Development of a Multi-Objective Genetic Algorithm for the Design of Offshore Renewable Energy Systems

This is the author accepted manuscript. The final version is available from the publisher via the URL in this record.Optimization algorithms have been deployed for a range of renewable energy problems and can successfully be applied to aid in the design of devices, farms, control strategies, and operations and maintenance strategies. Building on this, the present work makes use of a multi-objective genetic algorithm (GA) in order to develop a framework that can further aid in the design and development of offshore renewable energy systems by explicitly taking into account reliability considerations. Though the reliability-based design optimization approach has previously been used in offshore renewable energy applications and multi-objective optimization applications, it has not previously been applied to multi-objective offshore renewable energy design optimization. As the offshore renewable energy sectors grows it is important for the industry to explore more sophisticated methods of designing devices in order to ensure that the device reliability and lifetime can be maximized while downtime and cost are minimized. This paper describes the development of a framework using a GA in order to aid in the design of a mooring system for offshore renewable energy devices. This framework couples numerical models of the mooring system and structural response to both stress-life cumulative damage models and cost models in order for the GA to effectively operate considering the multiple objectives. The use of this multi-objective optimization approach allows multiple design objectives such as system lifetime and cost to be satisfied simultaneously using an automated mathematical approach. From the outputs of this approach, a designer can then select a solution which appropriately balances the different objectives. The developed framework will be applicable to any offshore technology subsystem allowing multi-objective optimization and reliability to be considered from the design stage in order to improve the design efficiency and aid the industry in using more systematic design approaches.This work is funded by the EPSRC (UK) grant for the SuperGen United Kingdom Centre for Marine Energy Research (UKCMER) [grant number: EP/P008682/1]

Mooring System Design Optimization Using a Surrogate Assisted Multi-Objective Genetic Algorithm

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this record.This article presents a novel framework for the multi-objective optimization of o shore re- newable energy mooring systems using a random forest based surrogate model coupled to a genetic algorithm. This framework is demonstrated for the optimization of the mooring system for a oating o shore wind turbine highlighting how this approach can aid in the strategic design decision making for real-world problems faced by the o shore renewable energy sector. This framework utilizes validated numerical models of the mooring system to train a surrogate model, which leads to a computationally e cient optimization routine, allowing the search space to be more thoroughly searched. Minimizing both the cost and cumulative fatigue damage of the mooring system, this framework presents a range of op- timal solutions characterizing how design changes impact the trade-o between these two competing objectives.This work is funded by the EPSRC (UK) grant for the SuperGen Marine United Kingdom Centre for Marine Energy Research (UKCMER) [grant number: EP/P008682/1]. The authors would also like to thank Jason Jonkman at NREL who provided the hydrodynamic data for the OC4 semi-submersible and Orcina Ltd. for providing OrcaFlex

Offshore Wind Farm Electrical Cable Layout Optimization

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this record.This article explores an automated approach for the efficient placement of substations and the design of an inter-array electrical collection network for an offshore wind farm through the minimization of the cost. To accomplish this, the problem is represented as a number of sub-problems that are solved in series using a combination of heuristic algorithms. The overall problem is first solved by clustering the turbines to generate valid substation positions. From this, a navigational mesh pathfinding algorithm based on Delaunay triangulation is applied to identify valid cable paths, which are then used in a mixed-integer linear programming problem to solve for a constrained capacitated minimum spanning tree considering all realistic constraints. The final tree that is produced represents the solution to the inter-array cable problem. This method is applied to a planned wind farm to illustrate the suitability of the approach and the resulting layout that is generated

The influence of ground conditions on the performance of shared anchor systems for floating offshore wind

This is the author accepted manuscript.Significant growth of the floating offshore wind sector is anticipated over the next decade as developers target increasingly deeper sites. The efficient design of mooring systems and innovative anchor layouts will be critical in driving down the cost of this technology. Sharing anchors would lead to a reduction in total number of components to be fabricated and installed. It is also perceived that shared anchors may be smaller, facilitating installation by more readily available and cheaper vessels. These shared anchors must, however, be designed to withstand loading from multiple directions and for an increased number of fatigue load cycles. The efficiencies that can be gained from anchor sharing will vary depending on anchor type, mooring line type, applied loading, and ground conditions. This paper presents a study of the anchor types that would typically be considered for three representative sites with a common water depth, but varying ground conditions to include soft clays, dense sands, and shallow bedrock. The suitability of each anchor type for use in a shared anchor system is evaluated for the representative sites, and the anchor performance is com pared across the different soil types

