user-project : tempest tidal energy mobilisation, proving ... · tidal energy mobilisation, proving...

Infrastructure Access Report

Infrastructure: NAREC CPTC Development Test Lab

User-Project: TEMPEST

Tidal Energy Mobilisation, Proving and Entire Systems

Testing

Smart Motor / Atlantis Resources Corporation

Marine Renewables Infrastructure Network

Status: Final

Version: 01

Date: 19-Sep-2013

EC FP7 “Capacities” Specific Programme

Research Infrastructure Action

Infrastructure Access Report: TEMPEST

Rev. 01, 19-Sep-2013

of 20

ABOUTMARINETMARINET (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)

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)

Belgium

1-Tech (1_TECH)

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)


Rev. 01, 19-Sep-2013

of 20

DOCUMENTINFORMATIONTitle Tidal Energy Mobilisation, Proving and Entire Systems Testing

Distribution Public

Document Reference MARINET-TA1-TEMPEST

User-Group Leader, Lead

Author

Svein Erik Evju Smart Motor AS

Jarleveien 8, 7041 Trondheim, Norway

User-Group Members,

Contributing Authors

Eirik Skare Smart Motor AS

Dave Rigg Atlantis Resources Corporation

Infrastructure Accessed: NAREC Nautilus Rotary Test Rig

Infrastructure Manager

(or Main Contact)

Oliver Wragg

REVISIONHISTORYRev

.

Date Description Prepared by

(Name)

Approved By

Infrastructure

Manager

Status

(Draft/Final)

01 19/09/13 Submitted Report D. Skinnader Final


Rev. 01, 19-Sep-2013

of 20

ABOUTTHISREPORTOne 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.

ACKNOWLEDGEMENTThe work described in this publication has received support from MARINET, a European Community - Research

Infrastructure Action under the FP7 “Capacities” Specific Programme.

LEGALDISCLAIMERThe 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, 19-Sep-2013

of 20

EXECUTIVESUMMARY

The 3MW Nautilus purpose-built rotary test bed at the Narec Marine Test Facility was utilised to subject Atlantis

Resources Corporation’s AR1000 Drive Train architecture to a series of systems and accelerated life time tests. The

supporting infrastructure, software modelling capability and technical expertise enabled de-risking of Smart Motor’s

Permanent Magnet Generator and Control System design and allowed for reliability analysis and monitoring for the

Drive Train.

The result has been the ability to complete a significant number of testing procedures in a dry, controlled environment.

This has proved to have been an advantageous exercise and has dramatically reduced risk for proceeding offshore

testing, in addition to limiting future supplier reliance and cost.


Rev. 01, 19-Sep-2013

of 20

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 .............................................................................................................................................................. 10

2.2.1 Test Plan .................................................................................................................................................... 10

2.2.2 Drive Train Efficiency Mapping ................................................................................................................. 10

2.2.3 Thermal Mapping ...................................................................................................................................... 11

2.2.4 Control System Testing .............................................................................................................................. 11

2.2.5 Accelerated Life Testing ............................................................................................................................ 12

2.2.6 Brake Testing ............................................................................................................................................. 13

2.3 RESULTS & ANALYSIS ......................................................................................................................................... 13

2.3.1 Drive Train Efficiency Mapping ................................................................................................................. 13

2.3.2 Thermal Mapping ...................................................................................................................................... 14

2.3.3 Control System Testing .............................................................................................................................. 15

2.3.4 Accelerated Life Testing ............................................................................................................................ 15

3 MAIN LEARNING OUTCOMES ...................................................................................................................... 17

3.1 PROGRESS MADE .............................................................................................................................................. 17

3.1.1 Next Steps .................................................................................................................................................. 17

3.1.2 Progress Made: For Marine Renewable Energy Industry .......................................................................... 17

3.2 KEY LESSONS LEARNED ....................................................................................................................................... 18

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


Rev. 01, 19-Sep-2013

of 20

1 INTRODUCTION&BACKGROUND

1.1 INTRODUCTION

The 3MW Nautilus purpose-built rotary test bed at the Narec Marine Test Facility was utilised to subject Atlantis Resources

Corporation’s AR1000 Drive Train architecture to a series of systems and accelerated life time tests. The supporting infrastructure,

software modelling capability and technical expertise enabled de-risking of Smart Motor’s Permanent Magnet Generator (PMG)

and Control System design and enabled reliability analysis and monitoring for the Drive Train.

