Loadshedding-induced transients due to battery backup systems and electric water heaters

Loadshedding has become the norm in South Africa, with rolling blackouts ranging from Stage 1 to 6. This results in households experiencing disempowerment for durations spanning two to four hours daily, averaging between 1.5 to 9 h. In an unequal society like South Africa, those with higher energy consumption can afford battery backup solutions to keep their lights on. However, implementing these solutions on a large scale, without integrating solar generation, eventually alters the utility’s ability to stabilise the grid and prevent blackouts through shedding the load. We analysed an electricity dataset including 6724 households to assess the impact of domestic users adopting battery backup solutions, both with and without solar components, at a 15% penetration level. The findings revealed that installing batteries with inverters (termed battery backup systems in South Africa) without a photovoltaic setup would increase the instantaneous load of zones that are exiting loadshedding due to the backup batteries being recharged from the grid. This would counteract the load reduction that is achieved by the zones that are entering loadshedding. In summer, during the evening peak, the load increase due to recharging the backup batteries would be 1.81 times the load reduction due to the loadshedding, (In winter, it would be 1.67 times.) However, households with a PV-connected inverter and a PV-connected electric water heater would experience a different outcome. In summer, during off-peak hours, the peak load reduction due to PV would be 2.27 times the load reduction due to load shedding. (In winter, it would be 0.91 times.) This suggests that during summer off-peak daylight hours, at least two stages of loadshedding (10% of the overall energy demand) can be mitigated, while in winter, nearly one stage of shedding can be avoided on a typical day. However, storage-less PV installations cannot mitigate loadshedding during the morning and evening peaks when there is little to no power generation from the solar panels.