Last week saw a major milestone in the decarbonisation of the UK’s power sector, as Emma Tribe and David Thomas from Elexon explain.

Following on from recent record solar and wind generation, we saw another first last Friday; 21 April 2017 was the first 24-hour period since 1880s during which no coal was used to generate electricity.

To put that in context, the last time this occurred Britain was still undergoing an industrial revolution, Queen Victoria was on the throne, and confederate colonel John Pemberton was still several years away from concocting the ‘liquor free’ tonic which he named Coca-Cola!

Coal generation ceased at 22:00 on 20 April, with no coal balancing mechanism units (BMUs) generating again until after midnight on 22 April. So what filled the gap left by coal?

The majority of generation seen on 21 April was sourced from gas (50 per cent), with nuclear contributing 21 per cent and wind a further 12 per cent. The remaining generation was mainly split between interconnectors (eight per cent) and ‘other’ generation (seven per cent), with only negligible pumped storage and hydro.

The shift away from coal generation is not a new phenomenon. Numerous factors have impacted generation from coal BMUs: the lower cost of gas, the increase in renewable generation and the UK and Europe emissions targets. It is slightly surprising for the first ‘no coal day’ to occur on a weekday, rather than at the weekend when demand is lower.

The graph below compares the total volume of generation the third week of April across the last three years (2015, 2016 and 2017). The decrease in volume generated from Coal BMUs is dramatic reducing from 1,560GWh in 2015 to 471GWh in 2016 and down to 31GWh in 2017. Coal generation reduced from 29 per cent of total generation in this period in 2015 to less than one per cent for the same period in 2017.

On one day in April two years ago (2 April 2015), coal generation across the day was 331GWh. In contrast, total coal generation for this month so far (up to 23 April) has been 298GWh.

National Grid’s 2017 summer outlook report included a forecast of expected costs of coal and gas generation over this summer. Their analysis concluded it is unlikely that coal generation could make a profit by running at either baseload or peak across the summer. Lower gas prices will mean gas generation is likely to continue to be the dominate generation type.

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