At 4 am on Saturday 22nd February the UK set a new record for the maximum percentage of wind on its power grid at 57.2%. This was enabled through strong and gusty weather from the tail-end of storm Dennis as well as by low overnight demand, the energy mix over the record-setting period can be seen in the graph below. Whilst this weekend saw a record for percentage of demand met by wind, the absolute power that wind has generated reached a maximum of 17 GW a couple of weeks previously. This took place on the 10th of February, during which the national wind fleet reached an instantaneous load factor of 76.8% over midday.
There are a number of factors for the long-term rising record levels, shown below. The most prominent being the ever-increasing wind capacity on the system - totalling 22.1 GW at time of writing - including 0.28 GW recently added by East Anglia One Phase 2 at the end of 2019. The more recent wind farm developments have also enabled higher load factors due to improvements in both turbine technology and the higher wind resource available where they’re being sited. At the same time overall demand has continued to fall, with only 285 TWh of power consumed in 2019 - down 12% from a decade earlier - which makes it easier for wind to make up a larger percentage of total generation.
Most importantly, the rising wind levels are helping to further decarbonise the UK’s electricity system. The National Grid recently reported that this January had the lowest average power carbon intensity on record at 209 g/kWh, a remarkable feat considering that a decade ago this figure stood at 519 g/kWh. One of the main drivers for this has been wind’s displacement of coal off the system. In 2010 coal averaged 30% of demand, but so far in 2020 it has provided less than 5%. This trend is set to continue as greater renewable capacity leads to increased cycling for thermal plants and further erodes their profits.
As new wind penetration records continue to be set every year, so too are new records for balancing service costs and curtailment set. Wind is an intermittent resource with higher speeds found over the border in Scotland, while the largest demand sinks are clustered in the South. This disparity in location highlights the weaknesses in the UK’s existing transmission infrastructure, in particular the two lone transmission lines connecting England to Scotland. This creates problems for the National Grid when there is considerable wind penetration - occuring far more frequently as shown below - and low demand, wind generators must then turned off to avoid system capacities being overloaded.
From December 2018 the 2.2GW Western Link HVDC connection was intended to provide a third pathway for wind power from Scotland to be transported down to demand in the south, as well as to alleviate congestion during high wind periods. Unfortunately though it has been plagued with schedule overruns and unexpected faults. This sporadic operation does, however, give us insight into the effects of additional transmission capacity on Scottish wind curtailment and the UK grid’s balancing costs, something that will be explored further in a future blog post.
