Prototype super-capacitor photovoltaic streetlight with xLogic SuperRelay functionality

Abstract

In this paper, the authors present and discuss the design of a prototype super-capacitor photovoltaic (PV) streetlight with xLogic SuperRelay (PLC) functionality. Deep-cycle batteries used in solar electrical systems, generally have low efficiencies, long charging times, are temperature sensitive and have a limited amount of charging and discharging cycles. This paper evaluated the effect of super-capacitors as an energy source for a PV streetlight in South Africa. An xLogic SuperRelay (PLC) is used to control the charging and discharging profiles of the super-capacitors and deep-cycle batteries. The following three design topologies are evaluated and presented: 1) deep-cycle batteries as an energy source, 2) super-capacitors as an energy source, 3) combination deep-cycle batteries and super-capacitors as an energy source. The experimental results obtained show that the deep-cycle batteries provide a constant supply to the load, while the super-capacitors charge and discharge with a linear curve. The results show that it is too expensive to replace deep-cycle batteries with super-capacitors, but a combination provides the most energy efficient solution