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Infrastructure Access Report

Infrastructure: UCC‐HMRC Ocean Wave Basin

User‐Project: JOULES ‐ Wavetrain

Performance of the JOULES Wavetrain WEC

Joules Energy Efficiency Services Ltd

Marine Renewables Infrastructure Network

Status: Draft Version: 01 Date: 17‐Jan‐2013

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Infrastructure Access Report: JOULES ‐ Wavetrain

Rev. 01, 17‐Jan‐2013 of 19

DOCUMENT INFORMATION Title Performance of the JOULES Wavetrain WEC Distribution Public Document Reference MARINET‐TA1‐JOULES ‐ Wavetrain User‐Group Leader, Lead Author

Dr Nicholas Wells Joules Energy Efficiency Services Ltd. 10 Edenderry Road, Belfast, BT8 8LD, N. Ireland. [email protected]

User‐Group Members, Contributing Authors

Dr Bjoern Elsaesser Queens University Belfast

Infrastructure Accessed: UCC‐HMRC Ocean Wave Basin Infrastructure Manager (or Main Contact)

Brian Holmes

REVISION HISTORY Rev. Date Description Prepared by

(Name) Approved By Infrastructure

Manager

Status (Draft/Final)

01 17/01/13 Infrastructure Access Report Dr Nick Wells


Rev. 01, 17‐Jan‐2013 of 19

ABOUT THIS REPORT One of the requirements of the EC in enabling a user group to benefit from free‐of‐charge access to an infrastructure is that the user group must be entitled to disseminate the foreground (information and results) that they have generated under the project in order to progress the state‐of‐the‐art of the sector. Notwithstanding this, the EC also state that dissemination activities shall be compatible with the protection of intellectual property rights, confidentiality obligations and the legitimate interests of the owner(s) of the foreground. The aim of this report is therefore to meet the first requirement of publicly disseminating the knowledge generated through this MARINET infrastructure access project in an accessible format in order to:

• progress the state‐of‐the‐art • publicise resulting progress made for the technology/industry • provide evidence of progress made along the Structured Development Plan • provide due diligence material for potential future investment and financing • share lessons learned • avoid potential future replication by others • provide opportunities for future collaboration • etc.

In some cases, the user group may wish to protect some of this information which they deem commercially sensitive, and so may choose to present results in a normalised (non‐dimensional) format or withhold certain design data – this is acceptable and allowed for in the second requirement outlined above.

ACKNOWLEDGEMENT The work described in this publication has received support from MARINET, a European Community ‐ Research Infrastructure Action under the FP7 “Capacities” Specific Programme.

LEGAL DISCLAIMER The views expressed, and responsibility for the content of this publication, lie solely with the authors. The European Commission is not liable for any use that may be made of the information contained herein. This work may rely on data from sources external to the MARINET project Consortium. Members of the Consortium do not accept liability for loss or damage suffered by any third party as a result of errors or inaccuracies in such data. The information in this document is provided “as is” and no guarantee or warranty is given that the information is fit for any particular purpose. The user thereof uses the information at its sole risk and neither the European Commission nor any member of the MARINET Consortium is liable for any use that may be made of the information.


Rev. 01, 17‐Jan‐2013 of 19

EXECUTIVE SUMMARY The “Wavetrain” device is a Wave Energy Converter (WEC) Concept designed by Dr Nick Wells of Joules E. E. S. Ltd. The device is based on a floating oscillating body enclosing a water column which serves as an inertial reference and is inclined at an angle of 45° downwards against the wave propagation direction. The current design consists of three floating bodies connected to each other, with the leading device connected to a floating buoy. The picture in Figure 1 shows the three devices in the HMRC wave tank. A number of theoretical investigations have taken place to examine the likely performance of this wave energy converter. In essence the device can be perceived as a hybrid between an attenuator and an array of three point absorbers. Each individual device acts as a point absorber to the incident wave, although as a linked system it shows some of the interdependence of an attenuator WEC. An initial set of tests was conducted in June 2010 at the QUB, Portaferry wave tank that indicated a relatively good capture performance.

