Variable List

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This page is in development as of 7/23/2013.

Symbol	Definition	Page Links
$A_{i}$	Anisotropy Index [unitless]	Hay and Davies Sky Diffuse Model , Reindl Sky Diffuse Model
$AM$	Air Mass [unitless]	Air Mass
$AM_{a}$	Absolute Air Mass [unitless]	Perez Sky Diffuse Model, Sandia PV Array Performance Model
$\theta_{AOI}$	Angle of Incidence [degrees]	POA Beam Angle of Incidence Hay and Davies Sky Diffuse Model Reindl Sky Diffuse Model Perez Sky Diffuse Model
$DHI$	Diffuse Horizontal Irradiance [W/m²]	Global Horizontal Irradiance, Diffuse Horizontal Irradiance Isotropic Sky Diffuse Model Simple Sandia Sky Diffuse Model Hay and Davies Sky Diffuse Model Reindl Sky Diffuse Model Perez Sky Diffuse Model
$DNI$	Direct Normal Irradiance [W/m²]	Irradiance and Weather – Definitions and OverviewDirect Normal Irradiance Global Horizontal Irradiance POA Beam Hay and Davies Sky Diffuse Model Reindl Sky Diffuse Model
$DOY$	Day of Year	Extraterrestrial Radiation
$E_{0}$	reference irradiance, typically 1000 W/m²	Sandia Cell Temperature Model, Effective Irradiance Sandia PV Array Performance Model PVWatts
$E_{a}$	Extraterrestrial Irradiance [W/m²]	Extraterrestrial RadiationDISC ModelHay and Davies Sky Diffuse Model Reindl Sky Diffuse Model Perez Sky Diffuse Model
$E_{b}$	beam component of plane-of-array irradiance [W/m²]	Plane of Array (POA) Irradiance POA Beam Sandia PV Array Performance Model
$E_{d}$	sky diffuse component of plane-of-array irradiance [W/m²]	Plane of Array (POA) Irradiance Simple Sandia Sky Diffuse Model Hay and Davies Sky Diffuse Model Reindl Sky Diffuse Model Perez Sky Diffuse Model Sandia PV Array Performance Model
$E_{e}$	effective irradiance [unitless]	Effective Irradiance Sandia PV Array Performance Model PVWatts
$E_{POA}$	irradiance incident on the plane of the array [W/m²]	Plane of Array (POA) Irradiance Faiman Module Temperature Model Sandia Cell Temperature Model PVsyst Cell Temperature Model Effective Irradiance
$E_{qt}$	Equation of Time	Simple Models
$E_{sc}$	Solar Constant	Extraterrestrial Radiation
$eta_{m}$	efficiency of PV module	PVsyst Cell Temperature Model
$f_{d}$	fraction of diffuse light used by PV module	Sandia PV Array Performance Model
$GHI$	Global Horizontal Irradiance [W/m²]	Direct Normal IrradianceDISC ModelGlobal Horizontal Irradiance Simple Sandia Sky Diffuse Model Reindl Sky Diffuse Model
$I$	Current [amps]	Module IV Curve Single Diode Equivalent Circuit Models
$I_{0}$	Saturation current	Single Diode Equivalent Circuit Models
$IAM$	Incidence angle modifier	Incident Angle Reflection Losses
$IAM_{b}$	Incidence angle modifier for beam component of irradiance	Incident Angle Reflection Losses
$I_{D}$	voltage-dependent current lost to recombination	Single Diode Equivalent Circuit Models
$I_{L}$	light-generated current produced within PV cell	Single Diode Equivalent Circuit Models
$I_{M}$	current of module or array	Single Diode Equivalent Circuit Models
$I_{mp}$	current at maximum power	Sandia PV Array Performance Model
$I_{sc}$	short circuit current	Sandia Model Effective Irradiance Sandia PV Array Performance Model
$I_{sc0}$		Effective Irradiance Sandia PV Array Performance Model
$I_{scr}$		Effective Irradiance
$I_{scr0}$		Effective Irradiance
$I_{sh}$	current lost due to shunt resistances	Single Diode Equivalent Circuit Models
$K$	glazing extinction coefficient	Physical Model of IAM
$K_{n}$	Direct Normal Transmittance	DISC Model
$K_{t}$	Global Horizontal Transmittance	DISC Model
$L$	glazing thickness	Physical Model of IAM
$Long_{local}$	Longitude of the observer	Simple Models
$Long_{sm}$	Longitude of standard meridian of observer’s time zone	Simple Models
$M$	air mass modifier	De Soto Model
