The Supergen wind research consortium is a group of research centres which undertake research primarily aimed at reducing the cost of offshore wind farming. Research is undertaken to apply the WRF mesoscale NWP model to the field of offshore wind resource assessment to assess its potential as an operational tool. WRF is run in a variety of configurations for a number of locations to determine and optimise a level of performance and assess how accessible that performance might be to an end user. Three studies set out to establish a level of performance at two different sites and improve performance through optimisation of model setup and post processing techniques. WRF was found to simulate wind speed to an appreciable level by reference to similar studies, though performance was found to vary throughout the course of the model runs and depending on the location. An average correlation coefficient of 0.9 was found for the Shell Flats resource assessment at 6-hourly resolution with an RMSE of 1.7ms-1. Performance at Scroby Sands was not at as high a level as that seen for Shell Flats with an average correlation coefficient for wind speed of 0.64 with an RMSE of 2ms-1. A range of variables were simulated by the model in the Shell Flats investigation to test the flexibility of the model output. Wind direction was produced to a moderate level of accuracy at 10-minute resolution while aggregated stability statistics showed the model had a good appreciation of the frequency of cases observed. Areas of uncertainty in model performance were addressed through model optimisation techniques including the generation of two ensembles and observational nudging. Both techniques were found to add value to the model output as well as improving performance. The difference between performance observed at Shell Flats and Scroby Sands shows that while the model clearly has inherent skill it is sensitive to the environment to which it is applied. In order to maximise performance, as large a computing resource as possible is recommended with a concerted effort to optimise model setup with the aim of allowing it to perform to its best ability. There is room for improvement in the application of mesoscale NWP to the field of offshore wind resource assessment but these results confirm an inherent skill in model performance. With the addition of further validation, improvements to model setup on a case by case basis and the application of optimisation techniques, it is anticipated mesoscale NWP can perform to a level which would justify its adoption operationally by the industry. The flexibility which can be offered relating to spatial and temporal coverage as well as the range of variables which can be produced make it an attractive option to developers if performance of a consistently high level can be established.

With the increasing interest in offshore wind power, the related technologies, including HVDC networks, are gaining similar levels of attention. For large scale wind farms far from shore, high voltage DC transmission can provide several advantages over traditional high voltage AC transmission. This thesis focuses on DC/DC converters, a core part of the HVDC network, especially for use in the high voltage, high power and offshore wind environment. The thesis examines a wide range of possible DC/DC converter topologies for the application. Different topologies are compared and evaluated in detail for use in a high power situation. Based on these results, three DC/DC converter topologies are selected for more detailed modelling. The simulation processes and results are presented in the thesis, which reveals the limitations and behaviour of the topologies when they are used at the MW level. In addition, the high power semiconductor switching devices are discussed and evaluated for each topology. To assess the suitability of the DC/DC converter topologies in the offshore wind application, the selected converter topologies are also analysed and modelled combined with a PMSG wind turbine. Finally, a down-scaled DC/DC converter prototype is built to verify the analysis and simulation results.

Until today the offshore wind power has grown in a steady pace and many new wind farms are being constructed around the globe. An important factor that is investigated today in the industry are the security of power supply to the equipment needed for controlling the offshore system during emergency situations. When a offshore wind farm is disconnected from the external grid and an emergency case occur the wind turbine generators lose their ability to transfer power and they are forced to be taken out of operation. As there are a number of loads in the wind turbines (navigation lights, sensor- and communication-apparatus, ventilation- and heating equipment etc.) they have a load demand which must be supplied in emergency mode. The German Transmission System operator (TSO) TenneT GmbH has set a requirement that the wind turbines is to be supplied by an auxiliary power supply (APS) in 12 hours and therefore there is need for a long-term auxiliary power supply system. This master thesis was assigned to investigate the most feasible APS-system. From the study of a number of different APS's one concept was chosen. This was the diesel gen-set solution placed on an offshore substation at sea. The system was modeled in the software DIgSILENT PowerFactory where a load flow analysis validated the calculated data and a study of the impact of  transients in the system was performed.