Figure 1: Initial floating test at HMRC wave tank

The key objective of the HMRC tests was to determine the individual body motions for all three articulated modules in the Wavetrain device and to ascertain if the estimated response amplitude operators are realistic in terms of overall performance of the full‐scale integrated system. The second objective was to measure the axial forces in the tubular struts forming part of the device articulation mechanism and mooring system. Knowledge of these forces will enable detailed structural design optimisation of the strut system and articulated joints. Both key objectives were achieved in the Marinet funded tests at HMRC with a total of 65 separate test runs accomplished during the allocated test period.


Rev. 01, 17‐Jan‐2013 of 19

CONTENTS

1 INTRODUCTION & BACKGROUND .................................................................................................................... 7

1.1 INTRODUCTION .................................................................................................................................................... 7 1.2 DEVELOPMENT SO FAR .......................................................................................................................................... 7 1.2.1 Stage Gate Progress .................................................................................................................................... 7 1.2.2 Plan For This Access ..................................................................................................................................... 8

2 OUTLINE OF WORK CARRIED OUT .................................................................................................................... 9

2.1 SETUP ................................................................................................................................................................. 9 2.2 TESTS ............................................................................................................................................................... 14 2.2.1 Test Plan .................................................................................................................................................... 14 2.3 RESULTS ............................................................................................................................................................ 14 2.4 ANALYSIS & CONCLUSIONS ................................................................................................................................... 16

3 MAIN LEARNING OUTCOMES ......................................................................................................................... 16

3.1 PROGRESS MADE ............................................................................................................................................... 16 3.1.1 Progress Made: For This User‐Group or Technology ................................................................................. 17 3.1.2 Progress Made: For Marine Renewable Energy Industry .......................................................................... 17 3.2 KEY LESSONS LEARNED ........................................................................................................................................ 17

4 FURTHER INFORMATION ................................................................................................................................ 18

4.1 SCIENTIFIC PUBLICATIONS .................................................................................................................................... 18 4.2 WEBSITE & SOCIAL MEDIA ................................................................................................................................... 18

5 REFERENCES ................................................................................................................................................... 18

6 APPENDICES ................................................................................................................................................... 18

6.1 STAGE DEVELOPMENT SUMMARY TABLE ................................................................................................................ 18 6.2 ANY OTHER APPENDICES ........................................................................................ ERROR! BOOKMARK NOT DEFINED.


Rev. 01, 17‐Jan‐2013 of 19

1 INTRODUCTION & BACKGROUND

1.1 INTRODUCTION The Hydraulics & Maritime Research Centre, UCC is a small scale testing facility in Cork, Ireland. The Ocean Wave Basin has a water depth of 1.0m. The periods generated by the wave maker range from 2.0 seconds to 0.66 seconds with wave heights significantly in excess of 0.2m. The Cork wave basin also allows polychromatic wave generation with good absorption capability both at the end of the wave tank and at the wave maker. The tank has a fully automatic data acquisition system with A/D converter and motion tracking cameras and software. The Wavetrain device had been tested previously at the QUB, Belfast and Portaferry facilities during initial concept validation work in the period June –September 2010. The Marinet funded tests at HMRC are designed to measure device motions and forces for a range of sea conditions to provide validation evidence for the numeric model.

1.2 DEVELOPMENT SO FAR

1.2.1 Stage Gate Progress Previously completed: Planned for this project:

STAGE GATE CRITERIA Status Stage 1 – Concept Validation • Linear monochromatic waves to validate or calibrate numerical models of the system (25 – 100 waves) • Finite monochromatic waves to include higher order effects (25 –100 waves)

• Hull(s) sea worthiness in real seas (scaled duration at 3 hours) • Restricted degrees of freedom (DofF) if required by the early mathematical models • Provide the empirical hydrodynamic co‐efficient associated with the device (for mathematical modelling tuning)

• Investigate physical process governing device response. May not be well defined theoretically or numerically solvable

• Real seaway productivity (scaled duration at 20‐30 minutes)

• Initially 2‐D (flume) test programme • Short crested seas need only be run at this early stage if the devices anticipated performance would be significantly affected by them • Evidence of the device seaworthiness

• Initial indication of the full system load regimes

Stage 2 – Design Validation • Accurately simulated PTO characteristics

• Performance in real seaways (long and short crested) • Survival loading and extreme motion behaviour.

