As the Dutch national grid processes more and more renewable energy, TenneT TSO faces a sharp growth in sudden frequency variations. S4 Energy has unveiled a new storage solution that helps TenneT meet this challenge, by providing an unusually fast and flexible frequency containment reserve. The technology also paves the way for further innovations, such as ‘virtual power plants’.

The new storage system, which was officially opened on the 23rd of November, enables S4 Energy to supply TenneT TSO with 2.8 MW of regulating and primary reserve capacity. “In addition, this new technology allows us to deliver a completely new type of service: a large and extremely fast power supply for damping sudden frequency variations”, says Dominique Becker Hoff, project director at S4 Energy.

The need for speed

The new technology meets a clear and growing need, according to Danny Klaar, manager System Operations International Development at TenneT TSO. “Wind and solar energy yields - as well as the increasing number of cross-border trades between individual countries - are unpredictable, resulting in a sharp rise in short, sudden frequency variations. A crucial advantage of this new storage system is that in such situations, power can be stored or fed back into the grid at an unprecedented speed.”

Flywheel/battery combination

The new system owes its flexibility and speed to a smart combination of storage technologies. Becker Hoff: “Our proprietary KINEXT flywheel unit can supply instantaneous power for short periods of time and without capacity loss. The batteries offer higher capacity, but are also prone to degradation. In other words, the two technologies are perfectly complementary. The KINEXT unit supplies continuous reserve power, the battery system only kicks in during longer frequency variations. This setup slows down the batteries’ degradation, which means the system has a minimum lifespan of 10 years.”

Virtual power plants

“It’s a unique and very innovative combination”, Klaar agrees. Which in his view also opens up opportunities for boosting the share of renewables in the energy mix. “In the long term, traditional power plants will be decommissioned and replaced by a large number of smaller energy producers, especially solar and wind farms. This technology can be used to combine such decentralized sources in ‘virtual’ power plants.” Such virtual power plants would then be able to deliver the same steady, reliable supply of energy currently provided by fossil-fueled plants.

S4 Ancillary Services

The installation in Almelo was built and is managed by S4 Ancillary Services, a joint venture between S4 Energy and EFO (Energiefonds Overijssel/Energy Fund for the Province of Overijssel). EFO’s involvement in this project underlines the impact of this new technology on creating a more sustainable energy supply. EFO invests in projects that make a meaningful contribution towards the Province of Overijssel’s goals of 20% renewable energy by 2023.