10 Module Deployment and Energy Rating
281
(a)
(b)
(c)
(d)
Fig. 10.18 Measuring equipment for monitoring the irradiance various components: a pyranometer,
to detect the global irradiance; b pyrheliometer, to detect the direct irradiance; c albedometer, to
detect the albedo; d spectrometer, to detect the spectral irradiance
field of view) and a sun shield, to protect from solar radiation the inner part of the
thermopile, which remains in the dark and cold. With almost flat spectral response
(Fig. 10.5a), a pyranometer is able to detect practically all the spectrum of the solar
global irradiance, and its reading is substantially unaffected by temperature. If it is
placed in-plane with the module (via levelling feet), the reading of a pyranometer
gives directly the in-plane global irradiance G(t) as a function of time, with no need
of spectral corrections.
An alternative to the pyranometer is a photovoltaic reference detector, with one
advantage and some limitations. The advantage is a much faster response to changing
irradiance than a pyranometer that typically require 5–20 s to measure irradiance:
a PV detector instead has a response which is almost instantaneous. PV detectors
(usually c-Si) have also typically the same spectral responsivity as the PV modules installed and, thus, spectral mismatch corrections can be negligible. But their
Since this temperature difference is proportional to the irradiance absorbed by the black detector,
the pyranometer is calibrated to provide an accurate measurement of the global irradiance.
281
(a)
(b)
(c)
(d)
Fig. 10.18 Measuring equipment for monitoring the irradiance various components: a pyranometer,
to detect the global irradiance; b pyrheliometer, to detect the direct irradiance; c albedometer, to
detect the albedo; d spectrometer, to detect the spectral irradiance
field of view) and a sun shield, to protect from solar radiation the inner part of the
thermopile, which remains in the dark and cold. With almost flat spectral response
(Fig. 10.5a), a pyranometer is able to detect practically all the spectrum of the solar
global irradiance, and its reading is substantially unaffected by temperature. If it is
placed in-plane with the module (via levelling feet), the reading of a pyranometer
gives directly the in-plane global irradiance G(t) as a function of time, with no need
of spectral corrections.
An alternative to the pyranometer is a photovoltaic reference detector, with one
advantage and some limitations. The advantage is a much faster response to changing
irradiance than a pyranometer that typically require 5–20 s to measure irradiance:
a PV detector instead has a response which is almost instantaneous. PV detectors
(usually c-Si) have also typically the same spectral responsivity as the PV modules installed and, thus, spectral mismatch corrections can be negligible. But their
Since this temperature difference is proportional to the irradiance absorbed by the black detector,
the pyranometer is calibrated to provide an accurate measurement of the global irradiance.