An engineering study has dispelled the myths “peddled by former Eskom executives” about the limits and costs of renewable energy capacity in South Africa.
The study was prepared for the South African Department of Energy and Eskom, and was commissioned by the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) – under the department’s South African-German Energy Programme.
It was conducted by engineering consultants Markus Pöller and Marko Obert, of Moeller & Poeller Engineering GmbH.
The study confirmed that the South African power system will be sufficiently flexible to handle large amounts of variable wind and solar PV generation.
This is relevant when considering the addition of combined cycle gas turbines (CCGTs) and open cycle gas turbines proposed in the Draft IRP 2016 Base Case.
To cope with increased flexibility requirements resulting from the installation of wind generation and solar PV by 2020, existing and planned power plants can be used at moderate additional costs.
By 2030, the addition of CCGTs will also reduce the cycling requirements of coal-fired power stations, even with 20GW of additional rooftop solar PV, stated the report.
In the case of high rooftop solar PV installations (10GW in 2020, and 20GW in 2030), it is recommended to move pumping operations of pumped-storage power plants from night to midday, when residual load is at its minimum value.
This relaxes the residual load requirements and allows coal-fired power plants to operate at higher levels. It can also help reduce the amount of curtailed solar PV energy.
Up to 2020, the allocated operating and emergency reserve does not need to be increased, even when adding 10GW of additional rooftop solar PV.
Up to 2030, the operating and emergency reserve will still be sufficient to balance the increased variability of wind and solar PV generation capacities proposed in the draft IRP 2016 Base Case, stated the report.
To ensure secure and cost-efficient operation of the power system – even with high levels of wind and solar PV generation – the report makes the following recommendations:
- Application of professional short-term forecast tools/services for wind and solar PV prediction, including a system for short-term prediction of rooftop solar PV.
- In the case of high solar PV installations: Allocate higher levels of operating reserve and emergency reserve in the afternoon hours.
- In the case of high solar PV installations: Operate pumped-storage power plants in pumping mode during midday, when residual load is at its minimum value.
The study confirms that large penetration levels of wind and solar PV can be handled by the South African power system from an active power balancing point of view, at moderate additional costs.