<p>Wind tunnel studies of the wake behind model wind turbines with one, two and three blades have been made in order to get a better understanding of wake development as well as the possibility to predict the power output from downstream turbines working in the wake of an upstream one. Both two-component hot-wire anemometry and particle image velocimetry (PIV) have been used to map the flow field downstream as well as upstream the turbine. All three velocity components were measured both for the turbine rotor normal to the oncoming flow as well as with the turbine inclined to the free stream direction (the yaw angle was varied from 0 to 30 degrees). The measurements showed, as expected, a wake rotation in the opposite direction to that of the turbine. A yawed turbine is found to clearly deflect the wake flow to the side showing the potential of controlling the wake position by yawing the turbine. The power output of a yawed turbine was found to depend strongly on the rotor. The possibility to use active wake control by yawing an upstream turbine was evaluated and was shown to have a potential to increase the power output significantly for certain configurations. An unexpected feature of the flow was that spectra from the time signals showed the appearance of a low frequency fluctuation both in the wake and in the flow outside. This fluctuation was found both with and without free stream turbulence and also with a yawed turbine. The non-dimensional frequency (Strouhal number) was independent of the freestream velocity and turbulence level but increases with the yaw angle. However the low frequency fluctuations were only observed when the tip speed ratio was high. Porous discs have been used to compare the meandering frequencies and the cause in wind turbines seems to be related to the blade rotational frequency. It is hypothesized that the observed meandering of wakes in field measurements is due to this shedding.</p>

An energy harvesting device driven by aeroelastic vibration with self-sustained pitching and heaving using an induction based power take off mechanism has been designed and tested for performance under various operating conditions. From the data collected the results show that the device achieved a maximum power output of 48.3 mW and a maximum efficiency of 2.26% at a dimensionless frequency of 0.143. For all airfoils tested the device was shown to be self-starting above 3 m/s. A qualitative description relating to the performance of the device considering dynamic stall and the flow conditions at optimal dimensionless frequency has been proposed and related to previous work. Performance for angles off the wind up to 22 degrees and was observed to have no reduction in power output due to the change in angle to the wind. The device has shown evidence of having a self-governing capability, tending to decrease its power output for heavy windpspeeds, a thorough examination of this capability is recommended for future work. / Graduate / 0548 / 0544 / opirquet@uvic.ca

This thesis analyzes the feasibility of having an integrated wind and solar farm to optimize the use of land resources and capital investment by evaluating the effect that wind turbine shadows have on the area surrounding them. Two methods are used to predict shadow impact. The first method is based on the traditional textbook “Clear Sky” equations, which have maximum sensitivity to shadows because the method considers every day to be a perfect day. The second method uses measured global-horizontal and diffuse-horizontal solar radiation in units of W/m2, which take into account the true variations of daily conditions. The calculations are performed for 1 square meter surfaces, over different assumed areas of a wind power plant, for every second of the day. For purposes of shadow calculations, the tip-top height (i.e., tower height plus blade length) is used. All calculations are performed with the specifications of a GE 1.5 MW wind turbine, which is the most commonly used wind turbine in USA. / text

This narrative chronicles the development of the utility scale wind industry in Texas from the perspective of the people who made it possible. It also looks ahead at the challenges facing the most mature green power sector in the United States. / text

Wind is one of the most promising resources in the renewable energy portfolio. Still, the cost of electrical power produced by small wind turbines impedes the use of this technology, which can otherwise provide power to millions of homes in rural regions worldwide. To encourage their use, small wind turbines must convert wind energy more effectively while avoiding increased equipment costs. A variable ratio gearbox (VRG) can provide this capability to the simple low-cost fixed-speed wind turbine through discrete operating speeds. The VRG concept is based upon mature technology taken from the automotive industry and is characterized by low cost and high reliability. A 100 kW model characterizes the benefits of integrating a VRG into a fixed-speed stall-regulated wind turbine system. Simulation results suggest it improves the efficiency of the fixed-speed turbine in the partial-load region and has the ability to limit power in the full-load region where pitch control is often used. To maximize electrical production, mechanical braking is applied during the normal operation of the wind turbine. A strategy is used to select gear ratios that produce torque slightly above the maximum amount the generator can accept while simultaneously applying the mechanical brake, so that full-load production may be realized over greater ranges of the wind speed. Dynamic programming is used to establish the VRG ratios and an optimal control design. This optimization strategy maximizes the energy production while insuring that the brake pads maintain a predetermined service life. In the final step of the research, a decision-making algorithm is developed to find the gears that emulate the ratios found in the optimal control design. The objective is to match the energy level as closely as possible, minimize the mass of the gears, and insure that tooth failure does not occur over the design life of the VRG. Recorded wind data of various wind classes is used to quantify the benefit of using the VRG. The results suggest that an optimized VRG design can increase wind energy production by roughly 10% at all of the sites in the study. / text

D. Tech. Mechanical Engineering, Mechatronics and Industrial Design / South Africa has limited reserve electricity resources and many parts of the country have limited access to electricity. Electricity production capacity is at maximum and almost each Giga watt is accounted for. Predictions suggest South Africa would have a serious electricity allocation problem in the very near future and current rolling blackout in many of our cities can attest to the looming problem. The energy crisis in South Africa has highlighted the need to increase electricity generation capacity and to search for alternative energy sources. Solar chimney plants could form part of the solution in the near future in South Africa to create additional power. This study aimed to develop a wind generation system in areas where wind is absent. A solar chimney power plant is expected to provide remote areas in South Africa with electric power, or to complement the current electricity grid. Solar energy and the psychometric state of the air are important to encourage the full development of a solar chimney power plant for the thermal and electrical production of energy for various uses. Research within the South African context and particularly on increasing the effectiveness of the solar chimney power plant technology is lacking; as such this study proposes the development of a solar chimney plant and associated technology to ensure the effectiveness of this plant.

