Renewable Energy Foundation

REF will shortly publish major new analysis by Professor Gordon Hughes, under the title Wind Power Economics: Rhetoric and Reality.

The study contains two volumes, one on the Performance of Wind Power in Denmark and the other on Wind Power Costs in the United Kingdom.

On the basis of a large and detailed statistical analysis of audited accounts and other performance data Professor Hughes shows that far from falling dramatically, capital costs for wind power have come down only slightly, and that Operation and Maintenance (O&M) costs required to maintain energy yields are actually rising sharply, throwing the medium and longer term economics of the entire enterprise into jeopardy.

The study will be published shortly with a webinar, and anyone interested in being added to the mailing list for that announcement should write to us at REF at This e-mail address is being protected from spambots. You need JavaScript enabled to view it

In the course of preparing this work and discussing it widely with colleagues we have become aware that the findings are surprising to many, particularly to some industry players who enjoy special circumstances unrepresentative of the overall wind sector.

An example of these special circumstances may make the point clear. Northern Ireland has several hundred small (< 250 kW) and apparently old turbines that are still making money. Some might say, and indeed REF has heard it said, that the empirical experience of these wind turbine operators should count for more than statistics, even if the statistical analysis is based on real cost data from audited accounts and authoritative records of real generation such as that behind Professor Hughes’s study.

While speciously persuasive this proves to be a good example of how dangerous it is to rely on limited, personal or anecdotal information when forming a general view. Uncle Wilfred may indeed have lived to a hundred on a diet of cigars and whiskey, but that is no recommendation for the rest of us. By the same token, closer examination of the situation in Northern Ireland shows it is no guide to the rest of the sector.

A series of unwelcome records were broken over the Bank Holiday weekend period, from Friday the 22nd to Sunday the 24th of May, 2020.

(i) Constraint payments made to wind power to reduce output within the Balancing Mechanism were £9.3 million - the highest ever paid for any three-day period (Sunday Telegraph “Wind Farms Paid Record £9.3m to Switch off their Turbines”).
(ii) System electricity prices dropped below zero for long periods with a record average price of -£17 per MWh being recorded on the 22nd.
(iii) Intermittent day-ahead prices used to calculate CfD subsidies averaged -£10 per MWh on the 23rd, the first time the average for an entire day has been negative.

The cost to the consumer of balancing electricity over this chaotic weekend is in excess of £50 million (The Times “National Grid pays out £50 million to turn power down as lockdown hits demand” .

There have been no constraint payments to Scottish wind power in the UK’s Balancing Mechanism (BM) since the 21st of April and up to the date of writing (7th of May). This is welcome after a very expensive start to the year when consumers paid £95 million to discard Scottish wind output from the 1st of January to the 21st of April..

But the reduction in constraints is not the result of improved balancing techniques or the return to service of the hitherto troubled Western Link interconnector. Rather, it is the result of low wind generation in Scotland reducing congestion within the country and over the links to England. Consequently exports to England have been declining for some weeks.

The cost of excess wind power in the first two months of 2020 amounted to £72 million in payments to wind farms to reduce output, mostly (£69 million) in Scotland. Last year’s annual total of £139 million was a record, but does not seem likely to remain so for long.

Comparing payments in January and February for all years back to 2012 we find that the total for those months in 2020 is nearly four times that in the next most expensive year, as shown in the following chart.

When there is a collision between different government policies with the same purpose the result is sure to be messy, and the chances are that the benefits arising from both policies will be compromised and perhaps lost altogether. The Scottish Government, for example, aims to reduce carbon dioxide emissions through the enhancement of carbon sinks, such as forestry and peat, while also encouraging the generation of electricity from industrial wind power. Since both projects are land hungry and the United Kingdom’s geographical area is finite or even diminishing, it is highly unlikely that targets for forestry and peatlands, on the one hand, and renewables on the other can be simultaneously approximated, let alone met and maximised.

Last weekend the Italian cable manufacturing company, Prysmian, released a statement announcing to the markets that the Western Link High Voltage Direct Current (HVDC) interconnector between Hunterston and Deeside had failed again, on the 10th of January. This grid link, which is a joint venture between Scottish Power Transmission (SPT) and National Grid (NG), employs cables manufactured by Prysmian.

