Windlab have made a significant contribution to a capacity credit study that has assessed the contribution of planned wind generation in South Africa to the firm capacity of the South African power system.

The capacity credit of wind energy study was undertaken by DIgSILENT GmbH, and was commissioned by the Department of Energy, power utility Eskom and German development institution GTZ, with input contributions from Windlab.

Windlab's involvement
Windlab provided modelled wind data for a set of proposed wind farm development locations across South Africa. DIgSILENT incorporated these hourly outputs of wind speed into a dynamic network model to provide an indication of the capacity credit of proposed wind developments in South Africa.

These services were based on application of Windlab's WindScape™ atmospheric model to produce a 100m resolution wind atlas of South Africa.

WindScapeTM has been validated against monitoring towers and operating wind farms across the globe and has been applied byWindlab for public planning purposes around the world, including the Australian Wind Atlas.

Findings of the study
The study analysed three scenarios:

Scenario 1: 2 000MW of installed wind generation capacity by 2015

Scenario 2: 4 800MW of installed wind generation capacity by 2020

Scenario 3: 10 000MW of installed wind generation capacity by 2020

Preliminary findings indicate capacity credit figures in the range of 23.5% to 30.6% across the various scenarios. With the outage rate of newly planned and existing coal fired power stations in South Africa factored into the study, the capacity credit of wind generation in South Africa was found to be between 26% and 38% of the corresponding contribution of new and existing coal-fired power stations.

Corresponding studies were performed with regard to the impact of wind generation in South Africa on the residual load, which is the remaining load that must be supplied by other power plants. The key findings were that ramp rates are comparable before and after inclusion of wind on the system and that there are no increased dynamic performance requirements for the existing thermal power plants.

The final results of the study will be published before the end of 2010.

For more information, read Eskom to publish grid-connection road map by year-end.