Growing The Marine Energy Supply Chain In Wales

To mitigate Climate Change and reduce greenhouse gas emissions, Europe is currently the World leader for exploiting one of the most significant sources of global untapped renewable energy; energy from our oceans.Within Europe, the UK is foremost to establish a sustainable marine energy industry, through research, development and supply chain growth.This article will examine the Skills and Training Needs Analysis work undertaken by Swansea University, to provide training courses designed to grow the marine energy supply chain within Wales and thus support and sustain Europe’s leading status

Influence of directional wave spreading on a WEC device

Wave Energy Converter (WEC) performance is generally sensitive to the wave direction. So, it is important to include the effect of multi-directional waves in numerical modelling. A realistic representation of ocean waves should account for wave height and directional spreading parameters specific to the WEC deployment location. A high quality generalised directional distribution is dependent on the wave direction and frequency. Here we compare the power produced, the wave field, and the motion of the WaveSub device for different frequency-directional distribution cases. Directional spreading has been modelled using different model distributions such as the uniform cosine fourth, Mitsuyasu, Hasselman and Donelan-Banner. The hydrodynamic coefficients are computed for all wave directions using Nemoh. Then, the WEC-Sim code has been extended to add the capability to simulate different user selected frequency-directional spreading. The excitation force applied to each hydrodynamic body is updated to account for the effect of the directional spectrum. Results show that power produced is generally 10-20% lower than a single direction case. The motion of the device demonstrates the introduction of sway, roll, and yaw for the directional spreading simulations while the resultant wavefield is more uniform compared to the non-directional case. Computational time is significantly lower than comparable CFD approaches and this makes this method particularly effective

From New Public Management to Lean thinking: understanding and managing 'potentially avoidable failure induced demand'

The central objective of this thesis is to investigate, understand and explain the conditions under which the administrative problem known as potentially avoidable failure induced demand (PAFID) arises in UK public services and might be prevented. PAFID is defined as “customer contacts that appear to be precipitated by earlier failures, such as failures to do things right first time, which cause additional and potentially avoidable demands to impinge upon public services”. A secondary objective of the thesis is to establish how, and under what better conditions, the public sector could successfully exploit the management paradigm called Lean thinking, as an alternative to the current New Public Management method, in order to address the PAFID problem. An analysis of the results from three case-studies conducted in UK local authority settings confirms that nearly half of all customer contacts in high-volume services such as housing benefits are potentially avoidable. The extrapolation of this finding to the contact volumes and handling costs in one UK council alone suggests possible savings of more than £1 million a year. The potential benefits that are available to the case-study councils and nearly 500 other local councils, together with numerous other providers of UK public services, are also very substantial. A variety of conceptual lenses are applied to the PAFID problem in order to generate alternative explanations and policy options. This thesis makes a number of contributions to public sector management theory and practice, including the finding that councils might reduce principal-agent problems that add to PAFID by espousing more supportive and enabling environments, and by adopting systems-oriented approaches that acknowledge the complex and subjective nature of real-world problems. The findings also suggest that, while the deployment of Lean ‘tools’ can result in short-term savings and performance improvements, the adoption of Lean thinking as a comprehensive management approach is more likely to bring about fundamental changes

Investigation of new layout design concepts of an array-on-device WaveSub device

Wave Energy Converters (WECs) have not yet proven their competitiveness in the mainstream energy market. Research and development of this technology are necessary to find optimal solutions in terms both of energy produced and reduced cost. A WEC farm is expected to have reduced Levelized Cost of Energy (LCoE) compared to individual devices due to shared installation and grid connection costs. Studies show that energy yield of a WEC array is highly dependent on spacing and layout of the WECs. A method for selecting an optimal array layout is desirable.Here we show a comparison between 4 different design layouts of a WaveSub device with six floats. A six float configuration has been chosen because the LCoE reduces with increasing floats per device as shown in previous research. An optimal configuration in terms of LCoE and rated power is found for linear, rectangle, triangle and circular multi-float configurations. Parameters optimised are float spacing and Power Take Off (PTO) stiffness, damping and rated power. The optimisation algorithm uses a genetic algorithm combined with a Kriging surrogate model. Numerical simulations are solved in the time-domain in WEC-Sim while the hydrodynamic coefficients are calculated in Nemoh using a linear potential flow theory.For all geometric configurations, the smallest float spacing was the most promising because of the lower cost of the structure. In fact, the influence of the float spacing on the power produced by the device is shown to be less significant than the influence of float spacing on the capital cost. Overall, the circular configuration outperformed the other configurations. This study shows that layout configurations can be investigated with optimisation and this could be applied to other configurations and other WEC concepts in future

