Abstract
There is a progression towards lowering the price of offshore renewable energy including the wave energy sector. Accessibility is a challenge with offshore generation devices including wave energy converters (WEC) and this is why the deployment of condition-based monitoring systems will be crucial to support operation activities. Condition monitoring systems are used to optimise maintenance and provide early detection while also reducing access constraints. This report study provides an insight into condition monitoring of Wave Energy Converters.
There is a wide range of wave energy technologies, each using different solutions to absorb energy from waves depending on the water depth and location. There is little convergence amongst the wave energy technologies, however, the industry shows many different alternatives to harnessing wave power under different conditions. It is believed that existing monitoring systems within the wave devices developed to date draw directly from current technologies and advances made in the wind and other industries.
Defects and errors can affect the operation or structural integrity of the wave energy device. Failure modes are the various ways in which the WEC could possibly fail and monitoring systems are often used to anticipate complete failure and for fault detection. Based on literature key WECs failure modes identified include, mechanical, electrical, structural and marine environment impact. Based on these failure modes, a number of sensing technologies and systems were proposed to monitor the integrity of the WEC device. The proposed sensors and method of detection must be able to provide effective failure detection and meet the requirements of accuracy, cost effectiveness and long-term stability.
CMS uses detection methods with analogue signals which must be conditioned before being digitised. Signal conditioning is the next stage of processing where the signal is made available for data analyses. Signal conditioning requirements in terms of amplification, attenuation and filtering to improve signal accuracy were also addressed in this report.
Based on IEC 61400-25 standard which addresses all aspects of communication architecture for the monitoring and control of wind power plants, an example of a WEC device communication architecture concept was proposed including the positioning of the monitoring, protection and control information equipment at different location within the device. The concept divides the whole architecture of the WEC into multiple segments where; (i) the device front end (PTO) is equipped with a number of sensing and monitoring equipment, (ii) the controller is located behind the generator and (iii) the grid compliant generated power, metering and user control interface.
General procedures which must be considered when setting up condition monitoring within sub-assemblies of machines like wave energy converters. As such a number of relevant standards and procedures for condition monitoring were summarised. It is believed that the communications for monitoring and control of wind power plants (IEC 61400-25) is conveniently compatible with WEC applications. The basic concept of this IEC is a breakdown of compliant services and the different communication profiles available for data interchange, allowing all data from the devices to follow the same format.