30
A. Funde and A. Shah
Fig. 2.10 a Irradiance variation through a typical clear-sky day of the month of April at Pune, India
(measured data) and b The monthly-average of daily global solar radiant exposure throughout a
year at Pune, India. The data of (b) is based on the Pvsyst ® software simulated data for the location
of Pune, India, derived from the MeteoNorm ® synthetic data
The daily and yearly global irradiance give us, thus, a precise indication of the
energy of incident sunlight to a specified area and during a specified period of time.
One needs to know these quantities, at a given location to accurately predict the future
performance of a solar power plant (see also Chap. 10 especially Sect. 10.2.5).
For better clarity of the terms used, following terms are drawn from the IEC
Glossary. Web address: http://std.iec.ch/glossary.
[Following elaboration is referring to Publication: IEC TS 61836, ed. 2.0 (2007–
12): Solar photovoltaic energy systems—Terms, definitions and symbols].
Irradiance:
(Symbol: G) (Unit: W × m
−2 )
electromagnetic radiated power per unit of area.
(a) direct irradiance: irradiance from the sun’s disk and from the circumsolar region
of the sky within a subtended angle of 8.7 × 10
−2 rad (5°)
(b) diffuse irradiance: irradiance excluding that portion which contributes to direct
irradiance
(c) global irradiance: sum of the direct and diffuse irradiance (or simply ‘irradiance’)
(d) global horizontal irradiance (GHI) global irradiance on a horizontal surface
NOTE Global horizontal irradiance, GHI usually takes into consideration the
albedo, although the albedo is often negligible in GHI.
(e) direct normal irradiance (DNI): irradiance received from a small solid angle
centered on the sun’s disc on a plane perpendicular to the sun’s rays
(f) in-plane irradiance, or plane of array irradiance (POAI): irradiance received
from the sun as a combination of direct normal irradiance and all forms of
diffuse light in the plane of the PV array
(g) integrated irradiance: continuously integrated spectral irradiance over a specified range of wavelengths
A. Funde and A. Shah
Fig. 2.10 a Irradiance variation through a typical clear-sky day of the month of April at Pune, India
(measured data) and b The monthly-average of daily global solar radiant exposure throughout a
year at Pune, India. The data of (b) is based on the Pvsyst ® software simulated data for the location
of Pune, India, derived from the MeteoNorm ® synthetic data
The daily and yearly global irradiance give us, thus, a precise indication of the
energy of incident sunlight to a specified area and during a specified period of time.
One needs to know these quantities, at a given location to accurately predict the future
performance of a solar power plant (see also Chap. 10 especially Sect. 10.2.5).
For better clarity of the terms used, following terms are drawn from the IEC
Glossary. Web address: http://std.iec.ch/glossary.
[Following elaboration is referring to Publication: IEC TS 61836, ed. 2.0 (2007–
12): Solar photovoltaic energy systems—Terms, definitions and symbols].
Irradiance:
(Symbol: G) (Unit: W × m
−2 )
electromagnetic radiated power per unit of area.
(a) direct irradiance: irradiance from the sun’s disk and from the circumsolar region
of the sky within a subtended angle of 8.7 × 10
−2 rad (5°)
(b) diffuse irradiance: irradiance excluding that portion which contributes to direct
irradiance
(c) global irradiance: sum of the direct and diffuse irradiance (or simply ‘irradiance’)
(d) global horizontal irradiance (GHI) global irradiance on a horizontal surface
NOTE Global horizontal irradiance, GHI usually takes into consideration the
albedo, although the albedo is often negligible in GHI.
(e) direct normal irradiance (DNI): irradiance received from a small solid angle
centered on the sun’s disc on a plane perpendicular to the sun’s rays
(f) in-plane irradiance, or plane of array irradiance (POAI): irradiance received
from the sun as a combination of direct normal irradiance and all forms of
diffuse light in the plane of the PV array
(g) integrated irradiance: continuously integrated spectral irradiance over a specified range of wavelengths