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Infrastructure Access Report

Infrastructure: UCC-HMRC Ocean Wave Basin

User-Project: W2P Mooring and wind

Hybrid Floating Platforms in Deep Waters (Phase III) and Multipurpose Wave Energy Converters

Pelagic Power AS/EnerOcean SL

Marine Renewables Infrastructure Network

Status: Final Version: 04 Date: 03-Mar-2015

EC FP7 “Capacities” Specific Programme

Research Infrastructure Action

Infrastructure Access Report: W2P Mooring and wind

Final draft

ABOUT MARINET MARINET (Marine Renewables Infrastructure Network for emerging Energy Technologies) is an EC-funded network of research centres and organisations that are working together to accelerate the development of marine renewable energy - wave, tidal & offshore-wind. The initiative is funded through the EC's Seventh Framework Programme (FP7) and runs for four years until 2015. The network of 29 partners with 42 specialist marine research facilities is spread across 11 EU countries and 1 International Cooperation Partner Country (Brazil). MARINET offers periods of free-of-charge access to test facilities at a range of world-class research centres. Companies and research groups can avail of this Transnational Access (TA) to test devices at any scale in areas such as wave energy, tidal energy, offshore-wind energy and environmental data or to conduct tests on cross-cutting areas such as power take-off systems, grid integration, materials or moorings. In total, over 700 weeks of access is available to an estimated 300 projects and 800 external users, with at least four calls for access applications over the 4-year initiative. MARINET partners are also working to implement common standards for testing in order to streamline the development process, conducting research to improve testing capabilities across the network, providing training at various facilities in the network in order to enhance personnel expertise and organising industry networking events in order to facilitate partnerships and knowledge exchange. The aim of the initiative is to streamline the capabilities of test infrastructures in order to enhance their impact and accelerate the commercialisation of marine renewable energy. See www.fp7-marinet.eu for more details.

Partners

Ireland University College Cork, HMRC (UCC_HMRC)

Coordinator

Sustainable Energy Authority of Ireland (SEAI_OEDU)

Denmark Aalborg Universitet (AAU)

DanmarksTekniskeUniversitet (RISOE)

France EcoleCentrale de Nantes (ECN)

InstitutFrançais de Recherche Pour l'Exploitation de la Mer (IFREMER)

United Kingdom National Renewable Energy Centre Ltd. (NAREC)

The University of Exeter (UNEXE)

European Marine Energy Centre Ltd. (EMEC)

University of Strathclyde (UNI_STRATH)

The University of Edinburgh (UEDIN)

Queen’s University Belfast (QUB)

Plymouth University(PU)

Spain Ente Vasco de la Energía (EVE)

Tecnalia Research & Innovation Foundation (TECNALIA)

Belgium 1-Tech (1_TECH)

Netherlands Stichting Tidal Testing Centre (TTC)

StichtingEnergieonderzoek Centrum Nederland (ECNeth)

Germany Fraunhofer-GesellschaftZurFoerderung Der AngewandtenForschungE.V (Fh_IWES)

Gottfried Wilhelm Leibniz Universität Hannover (LUH)

Universitaet Stuttgart (USTUTT)

Portugal Wave Energy Centre – Centro de Energia das Ondas (WavEC)

Italy UniversitàdegliStudidi Firenze (UNIFI-CRIACIV)

UniversitàdegliStudidi Firenze (UNIFI-PIN)

UniversitàdegliStudidellaTuscia (UNI_TUS)

ConsiglioNazionaledelleRicerche (CNR-INSEAN)

Brazil Instituto de PesquisasTecnológicas do Estado de São Paulo S.A. (IPT)

Norway SintefEnergi AS (SINTEF)

NorgesTeknisk-NaturvitenskapeligeUniversitet (NTNU)

http://www.fp7-marinet.eu/


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DOCUMENT INFORMATION Title Hybrid Floating Platforms in Deep Waters (Phase III) and Multipurpose Wave Energy

Converters

Distribution Public

Document Reference MARINET-TA1-W2P Mooring and wind

User-Group Leader, Lead Author

Reza Hezari Pelagic Power AS Pedro Mayorga EnerOcean SL

User-Group Members, Contributing Authors

Jan Hanssen Pelagic Power AS Javier Fernández EnerOcean SL Miguel Ángel Jaime EnerOcean SL

Infrastructure Accessed: UCC-HMRC Ocean Wave Basin

Infrastructure Manager (or Main Contact)

Florent Thiebaut

REVISION HISTORY Rev. Date Description Prepared by

(Name) Approved By Infrastructure

Manager

Status (Draft/Final)

01 10/2014 First draft Javier Fernandez Draft

02 12/2014 Revised draft Reza Hezari Draft

03 02/2015 Final draft Pedro Mayorga Final draft


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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.


