bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a passive blade-pitch mechanism to reduce the loads on a tidal turbine in high-flow conditions
Authors: Summers Thomas , Oterkus Selda , Tabor Gavin , Shek Jonathan , Wray Bevan , Dadd George 
Published: September 2023

Maintenance of tidal turbines is expensive, and relies upon suitable weather conditions and vessel availability, which can lead to costly delays. Turbine reliability can be improved by eliminating complexity in the design. The use of fixed-pitch blades, for example, can greatly reduce maintenance costs by avoiding complex active blade-pitch mechanisms which are the main source of failure in wind turbines.
Pitching rotor blades to feather in high-flow conditions is, however, the most effective means of reducing loads on the rotor. Turbines with fixed-pitch blades therefore necessarily have smaller rotor diameters compared to those with active-pitch systems, in order to keep the thrust force, flap-wise bending moment, and power output within allowable limits. In low-flow conditions, power output is proportional to the square of the rotor diameter, so turbines with small diameter rotors capture less energy over their lifetime.
This study seeks to develop a novel passive-pitch mechanism for tidal turbine blades. This mechanism must be reliable, and should act to reduce the loads on the rotor in high-flow conditions so that a larger diameter rotor can be installed, increasing power capture.
An initial design for a passive-pitch mechanism, which is actuated by the hydrodynamic forces developed by the rotor such that the blades pitch-to-feather in high-flow conditions, has been developed. The design is compatible with proven passive reversible rotor blade technology, eliminating the requirement for a maintenance sensitive yaw mechanism.
Since initial concept design, work has been undertaken to build a tool, based on NREL’s OpenFAST blade element momentum code, which models the forces acting on the rotor blades, coupled with the mechanical response of the passive blade-pitch mechanism. This tool has been used to predict the performance of the turbine for a range of operating conditions, allowing the influence of parameters such as blade geometry, rotor diameter and passive-pitch response to be analysed in terms of rotor loading and turbine performance.
Initial analysis suggests that installing blades with a passive-pitch mechanism could reduce the loads on the rotor in high-flow conditions down to just 25% of the loads that would act on an equivalent rotor with fixed-pitch blades. This would allow larger diameter rotors to be installed which could improve annual energy yield by over 40% at a typical site.
Despite these significant potential performance improvements, the challenges of developing a passive blade-pitch mechanism for tidal turbines are not well understood, as tidal developers have all so far implemented fixed or active pitch mechanisms. These challenges will be addressed throughout the remainder of this study, which will involve detailed design followed by physical tank testing.
Origami-adapted clam design for wave energy conversion
Authors: Yang Jingyi , You Zhong , Cheng Shanshan , Wang Xinu , Puzhukkil Krishnendu , Cox Malcolm , Rainey Rod , Chaplin John , Greaves Deborah 
Published: September 2023

The Clam wave energy converter (WEC) is a floating device composed of two side plates connected by a hinge that closes and opens under interaction with wave crests and troughs. A linear power take-off (PTO) may be installed between the two side plates to convert the mechanical motions to electricity, or the volume change may be used to pump air between chambers and across an air turbine PTO. The basic concept has been discussed since 1978 and featured as part of the UK Wave Energy research programme [1]. Some simplified clam models have been built since then and preliminary investigations were conducted by Phillips [2] to understand the wave-structure interactions at the COAST laboratory, University of Plymouth. However, the simplified models were not enclosed and hence seawater can be trapped in the device. To further the investigation, we will design the outer shell of the clam model that is enclosed and thus suitable for use in the (adverse) marine environment.
Since no enclosed flexible polyhedral structure can change its volume without bending or stretching of facets according to the bellows conjecture, the clam model must be strained when it is in motion. A portion of the wave energy will be consumed to deform the outer shell of the clam model and the rest can be captured by the PTO. Therefore, the design of the clam model will aim at minimising the strain on its facets while achieving the largest volumetric change of the device to maximise the power extraction by the PTO.
Inspired by origami, we will construct the enclosed clam-type offshore device by connecting rigid panels and elastic membranes with rotational hinges. We model the rigid panels to rotate about the hinges without facet deformation and allow stretching on elastic membranes. The strain on the elastic material shall be minimised for better structural integrity and minimal energy loss. Satisfying all the design requirements, the best geometric design is obtained through an optimisation process. Based on the optimised geometry, a downscaled prototype will be built using rigid plywood and rubber membranes and tested under dynamic wave-induced loads to prove that the strain incurred is negligible in response to forces.

