State-owned power utility Eskom is in the process of compiling a connection-capacity document to provide private power developers with improved visibility of the immediate grid-connection options in South Africa- the document will be published before the end of 2010.
Proximity to the existing grid was likely to be a key consideration for the first tranche of renewable energy feed-in tariff (Refit)-related projects, which were required to be contributing some 1 025MW to the grid by 2013. Of this, 700 MW has been set aside for wind under the first integrated resource plan (IRP1).
Such proximity to the grid is important, because any extension of the transmission system, as well as the related environmental impact assessments (EIA) for new transmission lines and substations, could take as long as five years to finalise.
Connection projects that would require deep or upstream reinforcements could only be connected within four to six years, owing to EIA-related constraints. Therefore, projects in such areas would likely not be considered under the first Refit phase, Eskom grid planning department chief engineer Kevin Leask said on Wednesday.
Therefore the first IRP1-alienged projects would likely have to be “cherry picked” based on ease of implementation, but geographic diversity was also expected to play a role.
Leask added that developers should be realistic in the timing of their projects, and it was not a matter of the system operator not being able to take the megawatts, but rather a question of what the cost of integrating those megawatts would be, and how long it would take.
Developers would be given an indication of this with the connection capacity document.
Under the Integrated Resource Plan 2010 (IRP2010) it has been proposed that some 3,8 GW of wind be brought onto the system between 2014 and 2020, while beyond 2020, renewable energy contribution to the grid should be as much as 7,2 GW.
Owing to grid connection limitations, Eskom was advocating a three-tiered approach for connection of renewable energy into the transmission grid.
The first level would be to connect projects that would not require power transmission reinforcement, and were at the 132-KV level. This, reiterated Eskom, would be the only way to connect projects to the grid in a way that met the renewable energy targets of 2013.
The second level was described as the medium-term outlook, to connect projects between 2014 and 2020, and this would identify larger projects of either 132 KV or 400 KV. The grid could be extended to ‘fetch’ power from these projects, but would not be reinforced. The projects could be connected directly to existing substations and power corridors at 132 KV or 400 KV with relatively minimal localised transmission reinforcement.
The third level was a longer-term strategic outlook beyond 2020, where transmission corridors could be created once variables had been proven. It would be based on more strategic development decisions to create transmission hubs.
Leask maintained that a geographical diversification of renewable energy connections would be important under the first Refit allocations to 2013, and should play a role in the decision making of who was awarded a license.
He said it would be preferable if projects were spread out, as this would be supportive of overall system stability. Owing to its intermittent nature, wind projects could also have an influence on such stability.
But the introduction of wind and other renewables would also allow for real time data collection, and would allow the system operator to gain experience in operating renewable energy generation with minimal risk and develop the necessary procedures to enable connection or larger amounts of renewable energy generation.
Further, it would also maximise the use of existing transmission infrastructure, before investing in new infrastructure.
All future generation projects, including Eskom projects, would be assessed on a case-by-case basis ahead of licencing.
The Eskom executives were addressing wind project developers at a stakeholder presentation on the “capacity credit of wind energy in South Africa”.
The capacity credit of wind energy study was undertaken by DIgSILENT, and was commissioned by the Department of Energy, Eskom and German development institution GTZ, with input contributions from Eskom and Windlab.
DIgSILENT researcher Markus Pöller said that the main conclusions form the study showed that the credit capacity of wind generation in South Africa could be expected to be in the range of 25%. This was said to be in line with expectations.
He added that the main impact on system operation would be limited predictability, rather than actual load or wind variation.