Longest break in load shedding

By yesterday morning, South Africans would have had a 10-day reprieve from load shedding – with no rotational blackouts since 5am last Tuesday.

Stage 2, which had been planned overnight from 4pm that day, was not required. This is the longest break in load shedding since 15 December to 2 January. Four major factors contributed to this. Rather obviously, there has been lower demand because of the Easter long weekend from Friday 29 March to Monday 1 April. The real impact of this was only seen over those four days, when peak demand was between 3 000MW and 5 000MW lower than the same weekend of the 13th week of last year (which wasn’t Easter).

This is equivalent to between three and five stages and saw the utility’s operating reserve margin return to above 20% – levels not seen since the festive season. This had a big impact over the weekend; however, this is no slam dunk.

Demand was back to “normal” levels of around 27 600MW on Wednesday night (3 April). This is slightly lower than last year – about 1 000MW less – possibly due to the impact of residential and commercial solar and battery installations.

Further data is required to prove this. Second, Kusile Unit 5 is contributing as much as 720MW to the grid – likely in the evening peak. Eskom categorises it as a “noncommercial” unit because, while it has been synchronised to the grid, it has not yet achieved commercial operation.

This is typical as new units are built and brought on stream. You can be sure that Unit 5 is being ramped up in the afternoons and idled down after the evening peak daily.

Aside from lower demand – which was temporary – the main reason for the absence of load shedding is that, simply, the coal fleet is performing better than it has in months.

Eskom’s data is somewhat iffy (given that 1 April is its new financial year), but its coal power stations generated over 20 000MW in the evening peak on Monday and both peaks on Tuesday. In fact, on Tuesday evening, Eskom managed to get nearly 21 000MW out of its coal fleet later in the peak (around 8pm).

On those two days it had no reason to use its diesel open-cycle gas turbines (OCGTs), or those of independent power producers. The lower temperatures definitely help as partial load losses caused by sweltering heat reduce. According to Eskom data, the level of unplanned outages is 2.5 percentage points lower than in the same week last year.

Planned maintenance is 1.6 percentage points lower, which, together with a reduction in other outages, means that Eskom’s energy availability factor (EAF) – a measure of generation capacity – is nearly five percentage points higher this year (57%) than the same week last year. The reduction in planned maintenance can be expected given the Easter break.

The final reason for the break in power cuts has been that renewables are pulling their weight. In the late afternoons and evenings, wind is making a meaningful contribution. In the past nine days, this has varied from 1 000MW to 2 200MW – with only a small portion coming from concentrated solar power.

Private solar is also doing the job of between 2 000MW and 4 000MW each day.

Four major factors have contributed to this