Dynamic Loadings on Turbines in a Tidal Array (DyLoTTA)

Lead Research Organisation: Cardiff University
Department Name: Sch of Engineering

Abstract

The research will investigate the nature of the loading patterns imparted onto tidal stream turbines when positioned and operated within an array and develop operational procedures to mitigate the impacts of these extreme loading patterns. Exposure to open sea wave climates with high wave-current interactions will influence the power generating, structural integrity, product durability and maintenance requirements of the technologies deployed. The research will undertake both experimental and numerical analyses in a manner that will make the results and findings transferable to real-life implementations. This will inform developers of the peak and fluctuating loads that devices are exposed to in a commercial array environment and will also identify and test mitigating actions to be implemented in order to ensure the robustness and sustainability of the array.
The dynamic, cyclic loadings on a tidal stream turbine have been shown to depend on the current profile and wave characteristics which can increase the severity of these loads. This must be considered in the design of the turbine. A turbine in an array will be subjected to more complex flows due to its position in the array, which will result in more diverse loading patterns, which must be fully understood by the turbine designers and operators.
The project will therefore evaluate and measure the loading and performance of different configurations of tidal stream turbine arrays using numerical modelling and model scaled experiments. The numerical modelling will use fluid and structural modelling. An existing and proven, instrumented, laboratory scale turbine design will used for the tests. Initial work on a three turbine array will be undertaken to create models of a full-scale turbine array to determine the power output, loading patterns and accurate life-fatigue analysis based on realistic site deployment conditions. This information will be formulated to provide a basis for the industry to evaluate anticipated performance, monitoring needs, operational best practice and maintenance regimes in order to deliver the lowest cost of energy from tidal arrays

Planned Impact

The impact of this research will directly effect decisions made by marine renewable technology developers; regulatory compliance bodies; Government and Legislative agencies developing policy; International standards bodies; investors, insurers and array developers. This provides the additional confidence necessary for the next stages of evolution for the marine renewables industry.

Better understanding of the loadings and fatigue induced in dynamic sea conditions will enable marine renewable technology developers to better design their product for operational conditions and more accurately schedule servicing requirements and intervals without relying on expensive over-engineering as per current practice, this delivering a more cost effective product.

Regulatory compliance bodies (DNV/ GL, LR etc.) will benefit from this new knowledge and understanding to enable more informed and apposite development of design codes used for undertaking compulsory third party verification. Ensuring codes are appropriate and fit for purpose and not merely an adaption of offshore engineering codes from the oil and gas sector.

Government and Legislative agencies, The Crown Estate, Regional and Local Authorities, etc responsible for developing policies for marine renewable deployment will be informed as to the nature of sites which can cost effectively harness marine renewable resource, and use this to deliver more realistic policies on enabling and quantifying resource extraction capabilities and which locations/ sites can be more cost effectively utilised in the early stages of commercial development of the marine renewable sector.

International Standards bodies, in the form of IEC Technical Committee 114 and IEA OES, will be informed with more accurate information on resource dynamics and resulting intensity, how this interacts with marine renewable technology and impacts on performance in order to inform standards being developed for device performance quantification, energy predictions from arrays and the cost of energy from marine renewable arrays.

Delivery of more accurate load quantification techniques will provide Insurers and investors with higher levels of confidence in assessing risk associated with array development and operations. Such premiums can be a considerable overhead on project costs, more accurate information associated with loads, fatigue and failure will allow premiums to be more reflective of risk while and minimise inbuilt contingency costs. This will reduce array project costs being experienced by investors and array developers and will deliver a lower levelised cost of energy from the project.
 
Description Design of a more advanced test turbine which includes more instrumentation for robustness and the ability to capture dynamic loads.
Design of a blade with improved peak power coefficient.
Testing has taken place with two turbines and variable turbulence levels and upstream turbine wakes. The data has proven to be high quality and is helping to determine turbine spatial limits within arrays. Testing with 3 turbines in Flowave in a number of spatial configurations and flow directions. Tidal turbine array spacing can not be considered in the same way as wind turbine arrays due to the high levels of forces.
Operation of the turbines in wave and profiled currents have been conducted. These flow conditions can result in significant increases in the fluctuations of power and load, whilst maintaining a reasonable average set of values.
Future testing will take place after the end of project in IFREMER with 2 turbines, turbulence, waves and yaw.

