Floating Wind Turbine Model Test

Transcription

1 Marine Renewables Infrastructure Network Infrastructure Access Report Infrastructure: ECN Hydrodynamic and Ocean Engineering Tank User-Project: INNWIND.EU Floating Wind Turbine Model Test INNWIND.EU Floating Wind Turbine Model Test (Phase 2, November 2014) Status: Draft Version: 01 Date: 4-December -2014

2 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-. The initiative is funded through the EC's Seventh Framework Programme (FP7) and runs for four years until 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- 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 for more details. Partners Ireland University College Cork, HMRC (UCC_HMRC) Coordinator Sustainable Energy Authority of Ireland (SEAI_OEDU) Denmark Aalborg Universitet (AAU) Danmarks Tekniske Universitet (RISOE) France Ecole Centrale de Nantes (ECN) Institut Français 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) Netherlands Stichting Tidal Testing Centre (TTC) Stichting Energieonderzoek Centrum Nederland (ECNeth) Germany Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V (Fh_IWES) Gottfried Wilhelm Leibniz Universität Hannover (LUH) Universitaet Stuttgart (USTUTT) Portugal Wave Energy Centre Centro de Energia das Ondas (WavEC) Italy Università degli Studi di Firenze (UNIFI-CRIACIV) Università degli Studi di Firenze (UNIFI-PIN) Università degli Studi della Tuscia (UNI_TUS) Consiglio Nazionale delle Ricerche (CNR-INSEAN) Brazil Instituto de Pesquisas Tecnológicas do Estado de São Paulo S.A. (IPT) Norway Sintef Energi AS (SINTEF) Norges Teknisk-Naturvitenskapelige Universitet (NTNU) Belgium 1-Tech (1_TECH) Page 2 of 33

3 DOCUMENT INFORMATION Title Floating Wind Turbine Model Test Distribution Public Document Reference MARINET-TA2-INNWIND.EU User-Group Leader, Lead Frank Sandner USTUTT Author [Optional: Insert address and contact details] User-Group Members, Henrik Bredmose DTU Contributing Authors Pierluigi Montinari POLIMI Ricardo Pereira DNVGL Carlo Bottasso POLIMI Florian Amann USTUTT José Azcona CENER Faisal Bouchotrouch CENER Infrastructure Accessed: ECN Hydrodynamic and Ocean Engineering Tank Infrastructure Manager Jean-Marc Rousset (or Main Contact) REVISION HISTORY Rev. Date Description Prepared by (Name) 01 Approved By Infrastructure Manager Status (Draft/Final) Page 3 of 33

4 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. Page 4 of 33

5 EXECUTIVE SUMMARY This report covers the second of two phases of combined -and-wave model testing of a generic floating turbine system. The widely studied open concept of the OC4-DeepC semi-submersible model has been tested together with a Froude-scaled rotor with increased chord for low Re-numbers.Two different scaling ratios have been used in order to represent, first, the 5MW NREL reference turbine and, second, the 10MW INNWIND.EU reference turbine. All of rotor speed, speed and thrust force are correctly scaled in this approach.in the second phase of this project the remaining test cases will be finalized (ULS conditions, yawed inflow, error assessment) and a thrust force generation for both turbine models will be tested through a ducted fan in terms of a hardware-in-the-loop experiment. It is the explicit goal of this project to make the model and measurement data public to a full extent for the international research community for model validation of advanced coupled software tools, including aerodynamic and hydrodynamic CFD. Page 5 of 33

6 CONTENTS 1 INTRODUCTION & BACKGROUND INTRODUCTION DEVELOPMENT SO FAR Stage Gate Progress Plan for this Access OUTLINE OF WORK CARRIED OUT SETUP Low Reynolds Rotor Ducted Fan and Software in the Loop Scaled model for the platform TESTS Test Plan RESULTS ANALYSIS & CONCLUSIONS MAIN LEARNING OUTCOMES PROGRESS MADE Progress Made: for Marine Renewable Energy Industry KEY LESSONS LEARNED FURTHER INFORMATION SCIENTIFIC PUBLICATIONS REFERENCES APPENDICES STAGE DEVELOPMENT SUMMARY TABLE ANY OTHER APPENDICES Page 6 of 33

