solaR (version 0.37)

C_fSolD: Daily apparent movement of the Sun from the Earth

Description

Compute the daily apparent movement of the Sun from the Earth. This movement is mainly described (for the simulation of photovoltaic systems) by the declination angle, the sunset angle and the daily extra-atmospheric irradiation.

Usage

fSolD(lat, BTd, method='michalsky')

Arguments

lat

Latitude (degrees) of the point of the Earth where calculations are needed. It is positive for locations above the Equator.

BTd

Daily temporal base, a POSIXct object which may be the result of fBTd.

method

character, method for the sun geometry calculations to be chosen from 'cooper', 'spencer', 'michalsky' and 'strous'. See references for details.

Value

• A zoo object with these components:
• decl
  Declination angle (radians) for each day of year in dn or BTd
• eo
  Factor of correction due the eccentricity of orbit of the Earth around the Sun.
• ws
  Sunset angle (in radians) for each day of year. Due to the convention which considers that the solar hour angle is negative before midday, this angle is negative.
• Bo0d
  Extra-atmospheric daily irradiation (watt-hour per squared meter) incident on a horizontal surface
• EoT
  Equation of Time.

encoding

UTF-8

References

• Cooper, P.I., Solar Energy, 12, 3 (1969). "The Absorption of Solar Radiation in Solar Stills"

Spencer, Search 2 (5), 172, http://www.mail-archive.com/[e-mail]/msg01050.html Strous: http://www.astro.uu.nl/~strous/AA/en/reken/zonpositie.html Michalsky, J., 1988: The Astronomical Almanac's algorithm for approximate solar position (1950-2050), Solar Energy 40, 227-235, ftp://climate1.gsfc.nasa.gov/wiscombe/Solar_Rad/SunAngles/sunae.f Perpiñán, O, Energía Solar Fotovoltaica, 2012. http://procomun.wordpress.com/documentos/libroesf/ Perpiñán, O. (2012), "solaR: Solar Radiation and Photovoltaic Systems with R", Journal of Statistical Software, 50(9), 1-32, http://www.jstatsoft.org/v50/i09/

Examples

BTd=fBTd(mode='serie')

lat=37.2
fSolD(lat,BTd[100])
fSolD(lat,BTd[100], method='strous')
fSolD(lat,BTd[100], method='spencer')
fSolD(lat,BTd[100], method='cooper')

lat=-37.2
fSolD(lat,BTd[283])

#Solar angles along the year
SolD<-fSolD(lat,BTd=fBTd())

library(lattice)
xyplot(SolD)

#Calculation of the daylength for several latitudes
library(latticeExtra)

Lats=c(-60,-40,-20,0,20,40,60)
NomLats=ifelse(Lats>0, paste(Lats,'N', sep=''), paste(abs(Lats), 'S',
sep=''))
NomLats[Lats==0]='0'

mat=matrix(nrow=365, ncol=length(Lats))
colnames(mat)=NomLats
WsZ=zoo(mat, fBTd(mode='serie'))

for (i in seq_along(Lats)){
    SolDaux<-fSolD(lat=Lats[i],BTd=fBTd(mode='serie'));
    WsZ[,i]<-r2h(2*abs(SolDaux$ws))}

p=xyplot(WsZ, superpose=TRUE,
        ylab=expression(omega[s] (h)), auto.key=FALSE)
plab<-p+glayer(panel.text(x[1], y[1], NomLats[group.number], pos=2))
print(plab)