Preconditioning of thin-film PV module technologies for calibration

Abstract

Thin-film module technologies are known for their metastability, and a study of this behaviour for different types of thin-film modules is presented. The modules investigated through a series of controlled light-soaking procedures are copper-indium sulfide (CIS), copper-indium-gallium diselenide (CIGS), cadmium telluride (CdTe), triple-junction amorphous silicon (a-Si), micromorph silicon (a-Si/m-Si) and thin-film crystalline silicon (CSG). The objective of the paper is to investigate whether after the stabilization point, as defined in the international qualification standard IEC 61646, there is any further significant change in the maximum power of the module. It was found that all CIS and CIGS modules investigated in this study stabilize according to IEC 61646, and no further significant change in maximum power is observed. The same result was obtained also for the CSG module. To the contrary, CdTe, triple-junction a-Si and a-Si/m-Si modules continued to show further change in maximum power even after they stabilize according to IEC 61646. For the purposes of module qualification, given the need to stay 'within reasonable constraints of cost and time', the stability procedure of IEC 61646 could be considered as satisfactory. However, in order to perform sufficient preconditioning of thin-film modules prior to precision calibration, a new more complete standard procedure is needed, tailored to the specific technology. For example, tighter stability limits lower than the current 2%, which would have the effect of increasing the number of light-soaking periods required.

A simple approach to model the performance of photovoltaic solar modules in operation

“…Data for conventional a-Si and c-Si devices are taken from Martin and Ruiz (2001), being consistent with the one found in the literature for several other flat panel devices with conventional (un-textured) front glasses (International Electrotechnical Commission, IEC-61724:1998(E); Kenny et al, 2012;Virtuani et al, 2007). As Fig.…”

“…an intrinsic degradation/regeneration of the electrical properties of the semiconductor (typical of amorphous Si) promoted by exposure to light/thermal-annealing (Staebler and Wronski, 1977;del Cueto and von Roedern, 1999;Makrides et al, 2012;Nikolaeva-Dimitrova et al, 2008;Kenny et al, 2012).…”

PV technologies performance comparison in temperate climates

“…As is well known, amorphous silicon cells undergo a remarkable degradation process when the PV module is initially exposed to light (Light Induced Degradation -LID) (Kenny et al, 2014). The magnitude of this degradation is related to several factors, such as the a-Si layer thickness and the number of junctions, that may account for an initial power reduction between 15% and 35% (Fanni et al, 2011).…”

“…The published experimental research showed that the amount of energy needed to consider the amorphous silicon modules as stabilized must be higher than 400-500 kW h/m 2 (Kenny et al, 2014). For such reason, in this work before starting the monitoring phase all the products monitored were exposed, as a precaution, to outdoor conditions for a period of 12 months, corresponding to an irradiation of about 1400 kW h/m 2 .…”

Standardization of the energy performance of photovoltaic modules in real operating conditions

“…This is a quite surprising result if we consider that generally the performances of thin film devices are not stable due to the light soaking effect [10]. In fact, the module qualification procedure for thin film requires that the modules are preconditioned before any measurement [11].…”