A rapid development of offshore wind power is planned in GB as a part to fulfil the EU2020 targets. 25 GW wind power capacity has been awarded to developers in nine different offshore zones outside the coast of UK. VSC-HVDC transmission is expected to be a both technical and economical favourable solution for transmitting the power into the main grid. This study investigates if such a transmission solution could comply with the regulatory framework in UK. Vattenfall and Scottish Energy Renewable will be part of this development and have been awarded the rights to develop 7200 MW of wind capacity outside the cost of East Anglia as a part of the offshore expansion plans in UK. The zone is broken down to several projects. The first project is called East Anglia ONE and this project is used as a reference case in this study. The GB Grid Code has been broken down into four areas, voltage and frequency variations; fault ride through requirements, active power control and reactive power control. Load flow calculations and dynamic simulations are designed to investigate compliance of each area. Further, simulations to investigate the interaction between the wind turbines and the offshore converter stations where done. A model representing East Anglia ONE was built in PSS/E and used to investigate grid codes compliance by load flow calculations and dynamic simulations. Data from earlier studies at Vattenfall was used to get a good representation of the wind park. A model representing a HVDC-transmission solution was provided by ABB. The results from load flow calculations and simulations show that a HVDC-solution can comply with the investigated parts of the grid codes. The limiting factor seems to be the capability to inject enough reactive power to the gird at small voltage dips during normal operation. This capability can, however, be enhanced with the right tap-changer settings at the onshore converter transformer.

This research study developed basic dynamic models that can be used to accurately predict the response behavior of a near-shore wind turbine structure with monopile, suction caisson, or gravity-based foundation systems. The marine soil conditions were modeled using apparent fixity level, Randolph elastic continuum, and modified cone models. The offshore wind turbine structures were developed using a finite element formulation. A two-bladed 3.0 megawatt (MW) and a three-bladed 1.5 MW capacity wind turbine were studied using a variety of design load, and soil conditions scenarios. Aerodynamic thrust loads were estimated using the FAST Software developed by the U.S Department of Energy’s National Renewable Energy Laboratory (NREL). Hydrodynamic loads were estimated using Morison’s equation and the more recent Faltinsen Newman Vinje (FNV) theory. This research study addressed two of the important design constraints, specifically, the angle of the support structure at seafloor and the horizontal displacement at the hub elevation during dynamic loading. The simulation results show that the modified cone model is stiffer than the apparent fixity level and Randolph elastic continuum models. The effect of the blade pitch failure on the offshore wind turbine structure decreases with increasing water depth, but increases with increasing hub height of the offshore wind turbine structure.

Forecasting capital expenditures in early stages of an offshore wind power project is aproblematic process. The process can be affected by optimism bias and strategicmisrepresentation which may result in cost overruns. This thesis is a response to issuesregarding cost overruns in offshore wind power projects. The aim of this thesis is tocreate a cost forecasting method which can estimate the necessary capital budget in awind power project. The author presents a two-step model which both applies the inside view and outsideview. The inside view contains equations related to investment and installation costs.The outside view applies reference class forecasting in order to adjust the necessary costcontingency budget. The combined model will therefore forecast capital expenditures fora specific site and adjust the cost calculations with regard to previous similar projects. The results illustrate that the model is well correlated with normalized cost estimationsin other projects. A hypothetical 150MW offshore wind farm is estimated to costbetween 2.9 million €/MW and 3.5 million €/MW depending on the location of the windfarm.

Little is known about the impact of marine renewable energy installations upon the marine environment and those who use it. Harnessing marine energy will involve the offshore siting of energy extraction devices and their associated infrastructure. This will alter the local environment and substantially modify use and access for a variety of marine stakeholders, potentially leading to conflict. Using the Ecosystem Approach (EA) as a conceptual framework, this thesis aimed to answer the question: What is the potential for conflict between the marine renewable energy industry and marine stakeholders, and how can this be mitigated? The research consisted of three components which used a variety of methods: i) stakeholder identification through a review of the literature and use of a novel interactive mapping method; ii) an investigation of the potential consequences for the priority stakeholder which used a mail survey and in-depth interviews; and iii) an exploration of potential mitigation which used ecosystem modelling. The stakeholder most likely to be affected by marine renewable energy device (MRED) deployment was the fishing industry. Potential consequences included: navigation and safety hazards, loss of access and alternative employment. Further exploration revealed that a loss of livelihood was the all-encompassing concern for fishers, and that skills shortages (transferable skills) may mean that should a loss of livelihood occur there may not be acceptable alternative employment. The modelling exercise indicated that it is not currently possible to definitively predict whether any opportunities which may be created by MRED installation will mitigate any negative effects, and that exclusion zones may actually decrease catches for most fleets. The findings of this study have implications for ‘conflict-free’ development of the marine renewable energy industry. To address this, several policy recommendations were offered as regards to operationalising the EA in terms of marine renewable energy.

Wind energy is recognized as a sustainable source of energy that is both reliable and capable of dramatically reducing pollution to the environment and dependency on non-renewable fuels, leading to research on wind turbines. Nowadays, the demand for electricity increases. Considering that the greater the distance from shore, the greater the wind, more electricity will be generated along the coast. It is necessary and beneficial to study large scale offshore wind turbines. The National Renewable Energy Lab (NREL) 5-MW offshore wind turbine is simulated using a three-dimensional computational fluid dynamics (CFD) model in this article. A realizable k-ε viscous model is used to simulate turbulence flow. The work is validated by comparing the torque with published simulated data, and satisfied consistency is observed. Further simulation and comprehensive analysis demonstrate the flow features and aerodynamic performances of 5-MW offshore wind turbine under various wind and rotor speeds. The velocity profiles, total pressure distribution, pressure coefficient, rotor thrust, torque and aerodynamic properties are obtained in detail.