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EXECUTIVE SUMMARY This was the third access granted to this User Group under Marinet program. Thanks to the practical experience gained from the previous tests and to the acquired knowledge on the system, it was possible to perform a high number of tests in different configurations. The investigation can be divided in two parts: the first part includes the characterization of the motions of the improved platform with and without aqua-culture activities. In this case, the influence on the mooring forces is also analysed. The second covers a detailed analysis of the performance of the new improved WECs resulted from considerations from previous laboratory tests. The WECs, in scale 1:30, were fixed to the bridge over the tank and were highly instrumented. The PTO was simulated and it was possible to test preliminary control strategies and calculate the corresponding efficiency under regular and irregular waves and different wave directions. The results were satisfactory and will allow further improvements in the iterative design loop of the W2Power concept.


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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 ............................................................................................................................... 9

2 OUTLINE OF WORK CARRIED OUT ..................................................................................................................... 10

2.1 SETUP ....................................................................................................................................................... 10 2.1.1 W2Power ............................................................................................................................................. 10 2.1.2 Wave Energy Converter ........................................................................................................................ 12

2.2 TESTS ........................................................................................................................................................ 14 2.2.1 Sea States of Irregular Waves ............................................................................................................... 14 2.2.2 First round Tests ................................................................................................................................... 14 2.2.3 Second round tests ............................................................................................................................... 15 2.2.4 Third round tests .................................................................................................................................. 16

2.3 RESULTS .................................................................................................................................................... 17 2.3.1 W2Power Platform ............................................................................................................................... 17 2.3.2 Wave Energy Converters ...................................................................................................................... 20

2.4 ANALYSIS & CONCLUSIONS ............................................................................................................................ 21

3 MAIN LEARNING OUTCOMES ............................................................................................................................ 22

3.1 PROGRESS MADE ......................................................................................................................................... 22 3.1.1 Progress Made: For This User-Group or Technology .............................................................................. 22

3.2 KEY LESSONS LEARNED .................................................................................................................................. 22

4 FURTHER INFORMATION .................................................................................................................................. 23

4.1 SCIENTIFIC PUBLICATIONS .............................................................................................................................. 23 4.2 WEBSITE &SOCIAL MEDIA ............................................................................................................................. 23

5 REFERENCES ...................................................................................................................................................... 23

6 APPENDICES ...................................................................................................................................................... 23

6.1 STAGE DEVELOPMENT SUMMARY TABLE ........................................................................................................... 23


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1 INTRODUCTION& BACKGROUND

1.1 INTRODUCTION W2Power is a novel hybrid floating platform for wind and wave energy utilisation in deep water areas. It consists of a deckless ultra-lightweight triangular semi-submersible platform carrying two standard offshore wind turbines and three linear arrays of wave energy converters. The development is led by a Norwegian SME’s – Pelagic Power AS and a Spanish SME EnerOcean, with some additional evaluation and predesign by Acciona and NTNU in MARINA project. Pelagic owns all the IP and had previously brought the wave energy technology originally used to the level of open sea testing at 1:3 scales. Mobilising wave energy resources in addition to the wind resources enables the delivery of renewable electricity also when the wind is low and provides better economics compared to adding more wind capacity. The platform is anchored by one semi-taut simplified swivel type mooring at the bow (front) column and two slack moorings at the aft so that it always faces the wind (“wind-vanning”). The tests at this phase of development are focussed on the new design of point absorbers installed on the three sides of the platform. The idea for this more efficient design is the results of previous set of tests, realized under Marinet program and is part of an iterative design process aimed at optimizing the different components of the W2Power platform and assessing its performance as a multi-energy-resource harvest device. For this purpose, the wave absorbers are modelled in good detail with simulated PTO so to allow testing of different control strategies and direct measurement of performance. In addition to that, in collaboration with the FP7 TROPOS project, the Platform has inspired its combination with other non-energy related activities, such as aquaculture. For this purpose, the tests presented in this report will also investigate the influence of a fish net and of an algae net attached to the W2Power platform itself. In particular, the influence on moorings and on movements will be presented.

