Wind power is big business, and is under pressure to reduce costs and carbon footprint. This can be done by proactively looking after the most valuable turbine components, with solutions that seek to repair and extend the lifespan of these parts and avoid long-distance, carbon-intensive and expensive transport.

On one day in November 2022, more than 20.896GW (70%) of the UK’s electricity was produced by wind, and that record was broken shortly after on December 30 when 20.918GW (87.2%) was generated by UK based wind turbines. Britain produced a record amount of wind power in 2022, the National Grid revealed on 6 January.

Wind produces on average over 25% of the United Kingdom’s energy needs annually and there are now more than 11,000 wind turbines onshore and offshore with an installed capacity of over 25 gigawatts. And this capacity is set to boom further, driven by energy security concerns and the cost of natural gas.

The UK Energy Security Strategy 2022 has set a goal of 95% low carbon power by 2030. To meet the 6th Carbon Budget, we will need a fully decarbonised power system by 2035. To achieve this the Government intends to quadruple offshore wind capacity to 50GW and the renewable energy industry also believes onshore wind capacity needs to increase to 30GW by 2030.

This rapid expansion of wind energy in the UK means more wind turbine manufacture, installation, operation, repair, refurbishment and replacement. A growing number of MPs have come out in favour of a reversal of the restrictions on new onshore wind farms, and according to the Offshore Wind Industry Council approximately £155bn of private sector investment is expected in offshore wind by 2030.

The expected life span of a commercial wind turbine is 20-25 years (source: Wind Europe) and the unit will need continual repair and maintenance during that period. The “workhorse” component in a wind turbine is the generator. During a turbine’s lifespan, the generator will require repair and maintenance and will quite often be replaced as it deteriorates due to age. Costs, logistics, lead times, manufacture and repair capacity, workforce and skills are all factors in achieving this replacement quickly and efficiently.

With a large proportion of existing turbines reaching the end of their OEM warranty periods, evidence from industry research points to the economic advantages of generator refurbishment, as the manufacturing and transportation of a full replacement has very high environmental as well as financial costs. Plus, the recyclability of wind turbines is under close scrutiny today – with the covid pandemic over, the Russia-Ukraine War in a period of stasis, and COP27 taking place, climate change is again top of the news agenda. ETIP Wind calculates that wind turbines are 85%-90% recyclable on average, with components like the gearbox, generator, foundation structure and tower all recyclable. Manufacturer Vestas cites that 83% of a turbine’s carbon footprint comes from the production of materials, while just 17% comes from transport.

Research by organisations including manufacturers and the UK’s Offshore Renewable Energy (ORE) Catapult say that electromechanical refurbishment is important to minimise wind’s own carbon footprint. Vestas states that a refurbished component can reuse up to 70% of the materials compared to a new product, and a refurbished component saves, on average, 45% of CO2 emissions compared to a new part, when reverse logistics – the cost of bringing the item from the turbine to the factory for repairs – is accounted for.

More stakeholders are pressing the case for a circular economy in renewable energy, especially wind power. The ORE Catapult, a private-public innovation centre, estimates that by 2050 the global wind industry will need to decommission as much as 85GW of offshore wind capacity and 1,200GW of onshore wind capacity. This provides an idea of the scale of the circular economy opportunity.

“Refurbishing of wind turbine generators has enormous, and largely untapped, potential,” says Chris Robson, Sales Director at Houghton International, an electromechanical engineering company.

“If the UK is to be “clean energy sourced” by 2035, we’ll need to construct thousands of new wind turbines while keeping the current capacity running. Many turbines are already exceeding their intended service life – so long as they’re maintained correctly. Rewinding and refurbishing a generator can extend its life by 20-years, and this will relieve some pressure on the new build programme.”

Grannell Community Energy Ltd – turning point

Houghton International is a service and repair company of electromechanical machines – generators, motors, transformers and pumps. Throughout its 38-year life, Houghton International (HI) has maintained, repaired and refurbished a very wide spectrum of these electromechanical assets but, while it had worked on ad hoc wind turbine generator maintenance, through the 2000s and 2010s the wind industry has been broadly reliant on OEM replacement or refurbishment.

In early 2020 Grannell Community Energy (GCE), a locally-funded Community Benefit Society, contacted Second Wind Energy LTD with a problem. The group had bought and installed a second-hand 480V / 800KW Enercon wind turbine, but the generator had failed after just one year in service. Second Wind Energy specialises in sourcing new and used turbines for customers, installing them and providing maintenance, and it also removes generators and turbine assets for repair.