7 1 INTRODUCTION & BACKGROUND 1.1 INTRODUCTION For floating turbine systems various numerical codes and methods are currently available or are still under development. Here the major developments concern the coupling of advanced aerodynamics and hydrodynamics, but also non-linear behavior of mooring lines. In addition, these experiments will be useful for the validation of testing methodologies, in particular for the integration of the aerodynamic rotor thrust during combined wave and tests and the mooring system modelling. The tools and methods validated in this test campaign will be applied to the design of a floating substructure for a 10MW turbine in Task 4.3 of the INNWIND.EU project. In the international code-comparison project Offshore Code Comparison Collaboration Continuation (OC4) funded by the IEA a generic semi-submersible floating platform has been simulated together with the NREL 5MW reference turbine by numerous institutions worldwide, see [1] and [2]. It is a semi-submersible design with three legs and 20m draft. The hub height is 87.6m. The basic geometry of the floating turbine is shown in Figure 1. The general mass characteristics of the platform are: Figure 1: Full Scale Semisubmersible [1] Table 1 General mass parameters of the floating turbine in full scale Magnitude Value Comments Weight t Including ballast Centre of Gravity m Below sea water lever (SWL) Inertia Ixx 6.827E+9 kgm2 About centre of gravity, exclusive added mass Inertia Iyy 6.827E+9 kgm2 About centre of gravity, exclusive added mass Page 7 of 33

8 Inertia Izz 1.226E+10 kgm2 About centre of gravity, exclusive added mass An overview of the main parameters that define the tower is provided in Table 2: Table 2 General parameters of the tower Magnitude Value Comments Tower Base Elevation 10 m (Platform Top) Above SWL Tower Top Elevation 87.6 m (Yaw Bearing) Above SWL Total Tower Mass t - Tower centre of Gravity Location Inertia Izz 43.4m Above SWL. Along Tower Centerline 1.226E10 kgm2 About centre of gravity, exclusive added mass Table 3 shows a summary of the main parameters that define the rotor of the turbine model. Table 3 General parameters of the rotor Magnitude Total RNA Mass Rotor Mass Nacelle Mass Rotor Diameter Rating Hub Height Rated Tip Speed Value 350 t 110 t 240 t 126 m 5 MW 90 m 80 m/s The OC4 mooring lines system is composed by three lines spread symmetrically about the central vertical axis of the platform. The depth of the location is 200m. 1.2 DEVELOPMENT SO FAR The objective of the project INNWIND.EU is to investigate the development of large offshore turbine systems above 10MW. In workpackage 4 fixed-bottom as well as floating foundations are being analysed. A first goal for the floating part is to gain valuable knowledge and experience in model testing and a thourough comparison with a wide range of numerical simulation tools from conceptual models to high-fidelity CFD software. For this end, a generic floating offshore turbine (FOWT) model has been selected. The model in a scale of 1:45 has been set up by partner USTUTT and preliminary assembled with the turbine model by partner POLIMI. It has been tested in a water tank and the datalogging devices synchronized through a common trigger signal. In order to reduce the influence of data cables a wireless transmission system has been set up for the platform inertial measurement unit (IMU) and the fairlead sensors. These waterproof sensors are selected since no interference with the mooring system dynamics occurs. Page 8 of 33

