In fact, it’s not just O&M, rather the industry is looking at sustained improvement across the lifecycle. For instance, coming up with relatively shorter construction period is one area

By Ritesh Gupta

The scope of O&M activities associated with any offshore wind farm is vast, but as various stakeholders repeatedly work on bigger, and more complex projects the understanding is on the rise.

In fact, it’s not just O&M, rather the industry is looking at sustained improvement across the lifecycle. For instance, coming up with relatively shorter construction period is one area.

Similarly, various categories of the overall O&M activity, such as maintenance of the wind turbines, substations, cables and foundations, vessel charter and maintenance, port-side activity, warehousing and on-site office space, resources required to move people and equipment at sea including work boats, offshore bases, helicopter services and jack-up services etc. are being assessed in a diligent manner.

Here we explore how areas, such as the chosen O&M base and blade maintenance, are being improved upon.

Selection of base

The industry has recognised that there are several aspects to port selection as a construction/ fabrication port that have to be assessed – be it for proximity to the offshore construction site, proximity of component suppliers, port authorities and general port limitations, both actual (e.g. quay length, water depth, tidal restrictions, crane facilities etc) and political etc. Even in case of O&M, the choice of base depends upon factors such as relating to vessel performance.

Dudgeon Offshore Wind has signed an initial 25-year lease deal with Great Yarmouth Port Company. The site will be the Dudgeon base during the construction of the wind farm and will be the hub for all O&M activity for the life of the 402 MW Dudgeon offshore wind farm. One of the highlights is the decision to go ahead with a purpose-designed base featuring offices, marine logistic centre and warehouse. The first electricity generation is expected in 2017.

Entities are getting in a position where they can control their maintenance-related expenditure better.

Expectedly, expenditure is not going to be greatly impacted by distance from shore in the future as the distance to shore of the operational fleet of wind turbines goes up and offshore-based access logistics start to emerge.

Scottish Enterprise, in one of its studies released last year, mentioned that closer to shore than 12NM workboat-based strategies are most likely to be cost optimal. Also, while evaluating the status of UK offshore wind projects by distance to port, it underlined that it would be more than 40NM from shore where offshore-based strategies are likely to be “the most practical and economic approach to O&M”.

Optimising maintenance

The industry is much more open to exploring options and how to approach maintenance related decision-making.

If we assess the arena of blade maintenance, the most important development has been the education of the industry on the requirement to perform comprehensive blade inspection and maintenance.

This, according to Complete Wind’s Chris Wraith, has led to a greater understanding on the rates of wear on such things as the leading edge coating, frequency of defect occurrence, necessity for comprehensive End of Warranty rotor blade inspections and requirement for developing a long term operations and maintenance plan.

There are many options available for optimising rotor blades available, with more of these options being offered to owners and operators at the time of rotor blade manufacture. This includes systems that aid in:

-Improving the lightning protection system of the rotor blade and for determining if the rotor blades have registered a strike;

-Decreasing the rotor blade noise;

-Improving rotor blade aerodynamic performance;

-Improving the wear resistance of the leading edge coating

Wraith says many owners and operators are still in the process of developing fully comprehensive operations and maintenance strategies for their rotor blades. These strategies are generally a synergy of in-house, 3rd party and OEM activities.

“Although a long term rotor blade inspection and maintenance strategy should exist prior to end of warranty, the selection of the wind farm owner and operator on how they will perform the post warranty operations and maintenance on the wind farm greatly affects the rotor blade strategy,” Wraith explained.

It must be ensured that any long term service agreements include comprehensive inspection and maintenance plans for the rotor blades that are able to identify issues with the rotor blades at an early stage and allow for, in most cases, efficient scheduling and execution of repairs.

Wraith stated that it is not uncommon for owners and operators to supplement their existing long term service agreements with targeted blade inspections to address any potential gaps.

Being proactive

Planning is getting stronger when it comes to O&M. As observed last year, the team at the Dudgeon Offshore Wind project was on the lookout for a harbour that has the potential to accommodate the amendments expected in vessel solutions as technology develops during three decades long or so lifetime of the project.

On the whole, Wraith proposes that long term operations and maintenance strategy should exist at the time of project pro-forma. With a plan in place at this time, a clear guide will be available to the development team on what is required to ensure the long term operations and maintenance of the wind farm, inclusive of: detailed and specific requests for information, requests for rotor blade optimisation add-ons, facility visits and where applicable audits.

Additional inspections performed at the time of on-site delivery and during construction should also be performed to ensure an understanding of the handling and construction process is gained, and so that if defects are discovered that require repair, these can be performed on the ground, where repairs are much easier to perform and quality work is easier to ensure.