GCE’s commercial scale wind turbine has a 4.2m diameter, 26-tonne generator located on a steel 50m tower. HI was the only UK based company that Second Wind Energy were satisfied could handle the full refurbishment of the damaged generator, and they responded quickly and positively, offering a competitively priced full rewind of the unit. The majority of wind generators operate through a gearbox so the much larger, direct drive generator was far less familiar to the team within HI, but their vast, multi-sector generator experience has given rise to a flexible, problem-solving approach. GCE’s generator was transported to HI’s Newcastle-upon-Tyne base, one of the only facilities in the UK that could accommodate such a big rotating machine. The project that unfolded proved to the customer, the wind turbine industry and HI there is a truly environmentally-conscious, effective solution for rewinding and extending the life of wind turbine generators here in the UK.

After assessing the damage, HI recommended a full rewind of the stator and rotor. Over 50 miles of copper wire, uprated to help ensure a long lifespan, was used in the rewind of the generator. The existing copper was stripped out and recycled. All 60 rotor bricks were reverse engineered and rewound using a process developed by HI that had been proven for decades on high-speed train alternators. The rotor bricks were put through a vacuum pressure impregnation process to seal them in a strong resin that is highly weather resistant and strengthens the entire rotor. The customer was delighted, and more wind turbine repair and life extension projects began to flow in.

The project demonstrated that Houghton International had the skills and knowhow to fully refurbish wind turbine generators, saving operators hundreds of thousands of pounds and many tonnes of carbon. “It’s not just the cost of repair or replacement to consider,” explains Robson.

“When a turbine is offline, that’s lost revenue or energy that must be sourced from elsewhere, potentially from non-renewable sources. Every day of downtime has both financial and environmental cost.”

For failed generators, the alternative is refurbishment or replacement by the OEM. Most offshore wind farms are in the North Sea, and the majority of the UK’s onshore wind farms are in Scotland – not so far from Newcastle-upon-Tyne.

“We believe that damaged and failed turbine generators – if they are selected for repair – are often shipped from the North Sea to the country of origin, to the OEM, in which could be anywhere from Germany or Denmark to somewhere in Asia,” says Chris Robson. “These generators would ship right past us on a several hundred mile round-trip, while we are here in Newcastle with the knowledge, equipment, skills and materials to do the work.”

Wind asset management business answers a real market need

Houghton International has received many enquiries from wind farm owners and operators since GCE and is building a strong pipeline of turbine refurbishment work. The service can cover all turbines, onshore and offshore, standard drive train and direct drive, from any manufacturer.

With the forecast boom for the UK’s wind industry and the need to reach 50GW of wind power by 2035 by keeping the existing footprint running, HI’s team saw the potential for a turnkey service. Like any infrastructure, wind turbine manufacturers and owners do not always have the resources to remove, repair and replace key components themselves, or manage multiple subcontractors.

HI will assess and price the contract and project manage the work. The business works with specialist subcontractors, including Second Wind Energy, to remove and transport the generators to and from HI’s facility. A single point of service could save customers money and realise big efficiencies. “It is a turnkey value proposition,” says Robson. “Houghton International can be the principal contractor to control the whole process of removal, transport, workshop, repair, storage and recommissioning – we have more control, and this gives the customer better value. We have a strong network of contractors who can add value in each of their specialist areas.”

The management team at HI are measuring the generator repair and upgrade on all three core metrics: cost, environmental and time savings, especially environmental, as well as the improved performance in the final product. Their sustainability message is: why ship generators across continents when you can upgrade and repair them here in the UK?

“We have the experience, and the tooling, process and reverse engineering knowledge to offer a high quality, competitive lead time service for any wind turbine generator,” says Robson. “And knowing that we are saving companies cash and making measurable reductions to their environmental impact, it’s a very exciting prospect.”

Growth industry needs domestic capability

A very important aspect of the solution is to give UK turbine operators more autonomy. “Wind power is a massive growth industry in the UK and we’re now outside of the European Union,” says Paul at Second Wind Energy. “We are playing catch-up with the EU and are somewhat beholden to their manufacturers, so we must have in-house capabilities here to operate, maintain and repair turbines. Having the intellectual property of generator repair for, for example, Enercon turbines in the UK is now really, important.”

Paul expects there to be a big uptake, especially for certain turbine generator models which have known failure items. There is not currently enough expertise in the UK to provide the whole service and, typically the Europe-based manufacturers are not providing a fast enough service to turn them around. “Some providers want to first sell you a new turbine, and second sell a new generator. Repairing and reinstalling a generator is not a priority for them.”

Considering the life cycle costs of wind farms, high quality refurbishment is a compelling solution for wind energy operators.

Research by Scotland’s ClimateXChange group, from 2015, shows that the manufacture and installation stages together account for over 90% of the total life cycle carbon emissions of an onshore wind farm not constructed on peatlands, and 70% of an offshore farm. Maintenance and operation activities only make up about 6% of onshore wind farm’s life cycle impact. By extending the life of generators and working components, not replacing them, operators can significantly reduce wind farms’ total carbon impact as well as save money.