• Active damping control (may be deferred to Stage 3)

• Device design changes and modifications

• Mooring arrangements and effects on motion

• Data for proposed PTO design and bench testing (Stage 3)

• Engineering Design (Prototype), feasibility and costing

• Site Review for Stage 3 and Stage 4 deployments

• Over topping rates


Rev. 01, 17‐Jan‐2013 of 19

STAGE GATE CRITERIA Status Stage 3 – Sub‐Systems Validation • To investigate physical properties not well scaled & validate performance figures

• To employ a realistic/actual PTO and generating system & develop control strategies

• To qualify environmental factors (i.e. the device on the environment and vice versa) e.g. marine growth, corrosion, windage and current drag

• To validate electrical supply quality and power electronic requirements.

• To quantify survival conditions, mooring behaviour and hull seaworthiness

• Manufacturing, deployment, recovery and O&M (component reliability)

• Project planning and management, including licensing, certification, insurance etc.

Stage 4 – Solo Device Validation • Hull seaworthiness and survival strategies

• Mooring and cable connection issues, including failure modes

• PTO performance and reliability

• Component and assembly longevity

• Electricity supply quality (absorbed/pneumatic power‐converted/electrical power)

• Application in local wave climate conditions

• Project management, manufacturing, deployment, recovery, etc

• Service, maintenance and operational experience [O&M]

• Accepted EIA

Stage 5 – Multi‐Device Demonstration • Economic Feasibility/Profitability

• Multiple units performance

• Device array interactions

• Power supply interaction & quality

• Environmental impact issues

• Full technical and economic due diligence

• Compliance of all operations with existing legal requirements

1.2.2 Plan for this Access The test programme was conducted in two sessions on 10th and 11th January 2013. The models were built over the Christmas break in December 2012 and fitted in HMRC, Cork with suitable pressure sensors and the load sensor in the period 7th to 9th January.

Objectives Following the ‘Development Protocol’ the objectives for this access fall within TRL 1 – Confirmation of Operation and TRL 2 Performance Convergence. During the trials verification of the design variables and physical process is completed and the physical process of the motion of the Wavetrain device and the power take‐off mechanism are validated together with obtaining information to validate and calibrate the mathematical model damping effect and phase. Logarithmic Decrement tests were used to determine the effective damping coefficient and real generic sea tests used to gain information on the PTO damping, natural periods, power absorption characteristics and wave‐device response phase relationships.


Rev. 01, 17‐Jan‐2013 of 19

The outputs that will be determined include the device stability and motion response amplitude operators. Pressure/force, velocity RAO’s with phase diagrams, and power conversion characteristic time histories. In addition evaluation of the test video is expected to reveal hull seaworthiness, any excessive rotations or submergence. The water surface abeam of the device modules was also measured and recorded with the other data. The objective was to test for a range of monochromatic wave periods the individual module motions while simultaneously measuring the load in the connecting tubular struts. These tests were repeated for three different wave amplitudes of 5, 10 and 20mm, (0.4, 0.8 and 1.6m at full scale). Following this a number of tests were to be carried out using various polychromatic Bretschneider wave spectral forms with small amplitude waves. A sequence of polychromatic Bretschneider wave spectral forms with Cosine2 and Cosine8 spreading functions were undertaken to complete the programme of work.

Primary Scale The primary scale of the tests was 1:80.

Facility The HMRC facility is a 3D basin for use with scales 1:25 to 1:100

2 OUTLINE OF WORK CARRIED OUT

2.1 SETUP

Figure 2: Setup of model at HMRC wave basin with motion tracking system

The model of the Wavetrain device was purpose built for this study at a scale of 1 in 80th and was made from HDPE quadrangular sections. The floating chamber was filled with closed‐cell polyurethane foam to maintain buoyancy should the upper part of the model be temporarily submerged. As shown above the design consists of three floating bodies connected to each other, with the leading device connected to a floating buoy. The three modules are connected by inclined tubular struts with universal joints at each end. These tubes are pivoted at the back of each module close to the water line and connected to the front toe of the module immediately behind. The first module in this chain is connected through the same tubular struts to a cylindrical floating buoy. On each side an elastic cable


