Environmental Engineering Reference
In-Depth Information
Figure 16-6.
Photo simulation of a proposed wind project created by wind plant design soft-
ware. Such simulations can be useful for soliciting community feedback and building community
support.
Source:
AWS Truepower.
The frequencies within the sum are determined by applying speedup factors and
directional shifts to the observed speed and direction frequency distributions in the
TAB file based on relationships defined in the WRG file. The power output is taken
from the power curve interpolated or extrapolated to the appropriate air density. These
calculations are all handled automatically by the software, and there is usually little
reason for the user to delve into them. However, situations can arise where it becomes
helpful to understand them in some depth. For this reason, some of the key methods
and equations, along with the important topic of wake modeling, are addressed in
Section 16.7.
The net energy production equals the gross production minus losses. A good esti-
mate of plant losses is essential for accurately determining the long-term financial
performance of a wind project. A tendency to underestimate losses is one of the
reasons why wind plants have often not produced as much energy as predicted in
preconstruction studies. In North America, the overestimation averaged around 10%
for projects built up to 2008 (1, 2). Improved resource assessment methods, as well
as more realistic loss assumptions such as those described below, have largely closed
this gap (10).
Table 16-2 provides a breakdown of the main loss categories, each with a range
of values (as a percentage of energy production) encountered in practical application.
The loss categories are described in more detail below. It should be stressed that every
project is different, and some may have higher or lower losses than the ranges shown
here. In addition, losses can change over time. Availability losses, in particular, tend
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