State-owned power utility Eskom’s 100-MW wind farm, which will be located close to the town of Koekenaap, just north of the Olifants river, is expected to be operational in 2010, despite recruitment problems and long lead times threatening to delay the project.

“Request for tenders for the engineering, procurement and construction contract closed in May last year, with the technical and commercial evaluation completed in June last year; however, with the current world economic recession, this might have to be relooked at,” says Eskom renewables manager Terence Govender.

“Wind farms are land intensive. The 100-MW plant will require 20 km2 of landspace,” notes Govender.

Other developments include the acceptance of the specification for the access road repair from the R363, at Koekenaap, to the site, in principle by the West Coast regional office of the Department of Transport and Public Works. “We are also continuing to monitor five to six hot spots that we have identified,” adds Govender.

The project will involve the development of a wind farm with an initial capacity of 100 MW, which is likely to be increased to 200 MW. 
The plant will allow for the storage of renewable energy for use during the evening peak demand.

It will consist of some 50 horizontal wind turbines with pitch control, gearbox reduction drives and induction generators ranging in capacity from 1,5 MW to 
2,5 MW each.

The wind farm will be connected to the national grid through a 132-kV line to Eskom’s Koekenaap or Juno substation close to Vredendal. “We expect that the wind power plant will have 2-MW to 3-MW turbine sizes, with a load factor of 22% to 28% and a life-of-plant of about 20 years, with an estimated annual production of 228 GW/h,” says Govender.

The 100-MW wind farm will be South Africa’s second commercial wind farm, following the launch of the first wind farm near Darling, in the Western Cape, in May 2008. It is the result of cumulative research at Eskom’s Klipheuwel wind energy demonstration facility, which was built in 2002 as a demonstration wind energy facility.

The Klipheuwel project, which is fully established and being run by Eskom’s peaking division focused on understanding the implications of using wind energy on a large scale for bulk electricity generation, determining the most suitable applications for wind energy as well as the most appropriate scale of implementation.

Twenty potential sites were originally identified; however, the Klipheuwel site was selected because of its acceptable wind speeds, its proximity to Cape Town for research and demonstration purposes, and the existing electricity distribution infrastructure.

The site consists of three turbines of different mechanical and electrical design that were commissioned between August 2002 and February 2003. 
The Jeumont 750-kW Still Control Turbine, with permanent magnet gearboxless synchronous generator and inverter connection to the national electricity grid, the Vestas 660-kW pitch control directly connected asynchronous generator turbine, and the Vestas 1,75-MW 
pitch control asynchronous generator turbine with rotor conversion system.

The Klipheuwel wind farm has a total capacity of 3,16 MW and a load factor of 20% to 30%. It has generated more than 
15 GWh to date.
 The wind generators have an expected lifespan of about 20 years, with turbines that can withstand wind speeds of between 200 km/h and 250 km/h.

Although the most advanced of all the renewable-energy projects, Govender notes that wind energy as a renewable source of energy has several challenges. These include the high construction costs, which are site specific, and, as an intermittent source, the production cost for wind energy for each kWh is higher than the cost of electricity currently produced by Eskom’s coal-fired power stations. 
The turbine’s units are small in capacity, ranging from 25 kW to 2 000 kW, which means hundreds of wind turbines would be needed to replace a single coal thermal unit ranging between 200 MW to 600 MW. Wind resource is also unpredictable and the wind turbines only work at certain speeds.

“Despite these drawbacks, wind is a free sustainable resource that provides a clean form of energy that gives off no emissions or waste products,” concludes Govender.

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