Environmental Engineering Reference
In-Depth Information
Supporting Research and Technology
While the construction and testing of particular wind turbines engendered the most
interest and publicity, these systems evolved due to the advances in the basic technologies
that underlie the design and siting of the turbines themselves. Research and technology
development were inanced principally by government grants and contracts because of the
limited inancial resources of the wind industry and the uncertain markets during the l970s
and l980s. The three technical needs underlying the future success of wind power were (1)
the need to improve performance , particularly annual energy output, (2) the need to extend
structural lifetime and integrity , while decreasing material costs and design complexity, and
(3) the need to be able to rapidly locate and evaluate productive wind turbine sites , with
reasonable accuracy. The disciplines of aerodynamics, structural dynamics, and the atmo-
spheric sciences are interrelated in all three of these areas.
Wind Characteristics
In wind energy conversion systems, the wind “fuel” is the source of both the energy
and the principal structural loads. Hence, the wind's characteristics directly affect both
energy production and system cost. Moreover, the wind speed varies with time on scales
from seconds to years, affecting mean and transient loads, control of peak power, and utility
dispatch and planning. The wind also varies with location, affecting siting, turbine spacing,
and proitability. Furthermore, the wind's power can range from zero to an order of
magnitude above the mean. This inconstant behavior of the wind leads to unique design
problems that require an understanding of wind fundamentals for solution. Lastly, wind
measurement and research in the past have been aimed at weather prediction, with the bulk
of the existing data being collected for aviation purposes and, more recently, environmental
studies. This data base, therefore, contains major biases toward airports and urban sites and
away from potential wind turbine locations.
In 1974, the Battelle Paciic Northwest Laboratory (PNL) undertook the task to
develop both the data base and the analytical modeling tools for site evaluation and
description of wind characteristics. On the siting front, an initial U.S. Wind Atlas was
developed [Barchet et al . 1980-81] from National Atmospheric and Oceanographic
Administration data (principally from airports), utilizing early interpolation tools. This Atlas
presented estimates of the annual and quarterly mean wind speeds for every 25 square
kilometers of the U.S., and the level of uncertainty in those wind speeds. It formed the
basis for the irst estimates of the national wind resource and served as a guide for the
early “wind prospecting” by entrepreneurs endeavoring to develop and commercialize wind
power. The California Energy Commission, recognizing the state's potential for wind
power, extended the California atlas to a iner scale [Miller and Simon 1980].
PNL developed the irst world wind resource map (on a coarser scale) for the World
Meteorological Organization [WMO 1981]. At the United Nations Conference on New and
Renewable Sources of Energy in Nairobi in 1981, this work was a stimulus to the
investigation of the worldwide potential of wind power. Later, more advanced interpolation
tools and analytical techniques, utilizing climatological and upper air data as well as
additional wind data from numerous sources, led to the creation of an advanced Wind
Energy Resource Atlas of the United States in 1987 [Elliott et al. 1987].
While wind atlases are useful for estimating large-scale resources and identifying poten-
tially high wind areas, terrain and climate cause variations too localized to be identiied on
any reasonable map scale. Thus, models were developed to estimate low patterns and wind
velocities across relatively small geographical areas. Such models and other techniques
allow estimation of wind speeds over a site less than 10 square kilometers in area, given
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