Wind lulls and slews; consequences for the stability of future UK electricity systems

TL;DR

This paper models extreme wind and solar variations in the UK to assess their impact on electricity system stability, emphasizing the need for fast-acting dispatchable generation sources to ensure reliability up to 2035.

Contribution

It introduces models based on real-time data to evaluate future wind and solar variations and proposes proven fast-acting generation technologies to mitigate their effects.

Findings

Wind lulls can last over a week, exceeding stored energy mitigation capacity.

Current CCGTs are insufficiently fast to handle future wind and solar slews.

Fast-acting sources like OCGTs, ICGRs, and energy storage can effectively cope with future variations.

Abstract

As the United Kingdom wind fleet increases in size, wind lulls and slews will increasingly challenge the stability of its electricity system. The paper describes the use of models based on real time records and including solar slews, to investigate the most extreme wind variations likely to be encountered in future, enabling strategies to be devised to mitigate them. Wind lulls are surprisingly frequent, occasionally lasting a week or more, and are always likely to be beyond the capabilities of stored or imported electrical energy to mitigate them. The models indicate that there will be a continuing need for gas powered generation to mitigate wind lulls. Currently, Combined Cycle Gas Turbines (CCGTs) provide most of the dispatchable generation. However, CCGTs are not sufficiently fast acting to cope with the wind and solar slews anticipated in future. The paper suggests that a range of already proven fast-acting sources of dispatchable generation, including Open Cycle Gas Turbines (OCGTs), Internal Combustion Gas-Fired Reciprocating engines (ICGRs) and stored electrical energy systems, should be capable of coping with the largest wind and solar slews likely to be encountered up to the year 2035. Examples are given of the recent introduction of these fast-acting sources of generation which, it is suggested, will progressively replace CCGTs as the wind and solar fleets increase in size. Moreover, we see the pattern of recent investments, summarised in the paper, as a good indication of likely future investments, with OCGT investments mainly serving the 440 kV grid, and ICGRs and stored electrical energy more local networks.