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This thesis describes four novel superconducting machine concepts, in the pursuit of finding a suitable design for large offshore wind turbines. The designs should be reliable, modular and light-weight. The main novelty of the topologies reside in using a single loop shaped stationary superconducting field winding, which eliminates the rotating transfer couplers and electric brushes or brushless exciters. Furthermore, the electromagnetic forces in the superconducting wire are also eliminated, which simplifies the design and manufacturing of the cryostat and the support structure. Among the four topologies presented, the claw pole type machine is the most promising one. The rotor of the machine composes of claw-poles made from laminated electrical sheets, the superconducting field winding and the armature winding are stationary. The machine is analysed using 3D FEA simulations and a small linear machine prototype is manufactured to verify the simulations. For large scale applications, a double-sided claw pole machine is proposed, which has balanced magnetic attraction forces in the rotor. The machine has a modular cryostat structure, which increases the availability of the machine. Thus, even if a fault occurs in the cryocoolers or in the armature coils, the rest of the machine can operate at partial load until the maintenance is performed. Moreover, it is much easier to replace the faulty parts, as full disassemble of the machine is not required, and a small on-site crane can be used. As a result, it offers operational advantages over the existing superconducting topologies. A 10 MW, 10 rpm generator design is presented, which has a diameter of 6.6 m and an axial length of 1.4 m. The total active mass of the generator is 58 tonnes, and the structural mass is 126 tonnes, which gives a total mass of 184 tonnes. There are four independent cryostats and two independent armature windings in the machine to improve modularity. The biggest advantage of the design is the significantly less superconducting wire usage compared to any other designs; 10 MW machine just needs 15 km of MgB2 wire at 30 K. Thus, it is believed that the proposed topology is a very cost effective and suitable candidate for a successful entry to the wind turbine market.

Floating wind turbines (FWTs) are considered a new lease of opportunity for sustaining growth from offshore wind energy. In recent years, several new concepts have emerged, with only a few making it to demonstration or pre-commercialisation stages. Amongst these, the spar-buoy based FWT has been extensively researched concept with efforts to optimise the dynamic response and reduce the costs at acceptable levels of performance. Yet, there exist notable lapses in understanding of these systems due to lack of established design standards, operational experience, inaccurate modelling and inconsistent reporting that hamper the design process. Previous studies on spar-buoy FWTs have shown inconsistencies in reporting hydrodynamic response and adopted simplified mooring line models that have failed to capture the coupled hydrodynamic behaviour accurately. At the same time, published information on drive-trains for FWTs is scarce and limited to geared systems that suffer from reliability issues. This research was aimed at filling the knowledge gaps with regard to hydrodynamic modelling and drive-train research for the spar-buoy FWT. The research proceeds in three parts, beginning with numerical modelling and experimental testing of a stepped spar-buoy FWT. A 1:100 scale model was constructed and tested in the University of Edinburgh’s curved wave tank for various regular and irregular sea states. The motion responses were recorded at its centre of mass and nacelle locations. The same motions were also simulated numerically using finite element method based software, OrcaFlex for identical wave conditions. The hydrodynamic responses were evaluated as Response Amplitude Operator (RAO) and compared with numerical simulations. The results showed very good agreement and the numerical model was found to better capture the non-linearities from mooring lines. A new design parameter, Nacelle Magnification Factor, was introduced to quantify coupled behaviour of the system. This could potentially encourage a new design approach to optimising floating wind turbine systems for a given hub height. The second part of the research was initiated by identification of special design considerations for drive-trains to be successfully integrated into FWTs. A comparative assessment of current state of the art showed good potential for directdrive permanent magnet synchronous generators (PMSG). A radial flux topology of the direct-drive PMSG was further examined to verify its suitability to FWT. The generator design was qualified based on its structural integrity and ability to ensure minimal overall impact. The results showed that limiting the generator weight without compromising air-gap tolerances or tower-foundation upgrades was the biggest challenge. Further research was required to verify the dynamic response and component loading to be at an acceptable level. The concluding part of research investigated the dynamic behaviour of the directdrive generator and the various processes that controlled its performance in a FWT. For this purpose, a fully coupled aero-hydro-servo-elastic model of direct-drive FWT was developed. This exercise yet again highlighted the weight challenge imposed by the direct-drive system entailing extra investment on structure. The drive-train dynamics were analysed using a linear combination of multi-body simulation tools namely HAWC2 and SIMPACK. Shaft misalignment, its effect on unbalanced magnetic pull and the main bearing loads were examined. The responses were found to be within acceptable limits and the FWT system does not appreciably alter the dynamics of a direct-drive generator. Any extra investment on the structure is expected to be outweighed by the superior performance and reliability with the direct-drive generator. In summary, this research proposes new solutions to increase the general understanding of hydrodynamics of FWTs and encourages the implementation of direct-drive generators for FWTs. It is believed that the solutions proposed through this research can potentially help address the design challenges of FWTs.

