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Online Remote Condition Monitoring of Tidal Stream Generators

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Greater reliability for tidal energy production

Harnessing the power of nature by using the tides to drive a turbine and produce electricity can provide a valuable source of renewable energy. But tidal turbines are subject to serious wear and tear, resulting in a significant cost in time and money when they undergo maintenance – an EU-funded initiative addressed this challenge.

Energy

Tidal streams are highly directional and predictable with stored energy density 800 times greater than that in wind for the same speed. The necessary infrastructure to produce renewable energy from this source can be hidden away under water and stored in cages to protect wildlife and passing ships. However, despite the benefits, tidal stream power has been underutilised due to problems with operation and maintenance. For example, structural vibrations of the large, heavy turbine components can reduce their effectiveness and lead to failure, resulting in their being available for as little as 25 % of the time. Structural health monitoring is well established in many fields, but underdeveloped in tidal stream power plants. This issue was addressed by the REMO (Online remote condition monitoring of tidal stream generators) project, which brought the technology up to date. Consortium members set out to reduce projected life-cycle maintenance costs by 50 % and achieve availability times of more than 96 %, which is comparable to those of wind turbines. Energy production costs will also be in line with wind turbines, thereby encouraging investment and realisation of the full economic and environmental benefits of using tidal power as a renewable source of energy. Tidal turbines' gearboxes are one of the most important causes of downtime as they must operate under a very harsh variable-load environment, causing a high level of wear and fatigue in gearbox components. In addition, the turbine motors must be prepared with the appropriate sealant so that they are able to work underwater. Researchers first determined the frequency signal of a healthy tidal stream turbine. On-site accelerometers and acoustic emission sensors then monitored low- and high-frequency vibrations for all rotational components during the operational lifetime. Deviations from the healthy signature caused an automatic alarm to sound, thereby enabling preventative maintenance to be carried out before the turbine became damaged. REMO's remote structural health monitoring technology for tidal stream turbines will catch potential faults before they occur. The sensor system will significantly decrease maintenance time and costs, increasing availability and thus bringing operating and electricity costs in line with those of wind turbines. Furthermore, widespread investment and market uptake will have important benefits for related industries, consumers and the environment.

Keywords

Turbine, electricity, renewable energy, tidal stream, structural health monitoring, rotational components

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