Design of a solar powered LED street light: effect of panel's mounting angle and traffic sensing

Abstract

In this work, the effect of mounting angle of solar panels and traffic sensing on the requirement of system size, i.e., panel size and battery capacity, for a solar powered street light system is investigated. Street lights need more energy in winter than in summer due to longer winter nights. However, for a solar powered system, less energy is available in winter with less intense sunlight and shorter days. The mounting angle of panels has a great impact on the cumulative energy output of the panels. Our investigation shows that while a mounting angle of 23.1° yields maximum energy collection in summer and minimum energy collection in winter, a mounting angle of 46.5° increases the energy collection in winter and yields more or less uniform energy collection throughout the year. Assuming a panel efficiency of 16%, an average cumulative energy output of 950 Wh/m2/day with about 5-8% variation throughout the year has been found with a mounting angle of 46.5°. This results in about 9% reduction in the panel size than that required with a mounting angle of 231°. Moreover, installing a traffic sensor in the lighting system will allow detection of traffic density, thereby operating the lamps at different intensity levels as per requirements. This will save energy wastage in time of low or no traffic and will further relax the requirement on system size.