Many MindedA 5.5 MW flywheel pair now steadies the grid at a Gansu coal-heat plant
Huaneng Group connected a dual-flywheel frequency regulation system to the grid at its Lanzhou combined heat and power plant on November 6, 2026. The combined rating is 5.5 MW and 1.375 MWh. Installation and the mandatory 168-hour continuous trial run were finished in December 2025, followed by a period of monitored operation before formal connection.
The main unit is a 5 MW, 1.25 MWh flywheel spinning at up to 3,200 rpm on five-axis active magnetic levitation. Huaneng says it is the highest-power single flywheel unit in China. A smaller 0.5 MW, 125 kWh inertia flywheel handles minor frequency deviations. Huaneng reports a response time under 100 milliseconds and regulation accuracy above 99.5%, credited to tight integration with the plant's control system. Lithium battery systems typically respond in a few hundred milliseconds. The Xi'an Thermal Power Research Institute, Huaneng's in-house R&D arm, led development.
Why it matters: wind and solar make grid frequency harder to hold, and Gansu is a core region of China's northwest renewables buildout. Flywheels are claimed to last tens of millions of cycles, with no chemical degradation and no fire risk. If that holds, the balancing service that variable renewables need could be supplied without consuming battery capacity. Huaneng also cites lower penalties and new revenue under China's two-part ancillary services rules.
Caveats: the speed and accuracy figures are not independently verified, and the record claim is Huaneng's own. The 1.375 MWh buffer is tiny, since flywheels provide speed, not bulk storage. They also cost more per megawatt than lithium batteries today, and the unit sits at a coal-linked plant. Whether this repeats elsewhere depends on how ancillary markets pay for millisecond response.
Source: pv magazine