9 1.2.1 Stage Gate Progress Previously completed: Planned for this project: STAGE GATE CRITERIA Stage 1 Platform only and Froude-scaled rotor tests Model building (Platform: USTUTT, turbine: POLIMI), sensor application, data logging system, data transmission. First test of the assembled FOWT model in water (July 2014 at University of Stuttgart) First unmoored free-decay tests in heave with data acquisition (July 2014 at University of Stuttgart) System identification (platform only): Static displacement in surge and sway (mooring ID) System identification (platform only): Free decay tests (moored) in surge, sway, heave, pitch Platform-only tests: Regular waves, irregular waves (set of frequencies for 5 and 10MW scale) System identification (FOWT, Fr-scaled rotor): Free decay tests (moored) in surge, sway, heave, pitch Regular waves and (FOWT, Fr-scaled rotor, for RAO) Irregular waves and (FOWT, Fr-scaled rotor; Selection of realistic wave conditions for 5 and 10MW scale) White noise waves and (FOWT, Fr-scaled rotor, for RAO) Comprehensive numerical model validation. Orig app Curremt access Status Next acces Stage 2 Platform with Froude-scaled rotor and HIL rotor tests Ultimate limit state conditions, idling rotor (FOWT, Fr-scaled rotor, for RAO). Yawed inflow (FOWT, Fr-scaled rotor, for RAO; Rotate tower on platform). Assembly of ducted fan tower and platform. System identification (FOWT, HIL rotor, for RAO): Free decay tests (moored) in surge, sway, heave, pitch. Regular waves and (FOWT, HIL rotor, for RAO). Irregular waves and (FOWT, HIL rotor, for RAO; Selection of realistic wave conditions for 5 and 10MW scale). Error assessment of shifted ballast for correction of center of gravity. Investigation of inflow conditions and blockage correction, determination of CFD boundary conditions. Forced-displacement tests (platform only, with Hexapod available at ECN). Comprehensive numerical model validation. Stage 3 Blade pitch controller testing Blade-pitch control with varying speeds. Page 9 of 33

10 STAGE GATE CRITERIA Individual blade pitch control (IPC). Orig app Curremt access Status Next acces Stage 4 Innovative INNWIND.EU floating platform Build new platform model for 10MW reference turbine in suitable scale. Test performance in combined -and-wave conditions. Compare results with design assumptions and numerical model predictions. Finalize structural design of innovative INNWIND.EU platform. Preliminary concept of manufacturing and installation. Levelized cost of energy analysis. Environmental impact analysis. Dissemination of results Plan for this Access In a previous access of two weeks the group performed a series of tests of increasing complexity: including free decays, only regular waves and RAO s. The plan for this access consists on combined tests of and waves. All possible combinations of steady and turbulent waves and regular and irregular waves are considered. The inclusion of aerodynamic loads is performed using the ducted fan and software in the loop approach and also using a Reynolds scaled rotor model Environmental Conditions Definition The last part of the test matrix consists of cases representatives of different sea states and also different sea states in combination with s. These environmental conditions (irregular sea states, regular sea states and conditions) are presented in Table 4, Table 5 and Table 6. A description of the cases involving these environmental conditions is provided in the following sections. Table 4 Irregular Sea Conditions Irregular Sea States Sea State Hs (m) Tp (s) Page 10 of 33

11 Table 5 Regular Sea Conditions Regular Sea States Sea State Height (m) Period (s) Table 6 Wind Conditions Wind Conditions Wind State Steady Wind Speeds (m/s) Turbulent Wind Speeds (m/s) Irregular Waves Cases Irregular wave cases are defined with the H s and T p defined in Table 4 with 0º and 45º of heading direction Wind Loading Characterization Wind only cases with the platform moored and still water are defined. Constant and turbulent s with the speeds from Table 6 are reproduced. These cases allow characterizing the loading system and verifying that it is correctly tuned and that the displacements in surge and pitch correspond to the expected values. In addition, a group of cases consisting in free decay tests in surge and pitch combined with constant s (see Table 7) is defined. These cases are useful for the characterization of the damping introduced by the aerodynamic loading. Page 11 of 33

12 Table 7 Free Decay + Constant Wind Conditions Free Decay + Constant Wind Infrastructure Access Report: INNWIND.EU Initial Displacement Wind Speed (m/s) # m 8.5 Surge # m 11.4 # m 18 # 1 5º 8.5 Pitch # 2 5º 11.4 # 3 5º Combined Wave and Wind Tests Combination of regular and irregular waves with steady and turbulent s according to the conditions described in Table 4, Table 5 and Table 6 are performed. Page 12 of 33

