Combining grid-tied PV and intelligent water heater control to reduce the energy costs at schools in South Africa

Abstract

South Africa's escalating electricity rates are increasingly diverting educational resources to utility bills. Recent advances in solar PV affordability, the advent of the smartgrid and the capacitive nature of water heaters could be combined to enable new methods for electricity cost and efficiency management without affecting user comfort. Control methods that combine excess PV energy dumping and real-time temperature-based prioritised scheduling were compared with the normally-employed thermostat control. In addition, the performance of an energy-optimising approach is compared with a peak demand optimising approach. The results show that peak demand limiting with a two-temperature thermostat provided the highest cost saving with a 30% reduction of the school's electricity cost and only a 0.2 percentage point reduction in the number of warm water events.