Prifysgol Caerdydd, Caerdydd, UK

Welcome A message from the chair of the 6th PRIMaRE 2019.

Dear PRIMaRE Delegates A warm welcome to the 6th PRIMaRE

Conference hosted by The School of Engineering, Cardiff University, Cardiff, Wales. We have a busy programme to get through the next few days (3rd and 4th July 2019). There will be 25 peer reviewed technical talks, 7 invited industrial speakers, poster display, panel discussion. As in previous years, the last being in Bristol, Southampton, Bath, Penryn, and Plymouth, the quality of submissions has been excellent. We decided to emulate last year’s conference in Bristol and have a mixed session covering wave, tidal, environmental and other associated fields. This helps to promote discussion across disciplines and keep a focus on the common challenges and new opportunities of marine renewable energy. Professor Tim O’Doherty Professor at the School of Engineering, Cardiff University. www.odoherty@cardiff.ac.uk

Venue The PRIMaRE conference presentations

and posters will be held in The School of Engineering, The Queen’s Buildings, Newport Rd. Directions to the Conference can be found here: https://www.cardiff.ac.uk/events/view/1477940-6th-primare-conference-2019 Also See Appendix 1 of this programme for the School location and Floor Plan of the Queen’s Buildings, showing the way to rooms Central Building (C1.09) and the faculty Lecture theatre (T2.09) in the Trevithick Building.

Talks and panels will be held at location: (A) Trevithick building (T2.09) Posters Coffee and lunches will be at location (B) Central building (C1.09)

Accommodation. If you are still looking for somewhere to stay during the conference or after, Info on accommodation can be found here: http://www.visitcardiff.com/tag/accommodation/

Presentation. All technical talk slots are 12 mins (will be in T2.09) including questions, so please allow time for change over. Please allow time before each session to upload your presentations.

Posters

Poster boards will be provided for each A1 poster in location (B) Central Buildings C1.09 (see floor plan in Appendix 1) from 10am on 3rd July. Means for fixing the posters will be provided. The main times for viewing the posters will be during breaks and lunchtimes.

Refreshments, Lunch and Conference Dinner

Lunch, morning and afternoon refreshments will be served in Central Buildings C1.09

The conference dinner will be held at the Ty Madeira Restaurant, 32 St. Mary Street, Cardiff, South Wales, CF10 1AB on Wednesday evening 3rd July at 20:00.

Vegetarian options will be available. If you require any other special dietary requirements during your time at the conference please make yourself known to a member of the conference team.

Internet Eduroam is available in the University venues.

Contact

In case of an emergency during the conference, please call 029 20 875941 to speak to one of the local organisers.

Croeso

Neges gan gadeirydd 6ed PRIMaRE 2019

Annwyl cynrhychiolwyr PRIMaRE

Croeso cynnes i 6ed gynhadledd

PRIMaRE sydd yn cael ei chynnal gan Ysgol

Peirianneg, Prifysgol Caerdydd, Caerdydd,

Cymru. Mae rhaglen brysur a llawn o’n blaenau

dros y dyddiau nesaf (3ydd a 4ydd o Fehefin

2019). Mi fydd 25 sgwrs dechnegol wedi eu

hadolygu gan gyfoedion, 7 siaradwr gwadd

diwydiannol, arddangosfa posteri a thrafodaeth

panel. Yn dilyn cynadleddau blaenorol, yr olaf

ym Mryste, Southampton, Bath, Penryn a

Plymouth, mae ansawdd y cyflwyniadau eto

eleni yn ardderchog. Fe benderfynwyd efelychu

cynhadledd llynedd ym Mrsyte trwy gynnal

sesiynau cymysg sydd yn cynnwys ton, llanw,

amgylchedd a meysydd cysylltiedig. Mae hyn yn

annog trafodaeth ar draws disgyblaethau

gwahanol a chadw ffocws ar y heriau cyffredin

a chyfleoedd o fewn ynni morol.

Yr athro Tim O’Doherty

Athro yn Ysgol Peirianneg, Prifysgol Caerdydd.

www.odoherty@cardiff.ac.uk

Lleoliad

Mi fydd cyflwyniadau cynhadledd

PRIMaRE a’r posteri yn cael eu cynnal yn yr

Ysgol Peireianneg, Adeilad y Frenhines,

Newport Rd.

Ceir cyfarwyddiadau i’r gynhaledd yma:

https://www.cardiff.ac.uk/events/view/14779

40-6th-primare-conference-2019

Ewch i atodiad 1 o’r rhaglen i ddarganfod

lleoliad yr ysgol, ac i weld cynllun llawr Adeilad

y Frenhines, sydd hefyd yn dangos y ffordd i

ystafelloedd yr adeilad canolog (C1.09), y

ddarlithfa cyfadran (T2.09) yn adeilad

Trevithick.

Mi fydd y sgyrsiau a’r paneli yn cael eu cynnal

yn lleoliad (A) Adeilad Trevithick (T2.09).

Posteri, coffi a cinio a’r gael yn lleoliad (B)

Adeilad Canolog (C1.09).

Llety

Os yr ydych chi dal yn chwilio am rywle i aros yn

ystod y gynhaledd, ceir gwybodaeth am lety yma:

https://www.visitcardiff.com/tag/accommodation/

Cyflwyniadau

Mi fydd y sgyrsiau technegol yn 12 munud o hyd gan

gynnwys cwestiynnau, felly gadewch ychydig o

amser ar gyfer newid drosodd. Gadewch amser cyn

pob sesiwn i lwytho eich cylwyniad.

Posteri

Mi fydd bwrdd poster ar gael i bob poster (A1) yn

lleoliad (B) Adeilad Canolog C1.09 (gwelwch gynllun

llawr yr adeilad yn atodiad 1) o 10:00y.b. ar y 3ydd o

Fehefin. Bydd dull o osod y poster ar gael. Y prif

amser i arsylwi y posteri fydd yn ystod egwyl a

chinio.

Lluniaeth, Cinio a Phryd Nos y gynhadledd

Cinio, lluniaeth bore a phrynhawn yn cael eu

cynnal yn yr Adeilad Canolog C1.09

Mi fydd pryd nos y gynhadledd yn cael ei gynnal

yn Ty Madeira, 32 St Mary Street, Caerdydd, De

Cymru, CF10 1AB ar nos Fercher, y 3ydd o

Fehefin 20:00

Mae opsiwn llysieuol ar gael. Os oes angen

gofynion dietegol arbennig arall yn ystod eich

amser yn y gynhadledd, a wnewch chi roi

gwybod i aelod o dim y gynhadledd.

Y we

Mae Eduroam ar gael ym mhob adeilad y Brifysgol.

Cyswllt

Mewn argyfwng yn ystod y gynhaledd, plis

cysylltwch â 029 20 875941 er mwyn siarad gyda un

o’r trefnwyr.

Invited speakers biographies

Fraser Johnson was a Chief Officer with the UK Merchant Navy. After

receiving his Masters from the University of Plymouth, he began his

involvement with Ocean Energy working for a number of wave energy

technologies. He is currently the O&M Manager for the 6MW array and has

responsibility for the operation and maintenance of the offshore and

onshore assets.”

Cam Algie is the Chief Technology Officer at Bombora Wave Power where

he oversees the research and development of mWaveTM technology. He

is responsible for converter design coordination, modelling and analysis,

he works closely with a range of wave energy experts globally to lead

Bombora’s device performance development. He has significant project

experience previously working as a successful entrepreneur in the West

Australian minerals industry. Prior to this, his work within the maritime

industry provided him with valuable practical experience of marine

mechanical systems in ocean environments. He is currently utilizing the

latest in modelling technology to adapt mWave to a broad range of real-

world environments, and to support detailed engineering of mWave for

specific project sites.

Daniel Coles is the Resource Analyst at SIMEC Atlantis Energy. Since joining

in July 2017, he has taken the lead role in the power curve testing of the

MeyGen Phase 1A turbines, resource assessment, array and cost of energy

optimisation, energy storage modelling and environmental impact

assessment. He has disseminated his work in multiple leading international

conference/journal proceedings, and contributes to the relevant

International Electrotechnical Commission standards for tidal stream

energy. He holds a Master’s degree in Mechanical Engineering from the

University of Manchester and a PhD in tidal turbine array modelling from

the University of Southampton, where he is an adjunct fellow. Before

joining SIMEC Atlantis Energy, he held a postdoctoral research associate

post at Imperial College London. He is the recent recipient of the Analyst

Award at the Young Professionals Green Energy Awards 2019, presented

by Scottish Renewables.

Paul Taylor is a Principal Consultant at Intertek. He is Intertek’s

modelling/technical manager, with 20 years’ experience in marine, coastal

and estuarine environmental consultancy. After gaining his MSc in Physical

Oceanography, he initially worked on offshore geophysical surveys, and

then as a marine environmental modelling consultant. He has worked in the

water industry since joining Metoc plc (now Intertek Energy and Water) in

2003, undertaking a varied range of hydrodynamic and water quality

modelling assessments for water companies throughout the UK. These

include reservoir studies, riverine, and estuarine Water Framework

Directive assessments, and bathing and shellfish water compliance projects.

Tom O’Mahoney is Senior Advisor at Deltares in the Unit Hydraulic

Engineering. He has a degree in Mathematics and a PhD in Fluids Engineering

with a specialization in Computational Fluid Dynamics (CFD). In his current

role he has works on projects related to the hydrodynamics around hydraulic

structures like sluices, locks and weirs, mostly involving validation of CFD

models against lab or field data In particular he has been involved in projects

for the Swansea Bay Tidal Lagoon and Tidal Turbines in the Eastern Scheldt

Barrier in the Netherlands.

Rob Spice is a Mechanical Engineer contributing to both the offshore and

onshore renewable energy groups at ITPEnergised. He graduated with a 1st

class Honours degree in Motorsport Engineering (BEng) from Oxford Brookes

University and was awarded a distinction by the University of Exeter for a

Masters in Renewable Energy Engineering (MSc). His work is primarily focused

on two areas, namely, the design and analysis of mechanical and structural

components and systems for use in the renewable energy sector, and

technical due diligence and asset management of onshore renewables.

Martin Murphy is the Chair of Marine Energy Wales. He has spent his career

in the marine sector, in the Royal Navy for 12 years followed by 15 years in

corporate industry, firstly for Alstom Power Conversion, and then L-3

Communications Ltd. In 2009, he joined Tidal Energy Limited leading the

company to the installation in 2015 of its full-scale DeltaStream device in

Pembrokeshire. He has been a Non-Executive Director of Pembrokeshire

Coastal Forum for 5 years and chairs Marine Energy Wales. In 2015 -16 he was

the 113th President of the Institute of Marine Engineering Science and

Technology (IMarEST) and is now the Institute’s Honorary Treasurer.