References:
[1] Peatfield, A. M., Duckers, L. J., Lockftt, F. P., Loughridge, B. W., West, M. J., & White, P. R. S. (1984). The SEA-Clam wave energy converter. In Energy Developments: New Forms, Renewables, Conservation (pp. 137-142). Pergamon.
[2] Phillips, J. W. (2017). Mathematical and Physical Modelling of a Floating Clam-type Wave Energy Converter (Doctoral dissertation, University of Plymouth).
Impact of lateral turbine spacing on the performance of a multi-rotor tidal energy device
Authors: Smith Rachael , Townley Bryn , Wray Bevan , Mason-Jones Allan 
Published: September 2023

In this work, the impact of local blockage on the power production of a tidal array due to multiple turbines positioned in close proximity is studied. A numerical model of the HydroWing tidal energy device, which features multiple turbines on a retrievable wing, is being developed using geometry-resolved computational fluid dynamics (CFD). For this paper, the influence of two turbines at several spacings is considered.
The CFD model is used to perform quasi-static steady-state simulations of two turbines in a twin rotor configuration, where a multiple reference frame (MRF) approach is used to simulate rotor rotation. The lateral spacing between the rotors is varied and the resulting impact on the axial loads and power performance of the two turbines is studied, with the aim of identifying the optimal turbine spacing for the HydroWing device. The results will be used in future design optimisation work to minimize the levelized cost of energy of a large scale array using HydroWing technology at the proposed site for the Morlais tidal energy project.
Tracking a large vortex at a tidal power site
Authors: Mercier Philippe , Guillou Sylvain S. 
Published: September 2023

Tidal turbines are sensitive to the high turbulence of tidal flows. Large and intense vortices are generated at the seabed and cause extreme loads, fatigue damage and degraded power production. Thus, these vortices must be characterised prior to the turbine installation. The flow characteristics can be assessed through ADCP measurements, but these measurements are sparse. The vortex characteristics are strongly affected by the seabed macro-roughness (rocks, faults) that induces spatial variations of the flow characteristics at a local scale. These local variations are difficult to catch through measurements [1]. Numerical simulations, that cover large areas, can fill in the gaps of measurements. Reynolds Averaged Navier Stokes simulations cover wide domains, but do not simulate the turbulent motions. Large Eddy Simulations (LES) do simulate the turbulent motions, but are computationally expensive, which reduces their spatial and temporal coverages.
LES has been validated for the simulation of turbulence at a tidal power site, with a spatial coverage of about 0.5 km² and a temporal coverage of about 30 minutes [2,3]. However, the high turbulence intensity complicates the analysis of turbulent motions. The tracking and characterisation of vortices is complex and time-consuming. New methods to automate this work would be very welcome.
In this work, we use Large Eddy Simulations to simulate the vortices generated at the rocky seabed of the Paimpol-Bréhat tidal turbine test site (France). A tracking method is used to follow the movement of turbulent motions (see Figure 1). This tracking highlights the long durability of turbulent motions. The impact of the most intense motions on fictive turbines is assessed and extreme flow variations are observed. This confirms the interest of the method for an easy detection of the most troublesome vortices and the locations where they are generated. It paves the way for the identification of the locations where turbine installation should be avoided due to potential damaging turbulent motions.
[1] Togneri, M. & Masters, I. Micrositing variability and mean flow scaling for marine turbulence in Ramsey Sound. Journal of Ocean Engineering and Marine Energy, 2016, 2, 35-46
[2] Mercier, P.; Grondeau, M.; Guillou, S.S.; Thiébot, J. & Poizot, E. Numerical study of the turbulent eddies generated by the seabed roughness. Case study at a tidal power site. Applied Ocean Research, 2020, 97
[3] Mercier, P. & Guillou, S.S. The impact of the seabed morphology on turbulence generation in a strong tidal stream. Physics of Fluids, 2021, 33
Enhancing energy system resilience using tidal stream energy
Authors: Coles Danny , Coyne Richard , Miles Jon 
Published: September 2023