Experimental data of bottom pressure and free surface elevation including waves and current interaction

This is the final version. Available on open access from MDPI via the DOI in this recordData Availability Statement: The data presented in this study are openly available: https://doi.org/10.7488/ds/3120.Abstract: Force plates are commonly used in tank testing to measure loads acting on the foundation of a structure. These targeted measurements are overlaid by the hydrostatic and dynamic pressure acting on the force plate induced by the waves and currents. This paper presents the dataset of bottom force measurement with a six degree-of-freedom force plate (AMTI OR6-7 1000, surface area 0.464 m×0.508 m) combined with synchronised measurements of surface elevation and current velocity. The data covers a wave frequencies between 0.2 to 0.7 Hz and wave direction between 0◦ and 180◦ . These variations are provided for 0 and 0.2 m/s current speed and a variation of current in the absence of waves covering 0 to 0.45 m/s. The dataset can be utilised as a validation dataset for models predicting bottom pressure based on free surface elevation. Additionally, the dataset provides the wave and current induced load acting on the specific load cell and a fixed water depth of 2 m, which can subsequently be removed to obtain the often-desired measurement of structural loadsEngineering and Physical Sciences Research Council (EPSRC

An Energy Management System for the control of battery storage in a grid-connected microgrid using mixed integer linear programming

This is the final version. Available on open access from MDPI via the DOI in this recordData Availability Statement: The data is available from the lead or the corresponding author upon reasonable requestsThis paper proposes an Energy Management System (EMS) for battery storage systems in grid connected microgrids. The battery charging/discharging power is determined such that the overall energy consumption cost is minimized, considering the variation in grid tariff, renewable power generation and load demand. The system is modelled as an economic load dispatch optimization problem over a 24-hours horizon and solved using mixed integer linear programming (MILP). This formulation, therefore, requires knowledge of the expected renewable energy power production and load demand over the next 24 hours. To achieve this, a long short-term memory (LSTM) network is proposed. The Receding Horizon (RH) strategy is suggested to reduce the impact of prediction error and enable real-time implementation of the EMS that benefits from using actual generation and demand data on the day, the Receding Horizon (RH) strategy is suggested. At each hour, the LSTM predicts generation and load data for the next 24 hours, the dispatch problem is then solved, and the battery charging or discharging command for only the first hour is applied in real-time. Real data is then used to update the LSTM input, and the process is repeated. Simulation results show that the proposed real-time strategy outperforms the offline optimisation strategy reducing the operating cost by 3.3%.Petroleum Technology Development Fund of Nigeri

Wave buoys in current - experimental results and observations

This is the author accepted manuscript. The final version is available from EWTEC via the link in this recordWave buoys are used extensively for the characterisation of deployment locations for offshore technologies, where they are subjected to currents in addition to the ocean waves. It has been frequently observed that the measurements from wave buoys are affected by these currents, but the majority of deployed buoys cannot measure, or account for, this effect. Presented here are a series of experiments conducted at the FloWave Ocean Energy Research Facility, deploying a spherical wave buoy scale model with a simplified mooring in a series of combined wave-current sea states. The resulting openaccess dataset provides 6 degree of freedom buoy motion and force data (current only) in addition to wave gauge and acoustic doppler velocimeter measurements of the sea states. Experiments were conducted under a range of combined wave-current conditions with variables including velocity, wave period, and relative wave-current angle. It is observed that vortex induced motions (VIM) are significant and highly sensitive to the mooring configuration and current speed. Nevertheless, the wave-induced response and buoy motion amplitude is found to agree with linear wave-current theory predictions in most following wavecurrent conditions. This agreement is poorer in opposing conditions where larger surge motions than predicted are consistently observed. Wave buoy outputs in directional irregular seas were also found to closely match wave gauge outputs. If properly considered, it is suggested that the effect of the current on existing buoy technologies may be accounted for without hardware modification or additional sensing, but through updated analytical tools.Engineering and Physical Sciences Research Council (EPSRC