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 (DoF) if required by the early mathematical models

Provide the empirical hydrodynamic coefficient 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


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STAGE GATE CRITERIA Status

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

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


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1.2.2 Plan For This Access W2Power has been combined with a fish-cage and its design modified inside TROPOS project by EnerOcean in collaboration with Pelagic Power. The main objectives of W2Power model testing are to:

Estimate the extreme value responses in terms of global motion and drift forces.

Adding measurements of mooring forces.

Validate the function of the turret mooring with turbines running in normal operating conditions modified by the presence of the fish cage. This includes investigation of the influence from oblique seas.

Observe responses in normal operating conditions with aquaculture elements attached. The WECs tested in this access have been designed for combine wind and wave in W2Power platform. These WECs are also proposed for installation in ports. The main objectives of WEC model testing are to:

Test different control laws to maximize efficiency depending sea state.

Obtain efficiency at 55 degrees (angle of W2Power platform).

Adding boundary conditions as wall or anti-reflective behind converters.


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2 OUTLINE OF WORK CARRIED OUT

2.1 SETUP This report includes three rounds of completed tests that are:

1. 21st to 25th April 2014: Tests on W2Power model with final mooring design, fish cage and algae production system.

2. 9th to 13th June 2014: Tests on W2Power model with different angles between wave front and thrust of wind. 3. 28thJuly to 15th August 2014: Tests on (multipurpose WEC) model with (based in PTO of pitch) torque control.

The instrumentation used is:

3 Load sensors, (2 pounds and 10 pounds)in the mooring lines

3 Resistive wave probes

6 DoF Motion Capturing System (Qualisys)

3 PIC microcontrollers and 3 servo-controllers of DC motors (for the simulation of Power Take-Off system)

Desktop PC for control of PIC microcontrollers (control law)

Under-water video camera

2.1.1 W2Power The model of 1/100 scale was manufactured in Málaga, Spain, with PVC pipes of equivalent dimensions and thicknesses depending of equivalent weights in all its parts (Fig. 1). It has been used in the first and second round of the Marinet supported tests. For this set of tests in Cork, the bottom central girder has been removed to allow the installation of the fish-cage model.

Figure 1 – Original W2Power platform

A preliminary catenary mooring design with 3 lines (3 lines 5.65 meters long, 120 degrees between lines) as used. The three lines were connected to a swivel that was fixed to the front column. The platform is designed to be wind-vanning so it rotates depending on the wind direction to orient the wind turbines in the correct position (Fig. 2).


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Figure 2 – Behaviour of W2Power platform

Within the TROPOS project the W2Power concept was selected to serve as baseline concept for the desired satellite modules. The most important criterion for this selection was the possibility of synergetic effects with the aquaculture activities. W2Power is suitable for this purpose as it allows the first conceptual implementation of a future sized fish-cage and algae production unit. The proposed configuration for fish cage and seaweed production units are shown in Fig.3- and their model in the laboratory is shown in Fig. 4.

Figure 3–Representation of the fish-cage and algae production unit

Figure 4 – Left: Detail of mooring system with load cells and fish-cage. Right: Overview of algae production unit


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To reproduce the wind thrust on wind turbines we used a set of pulleys and weights (Figure 5, Left) connected to the mounting point of the nacelle by fishing line. This configuration exerts a constant force equivalent to a given wind speed in the same direction. The equivalent mass was calculated for Vestas V112, 3.3 MW (Fig. 5, right).

Figure 5–Left: Detail of pulleys and weights. Right: Equivalent mass of thrust force.

