The offshore wind industry is starting to consider end-of-life options for the oldest turbines
A wind turbine being taken down in Lelystad, the Netherlands. As more and larger turbines are built offshore, the problem of future decommissioning looms larger (Image: Tromp Willem van Urk / Alamy)
Wind farms built out at sea are experiencing a construction boom.
Global capacity of offshore wind is expected to grow from 81 gigawatts (GW) at the end of 2024 to around 250 GW by 2030 – with 120 GW of this in China. Europe’s 37 GW capacity could more than double to 84 GW by 2030.
Wind turbines are becoming taller and more powerful, with some offshore varieties now generating enough electricity to power about 20,000 European homes each.
But as it puts up these mammoth structures, the wind industry is also starting to think about how to take down the older turbines, many of which are now nearing the end of their operational life, typically 25 years.
Decommissioning turbines on land is a well-established business, with a total of around 2 GW set to have been removed in Europe by the end of this year, according to data shared with Dialogue Earth by trade body WindEurope. Offshore it is a different story.
Just a handful of turbines have been taken out of the sea to date, including the world’s first offshore wind farm in the Danish Baltic Sea, built in 1991. WindEurope expects the total removed to have only reached 6 MW by the end of this year. As the most mature location for offshore wind globally, with 37 GW now installed, Europe will provide the testbed for decommissioning. WindEurope forecasts that 29 MW of turbine capacity is in the pipeline to be removed by 2030.
Repower or remove?
Some wind farms could have their lifetimes extended by refitting ageing components or turbine blades. Others may be “repowered”, meaning all their turbines and grid connections are replaced. But there is likely to be limited scope for repowering because turbines installed at sea decades ago have relatively small foundations. New turbines small enough to fit on these old foundations would be unlikely to be available, explains Christoph Zipf, WindEurope’s spokesperson.
WindEurope expects just 33 MW of offshore turbines to be repowered by 2030, according to data shared with Dialogue Earth.
Another issue with keeping offshore wind farms in place is that in many countries, the seabed on which turbines are installed is leased from government authorities: systems for extending these leases do not yet exist.
The sector is currently assessing the pros and cons of decommissioning versus refitting versus repowering. A 2023 assessment carried out by the Crown Estate, which manages seabed leases in much of the UK, found that completely new build offshore wind farms would add the most green electricity generation. Repowering existing farms would be best for economic value and jobs, while extending the lifetime of existing wind farms would be best for marine habitats and lower use of raw materials, it concluded.
Current leases last 50 years, and as yet, no offshore wind developer has applied to extend a lease, according to a spokesperson for the Crown Estate. When this happens, a decision would need to take into account environmental impact, consent from authorities and competition with other wind companies, he says.
Complete removal?
Fixed offshore turbines can use concrete or metal foundations, while floating designs involve large seafloor moorings involving the same materials. If turbines are to be removed, a major debate currently underway is whether they should be taken out foundations and all. An alternative is to leave two to three metres of foundation below the seabed.
“There have been quite large ecosystems that have built up around these structures over the past 20 years, and by disturbing those, you’re potentially doing more harm than good,” says Matthew Geraghty, CEO of ReWind, a DNV company.
He cites a 2020 study by the Technical University of Denmark (DTU). It found that rock-like material applied to the base of the turbine to prevent water erosion provides habitat for biodiversity.
DTU has installed artificial reefs made out of the same material to benefit marine wildlife in other parts of Denmark. “Why would you take it out of the water if you’re putting it back in elsewhere?” Geraghty says.
The legal landscape on the removal question is fragmented. Full removal is favoured by international law under the United Nations Convention on the Law of the Sea (Unclos) and the Convention for the Protection of the Marine Environment of the North-East Atlantic (Ospar).
Most national laws in countries with offshore wind, such as the UK, Denmark, Germany, the Netherlands and Belgium, stipulate full removal. Only France so far allows partial removal.
It is not possible to recommend a blanket approach.
- Calum Duncan, head of policy and advocacy at UK-based NGO the Marine Conservation Society
WindEurope wants the European Commission, which proposes pan-EU legislation, to develop an approach across the whole 27-country bloc that allows for some infrastructure to remain. This could happen where there is evidence it would not only protect biodiversity, by avoiding disturbance during removal of the complete structure, but actively enhance biodiversity in future, it says.
Offshore Renewable Energy Catapult, a UK-based innovation organisation, has recently reviewed the evidence of the impacts of full and partial removal. “We don’t have enough evidence around the artificial reef argument, for example, does it present other environmental concerns around degradation of the metal over years? There‘s not enough data to prove either case,” says Lorna Bennet, the organisation’s project engineer.
