The solution consist of utilising the fast and versatile nature of batteries to provide ancillary services to DSO and TSOs. The primary services are frequency balancing, voltage support and congestion management. The battery types that are addressed in this flexibility solution are medium size batteries and aggregated small domestic batteries. It is also possible to address adequacy by adjusting charging and discharging to peak in an hourly perspective so that the demand curve is more stabilised.
Components & enablers
The following components are required in order utilize the flexibility potential of batteries:
- Installed battery banks either aggregated domestic batteries or larger district batteries.
- Energy consumption/production forecast to predict battery state of charge.
- Algorithm/control system to control and map the available flexibility in the batteries.
- A market solution where the user can sell flexibility the battery can provide.
- Change in current regulatory framework to allocate for medium batteries (reduce fees or charging/discharging, reduce minimum power offers in markets, etc.)
State of the art in application and research
Home batteries have recently caught the public’s attention with products like Tesla’s Powerwall and similar products from other manufactures. However, the aggregation of these batteries are currently only in the pilot phase. District batteries are not as common, but a number of different pilots are looking into potential advantages they can deliver.
Medium scale battery banks have a large power output compared to their energy capacity relative to other storage technologies. This combined with their fast reaction time makes them well suited to provide primary reserve. Simulated primary reserve orders from DSO/TSOs have been tested in pilot project and general show good results. The ELSA project tested a similar order under actual grid conditions, and was able to fulfil the order from the DSO, validating the viability of the solution.
The ability of medium- and small-scale battery banks to deliver secondary and tertiary reserve are limited due to the energy required. However, their fast reaction time enables them to provide “virtual inertia” where the battery acts as a spinning reserve, reaction to small fluctuations in frequency.
Some pilots have tested the capability of batteries to provide voltage control as they have the ability to control their reactive power consumption. These pilots (ELSA, SENISBLE) have proven that medium scale banks have the ability to accurately control the phase angle of the energy they provide to the grid.
The technical aspect of the solution is for the most part ready. For the solution to mature further, certain economical and legislative barriers have to be overcome. New markets has to be established so that economical potential of ancillary serves offered by batteries can be fully exploited and further development of the existing market rules. Legislative actions has to be taken to give smaller players get access to this market in order to realize the full potential of this service. ICT platforms for optimal control of charging and discharging needs to be established.
OSMOSE covers how to combine battery storage with flywheel and supercapacitors to provide a combination service of synthetic inertia, frequency balancing and congestion management services in two demonstrators. Further, OSMOSE demonstrates a lithium-ion battery connected at high voltage in DC to provide voltage control services.
Technology Readiness Level
While battery technology is capable of addressing all the needs mentioned, the projects research how to address barriers to flexible participation in the power system. However, it is currently not profitable. The efficiency and the life time of batteries are insufficient for this purpose. Regulatory and technical barriers prevent batteries from working together with other components in the power system, such as local generation and demand forecasts. Various pilots and demonstrations address potential solutions to these barriers.
Current focus of R&D and research gaps
There is currently a large amount of research being done in the field of battery technology, with research into improving energy density, price, safety, longevity, etc.
Research directly applicable to this solution is research in to how different battery technologies behave when used for grid operation. Especially regarding how the charge/discharge cycle effects the longevity of the battery and what the self-discharge rate is.
 ELSA Pilot 1, 2, 3, 4. [Link]
 INVADE. [Link]
 The Smart Grid Battery Storage Project Prottes. [Link]
 STORY Pilot 5. [Link]
 NETfficient. [Link]
 OSMOSE WP4. [Link]
 SENSIBLE - Nottingham. [Link]