2.1.2 Wave Energy Converter The model of WEC in scale1:30 was manufactured in Málaga, Spain. The floater was made with PVC material and thin plates of lead material were used to adjust the weight. The PTO system has been simulated with a DC motor for toque control. PIC microcontrollers control the DC motor and measure torque and position with an encoder. The computer sends the torque desired and receives the measurements by serial communication. This allows direct measurement of the device performance. The modelled Power Take-Off system used in the tests and described above was built with no submerged or near water electronic components. The total torque multiplier is 185 theoretical between motor torque and floater torque. The angular position is measured by incremental encoder of 2.000 PPR. The DC motor of 180 W is here sufficient to reproduce the behaviour of power take-off system. For torque control was activated by a C program in Linux and transmitted via serial communication. Relative data acquisition was also using the same communication method. Two control laws were implemented to maximize the power production:

Quadratic damping law

o

Quadratic damping law + Phase control o The phase control can be summarized as: if the derivative of angular velocity is zero, then block the

floater in that position a short time period. After, unblock (quadratic damping law). This increases the weight or buoyancy of the floater.


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Figure 6–WECs connected to controlled motors

Secondary objective of WEC model tests is adding boundary conditions behind the models for different applications, such as, for example, breakwaters application. Figure 8 show an anti-reflective breakwater fixed to tank floor. This exercise has been useful to investigate possible alternative applications of the point absorbers under development and to understand better their behaviours under more complex sea conditions.

Figure 7–Boundary conditions. Anti-reflective behind WECs


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2.2 TESTS

2.2.1 Sea States of Irregular Waves The sea states chosen for irregular waves are the same of the previous set of tests conducted before in previous Marinet access. These are presented in Table 1. For WECs, also the same sea states have been chosen, however the scales are different (1:30 instead of1:100) and are listed in Table 2.

Table 1 – Sea states of JONSWAP spectrum for W2Power

Operational Survival

Sea State Hs[m] Tp [s] Gamma Sea State Hs [m] Tp [s] Gamma

A 0.75 8.5 1 A 3 7 3.3

B 0.75 11.5 1 B 4.5 8 3.3

C 0.75 14.5 1 C 6.5 10 3.3

D 2.25 8.5 1 D 5.5 12.5 3.3

E 2.25 11.5 1 E 5 15 3.3

F 2.25 14.5 1 F 4.5 8 1

G 3.75 8.5 1 G 4.5 8 5

H 3.75 11.5 1 H 5.5 12.5 1

I 3.75 14.5 1 I 5.5 12.5 5

Table 2 – Sea states of JONSWAP spectrum for WECs

Operations

Sea State Hs[mm] Tp [s] Gamma

A 25 1.6 1

B 25 2.1 1

C 75 1.6 1

D 75 2.1 1

E 125 1.6 1

F 125 2.1 1

2.2.2 First round Tests The first round of tests was regular and irregular waves with and without the fish-cage or algae net (tables 3-5).

Table 3–Regular tests on W2Power model for different operating modes

Wave Period [s]

Total 0.65 0.8 1 1.2 1.4 1.6 1.8

Wave direction Fishcage Algae Wave Amplitude [mm]

35/30/10 40/30/10 50/30/10 46/30/10 42/30/22/10 30/22/10 22/10

0 deg With Without 1/1/1 1/1/1 1/1/1 1/1/1 1/1/1/1 1/1/1 1/1 21

0 deg Without Without 1/0/1 1/0/1 1/0/1 1/0/1 1/0/0/1 1/0/1 1/1 14

0 deg Without With 1/0/0 1/0/0 1/0/0 1/0/0 1/0/0/0 1/0/0 1/0 7

4 6 6 6 7 6 5

Grand Total 42


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Table 4 - Normal tests on W2Pwer model for different operating modes

Wave direction Fishcage Algae Sea State Normal

Total A B C D E F G H I

0 deg With Without 1 1 1 1 1 1 1 1 1 9

0 deg Without Without 1 1 1 1 1 1 6

0 deg Without With 1 1 1 1 1 1 6

3 3 3 1 1 1 3 3 3

Grand Total 21

Table 5 - Survival tests on W2Pwer model for different operating modes

wave direction Fishcage Algae Sea State Survival


0 deg With Without 1 1 1 1 1 1 1 1 1 9

0 deg Without Without 1 1 1 1 1 5

0 deg Without Without 1 1 1 1 1 5

3 3 3 3 3 1 1 1 1

Grand Total 19

2.2.3 Second round tests The second round of tests investigated the platform with fish-cage under different simulated wind conditions, for different wave attack angles in regular and irregular waves (Tables 6-8).