A literature review of current design and analysis methods for offshore wind turbine (OWT) foundations is presented, focusing primarily on the monopile foundation. Laterally loaded monopile foundations are typically designed using the American Petroleum Institute (API) p-y method for offshore oil platforms, which presents several issues when extended to OWTs, mostly with respect to the large pile diameters required and the effect of cyclic loading from wind and waves. Although remedies have been proposed, none have been incorporated into current design standards. Foundations must be uniquely designed for each wind farm due to extreme dependence on site characteristics. The uncertainty in soil conditions as well as wind and wave loading is currently treated with a deterministic design procedure, though standards leave the door open for engineers to use a probability-based approach. This thesis uses probabilistic methods to examine the reliability of OWT pile foundations. A static two-dimensional analysis in MATLAB includes the nonlinearity of p-y soil spring stiffness, variation in soil properties, sensitivity to pile design parameters and loading conditions. Results are concluded with a natural frequency analysis.

Offshore wind has proved to be one of the most reliable and clean energy sources over the last few years. The industry has experienced a significant growth, with an increase of 101% only in 2017 compared to 2016. This raises the importance of the need for more secure power supply systems, which can be used for controlling the offshore farms during disconnections from the main grid. Nowadays, diesel generators are being used to feed auxiliary services of the offshore wind turbines in situations of emergency. However, as the marine renewable energy industry evolves, tidal energy parks have the potential to replace diesel generators and provide a more sustainable and eco-friendly solution for a long-term auxiliary power system. Moreover, they have the potential to produce extra power, which can be either stored for future use or linked directly to distribution. This report demonstrates a technical, financial and environmental assessment of a potential tidal park within an offshore wind park. Comparison with alternative sources for emergency power supply is also performed. Three alternative locations with high wind speeds and large tidal resource around the UK coast and four different groups of tidal devices are evaluated and compared for the implementation of this solution with the use of ArcGIS maps and other accessible marine data. The Aberdeen wind farm and the tidal kites are selected for further investigation and cost analysis. Seven tidal kites with average power 700 kW and rated power 3.5 MW can provide adequate power to the offshore wind farm for three months without grid connection, whereas they can also provide excess of energy on daily basis when grid disconnection does not occur. The total cost for the project would be approximately 301.6 MSEK. Due to the current renewable energy market, the project is not feasible without high investment risks. However, this study should be evaluated again in the near future when the cost of the tidal device will be further decreased. / Havsbaserad vind har visat sig vara en av de mest tillförlitliga och rena energikällorna under senare år. Inom denna industri har en betydande tillväxt skett, med en ökning med 101% år 2017 jämfört med 2016. Detta relaterar till behovet av säkra elförsörjningssystem, som kan användas för att styra havsbaserade vindraftverksparker under urkoppling från huvudnätet. Numera används dieselgeneratorer som reservkälla till havsvindkraftverk i nödsituationer. Men när den marina förnybara energiindustrin utvecklas, har tidvattenkraftverk potential att ersätta dieselgeneratorer och ge ett mer hållbar och miljövänlig långtidslösning. Dessutom har de potential att producera extra el, som antingen kan lagras för framtida användning eller kopplas direkt till distributionsnätet. Denna rapport erbjuder en teknisk, finansiell och miljömässig bedömning av en potentiell tidvattenkraftverkspark kopplad till en havsvindpark. Jämförelse med alternativa källor för strömförsörjning genomförs också. Tre alternativa platser med hög vindstyrka och stora tidvattenresurser längs Storbritanniens kust och fyra olika grupper av tidvattenanordningar utvärderas och jämförs med hjälp av kartor och andra tillgängliga marina data. Aberdeen vindkraftpark och tidvattendrakar väljs för ytterligare undersökning och kostnadsanalys. Sju tidvattendrakar med genomsnittlig effekt på 700 kW och nominell effekt 3,5 MW kan ge tillräckligt med el till havsvindkraftverk i tre månader utan nätförbindelse, medan de också kan ge överflöd av energi dagligen när strömavbrott inte förekommer. Den totala kostnaden för projektet skulle vara cirka 301,6 MSEK. På grund av läget idag på elmarknaden för förnybar energi, är projektet inte genomförbart utan höga investeringsrisker. Men den här studien bör utvärderas igen inom en snar framtid när kostnaden för tidvattenanordningen har minskat.