l
T = back-of-panel temperature ( °C)
l
T
0
=back-of-panel temperature at STC, typically 25 °C
l
α = temperature coefficient of short-circuit current
SLI uses the effective irradiances of a clean reference panel and a dirty test panel. It is defined as
Eq. 2
Where G
eff,Ref
is the effective irradiance calculated from the clean reference panel, and G
eff,Test
is
the effective irradiance calculated from the test panel.
8.3 Offset correction
PV panels often differ in power output under identical conditions, even when they are the same
model from the same manufacturing batch. This offset in power output can be determined upon
installation and updated after each cleaning of both panels. The offset correction is initiated by
pressing the Maintenance button for 5 s or more. The procedure determines the offset, and then
implements a correction factor into the measurement sequence to remove any effects that may
be caused by differences in panel power output under identical conditions. Carefully clean both
panels before initiating the offset correction process. Cleaning should be completed before 11
am.
NOTE:
Regardless of when the offset process is initiated, the offset will be updated at midnight on
the next day when the minimum number of data points required to calculate a good offset is
met.
After both panels are clean:
1. Press and hold the Maintenance button for a duration of greater than 5 seconds.
2. A variable named Update_Offset will be raised to 1. The time this button was pressed will be
recorded in the data table named offset.
3. Results will be available when the minimum number of data points has been met for
calculating a good offset value. This is typically midnight if the offset was initiated in the
morning, or midnight of the following day if the offset was initiated in the afternoon or
evening.
DustVue
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