Table 6 - Regular tests on W2Pwer model for different operating modes

Wave Period [s]

Total 0.65 0.8 1 1.2 1.4 1.6 1.8

wave direction Thrust Force

Fishcage Wave Amplitude [mm]

35 40 50 46 42 30 22

0 deg Max Without 1 1 1 1 1 1 1 7

90 deg Max Without 1 1 1 1 1 1 1 7

45 deg Max Without 1 1 1 1 1 1 1 7

45 deg Max With 1 1 1 1 1 1 1 7

45 deg 5.5 m/s With 1 1 1 1 1 1 1 7

90 deg 5.5 m/s With 1 1 1 1 1 1 1 7

90 deg Max With 1 1 1 1 1 1 1 7

7 7 7 7 7 7 7

Grand Total 49


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Table 7 - Normal tests on W2Pwer model for different operating modes


Fishcage Sea State Normal


0 deg Max Without 1 1 1 3



45 deg Max With 1 1 1 3

90 deg Max With 1 1 1 3

0 0 0 0 0 0 5 5 5

Grand Total 15

Table 8 - Survival tests on W2Pwer model for different operating modes


Fishcage Sea State Survival


0 deg Max Without 1 1 1 1 1 5



45 deg Max With 1 1 1 1 1 5

90 deg Max With 1 1 1 1 1 5

5 5 5 5 5 0 0 0 0

Grand Total 25

2.2.4 Third round tests The third and last set of tests was dedicated to the WECs. The varying parameters and the wave conditions are summarized in Tables 9-12.

Table 9 – Control parameters tested for regular waves on WECs in open sea

wave direction

Nº WEC Control Hs [mm] Wave Period [s]

Total 1.2 1.5 1.8 2.2

0 deg 3 Cuadratic 50 16 16 16 16 64

0 deg 3 Cuadratic 100 16 16 16 16 64

0 deg 1 Cuadratic 50 32 32 16 16 96

0 deg 1 Cuadratic 100 32 32 16 16 96

0 deg 1 Cuadratic 150 16 16 16 16 64

55 deg 3 Cuadratic 50 18 18 18 18 72

55 deg 3 Cuadratic 100 18 18 18 18 72

55 deg 3 Cuadratic 150 18 18 18 18 72

0 deg 3 Phase 50 18 18 18 18 72

0 deg 3 Phase 100 18 18 18 18 72

0 deg 3 Phase 150 18 18 18 18 72

220 220 188 188

Grand Total 816


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Table 10 - Control parameters tested for irregular waves on WECs in open sea

Wave direction

Nº WEC Control Sea State Normal

Total A B C D E F

0 deg 3 Cuadratic 5 5 5 5 5 5 30

Grand Total 30

Table 11 – Control parameters tested for regular waves on WECs in port

Mode Nº WEC Control Hs [mm] Wave Period [s]

Total 1.2 1.5 1.8 2.2

Wall 1 Cuadratic 50 18 18 18 18 72

Anti-R 1 Cuadratic 50 18 18 18 18 72

Anti-R 3 Cuadratic 50 18 18 18 18 72

54 54 54 54

Grand Total 216

Table 12 - Control parameters tested for irregular waves on WECs in port

Mode Nº WEC Control Sea State Normal

Total A B C D E F

Anti-R 1 Cuadratic 3 3

Anti-R 3 Cuadratic 5 2 7

8 2 0 0 0 0

Grand Total 10

2.3 RESULTS This section presents some preliminary results of platform motion and other interesting values like the calculated efficiency of WECs. Due to delicate commercial information in this project, only a few data can be shown.

2.3.1 W2Power Platform In order to compare the influence of different aquaculture systems on the platform movements, the figures 9, 10 and 11 show relatives RAO of heave, surge and pitch. From the collected data and for the wave conditions tested, the presence of the fish cage or of the algae net seems not to have a significant influence on the movements of the platform compared to the case without it in the case of heave.


