With no government subsidy, developing onshore wind farms in the UK has been a tough business over the last few years. Most of the “easy” sites close to grid connections or with few constraints have now been developed. So how can we continue to develop onshore wind in the UK?

Changing approaches

Yes, some big developers may be able to develop optimal sites from their balance sheets but what about the rest?  

Third-party power purchase agreements (PPAs) offer one promising option. If a large corporate like Google wants to power a data centre with wind, it arranges a PPA with the wind farm operator and the project could become bankable. This isn’t a subsidy – the corporate is paying a competitive market price – but it provides security for lenders through a fixed rate or floor price. The UK market awaits its first true third-party PPA with interest, to see if the approach lives up to its promise.

Whatever happens with PPAs, the industry can’t expect a return to its heyday. Developers are having to renegotiate land contracts that were signed when there were subsidies in the market and offer percentages to landowners that are no longer sustainable. The prices of engineering, procurement and construction contracts are being squeezed too. Contractors can’t expect the same profit margins they once enjoyed. Turbine manufacturers have already accepted this and now balance of plant contractors need to recognise reduces margins or wind farm projects won’t happen.

Thinking big is key

Scale is vital in the UK. By using larger rotors or higher hub heights, developers can get better energy density and capacity factors – lowering their costs per MW. Many are going back to planning to make their turbines as big as they possibly can. 

Ten years ago, the market was dominated by wind turbine generators with 90m rotors, such as the Vestas V90. Now diameters are considerably bigger. Compared to the Vestas V90 2MW, the Vestas V150 4.2MW has a 67% longer blade, a 178% increase in swept area and a 110% increase in rated power. This means that you can get more output from lower wind speed sites and can lead to high capacity factors on these lower wind speed sites.

Optimise – for the long term

In the UK, onshore wind is often limited by environmental constraints, particularly landscape and visual assessments. Many sites, particularly in Scotland, have issues with peat. Extracting peat down to the bedrock to provide a stable foundation for a wind turbine is expensive and environmentally damaging, so innovative approaches are required.

WSP is investigating how a unique foundation design we devised for the Canadian permafrost, which uses an innovative steel “spider” gravity foundation concept using a combination of precast concrete baskets and high strength steel beams siting on bored piles anchored to the bedrock, would work in UK peat. It has the potential to reduce concrete consumption, peat extraction and costs.

Another way to reduce the lifecycle cost of wind farms is to extend their lives beyond the standard 20 years. Data analysis of the designed, expected and actual loads experienced by the wind turbine generator could demonstrate that, with careful operation and maintenance, it’s possible for the project to last 25 or even 30 years. It’s vital to consider this in conjunction with longer-term planning and land agreements to safeguard the future of the wind farm.

Promising signs

From outside the industry, things may seem quiet but from inside the picture is different. Developers are looking to invest and acquire, with some purchasing sites from smaller developers who haven’t been able to build. 

With prices coming down, onshore wind is now competing to be the cheapest form of electricity in the UK – and it might just get there.

Kimberley Dewhirst is the technology lead for wind generation at WSP

Contact Kimberley

More on this subject