The integration of concentrated solar thermal power facilities alongside coal plants that have remaining operating lives of 25 years, or more, is technically feasible and could materially lower the subsidy required for the inclusion of concentrating solar power into the domestic generation mix.
However, he stresses that hybridisation should be seen as complementary to standalone concentrated solar thermal power solutions, which could have a significant role to play in South Africa’s future energy mix, owing to the country’s exceptional solar resource.
The Department of Energy’s current bidding process for the first 3,725 MW of renewable energy capacity sets a price cap of 285c/kWh for standalone concentrated solar thermal power projects, which is well above the prevailing Eskom tariff of around 66c/kWh.
However, Bögli says the allocation of only 200 MW for CSP is too small to provide the scale required to materially reduce the levelised energy costs associated with CSP. In the US, BrightSource Energy, which is pursuing CSP prospects in South Africa with Sasol and in which Alstom is an investor, is pursuing single projects at a scale of 250 MW, or larger, which is helping to support localization efforts and lower production costs.
South Africa’s Integrated Resource Plan for electricity envisages the roll-out of 1,200 MW of potential CSP capacity and 8,400 MW of solar photovoltaic (PV) capacity by 2030. However, these allocations may change when the plan is next reviewed.
Bögli argues that unless more is set aside for CSP, the technology is likely to struggle to compete with solar PV, the cost structure for which is currently benefiting from China’s large-scale manufacture and deployment programmes. That said, hybridised CSP facilities, which were likely to incorporate higher levels of local content in the medium term, could immediately become competitive with solar PV.
“We believe solar thermal hybrid cycles can offer a bridging technology and enable CSP to gain scale,” Bögli explains.
He says a preliminary assessment of Eskom’s coal-fired fleet indicated that there was “a 2 GW hybrid potential” associated with the existing fleet and a further 1 GW of potential associated with the coal plants currently under construction. Depending on how the solutions are configured, the inclusion of such plants could not only lower the amount of coal burned, but also add between 5% and 10% of additional capacity.
“At that scale, there would be significant cost reductions in the supply chain for CSP. That would boost the competitiveness of CSP with storage, which, in the long run, should displace coal to a larger extent.”
It may also be preferable for South Africa to consider migrating from a technology-based incentives scheme to performance standards. Hybridised CSP could benefit from such a shift as the plants, which will be located adjacent to existing coal plants, will be close to existing grid connections and offer full dispatchability, while immediately lowering the emission levels.
Alstom believes these benefits would more than offset the fact that the coal plants are not generally situated in parts of the country that enjoy the best direct normal irradiance, or DNI.
Avi Brenmiller, previously of Siemens and currently an independent solar thermal consultant, also believes hybridisation will be critical to realising the relative benefits of CSP when compared with solar PV plants.
Hybridisation will lower the costs associated with the technology in the initial deployment stages. This, in turn, will allow policymakers to properly weigh up the technology’s localisation and grid stability benefits against the immediate price and ease-of-delivery benefits associated with solar PV.
Brenmiller believes that, as with Spain, there is likely to be a solar PV “gold rush” in the early stages of South Africa’s renewables roll-out. But such a roll-out could become increasingly difficult to sustain, or justify, in the context of an ever-increasing demand for local content.
Unlike the solar PV market, which was increasingly dominated by Chinese manufacturers, there is an opportunity for South Africa to become a global CSP hub, owing to the availability of land and the country’s “ideal” DNI conditions.
By catering for hybrid CSP in its planning, South Africa could couple the introduction of cleaner energy solutions with clearly defined timelines on it willingness to subsidise the introduction of renewables solutions.
Brenmiller also argues that, where subsidies are provided, active steps should be taken to promote technologies that are able to keep the subsidies “inside the country”.
Terence Creamer, www.engineeringnews.co.za/