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The Wind Characteristics Program Element (WCPE) provides wind information, through the Wind Energy Conversion Program (WECP), for those involved in energy program planning, design and evaluation of performance of wind energy conversion systems (WECS), selection of sites for WECS installation, and WECS operations. Currently the technical work within the WCPE is divided among four program areas. These areas are to provide wind characteristics for design and performance evaluation; site slection; resource assessment; and operations. Work is being undertaken in the first three areas.
An investigation was conducted into the feasibility of applying the Composite Bearingless Rotor (CBR) concept to wind turbines. The CBR blade is comprised of a conventional blade construction over the outboard span, but inboard is made up simply from a finite length (about 15 percent of the radius) of unidirectional composite material. This member, called the flexbeam, replaces the hinges and bearings normally located at the blade root and provides the necessary flatwise and edgewise stiffness, but due to the unidirectional fiber alignment, has low torsional stiffness. Blade pitch control is achieved by applying a moment at the outboard end of the flexbeam and elastically twisting it. The work described in the final report was conducted under contract with ERDA and consisted of the design and fabrication of a dynamically scaled wind turbine model, the wind tunnel testing of this model, and the evaluation of several control concepts in an attempt to achieve a self-regulating system. Such a system was achieved and experimentally demonstrated in the wind tunnel. Operating characteristics at wind speeds exceeding 30 mph were investigated and simulated start ups and wind direction changes were successfully executed.
The purpose of this report is to provide a set of reference or standard values of wind profiles, wind speed distributions and their effects on wind turbine performance for engineering design applications. Based on measured Weibull distribution parameters, representative average, low, and high variance data are given for height profiles of mean, 25 percentile, and 75 percentile wind speeds; and for wind speed probability density (velocity frequency) functions and cumulative probability (velocity duration) functions at selected heights. Results of a sensitivity analysis of the dependence of wind turbine performance parameters on cut-in speed, and rated speed for various mean wind and wind variance regimes are also presented. Wind turbine performance is expressed in terms of capacity factor (ratio of mean power output to rated power) and recovery factor (ratio of mean energy output to energy theoretically available in the wind). The representative high, mean, and low variance cases were determined from calculated Weibull distributions at 140 sites across the Continental U.S., and all of the representative functions are evaluated at mean wind speeds of 4, 5, 6, 7, and 8 m/s at standard 10 m level.
The existing information on mean wind profiles and the characteristics of turbulence at a point are adequate for many purposes, but they are not sufficient for WECS design. The purpose of this paper is to describe some of the variability observed in a recent measurement program (Ramsdell, 1975). In particular, the variations of the vertical and lateral shear of the longitudinal component of the wind will be described. Data on the fluctuations of the vertical and lateral shears of the longitudinal wind component near the Seattle, Washington, central business district have been analyzed to determine shear characteristics downwind of large roughness elements. The analysis has examined the frequency distributions and time scales of the shear fluctuations. When possible the results have been compared with results of analysis of data from Cape Kennedy, Florida.
Separate abstracts are included for twenty-nine of the thirty papers presented concerning vertical axis wind turbines. One paper has previously been abstracted and included in the ERDA Energy Data Base and Energy Research Abstracts journal.
Numerical model calculations of three-dimensional regional wind fields oriented toward identifying the location, intensity and extent of wind energy-rich areas on Oahu are reported. The use of these calculations in planning a field data-collection program to study areas of expected high wind energy is described. Criteria for the selection of wind-energy subregions of primary interest are discussed.
In the basic wind characteristics assessment procedure a new step is incorporated to overcome its most serious deficiencies. This step employs mathematical model-based meteorological prediction tools. With them climatological data from weather stations in the region are used to infer climatological data at the unmeasured locations within the region. Meteorological phenomena taking place in regions comparable to the distance between synoptic weather stations (approximately 200 km) and in the immediate vicinity of the windmill site (approximately 1 km) are considered. Computer codes were developed for each of these regimes, and calculations of wind flow over complex terrain have been performed. Results of some of these wind calculations are presented, illustrating the effects of terrain on wind energy potential.
Detailed wind energy assessment from the available wind records, and evaluation of the application of wind energy systems to an existing electric utility were performed in an area known as the Texas Panhandle, on the Great Plains. The study area includes parts of Texas, eastern New Mexico, the Oklahoma Panhandle and southern Kansas. The region is shown to have uniformly distributed winds of relatively high velocity, with average wind power density of 0.53 kW/m/sup 2/ at 30 m height at Amarillo, Texas, a representative location. The annual period of calm is extremely low. Three separate compressed air storage systems with good potential were analyzed in detail, and two potential pumped-hydro facilities were identified and given preliminary consideration. Aquifer storage of compressed air is a promising possibility in the region.
Information is presented concerning: review of the status of general design efforts in the areas of aerodynamics, structures, systems analysis, and testing; summary of preliminary design details of the proposed 17-m turbine/60-kW generator system for power grid application; and structural analysis and operational test results for the existing 5-m turbine.
An investigation was carried out to examine the use of blade aeroelastic properties for providing rotational speed control for a wind turbine generator (WTG). The study was specifically directed at obtaining a rotor configuration that has the capability for maintaining nearly constant torque at constant RPM in the presence of varying wind conditions and is aimed at eliminating the current requirement for mechanical pitch change devices. The approach considered is one in which rotor twist due to aerodynamic loading is used to adjust the blade's pitch as the wind speed changes. The preliminary design concept that has evolved is a flexible rotor blade formed from a series of individual, light, rigid segments that are arranged along the blade spar. Each segment can rotate around the spar but is restricted in pitch by a nonlinear mechanical spring. The results of performance calculations as well as vibration and flutter analyses are presented. Based on these results, the concept appears to provide an attractive solution to the problem of WTG operation in a varying wind field.