Variable List

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

SymbolDefinitionPage 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 Overview: Direct Normal Irradiance, Global Horizontal Irradiance, POA Beam, Hay and Davies Sky Diffuse Model, Reindl Sky Diffuse Model
 $$DOY$$ Day of YearExtraterrestrial Radiation
 $$E_0$$ reference irradiance, typically 1000 W/m2Sandia Cell Temperature Model, Effective Irradiance, Sandia PV Array Performance Model, PVWatts
 $$E_a$$ Extraterrestrial Irradiance [W/m2]Extraterrestrial Radiation, DISC Model, Hay 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 TimeSimple Models
 $$E{sc}$$Solar ConstantExtraterrestrial Radiation
$$eta_{m}$$efficiency of PV modulePVsyst Cell Temperature Model
$$f_d$$fraction of diffuse light used by PV moduleSandia PV Array Performance Model
 $$GHI$$ Global Horizontal Irradiance [W/m2]Direct Normal Irradiance, DISC Model, Global 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 currentSingle Diode Equivalent Circuit Models
 $$IAM$$ Incidence angle modifierIncident Angle Reflection Losses
 $$IAM_b$$ Incidence angle modifier for beam component of irradianceIncident Angle Reflection Losses
 $$I_D$$ voltage-dependent current lost to recombinationSingle Diode Equivalent Circuit Models
 $$I_L$$ light-generated current produced within PV cellSingle Diode Equivalent Circuit Models
 $$I{M}$$ current of module or arraySingle Diode Equivalent Circuit Models
 $$I_{mp}$$ current at maximum powerSandia PV Array Performance Model
 $$I{sc}$$ short circuit currentSandia 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 resistancesSingle Diode Equivalent Circuit Models
 $$K$$ glazing extinction coefficientPhysical Model of IAM
 $$K_n$$ Direct Normal TransmittanceDISC Model
 $$K_t$$ Global Horizontal TransmittanceDISC Model
 $$L$$ glazing thicknessPhysical Model of IAM
 $$Long_{local}$$Longitude of the observerSimple Models
 $$Long_{sm}$$Longitude of standard meridian of observer’s time zoneSimple Models
 $$M$$ air mass modifierDe Soto Model
 $$N_s$$number of cells in seriesSingle Diode Equivalent Circuit Models
 $$P_{AC}$$ AC output powerSandia Inverter Model
 $$P_{ACO}$$ maximum AC power ratingSandia Inverter Model
 $$P_{DC}$$ DC input powerSandia Inverter Model
 $$p_{in}$$normalized DC powerDriesse Inverter Model
 $$p_{loss}$$Driesse Inverter Model
 $$P_{mp}$$maximum power point powerPoint-value Models, PVWatts
 $$P_{mp0}$$PVWatts
 $$PR_{AC}$$ daily AC performance ratioPerformance Ratio
 $$q$$ elementary charge (constant)Single Diode Equivalent Circuit Models, Sandia PV Array Performance Model
 $$R_{av}$$ mean Sun-Earth distanceExtraterrestrial Radiation
 $$R_s$$ series resistanceSingle Diode Equivalent Circuit Models
 $$R_{sh}$$ shunt resistanceSingle Diode Equivalent Circuit Models
 $$R_{sh,ecp}$$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 CelsiusEffective 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 timeSimple Models
 $$T_{m}$$ module temperature [°C]Sandia Module Temperature Model, Faiman Module Temperature Model, Sandia Cell Temperature Model
 $$T_{solar}$$ solar timeSimple Models
 $$U_{0}$$ constant heat transfer componentFaiman Module Temperature Model, PVsyst Cell Temperature Model
 $$U_1$$ convective heat transfer componentFaiman 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 voltageDriesse 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 voltageSingle 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 yieldPerformance Ratio
 $$Y_r$$ ratio of plane-of-array irradiance to reference irradiancePerformance Ratio
$$alpha$$ absorption coefficient of PV modulePVsyst Cell Temperature Model
$$alpha_{lmp}$$ temperature coefficient for maximum power point currentSandia PV Array Performance Model
$$alpha_{lsc}$$ temperature coefficient for short circuit currentEffective Irradiance, De Soto Model, Sandia PV Array Performance Model, PVsyst Model
$$alpha_{lscr}$$Effective Irradiance
$$beta_{Voc}$$ temperature coefficient for module; open circuit voltageSandia PV Array Performance Model
$$beta_{Voc0}$$ temperature coefficient for module; open circuit voltage at reference irradianceSandia PV Array Performance Model
$$gamma$$ temperature correction for PmpPVWatts
$$Delta
T$$
 temperature difference parameterSandia Cell Temperature Model
$$varepsilon$$ bins of clearnessPerez Sky Diffuse Model
$$theta_A$$azimuth angleSun Position, Angle of Incidence
$$theta_d$$declination of the sunSimple Models
$$theta_{el}$$solar elevation angleSun Position
$$theta_{hr}$$ hour angleSimple Models
$$theta_{r}$$ angle of refractionPhysical Model of IAM
$$theta_Z$$solar zenith angleSun Position, Air Mass, Angle of Incidence, Simple Sandia Sky Diffuse Model, Perez Sky Diffuse Model
$$kappa$$ constantPerez Sky Diffuse Model
$$lambda$$ latitude of the observerSimple Models
$$tau$$ weighted transmittanceIncident Angle Reflection Losses