Autonomous street lighting system based on solar energy and LEDs

This work presents an autonomous street lighting system based on solar energy as primary source, batteries as secondary source, and lighting emitting diodes (LEDs) as lighting source. This system is being presented as an alternative for remote localities, like roads and crossroads. Besides, it presents high efficiency, because all power stages are implemented in DC current. The design of LEDs fixture, in order to replace a 70W high pressure sodium (HPS) lamp, is performed. This design takes into account the human eye response in scotopic conditions. LEDs driver and battery charger experimental results are presented. The battery charger presents three control modes: maximum power point tracker (MPPT) mode; constant current mode; and constant voltage mode. The control mode depends on the battery state (charged/discharged), and solar irradiance level. The battery charger input impedance is analyzed in order to ensure that the MPPT is obtained for any solar irradiance and panel temperature.