Figure 1 Stacked area chart showing the contributions to the UK grid from various generating sources for March 2013. Similar charts for January, February and April can be found in an earlier post. With 9000 lines of data, it is not easy to display a time scale on the x-axis. The peaks represent days with the 1st of March to the left of the chart. The “Other” category includes French, Dutch, Irish and EW imports / exports via inter-connectors, pumped storage, conventional hydro, oil, open cycle gas turbines and “other”. Data from BM reports as reported by Gridwatch.
Balancing Mechanism (BM) reports as recorded by Gridwatch provide insight to exactly how the UK grid is coping with and responding to the ever growing amount of intermittent wind energy. The key observations are detailed below, the evidence is below the fold.
- There is no evidence that integrating wind has impaired the efficiency of combined cycle gas turbine (CCGT) or coal fired generation.
- The rate of load change to accommodate wind is no greater than the diurnal load cycle to accommodate demand.
- Wind is variable and is just as likely to be blowing at night when demand is low as during the day when demand is high (Figure 1).
- CCGT (gas) bears the brunt of load balancing in the UK for both diurnal demand and wind variability.
- A consequence of this is that CCGT is losing market share to wind whilst providing an ever larger and more valuable load balancing service.
- Reduction in coal generating capacity meant that coal fired power was running at capacity for periods last winter.
- Nuclear was also running at capacity for periods during the winter months.
- UK gas storage was run down to near zero April 2013 (source Rune Likvern at Fractional Flow), the result of a colder than normal winter and competition for LNG from Japan (Source National Grid).
- Continued growth of wind is going to squeeze CCGT (gas) out of the system – which is a consequence of the 2008 Climate Change Act. At some point CCGT generation may become unprofitable, but since it also provides essential grid balancing service, the industry may have to transfer to state ownership.
- Wind electricity displacing imported gas has a positive impact upon UK trade balance.
- Within a tight European gas market, wind power is making a contribution to keeping the UK grid operational. Without wind, the UK gas and electricity security situation would have been worse last winter
- Had the UK government commissioned 20GW of nuclear power 10 years ago, this situation could have been avoided.
The efficiency of CCGT and coal fired power generation
Figures 2 and 3 show the thermal efficiency of CCGT and coal fired plant. There is no significant impairment of efficiency stemming from the increase of intermittent wind in recent years. Data from DECC, spread sheet called Electricity since 1920 historical data.
Figure 2 CCGT thermal efficiency
Figure 3 coal thermal efficiency
Rate of load change to accommodate wind
Figure 4 shows the load variance of nuclear, coal, CCGT and wind for the UK in March 2013. The chart shows that both CCGT and coal undergo rapid load shifts on a diurnal basis to accommodate demand. The rate of load change to accommodate wind is lower than the demand load shift.
Figure 4 Load distribution between the 4 main generating sources. A value of 1 means all plant is operating at capacity. A value of zero means that all plant is idle. The daily fluctuations in CCGT and coal are to accommodate the diurnal cycle in demand. It is quite clear that when the wind is blowing the rate of diurnal cycling is barely affected. It is equally clear that when the wind is blowing, the load factors on CCGTs, and to a lesser extent coal, are reduced meaning that the quantities of imported fossil fuels is also reduced.
The variable nature of wind
One of the main limitations of wind is that without storage we have no control over when the power is delivered. An examination of Figure 1 shows that on occasions the wind blows during the day and makes a significant contribution to peak load. It also blows at night, making a significant contribution to off-peak load. But on an equal number of occasions it makes no contribution at all to UK electricity supply meaning that back-up is required from those sources excluded from the market when the wind is blowing, i.e. CCGT and coal. Conventional fossil fuels are being required to provide essential grid balancing services whilst losing market share.
CCGTs losing market share
Figure 5 illustrates quite clearly that gas use for electricity generation has declined since 2010. Figures 1 and 4 show that wind substitution for gas is the main cause. The recession that has resulted in a decline in electricity consumption is an additional cause. Improved energy efficiency at home likely plays a tertiary role.
Figure 5 This chart shows what we use natural gas for. The lions share goes to domestic heat and cooking and for electricity generation. It is striking to see how domestic demand rises substantially in the winter quarters – oct-dec and jan-mar. The overall fall in demand since 2010 results from a combination of factors – higher prices leading to energy poverty, recession and energy efficiency. The fall in gas consumed for power generation reflects substitution of gas by wind electric.
Coal and nuclear running at capacity
Under the EU Large Combustion Plant Directive, 9 large UK power stations have closed or are set to close representing 11.6 GW of generating capacity (peak UK demand~60GW). Here is the list according to industry representative Energy UK (Figure 4). According to Wikipedia 6 of the 9 plants have already closed.