Methodology to prepare for UK’s offshore wind Contract for Difference auctions

This is the final version. Available on open access from Elsevier via the DOI in this recordIn the UK, the Contract for Difference (CfD) subsidies for renewable energy generation are awarded through a competitive auction process. This paper simulates the most recent CfD auction for offshore wind, using a novel methodology to assist developers in preparing their bid strategy and for policymakers to test auction efficiency. The simulation’s results show developer’s leading strategy is to shade their bid to increase auction pay-off. A developer’s incentive to shade their bid depends on the project’s capacity and minimum bid price; the offshore wind farm Hornsea 3 has the greatest incentive to shade its bid as its optimum bid price is further from its cost price, and results in the highest expected value of additional auction pay-off. The median strike price estimated by the model is £39.23/MWh, and the most likely winners, as predicted from the simulations, are Hornsea 3, Inch Cape, East Anglia 3 and Norfolk Boreas. Published auction results show that the estimated strike price from the simulation is 5% higher than the £37.35/MWh awarded strike price; however, the model successfully predicted the winners. Further analysis of results demonstrates that developers adopted a risk-averse bidding strategy, bidding at a pre-determined floor (coexist) price, guaranteeing subsidy. As a result, £38 million of the subsidy budget was unused

Co-Creation of Breast Cancer Risk Communication Tools and an Assessment of Risk Factor Awareness: A Qualitative Study of Patients and the Public in India.

BACKGROUND: Low awareness of BC and its associated risk factors causes delays in diagnosis and impacts survival. It is critical to communicate BC risk to patients in a format that they are easily able to understand. Our study aim was to develop easy-to-follow transmedia prototypes to communicate BC risk and evaluate user preferences, alongside exploring awareness of BC and its risk factors. METHODS: Prototypes of transmedia tools for risk communication were developed with multidisciplinary input. A qualitative in-depth online interview study was undertaken using a pre-defined topic guide of BC patients (7), their relatives (6), the general public (6), and health professionals (6). Interviews were analyzed using a thematic approach. FINDINGS: Most participants preferred pictographic representations (frequency format) of lifetime risk and risk factors and storytelling using short animations and comic strips (infographics) for communicating genetic risk and testing: "In a short time, they explained it very well, and I liked it". Suggestions included minimizing technical terminology, decreasing the delivery speed, "two-way dialogue", and using local "language for different locations". There was low awareness of BC, with some understanding of age and hereditary risk factors but limited knowledge of reproductive factors. INTERPRETATION: Our findings support use of multiple context-specific multimedia tools in communicating cancer risk in an easy-to-understand way. The preference for storytelling using animations and infographics is a novel finding and should be more widely explored

The pathogenesis of low pathogenicity H7 avian influenza viruses in chickens, ducks and turkeys

<p>Abstract</p> <p>Background</p> <p>Avian influenza (AI) viruses infect numerous avian species, and low pathogenicity (LP) AI viruses of the H7 subtype are typically reported to produce mild or subclinical infections in both wild aquatic birds and domestic poultry. However relatively little work has been done to compare LPAI viruses from different avian species for their ability to cause disease in domestic poultry under the same conditions. In this study twelve H7 LPAI virus isolates from North America were each evaluated for their comparative pathogenesis in chickens, ducks, and turkeys.</p> <p>Results</p> <p>All 12 isolates were able to infect all three species at a dose of 10⁶50% egg infectious doses based on seroconversion, although not all animals seroconverted with each isolate-species combination. The severity of disease varied among isolate and species combinations, but there was a consistent trend for clinical disease to be most severe in turkeys where all 12 isolates induced disease, and mortality was observed in turkeys exposed to 9 of the 12 viruses. Turkeys also shed virus by the oral and cloacal routes at significantly higher titers than either ducks or chickens at numerous time points. Only 3 isolates induced observable clinical disease in ducks and only 6 isolates induced disease in chickens, which was generally very mild and did not result in mortality. Full genome sequence was completed for all 12 isolates and some isolates did have features consistent with adaptation to poultry (e.g. NA stalk deletions), however none of these features correlated with disease severity.</p> <p>Conclusions</p> <p>The data suggests that turkeys may be more susceptible to clinical disease from the H7 LPAI viruses included in this study than either chickens or ducks. However the severity of disease and degree of virus shed was not clearly correlated with any isolate or group of isolates, but relied on specific species and isolate combinations.</p