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Concentrated solar power plant

24 hour solar power?

It’s exactly when conventional solar generation tails off that power demand peaks: sunset. A new solar technology set out to change that, holding the promise of affordable low carbon electricity, night and day. By asking the right questions, Mott MacDonald Africa’s energy team – while part of the Mott MacDonald Group - helped turn an innovative project into a mainstream opportunity.

Solar energy consultancy and lenders' technical advisory


Concentrated solar power (CSP) plants use mirrors to focus the sun’s energy. On the KaXu and Xina projects, giant parabolic mirrors were used to heat fluid-filled tubes. This solar-heated fluid is passed through heat exchangers where it generates steam, which in turn drives a turbine to generate power.

The client wanted to transform CSP into after-dark generation technology by adding a heat storage ‘battery’. To store energy, the transfer fluid is used to heat a reservoir of molten salt to 385°C. After sunset, the salt gives up its thermal energy to keep power production going.

The system offers the potential to increase demand for solar generation, creating commercial opportunity while reducing the country’s carbon footprint. But the project’s lenders wanted help to assess the risks around reliability, robustness and cost.


Asking the right questions was key to pinning down the technical and commercial intricacies of this power production system. It called for diverse expertise and detailed insight into CSP that we provided in-house, giving the lenders and the project sponsor alike joined up advice and the confidence to go ahead.


Finance for the first parabolic trough CSP project in South Africa, KaXu, was secured, paving the way for a second, more advanced scheme, Xina. Together, these will provide green electricity for 175,000 households even after the sunset. The experience gained on KaXu and Xina is instilling confidence in the development of follow-on schemes, not just in South Africa but anywhere with abundant sunshine, and paving the way for use of more efficient technology on future CSP projects.

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