Utilisation of excess power generated by stand-alone solar photovoltaic system: a case study in Uganda

Abstract

Stand-alone solar PV systems are increasingly installed worldwide. For reliability, these systems are mostly oversized because of the intermittent nature of the source of energy and to cater for days of autonomy. During periods of high solar irradiance, the energy generated by these systems exceed the electrical demand of the user, which leads to excess energy after the battery is fully charged. This energy is not usually utilised. This study aimed at designing a system that can use the excess energy for heating applications. A control circuit was designed to divert and measure the excess power after the battery is fully charged. It was noted that the excess energy depended on the solar radiation of the day and the loads used for that particular day. A 211 W DC heating element designed using Nichrome wires, clay, ceramics and copper calorimeter acted as a dump load. The performance of the heating element was tested and it was able to heat 5 litres of water to a maximum temperature of 60 oC. This water can be used for many domestic applications.