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UK Wind Power Becalmed

Dr John Constable: GWPF Energy Editor

Wind power output in the United Kingdom since the end of May has been at low and extremely low levels, confirming, yet again, the observation that wind power contributes little or nothing to security of supply, and so requires a duplication of resources implying a reduction in overall system productivity and so higher costs to consumers.

This is “Onshore Wind Week”, but Aeolus, the fickle god of the winds, has tested his celebrants’ resolve in the run-up to this festival  by refusing to blow more than the occasional puff at the United Kingdom’s 9,000 wind turbines (7,000 onshore, 1,800 offshore). In fact, output from the total wind capacity of approximately 16,500 MW has been low to negligible since the 30thof May.

Metered output is available from the Balancing Mechanism Reporting Service (BMRS) for about 11,836 MW or 65% of the wind fleet. The remaining 35%  is not visible to the system operator, but on the assumption that it performs as well as the visible capacity we can estimate the total output.

In the whole of May wind power visible in the BMRS generated 2.2 TWh of electrical energy, so the full total would have been approximately 3.4 TWh. The same calculation for the period 1–10th of June suggests a total wind generation of 0.31 TWh, implying a daily average amounting to less than 1/3 of that in the previous month.

In fairness one should note that June has historically often been a low wind month, but this year’s output does seem to be modest even by those historical standards. Indeed, for some hours on some days the fleet output was effectively zero. On the 3rdof June, for example, between 07.00 and 13.00, during the morning ramp, output from all 16,500 MW of UK wind power fell to some under 100 MW, a load factor of 0.6%. It must be remembered that this was not a matter of choice, but just what the winds had to offer at that moment. The following chart is the half-hourly fuel mix chart for that day, calculated from the Balancing Mechanism data by Dr Moroney at REF:

Figure 1: Half hour metered UK electricity fuel mix data for the 3rd June 2018. Vertical axis: Megwatts; horizontal axis, half-hourly Settlement Period.  Source: United Kingdom’s Balancing Mechanism Reporting Service, reprocessed and charted by Renewable Energy Foundation.

Gas fired power stations, represented by the dark yellow band, are obviously following load, and have thus filled in for absent wind, a fact that can be confirmed by noting that gas fuelled generation accounted for 45% of electricity in May, a level typical for the whole of the previous year, but have generated 51% of megawatt hours so far in June, a level rarely exceed in preceding months.

It should also be noted that load on the system is low, at just under 30 GW, so there is no question here of the operator struggling to get by. The system managed perfectly well, indeed it seems to run more smoothly and certainly more cheaply without wind. There have been, for example, no constraint payments to wind power since the 27thof May, when £105,000 was paid to wind farms to stop generating. In fact some £3.8 million was paid in this way over the whole month, with just under £1 million of it paid on the 26th of May alone. For two weeks the consumer has had a welcome holiday from these arguably unjustified costs. What better way to celebrate Onshore Wind Week.

So, this was no crisis, and if anything a rather desirable state of affairs, but nonetheless very instructive. We learn from the last two weeks, and in particular from the pattern of generation on the 3rdof June, that the output even of a very large distributed wind fleet, on- and offshore around the UK, occasionally falls to low levels for days on end, and sometimes to less than 1% of its potential output for several consecutive hours at a time. In effect the entire national wind fleet from North to South, from East to West, was becalmed. Clearly this could happen at any time, and thus, as experienced engineers have repeatedly indicated, a conservative system operator will prefer to have at hand sufficient conventional, controllable capacity, plus a margin, to meet any probable load on the electricity network. Wind simply cannot be relied upon. This multiplication of resources must result in the electricity supply system as a whole having a lower productivity than it would otherwise possess, which also implies, and in spite of the fuel saving that wind offers, higher costs to the consumer.