SuperGen UK Centre for Marine Energy Research Annual Assembly 2016

Transcription

1 SuperGen UK Centre for Marine Energy Research Annual Assembly 2016 University of Exeter Novel mooring system development and condition monitoring techniques Prof. Lars Johanning Edinburgh, 30 th Nov 2016

2 Introduction Novel Mooring Tether update Condition Monitoring Acoustic system Condition Monitoring Optical system

3 Novel Moorings The Exeter Tether Design rationale Passive mooring tether Extreme & Fatigue load mitigation

4 non-dimensional surge Novel Moorings The Exeter Tether TRL 1 - basic principles observed non-dimensional horizontal tension Supergen 1 TRL 2 technology concept formulated TRL 3 experimental proof of concept Supergen 2 TRL 4 technology validated in lab TRL 5 technology validated in relevant environment Supergen 3 TRL 6 - technology demonstrated in relevant environment TRL 7 system prototype demonstration in operational environment TRL 8 system complete and qualified H OPERA Industry

5 Novel Moorings The Exeter Tether Material Testing IFREMER Tensile, compressive and ageing investigations Reduction in strength Marine ageing Increase in stiffness Reduced fatigue life

6 Novel Moorings The Exeter Tether Fatigue testing - DMaC Test Facility Thousand Cycle Load Limit test conducted Standard fatigue test from OCIMF Exeter Tether TCLL = 65.3% Promising result for early prototype Areas for improvement identified: Revised cord terminations Improved eye splice quality control Tether / rope construction TCLL value Source Exeter Tether 65.3% New result Monofilament nylon 55% Lankhorst Monofilament polypropylene 52% Lankhorst Euroflex 79.6% Lankhorst Eurofloat 73.0% Lankhorst Tipto 70.7% Lankhorst Lankoforce 100% Lankhorst AmSteel -Blue 100% Samson Ropes Saturn % Samson Ropes

7 Novel Moorings The Exeter Tether Sea Testing - SWMTF Deployment approaching 6 months DMaC testing to compare pre and post deployment Increase in axial dynamic stiffness Significant biofouling ingress Degradation of anti-friction membrane Areas for improvement identified: Revised anti-friction membranes trialled, 55µm UHMWPE showed promising results Outer protective jacket required to prevent biofouling ingress into core construction

8 Novel Moorings The Exeter Tether

9 Novel Moorings The Exeter Tether

10 Novel Moorings The Exeter Tether Studied the stiffness response depends of the diameter of the core: Change the contact area The space between the cord The Load necessary to arrive to a strain value. Laboratory test 42 test were realized. 7 different diameters (8.0, 10.0, 12.0, 15.0, ,25.0, 35, 37 and 40 mm) Numerical model To date numerical model Comsol is being calibrated to represent the laboratory results and then increase the cases studied.

11 Novel Moorings The Exeter Tether H2020 OPERA Project Project aims to reduce WEC mooring costs by 50% Exeter Tether 12 months field testing Deployed within Karratu Network Mooring system evaluation from in comparison to standard components Quantify effect of Exeter Tether on mooring system loads Karratu network mooring (Ricci et al. 2012)

12 Condition monitoring Acoustic Emissions Acoustic Emissions (AE) are sounds related to the engineering health and operating conditions of engineering components. In air, sensors are placed directly onto components. In water, we can use the increased propagation of sound to remotely sense acoustic emissions propagating from the device m Detecting AE underwater, and separating AE from environment noises, is developing as a reliable, remote monitoring technique.

13 Condition monitoring Acoustic Emissions Possible to connect acoustic signature to: System dynamics Changing environmental conditions

14 Condition monitoring Acoustic Emissions Propagation modelling study - To assess the impact of range, bathymetry and sediment on AE monitoring. Detailed Modelling Environment J. Garrett, University of Exeter, PhD Thesis Receiver depth Bathymetry

15 Condition monitoring Polymer Optical Fibres Concept: Optical Time Domain Reflectometry (OTDR) Embed Polymer Optical Fibres (POFs) into fibre mooring rope OTDR source injects laser down POF OTDR detector receives light reflected from different elements of the POF Typical OTDR trace (Kerridge 1999) Signal processing of traces can detect changes to POF - potential to detect: Strain Bending

16 Condition monitoring Polymer Optical Fibres Method Basic POF mechanical tests Select best optical fibres Full suite of tensile and fatigue tests Develop OTDR strain detection Embed POF in fibre rope - Important to terminate POFs securely for mechanical testing - Developing POF termination techniques epoxy resin plugs: Potting plug Plug termination Tensile testing of plug technique

17 Condition monitoring Polymer Optical Fibres Results to date - Issues with jacketed POFs pulling out of plugs or slipping over POF - Good results for bare fibres, range of fibres tested from 0.5 1mm Ø - POFs yielding at low extensions limit of extension ~ 2.5% Early results: Stress strain curves for bare POFs, 0.5mm, 0.75mm and 1mm. - Due to low extensions, Helix arrangement required to provide sufficient extension when embedding POF in conventional fibre rope

18 Acknowledgements Dr. Philipp Thies Tessa Gordelier Itxaso Oderiz Dr. David Parish Jodie Walsh This work has been funded by SuperGen: (Grant # EP/ /1). Further assistance has been provided through: - Marinet FP7 funded through the EC - OPERA Project funded through EC Horizon NERC GW4 + References T. Gordelier, D. Parish, P.R.Thies, L.Johanning. (2015) A Novel Mooring Tether for Highly-Dynamic Offshore Applications; Mitigating Peak and Fatigue Loads via Selectable Axial Stiffness, JMSE, 3(4): I. Bashir, J. Walsh, P. R. Thies, S. Weller, P. Blondel, and L. Johanning, Underwater Acoustic Emission Monitoring Experimental investigations of Synthetic Mooring Ropes, under review (2016). J. Walsh, I. Bashir, J. Garrett, P. R. Thies, P. Blondel, and L. Johanning, Monitoring the condition of Marine Renewable Energy Devices through underwater Acoustic Emissions: Case study of a Wave Energy Converter in Falmouth Bay, UK. Renewable Energy 102 (2017): J.Garrett. Interdisciplinary study into the effect of a marine renewable energy testing facility on the underwater sound in Falmouth Bay. University of Exeter, PhD Thesis, 2016.

19 SuperGen UK Centre for Marine Energy Research Annual Assembly 2015 University of Exeter Novel mooring system development and condition monitoring techniques Thank you! Questions?