During autumn 2021, high global gas demand led to a 400% increase in imported wholesale gas prices in the UK. This coincided with (i) an extended period of low wind resource, where wind turbines provided 60% less energy than typical levels for the time of year, (ii) low nuclear power availability and (iii) depleting domestic natural gas reserves. These simultaneous events led to UK wholesale electricity prices more than doubling. The 2022 military and political impact of Russia’s invasion of Ukraine has led to additional increases in imported fuel prices. These types of disruption have the potential to cause damage worth years of sector revenues [1]. In the future, energy resilience challenges must be overcome whilst also achieving net-zero to limit global warming to within 1.5 degrees Celsius above pre-industrial levels, whilst electricity demand at least doubles.
This research investigates the role of tidal stream energy in enhancing energy system resilience during periods when the energy system is highly stressed, such as during autumn 2021 in the UK. The concept of resilience refers to the ability of the system to survive strong and unexpected disruptions and to recover quickly afterward [1]. This research is motivated by the acknowledgement that the commercial viability of marine power relies on the sector being able to explain how it can provide contributions beyond decarbonisation [2].
We build on an energy system modelling case study of the Isle of Wight [3], using the EnerSyM-RC energy system model. Wind data between 2012 – 2020 is analysed to identify and characterise periods of low wind resource. These data form the inputs to the EnerySyM-RC modelling. The model then applies a simple brute force optimisation method to investigate the most suitable mix of solar PV, offshore wind, tidal stream and energy storage that enhances system resilience on the Isle of Wight.
Initial results show that the adoption of tidal stream energy compliments solar and wind generation by reducing reliance on reserve energy (e.g. imported gas) during high-stress periods. Reduced reliance on imported energy is also achieved because of the distinct generation pattern of tidal power (i.e. 4 periods of power generation, each separated by slack tide, every day), which enhances the utilisation of local energy storage.
References
[1] Jasiunas J, et al., 2021, Energy system resilience – A review, Renewable and Sustainable Energy Reviews, 150:111476
[2] Pacific Northwest National Laboratory, 2021, Grid Value Proposition of Marine Energy: A Preliminary Analysis, PNNL -31123, Technical report
[3] Coles DS et al., 2023, Impacts of tidal stream power on energy system security: An Isle of Wight case study, Applied Energy, 334:120686
Effects of non-isotropic blockage on a tidal turbine modeled with the Actuator-Line method
Authors: Mascrier Enzo , Zilic de Arcos Federico , Pinon Grégory 
Published: September 2023

Blockage effects are a consequence of the interaction between a body and the surrounding boundaries in a constrained flow. For the case of tidal rotors, global blockage (β) is usually defined bythe ratio between the swept area of the rotor and the cross-sectional area of a channel. Increasingblockage tends to increase the limits of power extraction (Garrett and Cummins, 2007), as well asthrust on a rotor through an attendant increase of through-rotor mass flow. While these observations have been studied and demonstrated for isotropic blockage effects (e.g., Zilic de Arcos et al.2020, Bahaj 2007 , Mikkelsen 2002), questions remain regarding the validity of such assumptionsfor non-isotropic blockage in channels with, e.g., rectangular cross-sections with varying aspectratios.
In this work, we will use CFD simulations to analyze the effect of non-isotropic blockage on atidal rotor. The study aims to explore these effects using an Actuator-Line representation of anaxial-flow rotor, simulated under different blockage ratios (1 %, 5 %, 10%, and 19.7 %), aspectratios (0.25, 0.5, 0.75, and 1), and tip speed ratios (4, 5, 6, and 7). A total of 64 cases will beconsidered. For each simulated case, the power, thrust, and spanwise force distributions will beextracted as functions of time, and used to understand the effect of blockage on the performanceof tidal rotors.
Our preliminary results, in agreement with existing literature, indicate that blockage affectswake development, as seen in Figure , along with power and thrust. These results, for a constantaspect ratio, show power increases up to 26 % for a blockage of 20 %. The bulk of the simulationmatrix, including the different aspect ratios, is currently under production and is expected to beready before the paper submission deadline.

ReferencesGarrett, C., Cummins, P. (2007). The efficiency of a turbine in a tidal channel. Journal of fluidmechanics, 588, 243-251.Zilic de Arcos, F., Tampier, G., Vogel, C. R. (2020). Numerical analysis of blockage correctionmethods for tidal turbines. Journal of Ocean Engineering and Marine Energy, 6, 183-197Bahaj, A. S., Molland, A. F., Chaplin, J. R., Batten, W. M. J. (2007). Power and thrust measurements of marine current turbines under various hydrodynamic flow conditions in a cavitationtunnel and a towing tank. Renewable energy, 32(3), 407-426.Mikkelsen, R., Sørensen, J. N. (2002). Modelling of wind turbine blockage. In 15th IEAsymposium on the aerodynamics of wind turbines, FOI Swedish Defence Research Agency.
Towards increased social acceptability of marine renewable energy
Authors: Dunphy Niall P. , Lennon Breffní , Smith A. Luke , Uyarra María C. , Gonçalves Janete , Soulard Thomas , Zubiate Laura 
Published: September 2023