Rev. 01, 17‐Jan‐2013 of 19

connection is made, which maintains, when acting against the module’s natural hydrostatic stiffness in pitch a constant spacing between the lead buoy and the last module. The two middle modules are free to move along this connection, thus giving almost unrestricted heave and surge of each device. The floating cylindrical buoy is restricted in terms of surge through a catenary mooring chain system, which connects to a fixed mooring point on the tank floor. The last device is connected through a long and almost horizontal mooring line to a mooring point at the rear of the tank to maintain device alignment when no waves are present. A very low stiffness spring connection allows low surge restraint and almost unrestricted heave motion. Following this initial phase the model was prepared for testing with three suitable pressure sensors and a set of six twin‐wire wave probes, one on each of the inclined internal water columns. In addition four light reflective spheres were attached to each module to facilitate the individual motion tracking together with a miniature force transducer installed in one of the tubular struts.

Figure 3: Close up of a module with the reflective motion tracking system


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Figure 4: Close up of the force transducer system integrated with the tubular strut The summary table for the Free Oscillation tests is given below. In the third test the solo device was floating in a more upright manner at an angle of 47 degrees resulting in a shifted shorter natural period in view of the larger resolved area of the water plane and hence larger hydrostatic stiffness. Model Natural

Period Model Natural Frequency

Full Scale Natural Period

Damping Coefficient

1. Free Oscillation Module 2 1.09 0.914 9.75 0.232 2. Free Oscillation Module 3 1.03 0.976 9.17 0.114 3. Free Oscillation Solo Device 0.844 1.19 7.55 0.165

Table 2.1 Free Oscillation Tests

The following Table gives the series of calibrated frequencies for use with tank testing. The actual model periods have also been transcribed to full scale periods for a model scale of 1:80. These frequencies were used for all of the monochromatic testing in HMRC. Tank Frequency Set Model Scale

Period Model Scale Frequency

Full Scale Period

1. F2 1.79 0.56 16.0 2. F3 1.59 0.63 14.2 3. F4 1.45 0.69 13.0 4. F5 1.33 0.75 11.9 5. F6 1.23 0.81 11.0 6. F7 1.14 0.88 10.2 7. F8 1.06 0.94 9.48 8. F9 1.00 1.00 8.94 9. F10 0.80 1.25 7.15 10. F11 0.69 1.44 6.17

Table 2.2 Tank Calibrated Frequency Set


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The following monochromatic test sets were completed for the Wavetrain device. The Table provides information on the test parameters but not on the output results which will require more time to compute and analyse. The test code system was based on M/R _ Fn _ Hn where M/R denotes Monochromatic or Polychromatic waves, Fn denotes the model scale frequency set and Hn denotes model scale wave height in mm. Video records were taken for each data set. Total test times were approximately 1 minute after allowance for reaching steady state conditions. Test Set Date Model Scale Period Model Scale Frequency Full Scale Period Model Scale Waveheight Full Scale Waveheight

M_F2_H10 10/01/13 1.79 0.56 16.0 10mm 0.8m M_F3_H10 10/01/13 1.59 0.63 14.2 10mm 0.8m M_F4_H10 10/01/13 1.45 0.69 13.0 10mm 0.8m M_F5_H10 10/01/13 1.33 0.75 11.9 10mm 0.8m M_F6_H10 10/01/13 1.23 0.81 11.0 10mm 0.8m M_F7_H10 10/01/13 1.14 0.88 10.2 10mm 0.8m M_F8_H10 10/01/13 1.06 0.94 9.48 10mm 0.8m M_F9_H10 10/01/13 1.00 1.00 8.94 10mm 0.8m M_F10_H10 10/01/13 0.80 1.25 7.15 10mm 0.8m M_F11_H10 10/01/13 0.69 1.44 6.17 10mm 0.8m M2_F2_H10 11/01/13 1.79 0.56 16.0 10mm 0.8m M2_F3_H10 11/01/13 1.59 0.63 14.2 10mm 0.8m M2_F4_H10 11/01/13 1.45 0.69 13.0 10mm 0.8m M2_F5_H10 11/01/13 1.33 0.75 11.9 10mm 0.8m M2_F6_H10 11/01/13 1.23 0.81 11.0 10mm 0.8m M2_F7_H10 11/01/13 1.14 0.88 10.2 10mm 0.8m M2_F8_H10 11/01/13 1.06 0.94 9.48 10mm 0.8m M2_F9_H10 11/01/13 1.00 1.00 8.94 10mm 0.8m M2_F10_H10 11/01/13 0.80 1.25 7.15 10mm 0.8m M2_F11_H10 11/01/13 0.69 1.44 6.17 10mm 0.8m M3_F2_H20 10/01/13 1.79 0.56 16.0 20mm 1.6m M3_F3_H20 10/01/13 1.59 0.63 14.2 20mm 1.6m M3_F4_H20 10/01/13 1.45 0.69 13.0 20mm 1.6m M3_F5_H20 10/01/13 1.33 0.75 11.9 20mm 1.6m M3_F6_H20 10/01/13 1.23 0.81 11.0 20mm 1.6m M3_F7_H20 10/01/13 1.14 0.88 10.2 20mm 1.6m M3_F8_H20 10/01/13 1.06 0.94 9.48 20mm 1.6m


