On the 7th of November the wind farm developer and green electricity supplier Ecotricity placed a double page spread advertisement in the Guardian newspaper. This advertisement claimed that wind power played a significant part in securing supplies on the 19th of October, when four nuclear power stations were already offline and the system came under further pressure in the evening because of a fire at Didcot B power station, a Combined Cycle Gas Turbine (CCGT) power station.
Specifically, Ecotricity wrote that:
“No one noticed that around nine million homes worth of electricity had electricity had simply ‘disappeared’ after four nuclear power stations had shut down and Didcot went up in flames. No one noticed because Britain’s windmills carried on turning, powering almost 25% of our country. It was a historic event that went almost unnoticed; one revolution after another quietly secured our energy needs. The lights didn’t go out. We have wind energy to thank for that.”
These claims are repeated on the Ecotricity web site: “Nothing Happened”.
In yesterday’s Sunday Telegraph (23.11.14) Christopher Booker’s column discussed the Guardian advertisement, and called its accuracy into question: “Revealed: the Guardian Wind farm advert that tried to pull the wool over our eyes”
As Mr Booker notes, REF has looked at the historic electricity data available to us to see what actually happened on the 19th October and whether Ecotricity’s claims can be substantiated. Our conclusion is that they cannot, and the claims are misleading. The following account, based on the data in the public domain, shows why.
As background to the history of event on the 19th of October, it must be noted that while the advertisement refers to the fact nuclear power stations were offline on that day, this nuclear outage was a combination of scheduled and longer term work which had already been accommodated in the National Grid planning for provision of electricity. In other words, the nuclear outage was expected and planned for, and is strictly speaking irrelevant to the actions taken in response to the immediate problems arising from the emergency on the evening of 19th of October.
The events of that day can be summarized thus: On the 19th of October 2014 Didcot B5, the CCGT unit that caught fire was not scheduled to generate electricity for the entire day. Instead it was scheduled to ramp up from zero to 720 MW and then back down to zero, starting the process at around 5pm, then reaching 700 MW at 7:30pm, holding that level until 10:30 and then ramping down again to zero at half past midnight. Thus, it seems the plan was for it to provide electricity for the evening hours when demand would be high.
The fire meant the B5 unit had to reduce output rapidly and prematurely between 8:30 and 9pm. Consequently there was a shortfall of generation for the hours of 9pm to midnight. For one and a half hours of that time the shortfall was 700 MW, and for one and a half hours there was a smaller lack of capacity.
During the immediate period after Didcot B5 stopped it appears from the public-domain electricity data that large coal generators, mainly Eggborough, but also Fiddlers Ferry, and Cottam, picked up the slack, with some help from Combined Cycle Gas Turbines, initially Immingham and Medway and then Langage.
Specifically, it would appear that in order to address the problem and provide the heavy lifting required, National Grid kept Eggborough (a 2,000 MW coal station) on the system for an hour or so longer than the station had had been planning to generate. After that, Langage an 885 MW CCGT generator was kept on the system longer than scheduled.
In other words, supplies to consumers were secured in spite of the fire at Didcot and no one noticed that the system was under stress because coal and gas generators were able at short notice to step into the breach left by Didcot B. Wind power was not only essentially passive but was in fact declining during the event, as can be seen from the REF online fuel mix data tables and charts. (The Didcot event would have impacted settlement periods 42 to 48 on 19 October and settlement period 1 of the next day.)
Furthermore, throughout the whole of the 19th October, including while this event was taking place, wind power in Scotland was being constrained off the system because of network limitations on the lines running into England. By our reckoning the volume of wind energy (MWh) constrained off between the hours of 9pm to midnight was roughly the same as that lost during that period because of the Didcot fire, as can be seen from the REF constraint payment tables.
It is almost certain that the wind-induced shortfall throughout the day would have been made up by fossil fuelled conventional generation, though only National Grid can be specific about the measures it took to replace constrained off wind power.
Thus, in summary it was not wind power that made up for the loss of Didcot B5, as Ecotricity imply; on the contrary, it was conventional power stations, namely coal and gas generators, that stabilized the system. Moreover, wind power was causing a separate problem for the grid system operator.