The result has been the ability to complete a significant number of testing procedures in a dry, controlled environment. This has

proved to have been an advantageous exercise and has dramatically reduced risk for proceeding offshore testing, in addition to

limiting future supplier reliance and cost.

1.2 DEVELOPMENTSOFAR

1.2.1 StageGateProgress

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, 19-Sep-2013

of 20

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 PlanForThisAccessThe key objectives planned for the project were as follows:

Objective: Details:

1 Final tuning of the pre-commissioned third-party Converter and Control components to complete the supplier

contract requirements. This would allow future tests to be run at a considerable cost reduction as the need to

re-engage the suppliers would be minimised or removed completely.

2 Provision of thermal characteristics of power train components to feed into the Detailed Design of the next-

generation turbine.

3 Study the performance of the brake and optimise use within an automated control system.

4 Investigate the efficiency of the turbine across its full operational envelope.

5 Carry out Control system testing to observe the automated system behaviour and tune the algorithm based

on theoretical assumptions for blade characteristics and system inertia correction factors.

6 Conduct accelerated lifecycle testing on the turbine to provide continuous running hours data for the turbine.


Rev. 01, 19-Sep-2013

of 20

2 OUTLINEOFWORKCARRIEDOUT

2.1 SETUPThe 3MW Nautilus purpose-built rotary test bed at the Narec Marine Test Facility was utilised to subject Atlantis Resources

Corporation’s AR1000 Drive Train architecture to a series of systems and accelerated life time tests. The supporting infrastructure,

software modelling capability and technical expertise enabled de-risking of Smart Motor’s PMG and Control System design and

allowed for reliability analysis and monitoring for the Drive Train.

As discussed in this report, the following aspects of the architecture were monitored:

1. Drive Train Efficiency Mapping

2. Thermal Mapping

3. Control System Testing

4. Accelerated Life Testing

5. Brake Testing


Rev. 01, 19-Sep-2013

of 20

2.2 TESTS

2.2.1 TestPlanAs discussed in the previous section SM and ARC collaborated on a number of aspects of the architecture which was supported

by MARINET.

The timescales involved for the execution of the plan were as follows:

Action No. Action Start Date Finish Date

1 Site Set Up-Dry 11/5/12 28/6/12

1.1 Nautilus Ready 11/5/12 11/5/12

1.2 Install nacelle into rig-Dry 11/5/12 17/5/12

1.3 Strip out nacelle-Dry 26/6/12 28/6/12

2 Commissioning 18/5/12 24/5/12

2.1 Commissioning-Dry 18/5/12 24/5/12

3 Testing 25/5/12 25/6/12

3.1 Test 1 25/5/12 28/5/12

3.2 Test 2 29/5/12 31/5/12

3.3 Test 3 01/6/12 04/6/12

3.4 Accelerated life testing 05/6/12 25/6/12

The test details were as follows:

Test 1 - Validate the permanent magnet generator performance characteristics

Running a series of tests with the Nautilus rig set to a constant value whilst SM vary the torque on the generator and hence the

electrical load. This allows for SM to build a complete efficiency map of the generator.

Measurements Required - RPM, input torque on ARC shaft, generator current, generator voltage, generator power factor.

Start Date – 25/5/12 End Date – 28/5/12

Test 2 - Confirm the efficiency decreases in the converter over partial load applications

A series of tests with the rpm of the rig set to a constant value whilst the torque is varied on the generator and hence the electrical

load.

Measurements Required - RPM, input torque on ARC shaft, generator current, generator voltage, generator power factor,

converter input voltage, converter input current, converter output voltage, converter output current.


Test 3 - Program the theoretical operating curve and ensure correct tracking over the course of a tidal exchange (up to rated

velocity) –

Power input up is slowly ramped-up (simulating an increase in water velocity) in constant increments equivalent to 0.1m/s. SM

ensure that the control system tracks the turbine RPM with that of a constant tip speed ratio (TSR) which is set to the design TSR.

SM will monitor the generator output and turbine rpm to ensure that their control system influences the turbine so that it follows

the expected theoretical operating curve. This will confirm the theoretical power curve for this operating region as well as

confirmation of the point tracking along the operating curve, previously developed by SM. This will be integrated with the control

algorithm implemented by SM and used to control the turbine during accelerated lifecycle testing.

Measurements Required - RPM, input Torque on ARC shaft, generator current, generator voltage, generator power factor,

converter input voltage, converter input current, converter output voltage, converter output current.


