Abstract
Point source, pillbox and circumsolar ratio-dependent extended light source Sun models are used as solar source inputs into an analytical optical ray trace model for the calculation of plane restricted illumination profiles generated by three example lenses. The example lenses are: a low iron soda-lime glass plano-convex lens, a poly (methyl) methacrylate (PMMA) 3-facet Fresnel lens and a PMMA 20-facet Fresnel lens. Significant differences in illumination profiles are found with solar source description variation. Most notably, it is found that chromatic aberrations and spectrally variant effects specific to the multi-junction solar cell architecture are only identified using the extended light source Sun model. The spectral dependency of material optical properties are analysed in the context of the multi-junction cell architecture by means of spectrally weighted averages corresponding to the active range of the sub-cells.
Highlights
Concentrating photovoltaic (CPV) systems typically utilise high-efficiency multi-junction solar cells (MJSCs) for the conversion of solar power to electricity
The CPV system offers an economically viable terrestrial application of MJSCs whereby their relative expense is offset by the use of optical concentration systems
Given that the validity of approximated solar source descriptions is called into question when modelling optical systems with small entry apertures, CPV, high concentration photovoltaic (HCPV) – where input aperture half angles are often in the sub-degree range, system modelling requires the use of extended light source Sun descriptions in order to accurately identify the MJSC illumination profiles
Summary
Concentrating photovoltaic (CPV) systems typically utilise high-efficiency multi-junction solar cells (MJSCs) for the conversion of solar power to electricity. MJSCs have significantly higher efficiencies than their archetypal counterparts, single-junction solar cells. A major application of MJSCs is found in the space power industry where their expense is of no real concern as their high-power per unit mass ratio takes precedence in design considerations. The CPV system offers an economically viable terrestrial application of MJSCs whereby their relative expense is offset by the use of optical concentration systems. This offset by concentration is possible because the multi-junction cell architecture is inherently much more efficient at heat management than the single-junction and can withstand much greater light intensities. There are two major elements involved in modelling the behaviour of optical concentration systems, namely: solar source descriptions and concentration components (lenses)
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