Curve-Correction Factor for Characterization of the Output of a Three-Dimensional Curved Photovoltaic Module on a Car Roof

Abstract

For modeling the energy generation of three-dimensional car roof photovoltaic (PV) panels, it is essential to define a scientifically accurate method to model the amount of solar irradiance received by the panel. Additionally, the average annual irradiance incident on car roofs must be evaluated, because the PV module is often shaded during driving and when parked. The curve-correction factor, which is a unique value depending on the three-dimensional curved shape of the PV module, is defined in this paper. The curve-correction factor was calculated using a ray-trace simulator. It was found that the shape of the curved surface affected the curve-correction factor. The ratio of the projection area to the curved surface area of most car roofs is 0.85–0.95, and the annual curve-correction factor lies between 0.70 and 0.90. The annual irradiance incident on car roofs was evaluated using a mobile multipyranometer array system for one year (September 2017–August 2018). It is estimated that the effective annual solar radiation for curved PV modules is 2.53–3.52 kWh m−2/day.