Conservation campaigners are cautious. Calum Duncan, head of policy and advocacy at UK-based NGO the Marine Conservation Society, said that for any type of decommissioning, it was preferable for the marine environment be left as it was before development had taken place. On some occasions there might be environmental benefits to leaving structures in place, he acknowledged.
“This decision would have to be made on a case-by-case basis and depend on a number of factors, including the habitat on which the structures are built, the materials they are made of, and the cost/benefit analysis of removing the structures compared to keeping them in place,” he says. “It is not possible to recommend a blanket approach.”
Helena Rodrigues, ocean policy officer at WWF-EU is wary of the wind industry’s claims about artificial reefs. “While the energy transition is essential, we must ensure that the impact of offshore wind projects is properly managed,” she says. “Simply leaving infrastructure behind does not automatically benefit marine ecosystems. We must focus on minimising harm and ensuring that any positive effects are scientifically validated over time.”
A circular approach
Another big environmental question facing industry is how to reuse or recycle materials and components from the coming wave of obsolete offshore wind farms.
While 85-95% of a turbine can be recycled, according to Danish manufacturer Ørsted, the blades remain a challenge. They are made of various materials, typically a balsa or foam core surrounded by layers of fibreglass or carbon fibre. This mixed makeup makes them very hard to break down for recycling.
Many manufacturers have been researching how to design blades for recyclability. Ørsted and Northern Irish company Plaswire have partnered to develop a method that involves shredding and granulating blades. They can then be turned into a polymer for the construction industry. Siemens, meanwhile, has developed a new type of resin which it claims makes its blades recyclable.
According to Zipf, all the main blade manufacturers have made commitments to recycle blades or to have zero-waste blades by the 2030s or 2040s. “As these blades become bigger, there’s a lot of valuable material in there, and it just makes sense to use them in a circular manner,” he says.
For Geraghty, recyclable blades are still quite far from being commercially viable, and in any case are not the main obstacle to making offshore wind circular. “Manufacturers’ biggest focus right now is using green steel for new turbines – it’s very hard to get enough,” he says.
The whole supply chain needs to be considered to enable circularity of green steel, according to Bennet. For example, in the UK, though steel manufacturers are able to recycle the metal domestically, there are currently no domestic facilities for manufacturing turbine towers or foundations. The recycled steel would have to be shipped to Europe, and the manufactured towers shipped back again.
To encourage the sector to design turbines and components with decommissioning and reuse in mind, WindEurope wants governments to introduce questions about how wind farm infrastructure has been designed to allow for reuse or recycling during the permitting or auction process.
Geraghty says the sector has a strong motivation to design turbines with decommissioning and reuse in mind to shift from the current huge reliance on China for many materials. “There’s a strong desire to build up supply chains within Europe,” he says.
When it comes to dealing with ageing offshore wind farms, where Europe is going now, other countries will have to follow.
China’s decommissioning challenges
China’s offshore wind industry has rapidly developed into the largest in the world and is on a similar trajectory to Europe’s.
Wind turbine blades at a manufacturing site in Binzhou, east China. Blades are among the hardest parts of wind farms to recycle (Image: Cynthia Lee / Alamy)
The nation’s older wind farms, which are on land, will experience a first peak of decommissioning this year, with over 1.2 GW of turbines expected to be retired. The decommissioning of offshore turbines will be further down the line, as it was not until 2010 that China’s first offshore windfarm was connected to the grid.
With offshore decommissioning only on the horizon, both policy and the recycling market are in their infancy.
In June 2023, the National Energy Administration issued rules for upgrading and decommissioning onshore wind farms but there are currently no rules for their offshore counterparts. Recognising the mass retirement of turbines that China will soon face, the national government issued a directive in August 2023. It commanded various bodies to build up regulations on wind-farm decommissioning and support research and development on recycling of both land and offshore sites.
Like its European counterpart, China’s wind-turbine industry faces the hurdle of recycling the huge blades from defunct farms. Over 90% of the decommissioned blades are thought to end up in landfill or be burned. Chinese private wind-turbine makers have begun rolling out blades which will be easier to recycle. They can be melted and separated into their original components under a chemical process, allowing the materials to be recycled.
The questions Europe is trying to answer now on decommissioning offshore wind will be asked with increasing urgency by China, and other countries, soon.
- This article was originally published on Dialogue Earth under the Creative Commons BY NC ND licence. Read the original article.
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