Why is there a perception that the UK faces an ongoing risk of electricity grid failures? At the end of May 2013 the UK had 416 power stations, counting wind farms and hydro dams, ranging in nameplate capacity from 1 to 3870 MW. The combined capacity in 2013, following large combustion plant closures, was 80,514 MW down from 92,044 MW in 2012 (Figure 1). With peak winter demand roughly 55,000 MW there still seems to be ample spare capacity to guarantee electricity supplies (Figure 1). Why then is there so much talk on the media, blogs and from the CEO of National Grid about pending blackouts in Britain? The answer is not what many may presume it to be.
Figure 1 During the 1960s to the 1980s Britain was largely dependent upon coal and nuclear power for electricity supplies. Natural gas (CCGT) was introduced in the early 1990s and expanded year on year until 2004. At the end of that decade a second phase of CCGT building got under way adding a further 9,274 MW of capacity, which with hindsight appears to be an extraordinary investment decision. The closure of 11,530 MW of large combustion plants has resulted in the decline of UK generating capacity. The expansion of wind got underway in the early 21st century. Wind capacity is not varied into the future. It can be expected to grow some, but not at the historic rate since companies are becoming shy of investing in Britain’s chaotic energy market. Data from DECC table dukes5_11.
Britain has 31,637 MW of CCGT capacity (combined cycle gas turbines) but lacks access to sufficient gas to run this fleet at anything close to capacity. During the cold spell at the end of last winter when gas storage was run down to empty the maximum output from the CCGT fleet was 22,000 MW, just 70% of the installed capacity. The closure of 11,530 MW of large combustion plants (coal and oil) has of course created the electricity supply crisis. But given that these power stations are now gone, it is a shortage of gas that creates the current blackout risk.
Figure 2 shows the pattern of electricity demand in the UK for January and July 2009. In 2009, peak demand was 58.9 GW at 6pm on a Tuesday in January and the minimum demand was 22.3 GW at 6 am on a Sunday morning in July. Peak demand is 2.64 times greater than the minimum demand and the electricity delivery system requires the flexibility and controllability to match supply with demand exactly at all times.
Figure 2 UK electricity demand for January and July 2009 shows three cycles in the pattern of demand. The daily cycle has peaks during day time, with maximum demand normally at 6pm, and troughs at night. The weekly cycle shows increased demand Monday to Friday with reduced demand on Saturday and Sunday. The annual cycle shows increased demand in winter compared with summer. This provides a picture of activity and expectations of the society we live in. We like to stay warm in winter, we go to bed at night and we have weekends off work.
For the time being, blackout risk in the UK is confined to the short periods of peak winter demand that invariably occur at 6pm in the winter months. And the blackout risk is hightened towards the end of the winter when our’s and Europe’s gas storage has been run down. Figure 3 shows gas generating capacity curtailed to 22,000 MW which is an approximation for current gas supply limits. Wind, that is not dispatchable, is removed.
Figure 3 An approximation for the deliverability from UK power stations with CCGT curtailed to 22,000 MW and wind power removed. On a calm, cold weekday at the end of a long cold winter, there is a risk of blackouts in the UK and that risk will increase as the decade progresses.
This now shows the nature of the blackout risk that we face. Should we have a cold winter that drains storage and cold weather in February or March and little wind across the UK and near continent then there is a blackout risk, especially if there are outages at nuclear or other generating plant, which is quite common. This risk will increase towards the end of the decade if planned nuclear closures go ahead and if there are further closures of large combustion plants.
At present, understanding the blackout risk in Britain boils down to understanding the security of future gas supplies and that is not a simple task. The hightened blackout risk of March 2013 came about because of LNG Heading East as a consequence of the Fukushima nuclear disaster in Japan. Closer to home, UK supplies may get some relief in the next few years as a number of new projects come on line, and if there are significant shale gas discoveries. Offsetting that are plans in the Netherlands to cut production in the giant Groningen field and the inevitability of a future peak in Norwegian gas production. We seem set to become increasingly reliant upon Russia for gas supplies that also provides our electricity security.
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Energy Matters’ 2050 pathway for the UK
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