2.2.2 DriveTrainEfficiencyMapping

Efficiency testing was conducted in a stepped approach so that a comprehensive Speed vs. Load vs. Drive Train Efficiency

relationship could be defined. Since the accuracy of the recorded power input of Nautilus was ill-defined for smaller loads (due


Rev. 01, 19-Sep-2013

of 20

to transducer measurements being subject to error) the testing was restricted to torque loads of 0.25-1.0 pu and a shaft speed of

0.4-1.0 pu.

The procedure was as follows:

Step 1 A ‘ready for test’ signal was announced by the control to Nautilus. Narec set an initial torque reference equivalent to

0.25pu of the nominal generator torque (146kNm) through the Nautilus rig. Testing began with a speed reference

manually through the AR1000 control system. The initial speed reference was set at 0.4pu of the nominal generator speed

(72RPM). Three minutes of continuous data was recorded.

Step 2 Once three minutes were recorded the speed reference was increased by 0.05pu and the procedure repeated until a

maximum speed of 1pu was achieved.

Step 3 After data had been collected for a set torque value for the full envelope of operating speeds (0.4–1pu of the generator)

an increased torque reference was set by Narec and the process was repeated until a generator torque of 1pu was

achieved.

2.2.3 ThermalMapping

The thermal characteristics of each of drive train components and the nacelle walls were investigated. Whilst these tests do not

present an exact replica of conditions found subsea, the results provided a worst case heating scenario for the drive train

components and the nacelle. This provided valuable feedback on potential problem areas as well as indicating how operating

conditions affect heating.

Thermal testing was conducted with all hatches on the AR1000 closed to the external air and the generator cooling system

delivering cool water to the top of the generator housing. The following procedure was followed during the test:

Step 1 A ‘ready for test’ signal was sent to Nautilus. Narec set the initial torque reference at 300kNm through the Nautilus rig.

The generator speed reference was set at 1pu (72RPM). 5 minutes of continuous data was then recorded.

Step 2 Once 5 minutes of continuous data was recorded; it was signalled to Narec to ramp the torque up by 100kNm. Speed was

kept constant. 5 minutes of continuous data was recorded.

Step 3 Once torque of 0.95MNm was reached, 60 minutes of continuous data was recorded at this set point (960kW).

Step 4 Once 60 minutes of continuous data was obtained the speed was dropped to 0.8pu and the Narec torque was dropped

to 600kNm (430kW). 60 minutes of continuous data was recorded at this set point.

Step 5 Once this test was completed it was signalled to Narec to end the test and complete system shut down was initiated.

Note: Thermal data can also be extracted from both the efficiency and accelerated life tests. However, in these instances the flaps

of the AR 1000 were open and a fan was blown into the nacelle at the location of the gearbox to aid simulation of subsea cooling.

As it is likely to be harsher operating conditions than subsea, where the water cools the nacelle more efficiently than air, the

results here can be seen as conservative.

2.2.4 ControlSystemTestingControl system testing was implemented in order to investigate the automated response of the in-built control algorithm and

ensure it tracked the operating curve over the course of a simulated tidal exchange. The dynamic response of the algorithm was

tested although an allowance was required to be made for the large increase in system inertia whilst testing at Narec, as opposed

to testing subsea with blades attached.

The procedure was as follows:

Step 1 AR1000 set to run in automated control mode and issue a ‘ready to test’ signal to Nautilus.

Step 2 Once the ‘ready to test’ signal was received by Narec, Nautilus WAS switched to torque reference control and began to

run a torque profile simulating a single tidal cycle from a cut-in water speed, up to a maximum water speed of 2.65 and

then back down to the same cut-in water speed following a sinusoidal wave. This tidal cycle was taken directly from the

predicted tidal flow at the European Marine Energy Centre (EMEC) on 12th January 2012 with a maximum flow speed of


Rev. 01, 19-Sep-2013

of 20

2.92 m/s and a total period of 6hrs 11 minutes. The total testing time at which the AR1000 was above the cut-in speed

was 3hrs 41 minutes.

Step 3 Nautilus then referenced a series of Look Up Tables (LUTs) to determine the correct torque to apply. By determining the

time elapsed, Nautilus referenced the correct LUT for the corresponding water speed.

Step 4 The rpm from the system was utilised by Nautilus as an input to their control system and referenced this against the LUT

to determine if at any given time the system is at the correct operating point. If the system is at the correct operating

point the torque input to the system will be as per the torque profile.

