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Innovation Challenges

Subsurface Structural Inspection of Blades


Defects can occur throughout the composite material of a blade, not just on the visible surface.  Composites used for blades are formed by impregnating strong fibre reinforcements with resin. The result is a very robust, erosion resistant material however the curing process can result in voids and air bubbles within the material, creating weak spots. If these areas of weakness are not picked up in inspection, fatigue loading can lead to catastrophic blade failure on site. Subsurface inspection is one method used to detect these flaws before they become critical.

Currently, subsurface blade inspections are carried out by human operators using rope-access, however the process of inspection is generally rather basic; operators tap blades and listening for differences in the material properties which may indicate cracks or defects.  Using this method, imperfections can easily be missed and there are also several health and safety issues with rope-access inspection. To inspect blades more rigorously, other methods of NDT could be used and the need for human intervention could be reduced. Solutions could consider robotics, multitasking unmanned aerial vehicles (UAVs), sensors or advanced imaging, methods using artificial intelligence etc. This change in approach would increase the probability of imperfections being detected before they become critical and by minimising human intervention, the health and safety risks of inspection operations would be greatly reduced.


The proposed solutions for this challenge must be deployable without requiring changes to existing manufacturing and design of offshore wind turbines.  To meet the desired timescale and risks, it is preferred that the proposed solution, or the key part(s) of the solution, has been commercially proven in other sectors.

Functional Requirements

  • A potential solution capable of detecting, monitoring and acquiring data concerning the physical surface, and sub-surface condition of a wind turbine blade.
  • Solutions must be deployed safely and ideally remotely to reduce human intervention.
  • Inspections must be undertaken with the blade in-situ, ideally without the need for the blade to be held stationary.
  • The acquired data, such as measurements, images, logging time and ambient conditions must be available for further analysis after inspection.
  • Solutions must be able to work for long periods without the need to recharge the power source.

Technical Characteristics

  • Solutions must be capable of non-destructive/non-intrusive inspection of the blade.
  • Solutions must be capable of detecting sub-surface cracks due to fatigue, damage or manufacturing defects, which could not be identifiable from visual inspection of the surface alone, whether at the blade tip, along the length, or at the root of the blade.
  • Solutions should be capable of detecting a minimum physical flaw/defect of 10mm at a resolution of ±5mm, ideally to a depth of 5cm. The flaws may include a surface/subsurface crack, voids, de-bonding, delamination, etc.
  • For dynamic (i.e. non-stationary) inspection, solutions must operate while physically attached to the structure.
  • Solutions must be as compact as possible and highly mobile with added ruggedness to resist offshore marine environments.
  • Solutions’ inspection efficiency must not be affected by atmospheric conditions such as poor lighting, high wind gusts, salt/dirt/particle deposits etc.

Deployment Timescale

  • Validation of solution: within 1 year
  • Field trials: within 1-2 years
  • Commercial implementation: within 3 years

Operating Conditions

  • Solutions must be able to be operated safely and reliably in offshore conditions with:
    • wind speeds of 8ms-1, with gusts of up to 25ms-1
    • an ambient temperature 0-40°C
    • heights of 100-200m from sea-level
    • distances up to 25km from shore, ideally up to 40km

Cost Requirements

  • New solutions must offer a faster inspection rate at a lower overall cost. Current industry practice is capable of inspecting three structures per day at an estimated cost of £6,000.
  • An ideal solution should aim to achieve a 50% overall improvement on cost and time of inspection.
  • The current estimated UK market for a successful solution will be in the region of £20m p.a. with a significant additional export market.

Europe has 4,149 offshore turbines installed and grid-connected... all require regular servicing and maintenance throughout their 20-25 year design life.


Operations and maintenance (O&M) costs can account for up to 25% of the levelised cost of energy from an offshore wind farm.  Wind turbines are increasing in size (60% growth in power rating from 2010 – 2016) and are being sited further from shore (currently averaging 43.5km and set to increase during the build of UK Round 3 projects) and in deeper water. This increases the challenges associated with servicing and maintaining them, as well as the costs, but opens up exciting opportunities for new technologies as wind farm Owner/Operators look to reduce those costs.

Offshore wind turbine blades tend to be between 50 and 88m long. Condition monitoring is becoming more critical as owner operators look to improve their understanding of blade erosion and remedial repair requirements as the assets age.  The service and repair market for blades is experiencing rapid growth due to the accumulation effect of continual wind farm development and installation.

Market size

The O&M market has seen rapid growth following a sustained offshore wind build programme in Europe led by the UK and Germany. Europe has 4,149 offshore turbines installed and grid-connected as of January 2018, with 81 offshore wind farms operating in 11 European countries making a grand total of 15.8 GW operating capacity. All these turbines require regular servicing and maintenance throughout their 20-25 year design life and the average operating expenditure (OPEX) ranges from £60,000 /MW/year (E&Y, 2009) to £87,500 /MW/year (BVG Associates, 2012).

Market forecast

The 11 offshore projects under construction in Europe as of June 2017 will increase installed capacity by a further 2.9GW.  In 2016 a total of 4,948MW of new capacity reached FID and it is projected that the total European installed capacity will reach 25 GW by 2020.

Do you have a potential solution?

Technologies that can reduce the cost of offshore wind blade structural inspections have a significant potential market.

Apply now

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