By Jamie McKane for MyBroadband
Eskom has provided a detailed explanation of how its low energy availability will result in an increased risk of load-shedding this year.
A recent report published by the Council for Scientific and Industrial Research (CSIR) found that Eskom’s low Energy Availability Factor (EAF) was a driving force for the record-breaking load-shedding last year.
“Eskom fleet EAF is on a declining trend and drove load-shedding events in 2020,” the CSIR noted.
EAF measures plant availability including planned maintenance, unplanned breakdowns, and energy losses not under plant management control.
The statistics reveal that load-shedding occurred for 859 hours of 2020 (9.8%) despite a reduction in demand during the national COVID-19 lockdown.
This is bad news for 2021, as Eskom’s EAF has continued to drop into 2021, which will likely result in increased load-shedding until this improves.
According to Eskom’s latest weekly generation availability report, the average EAF for the year to date is only 58.55%.
In response to questions from MyBroadband regarding the effect of its declining EAF on load-shedding, the power utility said that lower EAF figures increase the risk of load-shedding.
“It is correct that as EAF drops, all other factors remaining the same, the risk of load shedding would increase,” Eskom told MyBroadband.
Falling energy availability means more load-shedding
Eskom said that its power system was currently constrained, a state partly due to the low EAF of the generating fleet. Load-shedding is subsequently required to correct this supply/demand imbalance.
The power utility also said, however, that EAF was only one half of the equation – the other being the demand it needs to meet.
“The dispatchable generation is required to meet the residual demand,” Eskom said.
“This residual demand is the total customer demand of the country less the power supplied by the renewable generation (wind generation, solar generation, concentrating solar power generation, biomass generation etc.) ”
“The residual demand is, therefore, made up of customer demand and the contribution from the renewable generation,” it said.
Each of these factors is variable, and the variance determines the strain on the system and the risk of load-shedding.
“In the case of the renewable generation, the contribution is dependent on wind and solar radiation and there is a strong seasonal effect on the wind generation,” Eskom said.
“The customer demand is also variable changing in the range of 22GW to 34GW over the year with higher demand during the winter months.”
“In general, lower EAF combined with high residual demand will result in load-shedding. Load-shedding is also unfortunately required when the fleet availability drops even further from the average availability for more than a few days.”
Eskom added that it is the generally low EAF coupled with the unreliability and unpredictability of the plant that results in load-shedding.
“All factors must improve to significantly reduce the risk of load-shedding,” it said.
Why EAF is falling
Eskom’s EAF is continuing to decline due to a number of factors, the most prominent of which is power plant failures and breakdowns.
“The major contributors to unplanned energy losses (UCLF) are partial load losses (where units are unable to operate at full load), boiler tube leaks, trips, outage slip and other full load losses,” Eskom said.
It should, however, be noted that Eskom is also conducting reliability maintenance on its power plants, which means that a portion of its fleet is taken offline for extended periods to resolve major issues and defects.
Once this program is complete, Eskom said it expects the risk of load-shedding to decline somewhat. However, while EAF may improve, the power utility still faces a significant capacity shortfall for the next five years.
“Eskom’s generating fleet is unreliable and unpredictable,” Eskom said.
“Together with focussed attention on the areas that contribute most significantly to load losses, Eskom has been embarking on a programme of increased much-needed reliability maintenance.”
“Only once that programme has been completed can we expect the plant performance to become more reliable and less unpredictable,” it said.