Page 139 - Fluid Power Engineering

116 Chapter Seven

(site-specific) through a process that takes out site-specific in-
fluences which include:
Obstacles that are in 1 km radius from the observed wind

site
Roughness that is within 20 km radius from the site

Contour or elevation of area inside a radius of 5 km

Thermally driven flow

The distance ranges above are guidelines for normal condi-
tions. RWC is generated through the process shown in Fig. 7-2
that follows the up arrow in the left side of the diagram. The
output of this process is the RWC.
Wind atlas. A collection of RWC for a large area that is of the

order of thousands of kilometers.
Wind resource. Site-specific wind speed or energy density at a

specified height is called a wind resource. This is generated
through the process in Fig. 7-2 that follows the down arrow in
the right side of the diagram. The output of the process is the
wind resource, shown at the bottom-right corner of Fig. 7-2.
Wind resource map (WRM). WRM is a description of wind re-

sources at a specific height for a specific granularity. Creation
of WRM can be a very computationally intensive process for
a finer granularity grid. Therefore, depending on purpose,
appropriate granularity WRM is created. For instance, 200 m
× 200 m granularity WRM may be created for prospecting,
where as 50 m × 50 m WRM may be created for micrositing
of turbines. WRM is created as a color plot of annual aver-
age wind speed or average energy density at a specific height;
however, seasonal averages are becoming more popular. The
WRM color map with the intensity of wind energy density is
used to explore the variation in wind resources over an area.
Wind resource assessment (WRA). WRA is a compilation of ag-

gregate data that includes, annual or seasonal:
WRM

Wind rose, which is a plot of average annual wind energy

density by direction
For each sector, average turbulence intensity

For each sector, average wind shear

For each sector, Weibull parameters for the distribution of

wind speed
Average annual energy production for chosen turbines of

a wind farm