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Building on renewable energy #2 - Wind power

05 March 2020

Wind power is, unsurprisingly, generated by wind (typically as little as a light breeze) passing over and turning the turbine's blades. The blades are connected via a shaft and gearbox to a generator, which converts the kinetic energy into electrical energy. A transformer then increases the voltage of the generated energy to enable transmission to the grid.

Whether on or offshore, the design and construction of a wind turbine (or several turbines in a 'wind-farm'), will present various technical challenges. We consider a few of these such challenges below:

Design and Construction

The selection of a site, and the location of turbines within the site, can present initial difficulties. Wind-speed data, and the calculation of shadow-flicker for an onshore site, are important design considerations (including the rotor height of the turbine), and impact upon the financial assessment of the site.

Wind speed is particularly important to design. The stresses placed on the single connecting point between the rotor drive shaft can be extreme, and careful consideration needs to be given to these forces when making design decisions on the number, length, pitch, and construction of the rotor blades.

Shadow-flicker is the effect sometimes created by the shadow from a moving blade passing over a small opening - such as a window in a residential property - causing a strobing or flickering to occur within the room. If the site is designed or modelled incorrectly, and shadow flicker impacts upon residential properties in the vicinity of the turbine, then enforcement notices may be served upon the turbine owner. The turbine could require a sensor to be retro-fitted, shutting down the turbine in meteorological conditions where flicker is likely to occur, restricting generating hours and profitability.

Both offshore and onshore turbines have typically required substantive piling works to provide adequate stability, although several non-traditional floating turbines have now been built offshore (with more under construction), as have those with suction-bucket foundations. All will typically have long cable runs, which require careful attention. The experience and claims history of contractors and sub-contractors will be key to Insurers' decision whether to underwrite a risk, and at what premium.

Contractors and Insurers alike need to be alive to contractual terms more onerous than a duty to exercise reasonable skill and care, including fitness for purpose and/or design life warranties (see our article here) as the courts seem more willing to apply this stricter standard. The Supreme Court decision in MT Højgaard A/S v E.ON Climate & Renewables [2017] UKSC 59 illustrates the potentially significant remedial costs that may arise, and remain the contractor's responsibility.


Given the forces that turbines are subjected to, effective maintenance is vital in maximising the life of a turbine. Ensuring experienced asset managers / O&M contractors are retained, with tight contract control (including monitoring, inspections, and maintenance activities), will reduce the likelihood – and severity – of claims.

Modern wind turbines are often able to be monitored and controlled remotely, and there are fascinating projects ongoing which seek to develop autonomous vessels, crawling robots and aerial vehicles to carry out inspections and maintenance of wind turbines. Whilst such advances will undoubtedly reduce liability risk (particularly to technicians working in extreme conditions offshore), and the costs of inspection (for example, downtime and the charter of appropriate vessels), this remote and potentially autonomous access is not without risk. Robust and appropriate cyber protections are required to prevent unauthorised access, particularly as a traditional business interruption policy would be unlikely to provide cover (if physical damage is not caused to the turbine). 


The first swarths of commercial wind turbines have started to reach the end of their service lives, and decisions are being made as to the decommissioning or repowering of the turbine sites. Each presents its own construction and logistical challenges.

When decommissioning is the only option, there remains the difficult issue of the disposal of the rotor blades, as the technology to recycle the composite materials is in its infancy. Landfill is an unattractive option (and has, indeed, been capped or banned in some countries), with potential reputational issues for all involved with the project. Parties may wish to investigate whether a sustainable decommissioning plan is in place (perhaps through traditional recycling or reuse on secondary market installations, or the ingenious utilisation of sections of blades as public furniture, such as in the Netherlands), before becoming involved with a project.


 Click here to read the previous article: #1 Solar power