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The vital role for condition monitoring systems in wave and tidal energy

By Simon Cheeseman, Sector Lead, Wave and Tidal Energy, Offshore Renewable Energy Catapult

 Condition Monitoring Systems (CMS) are already well established in the offshore wind industry. A range of sensors can be used to monitor the structure and internal equipment remotely and detect when any components are requiring repair or maintenance. CMS reduces the need for maintenance crews to make physical inspections of the wind turbines and the CMS technology used has been growing in sophistication over recent years. This is important when you consider the difficulties in accessing many of these structures and the fact that operations and maintenance (O&M) costs can account for up to 35 per cent of the total cost of power supplied by offshore wind installations.

While there is much to learn from the experience of offshore wind, wave and tidal energy presents its own particular set of challenges. Compared to wind, there is a wider range of different types of devices currently being developed, which makes standardisation of a CMS approach more difficult. Wave devices are designed to operate in very harsh sea conditions and are subject to a very different set of stresses and strains compared to wind turbines.

A complete CMS for wave and tidal devices would need to cover a very broad range of potential failure areas, including:

·        Moorings, e.g. structural failure, loss of position

·        Structural, e.g. hull breach, deformation

·        Hydraulic, e.g. oil leakage, seal failure

·        Electrical, e.g. generator failure, connector fault

·        Instrumentation, e.g. calibration error, software fault

In order for wind and tidal energy to be commercialised and to reach its full potential, it has to win the complete confidence of investors. Therefore, they will need to be reassured that the devices will generate a consistent level of power, that they will operate reliably, that ongoing O&M costs will be controlled and tightly managed, and that any risks have been mitigated as much as possible – particularly the risk of a catastrophic equipment failure. (Experience from the offshore wind industry has shown that unplanned repair work can be six times more costly than scheduled repairs.) As a result, creating an effective CMS approach will be a pivotal part of developing wave and tidal energy into a viable and sustainable industry.

There will be a major focus on this area of marine technology over the next five years. This will present marine technology businesses with a broad range of challenges and commercial opportunities. There will be a need for clever new solutions in innovative types of sensor technology, prognostic approaches which can predict when specific types of materials will fail, better systems for monitoring the power output from energy devices, and more sophisticated data gathering and communications equipment which can operate in all weathers and all sea conditions. This will have to be underpinned by leading-edge software and analysis, including more advanced algorithms and artificial intelligence, to make full sense of the vast amount of data that will be generated and to translate it into outputs that a technical team can swiftly act on.

Finally, these new types of CMS will need to prove their reliability by undergoing extensive sea trials and this is being pursued by a number of international research projects, notably the Reliability in a Sea of Risk (RiaSoR) project. This international collaboration is designed to improve the reliability of wave and tidal energy convertors. In stage one of the project, a reliability framework was built, taking  established practices from the automotive industry where a monitoring framework is applied to a fleet of test-vehicles. In stage two, components for monitoring will be equipped with several sensors to collect required data, which will then be fed into the reliability process. This stage will include extensive sea trials of the sensing equipment. This is just part of the pioneering work that needs to be done to create the new types of CMS that the industry will require. You can see full details on this ground breaking project at: http://riasor.com/

Not only will the coming years be a very exciting phase in the development of wave and tidal power, but the data yielded by these new technical solutions and sea trials will further increase our understanding of this technology, giving us more guidance on how it can be designed to perform at its optimum level. The research that is currently being done will also help shape the creation of improved maintenance strategies for wave and tidal energy devices, which will create further momentum behind the sector.