South Africa’s electricity grid faces a concrete, daily problem: when evening arrives and millions of households switch on lights, cook dinner and turn on televisions, rooftop solar panels produce nothing. That gap, repeated every night across a country where coal supplies 74 percent of power and aging plants are retiring fast, is the central challenge that concentrating solar power is built to solve.
Unlike photovoltaic panels, which convert sunlight directly into electricity only during daylight hours, concentrating solar systems use mirrors to focus sunlight into intense heat. That heat warms molten salt to around 565 degrees Celsius, stores it in insulated tanks, and later uses it to drive turbines and generate electricity well after sunset. Modern plants can sustain generation for 12 to 20 hours. In summer, some run almost continuously. This ability to deliver power on demand, known as dispatchability, addresses a core public need that rooftop solar simply cannot meet.
Additional reference context is available at https://theconversation.com/south-africa-is-overlooking-solar-technology-that-can-keep-generating-electricity-after-sunset-283857.
South Africa is exceptionally well-positioned for this technology. The country has some of the world’s strongest direct normal irradiance, the straight-line sunlight these systems require. Only Chile’s Atacama Desert ranks higher. Clear skies, dry climate and low cloud cover make the conditions close to ideal. Yet the government has not approved a single new concentrating solar power project since 2014, even as the roughly 600 megawatts already built supply enough electricity for an estimated 350,000 to 400,000 average three-bedroom homes each year.
The reason for this neglect comes down to a flawed cost comparison. Planners have weighed the price of rooftop solar during daylight hours, around US$35 per megawatt-hour, against the full cost of building concentrating solar plants. On that narrow basis, rooftop solar looks cheaper. But the comparison ignores what happens after dark. Adding batteries to store enough power for a full night pushes the cost of solar-plus-storage to about US$166 per megawatt-hour. Concentrating solar power, which stores heat rather than electricity, delivers overnight generation at roughly US$95 per megawatt-hour. Storing heat is far cheaper than storing electricity in batteries for extended periods.
Meanwhile, the government is preparing to invest R2.2 trillion in new nuclear capacity, which costs around US$140 per megawatt-hour. Concentrating solar power offers comparable or better reliability at substantially lower cost to the public purse.
The consequences extend well beyond the electricity bill. Most of the cost of a photovoltaic system lies in the solar cells themselves, which are almost entirely imported and only assembled in South Africa. Concentrating solar plants, by contrast, are built primarily from concrete, steel and glass, materials South African industry already produces at scale. Up to 60 percent of the components for a concentrating solar plant could be sourced from local factories, creating manufacturing employment that photovoltaic assembly cannot match.
South Africa has already demonstrated world-class capability in this field. The Stellio heliostat, an award-winning mirror system regarded internationally as one of the most efficient and lowest-cost designs, was conceived and designed for local manufacture in South Africa. China now deploys it at scale. The pioneering work was done here; the industry was not.
Research from Stellenbosch University’s Solar Thermal Energy Research Group, published in full at theconversation.com/south-africa-is-overlooking-solar-technology-that-can-keep-generating-electricity-after-sunset-283857, indicates that South Africa’s grid has room for 6 to 10 gigawatts of concentrating solar power. That capacity could supply between 3.5 million and 6.5 million average three-bedroom homes over a year, depending on how plants are operated. Local manufacturing, once developed, could reduce costs further still.
The barriers are not geological or industrial. South Africa has the sunlight, the materials, the engineering expertise and the research base. What it lacks is a procurement programme that requires future projects to source components locally, and an energy planning framework that calculates the true delivered cost of electricity to citizens rather than the cost at the point of generation. The Department of Electricity and Energy, together with the Council for Scientific and Industrial Research, already has the modelling capacity to make that calculation. The Department of Trade, Industry and Competition and the Industrial Development Corporation could apply the same local-content requirements that grew the photovoltaic assembly sector.
The open question, as coal plants continue to retire and evening demand continues to go unmet, is how long the country will keep comparing the wrong numbers.