All units online for record-breaking hydroelectricity station in East China

The full operation of a record-breaking pumped-storage hydroelectricity station in East China is poised to further accelerate the nation's green energy transition and fortify long-term grid security, said industry experts.

Marking a monumental technological leap in ultra-high head and large-capacity energy storage, the Zhejiang Tiantai Pumped-storage Power Station, which brought all its units online last week, serves as a crucial "regulator" for the country's modern power system.

As the first facility of its kind to become fully operational during the 15th Five-Year Plan (2026-30) period, the 1.7-gigawatt project, located in Taizhou, Zhejiang province, boasts the world's highest rated water head at 724 meters, according to its operator China Three Gorges Corp (CTG).

In hydroelectric engineering, water head refers to the vertical drop between the upper reservoir and the turbine units. A higher water head means greater water pressure and potential energy, allowing the station to generate more power using less water.

However, a massive 724-meter drop creates immense pressure, demanding state-of-the-art materials and cutting-edge engineering to ensure safe operation.

The megaproject features four 425-megawatt reversible pump-turbine units, representing the largest single-unit capacity domestically, and utilizes a domestic record 483-meter single-stage inclined penstock, it said.

Primarily tasked with peak-shaving, valley-filling, frequency regulation and emergency backup for the Zhejiang power grid, the station is expected to generate 1.7 billion kilowatt-hours of clean electricity annually.

Overcoming the immense challenges of a world-record water head, the project team systematically mastered the core manufacturing and application technologies for units exceeding 700 meters in head and 400 MW in capacity.

Furthermore, the project pioneered the large-scale domestic application of 1,000-megapascal high-strength steel and implemented innovative low-heat cement techniques to prevent rock-fill dam face cracking. It also introduced unmanned, smart construction equipment — such as autonomous bulldozers — ensuring high-quality, collaborative operational efficiency.

The Tiantai station's completion aligns with a broader national strategy to utilize pumped-storage facilities as vital engines for sustainable development.

According to a recent report by the China Renewable Energy Engineering Institute, the sector will see a rapid leap over the next five years, with China expected to add roughly 100 million kilowatts of new capacity.

China has been steadily advancing the construction of approved projects, striving to meet the power system's demand for 400 million kW of flexible capacity by 2035.

Zhao Zenghai, deputy head of the institute, emphasized that these facilities are increasingly irreplaceable for ensuring safe grid operations amid expanding renewable energy integration.

He pointed out that while earlier projects primarily addressed peak-shaving in eastern load centers, future layouts will heavily support cross-provincial power transmission from new energy mega-bases in central and western regions, significantly enhancing transmission corridor efficiency.

Zhao believes that compared with the 14th Five-Year Plan (2021-25) period, the sector's development scale is expected to experience a rapid leap in the next five years.

Ye Xiaoning, a senior engineer at the State Grid Energy Research Institute, observed that modern pumped-storage stations have shifted from prioritizing sheer scale to balancing scale with economic viability and ecological safety.

They will play a dual role: balancing rapid grid responses in the east while smoothing out wind and solar volatility in resource-rich western and northern areas to boost outbound transmission, he said.