Irradiance decomposition

Irradiance decomposition

ghi_decomposition(
  x,
  yday = "yday",
  GHI = "SWGDN",
  zenith = "zenith",
  beam = "beam",
  method = 0,
  zenith_max = 89,
  keep.all = FALSE,
  verbose = getOption("merra2.verbose")
)

Arguments

x

yday

day of a year, integer vector

GHI

Global Horizontal Irradiance from MERRA-2 subset (\(GHI, W/m^2\))

zenith

Zenith angle, degrees

beam

method

zenith_max

keep.all

verbose

Details

List or data.frame with estimated following solar geometry variables:

• Extraterrestrial irradiance (\(G_e\)) \[G_e = G_{sc}\times\big(1+0.033\cos{(\frac{360n}{365})}\big)\] where:
  \(G_{sc} = 1360.8W/m^2\), is the solar constant based on the latest NASA observation (Kopp and Lean, 2011);
  \(n - \) day of the year.
  

• Clearness index (\(k_t\)) \[k_t = \frac{GHI}{G_e\cos{(zenith)}}\]

• Diffuse fraction (\(k_d\)) \[k_d = \begin{cases} 1-0.09k_t & & {k_t < 0.22}\newline 0.9511-0.1604k_t+4.388k_t^2-16.638k_t^3+12.336k_t^4 & & {0.22 \leq k_t \leq 0.8}\newline 0.165& & {k_t > 0.8} \end{cases} \]

• Direct Normal Irradiance (\(DNI, W/m^2\)) \[DNI = \frac{(1-k_d)}{\cos{(zenith)}}\times{GHI}\]

• Diffuse Horizontal Irradiance (\(DHI, W/m^2\)) \[DHI = k_d\times{GHI}\] where:
  \(GHI\) - Global Horizontal Irradiance (\(GHI, W/m^2\)) from MERRA-2 dataset. \[GHI = DHI + DNI \times{\cos{(zenith)}}\]

Examples

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#> [1] NA