South Africa turning greener

South Africa’s energetic renewables programme

The wind revolution

The Darling Wind Farm is intended to be a learning platform for the development of the wind energy industry in the country, by providing a financial, contractual, technical and operational framework for further independent power producer projects. Further, the project is in line with the government’s vision in respect of climate change and pollution mitigation, efforts to create a new industry and help the local population to benefit economically.

Setting the wind trend

Construction on the Darling wind project started in September 2007 with the first wind-generated energy produced in May 2008. In April this year, the last turbine of 12 in phase 1 was installed. The four turbines put in place in the first year of the project produced 8.6 gigawatt hours (at 1.3 MW each) or the equivalent of the yearly consumption of some 700 average South African households. The turbines rise 50 metres above the ground (equivalent to a 17-storey building), where the three rotor blades and the nacelle, housing the generator and the gearbox, are located. Their combined weight is 62 tons.

The turbines start producing power at a wind speed of 8 km/h, reaching full potential at 54 km/h. The blades rotate slowly at a constant speed of 32 revolutions per minute regardless of the wind speed. The length of the blades is 32 metres, just slightly more than the length of a tennis court.

A computer monitors the turbines’ condition permanently with over 100 sensors, ranging from wind speed and direction, turbine orientation, temperature, vibrations, the electricity produced etc., in order to optimise the production and efficiency at any time. Should wind speeds exceed 97km/h, the control system will close the system down and initiate braking to stop the blades. Wireless technology allows operation of the wind farm to be remotely controlled from anywhere over the internet, allowing for the monitoring of possible alarms, support from the German manufacturer and swift response action 24 hours a day.

The total project investment is some R75m ($9m) with a life expectancy of 20-plus years. The main costs relate to the operation and maintenance of the equipment and the general upkeep of the site.

The City of Cape Town has signed a power purchase agreement granting them the entire production for 20 years at a negotiated tariff. It will use half for its own needs and sell the remaining power to individuals and companies supporting green electricity generation.

Concentrated solar power

A relative newcomer in the range of energy generation, concentrated solar power is by far the more exciting. It holds the promise of energy storage, a facility that has so far eluded researchers, and could reach base capability before any of its renewable competitors.

A joint venture between Spanish CSP pioneer Abengoa and South Africa’s Industrial Development Corporation, the partners are keen to concertina the three-year building span into two and be ready for commissioning towards the end of 2014. The project comprises a 100 MW parabolic system and 50 MW tower technology being installed in the scorching solar radiance of South Africa’s Northern Cape province on the edge of the Kalahari Desert.