How clever Capetonians lessen the effects of Eskom's load-shedding
While the rest of the country experienced stage 2 load-shedding on Wednesday, people who get their electricity directly from the city of Cape Town have spent less time in the dark.
This is because of the Steenbras hydropower station.
On Thursday, the metro said that while there was stage 2 load-shedding for Eskom-supplied customers, it was only stage 1 for city-supplied customers.
Stage 1 requires the least amount of load-shedding - three times over a four-day period, for two hours at a time compared with stage 2 load-shedding which doubles the frequency of cuts, meaning there is no power six times over four days, for two hours at a time.
Phindile Maxiti, the city’s MMC for energy and climate change, said on Thursday that Cape Town was the only South African city which owned and operated a large hydro-electric pumped storage scheme - the 160MW Steenbras hydropower station, which manages the city’s power load.
Maxiti said the hydro-electric pumped storage scheme included the construction of the Steenbras Upper Dam, which was operated by the city's water department.
"The station consists of four pump/turbines which are used to generate electricity using the gravitational force of water flowing from the Upper Steenbras Dam to a reservoir below the station.
"This is done when the load is high during peak times or when there is insufficient energy to meet the demand, for instance load-shedding," Maxiti said.
Maxiti said when the load was low and there was sufficient electricity - say between 11pm and 7am - the pump and turbines were used to pump the water back to the Upper Steenbras Dam so it could flow down again during the day, generating electricity.
"The power station operates like a battery. The amount of electricity that it can generate in a day is limited only by the capacity of the lower reservoir," Maxiti said.
He said Steenbras power station had been put to work to successfully offset load-shedding in Cape Town, at least in the lower stages of load-shedding, for city-supplied customers.
"For instance, if Steenbras has spare capacity, the city customers can likely be protected at stages 1 and 2 from Eskom’s load-shedding - if conditions are appropriate.
"So that is why if Eskom announces stage 2, we can help city customers by keeping load-shedding at stage 1 when it is possible to do so," Maxiti said.