Reynolds scaling of turbine characteristic is possible from Laboratory scale models.
Exploitation Route This will eventually provide detailed effects of wave-current-structure-wake turbulence effects and array arrangements.
The data provide evidence for developers regarding turbine spacing to optimise on power and survivability. Some overlapping with upstream turbines can promote an increase in average power output without significant increases in fluctuations.
Operating a turbine in speed control results in high levels of torque fluctuations, where as operating in torque regulated mode results in increased thrust fluctuations.
Fundamental turbine characteristics can be found at laboratory scale provided the Reynolds number is high enough and in the turbine is operated in the area of independence.
Wave - profiled currents can cause significant fluctuation in loads and power, especially if the blade TDC position coincides with wave crests. Control mechanisms should be implemented in order to mitigate rotational speed and wave frequency matching.
Sectors Energy

 
Description International Advisory Board Member, Pan-American Marine Energy Conference. Mr Johnstone
Geographic Reach Multiple continents/international 
Policy Influence Type Participation in a advisory committee
 
Description Feasibility in Energy 2017
Amount £197,000 (GBP)
Funding ID EP/R000875/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 10/2017 
End 09/2018
 
Description Impact Acceleration Account
Amount £46,462 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 09/2017 
End 08/2018
 
Description Marinet2
Amount € 45,000 (EUR)
Funding ID project no. 1340 
Organisation European Union 
Sector Public
Country European Union (EU)
Start 11/2017 
End 11/2017
 
Description Newton Fund
Amount £80,000 (GBP)
Funding ID 332324562 
Organisation British Council 
Department British Council - Newton Fund
Sector Public
Country United Kingdom
Start 04/2018 
End 03/2019
 
Description Tidal Array Control and Optimisation of Energy (TACOE), Supergen Flex-Fund, 1 week of testing at Flowave,
Amount £15,000 (GBP)
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 02/2019 
End 12/2019
 
