Demand side optimal strategy for voluntary load shedding

South African electricity suppliers are considering the use of voluntary load shedding as a means of solving the country's electricity shortage. In this study, an optimization model for demand side voluntary load shedding was used to simulate a scenario involving a water supply company. The aim of the study was to determine an optimal control model for the water pump equipment while ensuring that energy and cost reductions were achieved. The water supply company consisted of 21 pumps, 3 engine rooms, and 4 destination reservoirs. The water system was modelled as a mass balance model which stated that the mass that entered the system must leave the system or accumulate within the system. A time-of-use electricity tariff structure was used. The cost function was computed over a 24 hour period. The study demonstrated that water demand can be met when 50.5 per cent of peak time energy consumption was shed, and when 12.33 per cent of energy consumption during a weekday was shed. Approximately 17.76 per cent of the corresponding energy costs can be saved by adopting an optimal load shedding strategy. Further practical applications of the load shedding model are now being investigated. 15 refs., 5 tabs., 2 figs.