This £1 billion project has a peak transit capacity of 2.25 GW and was designed solely to facilitate the export of Scottish wind power to the English and Welsh markets. In doing so it was expected to reduce constraint payments to wind power, payments which amount to £630m since 2010, with a record £130 million in 2019 alone.

The project was expected to come online at the end of 2015 but in fact did not become fully operational until late 2018 and has been plagued with faults ever since.

2019 was the tenth year in which British wind farms have received constraint payments to reduce their output because of electricity grid congestion. There has been a total of £649 million paid out over the decade for discarding 8.7 TWh of electricity. To put this in context, this quantity of energy would be sufficient to provide 90% of all Scottish households with electricity for a year.

Because of a rapid growth in wind farms, particularly in Scotland, the total paid has tended to increase year on year in spite of grid reinforcements and new grid lines such as the £1 billion Western Link from Hunterston to Deeside, which was built specifically to export wind power from Scotland to English and Welsh consumers. Figure 1. displays this trend, showing payments rising from £174,000 in 2010 to a new record cost of more than £139 million. The quantity of electricity discarded in 2019 was also a new record at 1.9 TWh.

The Scottish Government has recently approved increases in turbine heights – now set to reach 150 metres (490 feet) to blade tip – at the extension to the Gordonbush wind farm in the far north of Scotland, near Brora in Sutherland. The approval brings many significant public interest questions into the spotlight.

Introduction: Inertia and Frequency
There is much talk about the importance of "energy storage" to enable the adoption of renewables. It is often forgotten in such discussions that the conventional electricity system, of fossil fuelled and nuclear power stations, already has a large storage component built into it. This energy store is found in the rotating mass of the turbine shafts in the generators, and also, to a lesser extent, in the rotating mass of the large electric motors used by some electricity consumers. The rate at which the shafts of those generators, and synchronised motors, are turning is determined by the chosen electricity System Frequency, which in the UK is 50 Hz, or 50 revolutions a second, 3,000 rpm. In almost exactly the same way that a gyroscope has stability and resists attempts to move it due to the energy stored as kinetic energy in its rapidly turning wheel, the synchronised rotations of the electricity generators deliver system "inertia" making it robust against accidents and other surprises, for example an unforecast increase in electricity demand, a grid line failure or the loss of one or more power stations. The energy stored in the spinning mass of the turbines can be drawn down very briefly to buffer the shock and allow time for other generators to increase their output to address the shortfall. In that event, the frequency of the system falls as all the generators slow down due to loss of energy.

Unfortunately, not all generators are capable of operating in this synchronised fashion, and these generators do not contribute to inertia. Solar photovoltaics, for example, have no rotating parts, and wind turbines do not have sufficient mass in their generator shafts to contribute significantly to inertia. Consequently, these generators operate asynchronously, as do the electricity interconnectors with the networks of other countries.

As the proportion of renewable generation and the increased reliance on interconnectors has grown in the UK, the average inertia of the system at any moment has declined, meaning that the system would be less resilient in the face of an accident unless compensating measures were taken, for example the addition of asynchronous compensators (effectively flywheels), generation capable of a very rapid response, such as pumped storage hydropower, or other energy storage devices such as batteries.

It has been assumed hitherto that the UK System Operator, National Grid ESO, was taking adequate steps to ensure that declining inertia was not a threat. However, the load shedding causing local blackouts over the United Kingdom on the afternoon of the 9th of August this year, has put National Grid's management of the system under the spotlight, raising many questions.

REF wind farm constraint payment data was used on 12th of April 2019, in a Financial Times report on the most recent fault and outage at the new Western Link interconnector. In this post we explore some of the implications of the outage and offer some comments on its probable causes.

A renewable electricity policy based on wind and solar is a grid expansion policy; you can’t have a large fleet of uncontrollably fluctuating renewables in distributed and often remote locations without a cat's cradle of network to connect them and facilitate inter-regional and international exports and imports necessary as part of the demanding system balancing measures required of the System Operator. This fundamental association between wind turbines and wires has been clear for well over a decade, certainly since the now classic warnings of the Eon-Netz wind reports of 2004 and 2005.

But cables, whether subsea, underground, or in the air, are expensive, and add significantly to consumer costs. The Western Link interconnector, 2.25 GW High Voltage Direct Current cable consisting of 385km of subsea cable and 33km of onshore cabling, running from Hunterston in Scotland to Deeside in Wales, required a capital expenditure of somewhat over £1 billion.