ECN publication
Energy rating procedure voor PV-modules
Published by: Publication date:
ECN Energy in the Built Environment 1-10-2005
ECN report number: Document type:
ECN-C--05-097 ECN publication
Number of pages: Full text:
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The performance of PV-modules is usually characterized by the nominal power at standard test conditions. However more relevant for the end-user is the energy production. To arrive at a so-called energy rating procedure the P(Gi,Tm) matrix is defined, which makes it possible to calculate the expected annual energy production of a PV-module at any given location with known frequency distribution of horizontal irradiation and ambient temperature.

In order to make the de P(Gi,Tm) independent of the time and location of the tests the effective irradiation (Gi) is measured with a device with the same characteristics as the module under test. Such a device can be a suitable reference cell or, even better, the module under test itself. The latter, however, is only possible in case the module under test is stable in time.

Measurements were performed to test the applicability of the so-called self-reference for a-Si modules. Furthermore the difference between the effective irradiance and the real irradiance (measured with a pyranometer) was quantified for the test location Petten, the Netherlands.

The conclusions are:

·        Self-reference is not applicable for a-Si modules because of the time instability, even after 1 full year of degradation.

·        Self-reference signals (the short circuit current of the module under test) can be calibrated outdoor by comparison with a pyranometer at irradiance levels above 800 W/m2. The uncertainty of such a calibration is within 3%. The difference between the effective irradiance and the real irradiance on annual basis at Petten is virtually zero for x-Si modules and about 1% for a-Si modules.

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