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Advanced monitoring, simulation and control of tidal devices in unsteady, highly turbulent realistic tide environments

Periodic Reporting for period 1 - RealTide (Advanced monitoring, simulation and control of tidal devices in unsteady, highly turbulent realistic tide environments)

Berichtszeitraum: 2018-01-01 bis 2019-06-30

Tidal Energy sector is facing a harsh environment and more precisely the turbulence due to highly energetic currents and ocean waves. In the last years, several companies developed different concepts for exploiting the tidal currents and produce electricity which can be ranked in 3 categories: horizontal axis, vertical axis and other concepts. Nowadays, Tidal Energy is developed for isolated sites which are not grid connected to assure, in the future, an independent electricity production. Then, when technologies will prove their efficiency and will lower the cost production, the market will open to bigger projects connected to the grid.
Tidal Energy sector is, at this stage, focused on research development to tackle the lack of knowledge of turbulence in tidal currents which can likely improve the understanding of failures in Tidal Energy technologies. This could result in improved design versions of actual prototypes.
The RealTide project is using innovative flow measurement instrumentation - deploy at sea -, reliability methodologies coupled with condition monitoring, studies on new materials for blades and tide-to-wire modelling to give to the stakeholders guidelines to develop the next generation of their technologies.
During the first half of the 3-year project, partners performed the key steps of the RealTide project to be continued for the second half.
Thanks to partners experience, existing literature and previous research projects, a Failure Mode and Effects Analysis (FMEA) report has been published. 4 generic concepts have been defined to cover most of the existing technologies: 1. Complex bottom fixed / 2. Simple bottom fixed / 3. Floating multi rotor / 4. Cross flow turbine.
The FMEA methodology applied to RealTide led to recommendations depending on the criticality for a modification of design structure (redundancy, more reliable component, etc) and/or condition monitoring.
In parallel, an initial monitoring plan for Tidal Energy Converters (TECs) was also published, including a state-of-the-art of the current monitoring techniques and a proposition for TECs and the Sabella’s TEC. A model-based estimation has been developed to improve the system reliability. Such model can help to reduce redundancy of critical sensors or to eliminate it by this virtual monitoring technique. This task was the first step of the next on-going work conducted to implement a specific algorithm in the Conditioning-Monitoring System.
Partners started to work on a Reliability, Availability and Maintainability study applied on two of the four concepts (the methodology can be further used for the two other concepts) based on the FMEA. It aims to determine with deeper details design and/or monitoring recommendations to assess the electricity production. It will also be an important input for the Business Case study. A guideline will be then developed for the development of a TECs reliability database.
Another key objective addresses in RealTide concerns the flow characterization and precisely the turbulence to improve the knowledge on the realistic sea conditions. After delivering the exploitable data to all the partners and describing the methodology to use it, a Deployment and Instrument Specification for Advanced Flow Characterization has been released. It explains how the high-resolution instruments will be deployed at sea and recovered for the measurement campaigns in the Fromveur channel, in France.
Simultaneously, the Generalised Tide-to-Wire tool has been built from open-source software to a dedicated RealTide tool. The model is using blade element momentum theory to calculate the torque and thrust of a TEC from tidal conditions input. The modelling calculation result is the electricity production. The tool has been validated with cases study. A Computational Fluid Dynamics (CFD) solver is currently integrated in the tool in order to incorporate large scale - realistic - upstream turbulence. With the measurements in Fromveur passage and the characterization of the turbulence, the tool will be improved.
Two test campaigns in IFREMER the University of Edinburgh flumes have started and will finish at the end of this year. The outputs of the model and these tests will serve to develop a series of synthetic load spectra and force/load time series for validation of the monitoring technology and the blade response.
Finally, as it was noticed that failures on blades occur in TEC demonstration projects, composite materials are under tests in sea water. First results has been analysed on the fatigue tests and will be deliver at the end of this year. This analysis will normally result in a reduction of uncertainty in lifetime prediction and improve reliability. It will also evaluate existing and lower cost options for the TEC blades.