China-based Huaneng Group connected a dual-flywheel frequency regulation system to the grid at its Lanzhou combined heat and power plant on Nov. 6, completing a roughly year-long commissioning process that the group says validates large-scale flywheel storage for coal-fired generation assets.

The system comprises two flywheel units with a combined rating of 5.5 MW and 1.375 MWh. The primary unit — a 5 MW, 1.25 MWh flywheel spinning at up to 3,200 rpm on five-axis active magnetic levitation — is claimed by Huaneng to be the highest-power single flywheel unit in China. A secondary 0.5 MW, 125 kWh inertia flywheel handles smaller frequency deviations alongside it.

Huaneng says the paired design achieves a grid response time below 100 milliseconds and a regulation accuracy above 99.5%, figures the company attributes to the system’s proprietary control integration with the plant’s distributed control system. These performance figures have not been independently verified.

The pairing matters because flywheel storage is not designed for bulk energy delivery — 1.375 MWh is a small buffer — but for speed. Where a lithium battery frequency regulation system typically responds in a few hundred milliseconds, the flywheel array’s sub-100-millisecond response allows the thermal unit to react to grid disturbances faster than its own mechanical inertia would normally permit. The 5 MW primary flywheel handles large frequency excursions, while the smaller unit manages the finer, continuous corrections that would otherwise wear down the larger machine.

Technical development was led by the Xi’an Thermal Power Research Institute, Huaneng’s internal R&D arm, which has accumulated experience across several earlier thermal-storage combined frequency regulation demonstration projects.

Source link