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Inflexible generators face summer curtailment as National Grid prepares for soaring solar

National Grid has warned that inflexible generators such as nuclear and combined heat and power could face turn down instructions this summer to make way for soaring solar generation.

Yesterday National Grid, which owns and operates the UK’s electricity transmission system, issued its Summer Outlook report for 2017, outlining how the body would look to manage the country’s suite of generation assets most effectively.

The report stated that UK solar capacity stood at around 11.7GW as of February 2017, but would grow at a rate of roughly 150MW each month over the course of the next 12 months, totalling 13.5GW by February 2018.

This, when balanced against other generation assets the UK has at its disposal, would pose a dilemma for National Grid with electricity supply increasing as demand decreases during summer months.

National Grid forecasts that summer minimum demand will continue its trend of declining this year, falling to 17.3GW. Summer minimum demand stood at 18.5GW in 2014 and has fallen in each of the last four years.

To maintain the grid’s transmission frequency of 50Hz National Grid has stated there will be a “possibility” that inflexible generators will be issued instructions to reduce their output between late April and the end of summer 2017 in order to balance the grid.

Some flexible wind generation will also need to be curtailed during periods of minimum demand to help it balance the system.

National Grid determines inflexible generation to be technologies which require long notice periods to reduce or increase their output, do not participate in the balancing mechanism or those which have obligations to generate at certain times. These include the likes of nuclear power and CHP, as well as specific hydro or wind generators.

The report underpins the challenges faced by National Grid, including those which have already been seen at least once this year.

In late March prime weather conditions sent minimum afternoon demand tumbling below that of the minimum night time demand for the first time in history, while more than 8GW of solar generation squeezed out fossil fuel generators, which were forced to turn down.

Speaking last month at Imperial College in London Cordi O'Hara, director of UK System Operator at National Grid, explained that ever-decreasing summer miniumum demands mean that "summer is now as challenging as winter".

"Even though we have an obsession with the winter peak in the UK, we do need to think about the summer and its operation too," she stated.