For the first time: Frequency Containment Reserve by privately used swarm of Energy Storage Systems
- Successful pre-qualification as part of the SWARM pilot project
- A contribution to the stabilization of the European power transmission grid system

On 20 July 2015, pre-qualification was for the first time obtained for a network of privately used solar Energy Storage Systems (ESS) for supply of Frequency Containment Reserve (FCR) in Germany. As a result, 65 ESS in the SWARM pilot project were allowed to immediately contribute to stabilization of the power grid. The joint project by the technology and system supplier, Caterva GmbH, and by the Nuremberg community utility N-ERGIE Aktiengesellschaft, is supported by a grant of the State of Bavaria. Siemens AG is a technology partner.
The special feature of the large-scale virtual storage system is the networking of the storage units of household size. The ESS feature lithium-ion storage batteries. Siemens delivers the power electronics system.
Each ESS is provided with its own control unit, so that it can react on a stand-alone basis to grid frequency. The ESS, installed in private households, are connected via the UMTS network, with the control center at Caterva, which coordinates the households as a swarm. The control center acquires the latest individual data on storage-charging levels of the ESS and regulates the swarm such that the FCR, also known as frequency regulation or balancing power, on offer is actually available. At the TenneT control station, the data are forwarded online. The N-ERGIE power plant control station is responsible 24 by 7 for operator control and supervision of the large-scale virtual storage system, as it is for its own power generating facilities.

Double benefits for households
The beneficiaries of the ESS developed by Caterva – each with a total output rating of 20 kW and a capacity of 21 kWh – are the operators of private roof-top PV installations. Thanks to the storage systems, these users can cover 60 to 80 % of their power requirements from their own solar systems – and can at the same time contribute to German energy transition (Energiewende) by providing balancing power.
As a result of the considerably larger storage-battery capacity of the ESS in comparison to conventional PV buffer-storage, participation in the FCR market means no restriction to users in the consumption of the energy that they themselves have generated.

The first 65 ESS installations are distributed throughout the entire distribution system area of N-ERGIE, which is over 8,000 km² in size.

Contribution to grid stability
With provision of positive and negative FCR, the swarm enhances grid stability. Power balancing is necessary to compensate for the imbalance in power generation and consumption in such a way that grid frequency remains constant at 50 hertz. Balancing power is provided by transmission system operators in three specifications: FCR, Frequency Restoration Reserve, and Replacement Reserve (minute balancing power).
Demands placed on FCR are the strictest, since it must be provided within 30 seconds. Before Restoration and Replacement Reserve power, FCR is supplied directly proportionally to the deviation of grid frequency by each ESS.

Swarm Energy Storage Systems satisfy strictest requirements
The ESS swarm system has impressively fulfilled all requirements. The lithium-ion storage batteries installed in the ESS units enable a reaction period of just a few seconds. The large-scale virtual power storage system therefore balances fluctuation in the power grid within seconds and provides a key contribution to system stability.

Lithium-ion Battery