Solar PV generation enhancement using radiation augmentation from improved reflectance horizons

Abstract

The total incident irradiation on a surface such as a photovoltaic (PV) module is the sum of beam, sky-diffuse and ground reflected radiation. Ground albedo or ground reflectance is defined as the ratio between the ground reflected radiation and the global incident radiation. A constant albedo value of 0.2 for bare ground and 0.5 for dry tropical localities is widely accepted and is used in the modelling of PV systems. The real albedo values of foreground surfaces are different and hence using a constant value may be unsuitable to accurately predict the output of PV systems. This research investigated the real albedo values of various foreground surfaces and how it is affected by the factors such as ageing, solar altitude, rain and cloud cover (sky conditions). To investigate the impact of such factors, an experiment was setup to measure the albedo of conventional foreground materials (grass, sand and cement) and non-conventional materials (white pebbles, white paint, white tiles and aluminium foil). These materials were selected based on the type of PV applications such as solar farms and Building Applied Photovoltaic. The measured average albedo values of grass, sand, cement, white pebbles, white paint, white tiles and aluminium foil were 0.20, 0.36, 0.56, 0.15, 0.70, 0.61 and 0.73 respectively. Research has shown that non-conventional materials, increased the slope irradiation and ultimately the energy generation of PV modules. These results were further validated using the long-term data from the Garston and Edinburgh database. Lastly, a new computational tool was developed, which considers various albedo values of foreground materials simultaneously for any tilt angle of a PV module to compute the ground-reflected component.