SESSION SPEAKER AFFILIATION TITLE

Wednesday 3RD JULY

Registration and Refreshments, Central (C1.09) 09:15 – 10:15

Session 1 Time Start time - 10.15 Chair: Tim O'Doherty

INVITED 10:15 Fraser Johnson Meygen/Simec Atlantis

MeyGen – The world’s largest tidal array; Construction, Operation and Commercialisation

ID-93 10:40 A J Goward Brown

Bangor Impact of tidal stream site interconnectivity on resource assessment

ID-96 10:53 R Ellis Cardiff Comparison of numerical software for predicting the performance of a horizontal axis tidal turbine

ID-92 11:06 J Ji Plymouth Use of carbon fibre textile reinforced concretes in marine constructions

ID-134 11:19 L Yang Cranfield Unified one-fluid simulation for floating wave energy converters

ID-135 11:32 D White Southampton Through-life coupling between mooring loads and anchor capacity

Refreshments, Central (C1.09) 11:45 - 12:15

Session 2 Time Start time - 12.15 pm Chair: Deborah Greaves

INVITED 12:15 Cam Algie Bombora Wave Power Talk title held for Paul Vigars

ID-164 12:40 F Khalid Exeter Risk-return site characterisation for offshore wind energy

ID-120 12:53 E Katsidoniotaki Uppsala Extreme load analysis of point absorbing wave energy converters

ID-105 13:06 S Michele Loughborough Weakly nonlinear theory for an array of curved oscillating wave surge converters

ID-121 13:19 S Brown Plymouth Validating a numerical tool for evaluating floating tidal systems

ID-100 13:32 JJ Waggitt Bangor Topography, currents and foraging seabirds in coastal environments: identifying subtle effects of marine renewable energy installations

Lunch and Poster Display, Central (C1.09) 13:45 – 14:30

SESSION SPEAKER AFFILIATION TITLE

Session 3 Time Start time - 14.30 pm Chair: Allan Mason-Jones

INVITED 14:30 Dan Coles Simec Atlantis Commercial scale tidal stream turbine development

ID-116 14:55 M De Dominicis

NOC, Liverpool Effects on hydrodynamics and ecological costs of climate change and tidal stream energy extraction in a shelf sea

ID-98 15:08 S Zheng Plymouth Theoretical modelling of multiple OWCs along a straight coast/breakwater

ID-90 15:21 T Griffiths Western Australia Recent research on hydrodynamic forces for seabed cables

ID-94 15:34 P Ouro Cardiff Development of a digital offshore farm simulator: designing future tidal

turbine arrays using a high-fidelity computational model

ID-89 15:47 M Lewis Bangor Improving methods of characterising resource, interactions and conditions at tidal energy sites: the METRIC project

Refreshments, Central (C1.09) 16:00 – 16:30

Session 4 Time Start time 16.30 Chair: Paul Harper

INVITED 16:30 Paul Taylor Intertek Applying lessons learned and techniques from other industries to the marine Renewables sector

ID-101 16:55 MJ Harrold Exeter Prototype testing the intelligent mooring systems for floating wind turbines

ID-110 17:08 E Mills Dundee Modification of concrete surfaces to reduce colonisation by marine invasive species

ID-117 17:21 G Rinaldi Exeter Experimental modelling of a parachute-type tidal energy converter

ID-125 17:34 Z Liao Queen Mary Linear non-causal optimal control of multi-float multi-mode wave energy converter M4

ID-112 17:47 G. Veneruso Bangor An applied approach to investigating cetacean collision risk from tidal turbines

CONFERENCE DINNER, Ty Madeira, St Mary’s Street 20.00

SESSION SPEAKER AFFILIATION TITLE

Thursday 4th JULY

Session 5 Time Start time - 09.00 Chair: Jun Zang

INVITED 09:00 Tom O’Mahoney Deltares Combining near and farfield effects in tidal energy

ID-106 09:25 J Hughes Swansea Using WEC-Sim to model focused wave interaction with floating bodies

ID-122 09:38 H Ding Bath Parametric investigation of an integrated WEC-type breakwater system

ID-88 09:51 J Demmer Bangor Can offshore wind farms impact mussel settlement and connectivity in the Irish sea?

ID-137 10:04 B Guo Cardiff Modelling tidal range structures using Delft3D and Telemac2D

Refreshments, Central (C1.09) 10:20 - 11:00

Session 6 Time Start time - 11.00 am Chair: 'Bakr Bahaj

INVITED 11:00 Rob Spice ITPowerEnergised Design of Floating Platforms for Tidal Turbines

INVITED 11:25 Martin Murphy Marine Energy Wales Continuing Progress for Marine Renewable Energy in Wales

INVITED 11:50 QUESTION TIME Panel Members Questions to panel

Conference handover and lunch 12:45

Panel Members Company

FRASER JOHNSON MEYGEN/SIMEC ATLANTIS

CAM ALGIE BOMBORA WAVE POWER

TOM O’MAHONEY DELTARES

MARTIN MURPHY MARINE ENERGY WALES

PAUL TAYLOR INTERTEK

CAMERON JOHNSTONE NAUTRICITY

ROB SPICE ITPowerEnergised

DAN COLES Simec Atlantis

4th July, WORKSHOP: 14.00 -16.00 DESIGN OF TIDAL TURBINES - FROM LAB TO COMMERCIAL SCALE This workshop is linked with the EPSRC funded project DyLoTTA (EP/N020782) Dynamic Loading on Turbines in a Tidal Array. 1 Introduction - Load issues and knowledge requirements - needed for design. 2 Blade design methodology: BEMT, CFD, structure. 3 Turbine design at small scale process instrumentation. 4 Design philosophy at large scale 5 Discussion

Poster Presentations

IDs Author poster presentations (C1.09) Location

87 N. Xie Developing the Green Offshore Energy System Plymouth

97 Mathieu Caron Effects of flow depth on the wake structure of tidal stream turbine arrays.

Cardiff, Ecole Polytechnique, France

100 A Richard Heard The INSITE Programme: Building the science around Man-made Structures in the Marine Ecosystem.

UK

102 I. Fairley Global Wave Resource Classification Using A clustering Approach Swansea

105 E. Faraggiana Time domain simulation of the WaveSub device under multi-directional waves.

Swansea

107 Tongtong Zhang Liquid air energy storage system integrated with thermoelectric power generator as an efficient way for the storage, transplant and recovery of offshore wind power

Birmingham

108 D.M. Wang Use of HF radar for replicating wave conditions from testing of wave energy converters with different regrouping methods

Plymouth

115 I. Collins Literature Survey of Flexible Membranes for Wave energy Converters

Swansea

118 Q.Ye Structure design and assessment of a floating foundation for offshore wind turbines.

Plymouth, Ireland

119 A.J. Hillis Active control of the WaveSub WEC for increased power capture Bath

124 C. Lloyd CFD surface effects on flow conditions and tidal stream turbine performance.

Cardiff

128 G. Kallis Public engagement with energy transitions: An exploration of the challenges of engaging island communities

Plymouth, Exeter

129 Yao Zhang An advanced robust wave excitation force estimation framework based on adaptive sliding mode observer

Queens London

130 C. Leech Hydro-environmental modelling of wake dynamics of turbines and sluices in tidal range schemes

Cardiff

131 E. Rojo-Zazueta The initial characterisation of a tidal stream turbine on a drive train test rig on steady state conditions

Cardiff, Ecole Polytechnique, France

133 A. Peccin Macro-element of marine anchors for floating offshore structures subjected to cyclic loads

Bristol

136 B. Ranabhat Experimental Testing and Numerical Study of a Turbine for Hydroelectricity

Cardiff,

127 Y Xu Turbulent flow features around a circular monopile Glasgow

PRIMaRE Committee and Partners

PRIMaRE is a consortium of marine energy experts across higher education, research and industry that have

joined together to establish a ‘network of excellence’ for the south of the UK.

Steering Committee

AbuBakr Bahaj (University of Southampton) Claire Gibson (Wave Hub) Deborah Greaves (Plymouth University) Johnny Gowdy (Regen) Jan Hardwick (University of Exeter) Jan Zang (University of Bath) Kerry Hayes (Regen) Tim O’Doherty (Cardiff University) Lars Johanning (University of Exeter) Melanie Austen (Plymouth marine Laboratory) Paul Harper (Bristol University) Phillippe Blondel (University of Bath) Ricardo Torres (Plymouth Marine Laboratory) Stuart Herbert (Wave Hub) Tara Hooper (Plymouth Marine Laboratory)

Organizing Committee Tim O'Doherty, Cardiff University Matthew Allmark, Cardiff University Allan Mason-Jones, Cardiff University Catherine Lloyd, Cardiff University Rob Ellis, Cardiff University Paul Prickett, Cardiff University Carl Byrne, Cardiff University Roger Grosvenor, Cardiff University Edith Rojo Zazueta, Cardiff University Scott Brown, University of Plymouth

Acknowledgements Jennifer Gurney Tattiana Hernandez Madrigal Edith Rojo Zazueta Mabli Williams James Bain

Abstracts (3rd and 4th July, 2019)

(87-199-1-SM) Developing the Green Offshore Energy System N. Xie1, A. Linley1, D. Greaves1 1University of Plymouth, School of Engineering, nan.xie@plymouth.ac.uk 1University of Plymouth, School of Engineering, annie.linley@plymouth.ac.uk 1University of Plymouth, School of Engineering, deborah.greaves@plymouth.ac.uk KEYWORDS: Hydrogen, Offshore renewable energy, Oil and gas infrastructure, System approach Multiple drivers are now behind transformation of the offshore energy system, with offshore wind

expanding rapidly, shipping and ports transforming their operations to reduce emissions, O&G

companies decommissioning and redefining their role as energy producers. One possible routine to

develop the potential of hydrogen in decarbonizing the offshore energy system, is through the use of

offshore renewable energy for conversion of electrical energy into hydrogen on existing O&G

platforms, which is then stored or transported onshore via pipelines or cryogenically in ships.

Hydrogen is a green energy carrier. In this paper, a roadmap is proposed for developing the green

offshore energy system starting from offshore renewable energy to hydrogen end users. A literature

review was carried out to identify opportunities and challenges within this process. These include

major expansion and improvement in collaboration between offshore industry sectors, government

and the whole system research community to bring much clearer strategic focus to development of

hydrogen economy and to identify technical, policy and governance barriers to optimizing these

system and improving their economic viability.

(88-201-1-SM) Can offshore wind farms impact mussel settlement and connectivity in the Irish Sea? J. Demmer1, P. Robins1, S. Neill1, S.Malham1, T.Jones2 1Bangor University, School of Ocean Sciences, osp816@bangor.ac.uk 2Extramussel limited, trevormussels@yahoo.com KEYWORDS: Mussel Settlement, Hydrodynamic Modelling, Offshore Wind Farms, Connectivity Larval dispersal is a function of 1) larval transport (which is also a function of physical transport and

larval behaviour), 2) survival, 3) spawning and 4) settlement [1]. Larval transport and settlement

depends on physical process (tides, currents, winds) and larval behavior [2]. Mussels (mytilus edulis

L.) represent 40 to 50 % of the total gross turnover of Welsh shellfish industries and the industry has

been operating sustainably for over 50 years in North Wales. In this context, it is the interest for

Mussels companies to understand where the larvae go in order to manage their stocks efficiently. A

2D hydrodynamic model in Telemac is applied to simulate the tide around the North welsh coast from

Anglesey to Liverpool Bay. Then a particle tracking model under Matlab is used to understand the

larval dispersal and recruitment. The preliminary results of the model showed that a proportion of

mussel larvae (between 15% and 20% depending on the tide of release) are carried away from their

native mussel bed to an area where the wind farms are implanted. Indeed, Gwynt yn Mor (the fourth

largest wind farm in the world), Rhyl flat and North Hoyle are located between 10 and 15 km off the

welsh coast. Furthermore, the larvae, which reached this area, seemed to come from different mussel

beds. Results also showed that this area promote self–recruitment and consequently connectivity

among the different mussel populations. In this state of mind, the wind farms represent a potential

site of interest for mussel larvae settlement. Consequently, it could have both negative (less

settlement onshore for mussel companies) and positive (improvement of larval survival) impact.

(89-203-1-SM) Improving Methods of Characterising Resource, Interactions and Conditions at Tidal Energy Sites: The METRIC project Matt Lewis1

1School of Ocean Sciences, Bangor University, UK

KEYWORDS: Tidal-energy, resource assessment, oceanographic conditions, modelling It is essential that the global resource, and likely conditions, are understood so that the design of the

next generation of devices has global deployment capability. Furthermore, the potential for tidal

energy to make meaningful contributions to renewable energy targets needs to be quantified and

communicated so the industry is supported correctly. METRIC’s aims and research will be presented

at the conference to reduce uncertainty in the distribution of the global tidal energy resource and

better understand variability within likely ocean conditions. Global tidal resource assessments are

presently based on coarse, data constrained, models that are not validated for the few tidal energy

sites resolved. The global resource is therefore only broadly known, and may contain unknown bias as

present methods are applied from other ocean science applications (e.g. quantifying global energy

budgets). For example, comparison of global oceanographic data to a bespoke high-resolution ocean

model of the UK finds sites identified as suitable for tidal-stream development was under-estimated

by 69%. A bespoke tidal model with a blended grid (Delft dflowfm), and forced with tidal generating

forces (GTSM), has been developed to map the global tide resource and understand likely upper limits

of development. A method of downscaling tidal-stream resource model data (i.e. tidal velocity at

hourly outputs) to electricity at time-scales useful to end-users (i.e. 0.5 Hz) will also be presented. The

next steps of METRIC project aims to develop methods to support the industry as it evolves beyond

the fast, shallow, well-mixed and wave sheltered sites.

