Sensing failure in deep marine power generators
Among the numerous sources of renewable energy that can be exploited to relieve dependence on fossil fuels is tidal flow. Marine turbines located deep on the seabed floor have rotating blades similar to those of wind turbines. They convert the mechanical energy of tidal flows into electrical energy. Automated structural health monitoring (SHM) of turbine blade integrity would reduce maintenance time and operating costs as well as hazards to inspection personnel. Scientists working on the EU-funded project 'Development of a condition monitoring system for tidal stream generator structures' (TIDALSENSE) delivered such a system using a novel technique called long-range ultrasonic testing (LRUT). The TIDALSENSE LRU sensor array excites and detects LRU signals along with propagating acoustic elastic waves from external perturbation, making it particularly flexible in terms of potential applications. It detects changes in the characteristics of ultrasound waves, which in turn are indicative of material changes within the structures. The integration of signal conditioning software to enhance sensitivity and an automated defect detection (ADD) system enables accurate defect identification and classification. Wireless communications technology transfers data from the blade to the control centre. Scientists also developed data management and visualisation software accommodating signal analysis, display of results and generation of reports. Field trials on a mock-up blade confirmed the effective and reliable detection of structural defects in tidal marine turbine blades. Quick and simple inspection of submerged composite parts could have application to other maritime structures. Finally, more widespread implementation of tidal stream power generation is expected to have important impact on the cost of utilities and the health of the planet.