Biaxial experimental characterizations of soft polymers: A review

Soft polymeric materials such as elastomers and hydrogels have played a significant role in recent interdisciplinary research. They are subjected to large stretch and high cyclic loading-unloading conditions where the typical loading mode is biaxial rather than simple uniaxial loading thus, necessitating further characterization using biaxial loading conditions and subsequently developing robust and versatile numerical models. Although many standards were prepared for common uniaxial tests in situ elastomers including tensile, shear, and fatigue tests, no specific standardized guidelines were prepared to be employed for the biaxial characterization of elastomers and hydrogels. There existed limited works on the biaxial characterization of soft polymers, thus making it difficult to identify which configurations and results are more reliable. Hence, there were huge discrepancies in the existing literature for biaxial tests in terms of sample configurations (square or cruciform specimens), dimensions, and test setups including strain rate, pre-loading, equi-biaxial and unequi-biaxial tests. Therefore, this paper is aimed at reviewing the published studies on the biaxial characterization of soft polymers in several aspects including (i) sample configurations in terms of geometry and dimension (ii) biaxiality degree of tested specimens where sample should be optimized to reach proper biaxiality, i.e., larger area with homogenous strain distribution in the middle with respect to the edges, (iii) test procedure for the biaxial characterization including strain amplitude, strain rate and loading patterns (iv) a brief review on inflation test of elastomers which was the most common equi-biaxial test studied in the literature. The largest and smallest cruciform samples with the dimensions of 165 × 165 mm2 and 38 × 38 mm2 were used, respectively, while a small sample of 7 × 7 mm2 and large one of 70 × 70 mm2 were also employed for the square specimen. Various test parameters and materials were used for the biaxial characterization. This necessitates the importance of preparing a standardized methodology for the biaxial characterization of elastomers based on intended materials and applications. Hence, a few potential geometries based on the optimization performed in the literature were suggested for future investigations in which numerous examinations using different materials and test parameters shall be conducted to reach an ideal sample configuration and methodology for the biaxial characterization of soft polymeric materials

The cumulative impact of tidal stream turbine arrays on sediment transport in the Pentland Firth

This contribution investigates the impact of the deployment of tidal stream turbine arrays on sediment dynamics and seabed morphology in the Pentland Firth, Scotland. The Pentland Firth is arguably the premier tidal stream site in the world and engineering developments are progressing rapidly. Therefore understanding and minimising impacts is vital to ensure the successful development of this nascent industry. Here a 3 dimensional coupled hydrodynamic and sediment transport numerical model is used to investigate the impact on sediment transport and morphodynamics of tidal stream arrays. The aim of the work presented here is twofold: firstly to provide prediction of the changes caused by multiple tidal stream turbine array developments to some of the unique sandy seabed environments in the Pentland Firth and secondly as a case study to determine the relationship between impacts of individual tidal stream farms and cumulative impacts of multiple farms. Due to connectivity in tidal flow it has been hypothesized that the cumulative impact of multiple arrays on sediment dynamics might be non-linear. This work suggests that, for the Pentland Firth, this is not the case: the cumulative impact of the 4 currently proposed arrays in the area is equal to the sum of the impacts of the individual arrays. Additionally, array implementation only has minimal effect on the baseline morphodynamics of the large sandbanks in the region, smaller more local sandbanks were not considered. These two results are extremely positive for tidal stream developers in the region since it removes the burden of assessing cumulative impact from individual developers and suggests that impacts to sub-sea morphodynamics is insignificant and hence is unlikely to be an impediment to development in the Pentland Firth with the currently proposed levels of extraction

