Optimal energy management and economic analysis of a grid-connected hybrid solar water heating system: A case of Bloemfontein, South Africa

In this paper, the optimal energy management of a hybrid solar electric water heater is presented. A typical medium density household is considered. Actual historic exogenous data, obtained from a weather station in the considered area is used as input for the established model. The aim is to evaluate the energy and cost saving potential of the system, that may be achieved under time-based pricing, while maintaining a comfortable thermal level of the hot water user. Comparisons between the operation of a thermostatically controlled traditional electric storage tank water heater and the hybrid solar electric water heater, offered an energy saving of 75.8% in the winter and 51.5% during the summer period. A life cycle cost (LCC) analysis is presented, where the project lifetime is taken over 20 years. The LCC analysis of the hybrid system demonstrates a 44% saving in overall cost, as compared to a traditional water heating system. Simulation results conclude that the break-even point for the evaluated system was at R10 870 in 3.3 years, under the evaluated time-based pricing structure.