Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 76-79).

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 95-97).

Thesis (doctoral)--Uppsala University, 1990. / Summary in English. Leaf with thesis statement inserted. Includes bibliographical references (p. 292-300).

Thesis (M.S.)--San Jose State University, 2005. / Includes abstract. Includes bibliographical references (leaves 70-76) ProQuest ; Subscription required for access to full text. Also available via the World Wide Web ;

Wind energy, being an indirect form of solar energy would initially seem a very promising form of energy. Unfortunately, it suffers from the problem of dilution. Wind turbine designers naturally try to compensate for this by increasing the size of the rotor to capture more of the kinetic energy of the wind. A major constraint in conventional wind turbine design is the reduction in rotational speed as the size of the rotor is increased. This means expensive gear boxes are unavoidable. The rotor also becomes considerably more complicated in design and heavier as the size increases, to mitigate working stresses. Flow concentrators have been investigated in an attempt to alleviate wind turbine design problems, but flow concentrators usually incur the expense of high structural weight and size. The Helical Vortex Wind Concentrator (HVWC) is a recent addition to the list of flow concentrator types and its economic potential is, as yet unknown. The principle of the HVWC has been demonstrated in a series of wind tunnel tests. The wind tunnel tests involved a direct comparison between the performance of a wind turbine with and without an HVWC attached. During these tests a definite increase in power out was observed when the concentrator was attached to the wind turbine. Previous to these successful wind tunnel tests, other wind tunnel and field tests had been conducted on less successful designs. These other tests were important in the development of the current theory and design or the HVWC. Future research will need to investigate both physical and economic limitations of this type of wind concentrator.

This thesis describes work on the statistics of the temporal and spatial variation of wind power in the UK, and the consequences of these variations for the use of wind generation of electricity both by the Central Electricity Generating Board (CEGB) and more generally. The statistical work is based on the use of spectral analysis, and cross correlation analysis of wind power time series estimated from Meteorological Office records of hourly mean wind speeds at 30 UK recording sites over a period of 9 years. Estimates of wind power capacity credit and wind operating reserve requirements as functions of wind power penetration into the conventional grid, geographical separation of wind power plant and specific power of wind turbines are made. An important result from this work, is that cross correlation coefficients of changes in wind power for lead times of a few hours are dominated by diurnal fluctuations in wind speed. These in turn are highly variable in both magnitude and sign, depending on among other things measurement height. The dominance of diurnal fluctuations can be seen more clearly in the coherence function plots for wind power at pairs of sites. The most important consequence of the resultant uncertainty in cross correlation coefficients will be on estimates of wind operating reserve requirements, which to a first approximation are linearly dependent on these coefficients.

Circulation control aerofoils potentially offer an additional means of load and power control for horizontal axis wind turbines by virtue of their rapid response time. Their suitability for these tasks has been assessed with respect to the power which they absorb, their interaction with aerofoils used on modern wind turbines, the infrastructure or hardware which they require and the degree to which they can affect the loads experienced by the turbine blades and other major components. It has been determined that the type of circulation control aerofoil most suited to use on wind turbine blades are those of the jet flap type and it has been realised that an ability to shed, as well as increase loads is advantageous in this application. To this end the behaviour of both negatively and positively deflected jets have been investigated with a two-dimensional computational fluid dynamics code, validated in the course of this work for such modelling. Particular emphasis has been placed on minimising the input power requirements of the circulation control aerofoils and in proposing an overall system that has the required level of robustness and reliability. A 2MW turbine has been modelled with a blade element momentum theory code in order to compare performance with and without circulation control aerofoils. These initial results show that there may be some positive benefits to be gained, but that the energy demands of the system place a hard limit on the degree to which circulation control aerofoils can determine the forces experienced by the turbine.

Wireless sensor networks and portable electronic devices, such as mobile phones, media players, digital cameras and iPods, require local electric power supplies. Although these devices are operational all the time, they consume just a few milli-or micro-watts. This means energy harvesting from the environment is an attractive option for powering these devices. Mechanical energy harvesters can use electromagnet, electrostatic or piezoelectric approaches. Of these, electrostatic devices are found to be the most suitable approach for harvesting mechanical energy since they are compact, sensitive to low level mechanical energy, easier to integrate in small scale systems, not requiring smart materials, simple to fabricate, inexpensive and simply structured using less circuitry. Most of electrostatic harvesters proposed in previous studies use mechanical vibration. However, only a few studies have investigated harvesting rotational mechanical energy. The objective of this thesis is to investigate the possibility of harvesting rotational mechanical energy from wind using the electrostatic approach. The proposal involves capturing wind energy using a micro wind turbine then converting it into usable electrical energy. This work first considers general design considerations and the design procedure that must be followed to construct a suitable electrostatic based wind energy harvester. Second, it describes the operating principles of various parts needed to design a novel efficient electrostatic harvesting system. The new harvester consists of a micro wind turbine, a gearbox, a multi-pole variable capacitor or capacitor array, an LC to LC energy transfer circuit, a capacitance sensing system and a microcontroller. The harvesting process has three main steps. First, wind energy is captured and converted into mechanical power using the micro wind turbine. Second, mechanical power is converted into electrical power using the variable capacitor in three phases: pre-charge, harvest and reset. Third, the electrical energy is processed and stored in a Lithium ion battery. The proposed harvester was simulated using Matlab/Simulink to study energy transfer throughout the three energy harvesting phases. Energy analysis was then carried out to study the effect of varying the structure of the multi-pole capacitor on the amount of harvested energy. Results from the simulation for capacitance variation from 2.5 nF to 0.6 nF indicated that an eight-pole variable capacitor can produce 29.43 μJ/sec at a wind speed of 10 m/sec, while a capacitor array of the same capacitance variation with 10 capacitors in the array can produce 295 μJ/sec at a wind speed of 10 m/sec. The results of experiments were carried out to test wind harvesting using a two-pole capacitor proved that the proposed harvester is capable of powering an RF transmitter to transmit wind speed information wirelessly.

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No description available.