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Figure 8 – Relative RAO for heave of the Base Platform (red) with fish cage (blue) and with algae unit (green)

The RAO for surge and pitch, instead, increase consistently for periods between 9 and 19 seconds, probably as a consequence of the added inertia generated by the fish cage and by the algae net.

Figure 9 – Relative RAO for surge of the Base Platform (red) with fish cage (blue) and with algae unit (green)


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Figure 10- Relative RAO for pitch of the Base Platform (red) with fish cage (blue) and with algae unit (green)

The Figure 11 shows the change in the decay tests as consequence of the presence of the aquaculture systems. We can see a slightly longer response time in the case with fish cage implemented to the platform.

Figure 11 – Free decay surge motion with (blue) and without (red) fish cage attached

Figure 12 shows maximum deviation of yaw angle for all cases.


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Figure 12 – Yaw maximum deviation between still water and running test

2.3.2 Wave Energy Converters The efficiency of the wave energy converters, expressed as capture width ratio (power of converter divided by its width capture / power per meter of sea state) in regular waves for different attack angles is shown in Tables 13 and 14, both with an indicative average for equally probable sea states (this average will be modify for each site specific occurrence of every T and H couple).The highest efficiencies have been calculated for H=3 m and T=6.57 sec, full scale.

Table 13 – Efficiency for optimal control (quadratic damping law) at 0 degrees

Kv 0.3 T (s)

H (m) 1.2 1.5 1.8 2.2 Scale down

Scaled down Full scale 6.57 8.22 9.86 12.05 Full Scale

0.05 1.5 46% 19% 12% 5%

0.1 3 53% 31% 19% 10%

0.15 4.5 39% 36% 25% 10% 25%

Table 14 - Efficiency for optimal control (quadratic damping law) at 55 degrees

Kv 0.3 T (s)

H (m) 1.2 1.5 1.8 2.2 Scale down

Scaled down Full scale 6.57 8.22 9.86 12.05 Full Scale

0.05 1.5 26% 14% 9% 4%

0.1 3 33% 28% 18% 10%

0.15 4.5 30% 33% 20% 11% 20%

The average efficiency of energy production for the tested wave energy converters in irregular wave is similar to that in regular waves.


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Finally, Table 15 shows the average efficiency of production according to different contours conditions for comparison:

1) Free (without anything behind the line of point absorbers) 2) Wall (with a vertical wall i.e. vertical breakwater, behind the point absorbers) 3) Antireflective (with a structure designed to absorb the incoming waves for an antireflective effect behind the

point absorbers)

Table 15 – Efficiency for different boundary conditions (quadratic damping law) at 0 degrees

T (s)

H (m) 1.2 1.5 1.8 2.2 Scale down

CASE Scale down Full scale 6.57 8.22 9.86 12.05 Full Scale

Free 0.05 1.5 39% 28% 23% 16% 27%

Wall 0.05 1.5 113% -2% 27% 86% 56%

Anti-R 0.05 1.5 71% 0% 14% 39% 31%

2.4 ANALYSIS & CONCLUSIONS The main initial conclusions are:

The mooring design was fully validated, both in movement’s restriction and in maximum loads in the mooring lines.

Furthermore the addition of the aquaculture modules doesn’t affect significantly to the performance of the platform in its stability or in inducing higher loads on the mooring lines.

For the loads in the mooring line, it has been verified that the presence of the fish cage and associated drag

load only increased the average load (affecting potential fatigue life of the mooring) but not so much its peak

values.

Neither the RAOs nor natural frequencies have been modified significantly by the used of the validated mooring

design or the presence of the aquaculture modules (fish cage and Algae production module):

For the modification of the platforms RAOs it has been verified that although there is a significant increase of

the RAO for heave and surge at relative short period waves (5 to 8 seconds), its value is still very small and

there is no significant modification of the values for pitch over the range of interest.

When considering the effects over the modification of the natural frequencies of the platform, it has been

verified that there is again no significant modification of the values for Heave and Pitch, however the free

decay behaviour of the platform in surge presents higher damping and smaller damped frequency, but in any

case far enough of any exciting frequency.

