Generating solar energy nonstop without sunlight

LANZHOU — In Guazhou county of Northwest China's Gansu province, a solar thermal energy storage power station can generate power for 24 hours nonstop.

Its main project has begun commissioning and will be put into operation by the end of this year, according to the China Three Gorges Corporation.

The solar thermal energy storage power station can generate electricity with or without direct sunlight, thanks to heliostats and molten salt, while achieving stable all-day power output.

Two adjacent heat-absorbing towers, sharing one turbine generator, are settled in the power station. Beneath the towers, heliostat arrays are installed, covering a lighting area of 800,000 square meters. Notably, the heliostats can pivot and follow the direction of sunlight, like a sunflower tracking the sun through the course of the day.

Assisted by such a function, which turns sunlight into green energy, the power station attracts the sunlight into the two heat-absorbing towers to power up the turbine generator.

With a very high definition, the heliostats can reach 94 percent reflection efficiency, which reflects more sunlight to the heat-absorbing tower, greatly improving the efficiency at power generation. At the foot of the heat-absorbing towers, there are two huge storage tanks filled with molten salt at 300 C and 500 C.

The molten salt in its liquid form can store several times more heat than water. The solar energy collected by the heat-absorbing towers during the day is stored in the form of heat in the salt, achieving a stable and continuous power output for 24 hours.

Once in operation, the power station will serve as the basic regulation power supply, forming a clean energy base in a total installed capacity of 700,000 kilowatts together with the surrounding photovoltaic and wind power. The annual electricity generation will reach 1.8 billion kilowatt-hours, cutting about 1.53 million metric tons of carbon dioxide emissions.

Since China introduced new energy bases in its vast deserts, including the Gobi, large-scale solar thermal power generation development has also kicked off.

Solar thermal power generation integrates energy storage and power generation, which is one of the effective means for new energy to replace traditional energy safely and reliably, said Hu Wenping, an official at the China Electric Power Planning and Engineering Institute.

According to a blue book on China's solar thermal power industry in 2023, the total installed capacity of the country's solar thermal generating units above megawatt-level reached 588 megawatts, accounting for 7.8 percent of the global cumulative installed capacity of solar thermal power generation.

Xinhua