A continuing decline in the performance of the Eskom coal fleet drove yet another “intensive” period of load-shedding in South Africa during the first six months of 2021, when rotational power cuts were implemented for 650 hours, or 15% of the time.

A new Council for Scientific and Industrial Research (CSIR) Energy Centre analysis shows the average energy availability factor (EAF) of the coal fleet slumped to 61.3% during the period, materially below the 65% average EAF reported in 2020, as well as the 66.9% of 2019 and the 71.9% of 2018.

Compiled by CSIR’s Joanne Calitz and Dr Jarrad Wright the report estimates a load-shedding upper limit of 1 284 GWh for the period, relative to actual energy shed of 963 GWh.

The authors describe the six months as a “difficult” period of load-shedding, which was implemented mostly at Stage 2, representing 2 000 MW of cuts.

It follows South Africa’s most intensive full year of load-shedding in 2020, when 1 798 GWh was shed by Eskom.

Load-shedding during the first half of 2021 was equivalent to more than 70% of that 2020 record and took place during every month, with the months of March and June being the most negatively affected.

“The Eskom fleet EAF declining trend continues and drove load-shedding events in the first half of 2021, with specific concerns surrounding unplanned capacity load factor trends,” the CSIR reports notes.

Unplanned outages were recorded at 24.5% during the period, while planned outages stood at 11%, notwithstanding the utility having embarked on a ‘reliability maintenance’ programme to address backlogs that have made the coal fleet unreliable and unpredictable.

“The best hourly EAF of the first half was 73.7% and the worst was 51.5%,” the report states, highlighting that unplanned outages affected 10 000 MW for 81% of operating hours during the period.

South Africa has a nominal coal capacity of 38 700 MW in an overall system that has a nominal capacity of 52 600 MW.

Coal, thus, continued to contribute the lion’s share – 94 TWh, or nearly 82% – of the country’s electrical energy during the period.

System demand increased by 5.4 TWh, or 5%, relative to the first half of 2020, when South Africa implemented a hard lockdown in response to the Covid-19 pandemic.

Nevertheless, demand was 2.5 TWh, or 2.2%, lower than that experienced in the same period of 2019.

During the six months, South Africa’s 5 300-MW-strong wind and solar fleet supported a 65% reduction in high-demand hours (those hours when system demand exceeds 30 000 MW) from 280 hours to 97 hours, but contributed only modestly (0.3 GW) to reducing peak demand.

Renewable energy contributed 12.4 TWh, or 11%, to system demand, of which variable renewable energy contributed 6.8 TWh, or 6%.

Nuclear, by contrast, contributed 4.3 TWh, or 3.7%.