The development and deployment of novel technologies, including those associated with marine renewable energy, are vital for the ongoing decarbonisation of our energy system. However, technology on its own is not sufficient to realise the energy transition away from fossil fuels. Non-technical barriers – such as regulatory, economic, environmental or social aspects – can be a substantial impediment to widespread adoption of renewable energy technologies. One such impediment, is public opposition to specific deployments of renewable energy and/or indeed to the use of particular technologies. Within the SafeWAVE project, we are cognisant of the importance of good community relations and the need to develop two-way communication with stakeholders to facilitate the successful scaling up of ocean energy device deployments. Accordingly we have worked to co-develop and demonstrate a framework for education and public engagement (EPE), specifically aimed at ocean literacy for communities in France, Ireland, Portugal and Spain. This EPE framework aims to go beyond social acceptance, which is often equated to acquiescence to a fait accompli, and is designed to contribute to the development of projects which exhibit inherent social acceptability.
This paper presents the work within SafeWAVE project to develop the EPE framework with input from the communities. The first part of the paper reports on critical review of selected EPE programmes associated with marine energy test sites and infrastructure deployments, with methods adopted in each case analysed, key challenges faced identified, and best practices documented. Next a framework for public education and engagement is presented, which builds on this review and draws from literature across multiple disciplines – including sociology, psychology, political science, education. Finally, leveraging this developed knowledge the collaborative process of deriving tailored EPE programmes on ocean literacy around marine renewables for the four focal communities is outlined and described. These programmes are intended to reach out to, and engage with, local communities, interested stakeholders and the wider public on issues surrounding the deployment of ocean energy devices, including but not limited to: effects on local communities, implications for marine life, potential impacts for water users, etc.
The paper concludes by discussing the experience of developing the bespoke programmes, outlining emergent feedback from trialling of key elements of the programmes, discussing experiences and proffering guidance based on lessons learned.
Turbine fatigue load prediction from field measurements of waves and turbulence
Authors: Mullings Hannah , Stallard Tim , Draycott Samuel 
Published: September 2023

The interest in this work is understanding the conditions which contribute to the cyclic loading experienced by a tidal turbine. Tidal turbines are placed in locations with high flow speeds in order to extract maximum kinetic energy. These flow speeds combined with other environmental factors can lead to a complex operating conditions. When assessing turbine loading across a site, most models use ambient flow conditions, with very few codes including the impact of waves with currents. Previous studies have analysed the influence of wave conditions from measurements on the loading, through a consideration of the turbine not operating. Although tidal conditions are bi-directional, wave conditions do vary with direction and this combination will be investigated in this study.
Full-scale site data was gathered at Le Raz Blanchard, a potential tidal site as part of the Interreg funded TIGER project. The focus in this study is on data gathered which provides both wave and current conditions over a period of 45 days. Loading on the turbine components is assessed through an efficient blade element momentum theory method, which is combined with a synthetic turbulence model to provide a time-varying onset flow. This work determines the impact of the measured waves, and the way in which they are analysed on the turbulence characteristics in the onset flow, specifically the interaction of waves with current and influence on the loading experienced on the turbine.
Hybrid wind-wave systems: The case of the VolturnUS-S semi-submersible platform
Authors: Hengstmann Maximilian , Portillo Juan Carlos Chong , Gato Luís Manuel de Carvalho 
Published: September 2023

Wind-wave hybrid floating systems are subject to active research and development in academia and industry. Industrialization of hybrid wind-wave energy systems will benefit from modular designs, allowing floating platforms to be used with or without wave energy converters (WECs). This work explores the design process to use oscillating water column (OWC) WECs as modular add-on features to existing semi-submersible floating platform designs. As the base case design, the IEA 15 MW offshore reference wind turbine with the VolturnUS-S floating platform designed by the University of Maine was used. A design approach was proposed, which involved various tools, such as OpenFAST developed by NREL, and the OWC Modelica tool developed at IST/ULisboa. Aero-hydro-servo-elastic simulations were performed to analyze the influence of the wind turbine energy generation design modifications and damage equivalent loads (DELs). The hybrid platform was modeled in the OWC Modelica tool to assess the wave energy conversion and the interaction between OWCs and the floating platform. The investigated hybrid design did not significantly increase DELs of the wind turbine in aero-hydro-servo-elastic simulations. The hybrid system does not decrease the LCOEcompared to a standalone floating wind turbine. The main cost driver was identified to be the material of the OWCs' ducts. Furthermore, the coupling forces between OWCs and the floating platform were found to be in the same order of magnitude as the wave excitation and radiation forces. The possibilities of including these forces in OpenFAST and the challenges for this are discussed.