(90-205-1-SM) Recent research on hydrodynamic forces for seabed cables T. Griffiths1, Y. Teng2, S. Draper1,3, D. White1,4, H. An3, H. Mohr3, L. Cheng3 1University of Western Australia, Oceans Graduate School, terry.griffiths@uwa.edu.au 2International Joint Laboratory on Offshore Oil & Gas Engineering, Dalian University of Technology 3University of Western Australia, Dept. of Civil, Environmental and Mining Engineering, University of Southampton KEYWORDS: Seabed cables, rocky seabeds, hydrodynamic forces The on-bottom stability design of subsea pipelines and cables is important to ensure safety and reliability but can be challenging to achieve, particularly for renewable energy projects which are preferentially located in high energy metocean environments. Often these conditions lead to the seabed being stripped of all loose sediment, leaving the cables to rest on exposed bedrock where roughness features can be similar in size to the cables. As offshore renewable energy projects progress

from concept demonstration to commercial-scale developments, new approaches are needed to capture the relevant physics for small diameter cables on rocky seabeds to reduce the costs and risks of export power transmission and increase operational reliability. Recent experimental testing using the University of Western Australia's unique Large O-tube has enabled the experimental measurement of hydrodynamic forces on small diameter cables and pipes in proximity to smooth and rough beds. The tested conditions extend well beyond the existing published parameter range including much higher KC conditions together with seabed roughness which is comparable in size to the diameter. The results provide design data of great relevance to the ongoing development of marine renewable and conventional oil and gas projects, especially on rocky seabeds. This paper presents typical test results and gives an illustrative worked example to support tentative conclusions on the likely outcomes from this work, which are anticipated to be encapsulated in a new British Standard for seabed cable on-bottom stability design.

(92-207-1-SM) USE OF CARBON FIBRE TEXTILE REINFORCED CONCRETES IN MARINE CONSTRUCTIONS Jie Ji School of Engineering, University of Plymouth, jie.ji@plymouth.ac.uk KEYWORDS: Carbon Fibre, Textile Reinforced Concrete, Marine Constructions, Tensile Test, Pull-out Test With the development of marine engineering, traditional reinforced concrete composed by steel rebar and Portland cement gradually becomes difficult to meet demands of constructions situated in offshore area, including those constructions which are used for offshore renewable energy exploitation. On the one hand, concrete made by normal Portland cement and aggregates would be damaged by sulphate ion in seawater as time goes by. On the other hand, steel rebar would be corroded by chloride ion in seawater over time. The mentioned above drawbacks cause a serious durability problem of constructions. To explore the solution to this problem, carbon fibre textile reinforced mortar become an alternative to the traditional building materials. Carbon fibre textile mesh made by carbon fibre is almost corrosion free in seawater with normal temperature [1]. Moreover, the project tries to use PFA and GGBS which partially replace normal Portland cement. This will help the mortar resist the damage from sulphate ion in seawater and improve its compactness. Therefore this composite material will be equal to marine environment. Experimental methods are applied in the investigation of this new material, including plate tensile test, cylinder pull-out test and beam bending test. Tensile test focuses on the tensile strength and toughness of the composite material while pull-out test focuses on its bond property at interface between mortar matrix and carbon fibre textile mesh. Existing research has demonstrated that bond strength determined the structure ultimate strength and serviceability limit state design [2]. Fatigue bending test by small-size beams explores the structure durability of this composite material. Relevant work having done so far proves that each single carbon fibre strand embedded in plate constituted by this material has a

reasonable tensile strength with 2.1 GPa in average. Its bond strength is more than 5 MPa. Its durability will be explored by subsequent tests through accelerated aging method and applying fatigue load. (93-209-1-SM) Impact of Tidal Stream Site Interconnectivity on Resource Assessments A.J. Goward Brown#1, M.J. Lewis*, P. Robins*, S. P. Neill* #Centre for Applied Marine Sciences / *School of Ocean Sciences, Bangor University Menai Bridge, LL59 5AB, UK 1Corresponding author: a.j.gowardbrown@bangor.ac.uk KEYWORDS: ROMS, MARINE RENEWABLE ENERGY, TIDAL STREAM, TIDAL ENERGY EXTRACTION, RESOURCE ASSESSMENT Tidal energy is a growing area in both industry and research. Tidal energy can be extracted using

barrage, array (TEC) and lagoon technologies. Globally there are a large number of sites that have

been identified as suitable for tidal stream energy extraction. The energetic UK shelf seas are a prime

location for the development of tidal stream energy [1]. Fast tidal streams occur where the

propagating tidal wave is constrained. In some parts of the UK shelf seas a number of sites of been

leased within a relatively confined area. Tidal stream device installations will interact with the

unconstrained tidal resource. Neighbouring sites can alter another’s available resource [2]. It could be

argued that nearby development sites should therefore be included in resource assessments and

environmental impact assessments, however, using 3-D modelling techniques, Fairley et al. [3],

determined that the cumulative impact of the 4 planned array’s in the Pentland Firth is equal to the

sum of the impacts of each individual array. However, the authors acknowledge that larger scale

developments could lead to increasingly complex neighbouring interactions. This research uses a 3-D

ROMS (Regional Ocean Modelling System) model of the Pentland Firth and Orkney region, at a high

resolution (~100m), using bathymetry available from the GEBCO and Digimap datasets, available at

1/120⁰ and 30m respectively, and tidal boundary forcing provided by the FES2012 dataset, available

at 1/16⁰. Tidal stream energy extraction is included as an adaptation of the method described by [4]

as mid-depth force term. Each of the tidal stream sites was parameterised by the information available

to the authors at the time of the experiment. Each array was designed to be sited at the mid-depth of

the water column and energy is extracted over the entire leased site, at the rated power of the

proposed array. The focus of this research is the extent to which tidal array installations will affect the

available resource at neighbouring tidal array sites and the effective cumulative impact of multiple

array installations. Initially the array is limited to the Inner Sound site but in subsequent simulations,

all the leased sites in the Pentland Firth are developed. Results show an increase in available resource

at some of the neighbouring sites with a reduction at others. The site directly downstream of the Inner

Sound development faces the largest consequence of neighbouring tidal stream extraction than the

sites on the opposite side of the channel.

(94-211-1-SM) Development of a Digital Offshore Farm Simulator: designing future tidal turbine arrays using a high-fidelity computational model Pablo Ouro1, Magnus Harrold2, Luis Ramirez3

1Hydro-environmental Research Centre, School of Engineering, Cardiff University, CF24 3AA, Cardiff, UK, ourop@cardiff.ac.uk 2College of Engineering, Mathematics and Physical Sciences, The University of Exeter, TR10 9FE, Penryn, UK, m.j.harrold@exeter.ac.uk 3Group of Numerical Methods in Engineering, School of Civil Engineering, University of A Coruña, Spain, luis.ramirez@udc.es KEYWORDS: Tidal turbine arrays, large-eddy simulation, fluid-structure interaction, digital twin, turbulence The most recent progress of the tidal energy industry is the deployment of small arrays comprising up to a maximum of four turbines. Projects such as enFAIT [1], led by Nova Innovation Ltd, are looking at understanding how turbines interact between them under wake shadowing effects, which will help to reduce uncertainties related to power generation and structural loads. With the aim of improving the design of arrays of turbines, a Digital Offshore FArm Simulator (DOFAS) is here developed to accurately represent the working conditions of future tidal turbine farms. The DOFAS is based on the highly-accurate method of large-eddy simulation equipped with an actuator line model and immersed boundary method for the representation of tidal turbines and bathymetry, respectively [2-4]. An important feature of DOFAS is its hybrid parallelization with Message Passing Interface (MPI) and OpenMP, allowing it to effectively compute high-resolution simulations with a reasonable amount of computational resources. A first test case to validate DOFAS comprises the simulation of seven tidal stream turbines at laboratory scale, in two rows of three and four turbines. Results show that DOFAS captures the most relevant instantaneous flow phenomena, e.g. wake meandering or tip vortices, mean velocity field and also structural loads on the devices. The front-row turbines suffer the largest fatigue loads since they face the undisturbed approach flow, whilst the outermost turbines in the second-row undergo large tower yaw moments variations due to partially facing the fast-flowing ambient flow and low-momentum wake from the upstream turbines [2]. The holistic nature of DOFAS

will serve as a design tool for researchers and industry, to design turbine arrays considering the maximisation of energy generation as well as the reduction of extreme and fatigue loads. Future developments of DOFAS will focus on improved computational scalability and application to full-scale tidal turbines [5].

(96-214-1-SM) Comparison of numerical software for predicting the performance of a horizontal axis tidal turbine R. Ellis1, J. Bowman2, M. Allmark1, S. Bhushan2, D. Thompson2, A. Mason-Jones1, T. O’Doherty1

1Cardiff University, Engineering Department, ellisr10@cardiff.ac.uk 2Mississippi State University, Centre for Advanced Vehicular Systems, jb1060@msstate.edu KEYWORDS: ANSYS CFX, Computational Fluid Dynamics, Marine Energy, OpenFOAM, Tidal Stream Turbine As the global community, and more locally the UK, look to move away from the burning of finite fossil fuels, marine energy extraction has gained greater interest as one possible alternative energy resource. In part this is due to the perceived impact that wave and tidal energy extraction could have in helping achieve the desired renewable energy targets of 20% that the UK are trying to hit by 2020 [1]. A small number of projects around the UK coastline are starting to highlight the potential that could be achieved, however these are both costly and time consuming. To help mitigate this cost and time factor a large number of small-scale tests are being, and have been, undertaken at several facilities [2], [3]. The use of small-scale testing allows a platform from which computational models can be validated and compared to when looking at the performance of tidal stream turbines under a variety of flow conditions. The use of computational fluid dynamics (CFD) allows for a rapid and cheap alternative when determining a preliminary estimate for the performance of a horizontal axis tidal turbine. Previous studies have shown that CFD can be used to produce accurate predictions, especially when looking at the performance of a tidal turbine, however emphasis needs to be placed on the solver and the set-up of the model in question to ensure the conditions are being represented as accurately as possible. This paper aims to look at comparing the prediction of a tidal stream turbine using the commercial code ANSYS CFX and the open source code OpenFOAM. Alongside producing repeatable results, the implementation of the desired boundary conditions was compared. The numerical simulations were run using the same geometry, mesh and turbulence model on both software. The results were compared to experimental testing conducted at INSEAN. The setup for each model is detailed. Differences were noted in the running and setup of the models as well as within the time history of the results. Overall both CFX and OpenFOAM were shown to give good predictions for the performance coefficients compared to the experimental testing with the data averaged over several experiments. (97-216-1-SM) Effects of flow depth on the wake structure of tidal stream turbine arrays Mathieu Caron1,2, Pablo Ouro1

1Hydro-environmental Research Centre, School of Engineering, Cardiff University, CF24 3AA Cardiff UK, caronmd@cardiff.ac.uk , ourop@cardiff.ac.u k 2Ecole polytechnique, 91120 Palaiseau France, mathieu.caron@polytechnique.edu KEYWORDS: Tidal turbine arrays, large-eddy simulation, fluid-structure interaction, water depth, wake recovery Tidal stream turbine array layouts have to be designed to produce energy under various operating conditions. They differ from wind turbine arrays because of the limited water depth found at shallow tidal channels. This flow constraint can impact the wake structure, including the wake velocity recovery, and can determine the energy generation capabilities of secondary turbine array rows. Hence, it is necessary to carry out a study to identify the wake differences depending on the water depth and understand the varying mechanisms involved in the wake recovery. A Digital Offshore FArm Simulator (DOFAS) [1] is used to accurately predict the flow through a tidal turbine farm at four water depths. The DOFAS is based on the highly-accurate method of large-eddy simulation equipped with