Title Horizontal Axis Tidal Turbine Flume Testing Data 
Description The data provided is the result of the Flume Testing used to develop and test Condition Monitoring system and algorithms. The data is for an optimum turbine rotor set up, with blade offsets of 6 degrees. Three sets of flume experiments were conducted for flow velocities of 0.9 m/s, 1.0 m/s and 1.1 m/s. Flume data was obtained by testing for the following seven values of l: 1.5, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.5. In this way parametric surface were developed which creating a characterisation of the turbine operation under a variety of operating conditions. 
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Title The specification of and testing of a Horizontal Axis Tidal Turbine Rotor Monitoring approach 
Description DATA Set Created at Cardiff University based on research presented in the IJPHM paper, 'the specification of and testing of a horizontal axis tidal turbine rotor monitoring approach.' List of Data Files: CFD_DATA.mat InitialSimsTI000_0.mat InitialSimsTI000_5.mat InitialSimsTI001_0.mat InitialSimsTI002_0.mat InitialSimsTI010_0.mat CMMetricsTI000_5.mat CMMetricsTI001_0.mat CMMetricsTI002_0.mat CMMetricsTI010_5.mat ClassificationResultsTI000_5.mat ClassificationResultsTI001_0.mat ClassificationResultsTI002_0.mat ClassificationResultsTI010_0.mat FluidTimSeriesTI010_0.mat Ct.txt TSR.txt INFORMATION on DATA FILES: CFD_Data: This data set in the form of matlab structure contains data from the CFD models undertaken to produce the paramertisation data for the model detailed in the paper. CTC - Vector containing the non-dimensional torque curve for the turbine rotor being studied. ITSR - The Tip-Speed-Ration indexes for the above torque curve. Steady_State_Parameters--|-Optimum----|--CFD Data : CFD TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm). | |--Model Data: Details of the CFD model - Rotor Radius (m), Rotational Velocity (Rad/s), Mean Fluid Velocity (m/s). | |-Off6_5-----|--CFD Data: CFD TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm). | |--Model Data: Details of the CFD model - Rotor Radius (m), Rotational Velocity (Rad/s), Mean Fluid Velocity (m/s). | |-Off9-------|--CFD Data: CFD TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm). | |--Model Data: Details of the CFD model - Rotor Radius (m), Rotational Velocity (Rad/s), Mean Fluid Velocity (m/s). | |-Off12------|--CFD Data: CFD TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm). |--Model Data: Details of the CFD model - Rotor Radius (m), Rotational Velocity (Rad/s), Mean Fluid Velocity (m/s). InititalSimsTIxxx_x: Here XXX_X is the TI for the simulation contained in the matlab workspace e.g. InitialSimsTI010_0.mat contains the simulation results for the TI = 10% simulations. CTC - Vector containing the non-dimensional torque curve for the turbine rotor being studied. ITSR - The Tip-Speed-Ration indexes for the above torque curve. Steady_State_Parameters--|-Optimum----|--CFD Data : CFD TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm). | |--Model Data: Details of the CFD model - Rotor Radius (m), Rotational Velocity (Rad/s), Mean Fluid Velocity (m/s). | |-Off6_5-----|--CFD Data: CFD TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm). | |--Model Data: Details of the CFD model - Rotor Radius (m), Rotational Velocity (Rad/s), Mean Fluid Velocity (m/s). | |-Off9-------|--CFD Data: CFD TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm). | |--Model Data: Details of the CFD model - Rotor Radius (m), Rotational Velocity (Rad/s), Mean Fluid Velocity (m/s). | |-Off12------|--CFD Data: CFD TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm). |--Model Data: Details of the CFD model - Rotor Radius (m), Rotational Velocity (Rad/s), Mean Fluid Velocity (m/s). SteadyStateSimulation----|-Optimum----(1 to i)|--SimInfo: Gives all the information used to create the simulation. This includes the parameters used for the model detailed in [1] and the turbine information. | |--SimResults: Model TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm), FluidVelocity (m/s). | |-Off6_5-----(1 to i)|--SimInfo: Gives all the information used to create the simulation. This includes the parameters used for the model detailed in [1] and the turbine information. | |--SimResults: Model TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm), FluidVelocity (m/s). | |-Off9-------(1 to i)|--SimInfo: - Gives all the information used to create the simulation. This includes the parameters used for the model detailed in [1] and the turbine information. | |--SimResults: Model TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm), FluidVelocity (m/s). | |-Off12------(1 to i)|--SimInfo: - Gives all the information used to create the simulation. This includes the parameters used for the model detailed in [1] and the turbine information. |--SimResults: Model TimeStamp (Seconds), Rotor Position (Degrees), Tootal Torque (Nm), Torque Contribution Blade1 (Nm), Torque Contribution Blade2 (Nm), Torque Contribution Blade3 (Nm), FluidVelocity (m/s). NOTE: 1 to i refer to the simualtion number. for cases InitialSimsTI000_5, InitialSimsTI001_0 and InitialSimsTI002_0 there are 50 cases, i.e. i = 50. For the InitialSimsTI010_0 case there are 10 cases, i.e i = 10. CMMetricsTIxxx_x: Here XXX_X is the TI for the simulation contained in the matlab workspace e.g. CMMetricsTI010_0.mat contains the condition monitoring metrics outlined in [1] for the TI = 10% simulations. NormCMData: Matrix (4 by (number of simulations x number of fault cases)) The matrix contains the normalised condition monitoring metrics detailed in [1], each row contains a specific metrix i.e row 1 contains CM metric 1 (as defined in [1]). In the case of the TI000_5 to TI002_0 cases, there are 50 simulations of 4 differing rotor conditions, resulting in 200 columns. The first 50 contain data relatig to the optimum case and so on, in the order 'Optimum', 'Off6_5', 'Off9', 'Off12'. This data was used to train the NBCs detailed in [1]. ClassificationResultsTIxx_x: Here XXX_X is the TI for the simulation contained in the matlab workspace e.g. ClassificationResultsTI010_0.mat contains the cNBC results for the TI = 10% simulations. For Each fault case the following variables provide the results of the testing of the trained NBCs, trained as detailed in [1]. The case in the variable title refers to the condition of the data inputted into the NBC> NBClabel___: The MAP classification results for the inputted data set. NBCPosterior___: Posterior probability returned via the NBC for the inputted dataset. nbccOSToPT___: Cost of making the classification for the inputted data. FluidTimeSeriesTI010_0: Fluid time series generated via the process outline in Appendix A of [1] ct.txt Non-Dimensional Torque Curve, for the rotor. TSR.txt. Tip-Speed ratio index for the ct curve. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
Impact The outputs from the data sets has allowed the development of three turbines for turbine interaction testing. The data from all three turbines have been characterised and produce very close characteristics to each other. Publication is under review and data sets will be produced subsequently. 
 
Title Three instrumented turbines development 
Description Three instrumented turbines have been developed with (almost) identical characteristics. Each turbine is capable of providing measurements for: 1. Individual blade load measurements in both span and edgewise directions. 2. Total thrust and torque. 3. Rotational position and speed. 4. Motor Voltage and Current (torque and power) 5. 3 axis vibrations via an accelerometer mounted on the stanchion. Testing undertaken at Kelvin Hydrodynamic Laboratory, CNR-INM, IFREMER and Flowave. 
Type Of Material Data analysis technique 
Year Produced 2020 
Provided To Others? No  
Impact Understanding of: 1. Turbine interaction with turbulent flows. 2. Turbine interaction with full and partial wake of downstream turbines. 3. Turbine interaction with misaligned flows. 
 
