Lightweight, Passive Radiative Cooling to Enhance Concentrating Photovoltaics

Context & ScaleConcentrating photovoltaics (CPV) aim to focus sunlight on solar cells to improve efficiency and reduce material costs. However, concentration also increases heating of the solar cells, potentially offsetting efficiency improvements and reducing system lifetimes. Active cooling, such as forced air and liquid cooling, is usually required, but increases the cost while reducing net power production. Radiative cooling, on the other hand, uses thermal radiation to dissipate heat, which is cheap, lightweight, and requires no extra power. This is especially beneficial for enclosed CPV systems using solar trackers. Our experiment shows that by coupling radiative coolers on a flat heat sink, the solar cell operating temperature in a passively cooled CPV can be reduced by 36°C under a heat load of 6.1 W. As a result, a 27% relative increase of open-circuit voltage is observed for the GaSb cell. A lifetime extension of 4 to 15 times for typical CPV cells is also projected.Highlights•Radiative cooling for CPV is a cheap, lightweight add-on requiring no power•A 36°C temperature drop is achieved, leading to a 31% increase of VOC•A 4 to 15 times extension of lifetimes for various CPV cells is predicted•Different cooling structures are investigated at a wide range of conditionsSummaryRadiative cooling can reject significantly more waste heat than convection and conduction at high temperatures by sending it directly into space. As a passive and compact cooling mechanism, radiative cooling is lightweight and does not consume energy. These qualities are promising for thermal management in outdoor systems generating low grade heat, such as concentrating photovoltaics (CPV) and thermophotovoltaics (TPV). In this work, we first simulate radiative cooling for a wide range of working conditions, including heat loads from 6 to 100 W with different CPV cooling designs. We then demonstrate a CPV system integrated with radiative coolers, achieving a 5°C to 36°C temperature drop and an 8% to 27% relative increase of open-circuit voltage for a GaSb solar cell, under a heat load of above 6 W with different cooling designs. We show that the temperature drops from radiative cooling may significantly improve CPV system lifetimes.Graphical abstract