an actuator line model and immersed boundary method for the representation of tidal turbines and bathymetry, respectively [1-3]. The experimental tests from Stallard et al. [4], in which turbines operated in a very shallow flow, with a relative water depth of less than two equivalent turbine diameters, are used to validate DOFAS results. These simulations complete the knowledge from other experimental studies [5] with new analyses about how the relative water depth affects the wake dynamics. Similarly to previous studies for wind turbines [6], we compare the flow features for the four different depths and quantify the recovery of kinetic energy, which has been linked to the available power for secondary rows of turbines. It is interesting to note that turbulent fluxes have a great influence on kinetic energy recovery with the transport of mean kinetic energy due to Reynolds stress being determinant. Focusing on the production of turbulent kinetic energy allows us to study the fatigue loads depending on the water depth, with the goal to determine the variation of the working conditions for the turbines. (98-218-1-SM) Theoretical modelling of multiple OWCs along a straight coast/breakwater S. Zheng1, A. Antonini2, Y. Zhang3, D. Greaves1, J. Miles1, G. Iglesias4,1 1School of Engineering, University of Plymouth, Plymouth PL4 8AA, United Kingdom 2Department of Hydraulic Engineering, Delft University of Technology, The Netherlands 3State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing, 100084, China 4MaREI, Environmental Research Institute & School of Engineering, University College Cork, Ireland siming.zheng@plymouth.ac.uk KEYWORDS: Wave Energy, Potential Flow Theory, Theoretical Model, Wave Power Extraction The integration of oscillating water column (OWC) wave energy converters into a coastal structure (breakwater [1], pile [2], etc.) or, more generally, their installation along the coast is an effective way to increase the accessibility of wave power exploitation. In this paper, a theoretical model is developed based on the linear potential flow theory and eigenfunction matching method [3] to evaluate the hydrodynamic performance of an array of OWCs installed along a vertical straight coast. The chamber of each OWC consists of a hollow vertical circular cylinder, which is half embedded in the wall. The OWC chambers in the theoretical model may have different sizes, i.e., different values of the radius, wall thickness and submergence. At the top of each chamber, a Wells turbine is installed to extract power. The effects of the Wells turbine together with the air compressibility are taken into account as a linear power take-off system [4]. The hydrodynamic and wave power extraction performance of the multiple coast-integrated OWCs is compared with that of a single offshore/coast-integrated OWC and of multiple offshore OWCs. More specifically, the role of the wave incident angles, chamber size (i.e., radius, wall thickness and submergence), spacing between OWCs and number of OWCs are analysed using a theoretical model. It is shown that wave power extraction from the coast-integrated OWCs for a certain range of wave conditions can be significantly enhanced due to both the constructive array effect and the constructive coast effect. For any certain wave frequency, there is a general identity of the optimum wave capture factor over all incidence angles that multiple coast-integrated OWCs must hold regardless of the OWC dimension. It means a higher peak in the curve of wave power capture factor at some incidence angles must be associated with less power absorption at other incident angles. (99-220-1-SM) Topography, currents and foraging seabirds in coastal environments: identifying subtle effects of Marine Renewable Energy Installations J.J Waggitt1, J. Bond1, B. Brown1, P.W. Cazenave2, P.G.H. Evans1,3, N. Goldsmith1, L.M. Howarth4, J.G. Hiddink1, J. Short1, R. Torres2, J. van der Kooij5, G. Veneruso1, S.J.Fraser6 1School Of Ocean Sciences, Bangor University, Menai Bridge, Anglesey, UK. j.waggitt@bangor.ac.uk 2Plymouth Marine Laboratory, Plymouth, UK. 3Sea Watch Foundation, Bull Bay, Anglesey, UK. 4Life Sciences Centre, Dalhousie University, Halifax, Canada. 5Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, UK. 6NAFC Marine Centre, Scalloway, UK. KEYWORDS:Foraging Ecology, Habitat-Use, Spatial Overlap, Environmental Impacts

Interactions between currents and topography influence the distributions of seabirds in coastal

environments. Tidal fronts between mixed and stratified water-columns, shear-lines and eddies

around islands/headlands and internal-waves across bank systems all provide animals with

predictable and expoitable foraging opportunities. By changing currents and topography, marine

renewable energy installations (MREI) have the potential to impact foraging seabirds by modifying

prey availability. Predicting impacts requires an understanding of the relative role of currents and

topography in the creation of foraging opportunities, and the ability to estimate variations habitat-

use among locations. To achieve this understanding, researchers must compare locations showing

different combinations of topography and currents, identifying how changes in these components

alters habitat-use. This presentation summarises studies across several locations in the UK and

Europe, and proposes future studies building upon their findings. In particular, these studies show: (1)

the importance of trade-offs between different measurements of prey availability, with animals

selecting physical conditions which maximise foraging efficiency, (2) a diminishing importance of

currents and topography in coastal environments heavily influenced by meterological events and (3)

that increased current speeds could enhance the extent of foraging opportunities, allowing animals to

exploit a wider range of habitats. In combination, these results have started to tease apart the relative

roles of environmental processes in coastal environments, and identify scenarios when MREI could

impact seabird communities. By steering developments towards habitats where the likelihood of

impacts are reduced, these studies have important roles in the environmentally sustainable growth

the of MREI sector.

(100-222-1-SM) The INSITE Programme: Building the Science around Man-made Structures in the Marine Ecosystem A. Richard Heard1 1INSITE Programme Director, richard.heard@insitenorthsea.org KEYWORDS: Environmental Impact, Energy Policy, Regulation, Data, Decommissioning The INSITE Programme [1] is an industry-NERC funded research project which aims to provide stakeholders with the independent scientific evidence-base needed to better understand the influence of man-made structures on the ecosystem of the North Sea. Its scientific objectives are to help establish: a) the magnitude of the effects of man-made structures compared to the spatial and temporal variability of the North Sea ecosystem, considered on different time and space scales; and b) to what extent, if any, the man-made structures in the North Sea represent a large inter-connected hard substrate system. The £2.4Million Phase 1 was launched in 2015 and delivered eight research projects. At the end of 2017 the first phase of research concluded. Some 38 scientific papers from INSITE Phase 1 science are in preparation, under review or being planned. The Programme has established itself as a focal point for marine research around man-made structures in the North Sea. INSITE Phase 2, with combined industry and NERC funding of £7.6Million was launched in 2018, attracting recognition and support from industry, government and the scientific community through NERC. The public debate around what is the ‘right thing to do’ with man-made structures such as oil and gas and renewable energy installations at the end of their useful life is gathering pace as more structures are being considered for decommissioning. This research aims at ensuring the current regulatory framework around decommissioning is robust and the decisions made are truly evidence-based. The science being produced under INSITE will support decision making around all anthropogenic structures in the marine environment. This presentation will describe the unique governance structure of INSITE developed to ensure its independence, the scientific progress made in INSITE Phase 1, the ongoing science programme and novel approach to industry data sharing developed in Phase 2. (101-224-1-SM) Prototype Testing the Intelligent Mooring System for Floating Wind M.J. Harrold1, P.R. Thies1, D. Newsam2, C. Bittencourt Ferreira3, L. Johanning1 1University of Exeter, College of Engineering, Mathematics and Physical Sciences, m.j.harrold@exeter.ac.uk

2Teqniqa Systems Ltd. 3DNV GL KEYWORDS: Floating offshore wind, non-linear mooring systems, prototype testing, numerical modelling, peak load reduction Existing mooring systems for floating offshore wind turbines (FOWT) are largely based on designs from the oil and gas industry. While these can provide the required safety margins for the FOWT application, at present there is a degree of conservatism in the design of the mooring system, resulting in additional cost. Reports from industry suggest that the mooring system can account for in excess of 10% of the overall FOWT CapEx [1], highlighting that this is a key area in which cost reduction needs to be achieved in order to improve the cost-competitiveness of FOWT. This research project is supporting the development of a hydraulic-based mooring component, referred to as the Intelligent Mooring System (IMS). The IMS has a functionality akin to that of a shock absorber, and is designed to be placed in FOWT mooring systems to reduce both fatigue and peak line loading. This would enable the usage of lower strength, and hence lower cost, materials in FOWT mooring lines, while further cost reduction could be realised through the knock-on effects of reduced loading on the anchors and platform. The IMS was built at prototype scale and tested at the University of Exeter’s Dynamic Marine Component Test Facility (DMaC), a test rig that can replicate the motions and forces that mooring lines are subject to. The device was tested in operational and extreme sea states representative of those experienced by FOWT, after firstly deriving these conditions through numerical simulations of the IMS on the OC4 semi-submersible platform [2] using the FAST-OrcaFlex interface [3]. The results suggest that inclusion of the IMS can reduce the peak mooring loads by 10%. These test results are being used to inform the design of the commercial product, which is anticipated to have a greater load reduction performance. (102-226-1-SM) GLOBAL WAVE RESOURCE CLASSIFICATION USING A CLUSTERING APPROACH I. Fairley1, M. Lewis2, I. Masters1, D.E. Reeve1 1Swansea University, College of Engineering, i.a.fairley@swansea.ac.uk; i.masters@swansea.ac.uk; d.e.reeve@swansea.ac.uk 2Bangor University, School of Ocean Sciences, m.j.lewis@bangor.ac.uk KEYWORDS: Wave Energy, Resources, Global, Classification, Clustering Classification of global wave resources is important for two main reasons: to assist with global roll-out of existing wave energy converter (WEC) technology and to identify alternative resource characteristics to inform future design. Most wave energy converter research and development effort has focused on designs for sea-states characteristic of European conditions [1]. It is postulated that other areas which have different resource characteristics may be equally rich in deployment opportunities; for example, areas with low mean power but fewer extremes and resource variability. Other studies have used wave power and period bandings to develop a classification scheme for US waters [2,3], however this bases classification on existing technological considerations. Here, an alternative approach is taken whereby wave resource characteristics are used to define classification groupings a priori using the k-means clustering algorithm [4]. The motivation for this approach is to ensure classification is technology agnostic. A coastal subset of the ECMWF ERA5 global reanalysis wave model dataset was used [5], considering 12 years from 2000 – 2011. Parameters that relate to four different factors that effect device performance are considered. The four factors were: basic wave parameters and their variability (subset W); extreme conditions (subset X), consisting of the 50 year extreme wave height and a risk factor [2]; spectral properties based on Goda’s peakedness parameter [6] (subset S); directional properties (subset D). Clustering into 6 classification groups was then undertaken with sets of normalized parameters made up from different combinations of the sub-sets: W; WX; WS; WD; WXS; WXD; WSD; WXSD. Clustering results showed similarities for all sets of parameters; but choice of set affected finer details in both geographical and parameter space. Geographical cluster distribution was linked to distance and orientation to typical storm tracks. The presentation will further describe the results and the potential uses of the classifications. (103-228-1-SM) WEAKLY NONLINEAR THEORY FOR AN ARRAY OF CURVED OSCILLATING WAVE

SURGE CONVERTERS S. Michele1, E. Renzi1 1Loughborough University, Department of Mathematical Sciences, s.michele@lboro.ac.uk KEYWORDS: Wave Energy, Fluid-Structure Interaction, Wave Mechanics We present a weakly nonlinear theory for an array of Oscillating Wave Surge Converters (OWSCs) in a semi-infinite long channel [1]. The gate model is similar to that shown in [2] except for a weak horizontal deviation of the gate wetted surface about the vertical plane. The length scales of the free surface elevation, the gate vertical displacement and the horizontal oscillations are assumed small if compared to the wavelength. Hence, the boundary conditions on the gate and on the free surface can be conveniently Taylor-expanded respectively about the vertical plane and the horizontal undisturbed free surface level. Perturbation-harmonic expansion of the unknowns up to the third order allows us to decompose the nonlinear governing equations in a sequence of linearised boundary-value problems of order n and harmonic m [3]. The gate shape effects resonate the first harmonic at the second order, so that three timing with two slow time scales is necessary. We show the occurrence of new terms in the Ginzburg-Landau evolution equation, which are not present in the case of flat gates. First, we consider the subharmonic excitation of a single mode. We obtain that subharmonic resonance is associated with increased efficiency of wave power extraction, though the effects of curvature are not always beneficial. Finally, we analyse the occurrence of synchronous nonlinear resonance by monochromatic incident waves with constant small amplitude and frequency equal to the eigenfrequency of the array. We show that this mechanism is less powerful than the subharmonic one, yet it is substantial for design purposes in real sea states when a broad spectra of frequencies are present so that both mechanisms can concur to the total oscillations. (104-230-1-SM) Risk-return site characterisation for offshore wind energy F.Khalid1, Dr. P.R.Thies2, Prof. L.Johanning3 1,2,3University of Exeter, Renewable Energy department, f.khalid2@exeter.ac.uk KEYWORDS: Offshore wind energy, Site characterisation, Structural reliability, Performance indicator, Geospatial mapping Site characterisation in offshore wind energy (OWE) is not only vital to determine the resource, but also to gauge possible influences on structural reliability from stochastic wind and wave loads [1]. The assessment and improvement of the intrinsic structural reliability of offshore wind turbines is significant to reduce uncertainties and improve the cost effectiveness of farms installed at different offshore locations [2]. This paper presents a robust methodology to visualise expected system performance based on the contribution of metocean parameters for devices deployed at sites with varying loading conditions. Spatial metocean data from the UKCS and adjoining areas is translated into spatial reliability assessment through a two – step process. First, an aero-hydro-servo-elasto-dynamic tool is used to generate structural response for the range of environmental conditions at each site. This structural response is processed by a damage life estimation tool to calculate lifetime accumulated damage indicating the fatigue life of the structure. The resulting spatial distribution of risk and return parameters indicates that due to the reduced loading at locations with lower resource potential, the structure accumulates lower damage over its lifetime. On the contrary, deployments at more dynamic sites provide improved energy generation at the expense of higher structural damage. This research argues for location –intelligent decisions for farm siting and informs lifetime extension

decisions [3] as more installations reach their design lifetimes [4].

