Should we point them away from the sun? -A study in PV spectral tracking in a Scandinavian climate

Sammanfattning: Conventional photovoltaic solar tracking is commonly done by aligning the surface normal of a PV module with the direction from which direct solar irradiation is coming from. While this tracking design has proven to perform well in sunny climates, solar tracking is altogether less common in northern climates where the direct solar irradiance is weaker. In this study a radiative transfer model is used to approximate the wavelength distribution of incident solar radiation reaching Visby on the island of Gotland in Sweden during 2011 to investigate if the site specific irradiation of a northern climate in combination with different PV materials optical properties can result in circumstances where there are more productive things to track than the direct solar irradiation. The results of the study indicates that the performance of a tracking system to some extent depends on the choice of PV cell material used in the system and that the spectral response of different materials often make them achieve optimum productivity at slightly different tilt/azimuth combinations. The study concludes that a conventional tracking system in Visby during 2011 in general would generate approximately 10 kWh/m² less electricity compared to a theoretically optimal tracking system.