Progress on the development of a New Wind Energy Site Selection Methodology achieved during the final development phase of the program is described. The siting approach provides a useful preliminary to, and partial substitute for, conventional siting studies involving large field test programs by employing mathematical models of meso- and micrometeorology in regions of complex terrain. The models make use of data from meteorological stations where weather records are available and predict the windfield climatology of sites, within the region of interest, where data are unavailable. These forecasts are subsequently analyzed to predict site wind characteristics and to aid in the design of detailed field program to quantify the wind characteristics at promising wind energy sites.

The underlying theory is presented for determining blade and rotor/tower vibration and dynamic stability characteristics as well as the basic dynamic (as opposed to aerodynamic) operating loads. Starting with a simple concept of equivalent hinged rotors, the equations of motion for the blade including pitch, flap and lag motions are developed. The nonlinear equations are derived first and linearized about a finite displacement of the blade out of the plane of rotation. This is important since wind turbines tend to operate at relatively high coning angles. The effect of distributed flexibility, as opposed to the equivalent hinge concept, is then discussed.

The material is presented as far as possible in the form of charts, either tables or graphs, from which specific design information may be selected or trends determined without the need for computational facilities. For design purposes, or when attempting to correct a design deficiency, trends are frequently more useful than absolute information. Since it is impossible to cover all possible configurations for a system with as many parameters as a wind turbine, interpolation will be necessary in many cases.

A generalized wind estimate based on a limited number of uncertain field measurements is computed at each point in a given geographical region. A point-by-point comparison with a numerical model prediction of the wind field is then described. This comparison results in numerical assessments of the probability that the model succeeded in predicting the actual wind field and that the field measurements contain sufficient information on which to base such a comparison.

The basic aerodynamic theory of the wind turbine is presented, starting with the simple momentum theory based on uniform inflow and an infinite number of blades. The basic vortex theory is then developed. Following these basics, the more complete momentum theory, including swirl, non-uniform inflow, the effect of a finite number of blades, and empirical correction for the vortex ring condition is presented. The more complete vortex theory is presented which includes unsteady aerodynamic effects but based on a semi-rigid wake. Methods of applying this theory for performance estimation are discussed as well as for the purpose of computing time varying airloads due to windshear and tower interference.

The dynamics of the drive system and various approaches to power transmission are described. The effects on performance of using a constant rotor speed as opposed to a rotor speed varying with the wind speed are discussed for various rotor operating schedules and typical wind distributions. The dynamics of the combined rotor, alternator, and drive system are analyzed. Conditions which could lead to electro-dynamic instabilities and desynchronization are discussed as well as means for stabilizing the system. The dynamics of the drive system and important design conditions for various drive systems are discussed, such as location of the alternators, use of hydraulic drive systems and smoothing techniques.

Lifting line theory which is the counterpart of Prandtl's lifting line theory for rotating wing is employed for the overall performance analysis of a horizontal axis wind turbine rotor operating in a uniform flow. The wake system is modeled by non-rigid wake which includes the radial expansion and the axial retardation of trailing vortices. For the non-uniform flow which are caused by the ground, the tower reflection, or the tower shadow, the unsteady airloads acting on the turbine blade are computed, using lifting line theory and a non-rigid wake model. An equation which gives the wind profile in the tower shadow region is developed. Also, the equations to determine pitch angle control are derived to minimize the flapping moment variations or the thrust variations due to the non-uniform flow over a rotation.

The results are presented of some brief experiments conducted on a wind turbine model of a rotor system to verify the aerodynamic theories developed and to investigate the dynamic excitation characteristics of wind turbines.

The nonlinear equations of motor for a rigid rotor restrained by three flexible springs representing, respectively, the flapping, lagging, and feathering motions are derived using Lagrange's equations, for arbitrary angular rotations. These are reduced to a consistent set of nonlinear equations using nonlinear terms up to third order. The complete analysis is divided into three parts, A, B, and C. Part A consists of forced response of two-degree flapping-lagging rotor under the excitation of pure gravitational field (i.e., no aerodynamic forces). In Part B, the effect of aerodynamic forces on the dynamic response of two-degree flapping-lagging rotor is investigated. In Part C, the effect of third degree of motion, feathering, is considered.