If, however, the control system was to vary the speed away from the optimal operating point the Nautilus system will be

designed to behave like the function of the water on the blades in terms of input torque to the shaft, i.e. following the

correct torque speed characteristic curve associated with the AR1000 blades for the given water speed.

Step 5 Nautilus will, in effect, add or subtract torque on top of the programmed torque profile based on the current water speed

LUT. The rpm is used to determine what torque value should be added or subtracted. For example if the control system

slows the system then typically based on the behaviour of the water on the blades at sea the turbine would be subjected

to higher input torques corresponding to the blade characteristic torque speed curve. Likewise if the system is sped up

this would lead to lower torque values. This is a more accurate simulation of the driving torque to test the AR1000 control

system behaviour.

Step 6 How the control system behaves in automated mode is determined and tested whether it brings the system to the

desired steady state optimal set point within a satisfactory timeframe.

2.2.5 AcceleratedLifeTestingAccelerated life testing was undertaken to demonstrate robustness and reliability of the AR1000 and control system integrity. The

objective was to operate the AR 1000 for a continuous period equivalent to more than 3 months of power generation under

simulated ocean conditions, with the tidal profile extracted from tidal predictions at the EMEC site for the period of 1st January

2012 to 30th April 2012, as shown below. The period includes eight spring tides in which constructive interference between lunar

and solar tide components results in a larger tidal range and higher current speeds. The figures show that at the EMEC site there

is a significant difference between the flood (east to west moving) and ebb (west to east moving) tides. The flood tide is

approximately 0.3 – 0.6 m/s greater than the ebb tide.

Figure 1 Monthly Tidal Flow (l); 3-day Tidal Current Speed (r)

Step 1 AR1000 set to run in automated control mode, ‘ready to test’ signal issued to Nautilus.

Step 2 Nautilus operates a continuous sinusoidal tidal exchange from 1 to 2.65m/s water speed within a 20 minute duration.

The torque profile is set up to repeat as soon as it has finished so that the turbine is in continuous operation.

Step 3 The Nautilus control system and the AR1000 control system both set to shut down in the event of a critical alarm. This

enabled long uninterrupted periods of operation for the system. During night time an ARC representative was onsite in

the ARC control cabin to ensure in the event of an incident the system came to a satisfactory stop.


Rev. 01, 19-Sep-2013

of 20

Step 4 After a period of continuous operation of approximately 22 hours the system is brought to a stop to allow the system to

cool down. During this time the doors of the Nautilus test room were opened to reduce the ambient temperature in the

rig and the water in the cooling system drained and replaced with cold water.

Step 5 Once the water in the cooling system had reached the required level the test was continued at the point at which it had

been adjourned.

2.2.6 BrakeTestingThe mechanical brake was only partially-tested due to the dynamics of the NAREC system and the speed in which the AR1000

brake applies full torque. Functionality via an over-speed trip as well as a manual application of the brake torque at various applied

values was achieved. This manual application brake test was performed at a low rotational speed - 30RPM drive side/9.2RPM

generator, with the brake brought to the feather position. (Approx. 46bar/0kNm) plates are still able to rotate at this hydraulic

pressure, and then incrementally increased torque by releasing the brake pressure until the mechanical brake was deemed to be

providing too much torque on the Narec drive train and subsequently released.

The over-speed trip limit test was performed during Narec commissioning and was performed via the inherent safety system

coded within the PLC programme. This occurred at nominal speed of the generator (72RPM) and again at 10% above nominal.

Each of the latter tests resulted in the shear tubes of the coupler having to be replaced thus additional brake testing was then

eliminated from the test programme due to concerns regarding the stress placed on the Narec drive coupler in the event of the

oil tubes sheering.

2.3 RESULTS&ANALYSIS

2.3.1 DriveTrainEfficiencyMappingData produced by both the AR1000 SCADA and the Nautilus data acquisition system contained a degree of scatter due to

Electromagnetic Interference (EMI) and momentary sampling errors. In order to avoid spurious measurements contaminating the

efficiency calculation, both ��and �� were filtered at each load and speed setting. The filtering took the form of a temporal

average over the duration of the subtest. The average was then used to window the time-dependent power measures, discarding

all readings that were either higher than 110% or lower than 90% of the average. The efficiency was then calculated by averaging

the accepted measures.

This testing enabled the determination of the torque and speed versus efficiency characteristics to be established at all rotational

speeds so that the turbine drive train could be fully understood. The following table and graph shows the calculated efficiencies

at the various generator operating points.