Description Extended testing of turbines 
Organisation French Research Institute for the Exploitation of the Sea
Country France 
Sector Public 
PI Contribution We provided the turbines and the turbulence generation grids for the testing. In addition we provided some of the personnel for the testing.
Collaborator Contribution Access to the flume for 2 weeks. Personnel and velocity measurement equipment and expertise.
Impact To date one joint Journal paper is under review and four further papers are being prepared. Three conference papers for presentation at the 2020 AWTEC have been submitted. When published these will be entered into the relevant section of the form.
Start Year 2018
 
Description Turbine blade composite materials 
Organisation U.S. Department of Energy
Department National Renewable Energy Laboratory (NREL)
Country United States 
Sector Public 
PI Contribution The collaboration was agreed after an organised workshop in Tidal energy. The outcome was to assess the use of composite materials for the blade design used for this project. As a result of this project funding has been secured by both NREL and the DyLoTTA partners, through MARINET 2 for 3 weeks of testing in IFREMER, with a member of NREL taking an active part.
Collaborator Contribution With the expertise in wind energy and the use of composite materials for blades. The staff at NREL have looked at the use of composites to produce the blades, designed for this project by the partners.
Impact Paper: R Murray et al. Modeling and manufacturing of a thermoplastic carbon-fiber tidal turbine blade, 13th EWTEC, Naples, (2019)
Start Year 2018
 
Description Turbine testing 
Organisation French Research Institute for the Exploitation of the Sea
Country French Polynesia 
Sector Academic/University 
PI Contribution Using IAA grant we are contributing 50% (£40000) of the required funds to provide an extensive testing compaign.
Collaborator Contribution IFREMER are providing access to their flume along with expertise.
Impact testing in April and July 2018. A number of papers have been published (see publications) and are either under review or being written with joint authorship of the partners and IFREMER staff. Additional testing in April 2020 (access through MARINET 2) will provide further collaboration regarding turbine turbulence and wake interaction.
Start Year 2018
 
Description Attended workshops in India 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact as part of a UKIERI programme to explore the opportunities for the Sunderban area of West Bengal to introduce tidal/hydrokinetic energy devices. Discussions were between academics from both the UK and India, British High commission and West Bengal politicians.
Year(s) Of Engagement Activity 2018
 
Description European Wave and Tidal Energy Conference. Technical Committee member - Prof O'Doherty 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact membership of the technical committee is by invitation and recognises the persons expertise and experience in the marine energy field. The acitivity is to advice the EWTEC and to support the successful delivery of the conferences.
Year(s) Of Engagement Activity 2015,2017,2019
URL https://ewtec.org/
 
Description European Wave and Tidal Energy Conference. Technical Committee member - Dr Ordonez-Sanchez 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Membership of the Technical Committee is through invitation only and is made up of multinationals. The invitation recognised the persons expertise in the marine energy field of R&D. It provides the technical advice to the EWTEC and provides support for the successful running of the conferences.
Year(s) Of Engagement Activity 2019
URL https://ewtec.org/
 
Description Global Green Hub Korea conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact T O'Doherty and C Johnstone - Invited speakers at the Marine Energy session at the GGHK conference. Presentations made on the needs for research into tidal energy for structural reliability (carried out under the DyLoTTA project) and the industrial perspective of tidal energy generation. This was particuarly aimed at the Korean marine energy industry and research community. Questions were raised concerning development of devices with non uniform sea loading.
Year(s) Of Engagement Activity 2017
 
Description Invited participation by the British Council (Mexico) and SENER to discuss UK-Mexico collaboration in energy. 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact This meeting has been put together to provide direction to aide in Mexico's strategical energy plan for the XXI century. Four areas are Building Energy, Material, energy storage and offshore renewables. 12 UK experts were invited to take part - two in offshore renewables. This outcomes are to inform future Newton fund calls and possible SENER funding.
Year(s) Of Engagement Activity 2017
 
Description Pan-American Marine Energy Conference. Technical Committee member - Dr Ordonez-Sanchez 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Membership of the technical committee is by invitation only. The technical committee acts as an technical advisory board to the organisers of the conferences. This is a new series of conferences and has the main aim to develop the 'home' marine energy community in the international field.
Year(s) Of Engagement Activity 2019
 
Description Tidal energy workshop with the National Renewable energy Laboratories (NREL) - USA 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact This was a joint activity with NREL staff and DyLoTTA project members. The workshop included an overview of the project activities and the wider tidal energy research activities. Areas of interest that sparked questions was the question of loading issues and site effects on the design requirements of devices. In addition material selection for the tidal industry was discussed with regard to the requirements of the wind and tidal devices. Collaborative areas of interest were explored.
Year(s) Of Engagement Activity 2018
 
Description project meeting with international partner (Mississippi State Universaity) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact As part of the project we will hold one meeting per year at an international partners site. This meeting took place at the end of a secondment by a researcher to MSU. Presentations were made of the progress made by both the UK and MSU partners. The work was discussed in relation to the project findings/needs and wider ranging findings. The interaction of the researchers was found to be very good and the relationship between the partners growing stronger. Future publications and possible areas for further collaboration were discussed.
Year(s) Of Engagement Activity 2018