South African construction company Concor has put its stamp of experience and quality on another renewable energy project – this time the Roggeveld Wind Farm in the Karoo, 40 km north of Matjiesfontein.
This project won the Civil Engineering category in Construction World’s Best Projects 2020. It also received a Highly Commended Award in the AfriSam Innovation in Sustainable Construction category.
The 47-turbine, 147MW project has been developed by Red Rocket under government’s REIPPPP initiative, and constructed by EPC contractor Nordex Energy South Africa. Concor successfully completed the civil balance of plant work, including turbine bases spread over a construction footprint of 40 hectares.
Among the challenges was the area’s topography, with the highest point at 1 485 metres above sea level and the site offices a full 200 metres lower. Greg Oosthuizen, Concor’s project manager, notes that the wind farm is also in an environmentally sensitive area, with strict compliance standards applied to all construction activities.
Accessing the sites for the wind turbine bases and hard stands was over difficult terrain, and required the construction of 34 km of access roadway. The blasting, excavation and cleaning of each site was followed with the pouring of blinding and installation of levelling legs. About 2000 tonnes of steel reinforcing was used.
Then came the final installation of the levelling template, with corrugated sleeves in the foundation for anchoring the concrete towers, which are grouted into the foundation once assembled. Shuttering could then be installed, preparing the base for the readymix pour. Some 25,000 m3 of readymix was used, supplied from Concor’s own on-site batch plant.
Oosthuizen points out, however, that the batch plant presented logistical challenges of its own. It was some distance from the actual wind farm project, and about 12 km from the nearest turbine base.
“We operated ten readymix trucks on the project, and carefully managed efficiencies at the batch plant to reduce the turnaround time of these vehicles,” he says. “We also had to adjust the pumping rate when pouring the readymix at the bases.”
He emphasises that there was little room for error in base construction, especially regarding the tolerances for the levelling template. While different teams were working simultaneously on the base construction, it was viewed as one activity.
“We found that open communication between the teams was critical, and we relied on the Daily Safe Task Instructions to ensure that everyone was aligned with what was required,” he says.
Roggeveld Wind Farm will contribute 5,55000 MWh a year of clean energy to the national grid, and its location in a wind channel with high wind speeds will make it one of the most energy efficient of South Africa’s wind farms built to date. With hub heights of 100 metres and rotor diameters of 130 metres, 40 of the wind turbines are 3,15MW capacity while seven are 3MW.