published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Wind power generation has experienced an explosive growth worldwide. It is a promising renewable energy source to countries that are short of fossil fuels, e.g. China. While wind power is a distinctive direction to go for, it is still necessary to examine the rationale behind such investing mania, and this thesis analyzes the issue by collectively investment modeling. For investment analysis, it is necessary to first identify the relevant market background before inferring to any analytical model. Chapter 2 identifies a number of wind power investment scenarios in accordance to modern electricity market regime, primarily American and European structures. Among them, two main scenarios are investigated and modeled subsequently: fixed tariff wind power project invested by independent power producer and wind power project undertaken by utility. It has to be emphasized that different market scenarios would lead to different modeling methodologies for best representing the reality. Wind power is intermittent and uncertain. One way to describe the probabilistic energy production is by statistical characterization of wind power in a period of time. Chapter 3 presents a standalone analytical model of the wind power probability distribution and its higher order statistics. Large-scale deployment of wind power would influence power system in unprecedented ways. High penetration wind power poses a need of refinement to existing methodologies on production costing and reliability evaluation. The applications of the probabilistic wind power model to these topics are outlined in this chapter. In Chapter 4, investment of fixed tariff wind power project is analyzed. Operation of wind farm is very passive and as long as wind keeps blowing, such wind power investment has minimal risk in annual revenue. The low-risk profile facilitates debt financing. This leads to the attempt to manipulate the project capital structure to maximize the project levered value. Yet the default probability is raised and associated with a subjective value of default probability there is a value-at-risk debt level. I therefore propose an optimization formulation to maximize the wind power project valuation with debt as decision variable subject to the value-at-risk debt constraint. Apart from independent wind power producers, many policy and market factors driving wind power development are actually put on the utility side, e.g. Renewable Portfolio Standard (Renewable Energy Target) in U.S. (Europe) and Green Power Programs. It implies that utility has to have wind power (or other renewable) capacity ready by a certain date. In practice, utility may take action earlier if conditions are favorable or optimal. The conditions considered here are fossil fuel prices or in more general setting, electricity contract prices. Define the total fuel cost saving from conventional units as the benefit of wind power. If fuel prices are high enough, substituting load demand by wind energy is profitable, vice versa. The investment decision is analogous to premature exercising of an American option, in which the wind power project is modeled as real option. Chapter 5 offers detailed formulation of this idea. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This paper investigates the concept of an isolated small wind power system based on a three-phase generator and a direct ac-to-ac conversion. The ac-to-ac conversion is performed by a matrix converter and thus removing the need of a large smoothing capacitor in the typical rectifier-inverter solution. The paper is briefly presenting the operation for a particular topology of a three-phase to single-phase matrix converter. The control of this conversion ensures system’s frequency and voltage stability. Simulation results and practical results are presented to validate the frequency and voltage regulation of the isolated power system.

No description available.

Thesis (Ph.D.)--University of California, Berkeley, 2005. / Adviser: Daniel M. Kammen. Includes bibliographical references.

Thesis (M.S.)--University of Colorado, 1998. / Includes bibliographical references (leaves 45-46). Also available full text via Internet in .pdf format. Adobe Acrobat Reader required.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 49-50). Also available on the World Wide Web.

Cross flow wind turbines are not unique. The performance of Savonius and Darrieus turbines is well documented. Both share the advantage of being able to accept fluid flow from any direction. The Savonius is drag based and hence has poor power output while the Darrieus is lift based. Due to the fact that the Darrieus has fixed blades the fluid flow through the rotor does not result in optimal lift being generated at all points in the rotation circle. A drawback of the Darrieus system is that it has to operate at a high tip-to wind-speed ratio to obtain reasonable performance with the fixed blades. Deviation from a small optimal range of tip speed ratios results in poor performance. The Darrieus also has poor starting torque. The research conducted in this project focused on overcoming the shortcomings of other turbines and developing an effective cross flow turbine capable of good performance. A number of different concepts were experimented with, however all were based on a symmetrical aerofoil presented to the actual relative airflow at an angle that would produce the highest lift force at all times. The lift force was then utilized to generate movement and to do work on an electrical generator. All concepts contemplated were researched to ascertain their appropriateness for the intended application. During development of the final experimental platform and after lodging of a provisional patent (RSA 2007/00927) it was ascertained that the design shared some similarities with an American patent 5503525 dated 28/4/1994. This patent employed complex electronic sensing and control equipment for control of blade angle. This was thought to be overly complex and costly, particularly for small scale wind energy generation applications and a simpler mechanical solution was sought in the design of the final experimental platform used in this project. The design of the mechanical control system was refined in an attempt to make it simpler, more durable and employ the least number of moving parts. Literature studies and patent searches conducted, suggested that the mechanical control system as developed for the final experimental platform was unique. The enormous variation in the power available from the wind at the different wind speeds likely to be encountered by the device necessitated some means of control. In high wind conditions control of the amount of wind power into the device was deemed to be the preferable means of control. A number of different concepts to achieve this were devised and tested. The final concept employed limited the tail angle deflection and hence the lift produced by the aerofoils. This resulted in a seamless “throttle” control allowing the device to be used in any wind strength by adjusting the control to a position that resulted in the device receiving a suitable amount of power from the wind. The outcome of performance tests conducted indicated that the device has the potential to be developed into a viable wind turbine for both small and large scale applications. The ability to control the power input from the wind to the machine from zero to a maximum is considered to be one of the most beneficial outcomes of this project and together with the quiet operation and low speed, are considered the main advantages of the device over existing wind turbine designs. The possibilities of using the device to compress air for energy storage are exciting avenues that warrant further research.

Sound maintenance strategies and planning are of crucial importance for wind power systems, and especially for offshore locations. In the last decades, an increased awareness of the impact of human living on the environment has emerged in the world. The importance of developing renewable energy is today highly recognized and energy policies have been adopted towards this development. Wind energy has been the strongest growing renewable source of energy this last decade. Wind power is now developing offshore where sites are available and benefits from strong and steady wind. However, the initial investments are larger than onshore, and operation and maintenance costs may be substantially higher due to transportation costs for maintenance and accessibility constrained by the weather. Operational costs can be significantly reduced by optimizing decisions for maintenance strategies and maintenance planning. This is especially important for offshore wind power systems to reduce the high economic risks related to the uncertainties on the accessibility and reliability of wind turbines. This thesis proposes decision models for cost efficient maintenance planning and maintenance strategies for wind power systems. One model is proposed on the maintenance planning of service maintenance activities. Two models investigate the benefits of condition based maintenance strategies for the drive train and for the blades of wind turbines, respectively. Moreover, a model is proposed to optimize the inspection interval for the blade. Maintenance strategies for small components are also presented with simple models for component redundancy and age replacement. The models are tested in case studies and sensitivity analyses are performed for parameters of interests. The results show that maintenance costs can be significantly reduced through optimizing the maintenance strategies and the maintenance planning.

No description available.