08/07/2025
South Africa gets R11.6-billion solar plant with biggest thermal battery
The Redstone Concentrated Solar Plant (CSP) near Postmasburg in the Northern Cape recently reached full commercial operation, adding 100MW of generating capacity and 1,200MWh energy storage to South Africa’s grid.
The development comes after Redstone was synchronised to the network for the first time in September 2024.
Developed by ACWA Power, the plant is one of South Africa’s most expensive renewable energy projects to date, costing R11.6 billion.
Unlike photovoltaic (PV) solar plants that convert the sun’s light energy into electricity, CSPs use heat energy to boil water and produce power.
While they are substantially more expensive to build, CSPs feature a built-in thermal battery — typically in the form of a massive molten salt container — so they can supply power when sunshine is unavailable.
In the case of Redstone, 40,000 mirrors known as heliostats are arranged in a concentric circle around a 248-meter tower, directing the sun’s energy to a receiver that heats the molten salt.
The hot salt converts water into steam and, like in many other types of power stations, turns a turbine to generate electricity.
In addition to a peak capacity of 100MW, the Redstone CSP features 1,200MWh of thermal battery capacity using technology from California-based SolarReserve, its original developer.
The substantial storage means it can support the plant’s maximum output for up to 12 hours without sunshine.
South Africa already had five CSPs before Redstone came online. However, those have significantly less backup power capacity and cannot supply their peak design power throughout the night.
Its storage capacity also surpasses the Kenhardt hybrid facility, which boasts 1,140MWh of lithium-ion batteries. However, its design output of 100MW is substantially lower than Kenhardt’s 225MW.
ACWA Power country manager for South Africa, Nandu Bhula, said the plant is expected to contribute around 500,000MWh of electricity annually, sufficient to serve the demand of more than 200,000 homes.
It is also the first renewable power plant to provide ancillary services to the National Transmission Company of South Africa, at no additional cost.
Delayed by dodgy decisions.
The Redstone plant has been in the works for over a decade, but it has experienced substantial delays due to shoddy Eskom and government decisions that have created significant uncertainty.
It was one of 27 projects awarded preferential bidder status in Bid Windows 3.5 and 4 of South Africa’s renewable energy procurement programme in 2015, which were only signed off in early 2018.
The delay was caused by Eskom, which said it would no longer buy energy from renewable producers in 2016, as it had a generation surplus. That would come back to haunt the utility from around 2019.
The Department of Energy also contributed to delaying the process, including by holding back on signing the power purchase agreements (PPAs) due to labour union objections.
The National Union of Metalworkers attempted to interdict the projects based on their impact on jobs in the coal sector.
The case was ultimately dismissed and struck off the roll with costs, allowing the government to proceed with the procurements.
Construction on the Redstone plant commenced in early 2021, after funding was secured from several investors, including the African Development Bank, Absa, Nedbank, Investec, and Sanlam.
International investors included the Nederlandse Financierings-Maatschappij voor Ontwikkelingslanden and Deutsche Investitions und Entwicklungsgesellschaft.
The plant was initially anticipated to commence commercial operations in the fourth quarter of 2023, with 100% of design capacity to be reached within a year of that date.
At the peak of construction, the project created 2,000 jobs, which included 400 people from the local community. During its operational life, it will support 100 permanent jobs.
PUBLISHED in MyBroadband 08/07/2025.
https://mybroadband.co.za/news/energy/601565-south-africa-gets-r11-6-billion-solar-plant-with-biggest-thermal-battery.html
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