$N_{s}$	number of cells in series	Single Diode Equivalent Circuit Models
$P_{AC}$	AC output power	Sandia Inverter Model
$P_{AC0}$	maximum AC power rating	Sandia Inverter Model
$P_{DC}$	DC input power	Sandia Inverter Model
$p_{in}$	normalized DC power	Driesse Inverter Model
$p_{loss}$		Driesse Inverter Model
$P_{mp}$	maximum power point power	Point-value Models PVWatts
$P_{mp0}$		PVWatts
$PR_{AC}$	daily AC performance ratio	Performance Ratio
$q$	elementary charge (constant)	Single Diode Equivalent Circuit Models Sandia PV Array Performance Model
$R_{av}$	mean Sun-Earth distance	Extraterrestrial Radiation
$R_{s}$	series resistance	Single Diode Equivalent Circuit Models
$R_{sh}$	shunt resistance	Single Diode Equivalent Circuit Models
$R_{sh,exp}$		PVsyst Model
$S$	total absorbed irradiance [W/m²]	De Soto Model PVsyst Model
$SF$	soiling factor; ranges from 0 (no soiling)to 1 (complete soiling)	Effective Irradiance
$T_{0}$	reference temperature, typically 25 degrees Celsius	Effective Irradiance Sandia PV Array Performance Model PVWatts
$T_{c}$	cell temperature [°C]	Sandia Cell Temperature Model PVsyst Cell Temperature Model Effective Irradiance De Soto Model PVWatts
$T_{cr}$		Effective Irradiance
$T_{local}$	local time	Simple Models
$T_{m}$	module temperature [°C]	Sandia Module Temperature Model Faiman Module Temperature Model Sandia Cell Temperature Model
$T_{solar}$	solar time	Simple Models
$U_{0}$	constant heat transfer component	Faiman Module Temperature Model PVsyst Cell Temperature Model
$U_{1}$	convective heat transfer component	Faiman Module Temperature Model PVsyst Cell Temperature Model
$V$	voltage [V]	Module IV Curve
$V_{DC}$	DC input voltage [V]	Sandia Inverter Model
$V_{DC0}$	DC voltage level at which AC power rating is achieved [V]	Sandia Inverter Model
$v_{in}$	normalized DC voltage	Driesse Inverter Model
$V_{M}$	voltage of module or array [V]	Single Diode Equivalent Circuit Models
$V_{mp}$	maximum power point voltage [V]	Sandia PV Array Performance Model
$V_{oc}$	open circuit voltage [V]	Sandia PV Array Performance Model
$V_{T}$	thermal voltage	Single Diode Equivalent Circuit Models
$WS$	wind speed [m/s]	Sandia Module Temperature Model Faiman Module Temperature Model PVsyst Cell Temperature Model
$Y_{fAC}$	AC system yield	Performance Ratio
$Y_{r}$	ratio of plane-of-array irradiance to reference irradiance	Performance Ratio
$alpha$	absorption coefficient of PV module	PVsyst Cell Temperature Model
$alpha_{Imp}$	temperature coefficient for maximum power point current	Sandia PV Array Performance Model
$alpha_{Isc}$	temperature coefficient for short circuit current	Effective Irradiance De Soto Model Sandia PV Array Performance Model PVsyst Model
$alpha_{Iscr}$		Effective Irradiance
$beta_{Voc}$	temperature coefficient for module; open circuit voltage	Sandia PV Array Performance Model
$beta_{Voc0}$	temperature coefficient for module; open circuit voltage at reference irradiance	Sandia PV Array Performance Model
$gamma$	temperature correction for Pmp	PVWatts
$Delta T$	temperature difference parameter	Sandia Cell Temperature Model
$varepsilon$	bins of clearness	Perez Sky Diffuse Model
$theta_{A}$	azimuth angle	Sun Position Angle of Incidence
$theta_{d}$	declination of the sun	Simple Models
$theta_{el}$	solar elevation angle	Sun Position
$theta_{hr}$	hour angle	Simple Models
$theta _{r}$	angle of refraction	Physical Model of IAM
$theta_{Z}$	solar zenith angle	Sun Position Air Mass Angle of Incidence Simple Sandia Sky Diffuse Model Perez Sky Diffuse Model
$kappa$	constant	Perez Sky Diffuse Model
$lambda$	latitude of the observer	Simple Models
$tau$	weighted transmittance	Incident Angle Reflection Losses

Variable List

Symbol

Definition

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