Eskom’s newly released Medium-Term System Adequacy Outlook (MTSAO) report highlights several risks to South Africa’s electricity supply for the period 2018 to 2023 and indicates that additional capacity will be required during the period to restore generation adequacy should the energy availability factor (EAF) from the coal fleet fall below 75%.
The document tests six EAF scenarios across two demand forecasts: a moderate demand scenario, represented by average yearly growth of 1.9%; and a low demand scenario of 0.64% a year over the five-year period.
At an EAF of 71%, the system is inadequate, regardless of demand growth, while at 73%, the system is inadequate for moderate demand growth. At an EAF of 75% or above, the system is adequate for all demand forecast scenarios considered.
In 2017/18, Eskom reported an EAF of 78%, but the performance of the fleet has come under pressure this year as a result of coal shortages at ten of Eskom’s 15 coal-fired power stations, as well as a fatal incident at the Lethabo power station in early October. Lethabo Unit 5 will be out of service for a minimum of three months as a result of the incident.
The risks to future system adequacy outlined in the MTSAO included:
Any deterioration in plant performance as a result of insufficient plant maintenance.
Any earlier shutdowns, for economic or other reasons, of Eskom and/or non-Eskom generation units.
Insufficient coal at power stations as a result of low coal stockpile levels, or the unavailability of suitable coal.
Load losses, or the shutdown of generation units or stations as a result of Eskom’s failure to comply with air quality standards.
Longer-than-planned shutdowns to allow for the retrofitting of plant to comply with environmental legislation.
Any switch back to Eskom supply by non-Eskom generators, which would increase demand on the system.
And any delay to the commissioning dates for Eskom or independent power producer (IPP) plant.
“Should these risks materialise, it would have severe negative implications for the adequacy of the system,” the report states, concluding that the system will be adequate for the two demand scenarios studied with an EAF at 75% and above.
However, a deteriorating EAF, or any increase in demand, will have an impact on adequacy, which could be exacerbated if one or more of the identified risks materialises.
The report says care must be taken to mitigate the risks of a shortage of coal and potential impacts of the minimum emission standards (MES) on the available capacity of the system.
For the purposes of the MTSAO assessment, it was assumed that the MES will not have an impact on the availability of generation plant and that sufficient provision has made for planned outages to complete the required retrofits.
Nevertheless, Eskom cautions that a number of units will be impacted and may have to be de-rated or shut should emission projects not be concluded, or should the Department of Environmental Affairs disallow additional postponements for power-station compliance.
In 2015, Eskom’s power stations were granted a five-year extension to comply and MTSAO indicates that the utility is in the process of applying for further postponements for the full implementation of the MES.
The MTSAO is also not fully aligned with the draft Integrated Resource Plan 2018, which states that a combination of solar photovoltaic, onshore wind and flexible generators, such as gas, would be the least-cost new-build solution for South Africa to meet demand to 2030.
By contrast, the Eskom document foresees meeting any possible generation-adequacy gaps through the traditional framework of baseload, mid-merit and peaking generation investments.
However, the MTSAO also states that the “optimal investment (in terms of quantity and timing) in capacity should be informed by a long-term planning study, such as the Integrated Resource Plan”.