13 2 OUTLINE OF WORK CARRIED OUT 2.1 SETUP Low Reynolds Rotor The Setup consists of a turbine model with rigid rigid blades and flexible tower, that is mounted on the floating platform. The nacelle is composed of the following components: Mechanical components for transmission Optical encoder for azimuth measurement 3-Pitch actuators control units with position control Torque actuator housed in tower top for torque and speed control Shaft strain gages and signal conditioning board 36 channels slip ring Figure 2: Picture of nacelle At the bottom of the tower, strain gages are applied for acquiring tower loads. All the signal are then brought away to the cabinet by water proof cables. The cabinet contains Bachmann control, data acquisition system, motor torque and and power suppliers. Finally the system communicates throw Ethernet connection with a remote computer with a user interface Ducted Fan and Software in the Loop An alternative method to the design of a low-reynolds rotor to achieve representative rotor thrust during the execution of the tests is the use of a ducted fan to introduce a controlled force at the tower top that represents the aerodynamic loading. This method has the advantages of being very economical and avoiding an external generation system to introduce the main force impacting the floating system by other means. Several of these options and the correlated experiments from the literature are outlined in [4]. The use of this method in addition to the low-reynolds rotor will allow an assessment of the advantages and shortcomings related to this simplified testing method. The basic concept of the method consists of substituting the rotor by a fan driven by an electric motor. The fan thrust is controlled by the fan rotational speed set by the controller, which again depends on the real time simulation of the full scale rotor in a turbulent field, with the platform motions measured in real time in the wave tank test. A picture of the ducted fan at the tower top is shown in Figure 2. Page 13 of 33

14 Figure 2 Ducted fan The fan and its real-time controller are lighter than the scaled mass and thus, ballast has been added to the nacelle to match the full scale configuration. The fan is mounted on the same tower as the Froude-scaled rotor. The model of ducted fan selected to generate the force representing the aerodynamic thrust during the tests is the DS-30-AXI HDS, manufactured by the German company Schübeler. The fan is powered by a brushless motor HET 2W20 that is controlled by an Electronic Speed Controller (ESC) YGE 90 HV, and works with an industrial AC/DC power supply. This system configuration produces an approximate force range of 0-18N. The rpm of the motor (and therefore the force produced by the fan) is controlled by a Pulse Width Modulation (PWM) signal that is generated with the LabVIEW control software, using servo libraries for Arduino. The demanded force for the fan is provided by the full scale simulation of the rotor s aerodynamic thrust. The software used to compute the aerodynamic loads in real time is the version v6.02c-jmj of the FAST code, with AeroDyn The software has been compiled in Linux and during the test campaign it was ran in a computer with a 2.54GHz Intel Core Duo CPU and 2GB of RAM. Figure 4 Fan Control System Lay Out The layout of the system is shown in Figure 3. The left side describes the simulation part of the system, which works in full scale, and the right side represents the wave tank scaled test. The different magnitudes that are interchanged between both blocks are transformed by the appropriated scaling laws based on the factor scale λ. Page 14 of 33

15 Figure 3 Software-in-the-Loop Method Diagram The simulation tool provides the total aerodynamic force on the shaft F aero from integration of all the aerodynamic loading at the blade elements. This force in full scale is transformed to the model scale ( f aero) and the pulse width of the PWM signal needed to produce the force in the ducted fan is provided by a calibration curve. The control system regulates the fan speed that introduces the desired force at the model s hub height. The waves produced by the wave maker are also acting over the platform and, together with the aerodynamic thrust, inducing motions. The acquisition system measures the positions and velocities for the 6 degrees of freedom of the platform at a certain sampling period. These measurements are sent to the simulation tool that is waiting for the data to advance one time step and calculate the new value of the aerodynamic thrust. For this reason, the sampling period, t, and the 0.5 simulation time step, T, have to be set accordingly (with a factor of λ ). Page 15 of 33

