Offshore wind farm maintenance: High time for a new approach?

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Aside from upfront costs, the maintenance of offshore wind farm assets represents a sizeable cost of any project. It is therefore in the renewable industry’s interests to find ways to drive down this cost – while all the time guaranteeing the integrity of its installations. This article explains how a maintenance regime that borrows from those used in the oil and gas industry could pay dividends.

It is useful to consider the context of maintenance of wind farms. Firstly, there are few duties imposed on operators when it comes to this subject. It is true that at the consenting stage, some obligations may be specified for maintenance; however, these are likely to only be short term in nature. The original equipment manufacturer (OEM) may also recommend particular maintenance, especially in the early years of an installation. However, for the average in-service project there is little guidance or advice available for truly tackling and understanding maintenance in its entirety.

Another factor is the particular parts of an offshore installation which are typically subject to maintenance. While the above-the-sea elements might be subject to routine inspection and repair where necessary, from our experience few operators are properly considering subsea aspects, and connection cabling and associated equipment in particular. This represents an unnecessary technical risk to projects that are currently in operation.

The result of taking an informal approach has been the development of project-by-project maintenance techniques, and certainly no formalised approach that is used across the industry, despite the first offshore wind farm being installed off the Danish coast more than 20 years ago.

With a sharp rise in the number of offshore wind farms being installed off our coasts – and a total of more than 1,200 individual turbines in European waters alone according to the European Wind Energy Association – not to mention some major offshore installations now reaching middle age, the need to place a greater focus on maintenance is increasing. It is my belief that the topic needs to be comprehensively rethought and that without a radical new, and more formalised, approach being taken to maintenance, offshore operators are exposing themselves to unnecessary technical and financial risks.

Learn form the oil S gas industry

It is helpful at this stage to look to other industries, and to consider whether anything can be learned. Despite first impressions, I contest that the oil and gas industry – having been established offshore for so long – offers some valuable pointers that wind farm operators could do well to learn from. Of course, the differences in the regulatory environments of the oil and gas and renewables industries could not be more different. While offshore oil operators are used to stringent regulations, driven to a large extent by need to protect the health and safety of offshore personnel, no such framework currently exists for the renewables industry.

In the oil and gas world, TRM’ (or ‘Inspection, Repair and Maintenance’) describes the overarching approach that is typically used. This is a planned means of evaluating the performance and integrity of key elements of the plant on a regular basis, and performing the necessary repair and maintenance as a result. It is cyclical, meaning that outputs from the repair and maintenance that is carried out are fed into the ongoing inspection routine to ensure inspection activities remain appropriate.

The renewables industry could do well to take heed of this approach. The key point is that maintenance needs to be seen as a proactive process, rather than a reactive one. What’s more, installations need to be looked at in a more holistic way so that every component, no matter how small or apparently insignificant, is mapped and analysed for the risk it may pose to the entire system should it become defective.

This is not about directly taking the methods that the oil and gas industry use and applying them to the growing offshore wind market; rather it is about understanding the broad approach that is commonplace in oil and gas and seeing which elements could be transferred to the renewables industry. This is coupled with taking a long term, common sense approach to understanding maintenance needs and costs. We would suggest calling this Inspection, Maintenance and Repair (IMR) – rather than the oil and gas industry’s IRM – to reflect the importance of prioritising maintenance over repair.

So what might a new maintenance technique for offshore wind farm operators look like? We have studied the options for operators and believe that an approach based on verification, where a thorough assessment of risk is considered at the same time as quality control, is what is urgently needed. By properly understanding every aspect of an installation, including the crucial subsea elements, inspection can be performed at appropriate intervals and maintenance correspondingly planned.

Implementing IMR

Practically speaking, we see there being six main stages to implementing IMR. To begin, an audit and review of the existing data and information that exists on maintaining the wind farm should take place. With little in the way of industry-standard best practice currently in circulation, this may be restricted to maintenance recommendations available from the OEM, but there may also be guidance from the earlier consenting process available. Up until now, this step alone may have been deemed sufficient, but we believe this should be seen as just a starting point.

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With the available information in hand, operators should then look to the installation itself in order to identify those elements that may represent a risk, no matter how small, to its successful functioning. A risk analysis can then be performed on each of these aspects to understand the extent to which they may pose a critical integrity or safety risk. Any pre-existing information that was collated at the earlier stage can also be brought in here, so that operators can be completely clear on every risk that the wind farm may present.

We would then advocate standards being developed that set out the required performance for each safety critical element of a wind farm, in either qualitative or quantitative terms.

By combining the safety critical aspects of an installation with these performance aspects, a Written Scheme of Examination (or simply ‘WSE’) can be developed. In essence, this aspect of the IMR process is where the maintenance regime for a wind farm is documented, both in terms of what maintenance is specifically needed and how regularly it needs to take place. At this point, operators would also take account of what could be considered ‘reasonable’ performance from each component.

For some operators, it may be sufficient to have a full WSE that is reviewed and updated periodically, depending on the results of ongoing inspection and maintenance activities. But there is an important last point to be considered. Having a WSE independently verified can give operators, and associated parties such as financiers, the confidence they need that their installation can perform to a specified level, with minimal chance of unexpected downtime.

Risk can never be entirely removed from any engineered system, and a complex offshore wind farm is no exception. However, I believe that an approach to maintenance based on the principles of IMR can help manage and minimise these risks and, if followed through methodically, can reap enormous benefits. Rather than following a maintenance regime that is either outdated or too generic for an individual wind farm, operators will only be completing the maintenance that is needed for reliable, safe functioning.

Stephen Bolton, Director of Operations and Maintenance at Offshore Marine Management