In South Africa, the Loeriesfontein Wind Farm, which falls under the department of Energy’s Renewable Energy Independent Power Producer Procurement Programme (REIPPPP), is said to have one of the world’s lowest carbon footprints for any wind farm foundation.
This is according to research scientist and head of Murray & Roberts’ Concrete Centre for Excellence, Cyril Attwell, who said that the wind farm’s foundations have been developed with an 89% replacement of cement.
According to a statement released by the wind farm, the farm’s first two bases comprise of an 80% replacement of Portland cement, and the balance utilises a unique design comprising 35kgs of high grade Portland cement per cubic meter, an 89% reduction from a standard concrete mix.
This mix has enabled the farm’s carbon footprint being reduced to around 90.7kg of carbon dioxide per cubic meter. Ground Granulated Corex Slag (GGCS), a by-product from the iron industry, is used to replace 89% of the cement.
Leo Quinn, Project Manager for Loeriesfontein Wind Farm said: “Cement manufacturing is typically a highly energy intensive process. By substituting the cement with a by-product such as GGCS, we are able to reduce our carbon footprint considerably.”
Attwell explained: “A twenty-eight day compressive strength test has been completed, which indicated that the 80% replacement ratio achieved an impressive strength of 55MPa (megapascals), and an expected ultimate strength of 100MPa, within a fifty-six day period.
“The strength of concrete is measured in megapascals; theoretically a cubic metre of concrete that is rated 30 MPa, is able to withstand the weight of six bull elephants, whereas these foundations are able to withstand the approximate mass of 20 bull elephants standing on a square centimetre of concrete – a phenomenal feat.”
A smaller carbon footprint
Quinn explained: “The achieved reduction in our carbon footprint is phenomenal, especially considering that a standard 30MPa concrete as supplied by the ready-mix industry equates to a carbon footprint of approximately 300kgs to 350kgs of CO2 per cubic meter.”
The wind farm added in a statement that usually a 30 MPa concrete needs between 300kg and 350kg of ordinary cement per cubic metre, but scientists working for Murray & Roberts have developed a technology that meets the 30 MPa standard using just 25kg of cement or even less.
The Loeriesfontein Wind Farm
The wind farm, which falls under the jurisdiction of the Hantam Municipality in the Northern Cape, will comprise of 61 wind turbines each with an output of 140MW. The farm will generate an estimated 563,500 MWh per annum of clean energy to the national electricity grid.
In addition, the wind farm will reduce its emissions by an estimated 550,000 tonnes each year and generate enough to power around 120,000 domestic households.
The location of the Loeriesfontein Wind Farm was selected for its optimal wind resources, favourable construction conditions and direct connection into Eskom’s Helios substation. The project is expected to come online by December 2017.