Figure 2 Generator Speed vs. SCADA Control (l); Nautilus drive torque temporal evolution (r)

Figure 2 above demonstrates the procedure by which the efficiency mapping was achieved. For each input torque set point (r) a

range of shaft speeds were enforced and regulated by the AR1000 Proportional Integral (PI) controller module with the

Supervisory Control and Data Acquisition (SCADA) unit. Each test point was maintained for a period of approximately three

minutes in order to extract an average efficiency measure.

The maximum efficiency of CP max = 0.9 was determined for the AR1000 drivetrain operating at a torque of 1.0pu and a shaft speed

of 0.9pu. Our expectation of maximum system efficiency (based on non-generator losses of 4-6% and generator losses of


Rev. 01, 19-Sep-2013

of 20

4-5%) was 89-92%. The results at near or full load were within expectations.

Figure 3 Drive Train Efficiency as a function of Generator Load & Speed

2.3.2 ThermalMapping

Figure 4 Variation of Generator shaft rotational speed (l); Generator Output Power during Test

The figures above show the variation of shaft speed and power output

respectively for the duration of the thermal testing. The largest temperature rise

is experienced at the generator windings, as Figure 5 shows below:

After synchronisation of Nautilus and the AR1000 and a period of operation at a

low power output, the shaft rotational speed was increased by 1pu and the input

torque increased at intervals of 100 kNm (Step 2). The corresponding rise in

generator power output produced a rapid rise in the temperature at the generator

windings. The gradient of the temperature rise increased with additional load

until the maximum test load was reached, indicating the start of Step 3. During

Step 2 the water in the cooling tank rose in temperature as heat energy was

removed from the generator housing. The rate of temperature increase in the

cooling tank is far smaller than that of the generator windings causing the temperature

differential between the coolant and the generator housing to escalate. Since the energy extracted by the coolant is proportional

to the temperature differential, the gradient of the temperature rise began to decrease during Step 3 and is approximated by a

linear gradient of 20°C/hr.

Figure 5 Generator Windings Test Temp


Rev. 01, 19-Sep-2013

of 20

The generator load was reduced significantly at the start of Step 4 and then maintained constant for the period of one hour. An

immediate decrease in temperature at the generator windings is evident in Figure 6 which eventually stabilise to a constant

temperature of approximately 57°C. The constant winding temperatures suggest that heat produced by the generator is balanced

by that extracted by the cooling system. The gradient of the temperature rise of water within the cooling tank reduces as less

heat energy is extracted from the generator housing walls.

2.3.3 ControlSystemTestingThe input torque recorded at the Nautilus drive corresponding to the

sinusoidal velocity profile is shown in Figure 9. The input torque is

limited at a minimum torque of 250 kNm resulting in the initially flat

profile before time t = 1000s. Between 4900s < t < 9300s the equivalent

tidal velocity is above rated resulting in the constant maximum torque.

Control of the turbine is demonstrated in Figure 10, which shows the

reference speed for the AR1000 PI controller and the response of the

shaft speed. Throughout the test period the shaft speed remains stable

and accurate to within 5% of the PI reference speed, which is set by the

LUTs within the Programmable Logic Controller (PLC). Stability and

control is maintained in spite of fluctuations in the Nautilus Drive

Torque, which are particularly prevalent at the maximum drive torque.

2.3.4 AcceleratedLifeTestingNoting that the turbine was subject to a more continuous load compared with when it is offshore (where normally there would

be two hours of non-generation at the end of each tide in which to cool down), the results were extremely positive. The turbine

was only stopped for one cool-down period in each simulated month, and never faulted during operation. Automatic control was

not compromised and the turbine did not have to be stopped for any reason during its continuous operation runs.

The total power generated by the AR1000 was integrated over the duration of the accelerated life test and is shown below. The

accumulated testing time was 83.60 hours which represents a turbine operating in an equivalent tidal flow for 3.85 months

generating 0.58 GWhr of electricity. The turbine was operated at approximately 10% below peak power to ensure a safety factor

on overheating, therefore the corrected equivalent annualised output was approximately 2.05GWhr, which is within tolerance of

our expected power return of a year of operation at EMEC at 95% availability.

