South Africa - Eskom looks to wind for power

ESKOM - South Africa's almost only provider of electricity to its grid, has confirmed that it will invest R1bn in a 100MW wind farm on the West Coast to feed into the national electricity grid by the beginning of 2010.

A R5,3bn 100MW solar thermal energy plant in Upington is also under consideration. If this project is approved, the plant could come online by 2012. While small, these projects will be in operation years before the other major power stations Eskom has commissioned.

Eskom’s GM for corporate sustainability Wendy Poulton says the projects are part of Eskom’s R300bn capacity expansion and research programmes over five years, which will provide renewable energy resources from wind, sun and water. The plans for the West Coast wind farm includes building about 100 turbines over a 25km² site near the coast, in the Vredendal area. Other sites in the area are being considered for further development.

Eskom estimates that the South African coastline has potential for 1000 turbines. Poulton says the capacity factor of wind farms depends on the availability and speed of the wind. “Turbines generally operate 20% to 25% of the time, and this can vary seasonally.” The West Coast north of the Olifants River is regarded as having the highest wind speeds in the country. A precursor to the new wind farm was Eskom’s 3MW pilot study for three years in Klipheuwel near Darling in Western Cape. It found that the best energy production occurs during the windy summer months with capacity of between 10% in winter and 35% in summer. The wind turbines at Klipheuwel generate electricity at wind speeds between 11km/h and 50km/h, with full power generation only reached at about 50km/h.

The project also assessed different technological features of turbines, how to develop an operations and maintenance programme, as well as to evaluate the effect the farm might have on the national electricity grid.

The proposed 100MW thermal energy plant at Upington in Northern Cape will serve as a pilot project. It will be 10 times the size of solar power plants and use a new, but proven, technology, says Eskom's MD for corporate services Steve Lennon. He says the cost of the project is estimated at about R5,3bn. Almost all solar power is now generated through photovoltaic cells, with the largest being a 10MW plant. Alternatively, new technology concentrates the sun's rays through a parabolic mirror. The heat gathered at the focal point is used to melt salt. This molten salt then drives a conventional turbine, says Lennon. Compared with fossil fuel power generators, a R5bn investment for a 100MW power plant is high, says Lennon — “almost the same as a nuclear plant”. “If the first plant works well, the cost will immediately come down to two-thirds for the second one,” he says.

Eskom’s Research and Innovation Centre’s Louis van Heerden says Eskom has been studying the technology for several years and recent efforts have focused on reducing the technical risks associated with the use of such a new technology. Van Heerden says the main benefits of renewable energy technology are that there are no fuel costs, and as a result no future pressure on resources that occurs with gas and oil; and that these technologies have a limited effect on the environment.

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