However, the lesson is reasonably clear Britain and Germany’s aggregate wind farm output can be expected to go below 1% of total installed capacity with reasonable regularity. Britain installed some new capacity between June and September. The minimum was therefore only 0.4% of the maximum.
Its output reached a minimum of 0.025 GW at 11 pm on the 16th of June. However, it also sees periods of close to zero wind.īritain’s total wind farm output peaked at 6 GW at midnight on the 21st of December. Overall, Britain has a much better wind regime than Germany, with higher average wind speeds and fewer lulls. Not quite zero, but not much higher either. Minimum power output was therefore only 0.5% of maximum power output. In contrast, minimum power output of Germany’s wind farms was 0.128 GW at 2 pm on the 4th of September. Last year the power output of Germany’s wind farms peaked at 26 GW at 6 pm on the 5th of December (see technical note for details of calculations). How much does wind farm output vary in these countries? Let’s look at Germany first. (Britain’s government publishes annual figures here.) Recent production data in Germany and Britain indicate that these are still reasonable estimates. In other words 10 GW (GW = billion watts) of installed capacity in Britain will deliver about 2.6 GW on average, but the figure will be 1.8 GW in Germany. In 2009, Boccard estimated that the average capacity factor of Germany’s wind farms was 18.3%, while in Britain it was 26.1%. Wind farms can reliably supply less than 1% of installed capacityīritain is perhaps the windiest country in Europe while Germany is more or less the least windy. I will illustrate this for Britain and Germany. How much the aggregate output of countries’ wind farms varies can be discovered by looking through spreadsheets produced by grid operators And the lesson is clear: In every country aggregate wind farm output often goes close to zero. If you are comforted by the claim that “if it is not windy in one place, it will be windy elsewhere”, I suggest you watch a weather forecast. the whole of Britain, are closely linked. The same cannot be said for wind farms.Īnyone who regularly watches weather forecasts knows that wind speeds over large areas, e.g. I live in Scotland, and the probability of Longannett power station – a short drive from where I live – going off-line at exactly the same time as Drax power station – a 3 hour train journey away – is close to zero. In this sense, all power plants are backed up by each other.Ĭoal power plant outages, however, are always independent of each other. When a power plant does goes off-line, others will respond by changing their output. A century of technical innovation has resulted in electricity grids that are ultra-reliable by any reasonable standard, but power plants still cut off on occasion they are vastly complex industrial machines and things will sometimes go wrong. Let me begin by unpacking a banal statement: All power plants need back up. In this sense, every wind farm must have a fossil fuel power plant sitting in wait for when the wind does not blow. In fact, on the scale of most countries aggregate wind farm output can be assumed to have almost zero reliability. Wind farms, however, cannot currently provide this reliability. On aggregate, these power plants can be relied on to supply electricity around the clock a reliability that would seem miraculous to people living only a few centuries ago when light availability was completely dependent on whether the sun shone. This electricity comes almost entirely from burning coal and natural gas, fissioning uranium or by large hydro-electric dams. Modern society is fundamentally dependent on a reliable and on-demand supply of electricity.
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