Redstone concentrated solar thermal power (CSP) project is a 100MW integrated CSP plant being developed in South Africa.

The South Africa Department of Energy (DOE) awarded the contract to develop the CSP project to the consortium of SolarReserve and ACWA Power, in January 2015. The contract was awarded under the Renewable Energy Independent Power Producer Procurement Program (REIPPPP) initiated by the DOE.

Redstone is the first of its kind to be developed in Africa and is expected to produce 480,000MW of clean energy a year. It is expected to electrify approximately 210,000 South African households during peak demand and is also anticipated to create more than 3,500 jobs.

The CSP project is estimated to involve an investment of $789m and is expected to have an operational life of more than 30 years.

Redstone concentrated solar project location

The Redstone concentrated solar power plant is being developed in the Humansrus Solar Park located towards the east of Postmasburg, Northern Cape Province.

It is located in close proximity to the 96MW Jasper and the 75MW Lesedi photovoltaic (PV) solar power projects developed by SolarReserve under the REIPPPP. The three projects together become the first combined CSP and PV solar park in the world, with a total generating capacity of 271MW.

Redstone concentrated solar project details

The project will feature ThermaVault technology developed by SolarReserve, which will combine the solar thermal technology with molten salt energy storage technology. The project design is similar to that of SolarReserve’s Crescent Dunes project.

The CSP technology will be capable of storing thermal energy for a period of 12 hours, which enables the plant to generate electricity through the night in addition to day time operations.

The heliostats of the project follow the sun and reflect the sunlight onto a 250m-tall central receiver tower, which uses molten salt as heat transfer fluid and storage medium.

The thermal to electric power conversion unit will comprise 115MW high-temperature subcritical steam turbine-generator units.

Auxiliary infrastructure includes two molten salt storage tanks, air-cooled condensers, water purification system, sewage treatment facility, an evaporation pond, emergency diesel generators, electrical switchyard, step-up transformers, and associated facilities.

The project also features dry cooling of the power generation cycle, to minimize water usage during operations.

Off-take and transmission of power from Redstone

Eskom entered a 20-year power purchase agreement with the consortium of SolarReserve and ACWA Power, in April 2018, for the off-take of power generated at the Redstone solar thermal power plant.

A new 132kV switching station and a 34km-long 132kV transmission line are proposed to be constructed to connect the project with the national grid.


African Development Bank (AfDB) approved a ZAR3bn ($192.4m) senior loan for the Redstone CSP project, in November 2018.

ACWA Power and Central Energy Fund of South Africa entered a co-operation agreement, in July 2018, for co-investing in the Redstone project.

In October 2015, Overseas Private Investment (OPIC) signed an agreement with the project developers and made a commitment to provide $400m debt financing for the CSP project.

IFC financed $72m loan and $50m CTF soft loan for the project development as well as acted as the mandated lead technical bank/co-ordinating bank.


Apart from SolarReserve and ACWA Power, other prominent investors of the project include Public Investment Commission (PIC, 13.5%), Old Mutual Life Assurance South Africa (OMLACSA, 10%), Community (12.5%), and Pele Green (4%).

Contractors involved

SolarReserve is the supplier of the core technology for the project, including the molten salt receiver, heliostat collector field controls, and tracking system.

WorleyParsons was involved in the environmental management program (EMPr) for the Redstone Solar Thermal power plant, in 2015, while Savannah Environmental was engaged for reviewing the EMPr.

Acciona Industrial was awarded the engineering, procurement, construction, and commissioning contract for the power project.

First National Operation and Maintenance (NOMAC), a wholly-owned subsidiary of ACWA, is responsible for the operation and maintenance (O&M) of the Redstone concentrated solar thermal power project.