16 2.1.3 Scaled model for the platform An inertial platform and an accelerometer are housed in the platform, and with three force sensors applied between the platform connections and mooring lines are managed by arduino system in wireless connection with a second computer. Figure 6 Pictures of the model assembled Figure 7: Picture of the platform model with force sensors Page 16 of 33

17 Figure 8: Picture of the tower load cell Figure 9: Picture of the cabinet Page 17 of 33

18 Sample Landscape section Page 18 of 33

19 2.2 TESTS Test Plan Table 8 Wind tests with moored platform and water Case Description Wind speed (m/s) Wind speed (m/s) (Full scale) Measurements Duration (s) Comments Wind tests / moored platform / still water Steady Wind 1,04 7,00 V Wi ML PM 89,4 Wind tests / moored platform / still water Steady Wind 1,27 8,50 V Wi ML PM 89,4 Wind tests / moored platform / still water Steady Wind 1,70 11,40 V Wi ML PM 89,4 Wind tests / moored platform / still water Steady Wind 2,68 18,00 V Wi ML PM 89,4 Wind tests / moored platform / still water Wind tests / moored platform / still water Wind tests / moored platform / still water Wind tests / moored platform / still water Steady Wind 3,73 25,00 V Wi ML PM 89,4 Turbulent 1,04 7,00 V Wi ML PM 536,7 Turbulent 1,27 8,50 V Wi ML PM 536,7 Turbulent 1,70 11,40 V Wi ML PM 536,7 No turbulent No turbulent No turbulent Page 19 of 33

20 Wind tests / moored platform / still water Wind tests / moored platform / still water Turbulent 2,68 18,00 V Wi ML PM 536,7 Turbulent 3,73 25,00 V Wi ML PM 536,7 No turbulent No turbulent Table 9 Free decay test with steady and moored hull Case Description Initial Displacement (m/deg) Initial Displacemen (Full Scale) (m/deg) Wind speed (m/s) Wind speed (m/s) (Full scale) Measurements Duration (s) Free decay tests + steady / moored hull Surge + Steady 0,15 6,75 1,27 8,50 V Wi ML PM 160,8 Free decay tests + steady / moored hull Surge + Steady 0,15 6,75 1,70 11,40 V Wi ML PM 160,8 Free decay tests + steady / moored hull Surge + Steady 0,15 6,75 2,68 18,00 V Wi ML PM 160,8 Free decay tests + steady / moored hull Pitch + Steady 5,00 5,00 1,27 8,50 V Wi ML PM 38,1 Free decay tests + steady / moored hull Pitch + Steady 5,00 5,00 1,70 11,40 V Wi ML PM 38,1 Page 20 of 33

21 Free decay tests + steady / moored hull Pitch + Steady 5,00 5,00 2,68 18,00 V Wi ML PM 38,1 Table 10 Regular wave with steady Case Wave Height (m) Period (s) Period (Full Scale) (s) Wave Direction (deg) Wind speed (m/s) Measurements Duration (s) Regular wave + steady Regular wave + steady Regular wave + steady Regular wave + steady Regular wave + steady Regular wave + steady 0,052 0,820 5,50 0,0 1,043 V Wv Wi ML PM 41,0 0,073 0,969 6,50 0,0 1,267 V Wv Wi ML PM 48,4 0,092 1,088 7,30 0,0 1,699 V Wv Wi ML PM 54,4 0,137 1,327 8,90 0,0 2,683 V Wv Wi ML PM 66,3 0,140 1,491 10,00 0,0 3,727 V Wv Wi ML PM 74,5 0,052 0,820 5,50 45,0 1,043 V Wv Wi ML PM 41,0 Page 21 of 33