105-232-1-SM Time domain simulation of the WaveSub device under multi-directional waves E. Faraggiana1, I. Masters1, J. Chapman2 1Swansea University, College of Engineering, Marine Energy Research Group, 951180@swansea.ac.uk 2Marine Power systems Ltd., Swansea SA1 8AS, contact@marinepowersystems.co.uk KEYWORDS: Wave directional spreading, wave energy, Wave Energy Converters, wave potential theory, numerical modelling

Simulation of multi-directional waves provide a more realistic representation of the sea state compared to uni-directional waves. They can be described by a Gaussian directional distribution [1]. The wave directional distribution is assumed to be independent of frequency and is sufficiently accurate to model the temporal wave directional characteristic. The numerical simulation of Wave Energy Converters (WECs) under multi-directional waves is a current research topic. Here we show the application and the methodology of the numerical modelling of the WaveSub device [2] under multi-directional waves. The hydrodynamic coefficients for various frequencies and directions has been found using Nemoh [3], a linear potential flow theory solver. The time domain simulation is carried out by using WEC-Sim [4] that enables modelling of the dynamic system including the Power Take-Off (PTO) and the mooring. The hydrodynamic forces computed from Nemoh are used in WEC-Sim. The influence of the wave directional distribution on the excitation force has been achieved by modification of the WEC-Sim source code; this modification has been adopted in the official version of the code. Our results extend the simulation of WECs to multi-directional waves showing the influence of the directional distribution on the WEC performance. The results of the time domain simulation could be used for future benchmarking purposes with tank testing and with CFD results. Furthermore, the efficient computational time makes this method very interesting for WECs numerical modelling.

(106-234-1-SM) Using WEC-Sim to Model Focused Wave Interaction with Floating Bodies J. Hughes, A. Williams, I. Masters Swansea University, College of Engineering, 708774@swansea.ac.uk KEYWORDS: focused wave, WEC-Sim, COAST laboratory Capturing the highly unsteady and nonlinear features of extreme wave interactions with floating bodies is a difficult task and one that can require large amounts of computing power due to the complexity of such events. Le Mehauté [1] describes the validity of different wave theories as a factor of water depth and wave steepness and shows that generally more complex models are required as wave steepness increases. Linear wave theory is often favoured in offshore industries due to its efficiency, though its drawbacks are well known due to some of the assumptions it uses, especially when it comes to modelling extreme events [2]. Clearly, there must a trade off between computational and numerical efficiency. WEC-Sim [3] is a mid-fidelity open-source code developed by Sandia Labs and NREL which uses a linear potential flow theory based method to model wave energy converter dynamics in the time domain. Frequency domain hydrodynamic coefficients are generated in open source boundary element method code, NEMOH, which are subsequently used in WEC-Sim. In this study WEC-Sim has been used to model an experiment carried out by Ransley et al. [4] in which a floating, hemispherical bottomed buoy was subject to a focused wave based on the 100 year extreme event at the test site in Falmouth, UK. The subsequent buoy motions in heave, surge and pitch are compared along with the mooring load, which is provided by a linearly elastic vertical mooring line. Fig. 1 compares the buoy motions predicted in WEC-Sim against the experimental results and CFD results from Ransley et al. [4]. Fig. 1 shows the heave motions of the buoy are predicted well, whereas surge motions are underpredicted. This is due to the underprediction of restoring forces as nonlinear buoyancy and hydrodynamic forces are neglected. (107-236-1-SM) Liquid Air Energy Storage system integrated with thermoelectric power generator as an efficient way for the storage, transport and recovery of offshore wind power Tongtong Zhang1, Xiaohui She1, Yulong Ding1 1University of Birmingham, School of Chemical Engineering, txz772@student.bham.ac.uk KEYWORDS: Liquid air energy storage, Cryogenic Energy, Offshore wind power, Thermoelectric Power Generation, Levelized cost of energy Connecting the offshore wind power with the public power grid is challenging because of its instability, intermittent and unpredictability, and the high cost of transmission cables [1]. Liquid Air Energy Storage (LAES) provides a novel way to utilize the offshore wind power: convert wind power to cryogenic energy with liquid air as the storage medium, transport the liquid air tank to a distributed power system, and finally convert the mechanical (pressure) component of the cryogenic energy to electricity. Thus, in this case, the charging and discharging

process are separated, indicating that the thermal component of the cryogenic energy cannot be recovered from discharging process and reutilized in charging process like the stand-alone LAES system. Thermoelectric power generation (TEG) technology can utilize the temperature gradient to generate electricity through the Seebeck effect. Because of no maintenance requirement and integration available [2], TEG modules could be integrated with the liquid air evaporator to generate extra electricity with the thermal component of the cryogenic energy. Thus, the thermodynamic model of the TEG evaporator was built, and both the thermodynamic and the economic performances were investigated with the liquid nitrogen (LN2) as the cold source and 60℃ thermal oil as the hot source. When only latent heat part of the cryogenic energy is used, the thermal efficiency and power generation per unit LN2 of the TEG evaporator are about 8.5% and 16 kJ/kg, respectively. When more and more sensible heat part of the cryogenic energy is utilized, the efficiency decreases while the power generation increases first and then decreases. Although the efficiency is not that attractive, the economic analysis shows that in terms of the capital cost and the levelized cost of energy (LCOE), TEG performs much more competitive than the Rankine Cycle, indicating TEG is more profitable in the small-scale distributed power system. (108-238-1-SM) Use of HF radar for replicating wave conditions for testing of wave energy converters with different regrouping methods D. M. Wang1, D. Conley1, M. Hann1, K. M. Colins1 , D. Greaves1 1Department of Marine Science and Engineering University of Plymouth, Drake Circus, Plymouth,PL4 8AA, UK daming.wang@plymouth.ac.uk KEYWORDS: HF radar, K-means clustering method, wave spectrum, WEC Wave tank testing is a useful tool to assess the performance of Wave Energy Converters (WEC) at different technology readiness levels (TRL). At early TRL the use of systematically varying wave conditions is acceptable, however at later stages there is a need to use testing conditions representative of potential prototype deployment sites. Environmental data at these deployment sties can be collected by various instruments, such as buoys, ADCP, radars etc. The most commonly used method to re-create the measured environmental testing conditions in a wave tank is to use a parmetric wave spectrum such as JONSWAP or Pierson-Moskowitz spectrum with the measured significant wave height and peak period. Although a useful tool, these parametric spectra represent a simplification which omits much of the site specific spectral information even if by introducing a pramcetric directional spreading function to represent the directional speading. Such could have the potential to significantly impact WEC performance. In most wave tanks it is possible to reproduce directly a measured spectrum. However this raises questions about which measured cases to reproduce. The use of the K-means clustering algothrim provides the opportunity to select sea states for wave tank testing that are more representative of a potential deployment site. It is necessary to develop a methodology to systematically select a set of representative experimental test cases from the wave datasets obtained from HF radar. Previous research has demonstrated the use of the K-means clustering algothrim to obtain representative wave cases from measured wave spectra [1]. Here the expansion of this method is demonstrated and an improved approach proposed. HF radar data obtained at Wave Hub, a wave energy test site in Cornwall, UK, and buoy data obtained close to Long Island, USA are used to demonstrate the approach. The new approach can re-balance the importance of different parameters participating in the regrouping and can provide more representative sea states. (110-240-1-SM)Modification of Concrete Surfaces to Reduce Colonisation by Marine Invasive Species E. Mills1, T.Dyer2, R. Jones3, J. Loxton4 1University of Dundee, School of Science and Engineering, e.mills@dundee.ac.uk 2University of Dundee, School of Science and Engineering, t.d.dyer@dundee.ac.uk 3University of Dundee, School of Science and Engineering, m.r.jones@dundee.ac.uk 4University of Edinburgh, School of Geosciences, jennifer.loxton@ed.ac.uk

KEYWORDS: Biofouling, Invasive Species, Concrete, Material Properties, Colonisation Study Marine renewable energy (MRE) is one of many industries that introduce concrete surfaces into the

oceans through the deployment of MRE devices and related infrastructure, such as harbours and

concrete mattresses. Despite this, limited biofouling research has been conducted on concrete

surfaces. This biofouling community, may include both native and non-native species, with many

studies seemingly showing man-made materials encouraging the settlement on non-native species

[1]. Invasive species spread is the second biggest threat to biodiversity globally and costs the UK £1.7

billion annually [2]. To our knowledge no study has attempted to design a material specifically to

reduce invasive species colonisation. Based on promising ecological observations found within the

current literature, six concrete surfaces, four of which are novel, were created. All six concrete

surfaces meet the requirements of engineering standards with low cost, non-toxic methodologies to

increase the possibility of implementation into industry. Frames were designed and trialled to deploy

concrete panels into the field to overcome the challenges of deploying a heavy material into the

marine environment in Scotland. A 12-month field study is currently underway with 174 panels

deployed over three sites of the East Coast of Scotland. Unsuccessful and successful frame designs will

be discussed, with the successful frame withstanding deployment for 5 months as of May 2019.

Photographs of preliminary panels placed in the water for three months will be discussed. This study

provides an example of interdisciplinary collaboration, which allows for a study where both disciplines

to address the problem efficaciously. The results of which, will hopefully provide the opportunity for

MRE to produce ecologically-tailored concrete infrastructure to promote more benign biofouling

communities.

(112-242-1-SM) An applied approach to investigating cetacean collision risk from tidal turbines Veneruso1, Bond1, Cordes2, Goward-Brown1, Hastie3, LeVay1, Slingsby2, Waggitt2 1Bangor University, Centre for Applied Marine Sciences, g.veneruso@bangor.ac.uk 2Bangor University, School of Ocean Sciences 3University of St Andrews, Sea Mammal Research Unit KEYWORDS: Tidal energy, collision risk, ecology, environmental impact, marine mammals Collision risk of marine mammals with tidal-stream technology is a significant concern to regulators due to conservation legislation and ethics. The most common approach to estimate risk is via collision risk models (CRMs) which require accurate input parameters that influence the probability of a fatal collision; the encounter and strike probabilities. To date, there are rarely data available to provide accurate model parameters meaning that uncertainty is high. The SEACAMS2 project was developed to bridge the gap between academia, industry and regulators by conducting research focussed on supporting MRE industry progression in Wales. This presentation discusses ongoing R&D projects relating to cetaceans and collision risk from tidal turbines, informing CRM encounter and strike probabilities. The harbour porpoise (Phocoena phocoena) is a cetacean known to commonly occupy tidally energetic habitats. The potential co-occurrence has led to concerns about impacts on porpoises. This pre-installation study aims to investigate harbour porpoise behaviour in tidal currents in order to assess the likelihood of animals encountering turbines. Moored acoustic recorders and 3D hydrodynamic models were used to investigate porpoise associations with local oceanography at a tidal-stream demonstration zone off Anglesey, Wales. Data relating to harbour porpoise surface behaviour at tidal features was also collected using a novel video tracking method. Preliminary results suggest that encounter rates are high, and that porpoise show fine-scale associations with local hydrodynamic features. The response of cetaceans to operational turbines is thought to be the most significant parameter influencing collision risk. A project has been developed to track cetacean movement around a commercial-scale operational power kite due to begin summer 2019. A passive acoustic array will be used to study near and mid-field response to the operating device by 3D localization of echolocating individuals and a single channel hydrophone array surrounding the development.