Transverse Flux Machines (TFM) present some interesting problems to the machine designer, electro-magnetically and mechanically. They offer the lure of an extremely high specific output, but only, apparently, at the price of intricate three dimensional flux paths, a complicated construction and a low power factor. The research covered by this thesis was concerned with the study, development and improvement of these machines with a view to reducing the detracting aspects of the marque whilst accentuating its advantages. Extensive three dimensional finite element analysis into a wide range of TFM topologies, was coupled with practical investigations into three prototype TFMs constructed at Newcastle University. The result of this work was an improved TFM topology with comparatively good power factor, a simple single sided geometry and a very high specific output.

A trade study is carried out for the design of electric propulsion based lunar robotic precursor missions. The focus is to understand the relationships between payload mass delivered, electric propulsion power, and trip time. The results are compared against a baseline system using chemical propulsion with LOX/H2. The major differences between the chemical propulsion based and electric propulsion based systems are presented in terms of the payload mass and trip time. It is shown that solar electric propulsion offers significant advantage over chemical propulsion in delivering non-time critical payloads to lunar orbit. / Master of Science

The key focus of this research was to investigate the bearing options most suited to operation in a novel direct drive linear generator. This was done through bearing comparisons, modelling and testing. It is fundamental that the linear generator is designed to suit the marine environment. Key design constraints include reliability, survivability, maintenance intervals and cost. Resilient mechanical structural components, such as bearings, will prolong the time a device can operate without maintenance hence prolonging the operating period. Effective lifespan predictions for bearings will feed into the structural design of the generator which forms part of an overall objective to combine each generator design stage into one integrated design process. This promises to provide a cost effective, light weight generator design. This thesis covers the initial investigations into effective, long life and low-wear bearings to meet the operating demands of WEC. It includes an assessment of conventional bearing technology, designs of water-fed hydrostatic bearings and testing of novel polymer bearings. The development of an experimental test rig from a prototype linear generator is described. The rig was built in order to validate and fully explore the potential of self-lubricating, submersible polymer bearings with the ultimate aim of identifying wear constants and frictional properties of the bearings in the low-speed, mid to high-load, oscillating operation of a WEC in order to more accurately predict a bearing lifespan. The outcome of this research served to underpin the need for the design of application specific bearing systems to be based on empirically determined data and observations from test data taken from application specific tests. For inclusion in the design of these linear generators, sizing a bearing requires knowledge of the electrical loading in addition to the expected operating conditions of a WEC. Choosing bearing materials and hence lubricant regimes is dependant on the thermal operating characteristics. Then bearing knowledge in terms of size, load capacity and lifespan can be put directly into the structural model. This iterative process of design can then be merged into a fully integrated generator design tool hence this research was part of the development of an integrated design tool for direct drive generators.

This thesis focuses on permanent magnet "direct drive" electrical generators for wind turbines with large power output. A variety of such generator topologies is reviewed, tested and optimised in an attempt to increase their potential as commercial concepts for the wind industry. Direct drive electrical generators offer a reliable alternative to gearbox drivetrains. This novel technology reduces energy loses thus allowing more energy to be yield from the wind and decreases the maintenance cost at the same time. A fundamental issue for these generators is their large size which makes them difficult to manufacture, transport and assembly. A number of structural designs have been suggested in the literature in an attempt to minimise this attribute. A set of design tools are set out in an attempt to investigate the structural stiffness of the different permanent magnet direct drive generator topologies against a number of structural stresses that apply to such wind turbine energy converters. Optimisation techniques, both analytical and structural, are also developed for minimising the total mass of a variety of "directly driven" machines with power output of 5MW or greater. Conventional and promising generator designs are modelled and optimised with the use of these optimisation techniques. The topologies under examination are then compared in terms of structural mass, stiffness and cost. As the number of wind turbine manufactures who adopt the direct drive concept increases, it is important to outline the unique characteristics of the different topologies and increase their manufacturing potential. Discussions and conclusions will provide an indication of the design solutions that could help decrease the mass and cost of such machines.

<p>In this thesis, a concept for a modular assembly direct drive permanent magnetgenerator is presented. The maximum forces that act on the different parts of thegenerator during normal operation have been calculated and used in solid mechanicsimulations in SolidWorks. The result is a rough first draft of a generator designwhere the stator has been divided into five modules and the rotor into six modules.This division is done in order to avoid symmetries in the generator that could lead toproblems with self-oscillation.The modulization of the stator brings about certain difficulties, both for the magneticcircuit and for the winding scheme. Different solutions for optimization of themagnetic circuit are analyzed from both a physical and a construction technicalperspective. A winding scheme is produced and the winding process tested in awinding dummy produced according to the conceptual generator design.</p>

In this thesis, a concept for a modular assembly direct drive permanent magnetgenerator is presented. The maximum forces that act on the different parts of thegenerator during normal operation have been calculated and used in solid mechanicsimulations in SolidWorks. The result is a rough first draft of a generator designwhere the stator has been divided into five modules and the rotor into six modules.This division is done in order to avoid symmetries in the generator that could lead toproblems with self-oscillation.The modulization of the stator brings about certain difficulties, both for the magneticcircuit and for the winding scheme. Different solutions for optimization of themagnetic circuit are analyzed from both a physical and a construction technicalperspective. A winding scheme is produced and the winding process tested in awinding dummy produced according to the conceptual generator design.