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M3_F9_H20 10/01/13 1.00 1.00 8.94 20mm 1.6m M3_F10_H20 10/01/13 0.80 1.25 7.15 20mm 1.6m M3_F11_H20 10/01/13 0.69 1.44 6.17 20mm 1.6m M4_F2_H40 11/01/13 1.79 0.56 16.0 40mm 3.2m M4_F2_H40 11/01/13 1.59 0.63 14.2 40mm 3.2m M4_F2_H40 11/01/13 1.45 0.69 13.0 40mm 3.2m M4_F2_H40 11/01/13 1.33 0.75 11.9 40mm 3.2m M4_F2_H40 11/01/13 1.23 0.81 11.0 40mm 3.2m M4_F2_H40 11/01/13 1.14 0.88 10.2 40mm 3.2m M4_F2_H40 11/01/13 1.06 0.94 9.48 40mm 3.2m M4_F2_H40 11/01/13 1.00 1.00 8.94 40mm 3.2m M4_F2_H40 11/01/13 0.80 1.25 7.15 40mm 3.2m M4_F2_H40 11/01/13 0.69 1.44 6.17 40mm 3.2m Polychromatic tests included long crested trials and short‐crested trials with two spreading functions, Cosine2 and Cosine8. The tests lasted for 8192 samples. Bretschneider Date Spectral type Model Scale Hs Full Scale Hs Model scale Tz Full Scale Tz

B3 – Long Crested 11/01/13 Bretschneider 20mm 1.6m 0.86 7.7 B16 – Long Crested 11/01/13 Bretschneider 20mm 1.6m 1.07 9.6 B17 – Long Crested 11/01/13 Bretschneider 20mm 1.6m 1.29 11.5 B11 – Long Crested 11/01/13 Bretschneider 20mm 1.6m 1.43 12.8 B1 – Long Crested 11/01/13 Bretschneider 40mm 3.2m 0.57 0.86 B18 – Long Crested 11/01/13 Bretschneider 40mm 3.2m 1.29 11.5 B19 – Long Crested 11/01/13 Bretschneider 50mm 4.0m 0.64 5.7 B1 – Cosine 2 11/01/13 Bretschneider 40mm 3.2m 0.57 0.86 B1 – Cosine 8 11/01/13 Bretschneider 40mm 3.2m 0.57 0.86 B3 – Cosine 8 11/01/13 Bretschneider 20mm 1.6m 0.86 7.7 B11 – Cosine 8 11/01/13 Bretschneider 20mm 1.6m 1.43 12.8 B19 – Cosine 8 11/01/13 Bretschneider 50mm 4.0m 0.64 5.7 B19 – Cosine 2 11/01/13 Bretschneider 50mm 4.0m 0.64 5.7 B11 – Cosine 2 11/01/13 Bretschneider 20mm 1.6m 1.43 12.8 B18 – Cosine 2 11/01/13 Bretschneider 40mm 3.2m 1.29 11.5


Rev. 01, 17‐Jan‐2013 of 19

2.2 TESTS

2.2.1 Test Plan The methodology for this new study included some initial floating tests at the Cork facility; the key objectives were to test the ballasting and balancing of the devices and to prepare the mooring arrangement. A few impulse and natural oscillatory decay tests were conducted to gain insight into the applied pneumatic damping. A total of 65 different test configurations were tested in HMRC during this period. An overview of the basic parameters tested is given below:

