Molten salt energy storage used in S Africa CSP project

8th April 2016

Molten salt energy storage used in S Africa CSP project

CSP PROJECT LAUNCHED Projects uses heat exchanger as a diffusion medium for the energy stored inside the molten salt

The Bokpoort concentrated solar power (CSP) project – launched March 14 – in the Northern Cape, is one of the few CSP projects that use heat exchangers as a diffusion medium for the energy stored inside the molten salt.

The R5-billion project has one of the highest solar radiation footprints in the world and is being developed as part of South Africa’s Renewable Energy Independent Power Producer
Procurement Programme.

The 50 MW CSP plant incor-porates 1 300 MWh molten salt energy storage facility, which will provide about 9.3 hours of thermal energy storage. The site covers an area of about 6 700 ha, of which its facilities cover a total area of about 250 ha.

The CSP plant employs engineering and technology group Sener’s patented technology SENERtrough cylindrical-parabolic collectors, which direct the solar radiation to a central absorber tube containing a heat transfer fluid (HTF) such as thermal oil.

The heated oil is pumped to the heat exchangers, which transfer the thermal energy to heat water. The generated steam is then used to drive a SST-800 Siemens steam turbine generators to produce electricity.

A stream of the same HTF is also used to heat a molten salt mixture stored in two large insulated tanks, which retain the heat and release it during the night or during cloudy days. Following the transfer of the heat, the HTF is further cooled and recirculated through the receivers to repeat the process.

The project will also involve the installation of a backup diesel-fired boiler to enable the direct heating of HTF to prevent the crystallisation of the molten salt during cold nights.

The required water for the project will be sourced from the Orange river through a dedicated water transmission pipeline.

Furthermore, the renewable-energy facility will have an output capacity of 200 GWh/y, which is sufficient to serve about 21 000 households and offset 230 000 t/y of carbon emissions.

Other significant benefits from the CSP project include the generation of about 900 jobs during the peak construction phase, 60 jobs during the operations and maintenance (O&M) phase, and about $2-million in additional investments each year.

Meanwhile, Trade Ministers from South Africa and Saudi Arabia jointly inaugurated the Bokpoort CSP project, which has been developed by research and investment company ACWA Power.

O&M provider Nomac, a subsidiary of ACWA Power, and Invest In Africa Energy Services will be responsible for providing operations and maintenance services for the facility.

ACWA Power notes that the project will contribute significantly to the government initiative to augment much-needed power capacity, attract foreign direct investment and create jobs, while also stimulating the country’s economy.

ACWA Power Southern A frica region MD Chris Ehlers says: “We are here to serve the nation and to contribute to its development. “Our commitment to the development of the South African economy beyond reliably supplying renewable energy at a cost-competitive tariff is demonstrated by the R2-billion worth of locally sourced components made in South Africa that have been used in the construction of this plant and the creation of 1 300 construction jobs.”

Moreover, the Bokpoort CSP plant is the first in a series of investments in the power sector that ACWA Power is making in South Africa. The company is expecting to commence construction on the 100 MW Redstone CSP project, in Northern Cape. This is scheduled to commence in 2018.

ACWA Power is awaiting the outcome of tender submissions for a 300 MW coal-fired plant in Mpumalanga and another 150 MW CSP plant, in the Northern Cape.

ACWA Power pursues a mission to reliably deliver electricity and desalinated water at the lowest possible cost, while seeking to maximise local content and local employment creation, thereby contributing to the social and economic development of the communities and countries it invests in and serves.