KaXu Solar One, Pofadder, Northern Cape

KaXu Solar One is the first concentrated solar power (CSP) plant in South Africa to use the parabolic trough technology. Image: courtesy of Industrial Development Corporation (IDC).

KaXu Solar One is owned and operated by Abengoa Solar (51%), Industrial Development Corporation (IDC, 29%) and the KaXu Community Trust (20%). Image: courtesy of Industrial Development Corporation (IDC).

South Africa's biggest solar thermal plant was commissioned in March 2015. Image: courtesy of Industrial Development Corporation (IDC).

KaXu (translated as open skies) Solar One, the biggest of its kind in Africa and the southern hemisphere, is located approximately 40km north-east of the town of Pofadder in the Northern Cape Province, South Africa.

The 100MW concentrated solar power (CSP) plant is the first to use the parabolic trough technology in South Africa. It came online in March 2015 following more than two years of construction, which was initiated in November 2012.

The plant has an output capacity of 320 gigawatt hours a year (GWh/year), which is sufficient to serve 80,000 African homes and offset 315,000t of CO2 emissions a year. The project also generated 4,500 construction jobs and 80 permanent jobs, and helps South Africa to meet its target of generating up to 17,800MW of renewable energy by 2030.

The South African solar power plant is owned and operated by Abengoa Solar (51%), state-owned Industrial Development Corporation (IDC, 29%) and the KaXu Community Trust (20%).

KaXu Solar One location and plant make-up

The KaXu Solar One project facilities have a footprint of approximately 310ha (3.1km²) on a 1,100ha (11km²) site. It is equipped with 1,200 parabolic trough solar collector assemblies (SCA), each measuring 25ft-wide, 500ft-long and 10ft-high. Each SCA comprises ten modules, which further integrate 28 pivoting concave mirrors each, bringing the total number of parabolic-shaped mirrors at the site to 336,000.

The SCAs focus the sunlight on to 4m-long receiver pipes or heat collection elements (HCEs) placed at the centre of each trough, to heat the thermal fluid flowing through the pipes. The thermal energy is converted into steam that drives a steam turbine to generate electricity.

KaXu Solar One further integrates a two-tank, indirect molten salt-based thermal energy storage system, which provides up to 2.5 hours of stored energy to be used after sunset or when cloudy. The solar thermal field is expected to be in service until 2035.

Kaxu Solar One power purchase agreement

The entire output from the solar power plant is purchased by Eskom, Africa’s biggest power utility, under a 20-year power purchase agreement.

The solar plant conveys the electricity to Eskom’s Paulputs Transmission Substation in Northern Cape via a 5km-long, 132kV overhead transmission line.

Financiers involved with KaXu Solar One

The power plant was constructed with an estimated investment of $891m. The European Investment Bank (EIB) provided R1.4bn ($104m approximately) funding for the project. The European Investment Bank provided a €210m ($236m approximately) loan along with First Rand Bank and the Development Bank of Southern Africa.

Abengoa provided R1bn ($74m approximately), while other financiers included IDC, Nedbank RMB, and the International Finance Corporation. Mott MacDonald served as the lenders’ technical adviser.

Contractors involved with Africa’s biggest solar power plant

The engineering, procurement and construction (EPC) contractor for the project was Abeinsa EPC. Siemens provided installation and commissioning support for the project.

The final environmental impact assessment (EIA) report for the project was prepared by Savannah Environmental. The drawings and documentation works for the civil engineering structures were provided by 3D3 INGENIERÍA.

The parabolic trough SCAs were supplied by Abengoa, while Rioglass supplied the mirrors, Schott supplied the HCEs and Goizea supplied the pipe supports.

ALTAC was the structural designer for the project. Bergvik supplied its proprietary Iso Floor System for the electrical control rooms of the solar field.

Inspection and quality control services were rendered by OCA International, while Jeffares & Green (J&G) served as Abeinsa’s design review consultants for the mirror assembly warehouse and Element Consulting Engineers scrutinised the design layouts provided by the EPC contractor.

The electrical and control instrumentation works were provided by Lead EPC, Flowserve supplied 307 of its Limitorque MX10 actuators, and Power Electronics supplied seven units of its XMV660 variable-speed drives and three units of its SD700 low-voltage (LV) speed drives for the solar field.