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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

CAVITY ABSORBER-EMITTERS FOR HIGH-TEMPERATURE SOLAR THERMOPHOTOVOLTAICS

Get access (open in a dialog) DOI: 10.1615/IHTC16.nee.023307
pages 7485-7493

要約

Solar thermophotovoltaic (STPV) devices enhance photovoltaic power conversion efficiencies through the introduction of an intermediate spectral converter, reshaping the broadband solar spectrum into a narrow band tuned for the spectral response of a PV cell. Concentrated sunlight heats this converter, which thermally emits power towards a low-bandgap cell. By introducing the ability to precisely tune the emission spectrum, photovoltaic conversion efficiency can be much higher that it would be under direct solar illumination. Unfortunately, some of the absorbed solar energy is lost through re-emission from the absorbing surface in the form of infrared radiation. In this work, we investigate a purely geometric solution to mitigate these re-emission losses by increasing the ratio of emitter area to absorber area, defined as the area ratio. If the area ratio is large, a larger fraction of the total emitted power leaves through the emitter surface. By using a cavity in place of the planar absorber-emitter demonstrated in previous works, we can achieve higher area ratios and thereby significant improvement in the predicted system efficiency. To evaluate this approach, we developed a model quantifying the performance of cavity absorber-emitters with differing area ratios. We experimentally validated our model using cavities with area ratios of 24 and 106. By integrating our cavity-type absorber-emitter with spectrally selective surfaces and filters already realized in the literature, the maximum full system efficiency demonstrated in previous works could be increased from 6.8% to 9%. This cavity-type approach could lead to a significant increase in the energy conversion efficiency of solar absorbers for STPVs and other solar thermal technologies.