22 Regular wave + steady Regular wave + steady Regular wave + steady Regular wave + steady White Noise / steady Irregular wave + steady Irregular wave + steady Irregular wave + steady Irregular wave + steady Irregular wave + steady Irregular wave + steady Irregular wave + steady Irregular wave + steady 0,073 0,969 6,50 45,0 1,267 V Wv Wi ML PM 48,4 0,092 1,088 7,30 45,0 1,699 V Wv Wi ML PM 54,4 0,137 1,327 8,90 45,0 2,683 V Wv Wi ML PM 66,3 0,133 1,491 10,00 45,0 3,727 V Wv Wi ML PM 74,5 0, ,7 V Wv Wi ML PM 600 0,061 0,820 5,50 0 1,04 V Wv Wi ML PM 536,7 0,070 0,969 6,50 0 1,27 V Wv Wi ML PM 536,7 0,092 1,088 7,30 0 1,70 V Wv Wi ML PM 536,7 0,108 1,327 8,90 0 2,68 V Wv Wi ML PM 536,7 0,133 1,491 10,00 0 3,73 V Wv Wi ML PM 536,7 0,061 0,820 5, ,04 V Wv Wi ML PM 536,7 0,070 0,969 6, ,27 V Wv Wi ML PM 536,7 0,092 1,088 7, ,70 V Wv Wi ML PM 536,7 Page 22 of 33

23 Irregular wave + steady Irregular wave + steady 0,108 1,327 8, ,68 V Wv Wi ML PM 536,7 0,133 1,491 10, ,73 V Wv Wi ML PM 536,7 Tests for 10 MW scaled model: Table 11 Regular/Irregular wave with moored hull Case Wave Height (m) Period (s) Period (Full Scale) (s) Wave Direction (deg) Measurements Duration (s) Regular waves / moored hull 0,113 0, V Wv ML PM 37,3 Regular waves / moored hull 0,113 0, V Wv ML PM 44,7 Regular waves / moored hull 0,113 0, V Wv ML PM 52,2 Regular waves / moored hull 0,113 1, V Wv ML PM 59,6 Regular waves / moored hull 0,113 1, V Wv ML PM 67,1 Regular waves / moored hull 0,113 1, V Wv ML PM 74,5 Page 23 of 33

24 Regular waves / moored hull 0,113 1, V Wv ML PM 82,0 Regular waves / moored hull 0,113 1, V Wv ML PM 111,8 Regular waves / moored hull 0,113 2, V Wv ML PM 149,1 Regular waves / moored hull 0,113 3, V Wv ML PM 186,3 White Noise / moored hull 0, V Wv ML PM 536,7 White Noise / moored hull 0, V Wv ML PM 536,7 Irregular waves / moored hull 0,046 0,710 5,5 0 V Wv ML PM 536,7 Irregular waves / moored hull 0,052 0,839 6,5 0 V Wv ML PM 536,7 Irregular waves / moored hull 0,069 0,942 7,3 0 V Wv ML PM 536,7 Irregular waves / moored hull 0,081 1,149 8,9 0 V Wv ML PM 536,7 Irregular waves / moored hull 0,100 1, V Wv ML PM 536,7 Irregular waves / moored hull 0,046 0,710 5,5 45 V Wv ML PM 536,7 Irregular waves / moored hull 0,052 0,839 6,5 45 V Wv ML PM 536,7 Irregular waves / moored hull 0,069 0,942 7,3 45 V Wv ML PM 536,7 Irregular waves / moored hull 0,081 1,149 8,9 45 V Wv ML PM 536,7 Irregular waves / moored hull 0,100 1, V Wv ML PM 536,7 Page 24 of 33

25 Table 11 Free decay with steady and moored hull Case Description Initial Displacement (m/deg) Wind speed (m/s) Measurements Duration (s) Free decay tests + steady / moored hull Free decay tests + steady / moored hull Free decay tests + steady / moored hull Free decay tests + steady / moored hull Free decay tests + steady / moored hull Free decay tests + steady / moored hull Surge + Steady 0,11 1,10 V Wi ML PM 139,3 Surge + Steady 0,11 1,47 V Wi ML PM 139,3 Surge + Steady 0,11 2,32 V Wi ML PM 139,3 Pitch + Steady 5,00 1,10 V Wi ML PM 33,0 Pitch + Steady 5,00 1,47 V Wi ML PM 33,0 Pitch + Steady 5,00 2,32 V Wi ML PM 33,0 Page 25 of 33

