Trial Programme

Subject to a positive stage gate decision, the intention is to install a battery for the demonstration and trial operation of a RaaS scheme at SSEN’s Drynoch primary substation on the Isle of Skye. The scheme would be capable of providing discharge power of 6MVA for up to 3 seconds and 3MW during continuous operation, and depending on the cell technology applied, it is expected that the battery would have a capacity of at least 3MWh.

In addition to providing storage capacity for both the RaaS service and participation in other flexibility markets, this battery system would ensure appropriate integration with the existing network protection schemes for the safe operation of RaaS, including transitions between grid connected and islanded operation, and provide the power required to successfully black start the Drynoch 11kV network.

Initially, sufficient energy will be reserved in the battery to supply the Drynoch site for 3 hours, across 90% of the year – this would cover a high proportion of power outages based on historic data. The remaining ‘headroom’ capacity will be used for revenue optimisation from other markets and services, such as wholesale trading, the Balancing Mechanism, Frequency Response/Dynamic Containment, and the Capacity Market. During the trial period, the operational procedures will be evaluated and refined to further optimise the balance of reserved and headroom capacity, supporting the cost effective delivery of local resilience.

In addition to demonstrating the technical and commercial concepts, the project will investigate a range of other factors identified as influential for the future application and roll out of RaaS, including:

  • the approach to DNO service level requirements specification
  • the role of forecasting, including the potential benefits from enhanced forecasting of:
    • demand – to inform DNO requirements specification and reserved capacity at different points in time
    • interruptions – to inform DNO decisions re ‘standing down’ a RaaS service to release battery capacity for other markets
    • income from other markets – to inform RaaS Service Provider decisions re battery sizing and optimal headroom capacity (and then determine RaaS fees)
  • RaaS fees structures – preferences around the proportion of fixed, availability & utilisation payments, considerations regarding contract vs incentives – rewards & penalties


The image below indicates the timeline for the two stages of the project.

image: Trial Programme