1000x shadow-free mirror-based Köhler concentrator

Maikel Hernandez; Pablo Benítez; João Mendes-Lopes; Aleksandra Cvetkovic; Yupin Sun; Juan Carlos Miñano; Julio Chaves; Rubén Mohedano

doi:10.1117/12.931657

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10 October 2012 1000x shadow-free mirror-based Köhler concentrator

Maikel Hernandez, Pablo Benítez, João Mendes-Lopes, Aleksandra Cvetkovic, Yupin Sun, Juan Carlos Miñano, Julio Chaves, Rubén Mohedano

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Proceedings Volume 8468, High and Low Concentrator Systems for Solar Electric Applications VII; 84680C (2012) https://doi.org/10.1117/12.931657
Event: SPIE Solar Energy + Technology, 2012, San Diego, California, United States

Abstract

A new design for a photovoltaic concentrator, the most recent advance based on the Kohler concept, is presented. The system is mirror-based, and with geometry that guaranties a maximum sunlight collection area (without shadows, like those caused by secondary stages or receivers and heat-sinks in other mirror-based systems). Designed for a concentration of 1000x, this off axis system combines both good acceptance angle and good irradiance uniformity on the solar cell. The advanced performance features (concentration-acceptance products –CAP- about 0.73 and affordable peak and average irradiances) are achieved through the combination of four reflective folds combined with four refractive surfaces, all of them free-form, performing Köhler integration ². In Köhler devices, the irradiance uniformity is not achieved through additional optical stages (TIR prisms), thus no complex/expensive elements to manufacture are required. The rim angle and geometry are such that the secondary stage and receivers are hidden below the primary mirrors, so maximum collection is assured. The entire system was designed to allow loose assembly/alignment tolerances (through high acceptance angle) and to be manufactured using already well-developed methods for mass production, with high potential for low cost. The optical surfaces for Köhler integration, although with a quite different optical behavior, have approximately the same dimensions and can be manufactured with the same techniques as the more traditional secondary optical elements used for concentration (typically plastic injection molding or glass molding). This paper will show the main design features, along with realistic performance simulations considering all spectral characteristics of the elements involved.

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Maikel Hernandez, Pablo Benítez, João Mendes-Lopes, Aleksandra Cvetkovic, Yupin Sun, Juan Carlos Miñano, Julio Chaves, and Rubén Mohedano "1000x shadow-free mirror-based Köhler concentrator", Proc. SPIE 8468, High and Low Concentrator Systems for Solar Electric Applications VII, 84680C (10 October 2012); https://doi.org/10.1117/12.931657

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