The South African power system is severely constrained and will remain tight until at least the end of April, according to Eskom. The company generates approximately 95% of the electricity used in South Africa and approximately 45% of the electricity used in all of Africa.

In a media presentation, CEO Tshediso Matona explained that Eskom’s reserve margin is very low and that the company does not currently have enough capacity to meet demand. The situation has necessitated planned, controlled, and rotational load shedding to protect the power system from a total countrywide blackout.

The company says it avoided load shedding over the past seven years by subscribing to a “keeping the lights on at all costs” philosophy. As a consequence, much needed maintenance has been postponed over the years, resulting in a severe maintenance backlog and an increase in equipment breakdowns.

One measure Eskom uses to track reliability is its unplanned capability loss factor (UCLF). An increasing UCLF percentage indicates deteriorating plant health. From 2005 through 2009, the UCLF averaged 4.43%. However, since that time, as more and more maintenance has been deferred, the percentage has risen steadily, reaching 14.85% by the end of 2014.

“We have arrived at a point that does not allow us to ignore the health of our plants,” Eskom said. “Our reserve margin is so thin, that every incident creates a major systems issue and could also have safety implications for the plant. The massive usage of diesel helps to bridge the problem somewhat, but can’t help the systemic healing and a shortage of capacity for the coming three years appears to be unavoidable.”

This summer has seen increased use of open cycle gas turbines and other reserves to balance supply and demand, but Eskom says, “new generating capacity and other levers are needed in order to ease the pressure on the system.”

The maintenance season in South Africa is usually from September to mid-May—the Southern Hemisphere’s summer—when Eskom typically sees lower demand for electricity. This year, planned outages will place additional stress on an already fragile system. Unit 1 at the Koeberg Power Station—the only nuclear power station in Africa and Eskom’s self-proclaimed best in class operator—is expected to come offline on Feb. 9 for a lengthy refueling outage, which will remove 900 MW from service (Figure 6).

6. Koeberg Power Station is like a beacon in the night. With an average availability over the last three years of 83.1%, Koeberg is Eskom’s most reliable power station. Courtesy: Pipodesign/Phillipp P. Egli

Eskom completed a return-to-service program in 2014 that included re-commissioning three previously mothballed coal-fired stations, including the Camden Power Station, a 2014 POWER Top Plant award winner (see the October issue). More capacity is needed though. In the first half of 2015, the 100-MW Sere wind farm is expected to enter service along with the first of six 794-MW coal-fired units at the Medupi facility, a greenfield project. Other capacity additions will follow, including the Ingula Pumped Storage Scheme Project next year and the 6 x 800-MW Kusile Power Station Project beginning in 2017.

For the time being though, load shedding will be the norm. Eskom predicts insufficient generation capacity and a high probability of load shedding on 62 of the 89 days from Feb. 1 through Apr. 30. It says that there is a medium probability of load shedding on 18 additional days during the period, leaving only nine days in which generation capacity is expected to be adequate—mostly over weekends.

Aaron Larson