26 Table 12 Free decay with steady and moored hull Case Wave Height (m) Period (s) Wave Direction (deg) Wind speed (m/s) Measurements Duration (s) Regular wave + steady 0,039 0,710 0,0 0,9 V Wv Wi ML PM 35,5 Regular wave + steady 0,055 0,839 0,0 1,1 V Wv Wi ML PM 42,0 Regular wave + steady 0,069 0,942 0,0 1,5 V Wv Wi ML PM 47,1 Regular wave + steady 0,103 1,149 0,0 2,3 V Wv Wi ML PM 57,4 Regular wave + steady 0,100 1,291 0,0 3,2 V Wv Wi ML PM 64,5 Regular wave + steady 0,046 0,710 45,0 0,9 V Wv Wi ML PM 35,5 Regular wave + steady 0,052 0,839 45,0 1,1 V Wv Wi ML PM 42,0 Regular wave + steady 0,069 0,942 45,0 1,5 V Wv Wi ML PM 47,1 Page 26 of 33

27 Regular wave + steady 0,081 1,149 45,0 2,3 V Wv Wi ML PM 57,4 Regular wave + steady 0,100 1,291 45,0 3,2 V Wv Wi ML PM 64,5 White Noise / steady 0, ,47 V Wv Wi ML PM 600 Irregular wave + steady 0,046 0, ,90 V Wv Wi ML PM 464,8 Irregular wave + steady 0,052 0, ,10 V Wv Wi ML PM 464,8 Irregular wave + steady 0,069 0, ,47 V Wv Wi ML PM 464,8 Irregular wave + steady 0,081 1, ,32 V Wv Wi ML PM 464,8 Irregular wave + steady 0,100 1, ,23 V Wv Wi ML PM 464,8 Irregular wave + steady 0,046 0, ,90 V Wv Wi ML PM 464,8 Irregular wave + steady 0,052 0, ,10 V Wv Wi ML PM 464,8 Irregular wave + steady 0,069 0, ,47 V Wv Wi ML PM 464,8 Irregular wave + steady 0,081 1, ,32 V Wv Wi ML PM 464,8 Irregular wave + steady 0,100 1, ,23 V Wv Wi ML PM 464,8 Page 27 of 33

28 2.3 RESULTS Figure 30 and Figure 31 show selected results for a pitch free-decay test of the platform with the Froude-scaled rotor mounted on top from week 2. The effect of the cables is assessed through this comparison, where Figure shows the results for disconnected cables. Figure 10 Pitch free decay without cables (Froude-scaled rotor). Figure 11 - Pitch free decay with cables (Froudescaled rotor). Figure 32 compares 4 different free decay tests in pitch performed with 4 different conditions and using the coupled fan system to model the thrust. In the case with no the fan is not connected and, therefore, the loading is zero. The other cases correspond to constant velocities of 8.5m/s, 11.4m/s and 18m/s in full scale (scale factor 1/45). The plot shows that the minimum damping appears in the No Wind case, and the maximum damping corresponds to the case with 11.4m/s of that is the rated speed, and also the condition where the aerodynamic thrust is the maximum. Page 28 of 33

