By Antonio Ruffini

19 July 2013 – The winter peak electricity demand from the national grid in South Africa is expected to be about 36,800 MW, with some evening peak within peak periods already having come close to this level. Eskom has a nominal capacity of almost 42,000 MW and there is another 1,100 MW of independent and municipal power producer capacity available to supply the grid.

The country’s electricity network has been operating on very thin margins during peak periods because Eskom has been undertaking maintenance on its coal fired power station fleet, work that could not be delayed, with nine units undergoing maintenance this winter. As of early-mid July, two of these had seen the maintenance work completed, work was being executed on four with the rest to be completed during the course of the winter period. There have already been occasions this year when peak capacity available to supply the system, including the emergency open cycle gas turbines, has been insufficient to meet demand, and interruptible power agreements with BHP Billiton smelters, which cover up to 2,000 MW, have had to be invoked.

Eskom has not had to enact any load shedding since the first half of May 2008. However, with the delay in Medupi’s first unit synchronisation to the grid only due in the second half of 2014 and no major contribution from the renewables facilities under construction expected before then, Eskom has estimated a shortfall in mid-merit capacity of some 700 MW next year. Plans have not yet been finalised to deal with the capacity shortfall, but it will most likely entail agreements with heavy power users to shift power usage away from the peak period, as well as deals to facilitate additional energy supply to the grid.

The slowdown in energy demand may also contribute to managing this gap as electricity sales in South Africa decreased year on year for the financial year ended March 31st 2013 to 216,516 GWh from 224,785 GWh previously. This is as economic growth slows, demand side management and energy efficiency initiatives prove effective and some large users of electricity turn to own generation projects to create flexibility for themselves.

As Brian Dames, CEO of Eskom points out, for 22 hours out of 24, Eskom has more than enough capacity to supply the grid, this increasing to some 20% in the early hours of the morning and averaging 12% during much of the day. It is only during the evening peak periods that the system is highly constrained.

The one advantage of the current electricity situation is that it is focusing a greater effort towards smoothing out the country’s electricity demand curve than might otherwise have happened.