It is quite safe to say – without upsetting too many people – that the Northern Cape does not have very much to boast about. It’s a place of vast open spaces and blistering sunshine that mainly appeals to hardy souls and adventurers. Yet those characteristics have now turned into its biggest industrial attraction, because open spaces and sunshine are exactly what a solar power plant needs.
The Khi Solar One power plant is currently being constructed near Upington, and will give South Africa a much needed source of alternative electricity. And as Eskom imposes rolling blackouts once again, it’s good to know that there is solar powered light at the end of the tunnel.
Khi Solar One is commonly referred to as a CSP, a Concentrated Solar Power plant. It is being built by Spanish company Abengoa Solar in partnership with South Africa’s Industrial Development Corporation and the Khi Community Trust.
The site is a barren landscape about 40 km from Upington, where the plant will draw its energy from 4,200 heliostats arranged in an array spanning 576,800 m2. A heliostat is a computer-controlled mirror that tracks the sun to keep it reflected on a target as it moves across the sky. Abengoa is using a new design of heliostat with higher reflective areas. The mirrored surfaces will reflect the sun’s rays onto a boiler placed on top of a steam tower 205 m tall, which is almost as tall as Johannesburg’s Carlton Centre.
The tower is filled with tubes painted black to absorb heat from the reflections, and containing high-pressure water pumped from the Orange River. When the sun is reflected onto the tubes, the water reaches boiling point and turns into steam, and that steam is heated further to create enough pressure to turn a turbine and generate electricity. Abengoa has signed an agreement with Eskom to buy all the electricity it produces.
Khi Solar One will be the first solar power plant in Africa, and Abengoa’s first outside of Spain. Its design has been influenced by lessons learned at other plants. One innovation is scrapping the usual method of using molten salt as a fluid to transfer and store the heat. Instead it will use superheated steam to reach a maximum temperature of 530 ºC, increasing the efficiency by up to 30 % in a technology developed by Abengoa’s research team.
Saturated steam will also be used to store the thermal heat for up to two hours, so energy can still be distributed after sunset or in cloudy weather.
Despite relying on steam, the plant will not require vast amounts of water or much electricity to operate, thanks to an innovative dry cooling system installed by SPX Corporation. Instead of using electrical fans to blow cold air to cool its condensers, the dry cooling system uses natural drafts in the towers to distribute air across fin blades and thus dissipate the heat.
“As this type of cooling tower operates without fans, the substantial amount of electric power otherwise required for large cooling tower systems is not needed,” says SPX. This technology should also use 80 % less water than a wet-cooled CSP plant.
Abengoa says that these are important technological advances that will allow higher temperatures during the electricity generation process, more than doubling the capacity of the last tower it built in Spain.
Hundreds of construction jobs were created during the lengthy building process, and around 35 fulltime plant operators will be employed once the plant is switched on. Tragically, two people died and seven were injured in November when a crane collapsed at the plant during gale force winds, another natural phenomenon that makes the Northern Cape quite hostile.
Although a start date has yet to be confirmed, the plant will soon begin to contribute to South Africa’s goal of generating up to 17,800 MW of renewable energy by 2030 and reducing our dependency on the unsustainable resources of oil and natural gas.Abengoa was awarded the project by the Department of Energy in an announcement made at the United Nations COP17 Climate Change Conference in Durban in 2011.
South Africa’s sunshine makes the country ideal for harvesting solar energy, as the power it provides is clean, dispatchable, renewable, and can be stored for later use.
Sidebar - Solar Statistics
- The 205 m tall Khi Solar One tower will generate 50MW of power to provide clean and sustainable electricity to approximately 65,000 homes.
- Its technologies include super-heated steam and dry cooling methods that increase efficiency and reduce water consumption compared to previous solar plants.
- The project is a partnership, with Abengoa holding 51 %, the Industrial Development Corporation 29 % and black economic empowerment stakeholders the Khi Community Trust holding 20 % of the ownership.
- Solar One will benefit the country through R4 billion direct and indirect investment, and by creating a supply chain for R2.6 billion in components and services, with 45 % local content.
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