China has switched on a world-first solar thermal power station in the Gobi Desert that is said to be a cheaper and more efficient use of the technology with potential to be scaled up.

Built by the China Three Gorges Corporation, the plant in Guazhou county in northwestern Gansu province uses two towers feeding a single turbine system – the first time this has been done.

Nearly 27,000 mirrors have been installed to focus sunlight onto the 200-metre (656 feet) towers, which are about 1km (0.62 miles) apart.

This produces concentrated heat that melts and stores salt at up to 570 degrees Celsius (1,058 degrees Fahrenheit). That in turn creates steam to drive the turbines and keep the power flowing, even after sunset or on cloudy days.

The dual towers allow the east tower to capture morning sun, while the west tower takes over in the afternoon, state broadcaster CCTV reported last week.

That makes them about 25 per cent more effective than a single-tower design, the report said. And with the two mirror fields partly overlapping, fewer mirrors are needed – a key saving since they account for most of the construction costs.

The design – and potentially multi-tower systems in the future – breaks the capacity limits of single-tower plants and opens a new path for scaling up solar thermal power in China, according to CCTV.

Unlike many earlier solar thermal projects in Europe and the United States that operated as stand-alone plants, the Chinese facility is part of a larger clean energy hub. Combined with vast solar and wind farms already in the area, the hub is expected to supply electricity for about half a million households each year.

Solar thermal power has one major advantage over solar panels: it can keep generating electricity after dark.

The technology boomed more than a decade ago in Spain and the US under generous government subsidies, but lost ground as photovoltaic, or PV, costs plunged. With utility-scale PV prices dropping by over 80 per cent, many solar thermal plants struggled financially or went bankrupt.

In China, it was a different story. The country first built vast amounts of low-cost PV and wind capacity, especially across its sunny, windy western regions such as Gansu, Xinjiang and Qinghai. That created a new challenge since the sources are intermittent and cannot match demand at night or on calm, cloudy days.

That was when solar thermal power emerged – not to compete with PV, but to complement it by filling the gaps, said Wang Zhifeng, a leading researcher at the Chinese Academy of Sciences.

Wang – whose team tested a new-generation solar thermal facility last year that uses ceramic receivers and supercritical carbon dioxide turbines – said cost remained the biggest challenge.

About 60 per cent of the cost came from the mirror system since it must be precisely curved, polished and able to track the sun with high accuracy, Wang said during a science outreach event in 2022.

His team has experimented with a special “metamaterial” – a flat surface patterned at the microscopic level to bend and focus sunlight without curved mirrors. Wang said that method could make flat panels concentrate sunlight like a curved mirror, potentially cutting mirror costs by up to 60 per cent.

According to CCTV, China has already built 21 commercial solar thermal power plants with a combined capacity of 1.57 million kilowatts. Another 30 projects under construction will add 3.1 million kilowatts.

Globally, the largest operating solar thermal complex is the 700-megawatt Noor Energy 1 project in the United Arab Emirates. China has also contributed to major plants such as Morocco’s Noor complex and Chile’s Cerro Dominador, where solar thermal power remains part of national clean energy strategies.