Redstone CSP Plant Marks Likely End of an Era for Solar Thermal in South Africa

(3 Minutes Read)

The 100 MW Redstone Concentrated Solar Power (CSP) plant has reached full commercial operation in South Africa, but it may be the last of its kind due to high costs, long delays, and more efficient alternatives like photovoltaic (PV) solar with lithium-ion storage.

Once praised for its ability to store energy for use after sundown, CSP has lost favour. Redstone’s thermal battery can deliver 12 hours of backup power, but the technology is complex, expensive, and dependent on co-located storage in areas with ideal sunshine — regions in South Africa that are now constrained by limited transmission capacity.

Energy analyst Chris Yelland noted the project’s completion, despite delays and the bankruptcy of its original technology provider, is an anomaly. Redstone’s final price of R1.223/kWh under a 20-year deal is no longer competitive compared to newer PV-battery projects.

Meanwhile, PV systems are simpler, cheaper, and faster to deploy. Falling costs for solar panels and lithium-ion batteries make combined PV-storage solutions more attractive and flexible, even in grid-constrained areas. As a result, CSP is unlikely to feature in South Africa’s future energy plans.

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CSPs use heat energy from the sun to warm a thermal battery, typically consisting of molten salt. Using a heat transfer, the plant boils water to create steam, which turns a turbine to produce electricity.

The Redstone plant has a 1,200MWh thermal battery capable of supporting up to 12 hours of 100MW backup power even when the sun is not shining.It is the sixth CSP to be built in South Africa under the government’s Renewable Energy Independent Power Producers Programme (REIPPP).