Dutch startup stabilizes Netherlands’ grid with 9 MWh battery-flywheel storage facility


S4 Energy, a Netherlands-based flywheel technology, and Swiss conglomerate ABB recently switched on a storage project that combines battery and flywheels to help the Dutch grid maintain a stable frequency of 50 Hz.

The facility is located in Heerhugowaard, in the province of North Holland. It features a 10 MW battery system and a 3 MW flywheel system, which are both connected to a nearby wind farm.

“The hybrid storage facility, batteries and flywheels can also support PV production facilities,” a spokesperson from ABB told pv magazine. “They can be used to curtail and smoothen the PV power profile on a short-term basis, within 15 minutes.”

The storage system has a storage capacity of around 9 MWh and relies on ABB's regenerative drives and process performance motors, which power the Kinext energy-storage flywheels developed by S4 Energy. Each Kinext unit includes a flywheel with a mass of 5,000 kg and a large diameter. The companies said it is able to spin relatively slowly, at 1,800 rpm, but it can reach a maximum speed of around 950 km per hour.

“If necessary, a Kinext unit can provide more than 1 MW of power,” said S4 Energy. “Kinext units can be used as standalone storage systems or as part of a larger set-up, in which one or more Kinext units work together with other storage technology such as battery systems.”

ABB's motor and drive use surplus power from the electricity network to speed up the rotation of the flywheel, which stores power in the form of kinetic energy and releases it back into electricity within milliseconds.

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“With flywheel storage, charging and discharging is very fast. Flywheels also have a long cycle lifetime, as they do not suffer any degradation in their capacity and do not require high maintenance costs. In addition, they typically have a low environmental impact,” an ABB spokesperson said. “The levelized cost of storage (LCOS) depends on the application, but is between €0.020 ($0.020)/kWh and €0.12/kWh.”

ABB says that flywheel storage enables fast charging and discharging. Flywheels also have a long cycle lifetime, as they do not degrade and do not require high maintenance costs. In addition, they typically have a low environmental impact. S4 Energy claims its flywheel system has a cycle efficiency of more than 92% and a lifetime of over 20 years, or more than 1,000,000 cycles.

“There are similar projects in the pipeline, and other potential applications for the flywheel. For example, a flywheel peak shaving application for a harbor crane is currently being installed in the port of Rotterdam, Netherlands,” the ABB spokesperson said. “The pilot was aimed at the development of the algorithms to smoothen the wind power profile, in order to produce a profile that is similar to the forecasted production profile of the wind turbine.”

S4 Energy currently has 19 MW of storage facilities in operation and another 6 MW under construction.

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