Security of electricity supply

When the Longannet power station closed in 2016 it raised debate about Scotland’s ability to meet its peak demand for electricity. In the period until 2030 we are expecting further major changes to the Scottish electricity system:

• Hunterston and Torness nuclear stations are both expected to close by 2030,
• there is no certainty over the long term future of Peterhead gas power station,
• the capacity of wind generation is expected to grow, and
• the size of the peak demand is also likely to grow.

As a result the flows of electricity across the transmission network will be considerably more variable. Towards the end of the 2020s, at the latest, it is likely that we will need either new transmission links with the rest of Great Britain, or new generation capacity that is capable of being scheduled in advance, to ensure Scotland’s peak demand security-of-supply.

This study analyses the current level of transmission import capability and investigates the transmission import capability required going forward.

Main findings:

• Development of either new transmission links or new schedulable generation capacity in Scotland is likely be required by the late 2020s. Given the time scales normally required for transmission and generation projects, it is important that system planners, regulators and policy makers ensure that further examination of the requirements and potential options begins soon.
• Scottish peak-demand security is only one of a number of aspects of security-of-supply. Ensuring that future system developments support all aspects of security will be vital to keeping the system operational and resilient. Regulators and policy makers need to be aware of the technical and multi-dimensional nature of electricity security-of-supply, and ensure that generation and network resources are designed to ensure that all aspects of security are maintained to acceptable levels.

• The current deterministic calculations used to estimate the required capability of the transmission system in respect of reliability of supply need to be revisited in light of two factors:
  • • (i) the increased penetration of weather dependent renewable resources such as wind; and
    • (ii) the emergence of a situation where large regions of the GB system, such as Scotland, have a small number of large conventional generation units.