Evaluation of Albedo for Rooftop PV in a Desert Climate

Ground albedo is an essential parameter for tilted PV systems and modelling, with growing interest recently thanks to the adoption of bifacial PV systems. On rooftop installations in which the solar panels are not on the plane of the rooftop (e.g. on horizontal roofs with elevated solar panels), the albedo of the particular rooftop surface should be assessed, not only with proper spatial but high temporal resolution. This article presents an analysis of albedo at the rooftop of a building in a desert location, which presents relatively low frequency of rain but high frequency of dust events. High temporal resolution measurements (one-minute) are collected and analysed; the average albedo is found around 0.4, but large variations (reductions in albedo) are found by rain and, to a lesser degree, by dust events, not only across days or seasons, but within the day as well, highlighting the importance of not relying on one single value for albedo.