(115-245-1-SM) Literature Survey of Flexible Membranes for Wave Energy Converters I. Collins1, M. Hossain1, I. Masters1 1University, Department, 793350@swansea.ac.uk KEYWORDS: Wave Energy, Survivability, Reliability, Numerical Modelling, Membrane Structures Wave energy has struggled to be competitive with other renewable energy technologies, partly due to reliability concerns. System reliability is correlated to the overall complexity of the design which is a crucial area to address for a viable device design. A new trend in the wave energy literature is to utilize a membrane structure for the primary mover and power take-off as well as other sub-components, removing the need for complex mechanical systems. This literature review aims to provide an extensive overview of the implementation of membranes in wave energy converters (WECs). From the developments, a classification is devised for primary moving membrane WECs. Further discussions on the material selection and modelling approaches are presented, along with the reliability predictions which these devices aim to improve. There are as many as 20 devices [1] utilizing a membrane structure as part of their design and three new device forms have emerged: membrane cell, bulge wave and membrane carpet. Some of the notable developments from Bombora [2], Anaconda [3] and SBM S3 [4] are nearing sea trials; the critical stage for demonstrating the competiveness a device. The material choice has typically favoured elastomeric/ fabric composites due to their low modulus of elasticity and proven durability in other sectors such as the tyre industry. The advent of dielectric elastomer generators (DEGs) has allowed for a simpiler PTO which in some instances has merged with primary mover allowing for no moving machinery whatsoever [4]. Through the device development stages, numerical modelling provides an indication of the expected performance without the costs of building prototype devices. The novelty of these devices has required bespoke numerical modelling approaches, although more general approaches are now being proposed [1]. The membrane structure is expected to be the critical subsystem for overall system reliability. Currently, there is limited research in the use of elastomeric membranes under the expected environmental and loading conditions, an area which requires further research. (116-246-1-SM) Effects on hydrodynamics and ecological costs of climate change and tidal stream energy extraction in a shelf sea M. De Dominicis1, J. Wolf1, D. Sadykova 2,3, B. Scott3, A. Sadykov 2,3, R. O’Hara Murray 4 1National Oceanography Centre, Liverpool, UK, micdom@noc.ac.uk 2Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK 3School of Biological Sciences, Queen's University Belfast, Belfast, UK 4Marine Scotland Science, Aberdeen, UK KEYWORDS: tidal stream energy extraction, climate change, hydrodynamic modelling, NW European continental shelf, environmental impact Ocean energy technologies can soon occupy the marine space, in order to lower CO2 emissions and mitigate climate change. The aim of this work is to analyse the potential impacts of tidal energy extraction on the marine environment, since they should be considered when planning future tidal energy exploitation. In this work, we wanted to put them in the broader context of the possibly greater and global ecological threat of climate change. Here, we present how very large (hypothetical) tidal stream arrays and a ''business as usual'' future climate scenario can change the hydrodynamics of a seasonally stratified shelf sea, and consequently modify ecosystem habitats and animals’ behaviour. The Scottish Shelf Model, an unstructured grid three-dimensional ocean model, has been used to reproduce the present and the future state of the NW European continental shelf. Four scenarios have been modelled: present conditions and projected future climate in 2050, each with and without very large scale tidal stream arrays in Scottish Waters (UK). This allows us to evaluate the potential effect of climate change on the hydrodynamics and compare it with the future state of the seas modified by large scale energy extraction. As demonstrated in this work, climate change and tidal energy extraction both act in the same direction, in terms of increasing stratification due to warming and reduced mixing, however, the effect of climate change is ten times larger. Whilst these changes might be detrimental to the marine environment, they can also be beneficial by mitigating the effect of sea level rise in some locations. Finally, the ecological costs and benefits of these contrasting pressures on

our marine species, are evaluated using statistical models, that simultaneously explore the distributions of mobile predator and prey species and calculate the degree of overlap in these species now and in future projections. (117-249-1-SM) EXPERIMENTAL MODELLING OF A PARACHUTE-TYPE TIDAL ENERGY CONVERTER G. Rinaldi1, B. Carne2, L. Johanning1 1University of Exeter, Renewable Energy, g.rinaldi@exeter.ac.uk, l.johanning@exeter.ac.uk 2Riggers UK, info@riggers-uk.com KEYWORDS: Tidal device, experimental modelling, flume experiment Riggers UK is a Cornish service provider founded in 1970, providing diagnosis, advice and assistance on all aspects of yacht rigging, masts and commercial rigging. As a side-line activity, Riggers UK has started to develop the concept of an innovative device, shown in Figure 1, able to extract energy from water streams. The device consists of a series of semi spherical membranes (“chutes”) connected by means of a rope passing through their centre. The rope, pulled by the drag due to the action of water flow on the chutes, is then allowed to turn around a couple of rotors. These, in turn, are connected to a power take-off system (e.g. a permanent magnet generator) which converts the rotation of the rotors into electricity. Within the European funded programme Marine-i, the University of Exeter undertook a series of experimental tests, according to the ITTC guidelines [1], of a scaled and simplified versions of the device in the flume available at Penryn campus. These tests were made in order to verify the working principle of the prototype, compare the outcomes with previous numerical estimation and obtain indications for the optimization of the device. Different configurations in terms of chute size, distance and angle were conducted in order to maximize the drag of the device. The main results and their significance, especially in terms of future development of the device, will be presented. (118-251-1-SM) STRUCTURE DESIGN AND ASSESSMENT OF A FLOATING FOUNDATION FOR OFFSHORE WIND TURBINES Q. Ye1, S. Cheng1, B. Kim1, K. M. Collins1, G. Iglesias1,2 1School of Engineering, University of Plymouth, UK, qi.ye@plymouth.ac.uk 2MaREI, Environmental Research Institute & School of Engineering, University College Cork, Cork, Ireland KEYWORDS: Floating Foundation, Structural Design, Shell Structure, Buckling Resistance As energy consumption increases globally and environmental issues threaten the quality of life, new sustainable ways of energy generation are actively being researched and promoted. Although offshore wind energy has demonstrated great potential, it needs to cut down cost significantly in order to be competitive with conventional energy types. Given the fact that the substructure and installation count for over 30% of the total investment costs of offshore floating wind turbines [1], it is essential to optimize the design and fabrication of the support structures in order to lower the cost. The aim of this work is to assess the structural design of a floating foundation for offshore wind turbines based on DNVGL [2] and Eurocode [3] in terms of economy and reliability. The wind loads are calculated using empirical equations, and the wave loads are obtained and verified using various methods including hand calculation, AQWA and flow 3D. It is found that the shell thickness could be reduced significantly by introducing the stiffeners (stringer or ring), which can decrease the weight of the hull and lower the cost. While DNVGL and Eurocode yield similar design solutions if using plane shell structures, Eurocode significantly underestimates the buckling resistance of stiffened cylindrical shells.

(119-253-1-SM) Active control of the WaveSub WEC for increased power capture A.J. Hillis1, A.R.Plummer1, J. Chapman2 1University of Bath, Department of Mechanical Engineering, a.j.hillis@bath.ac.uk 2Marine Power Systems Ltd, contact@marinepowersystems.co.uk KEYWORDS: Active control, submerged Wave Energy Converter, power take off WaveSub is a Wave Energy Converter (WEC) under development by Marine Power Systems Ltd (MPS). It is a submerged point absorber with a unique multi-tether configuration and variable geometry

which can be tuned to the prevailing sea state. A float moves with the waves and reacts against a moored base. The tethers pull on rotational drums which are attached to a PTO. An illustration of a full scale multi-float concept is shown in Figure 1. This study uses a single section of this device, comprising a single float with four taut tethers connected to individual drums and rotational power take offs (PTO). The block diagram of the complete system is shown in Figure 2. The full scale WEC has been modelled in the WEC-Sim environment using a fixed passive damping system for the PTOs, which was optimally tuned for individual sea-states to provide a performance benchmark. An active control system utilising the simple and effective method with a Linear Quadratic Regulator velocity tracking loop has been developed with the aim of maximising power capture across a range of seas whilst operating within physical system constraints [1]. A wide range of operational sea states was applied and the performance of the active and passive systems compared. Figure 3 shows the percentage increase in mean power generation achieved by the actively controlled system over 700s of simulation with the full nonlinear WEC-Sim model. The results are shown for irregular PM spectra with significant wave heights (Hs) of 0.5-6.5m and energy periods (Te) of 6-16s. Power gains of 13% to 86% are observed across a wide range of irregular sea states compared to the passive system. This approach shows promise to provide a substantial increase in power capture for a minimal additional device cost and therefore a significant improvement in cost of energy would likely result.

(120-255-1-SM) EXTREME LOAD ANALYSIS OF POINT ABSORBING WAVE ENERGY CONVERTERS E. Katsidoniotaki1, E. Ransley2, M. Göteman1 1Uppsala University, Dep. of Engineering Sciences, Box 534, 751 21 Uppsala Sweden eirini.katsidoniotaki@angstrom.uu.se, malin.goteman@angstrom.uu.se 2University of Plymouth, School of Engineering, Marine Building, Drake Circus, Plymouth, PLA 8AA, UK edward.ransley@plymouth.ac.uk KEYWORDS: Wave Energy, Survivability, Numerical Modelling, Computational Fluid Dynamics, Extreme Conditions One of the main challenges in harnessing marine renewable energy resources is the difficulty in finding reliable solutions for the harsh environmental and extreme weather conditions offshore. Extreme loads play a key role at the design stage of wave energy converters, significantly affecting their cost. The main objective, of the present work, is to develop a reliable numerical model for offshore renewable energy applications and use it to study extreme loads and survivability. The main focus is, initially, on the wave energy convertor (WEC) developed at Uppsala University [1], but other floating structures, such as similar WECs or floating wind turbine foundations, will be considered in the future. The numerical model simulations are conducted using high fidelity CFD analysis, specifically the open- source software OpenFOAM. The main focus is to investigate the nonlinear wave and floating object interaction, during extreme and survival sea states, and predict the exreme response of the body using an ‘equivalent design wave’ approach. The equivalent wave profile represents the wave which causes the maximum design load and thus the maxima device response [2]. In the future, the extreme sea states used would have been identified from the ‘n-year extreme wave contour’ from locations in the Baltic and North Sea, provided by Uppsala University Geocentrum Department. At present, the Uppsala University WEC approximated as a single-body, point-absorber device. The structure is exposed to 5 regular waves profiles equivalent to 5 sea states identified from the 100-year extreme wave contour at the Humboldt Bay site California [3]. The force due to the connection line, translator acceleration and Power Take Off (PTO) damping is applied via an expression-based motion restraint [1]. Mesh independence is demonstrated and both the mooring load and body displacement reported. In terms of a long term approach under the framework of the present PhD project, effort is made to correlate real sea state data from the examined locations with the occurance of nonlinear hydrodynamic phenomena and answer some common practical questions, such as: how resilient is the system; would be a better practice to force the system into survival mode, during the extreme conditions, and; how is the cost of energy affected by the extreme weather conditions present? (121-257-1-SM) VALIDATING A NUMERICAL TOOL FOR EVALUATING FLOATING TIDAL SYSTEMS S. Brown1, E. Ransley1, N. Xie1, E. Guerrini2, D. Greaves1 1University of Plymouth, School of Engineering, scott.brown@plymouth.ac.uk

