With two units at Koeberg nuclear power station likely to be out of commission at the same time, Eskom will struggle to keep the lights on, said Electricity Minister Kgosientsho Ramokgopa.
Eskom will resort to load-shedding again from 5pm until 5am on Wednesday as demand is expected to exceed capacity by some 9 000 megawatts at peak hour, chief executive André de Ruyter told a media briefing.
“The available capacity that we anticipate to have at our disposal by five o’clock this afternoon is sitting at 26 665MW, and this is excluding any reserves,” De Ruyter said.
“The gas reserves are sitting at about 2 200MW. There is a shortfall of 2 945MW and hence the requirement to implement load-shedding with a load forecast for peak of 29 815MW.”
De Ruyter said load-shedding became unavoidable on Monday after unit five at Medupi tripped as a result of a steam air heater leak. The unit was returned to service shortly after 11pm. But in the meanwhile unit two at Lethabo power station in the Free State went down.
Eskom was trying to avoid firing open-cycle gas turbines to keep the lights to preserve its diesel reserves, its boss said.
“We have about 70% worth of diesel at Ankerlig … This is enough to keep all the units running for 24 hours,” De Ruyter said.
“Now, this might seem like a lot but it actually isn’t because we have to replenish the diesel by road and this creates some logistical challenges for us, [so] we need to conserve diesel at Ankerlig. We want to avoid using that as much as possible.”
Reserves at Gourikwa were at a healthier 85%, which translates into 36 hours of fueling the turbines at a full capacity.
De Ruyter said extreme flooding in KwaZulu-Natal had contributed to the current operational difficulties.
“We’ve had a significant ingress of debris into our Drakensberg pump-storage facility, so while we have grids that obviously stop debris from entering into the turbines these clog up when there is an excess of debris.
“We also have a challenge with the dams at Ingula being excessively full and this is maybe counterintuitive, but to run a pump storage facility you need two dams and you want one dam full and one dam empty and this allows you then to run water downhill through the turbine to generate electricity.”
When both dams were full, this created a generation constraint because water cannot be released from the dam upstream, as is currently the case in the province. Eskom considered the situation an emergency, but it could not carry out repairs while the flooding was still in progress.
“You will appreciate that water and electricity don’t mix, so we also have to bear in mind the safety of our crews, as well as the general public, when it comes to restoring the supply of electricity, particularly in water-logged areas,” De Ruyter said.
De Ruyter said a number of power units would be returning to service before the upcoming long weekend, including those at Camden power station that had performed poorly in the past few days and contributed to the need for load-shedding.
He said the outlook was that Eskom would continue to face generation constraints, despite plans to scale back maintenance in the winter months; therefore, it welcomed the department of energy’s announcements about bringing online new capacity from independent power producers.
Bid window five is expected to yield an additional 2 600MW over the next 18 to 24 months. Bid documents were issued for window six last week. It is expected to eventually see the same amount of power added to the grid, if all goes well by 2025.
“We eagerly anticipate the rapid conclusion of that bidding process,” De Ruyter said.
In replying to questions on the likelihood of load-shedding through the winter, De Ruyter said the outlook was “not entirely dire”, but impossible to forecast with accuracy.
The utility planned to scale back planned maintenance as it always did, and the situation would be mitigated by the fact that its plants performed better in colder, drier weather. However, half of the Koeberg nuclear plant will remain offline for the coming months.
“Unfortunately, we have to deal with probabilities: if we knew exactly when load-shedding was going to take place, it would make everybody’s lives and a challenging situation far easier.”
Eskom would release a scenario forecast on unplanned load losses at some point in the next few weeks.