Photovoltaic and solar energy engineering terminology

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Some important photovoltaic terms and symbols used in solar energy engineering and in photovoltaics are presented in the tabels below. Detailed information can be found in "IEC/TR2 61836, Solar photovoltaic energy systems - Terms and symbols". For detailed definitions please see also references at the bottom of the page.

Units and symbols used in photovoltaics

Global irradiance

Beam irradiance

Diffuse irradiance

Global irradiation *

Beam irradiation *

Diffuse irradiation *

G

G_b

G_d

H

H_b

H_d

W/m²

W/m²

W/m²

J/m²

J/m²

J/m²

Specific heat

Thermal conductivity

Extinction coefficient

Index of refraction

Absorptance

Emittance

Reflectance

Density

Transmittance

c

k

K

n

α

ε

ρ

ρ

τ

J/kg K

W/m K

-

-

-

-

-

kg/m³

-

Altitude (0 do +/- 90°)

Surface tilt angle
(0 do +/- 90° tilt toward equator +)

Azimuth of surface
(0 to + 360° - CW from N positive)

Declination (0 to +/- 23.45°)

Incidence angle (0 to + 90°)

Zenith angle (0 to + 90^o)

Latitude
(0 to +/- 90^o, N from equator +)

Hour angle
(-180° to + 180° , noon 0°, afternoon positive)

α

β

γ

δ

i

Θ_z

Ψ

ω

degrees (°)

degrees (°)

degrees (°)

degrees (°)

degrees (°)

degrees (°)

degrees (°)

degrees (°)

*NOTE: The unit Wh/m² (kWh/m²) is often used in technical practise in Europe. Please look for further information and additional symbols in suggested literature.

Units and symbols - detailed information and conversion tools
	convert-me.com - Here you will find interactive calculators for many measurement systems both commonly used like metric and U.S. Avoirdupois and quite exotic like Ancient Greek and Roman. Languages:
	The NIST Reference on Constants Units and Uncertainty - This site addresses three topics: fundamental physical constants, the International System of Units (SI), which is the modern metric system, and expressing the uncertainty of measurement results. Both essential information and background information are given for each topic. Languages:
	Eric Weisstein's World of Science - physical and other scientifical terms explained in detail. Languages:

More information and some useful tools

IEC/TS 61836 Ed.2, Solar photovoltaic energy systems - Terms, definitions and symbols
Units and Symbols in Solar Energy; Solar Energy, vol.71, number 1, 2001
Beckman, W.A et al.: Units and symbols in solar energy; Solar Energy, vol. 21, no. 1, 1978, p. 65-68
Rösemann, R.: Solar Radiation Measurement, From Sensor to Application; Gengenbach Messtechnik, 2004.
TCAEP: The Constants and Equation Pages
English weigths and measures