Energy20.01.2025

Groundbreaking all-hours solar power farm launching in South Africa

South Africa will soon get a concentrated solar power (CSP) plant with a first-of-its-kind hydrothermal battery that will supply significant power overnight.

CSP plants generate electricity with heat energy from the sun rather than light energy like photovoltaïc (PV) plants.

One major advantage over PV facilities is that they are paired with an energy storage system that can supply electricity when the sun is not shining.

While there are several configurations of CSPs, all operate by using mirrors that concentrate the sun’s beams onto a receiver. The mirror modules are typically arranged in a circle or semi-circle around a tower that holds the receiver.

The receivers on some of these plants can reach temperatures around 600°C.

CSPs are truly eye-catching in real life, with the receiver’s blinding glint sometimes described as otherworldly.

South Africa already has five CSPs — each with a peak output of 100 megawatts (MW). However, all of these use molten salt for energy storage.

The new CSP plant being built by Photon Energy will use cutting-edge hydrothermal technology from Australian firm RayGen.

The plant will be located in Winterton, KwaZulu-Natal, and will have a peak production of 250MW when the sun is out.

Its hydro storage will ensure it can supply 150MW output over 12 hours when the sun is not shining.

If all of this is used, it will have supplied 1.8 gigawatt-hours of electricity over that period, equal to 1.8 million kilowatt-hours.

In addition to heat energy, the plant will also collect light energy on the central receivers, which are also PV modules.

One third of the sunshine is converted into electricity and the other two-thirds are used to heat water at 90°C.

RayGen’s technology demonstration plant has two deep pits — one filled with cold water and another with hot water — both of which are insulated to prevent temperature changes or evaporation.

The heat generated as a byproduct from the receiver is used to warm the water in the hot pit, while the electricity from the receiver runs a chiller to cool the water in the other.

When energy must be dispensed from the plant’s storage, the temperature difference between the two pits’ water drives an organic Rankine cycle turbine.

The turbine’s working fluid — ammonia — is evaporated by the hot water to turn the turbine and generate electricity.

The image below shows the basic components of RayGen’s solar-hydro power plant.

RayGen’s technology is already in use at the Carwarp plants in Victoria, Australia. This plant only has 4MW capacity and 50MWh storage. Therefore, the Winterton farm will likely have a much greater scale.

Construction planned for next year

Photon Energy recently announced the Winterton CSP project was making steady progress, with the most recent milestone being that it received favourable grid connection terms.

“In the next phase of development, Photon Energy will collaborate with Eskom to design and implement the necessary technical solutions for integrating the plant into both the regional and national grid,” the company said.

“This partnership aims to ensure grid stability, optimize energy distribution, and provide essential services such as frequency regulation and peak load management.”

The project is expected to conclude its Environmental Impact Assessment (EIA) in the fourth quarter of 2025 and reach ready-to-build status by the second quarter of 2026.

RayGen’s technology is already in use at two plants in Australia — the Newbridge and Carwarp plants in Victoria.

The latter demonstrates the CSP technology that is envisioned for application on the Winterton farm.

However, considering that the Carwarp plant only has 4MW capacity and 50MWh storage, the Winterton farm will likely be much larger.

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