On Tuesday 6 December, UK Prime Minister Rishi Sunak and Business Secretary Grant Shapps reached a much-anticipated deal overturning the effective ban on new onshore wind projects. Onshore wind has been a political football in the UK since 2015, when David Cameron introduced strict planning restrictions on onshore wind development in the government’s National Planning Policy Framework (NPPF), amounting to an effective ban. Under the rules, councils can only grant permission for a new wind farm if it meets two requirements: first, it must be located somewhere identified as suitable, and second, it must have backing from locals

The effect of the restrictions has been to stunt the growth of new onshore wind farms, with the number of planning applications put forward in England dropping sharply in 2015. 

In 2021, the UK’s Climate Change Committee advised the government to install 35GW of onshore wind by 2035 as a key step to reaching net zero. However, so far, the UK has been giving consent to less than half the annual capacity needed to reach that goal. 

As such, many were buoyant in response to this week’s news of an end to the effective ban on onshore wind. Vattenfall's head of UK onshore development, Frank Elsworth, said in a statement: "If this is a genuine move which will put onshore wind on a level playing field with other infrastructure in England, it will send a very positive signal that the government is serious about harnessing the benefits which onshore development can unleash for the environment, the economy and communities.”

Repowering onshore wind

A less-discussed aspect of the government’s announcement of a consultation on onshore wind development is what it means for repowering existing wind farms

In the UK, most onshore wind and solar farms are granted a time-limited planning consent of 25 years, which roughly corresponds to the end of their operational life. According to 2021 research by Rebecca Windemer from the University of the West of England, 654 UK wind turbines, or 10% of the total, are more than 20 years old, and the number is growing rapidly. 

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When a wind farm reaches the end of its life, there are three options: it can be decommissioned, where all infrastructure from the site is removed; its life can be extended beyond the duration of the existing planning consent (usually for five to ten years); or it can be repowered, where existing equipment is replaced by new equipment with a higher energy output. In order to repower, wind farms must have a fresh planning application approved. 

Developers may find there is more economic incentive to extend the life of an existing project than repower, thanks to subsidies. For example, many existing wind farms currently benefit from the UK’s renewables obligation certificates (ROC) scheme, which issues certificates to renewable electricity providers for each megawatt-hour of electricity produced, which can then be sold on to other parties. The scheme was scrapped in 2017, but existing projects can receive ROCs until 2027, meaning developers may consider it more economic to extend the life of an existing project than repower with new turbines that have no subsidy. When these subsidies run out in 2027, it is expected that more developers will turn to repowering. 

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Another sign the UK government is looking more favourably upon onshore wind is an end to its previous exclusion from the UK’s Contracts for Difference (CfD) scheme, which guarantees a generator revenues at a pre-agreed level (strike price) for a certain length of time.

In line with other restrictive policies, onshore wind was excluded from this scheme from 2017 until last year, a change which James Robottom, head of onshore wind at industry body RenewableUK, says was a “big step” forward. Robottom also notes that repowering projects were included in the last CfD round, which is “good because repowering projects can get a consistent price... which is what we want”. 

In further positive news for the industry, the government’s consultation on local support for onshore wind, published on 6 December, says it will “encourage the upgrading of existing wind farm sites”, which suggests a step towards formal guidance on repowering. Robottom says further guidance is crucial: “New sites would be great; repowering is essential.” Although restrictions on new wind farms have dominated political debates, he argues that the more pressing issue is that the UK risks losing existing capacity.

“The number of viable onshore wind sites in the UK is substantial but finite," Robottom told Energy Monitor. "Effective repowering is a vital part of making the most efficient use of the available onshore wind and land resources and would complement the new sites that will also be needed.” 

According to RenewableUK, in the next ten years, around 2GW of the current 14.2GW of installed onshore wind capacity in the UK will reach the typical 25-year consent time. By 2042, 12.3GW will reach the same milestone. 

The industry recommends that the UK aims for a target of 30GW og onshore wind capacity by 2030 in order to meet the UK’s net zero by 2050 target. Repowering would play a significant part in that: in an earlier analysis that foresaw 26GW of onshore wind in 2030, more than half (or around 20GW) of the 36GW expected by 2050 would have come from repowering.

Improved efficiency 

One of the reasons repowering is so important is that it will improve the efficiency of existing wind farms. "[Repowering] often involves replacing existing turbines with a smaller number of larger, more efficient turbines in a different layout,” Windemer explains. According to her research, repowering has decreased the number of turbines on a site by 41% on average, while increasing the height of turbines by 98.8%.

The average increase in installed capacity in a repowered onshore wind farm in megawatts (MW) is 143%. For example, the Ovenden Moor wind farm in West Yorkshire, which, in 1993, had 23 turbines that could produce 9MW of energy, was repowered in 2017 with just nine turbines that had 18MW of capacity. This amounts to 100% more capacity with 60.9% fewer turbines, making it a “good example of a really effective, efficient repowering”, says Windemer. 

Missing guidance on onshore wind repowering

Yet there are few government guidelines on repowering. Historic applications have tended to be successful – as of July 2021, 18 out of 23 wind farms applying to repower were granted permission. However, most of these decisions were made before Cameron's planning restrictions. The current NPPF 'exempts' repowering applications from the double requirement of being located somewhere identified as suitable and requiring backing from locals, but wind farms looking to fully repower or extend their lives beyond any end date originally set out still have to make a fresh application and undergo an environmental impact assessment.

With no formal guidance on how local authorities should deal with repowering projects, it remains unclear how far the restrictions on existing projects affect repowering applications, says Windemer.

The only other mention of repowering in UK government policy comes in a 2011 publication, the National Policy Document for Renewable Infrastructure, which states that repowering applications should “be determined on their individual merits”. 

In Scotland, the situation is different. Since 2017, policy has determined that areas identified for wind farms should be suitable for use “in perpetuity”.

RenewableUK wants the NPPF’s wording on repowering to be clarified. “[There] will need to be grown-up conversations at some point around making sure that repowering uses the most efficient and appropriate turbines for that site,” Robottom says. The government’s overturning of the effective ban on new onshore wind may offer a chance for those conversations to take place.

Community consent remains an issue 

A lack of community consent has on at least one occasion prevented a repowering application. The Chelker Reservoir wind farm in England had its application for repowering rejected twice, first in 2008 and again in 2011, for reasons including the visual impact on the historic landscape and its impact on nearby residents.

In a new paper published in the first week of December 2022, Windemer argues that research on community experiences of living near wind farms is undeveloped, despite being crucial to ensure applications for repowering get community support. People must have a positive experience of living near wind farms to support repowering applications, Windemer concludes.

She offers developers a number of recommendations, including providing local residents with some financial benefit, maintaining consistent communication and ensuring locals are fully involved in all repowering decisions. 

Building on these recommendations could be crucial to ensuring repowering decisions are not blocked and the UK has a chance of reaching its net-zero target. 

This article originally appeared on Energy Monitor.