Nomenclature#
There is a convention on consistent variable names throughout the library:
- airmass#
Airmass
- airmass_absolute#
Absolute airmass
- airmass_relative#
Relative airmass
- albedo#
Ratio of reflected solar irradiance to global horizontal irradiance [unitless]
- aod#
- aod500#
aerosol optical depth [unitless]. Measure of aerosols (e.g., smoke particles, desert dust) distributed within a column of air from the instrument (Earth’s surface) to the top of the atmosphere. The AOD value indicates the level of extinction of sunlight in this column, and when followed by a number (e.g. AOD500), indicates the extinction at this wavelength (500nm).
- aoi#
Angle of incidence. Angle between the surface normal vector and the vector pointing towards the sun’s center. [°]
- aoi_projection#
cos(aoi). When the sun is behind the surface, the value is negative. For many uses, negative values must be set to zero.
- ape#
Average photon energy
- apparent_zenith#
Refraction-corrected solar zenith angle. The solar zenith angle describes the position of the sun relative to the vertical and is defined as the angle between a vector pointed straight up and a vector pointed at the sun, from the observer. [°]
- apparent_elevation#
Refraction-corrected solar elevation angle. This is the complement of apparent_zenith (90 - apparent_zenith). [°]
- bhi#
Beam/direct horizontal irradiance
- clearness_index#
clearness index [unitless]. Ratio of global horizontal irraidance to the extra terrestrial irriance. The clearness index ranges between 0 and 1, with values closer to 1 indicating clear skies.
- clearsky_index#
clearsky index [unitless]. Ratio of actual global irradiance to modeled clearsky global irradiance.
- dhi#
Diffuse horizontal irradiance
- dni#
Direct normal irradiance [Wm⁻²]. Irradiance received per unit area by a surface perpendicular (normal) to the sun’s rays that propagate in a straight line from the sun.
- dni_clear#
Clear sky direct normal irradiance
- dni_extra#
Direct normal irradiance at top of atmosphere (extraterrestrial)
- effective_irradiance#
Effective irradiance
- eta_inv#
Inverter efficiency
- eta_inv_nom#
Nominal inverter efficiency
- eta_inv_ref#
Reference inverter efficiency
- g_poa_effective#
Broadband plane of array effective irradiance
- gamma_pdc#
Module temperature coefficient. Typically in units of 1/C.
- ghi#
Global horizontal irradiance
- ghi_clear#
Clearsky global horizontal irradiance [Wm⁻²]
- ghi_extra#
Horizontal irradiance at top of atmosphere (extraterrestrial)
- gri#
Ground-reflected irradiance
- i_sc#
Short circuit module current
- i_x, i_xx#
Sandia Array Performance Model IV curve parameters
- latitude#
Latitude in decimal degrees. Positive north of equator, negative to south.
- longitude#
Longitude in decimal degrees. Positive east of prime meridian, negative to west.
- pac, ac#
AC power
- pdc, dc#
DC power
- pdc0#
Nameplate DC rating
- photocurrent#
Photocurrent
- poa_diffuse#
Total diffuse irradiance in plane [Wm⁻²]. Sum of ground and sky diffuse components of global irradiance.
- poa_direct#
Direct/beam irradiance in plane [Wm⁻²].
- poa_global#
Global irradiance in plane. Sum of diffuse and beam projection [Wm⁻²].
- poa_ground_diffuse#
In plane ground reflected irradiance [Wm⁻²].
- poa_sky_diffuse#
Diffuse irradiance in plane from scattered light in the atmosphere (without ground reflected irradiance) [Wm⁻²].
- precipitable_water#
Total precipitable water contained in a column of unit cross section from earth to top of atmosphere
- pressure#
Atmospheric pressure
- relative_humidity#
Relative humidity
- resistance_series#
Series resistance
- resistance_shunt#
Shunt resistance
- saturation_current#
Diode saturation current
- solar_azimuth#
Azimuth angle of the sun in degrees East of North. The solar azimuth angle describes the sun’s position along the horizon relative to the observer. Azimuth is defined as degrees East of North, so North = 0°, East = 90°, South = 180°, West = 270°.
- solar_zenith#
Zenith angle of the sun in degrees [°]. Zenith is the angle between is between a vector pointed straight up and a vector pointed at the sun, from the observer. Zenith is the complement of solar elevation, i.e., zenith = 90 - elevation.
- spectra#
- spectra_components#
Spectral irradiance (components) [Wm⁻²nm⁻¹]. The amount of energy incident on a unit area per unit time and per unit wavelength. As with broadband irradiance, global spectral irradiance is composed of direct and diffuse components.
- surface_azimuth#
Azimuth angle of the surface in degrees East of North. Surface azimuth is specified by the horizontal projection of the normal vector from the surface. Azimuth is defined as degrees East (clockwise) of North, so North = 0°, East = 90°, South = 180°, West = 270°.
- surface_tilt#
Tilt from horizontal [°]. The surface tilt angle is defined as degrees from the horizontal such that a surface facing up would have a surface tilt of 0°, and one facing the horizon would be 90°. [°]
- temp_air#
Temperature of the air
- temp_cell#
Temperature of the cell
- temp_dew#
Dewpoint temperature
- temp_module#
Temperature of the module
- tz#
Timezone
- v_mp, i_mp, p_mp#
Module voltage, current, power at the maximum power point
- v_oc#
Open circuit module voltage
- wind_direction#
Wind direction
- wind_speed#
Wind speed
For further explanation of the variables, common symbols, and units, refer to the following sources from SoDa Service:
Note
These further references might not use the same terminology as pvlib. But the physical process referred to is the same.