An airconditioned nightmare for Eskom
Heatwave boosted demand and reduced plants’ efficiency
● A surge in the use of airconditioners and fans by “affluent” South Africans during the heatwave of recent weeks is partly to blame for the latest descent into stage 6 load-shedding, a senior Eskom executive says.
“The heatwave put us in a bad position. We had failures on some units, and I know we use the term ‘unexpected’ very loosely, but these failures we did not anticipate,” Karabo Rakgolela, general manager of Lethabo power station, told the Sunday Times.
Rakgolela is a senior member of Eskom’s management team, having been the cluster manager for Lethabo, Matla, Kusile, Kendal and Grootvlei power stations.
He said shutdowns for planned maintenance had contributed to the need for higher levels of load-shedding.
“We had a stable grid for most of September and October and two weeks ago suddenly the problems started when we started seeing the partial load losses begin to climb. I can place a lot of the reasons for our current problems at the door of the extreme swings in temperature we had,” Rakgolela said.
“We were also not helped by some units tripping. We worked hard to get these tripped units back on load but we were not getting them back on load fast enough.”
This forced Eskom to make inroads into its emergency water and diesel reserves.
“The Sunday just before Black Friday, we had some units down, and we had started recovering them when we were hit by the incredible heatwave, and suddenly usage spiked by about 1,500MW ... 1½ stages of load-shedding.”
This forced implementation of stage 6 to protect the grid.
“That is the last outcome any of the 15,000 people fighting to fix these issues wanted. We were still having consultations between the executive committee and other senior managers at 1am that Monday morning.”
Summer traditionally brings a reduction in energy consumption, but, Rakgolela said: “In a heatwave such as this recent one you can see the usage go up as the entire affluent South Africa switches on their airconditioning and fans, and that usage stays up as long as it stays warm.”
The rising temperatures brought other complications. “As Murphy would have it, we started having tube leaks and units tripping. We ended up running on diesel deep into the night,” Rakgolela said.
Planned maintenance shutdowns complicated matters further. “We also switched off a lot of our units in the summer for planned maintenance to be ready for the higher demands of the winter next year. Currently we are sitting on about 6,000MW switched off for this reason. Soon we will be picking this up to about 10,000MW.
“Our summer plan was to take off about 14,500MW for planned maintenance, but if you add the 6,000MW we lost this comes to 20,500MW that is unavailable, leaving us with about 25,000MW to service the entire grid,” Rakgolela said.
Energy analyst Clyde Mallinson said he both “agrees and disagrees” with Rakgolela. “Yes, the heatwave accentuated the problem, but I made a model in January this year according to which we would be on stage 6 now anyway, and that is exactly what happened,” he said.
Failure to do maintenance timeously was the root issue, said Mallinson. “At my age you have to visit your doctor once a year. You can’t skip these visits for five years, then go see your doc five days in a row. When it comes to increased maintenance, Eskom is trying to visit their doctor five days in a row.” Eskom spokesperson Daphne Mokoena said as of Friday, 14 units were on planned outages, which “equates to 6,443MW”.
Apart from increased demand from airconditioners, hot weather affected the performance of power stations. “The exhaust steam from the turbines requires cooling before it can be returned to the boiler tubes. The cooler the ambient temperature, the more efficient this process is. When the weather is hotter, there is an efficiency loss and thus a loss in MW produced,” Mokoena said.
On the diesel reserves used in the open-cycle gas turbines (OCGTs), she said Eskom has a budget of about R30bn for all OCGTs for the 2024 financial year. As Eskom cannot borrow more in terms of Treasury conditions, should Eskom require more funds for OCGTs, this will have to be cash from other operations.”