Q2 2017: Reaching below 100 g/kWh

by Dr Iain Staffell – Imperial College London 

Low-carbon is the new normal for Britain’s power system. 

Carbon intensity over the quarter averaged 199 g/kWh: 10% lower than the previous minimum set last year. For context, the carbon intensity averaged 740 g/kWh in the 1980s and 500 g/kWh in the 2000s.

The carbon intensity of Britain’s electricity now regularly dips below 100 g/kWh, showing that deep decarbonisation is already plausible. The sunny and windy Sunday afternoon of June 11th (see previous figure) saw grid carbon intensity hit an all-time low of 71 g/kWh, and remain below 100 g/kWh for several hours.

The figure below shows the carbon intensity of electricity supply during each half-year. In 2010/11, a third of hours were high-carbon with emissions over 500 g/kWh, the rest were mid-carbon (250-500 g/kWh). Lower coal and higher gas prices in 2012/13 saw more high-carbon hours as coal stations displaced gas until the Carbon Price Support made coal-fired generation less economic. With strong growth of renewable output, low-carbon hours (125–250 g/kWh) are now rapidly emerging, and occurred half the time over the last twelve months. There hasn’t been a single high-carbon hour in the last two years, and we are now seeing the first ‘lowest-carbon’ hours with less than one quarter of the carbon intensity. So far, 2% of hours in 2017 have been in this lowest carbon category, but in future these will need to become the norm to hit the country’s decarbonisation targets.

The Committee on Climate Change’s recommendation for 2030 (electricity below 100 g/kWh) can now be achieved for short periods of time, although meeting the target on individual days is easier than over the year as a whole. Nonetheless, the path to low-carbon electricity supply appears more certain these days, but major challenges lie ahead in decarbonising the heating and transport sectors.

The hourly generation mix in each half-year grouped by carbon intensity, with projections¹ for 2020 and 2030

Authors: Dr Iain Staffell, Professor Richard Green, Dr Rob Gross, Professor Tim Green and Dr Jonathan Scurlock

1: Future projections are based on an average carbon intensity of 175 g/kWh in 2020 (from National Grid’s Future Energy Scenarios) and 100 g/kWh in 2030 (from the Committee on Climate Change recommendations). The share of each category was estimated by reducing the carbon intensity of each hour during 2016 by 74 g/kWh for 2020 and 149 g/kWh for 2030. This preserves the distribution of carbon intensities across the year, which has remained similar since 2009 with a standard deviation of ± 66 g/kWh. This gives one possible share of generation that is consistent with meeting the annual target, rather than a precise forecast.