D. Tech. Electrical Engineering. / Aims to investigate wind resources of a given site and develop a mathematical model that is suited for the selection of an appropriate wind turbine for the site. Develop a mathematical model for a wind energy conversion system (WECS) and its use in studying the behaviour of wind generators in response to the electrical network disturbance. The impact of wind power on the transient stability of a power system and the integration impact of intermittent wind power on the small signal stability of a power system.

M. Tech. Electrical Engineering. / One of the main issues in the integration of large wind power generation into the electric power networks is the voltage drop at the point of common connection (PCC) and the increase in power losses as well. This work deals with the optimization of the reactive power control in a power system with integration of a wind farm with the aim of minimizing the total active power losses and improving the load voltage profiles

Fossil fuel is presently a major source for electricity production, but it contributes significantly to Green House Gas emissions. Wind is a promising alternative, and can potentially become a major power resource in future power systems. Wind power installations are growing significantly for producing clean energy in electric power systems. As the wind penetration continues to increase to relatively high levels, it can significantly affect the overall performance and reliability of the power system. Hence, it becomes very important to accurately model the behaviour of wind, its interaction with conventional sources and also with other wind resources connected to the power system in order to conduct a realistic assessment of system reliability and benefits from wind energy utilization. When the wind penetration levels are low, all the wind energy generated is utilized to serve the load. However, at higher wind penetration levels, wind energy is spilled due to limitations in the operating reserve or ramping capability of the scheduled generating units. The system reliability and the wind energy benefits are reduced as the wind energy spillage increases due to wind curtailment. Hence, accurate wind models should be researched and developed to include wind energy curtailment in the reliability modelling, considering factors such as the system load level, priority loading order of the generating unit and response rates of the generating units. Researchers have not incorporated these factors in wind power modelling and in the adequacy evaluation of wind integrated power systems. A new analytical technique is developed in the subsequent chapters to carry out a comprehensive wind absorption capability evaluation of the power system, and also to incorporate this characteristic in reliability modelling of the system. Wind curtailments can take place not only due to generation constraints, but also due to transmission line constraints depending on the capacity and location of the wind energy resource in the power system, and the power transfer capacity of the transmission lines connected to the wind farm bus. Therefore, reliability modelling of the power system considering wind curtailments due to both generation and transmission constraints should be carried out to assess the impact of wind farms on bulk system reliability and the wind energy benefits. Wind curtailment is incorporated in the composite power system reliability evaluation by modelling the wind resource both as generation and as negative load. The techniques can be utilized to conduct system adequacy and wind energy benefit assessment both at the capacity planning stages and composite generation/transmission planning stages, incorporating wind power curtailment due to generating unit response limitations. As the wind penetration in a power system increases, the wind farms connected to the system are distributed at different geographical locations. Both analytical and Monte Carlo Simulation based techniques have previously been used by the research group at the University of Saskatchewan to include the cross correlation between the wind characteristics of different wind farms in the wind modelling for reliability evaluation of power systems. However, the combined effect of wind diversity and wind curtailments due to both transmission and generation constraints on the system reliability and wind energy benefit assessment has not been considered. The techniques developed for system adequacy and wind energy benefit assessment considering wind curtailment due to generation and transmission constraints are further modified and presented in this thesis to include wind diversity in the analysis. The developed techniques for adequacy evaluation of wind integrated power systems considering wind power curtailment and diversity should be extremely useful for system planning engineers and policy makers as wind power penetration in power systems continues to increase throughout the world.

Renewable energy sources have become very popular in the last years in electricity generation thanks to the technological developments, the increase in the price of fossil fuels and the environmental concerns. These factors have also prompted Turkey to utilize her very rich renewable energy sources to meet the demand increasing around 7% annually. In this study, solar and wind energy potential of Turkey is analyzed in terms of its economics to find out whether these sources are real alternatives to fossil fuels in electricity generation. Before this analysis, wind and solar energy technologies and costs and wind and solar energy potential of Turkey are discussed. Then, models are set up for five technologies which are onshore wind, offshore wind, solar PV, solar trough and solar tower technologies models to calculate cash flows which are used to calculate payback, NPV, IRR, LCE and shut-down price to conduct economic analysis. In addition to base case scenario, uncertainty analysis is done for the most promising technologies which are onshore wind and solar tower technologies by evaluating NPV and LCE under uncertain environment. The main finding of these analyses is that only onshore wind projects are attractive in Turkey; none of other technologies is attractive. However, with a minor increase in the regulated price for solar thermal electricity, tower plant projects will also be attractive. / text