# Variables and Symbols#

There is a convention on consistent variable names throughout the library:

List of used Variables and Parameters#

variable

description

tz

timezone

latitude

latitude

longitude

longitude

dni

dni_extra

direct normal irradiance at top of atmosphere (extraterrestrial)

dhi

bhi

ghi

gri

aoi

angle of incidence between $$90\deg$$ and $$90\deg$$

aoi_projection

cos(aoi)

airmass

airmass

airmass_relative

relative airmass

airmass_absolute

absolute airmass

poa_ground_diffuse

poa_direct

poa_diffuse

total diffuse irradiation in plane. sum of ground and sky diffuse.

poa_global

global irradiation in plane. sum of diffuse and beam projection.

poa_sky_diffuse

diffuse irradiation in plane from scattered light in the atmosphere (without ground reflected irradiation)

g_poa_effective

surface_tilt

tilt angle of the surface

surface_azimuth

azimuth angle of the surface

solar_zenith

zenith angle of the sun in degrees

apparent_zenith

refraction-corrected solar zenith angle in degrees

solar_azimuth

azimuth angle of the sun in degrees East of North

temp_cell

temperature of the cell

temp_module

temperature of the module

temp_air

temperature of the air

temp_dew

dewpoint temperature

relative_humidity

relative humidity

wind_speed

wind speed

wind_direction

wind direction

pressure

atmospheric pressure

v_mp, i_mp, p_mp

module voltage, current, power at the maximum power point

v_oc

open circuit module voltage

i_sc

short circuit module current

i_x, i_xx

Sandia Array Performance Model IV curve parameters

photocurrent

photocurrent

saturation_current

diode saturation current

resistance_series

series resistance

resistance_shunt

shunt resistance

transposition_factor

the gain ratio of the radiation on inclined plane to global horizontal irradiation: $$\frac{poa\_global}{ghi}$$

pdc0

nameplate DC rating

pdc, dc

dc power

gamma_pdc

module temperature coefficient. Typically in units of 1/C.

pac, ac

ac powe.

eta_inv

inverter efficiency

eta_inv_ref

reference inverter efficiency

eta_inv_nom

nominal inverter efficiency

For a definition and further explanation on the variables, common symbols and units refer to the following sources:

Note

These further references might not use the same terminology as pvlib. But the physical process referred to is the same.