International technology and infrastructure group Abengoa, which has developed a portfolio of three concentrated solar power (CSP) projects in South Africa, believes blending CSP with solar photovoltaic (PV) technology is the logical next step for lowering CSP costs, while also producing dispatchable solar power.
The Spanish group recently completed construction of the 100 MW XiNa Solar One parabolic-trough CSP power station in the Northern Cape town of Pofadder, following a 29-month construction period.
XiNa, which means ‘bright light’ in the Khoisan language of Nama-Damara, is located close to Abengoa’s 100 MW Kaxu Solar One parabolic-trough power station, which has been operating since 2015. The group’s 50 MW Khi Solar One solar-tower plant, which is located near Upington, began producing in 2016.
Abengoa South Africa business development VP Dominic Goncalves tells Engineering News Online that the group remains optimistic about the future of CSP, despite criticism of the technology’s costs and recent delays to South Africa’s renewable-energy procurement programme.
He says substantial progress has been made over the past four years in the scale and efficiency of CSP projects being developed in the Middle East, Africa, China and the Americas, which has already helped reduced operating costs.
However, building hybrid plants, which incorporate both solar technologies, could assist in reducing costs even further. Such an approach is already being pursued in Morocco, where low-cost PV plants will be used during the day, while the solar-thermal power produced using CSP is stored in tanks for release to the steam generators at night, or when there is insufficient solar radiation for PV generation during the day.
All three of Abengoa’s South African plants already include storage capacity, with the R9.5-billion XiNa incorporating five-and-a-half hours of storage, enabling the plant to supply into the grid during the evening peak from 16:30 to 21:30. Storage at Kaxu and XiNa is based on molten salts, while Khi employs super-heated steam.
In fact, XiNa’s power purchase agreement (PPA) with Eskom includes an incentive for peak-time production. For the period from April 2018 to March 2019, the standard-time tariff is set at R2 151.28/MWh, while the peak-time tariff is R5 808.47/MWh.
“Technically it’s now feasible to have solar thermal technology like XiNa being dispatchable almost 24 hours a day, although this will require an oversized configuration of the storage technology at an increased cost.”
Should South Africa decided to procure further CSP capacity, Goncalves believes production costs could be reduced by about 30% by merging of the two main solar technologies of CSP and PV.
However, the future of South Africa’s energy mix will depend primarily on the outcome of a review of the country’s Integrated Resource Plan (IRP) for electricity, which Energy Minister Jeff Radebe has confirmed is currently under way.
“The Department of Energy is at an advanced stage of finalising the review of IRP, which will provide further policy certainty on electricity generation infrastructure for the next 20 to 30 years,” Radebe said at the recent Japan-Africa Public Private Economic Forum, which took place in Johannesburg.
Despite a recent protracted delay in South Africa’s roll-out of renewable energy, Goncalves confirms that Abengoa is “more than willing” to participate in new projects, adding that the group has been encouraged by the recent revival of the Renewable Energy Independent Power Producer Procurement Programme and the signing of PPAs for 27 delayed projects.
However, for renewable-energy projects and technologies to be deployed in a way that reduces cost and risk, “it is fundamentally necessary to have predictable, robust programmes”.
Such an environment is not only necessary for attracting renewable-energy investment, but also the other possible public-private investment areas in which Abengoa is keen to participate, such as the proposed gas-to-power programme and possible desalination projects.
Globally, Abengoa’s seawater reverse osmosis plants are treating 1 500-million litres a day, which Goncalves says is around three times Cape Town’s water consumption.
“In fact, just this year we have been awarded two large desalination projects in the Middle East and Morocco that would cover more than the whole of Cape Town’s water consumption.”