No description available.

No description available.

The V-type vertical axis wind turbine (V-VAWT) is of simple design and construction, has a low aerodynamic efficiency, yet its originators consider that it will be a cost effective configuration in electricity generation applications. However, the quality and reliability of its power output must be ensured; this necessarily requires continual control of rotor speed and power. The initial V-VAWT investigations of Sharpe and Taylor, and methods of wind turbine control are reviewed. Partial-span pitch angle variation is considered the most promising option, and the systematic investigation of this control method in V-VAWT applications is reported. This work includes the design, construction and performance testing of a small V-VAWT with pitching blade tips. The tests showed that rotor power can be regulated with small blade tip areas, however, correlation between the measured and theoretical results was not good. Wind tunnel test were undertaken to determine the characteristics of the NACA0025 aerofoil used for the model blades. Performance predictions using this data showed better correlation between experimental and- theoretical results. This has allowed the theoretical model to be used with confidence for predicting the performance of larger V-VAWTs with partial-span pitch control. A theoretical model of the dynamic behaviour of a V-VAWT generator integrated with an electricity supply network has been developed and embodied in the computer program DYNVAWT. This program has allowed the dynamic behaviour of a 5kW sized V-VAWT to be simulated, and an active control strategy developed. The simulation studies show that active partial-span pitch control ensures the quality and reliability of the electricity supply can be maintained even when the V-VAWT is operating in turbulent wind conditions.

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The release of carbon dioxide from the burning of fossil fuels for energy is thought to be one of the main contributors to increasing greenhouse gas concentrations in the atmosphere. This increase is reported to be causing irreversible changes to the earth’s climate, giving rise to temperature increases and other consequent alterations in weather patterns. Amid growing concern about climate change and its impact on the world, targets have been set through agreements such as the Kyoto Protocol and via European Union and government legislation to force countries to work towards decreasing their greenhouse gas emissions. Increasing the contribution that renewable sources make to energy production is a major part of most countries’ strategies to meet these targets. The UK has arguably the greatest potential for wind power generation in Europe and the government is seeking to build upon this strength by exploiting the resource further. The liberalised electricity market infers a requirement for private investment in order to develop the wind portfolio and this in turn requires financial and economic feasibility. Given the changes in weather patterns that are projected to occur over the course of the coming century, the possibility that this could change the UK’s wind resource, and hence the financial viability of wind power developments, must be addressed. Other aspects of how changes in the wind resource could impact on the operation of the fragmented electricity system ought also to be considered in this context. This thesis attempts to understand how the current generation of climate models project surface wind climate to change, and seeks to make the model information relevant at a site level by using statistical and physical modelling techniques. The projected changes indicated by the models are small, and it has been assessed that potential impacts on the electricity system, from project feasibility to the potential for inclusion of wind in the generation mix, will be limited.

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As the demand for safe and clean electricity increases, the New Zealand wind energy industry seems poised to expand. Many generating companies have projects in the planning stage and there are likely to be many more potential sites yet to be identified. Reliable wind climate predictions over a wide area and for different heights above grounds are often vital to determine the viability of wind farm projects. This study investigates the use of meteorological mesoscale models to determine the wind and energy resource, particularly in areas of complex terrain. Complex terrain environments are likely to be typical of where New Zealand wind energy developments will take place. Using the prognostic mesoscale meteorological model TAPM (The Air Pollution Model), regions of relatively high mean wind speed were identified for a number of regions, including Banks Peninsula and parts of Canterbury and Otago. The simulations were conducted for a one-year period (2001) and at different heights above ground level. Depending on the resolution of the model calculations, speed-up effects from the forcing of some topographic features were accounted for by this model. Where the modelling was considered reliable, hourly wind data were obtained from grid points within the inner grid and used as input data for the industry-standard wind energy assessment model WAsP (The Wind Atlas Analysis and Application Program). As WAsP is able to account for detailed topography and surface roughness features, wind and energy predictions at a specific site or over a wider area surrounding the site were made. Limitations of both models in complex terrain were identified. These limitations were due to a number of factors, including the grid spacing used for mesoscale model calculations, the complexity of the terrain, and difficulties in modelling some regional scale airflow regimes. Being aware of when and where model limitations are likely to occur is important in being able to overcome and account for them.

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Incorporation of wind energy into the electricity generation system requires a detailed analysis of wind speed in order to minimize system balancing cost and avoid a significant mismatch between supply and demand. Power generation and consumption in the electricity networks have to be balanced every minute, therefore it is necessary to study wind speed on a one-minute time scale. In this thesis, we examine the statistical characteristics of one-minute average values of wind speed. One-minute wind speed is available from a single site in Great Britain while there are records of ten-minute wind speed available. We apply a modified Gibbs sampling algorithm to generate one-minute wind speed required for optimization modelling from the available ten-minute wind speed. System balancing costs are estimated through optimization modelling of the short-term electricity generation with wind energy contributing to the total supply. Two main drivers of additional system cost caused by wind energy are variability and unpredictability of one-minute wind speed. Further, a linear mathematical optimization model for a problem of short-term electricity generation is presented to calculate an additional balancing cost that appears as a result of wind energy variability. It is then shown that this additional balancing cost can be estimated using the statistical characteristics of wind energy present in the system. The unpredictable characteristic of wind speed is analysed with the techniques of stochastic programming. Uncertainty of the expected wind speed is represented through scenario trees and stochastic linear optimization models are used to calculate the extra cost due to uncertainty. Alternative optimization models are compared by calculating the additional balancing cost and the extent of imbalance between power generation and consumption in the system.

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