Download GIZ Report - 'Capacity Credit Studies'

Download  'Capacity Credit Studies' )

Renewable energies, such as wind energy can represent an economic and ecologic alternative for the generation of electrical energy. But besides contributing to the electrical energy supply, renewable energies such as wind energy can also have a valuable contribution to the equivalent firm capacity of a system. This means in other words, that with the addition of wind farms, the reliability of supply of a system is improved and that it is indeed possible to replace some conventional power plants by wind farms completely. The percentage of the installed wind capacity that can be considered to be “firm capacity” is named Capacity Credit and is subject to the analysis of the presented studies for the South African power system.

The studies presented in this report are based on three scenarios:

  • Scenario 1: Year 2015, 2000MW installed wind generation capacity
  • Scenario 2: Year 2020, 4800MW installed wind generation capacity
  • Scenario 3: Year 2020, 10000MW installed wind generation capacity

For each of the three scenarios, the average loss of load probability (LOLP) at the daily peak load has been calculated and has been used as the relevant reliability index for assessing the capacity credit of wind generation in South Africa.

The second part of the presented studies analyses the impact of wind generation in South Africa on the residual load, which is the remaining load that must be supplied by thermal and hydro power plants.

The analysis was mainly looking at:

  • Worst case situations with regard to wind and load variations.
  • Impact of wind generation on dynamic performance requirements.

The results of the corresponding studies lead to the conclusion that:

  • Hourly ramp-up and ramp-down rates of the residual load are comparable to the corresponding ramp-rates of the system load (without wind generation).
  • There are no increased dynamic performance requirements for the existing thermal power plants in South Africa.

This report has been commissioned by GIZ GmbH, the South African Department of Energy and ESKOM. The main author of the studies is DIgSILENT GmbH. Special thanks to Windlab Developments South Africa Pty Ltd., who delivered the wind data on which all studies are based on.