• Range of monochromatic seas with wave periods covering 6.17s, 7.15s, 8.94s, 9.48s, 10.2s, 11.0s, 11.9s, 13.0s, 14.2s & 16.0s (all to full scale)

• A single damping condition corresponding to 8mm orifice opening was used throughout the full range of tests

• Various Bretschneider Sea States were used in the second series of tests with wave heights Hs = 20mm, Tz = 0.86, 1.07,1.29 & 1.43s, Hs = 40mm, Tz = 0.57 & 1.29 and Hs = 50mm, Tz = 0.64 at model scale

• Bretschneider Sea States with Cos2 spreading functions at Hs = 20mm & Tz = 1.43, Hs = 40mm & Tz = 0.57 & 1.29, and Hs = 50mm & Tz = 0.64

• Bretschneider Sea States with Cos8 spreading functions at Hs = 20mm & Tz = 0.86 & 1.43 and Hs = 40mm & Tz = 0.57

2.3 RESULTS XZ Motions This Post‐Access report will not discuss the time series analysis in full detail. However, preliminary results for the XZ motion plots for the three modules are provided for three indicative monochromatic frequencies.

Figure 5: XZ plane motion plots for modules 1‐3 at 11.9s full scale


Rev. 01, 17‐Jan‐2013 of 19

Figure 6: XZ plane motion plots for modules 1‐3 at 9.48s full scale (peak response)

Figure 7: XZ plane motion plots for modules 1‐3 at 7.15s

It may be seen in Figure 6, which corresponds to the module natural period and peak response that the module is moving accurately on the inclined plane corresponding to the angle of the inertia tubes, (approximately 45degrees). At frequencies above and below that of the peak motion response the motion is less linear and the power modules respond with quasi‐elliptical motion although the lead module and the trailing module have more complicated responses. The response at the natural period and peak response is very close to that assumed in the numerical model.

Strut Forces Strut loads for the natural period in waves of 40mm model scale height (3.2m full scale) are shown in Figure 8. This is a significant wave height corresponding to storm conditions.

Figure 8: Tubular strut axial load plot at 9.48s full scale giving a peak load of 83.5t.

The model load varies from +0.7N to – 1.5N giving a peak load at full scale of 83.5t.


Rev. 01, 17‐Jan‐2013 of 19

2.4 ANALYSIS & CONCLUSIONS The preliminary results are very encouraging and indicate that the power module motions are indeed in the form anticipated in the basic numerical model. The free oscillation tests have provided new information previously not available on the equivalent damping factor applied by the power take‐off system at model scale. This has been used in the numerical model to replicate the XZ motion RAO’s which correlate closely with the measured model tests. This evidence provides some validation of the numerical model whose results have been used to predict full scale capture performance. There are significant viscous losses at model scale (1:80) that conceal the likely full scale capture performance. Further quantification of the capture performance at larger model scale (say 1:25) would help to isolate and quantify these losses. These tests pave the way for TRL 3 trials to commence Device Optimisation including Hull Geometry, Component Configuration, Power Take‐off Characteristics and Design Engineering/Naval Architecture.

3 MAIN LEARNING OUTCOMES

3.1 PROGRESS MADE The Plan for this Access given in Section 1.2.1 may be used to assess the progress made during these trials. The particular Stage 1 – Concept Validation investigations planned for this set of tests included:

• Finite monochromatic waves to include higher order effects • Investigate the physical process governing device response (may not be well defined theoretically or

numerically solvable • Real seaway productivity • Evidence of device seaworthiness • Initial indication of the full system load regimes

While the Stage 2 – Design Validation investigations included:

• Mooring arrangements and effects on motion All of these aspects have been furthered successfully during these trials. Three series of monochromatic wave tests have been completed with common frequencies and increasing wave amplitude that will provide evidence of higher order effects. The physical process governing the device response has been demonstrated to be a linear response in the inclined plane of the water inertia tubes with surge and heave coupled in phase has been illustrated at the natural period combined with some elliptical motions at other frequencies. The aim will be to broaden the device linear inclined plane response as far as possible through geometry changes and different sized devices. Out of phase motions in surge or heave may lead to some un‐recoverable energy losses. The productivity of the device in real seaways may be calculated from the polychromatic tests of which there are three specific types:

• Long‐crested polychromatic Bretschneider at Hs of 20mm, 40mm and 50mm. • Short‐crested polychromatic Bretschneider with Cosine 2 spreading function • Short‐crested polychromatic Bretschneider with Cosine 2 spreading function


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This analysis will follow in due course. The video taken of each test will provide evidence of device seaworthiness. Similarly, the loads measured in the tubular strut will provide an indication of full system load regimes for detailed engineering design. The motion results and video recordings will provide evidence of the effectiveness of the mooring system and its impact on device motions.

