
profile(mast, v.set, dir.set, num.sectors=12,
method=c("hellman", "loglm", "fixed"), alpha=NULL,
digits=3, print=TRUE)
pro(mast, v.set, dir.set, num.sectors=12,
method=c("hellman", "loglm", "fixed"), alpha=NULL,
digits=3, print=TRUE)
createMast
.alpha
12
."hellman"
, "loglm"
or "fixed"
(see Details section). Optional argument: "fixed"
is used if v.set
is a single dataset, "hellman"
is method
is "fixed"
. If alpha
is NULL
, 0.2
is used as default.3
.TRUE
, results are printed directly.v.set
)."hellman"
), defined as:
To calculate $\alpha$, profile
uses the inverted equation as:
If data is available for two or more heights, a log-linear model fit can be used for the computation of $\alpha$. In this case the data is logarithmized to allow for fitting a linear model. The models slope is then used as $\alpha$. Please note: depending on the data this method might result in negative $\alpha$.
If the wind speed is only known for one height, $\alpha$ must be estimated. $\alpha$ depends on various issues, including roughness and terrain of the site. Some empirical values for temperate climates are:
Brower, M., Marcus, M., Taylor, M., Bernadett, D., Filippelli, M., Beaucage, P., Hale, E., Elsholz, K., Doane, J., Eberhard, M., Tensen, J., Ryan, D. (2010) Wind Resource Assessment Handbook. http://www.awstruepower.com/wp-content/uploads/2012/01/10-30_wind-resource-handbook.pdf
International Electrotechnical Commission (2005) IEC 61400-12 Wind Turbines -- Part 12-1: Power Performance Measurements of Electricity Producing Wind Turbines. IEC Standard
createMast
, plotProfile
, printObject
# load and prepare data
data(winddata)
set40 <- createSet(height=40, v.avg=winddata[,2], dir.avg=winddata[,14])
set30 <- createSet(height=30, v.avg=winddata[,6], dir.avg=winddata[,16])
set20 <- createSet(height=20, v.avg=winddata[,10], v.std=winddata[,13])
ts <- formatTS(time.stamp=winddata[,1])
neubuerg <- createMast(time.stamp=ts, set40, set30, set20)
neubuerg <- clean(mast=neubuerg)
# create profile based on one height
profile(mast=neubuerg, v.set=1, dir.set=1) # default alpha=0.2
profile(mast=neubuerg, v.set=1, dir.set=1, alpha=0.15)
# calculate profile based on two heights
profile(mast=neubuerg, v.set=c(1,2), dir.set=1)
profile(mast=neubuerg, v.set=c(1,3), dir.set=1)
# same as above
profile(mast=neubuerg, v.set=c("set1", "set3"), dir.set="set1")
# calculate profile based on three heights
profile(mast=neubuerg, v.set=c(1,2,3), dir.set=1)
# change the method used for computation
# note: negative alphas!
profile(mast=neubuerg, v.set=c(1,2), dir.set=1, method="loglm")
# change number of direction sectors
profile(mast=neubuerg, v.set=c(1,2), dir.set=1, num.sectors=8)
# change number of digits and hide results
profile(mast=neubuerg, v.set=1, dir.set=1, digits=2)
profile(mast=neubuerg, v.set=1, dir.set=1, print=FALSE)
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