Similarity Measures for Enhancing Interactive Streamline Seeding

Streamline seeding rakes are widely used in vector field visualization. We present new approaches for calculating similarity between integral curves (streamlines and pathlines). While others have used similarity distance measures, the computational expense involved with existing techniques is relatively high due to the vast number of euclidean distance tests, restricting interactivity and their use for streamline seeding rakes. We introduce the novel idea of computing streamline signatures based on a set of curve-based attributes. A signature produces a compact representation for describing a streamline. Similarity comparisons are performed by using a popular statistical measure on the derived signatures. We demonstrate that this novel scheme, including a hierarchical variant, produces good clustering results and is computed over two orders of magnitude faster than previous methods. Similarity-based clustering enables filtering of the streamlines to provide a nonuniform seeding distribution along the seeding object. We show that this method preserves the overall flow behavior while using only a small subset of the original streamline set. We apply focus + context rendering using the clusters which allows for faster and easier analysis in cases of high visual complexity and occlusion. The method provides a high level of interactivity and allows the user to easily fine tune the clustering results at runtime while avoiding any time-consuming recomputation. Our method maintains interactive rates even when hundreds of streamlines are used

Genetic based optimisation of the design parameters for an array-on-device orbital motion wave energy converter

Optimisation of Wave Energy Converters (WECs) is a very important topic to obtain competitive devices in the energy market. Wave energy is a renewable resource that could contribute significantly to a future sustainable world. Research is on-going to reduce costs and increase the amount of energy captured. This work aims to optimise a WaveSub device made up of multiple floats in a line by investigating the influence of 6 different design parameters such as the number of floats. Here we show that a multi-float configuration of 6 floats is more competitive in terms of Levelised Cost Of Energy (LCOE) compared to a single float configuration with a LCOE reduction of around 21%. We demonstrate that multi-float configurations of this device reduce the LCOE especially because of the reduction of grid connection, installation, control and mooring costs. From the power capture perspective, optimized multi-float configurations still have similar capacity factors to the single float configuration. This research gives important indications for further development of the WECs from an optimisation perspective. These promising results show that more complex, optimized, multi-float configurations could be investigated in future

On the influence of time-dependent behaviour of elastomeric wave energy harvesting membranes using experimental and numerical modelling techniques

The transient response of elastomeric polymers is dependent on polymer composition, temperature and the loading history. In particular, hysteresis, dissipation and creep are significant in the choice of material for elastomer membrane wave energy converters. Natural rubber is a good candidate when looking for material for a wave energy harvester since it has an excellent stretchability, is almost resistant to the environment in which the harvester will be used and has good fatigue properties. The mechanical behaviour of the natural rubber used in this work has been deeply characterised: the material resulted to have a very little hysteretical behaviour (that is a very low energy dissipation during stretching) but also to show a strain-dependency, stress softening, and relaxation at constant stretch. Low dissipation represents the best case scenario for energy harvesting; in reality reinforcement of the material is required which adds to the dissipative behaviour. Afterwards, an extended finite strain viscoelastic constitutive model is proposed that is calibrated analytically to the experimental data to identify the relevant material parameters resulting in non-linear viscosity functions in the evolution equations of the constitutive model. The model was able to capture the minimal dissipation behaviour with good degrees of accuracy. Results are shown for a flexible membrane wave energy converter under creep and cyclic loading. A parametric study is made comparing the experimentally characterised polymer with different amounts of viscous dissipation. The response of the wave energy converter shows that even minimal amounts of dissipation manifests itself into changes in the pressure–volume function and reduction in energy capture through hysteresis. The new material model shows, for the first time, that the control of internal pressure in wave energy membranes must take into account transient material effects