Thermoelectric Power Production Efficiency Can Surpass Photovoltaics Under Concentrated Sunlight Due to High-Temperature Performance Degradation

Document Type : Original papers

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1 Mechanical and Aerospace Engineering Department, University of Florida, Gainesville, FL, USA

2 Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL, USA

Abstract

As of 2019, almost 97% of utility-scale solar power capacity is photovoltaic-based. Photovoltaic cells become less efficient at higher temperatures, requiring cooling water for these plants to maintain efficiency. However solar plants are often located in deserts where water is scarce, thus increasing the price of concentrated solar power. An unutilized but attractive alternative is thermoelectric generators under concentrated sunlight with passive geothermal cooling. This paper calculates the crossover temperature at which thermoelectric generator efficiency exceeds photovoltaic cell efficiency due to rising thermoelectric efficiency as operating temperature increases. The crossover temperature was determined to be 495K by theoretical modeling. A comparison of empirical literature for thermoelectric generators and experimental results for photovoltaic cells was conducted. To experimentally represent thermoelectric generators, metal collector targets were placed under two different Fresnel lenses with lens-to-collector target ratios of 28.8:1.0 and 275.0:1.0. Thermoelectric generators should always be considered as an alternative to a photovoltaics in concentrated solar power plants without coolant when the lens-to-target area ratio exceeds 350. For thermoelectric generators, heat flux absorption and corresponding elevated power generation are hindered by sunlight reflection. To improve heat flux absorption, the experimental setup was modified to include black acrylic or refractory painted collector targets. These treatments decreased reflectivity from 93 ± 2% for polished brass to 79 ± 2% and 92 ± 1% for 28.8:1.0 and 275.0:1.0 area ratio, respectively. With dramatic surface reflectivity reduction, thermoelectric generators will outperform photovoltaic cells as an alternative solar concentrating power plant when cogeneration is unneeded.

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