When the wind blows in a different direction, than the wave attack angle, this does not affect significantly the production of wind turbines since the waves are only able to deflect the platform with respect to wind a few degrees. For the Wave2Power WECs:

The average power production of each converter in regular and irregular waves conforms to expectations according to the design by EnerOcean and Pelagic Power. This validates the efficiency of the converter as a modular element that can also be used in different applications (such as breakwaters).

Despite the dynamic response of the structure varies depending on the wave attack angle, it was proved that the efficiency of the point absorbers is little affected by wave directionality. This is a good news for a wind vanning platform that is oriented based on dominant wind direction and not perhaps (depending by the case) not optimal wave direction. For the use in ports, the presence of a wall at a certain distance behind the converter can be beneficial as it may increase the efficiency compared to the case without a vertical wall,

this is probably due to the combination of incident and reflected waves exciting the point absorbers.


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3 MAIN LEARNING OUTCOMES

3.1 PROGRESS MADE

3.1.1 Progress Made: For This User-Group or Technology In the first series of MARINET tests, the focus was on two different platform configurations and the selection of the best one based on stability. The results contributed to the selection and decision in further development of the triangular W2Power platform that showed promising results in terms of stability. Also, the test lead to the design of an optimized point absorber to be implemented in later development stages on the platform. The point absorbers selected are rotating around pitch and provide better efficiency than the old vertical heaving buoys. In the second series of tests the focus was the stability performance and behaviour of the improved platform with new WECs in regular and irregular sea conditions, for operational and survival modes. The results showed that the platform continued to be stable with the combination of wind and waves, with a total of 10 converters. In addition, mooring forces were measured for a preliminary mooring configuration. In this third series of test, the influence of the wind and especially of the mooring were the main focuses of the investigations. RAO were calculated for different configurations, with and without aquaculture structures and in different wave conditions, including different wave directions. A big part of the third series of tests in the third access granted under Marinet program, has been dedicated to the calculation of the efficiencies of the improved WECs that have been modelled with PTO and control strategies. The realization of such a model was a big step forward for the W2Power concept. The developers, having proved that the WECs have a good efficiency, took the chance to implement a series of tests of those for different application scenarios, i.e. on breakwaters instead of on the W2Power floating platform. This exercise improved greatly the knowledge on the performance of the WECs and the ability of the group to test in the laboratory and analyse the collected data.

3.2 KEY LESSONS LEARNED The use of a set of pulleys and weights to simulate the effect of the wind on a wind turbine is easy and gives

good results.

To include load cells in the mooring lines does not imply any complexity and provides great information for the design of the mooring system.

The use of a DC motor controlled from a computer with a microcontroller and the servo-drive to model the PTO is a flexible configuration with good repeatability.

Different boundary conditions around of converters can sometimes be beneficial for energy production.It is important that the model can be damaged during transport. Avoid using glue into parts that can be damaged and leak-check prior to transport. Figure 13 shows the sunken model after some hours in the water, due to a small leakage caused during model transport. Avoid complex sealing solutions. Small carcks and little leaks can be extremely difficult to find and solve with easy methods (hard glue, foams, etc…).


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Figure 13 – Model of platform partially sunk due to water leakage

4 FURTHER INFORMATION

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

An overview paper with first summary of these results obtained here has been submitted to a selected international conference.

A paper called “Design and Performance Validation of a Hybrid Offshore Renewable Energy Platform." has been submitted and will be presented to the IEEE EVER 2015 to be held in Monaco in April 2015.

EnerOcean showed the testing plan and previous results of testing in previous phase in the MARINET users conference held in ROME MARINET USERWORKSHOP 6th of November 2013.

Part of these results has been published in the Technical deliverables of Wp3 and Wp4 FP7 TROPOS project.

A presentation in the Spanish APPA Marina session in Genera Energy conference held in Madrid in February 2015 shown part of the results.

4.2 WEBSITE &SOCIAL MEDIA Websites: www.pelagicpower.no www.enerocean.com www.w2power.com

5 REFERENCES

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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infrastructure access report - marinet2 · infrastructure access report: w2p mooring and wind final...

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