Figure 6 Variation of Nautilus Drive Torque with Time

Figure 7 PI Controller Ref Speed with

Resultant Shaft Speed


Rev. 01, 19-Sep-2013

of 20

Period Test

Duration (hr)

Power

(MWhr) Equivalent

Duration (hr)

Equivalent Power

Output (GWhr)

Day 1 22.76 7.91 409.7 0.14

Day 2 21.36 8.12 384.5 0.15

Day 3 21.65 8.42 389.6 0.15

Day 4 17.83 7.62 320.9 0.14

Total 83.60 32.1 1504.7 0.58

Figure 7 Summation of Power Generated during Accelerated Life Test and its Equivalent Power


Rev. 01, 19-Sep-2013

of 20

3 MAINLEARNINGOUTCOMES

3.1 PROGRESSMADE

Objective: Details: Result:

1 Final tuning of the pre-commissioned third-party

Converter and Control components to complete the

supplier contract requirements. This would allow future

tests to be run at a considerable cost reduction as the

need to re-engage the suppliers would be minimised or

removed completely.

Achieved. The vast majority of the post-

commissioning tuning works allocated to Smart

Motor and ABB in regards to their shore-based

electrical systems was completed.

2 Provision of thermal characteristics of power train

components to feed into the Detailed Design of the next-

generation turbine.

Achieved. Thermal information of the system over

the full operating envelope of load and speed was

gathered.

3 Study the performance of the brake and optimise use

within an automated control system.

The brake functionality was tested at low loads.

Full analysis of the brake was limited by the

operating restrictions of the Nautilus test rig. Full

load application of the brake results in the

application of a large counter torque on the

Nautilus drive shaft, which is sufficient to shear the

coupling between Nautilus and the AR1000. Full

load brake testing has been postponed until re-

deployment for safety reasons.

4 Investigate the efficiency of the turbine across its full

operational envelope.

Achieved. The turbine was operated over a

comprehensive range of system input conditions

and an efficiency map produced.

5 Carry out Control System testing to observe the

automated system behaviour and tune the algorithm

based on theoretical assumptions for blade characteristics

and system inertia correction factors.

The HV closed loop control and synchronisation to

the generator during start-up were tuned during

the Narec testing enabling the AR1000 to operate

in fully automated control.

6 Conduct accelerated lifecycle testing on the turbine to

provide continuous running hours data for the turbine.

The AR1000 performed without failure or

overheating for the entire testing period. Over 3

months of equivalent power production was

achieved.

3.1.1 NextStepsThe AR1000 unit performed to a high level during testing and this analysis has been fed into development of the next-generation

AR1500 tidal turbine to further drive efficiency and reliability.

3.1.2 ProgressMade:ForMarineRenewableEnergyIndustryThe work carried out at Narec was the inaugural testing using the 3MW drive train facility.

The series of tests to confirm the drive train’s efficiency, control system validation and analysis of component thermal properties

under a full electrical load through accelerated life tests have helped to advance the tidal turbine development cycle considerably,

whilst showcasing Narec as an important test facility for developers within the industry.


Rev. 01, 19-Sep-2013

of 20

3.2 KEYLESSONSLEARNED• Control system validation in a controlled environment was invaluable and accelerated the process from doing

this with the turbine installed and waiting for the right conditions to present themselves.

• Generator and gearbox thermal signatures could be mapped easily with this system, allowing for this

information to be fed back into design validation and future designs

• Early mechanical problems with the system were highlighted easily in a dry controlled environment,

whichcould then could be rectified quickly and cheaply.

• These tests gave us a greater level of understanding of our machine and helped validate the performance of

the components and the system as a whole that we could not achieve without doing this style of drive train

testing.

• Braking tests were far more difficult to simulate than had been foreseen owing to the fact that there were in

fact two control systems at work during each of the tests. For the complete set of braking tests to be carried

out next time we will need to modify the Nautilus system so that these tests can be performed successfully

and safely.

4 FURTHERINFORMATION

4.1 SCIENTIFICPUBLICATIONSIt is intended to submit content for publication regarding the Thermal Analysis carried out during testing, potentially

with the Institution of Mechanical Engineers or a body of a similar stature.

4.2 WEBSITE&SOCIALMEDIAWebsite: www.smartmotor.no

www.atlantisresourcescorporation.com

YouTube Link(s):

Narec 3MW tidal turbine drive train testing:

http://www.youtube.com/watch?v=hmZ0R0cuXhI

5 REFERENCES3023-ARC-Narec Summary Test Report

6 APPENDICES

6.1 STAGEDEVELOPMENTSUMMARYTABLEThe 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.


Rev. 01, 19-Sep-2013

of 20

user-project : tempest tidal energy mobilisation, proving ... · tidal energy mobilisation, proving...

Documents