29 Figure 12 Comparison of pitch free decay tests with different constant speeds modelled by the coupled fan system. 2.4 ANALYSIS & CONCLUSIONS The combined tests of wave and have shown a good behaviour of the platform tested with moderate motions of the concept. One important outcome has been the verification of the two approaches to integrate the aerodynamic loading in the combined wave and tests. The measurements of thrust provided by the scaled low Reynolds number rotor were in the range of the objective defined by the full scale rotor. In addition, the ducted fan was also successfully integrated in the tests and the capability to model the aerodynamic damping has been showed by the execution of pitch free decay tests under steady loading at different speeds. 3 MAIN LEARNING OUTCOMES 3.1 PROGRESS MADE The validation of the methodology for the integration of aerodynamic loads on the test using a low-reynolds, pitch controlled rotor is a very innovative alternative to the other existing technologies as the use of a drag actuator disk that can provide a very good performance, including the effect of the control actions. The detailed description of the built model, the sensors and data loggers used and the test description and data which will be published allow for a thorough improvement of the testing procedure of floating turbines and contribute to the establishment of best practices for future model tests. In addition, the validation of the ducted fan and Software-in-the-Loop approach is an important outcome of the project. During the implementation of the system, we gain important experience on how to solve the communication problems between the computers and the acquisition system. Some of the software in the loop simulations failed due to the use of a blade discretization with excessive number of elements that slowed the simulation. This was an important lesson learnt Next Steps for Research or Staged Development Plan Exit/Change & Retest/Proceed? Once validated our methodologies for the testing of combined wave and cases, we plan to perform a validation campaign with an innovative platform concept currently under development. It is a hybrid concept between spar and semisubmersible in concrete Progress Made: for Marine Renewable Energy Industry The validation of the methodology for the integration of aerodynamic loads on the test using a low-reynolds, pitchcontrolled rotor is a very innovative alternative to the other existing technologies as the use of a drag actuator disk, that can provide a very good performance, including the effect of the control actions. The ducted fan and software in the loop method is also an innovative approach with very low cost that can be applied in facilities where no generator exists. Page 29 of 33

30 3.2 KEY LESSONS LEARNED The installation of the scaled full mooring system has to be performed with precision. Due to the dimensions of the basin and the lines this is not an easy task. The platform motion can be very sensitive to small discrepancies on the mooring system setup. The aerodynamic loading has a high impact on the dynamic of the platform, in particular in the pitch motion that has a high impact on the loading level of the turbine. The correct scaling of the thrust is critical for the validation of a floating turbine conceptual design. Wireless acquisition systems have shown a very good performance in this test campaign and have the advantage of not requiring wires that can affect the dynamics of the test and introduce disturbance in the results The low Reynolds rotor designed by our group performed very well and it is an innovative and effective way of incorporating the aerodynamic loading to the scaled model rotor The ducted fan and Software-in-the-Loop approach has showed the capability of modelling the aerodynamic damping during the tests. Parameters as the height and period of the waves generated, velocity, force at the rotor, measurements of the sensors, should be continuously checked during the tests execution to assure they match the requirements and to prevent the generation of invalid test cases. 4 FURTHER INFORMATION 4.1 SCIENTIFIC PUBLICATIONS Sandner, F., Amann, F., Azcona, J., Munduate, X., Bottasso, C. L., Campagnolo, F., Bredmose H, Manjock, A., Pereira, R., Robertson, A. (2015). Model Building and Scaled Testing of 5MW and 10MW Semi-Submersible Floating Wind Turbines. Abstract submitted to EERA Deep. Trondheim/NO. Müller, K., Sandner, F., Bredmose, H., Azcona, J., Manjock, A., & Pereira, R. (2014). Improved Tank Test Procedures For Scaled Floating Offshore Wind Turbines. In International Wind Engineering Conference IWEC. Bremerhaven. Azcona, J., Bekiropoulos, D., Bredmose, H., Fischer, A., Heilskov, N. F., Krieger, A., Voutsinas, S. (2012). INNWIND.EU D4.2.1: State-of-the-art and implementation of design tools for floating structures. Azcona, J., Sander, F., Bredmose, H., Manjock, A., Pereira, R., & Campagnolo, F. (n.d.). INNWIND.EU D4.2.2: Methods for performing scale-tests for method and model validation. Page 30 of 33

31 5 REFERENCES [1] A. Robertson, J. Jonkman, M. Masciola, H. Song, A. Goupee, A. Coulling and C. Luan, "Definition of the Semisubmersible Floating System for Phase II of OC4". [2] J. Jonkman, S. Butterfield, W. Musial and G. Scott, "Definition of a 5-MW Reference Wind Turbine for Offshore System Development Definition," no. February, 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. Page 31 of 33

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