The average load factors for January 2013 are noted in figure 6. The average loads for coal and nuclear are both very high. The load for wind at 27.1% is actually very good. But the CCGT fleet was idling for 68% of the time. Figure 6 shows the distribution of load factors for January and shows for much of that month nuclear and coal were running between 80 and 100% and were actually running at capacity for some of the time.
Figure 6 This chart is tricky to explain. Using the data from Gridwatch and DECC it is possible to work out the load factor for generating plant every 5 minutes. That’s what I’ve done and then sorted the data according to load. The x-axis = 1 month of sorted data. The curves show the load distribution for the month. In January 2013, nuclear was basically running flat out; coal was running flat out for much of the time, the tail to the right reflects night time cycling down; wind performed well; the CCGT fleet was idling while the wind was blowing and LNG cargoes headed for Japan.
UK gas storage running on empty
Figure 7 shows that during April 2013, UK gas storage was effectively empty. National Grid in their Winter Outlook 2013/14 on p37 provide this explanation:
2012/13 – (1 in 4 cold winter) Further reductions in LNG, highest ever use of storage, and highest use of IUK since 2005/6.
National Grid also show some nice graphics showing the collapse in LNG imports with LNG cargoes chasing high prices in Japan. Imports via the Interconnector UK and storage compensating for the decline in LNG.
Figure 7 Chart from Rune Likvern at Norwegian energy blog Fractional Flow. The black line shows UK gas storage on the right hand scale, close to zero in April 2013. The columns show gas injection into storage and withdrawals from storage.
Gas being squeezed out
It is somewhat ironical that gas, which produces less CO2 per GWh than coal, is being squeezed out of the UK generating mix. With UK indigenous gas production in decline (Figures 8 and 9) there is an inevitability that we should transition away from this transient windfall from the North Sea. The Climate Change Act is also specifically designed to squeeze out fossil fuel power generation. And so government must also shoulder part of the blame for the inevitable demise of our legacy power system.
Figure 8 The history of UK primary energy production and consumption. The yawning gap that is opening up between production and consumption has resulted in the huge trade deficit shown in Figure 10.
Figure 9 This chart shows the decline of indigenous UK gas production (blue) replaced by imports (red and orange). Exports in recent years are effectively imported gas passing through the UK distribution system to destinations in Europe and Ireland. Gas is injected to storage during the summer and withdrawn during the winter.
With high gas prices, low plant utilisation and ever larger load balancing demands being made, it is little surprise that gas and electricity utilities are putting up prices. There is a very painful period of adjustment ahead for power companies and consumers.
Here are a couple of quotes from a European corporate presentation:
The massive erosion of wholesale prices caused by the growth of renewables constitutes a serious problem which may even threaten the company’s survival.
Large-scale investment programme has been devalued almost entirely by the upheaval in the energy market
Essential industries cannot go out of business, hence my presumption that nationalisation of parts of this sector may lie ahead.
Impact on trade balance
The focus of the UK energy debate should be on energy security, trade balance and affordable energy. Figure 10, provided by DECC, shows how energy surplus has swung into unsustainable energy deficit of over £22billion per annum. From January to April this year, the metered wind reported by Gridwatch produced 6.35 TWh of electricity. DECC provide more comprehensive figures that show actual wind production, that includes the vast number of small producers, was 8.07 TWh. This has displaced imported gas with significant benefit to the trade balance. An unofficial estimate on the value of deferred gas imports is of the order £295 million for jan-april 2013. With increasing wind on the grid, it is quite clear this saving could reach £1billion per annum in the near future. This calculation is subject to uncertainty and so if any readers would care to make a stab at this calculation in the comments section, that would be useful information to have. Most of the deferred liquefied natural gas imports have probably been combusted in Japan.
Figure 10 This chart, provided by DECC, shows the swing from £9 billion energy surplus to £21 billion energy deficit in only 12 years. To put this in context, the UK current account deficit for 2012 was £59.8 billion. About one third of this is down to spiralling energy imports. The government surely has a duty to manage this situation.
- The UK must do everything possible to increase indigenous primary energy production. The options include enhanced oil recovery in the North Sea, nuclear and renewables.
- At about 6% of current generation and growing fast, wind is making a meaningful though still small contribution. This offsets use of imported natural gas (or coal) that the country can ill afford to pay for.
- Wind is taking market share from gas and coal production. Gas and to a lesser extent coal are also being required to provide increasingly important balancing services to the grid. It is clearly not sustainable to ask one part of the generating sector to continuously do more for less.
- I object to wind farms springing up all over the countryside as much as the next person. To be honest I object to some a lot more than others. But a choice needs to be made between having electricity or a return to a subsistence society. If we want to have electricity then we have to put up with the infrastructure that generates it. Personally I quite like having hospitals and schools.
I am to be on holiday next week and so there will be no big post but I will be putting up some nice charts and maps. On my return I will be turning my attention to Energy Matters outside of the UK.