2Modular Tide Generators Ltd. KEYWORDS: Tidal Turbines, Moorings, Marine Renewable Energy, OpenFOAM, COAST Floating systems provide an opportunity to expand the available tidal stream energy resource and reduce the levelised cost of energy (LCOE) by increasing the number of viable deployment sites; simplifying the installation, maintenance and decommissioning, and; by accessing greater flow speeds near the free surface. However, the proximity of the free surface raises concerns over both the power delivery and the survivability of these systems, due to the presence of waves and the associated excitation of the floating structures. Without an accurate prediction of the power output and greater confidence in the resilience of these systems, the risk to investors is too high to gain significant support for the industry. This has led to the development of a coupled and fully-nonlinear numerical model within the open-source CFD environment, OpenFOAM, capable of evaluating the performance and behaviour of full floating tidal systems [1]. The model solves the incompressible Reynolds-Averaged Navier-Stokes equations for a two-phase fluid, tracks the motion of the system in six degrees of freedom, and uses expression-based boundary conditions for wave generation [2]; a two-way coupled, actuator method to represent the turbine [1]; and a static catenary formulation for the moorings [3,4]. The model has previously been shown to agree with industry standard codes in relatively benign conditions, but has demonstrated additional complexities are present in more realistic conditions and these are not captured by simpler approaches. This work considers validation of the numerical model through simulation of the Modular Tide Generator’s (MTG) floating tidal platform concept, which consists of a catamaran style hull, catenary mooring system and a submerged horizontal axis tidal turbine. The results are compared with a series of 1/12 scale physical experiments, conducted in the COAST laboratory’s Ocean Basin at the University of Plymouth. The behaviour of the full system has been explored in a range of wave, current, and wave-current conditions, both with and without the turbine. In each case, the accuracy of the numerical model predictions has been assessed against multiple criteria, including the motion of the barge, tension in each of the mooring lines and the thrust on the turbine. The results imply that the model successfully captures some of the key coupled properties of the problem, including relative increases in turbine load due to the motion-thrust coupling. However, further work is required to improve turbine load calculations in reversing flows, and to introduce dynamic catenary mooring line functionality. (122-259-3-SM) Parametric investigation of an integrated WEC-type breakwater system H. Ding1, J. Zang1, C. Blenkinsopp1, Q. Chen1 1University of Bath, Department of Architecture & Civil Engineering, hd484@bath.ac.uk KEYWORDS: Wave Energy Converter (WEC), Floating Breakwater, OpenFOAM®, Optimisation, Functional Performance Wave energy converters (WECs) are built to extract wave energy. Nevertheless, this kind of devices is still expensive for commercial utilisations. There is one possible solution to cut down the cost of WECs by sharing the construction-cost with breakwaters. Thus, the integrated WEC-type breakwater (WEC-B) system is proposed. However, the WEC-B system is still in an immature phase and under development. This research aims to improve the efficiency of the WEC-B system by optimising an existing concept, which is the pile-restrained WEC-type dual-floating breakwater (pile-restrained WEC-B) system proposed in [1] [2] (device setup in numerical wave tank shown in Figure 1). Four parameters including PTO damping coefficient, gap width between two floating breakwaters, structure width and draft are discussed about how they influence the performance of the pile-restrained WEC-B system in the optimisation. This parametric investigation is conducted by the Computational Fluid Dynamics (CFD) tool OpenFOAM®. The solver, interDyMFoam within OpenFOAM® package, is employed to simulate fluid-floating structure interactions. Navier-Stokes equations are utilised to describe the motion of fluid continuum, and the volume of fluid (VOF) method is utilised to track the shape and position of water free surface. The water waves are generated by toolbox waves2foam [3]. The numerical results in this research present influences of four aforementioned parameters on two factors including transmission coefficient and capture width ratio, which can be used to evaluate the performance of wave attenuation and efficiency of energy extraction, respectively. These results prove that the functional performance of the pile-restrained

WEC-B system can be improved obviously with an appropriate layout of devices. In addition, the phenomena including bragg resonance and gap resonance appear during the numerical simulations, which can be discussed in the further research by considering influences on the survivability of WEC-B systems. (124-260-1-SM) CFD surface effects on flow conditions and tidal stream turbine performance C. Lloyd1 1Cardiff University, Engineering Department, Lloydc11@cardiff.ac.uk KEYWORDS: ANSYS CFX, Computational Fluid Dynamics, Free Surface, Marine Energy, Tidal Stream Turbine. There is a rising demand for energy around the world and yet a finite supply of fossil fuels. This, amongst other environmental concerns, has provoked increased research and development into identifying sources of sustainable energy. Tidal energy is an abundant resource in the UK and has an estimated potential of 18 TWh / year [1]. With over half the world’s tidal energy developers being based in the EU [2], the industry is beginning to grow and have a positive impact. The diurnal tidal flow is a predictable and regular form of renewable energy, where Tidal Stream Turbines (TST’s) can extract energy from these flows to generate electrical energy. The ocean is a harsh, very complex and diverse environment, where challenging conditions arise from interaction between tidal currents, surface waves and turbulence from the bathymetry of the seabed. These conditions can make the operation and maintenance of full-scale devices very difficult. Experimental testing of model scale TST’s has therefore been carried out in tow tanks and recirculating flume facilities. These facilities can be used to establish a wide range of flow conditions and investigate the loadings and performance on a turbine. Computational Fluid Dynamics (CFD), in more recent years, has been used to create numerical models as a cheaper alternative to experimental testing. These numerical models can replicate experimental conditions and investigate TST operation in various subsea flow conditions, as found in [3]–[5]. Although all flume tanks possess a free surface experimentally, most CFD modelling is done without and uses adjusted boundary conditions instead. This is because it is important to have an increased mesh resolution at the fluid interface and in doing this, increases the overall size of the mesh and therefore the run time of the model. This paper aims to investigate the differences of the surface boundary conditions in a model with and without a free surface. The simulations will model one TST in a uniform flow condition with comparable meshes in order to isolate the variation of the surface effects and directly compare them. Experimental data from the French Research Institute for Exploitation of the Sea (IFREMER) is then used to make comparisons with, and validate the accuracy, of each model. (125-262-1-SM) Linear non-causal optimal control of multi-float multi-mode wave energy converter M4 Zhijing. Liao1, Peter. Stansby2, Guang. Li1 1Queen Mary University of London, School of Engineering and Materials Science, z.liao@qmul.ac.uk g.li@qmul.ac.uk 2University of Manchester, School of Mechanical, Aerospace and Civil Engineering p.k.stansby@manchester.ac.uk KEYWORDS: Wave energy converter, Optimal control, Non-causal control, Wave prediction In this work, we demonstrate the application of an efficient linear non-causal optimal controller

(LNOC) [1] to maximize the energy conversion of the attenuator type multi-float multi-mode wave

energy converter (MWEC) M4. [2] While it is very challenging to design and implement controllers for

the MWECs using most of the existing advanced control methods, because of the model complexity

of MWECs and high computational demands of the controllers, we aim to demonstrate that using a

reduced-order linear model, the LNOC method can be applied to the M4 WEC without introducing an

intractable computational burden while enabling significant energy conversion improvement. The key

reason for the energy conversion improvement is due to the non-causal wave prediction explicitly

incorporated into the controller. Numerical results show that with the LNOC method and a wave

prediction of 2-3 peak periods into the future, the M4 WEC has an energy conversion improvement

ranging from 40% to 100% in various sea states. The prediction horizon and prediction errors are both

investigated to quantify their influences on control performance. As a conclusion the LNOC method

shows great potentials for practical implementation on MWECs in real applications.

(127-264-1-SM) TURBULENT FLOW FEATURES AROUND A CIRCULAR MONOPILE Yi Xu1, Manousos Valyrakis1 1Water Engineering, Water Engineering Lab, University of Glasgow, Glasgow G12 8LT, UK, 2421380X@student.gla.ac.uk KEYWORDS: experimental modeling, flow turbulence, monopile, scour Local scour around monopiles can be significant leading to failure of the support structure for energy infrastructure. Maximum local scour depth monitoring and prediction is a challenge that needs be addressed for resilient design and installation of near and off---shore infrastructure, such as wind farms. This research study focuses on presenting preliminary results from an experimental campaign to acquire high---resolution flow turbulence diagnostics and scour depth, around a cylindrical structure (a physical scale model of a monopole), under clear water scour conditions, using acoustic Doppler velocimetry (ADV), assuming a strong current (only unidirectional flow). A range of turbulent flow features (such as three---dimensional mean flow velocity components, size of primary horseshoe vortex, Reynolds shear stresses, turbulence intensities and turbulence kinetic energy), are estimated for different monopole diameters under equilibrium scour conditions. The primary horseshoe vortex was found to be the major cause for scour processes. Horseshoe vortex size increases with monopile diameter resulting at a maximum equilibrium scour depth, which also scales with the shed vortices [1]. (128-266-1-SM) Public engagement with energy transitions: An exploration of the challenges of engaging island communities G. Kallis1, I. Bailey1, P. Devine-Wright2, E. Bailey2 1Plymouth University, School of Geography, Earth and Environmental Sciences, gina.kallis@plymouth.ac.uk (corresponding author) 2University of Exeter, College of Life and Environmental Sciences KEYWORDS: Islands, remote communities, public engagement, energy transitions This poster examines the challenges of public engagement with island communities on marine renewable energy projects and other aspects of energy transitions. Recent years have seen growing recognition of the importance of active public engagement in counteracting difficulties in energy planning and siting decisions. Much attention has centred on defining principles and practices for ‘effective’, place-sensitive and justice-based public engagement on energy issues, but most research in this area has focused on ‘mainland’ communities. This poster complements and extends this research by utilising evidence from the engagement literature and island case studies to examine the distinctive considerations of consulting with island communities on projects to address local energy access and sustainability issues and/or generate low-carbon energy on a larger-scale. It examines how varying motivations for public engagement can influence engagement strategies, the suitability of different methods of engagement in island contexts, and the challenges of conducting public engagement in ways that ensure island communities have a fair say and receive fair treatment in energy decision-making. Alongside general considerations such as starting engagement early to increase opportunities for local views and knowledge to be discussed, and maintaining engagement throughout the planning, construction, operation and decommissioning stages of project, key issues highlighted include: (i) the need to recognise the diverse character of island communities (including different forms of attachment to the local area among permanent and part-time residents and visitors, and between economic sectors) and how this affects views towards energy projects and the practicalities (timing and intensity) of engagement; (ii) the use of trusted intermediaries to build understanding and trust; and (iii) encouraging active local input into the design of community benefits to address perceived imbalances between the impacts and benefits of developments.

(129-268-1-SM) An advanced robust wave excitation force estimation framework based on adaptive sliding mode observer Yao Zhang and Guang Li Queen Mary University of London KEYWORDS: wave energy converter, wave excitation force prediction, optimal control, sliding mode observer, adaptive control. It is well accepted that sea wave energy converter (WEC) control is a non-causal control problem which requires the incorporation of the wave forecasting information into WEC optimal controller (Zhan S, 2018) (Li G, 2014 ). Motivated by this fact, many wave prediction techniques have been developed to provide the wave forecasting information for WEC control purpose. The efficacy of these algorithms (Fusco, 2010) (Fusco F. a., 2011) have been demonstrated mainly for single-float single motion (SLSM) WECs, but their efficacy may degrade for multi-float, multi-motion (MFMM) WEC. This is because the wave excitation force prediction of a MFMM WEC heavily relies on the fidelity of the WEC dynamic model, and the control oriented model of the MFMM WEC, which may involve much more significant uncertainties compared to that of a SLSM WEC. The uncertainties are caused by the following reasons: 1. To develop computationally efficient WEC control algorithms, the nonlinear MFMM WEC model is linearlized locally, which introduces modelling mismatch (Stansby, 2015). 2. The frequency-determined hydrodynamics of a WEC can change notably with the variation of sea states. To develop a high-fidelity control oriented model for MFMM WEC coving a wide range of sea sates is very challenging and can result in a very large order model. To resolve the influence of model uncertainties on wave excitation forecasting, in this presentation, we demonstrate an advanced robust wave excitation force estimation framework based on an adaptive sliding mode observer (ASMO). By using this novel wave excitation force estimation framework, the prediction errors can be explicitly estimated to achieve guaranteed control performance for the non-causal controller requiring future excitation force. Simulation results based on a MFMM WEC M4 (Stansby, 2015) show that the proposed advanced robust wave excitation force estimation framework can achieve a small estimation error and is robust against modeling uncertainties compared with the existing wave excitation force prediction methods. (130-270-1-SM) HYDRO-ENVIRONMENTAL MODELLING OF WAKE DYNAMICS OF TURBINES AND SLUICES IN TIDAL RANGE SCHEMES C. Leech1, Dr Reza Ahmadian1 and Professor Roger Falconer1 1Cardiff University, Engineering Department, leechc@cardiff.ac.uk KEYWORDS: Tidal Range, Turbines, Sluices, Hydro-environmental impact, Physical modelling The great tidal range of the UK is, as yet, an untapped resource, estimated to be capable of providing up to 20% of the UK’s national energy demand [1]. However, besides technological issues, obstacles to the use of this technology lie in concerns over the many unknown environmental impacts that tidal range structures (TRS) could cause. This research seeks to address questions around flow structures initiated by TRSs, which impact both the technical and environmental performance of a scheme, by focusing on experimental and numerical modelling of turbine and sluice spacing in TRSs. With no tidal range lagoons yet in existence it is important to gain accurate information about their performance on which to base predictions for future projects. To this end, a physical model with idealized geometry has been built in the 5m by 5m tidal basin at the Hydro-environmental Research Centre (HRC) of Cardiff University. Plans to vary the layout of turbines and sluices will enable the observation of hydrodynamic features under different conditions [2]. Results from these physical experiments will then be used to calibrate a numerical model in Delft3D [3] in order to extend simulations to look at flow conditions around turbines and sluices in TRSs in real cases with different configurations to determine the best design for maintaining a healthy environment. It is also hoped that modelling the hydrodynamic characteristics of such projects will help determine if other activities, such as recreation and aquaculture, are possible within a tidal range lagoon. Scrutinising the wake dynamics of tidal range turbines will also help decision makers to prove conclusively whether this is a sustainable technology i.e. whether it is able to operate under conditions that are not detrimental to the environment.

