Sky status: A local analysis of ground based digital images

Abstract

Cloud coverage obscures the sunlight, it can be identified as the major factor that significantly decreases the total irradiance received by photovoltaic panels, and then the power generation is intermittent. In this paper, and in order to predict the energy production by a solar installation, we analyze the acquired ground based images of the sky to extract its actual status (clear, partially cloudy, or totally cloudy). An embedded system is dedicated to simultaneously capture images and estimate the power generation. The accurate sky status is determined by comparing the brightness of the sun zone in the digital image to its surrounding area. The experimental results are promising and shows that the developed techniques can be easily embedded in solar plants to accurately predict the short time energy production.