larger than commercial narrow-gap semiconductor p-n junctions. ACT has a strong Ramp;D team in place to perform the proposed work and a long history of supplying advanced thermal systems for flight applications. The team at UM has a long history working with narrow-gap semiconductor materials, including growth, fabrication and characterization.