3.1.1 Progress Made: For This UserGroup or Technology The tests have provided a comprehensive data set to validate the Wavetrain design concept. Already, it is apparent that the device motions and loads are largely as predicted and that it has good potential to produce energy in a competitive manner. This evidence supports the observations made by the consultants Black & Veatch who independently reviewed the concept under the auspices of the Carbon Trust Marine Energy Challenge Programme.

3.1.1.1 Next Steps for Research or Staged Development Plan – Exit/Change & Retest/Proceed? The next steps involve a concerted period of analysis of the accumulated data to validate the concept and determine the fundamental engineering design parameters. Already, it is clear that the Wavetrain concept is sufficiently competitive to justify further and prolonged testing at 1:80 and 1:25 scale. Further tuning of the fundamental design parameters of mass, water plane area, inclination angle and external boundary geometry are required to improve the system performance in off‐resonance conditions. However, the device capture factor bandwidth has already been demonstrated to be exceptional both in the numerical model and physical scale model results. This bandwidth is enhanced compared to isolated devices and benefits from the rigid inclined link connections that help to confine the power module motions in the inclined plane of the water inertia tubes.

3.1.2 Progress Made: For Marine Renewable Energy Industry The Wavetrain device concept is a development of work carried out in QUB to examine pneumatic power take‐off using a Wells turbine from the IPS buoy rather than the original hydraulic system. The results of using inclined rigid links to connect a series of power modules has also been demonstrated as being beneficial to the overall device capture performance. Further work is now required to understand the interactions between the device power modules (point absorbers in a linear array). This work is initially required in the numerical modelling which may subsequently be validated with further device testing at 1:80 and 1:25 scale. The numerical hydrodynamic modelling of the Wavetrain device needs to be enhanced to take account of a series of interconnected bodies rather than the isolated module hydrodynamics used to date. “q” factors for the individual power modules need to be determined for different excitation frequencies.

3.2 KEY LESSONS LEARNED The following observations may be made on the success of the testing at HMRC.

• Previous experience is valuable in preparing models for testing prior to arrival at the wave tank and in the design of features necessary for calibration of transducers

• Set‐up of the instrumentation (wave probes, force transducers, pressure transducers, motion sensors, etc) can take several days even when the models are well prepared in advance

• Subsequent testing can take place at a fast pace once all the instrumentation is established and calibrated • Analysis of the copious quantities of test data is by far the most time consuming element of the test

sequence. The development in advance of MatLab or Excel spreadsheets to receive test data and provide key outputs would be a significant advantage for future testing. In this respect parametric studies could be analysed in real time and tests modified to pursue specific characteristics. However, this requires detailed interaction between test establishments and the users in advance of use of the facility.


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4 FURTHER INFORMATION

4.1 SCIENTIFIC PUBLICATIONS List of any scientific publications made (already or planned) as a result of this work:

• A paper on the motions of the Wavetrain power modules is possible for presentation at one of the international wave energy conferences.

4.2 WEBSITE & SOCIAL MEDIA Website: none YouTube Link(s): none LinkedIn/Twitter/Facebook Links: none Online Photographs Link: none

5 REFERENCES IP protection has limited the amount of information released to the public domain on the Wavetrain device. The main reference is not available in the public domain – but could be made available on request to the author. It is the independent report on the Wavetrain device issued by Black & Veatch under the auspices of the Carbon Trust.

6 APPENDICES

6.1 STAGE DEVELOPMENT SUMMARY TABLE The table following offers an overview of the test programmes recommended by IEA‐OES for each Technology Readiness Level. This is only offered as a guide and is in no way extensive of the full test programme that should be committed to at each TRL.


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