Accurate modelling of wake dynamics may also have applications in natural lagoons and be used by environmental groups to support healthy habitats. (131-272-1-SM) The initial characterisation of a tidal stream turbine on a drive train test rig on steady state conditions E.Rojo-Zazueta1, M. Allmark2, P. Prickett3, R. Grosvenor4 1Cardiff University, School of Engineering, RojoZazuetaEG@cardiff.ac.uk 2AllmarkMJ1@cardiff.ac.uk 3Prickett@cardiff.ac.uk 4Grosvenor@cardiff.ac.uk KEYWORDS: Condition-based maintenance, tidal stream turbine, generator test rig, monitoring. The long-term operational availability and reliability of marine energy tidal stream turbines (TSTs) devices have yet to be proven. There are therefore risks of higher operational costs and a major uncertainty surrounding their operation and maintenance [1]. A condition-based maintenance (CBM) strategy has the potential to increase availability and reduce maintenance costs while improving the competitiveness of TSTs when compared with other renewable energy technologies [2]. Different approaches, from computational modelling to experimental testing, have allowed researchers to explore the use of CBM approaches. However, one of the most considerable remaining challenges is to establish the capability to translate the results from experimental to full scale TSTs. This paper presents an approach to characterise turbine behaviour by the use of a simulator drive train test bed. The aim is to develop and validate CBM strategies. The test bed will be used to predict the capabilities of future turbine performance monitoring with realistic and site-specific conditions. Research undertaken by the Cardiff Marine Energy Research Group (CMERG) has developed representative TSTs simulations which will be adapted to run the drive test rig at 1/20th scale. A non-dimensional analysis will be presented to confirm the ability of the simulator test-bed to support a realistic flow resource characterisation. The response and interaction of the drive train components within a TST will then be investigated. The purpose of this paper is to demonstrate the effectiveness of the simulator in replicating different inlet velocities and torque measurement data from experimental results of an existing CMERG turbine. The flexibility that this test rig constitutes is essential in the engineering of cost-effective CBM outcomes. The test rig can also be used to determine appropriate parameters, such as tip-speed ratio and rotor angular velocity, given a low velocity profile with other realistic flow characterisation inputs. The longer-term intention of this work is to support the appropriate selection and subsequent CBM of a device able to extract the peak offered energy yield from low velocities, such as the ones found in Mexico. (133-276-1-SM) MACRO-ELEMENT MODEL OF MARINE ANCHORS FOR FLOATING OFFSHORE STRUCTURES SUBJECTED TO CYCLIC LOADS A. Peccin da Silva1, A. Diambra2 1University of Bristol, Department of Civil Engineering, a.peccindasilva@bristol.ac.uk 1University of Bristol, Department of Civil Engineering, andrea.diambra@bristol.ac.uk KEYWORDS: Anchors, Macro-Element Modelling, Cyclic Loading, Wind and Wave Energy This work presents a rigid-plastic strain-hardening macro-element model that is able to predict the behaviour of Suction Embedded Plate Anchors (SEPLAs) for floating offshore structures, mainly those applied to wave, wind and tidal energy, during keying and loading stages. A non-associated plastic potential is added to an existing model with the aim of improving the prediction of anchor trajectory for the whole displacement domain and for a large range of padeye offsets. The proposed model also includes a strain-hardening rule in order to predict the force and displacement mobilisation at the early stages of the keying process. The results obtained from the macro-element model simulations are compared to previously published LDFE analyses and centrifuge tests, showing its capability of reproducing anchor rotation, trajectory and force-displacement for a wide range of padeye offsets. Ongoing developments on the effect of cyclic loading in the response of the anchors will also be presented. This research provides a powerful tool to assist engineers and academics working on the design of floating offshore structures.

(134-278-1-SM) Unified one-fluid simulation for Floating Wave Energy Converters L. Yang1, D. Stagonas1, P. Hart1 1Division of Energy and Power, Cranfield University Liang.Yang@cranfield.ac.uk 1Division of Energy and Power, Cranfield University D.Stagonas@cranfield.ac.uk 1Division of Energy and Power, Cranfield University P.R.Hart@cranfield.ac.uk KEYWORDS: Wave Energy, Numerical Modelling, One-Fluid formulation The overall scientific goal of this research is a step change in the numerical simulation of complex Multiphysics problem, involving multibody dynamics (MBD), solid mechanics and wave hydrodynamics, which lies well beyond the scope of today's analytical capability. From the modelling standpoint, the ideas pursued in this research will represent an original research contribution in the numerical analysis of MBD and fluid mechanics coupling, with an efficient methodology to model connected structures as a continuum. In the ‘one-fluid’ formulation [1], the multiple connected rigid bodies are modelled as a different phase of non-viscous fluid, and their motions are linked by a unified equation by Lagrange Multipliers. The whole system is solved in a continuum and unified manner, and there is no explicit imposing the coupling boundary or condition or usage of MBD governing equations [2,3]. The key ingredients of this methodology are: 1) the solution of the underlying Navier-Stokes equations and 2) the consideration of distributed Lagrange multipliers to enforce rigid body constraints. From the spatial discretisation point of view, we employ a Cartesian staggered Finite Volume scheme (Marker-and-Cell (MAC) grid) and a level set methodology to describe the evolution of the various interacting phases. The results suggest that the unified ‘one-fluid’ equation can predict the dynamic response of the WECs in the numerical wave tank. (135-280-1-SM) THROUGH-LIFE COUPLING BETWEEN MOORING LOADS AND ANCHOR CAPACITY

D.J. White1, J. Tom2, R. Ragni3 & D. Rijnsdorp4 david.white@soton.ac.uk1 University of Southampton, Faculty of Engineering & Physical Sciences, joe.tom@uwa.edu.au2 University of Western Australia, Oceans Graduate School, raffaele.ragni@ngi.no3 Norwegian Geotechnical Institute, Perth, dirk.rijnsdorp@uwa.edu.au4 University of Western Australia, Oceans Graduate School, KEYWORDS: Wave Energy, Moorings, Anchors, Geotechnical Capacity, Reliability Wave energy devices and other floating renewable energy systems require a reliable mooring systems. The mooring arrangement often involves taut lines that applies a continuous load to the anchor point, with cyclic loading superimposed. The anchor must be sized to provide sufficient capacity to resist the extreme loads applied during the operating life. It is conventional for the extreme anchor load to be estimated from analyses in which the anchor connection is rigid. The anchor is then sized to provide adequate geotechnical capacity based on this single design load, sometimes allowing for the degradation of soil strength associated with the build-up of the storm in which that design load occurs. This presentation explores potential beneficial geotechnical effects that are not incorporated in the conventional design approach, via an analysis of a heaving point absorber. The non-hydrostatic wave-flow model SWASH is used to simulate the response of this taut-moored wave energy converter. The predicted forces acting on the mooring system are used to compute the build-up of excess pore pressures in the soil around the mooring anchor and the resulting changes in strength and capacity. An initial loss of strength is followed by a subsequent increase in capacity, associated with long-term cyclic loading and hardening due to consolidation. The analyses show how cyclic loading may actually benefit and reduce anchoring requirements for wave energy devices, in soft soil conditions where the sediment has a tendency to contract in response to monotonic and cyclic loading. The analyses demonstrates the value in developing coupled models of wave energy systems that incorporate geotechnical effects as well as the device and its mooring. There may be opportunities to reduce the conservatism of current design approaches while assuring adequate system reliability.

(136-282-1-SM) Experimental Testing and Numerical Study of a Turbine for Hydroelectricity Generation B. Ranabhat1, R. Ahmadian1, A. Mason-Jones, R. Falconer1, A. Kwan1 1Cardiff University, School of Engineering

RanabhatB1@cardiff.ac.uk KEYWORDS: Hydro-kinetic turbine, Experimental study, performance parameter Most of the research and development on hydro-kinetic turbines has been recently focused on tidal currents where the axial flow and lift based turbine technology has generated a momentum for the performance of such turbines [1]. However, significant sources of renewable energy including riverine and shallow waters have been overlooked due to either environmental concerns or unavailability of appropriate turbines [2]. This research is focused on experimental testing and computational modelling of a cross flow, drag type turbine for its performance. The key objectives of this study are to assess the turbine’s performance parameters, such as power coefficient (Cp) at various tip speed ratios (TSR) for different turbine configurations and their impact due to channel augmentation. Twelve different turbine configurations are considered by varying the number and type of blades. The optimum number of blades for such turbines have been established. The experimental testing of the turbine is carried out in a re-circulating flume at the hydraulic lab of Cardiff University. The generated power from the test turbine is dissipated due to heat from a mechanical disk brake where the torque and rotational speed are recorded by a LabVIEW program to assess the performance parameter. The next phase of the research will be to test the same turbines by augmenting the flow in the channel. The flume side walls will be modified by using wedges of different slopes to funnel the flow to the turbine. A CFD model will also be developed by using the commercial program ANSYS CFX to validate the experimental outcomes. The flume test results of different turbine options so far showed a lower TSR (<1) and characterise the turbine as a slow rotating device with its possible application at the ecologically sensitive rivers. (137-284-1-SM) Modelling Tidal Range Structures Using Delft3D and Telemac2D B. Guo, N. ČOŽ, R. Ahmadian and R. A. Falconer Cardiff University, Hydro-environmental research center, guob2@cardiff.ac.uk KEYWORDS: Flow pattern, Lagoon, turbine wake, Telemac2D, Delft3D Abstract: Tidal lagoon has gained further interest in recent years because of the increasing demand for renewable energy and their potential in providing other benefits, such as coastal protection. Accurate modelling of such schemes is very important to predict their operation, hydrodynamic and hydro-environmental processes, and power output of such schemes [1-2]. Implementation of the Tidal Range Structures (TRSs) in hydro-environmental models requires modification of the model which could be different due to the structure, numerical scheme and discretization method used in the model. Furthermore, a momentum source/sink which simulate the impact of water jet in the receiving waters has been considered as an important part of such models. Two widely used open-source software: Telemac2D and Delft3D have been refined to simulate the Swansea Bay tidal lagoons to study the flow pattern in the operation of Swansea bay lagoon. Both models were modified to simulate the lagoon using domain decomposition which means simulating the lagoon as an independent subdomain from the main domain. The turbines were represented using a Hill-chart and the discharge through the sluice gates and idle turbines was calculated from a standard orifice equation. The operation scheme considered for this study was two-way generation as proposed for the Swansea Bay Lagoon. The model predictions using different approaches, including water level on both sides of lagoon, the power output, and recirculation zones, were compared. Results show that Telemac2D and Delft3D despite their different numerical approach, have a similar and reasonable results in simulating the Swansea bay lagoon. There are several recirculation zones generated on both sides of lagoon when the turbines are in operation which are expected to affect the sediment transport and sediment erosion and deposition. The prediction of power output by both models for over a typical neap-spring-neap tidal cycle were similar. There are also differences between model predictions like the width and

the development flow direction of turbine wakes which are thought to be linked to mesh structure and turbulence model, but no noticeable influence in the far-field flow pattern. The comparison between Telemac2D and Delft3D predictions show that both models so far are suitable to predict the environmental impact of tidal lagoon.

(138-285-1-SM) Commercial scale tidal stream turbine development D.S Coles SIMEC Atlantis Energy, daniel.coles@simecatlantis.com KEYWORDS: MeyGen, commercial scale arrays, levelised cost of energy, array optimization, economies of scale/volume. To date (03/06/2019), the MeyGen Phase 1A array has generated over 16.5 GWh to grid, with availability exceeding 95% in recent months. Up to May 2019, the total energy generated from tidal stream energy projects exceeds 30 GWh. Whilst these achievements represent significant progress, uncertainty remains over how the industry can scale up to commercial levels, defined here as c. 100 MW arrays. This scale up is sensitive to cost of energy, since tidal stream energy is currently more expensive than technologies that have benefited from significantly longer development periods. This presentation provides SIMEC Atlantis Energy’s view of the approaches needed/being taken to overcome technical challenges that will achieve cost of energy reduction to unlock commercial scale build out. These include: 1. Resource assessment: Drone/radar surveys for cost effective flow characterization with high spatial and temporal coverage. 2. Turbine design: Validation against design codes, economies of scale to reduce LCoE, modular design approach to achieve economies of volume. 3. Array optimization: Multi-faceted optimization of turbine placement to minimize LCoE and environmental impact, full-scale site wake surveys to establish wake impingement avoidance.

APPENDIX 1

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Prifysgol Caerdydd, Caerdydd, UK