Renewable Energy Foundation

Constraint payments to wind farms, that is payments to stop generation, mostly in Scotland, reached record levels in 2018, with the total reaching £124,649,106, as compared to the total in 2017, of £108,247,860.

Of this, £115,716,335 was paid to Scottish wind farms, and nearly all of that, £115,313,091 went to onshore wind farms. These costs are, of course, passed through to consumers in their bills.

The new record data generated a number of stories in the press including the Sunday Times, the Times and the Scottish Daily Mail.

Of particular interest is that behind this record lies the fact that many wind farms received constraint payments for the first time in 2017 and 2018, as shown in the map below, including some such as Stronelairg that began to be constrained off (28 December 2018) within weeks of being connected to the system.

Figure 1: Newly constrained wind farms in 2017 (Green dots) and 2018 (Red dots)

There is a growing suspicion that the probability of major constraints is a factor in site selection, since it increases the average earnings per MWh generated as a result of the scale of compensatory constraint payments allowed, which are, and we think unjustifiably, well above lost income. Constraints can account for a substantial part of the potential output of a wind farm.

It is possible from market data to produce reasoned estimates of the fraction of output that is discarded. The following table lists the wind farms with the highest proportion of constrained off energy, which ranges from just below 30% to around 15%. These are high fractions, and, given that constraint payment compensation, which averages £70/MWh, is over 50% in excess of the lost income (£45/MWh) make a material difference to the annual income of the site.

These matters are not at present adequately addressed in the planning system, but clearly should be. Decisions makers should be aware that a site may have been chosen precisely because it lies behind a constraint, and in spite of other material considerations, such as local environmental impacts.

Table 1. Estimated proportion of total generation in 2018 that received payments through the Balancing Mechanism not to be generated. For example, Bhlaraidh generated approximately 192 GWh in 2018 and a further 80 GWh was constrained resulting in the 29% figure in Table 1.