Abstract
The performance of a PV module at STC (1) is a useful indicator for comparing the peak performance of different module types, but on its own is not sufficient to accurately predict how much energy a module will deliver in the field when subjected to a wide range of real operating conditions (2). An Energy Rating approach has to be preferred for that aim. It is currently under development the standard series IEC 61853 on Energy Rating, for which only part 1 (3) has been issued. It describes methods to characterize the module performance as a function of irradiance and temperature. The reproducibility of the power matrix measurements obtained by the three different methods specified in the standard, namely: under natural sunlight using a tracking system; under natural sunlight without tracker; and a large area pulsed solar simulator of Class AAA were evaluated and discussed (4, 5). The work here presented is focused on the second method listed above, which explores the real working conditions for a PV device and therefore it represents the situation where Energy Rating procedures are expected to give the largest deviations from the STC predictions. The system for continuous monitoring of module performances, already implemented at ESTI, has been recently replaced with a new system having a number of improvements described in the following. The two system results have been compared showing a discrete compatibility. The two power matrices are then merged together using a weighted average and compared to those acquired with the other two remaining ideal systems. An interesting tendency seems to come up from this comparison, making the power rating under real operating conditions an essential procedure for energy rating purposes.
Highlights
Photovoltaic (PV) modules were first used for terrestrial applications in the 1970s
The performance of a PV module at Standard Test Conditions (STC) [1] is a useful indicator for comparing the peak performance of different module types, but on its own is not sufficient to accurately predict how much energy a module will deliver in the field when subjected to a wide range of real operating conditions [2]
The work here presented is focused on the second method listed above, which explores the real working conditions for a PV device and it represents the situation where Energy Rating procedures are expected to give the largest deviations from the STC predictions
Summary
Photovoltaic (PV) modules were first used for terrestrial applications in the 1970s. In the intervening decades order of magnitude improvements in performance have been made together with even greater reductions in cost, through improved manufacturing processes and introduction of new materials. Of great importance to these developments and for the commercial acceptance of PV have been the introduction of standards for the performance testing and reliability of PV modules. Manufacturers of PV modules currently provide a power rating (Pmax) at Standard Test Conditions (STC) according to IEC 61215 [1]. These conditions correspond to an irradiance level of 1000 Wm−2 at defined spectral irradiance distribution (AM1.5) and a module temperature of 25◦C [6]
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