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REF Blog

A Decade of Constraint Payments

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.


Gordonbush Wind Farm Extension: Environmental and Economic Downsides

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.


Constraint Payments to Hornsea Offshore Wind

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.


Western Link Outages Increase Consumer Costs for Scottish Wind Farms

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.


RPI Inflation Index Provides Multi-Billion Subsidy Windfall for Renewables

Dr Mark Carney, Governor of the Bank of England, has recently called for government to cease using to the widely discredited Retail Prices Index (RPI), for example when index-linking to offset inflation. This follows a recent House of Lords report on the indices used to measure consumer price inflation which drew attention to the fact that due to an error in the methodology used by the UK Statistics Authority (UKSA) the RPI is greater than the Consumer Prices Index (CPI), with the difference tending to increase (see Figure 1).

As the House of Lords report states, this error has created both winners and losers. Examples of losers include students and commuters whose loans and rail-fares are linked to the higher and more rapidly increasing RPI. Amongst the winners are holders of RPI-linked gilts and also, recipients of renewable energy subsidies under the Renewables Obligation (RO), the Feed-in-Tariff (FiT) and early adopters of the Renewable Heat Incentive (RHI). Since the RPI is used to calculate the inflation proofing of these subsidies there is now significant and unjustifiable over-support, with the scale of the problem being particularly significant in the largest of the schemes, the Renewables Obligation.


The Co-location of Battery Storage and Fossil Fuelled Generators in the United Kingdom

It is a commonplace that the uncontrollable variability of the most prominent modern renewables, solar and wind power, requires electricity storage to make them viable as free-standing and independent technologies. Consequently, batteries and other storage systems are sometimes presented as the key to the problem of intermittency, storing green energy at times of surplus for those times of dearth when the wind isn’t blowing or the sun shining, and so unlocking the wholly renewable future. Batteries are now on the verge of broad deployment in the UK, but they do not appear to be taking up the function expected of them, and instead seem to be gravitating towards close working with conventional generation.


Paying Wind Farms to Stop Generating in 2018

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.


High Wind Farm Constraints Continue in Spite of WesternLink Interconnector

The long overdue commissioning of the WesternLink Anglo-Scottish subsea interconnector, completed earlier this month, appears to be mitigating the need to constrain off Scottish wind power, but the delay in the cable’s delivery has meant that it has been overtaken by overall growth in wind on the network, and constraint payments continue, with over £2m being paid out to forty wind farms yesterday, the 23rd of October 2018, with an average price of £69/MWh, well above the lost income of £45/MWh.

Nevertheless, the WesternLink does appear to be facilitating very high, record-breaking levels of wind on GB’s electricity system. For example about 11 GW of wind was carried over a single settlement period (SP 41 which covers the period 8:00- 8:30 PM) on the 23rd of October 2018. This can be seen clearly in the two figures below, generated from REF’s free, online fuel mix database, which is based on Nationall Grid data.  The first panel shows the total fuel mix, and the second panel the renewables and interconnectors alone.


UK Wind Constraint Payments Reach New and Exceptional Levels

Constraint payments to wind power are hitting new records on a regular basis. The highest daily total, £4.77m occurred on the 8th of October 2018, and the highest monthly total of £28.4m in September 2018, a staggering £5m more than the previous record of £23.2m in October 2017. The annual record, set last year, of £108m looks almost certain to be broken this year, where the total is already £101.5m to the 19th of October 2018.

Constraint payments to wind power, mostly but not now entirely in Scotland, comprise a staggering 8% of the cost recovered through the Balancing Services Use of System (BSUoS) charges, with a very substantial proportion of the remainder being caused by wind constraints that require conventional generation to be constrained on to the system south of the constraint to make up for the absence of contracted wind.


Record UK Wind Farm Constraint Payments of £28m for September 2018

September 2018 has seen the highest monthly payments to wind farms to stop generating since records began in 2010.


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