Observed degradation in photovoltaic plants affected by hot‐spots

Abstract

A number of findings have shown that the test procedures currently available to determine the reliability and durability of photovoltaic (PV) modules are insufficient to detect certain problems. To improve these procedures, ongoing research into the actual performance of the modules in the field is required. However, scientific literature contains but few references to field studies of defective modules. This article studies two different localized heating phenomena affecting the PV modules of two large-scale PV plants in Spain. The first problem relates to weak solder joints whilst the second is due to microcracks on the module cells. For both cases, the cause is identified, and consideration is given with regard to the effect on performance, the potential deterioration over time, and a way to detect the problems identified. The findings contained in this paper will prove to be of considerable interest to maintenance personnel at large-scale PV plants and also to those responsible for setting module quality standards and specifications, and even the PV module manufacturers themselves.

Experimental observations on hot-spots and derived acceptance/rejection criteria

“…1 shows two infrared (IR) images of hot-spots. The anomalies that cause hot-spots can be external to the PV module: shading (Alonso- García et al, 2003;Herrmann et al, 1997;Molenbroek et al, 1991) or dust (Lorenzo et al, 2014); or internal: micro-cracks (Brun and Melkote, 2009;Buerhop et al, 2012;García et al, 2013;Grunow et al, 2005;Paggi and Sapora, 2013;, defective soldering (Buerhop et al, 2012;Chaturvedi et al, 2013;Gabor et al, 2006;García et al, 2013;Muñoz et al, 2008), potential induced degradation (Berghold et al, 2013;Hacke et al, 2010), material imperfections (Vasko et al, 2014). In general, a hot-spot entails a decrease of the operational efficiency of the PV module.…”

“…In general, a hot-spot entails a decrease of the operational efficiency of the PV module. Moreover, when a hot-spot persists over time, it entails a risk for the PV module's lifetime (Buerhop et al, 2012;García et al, 2013;Muñ oz et al, 2011;Osterwald and McMahon, 2009;Radziemska, 2003;Simon and Meyer, 2010;Soló rzano and Egido, 2014).…”

Output-Power Enhancement for Hot Spotted Polycrystalline Photovoltaic Solar Cells

“…The use of bypass diodes across PV strings is standard practice that is required in crystalline silicon PV panels [19]. Their purpose is to prevent hot spot damage that can occur in series-connected PV cells [20][21][22].…”

Contributions to uncertainty reduction in the estimation of PV plants performance

“…The IES-UPM played the role of independent experts at different stages of the projects: defining the initial production expectation, measuring PV modules and preparing some of them to act as reference modules in the field (to measure the operating conditions), and accomplishing the in-field measurements during the commissioning of the plant. Taking advantage of the previous IES-UPM knowledge and of this in-field work accomplished in the Spanish PV plants, numerous studies were published, facing the improvement of measurement procedures, the detection of early degradation phenomena and the development of proper indexes and methods to evaluate the initial state of health of PV installations (García, 2014) (Martínez-Moreno, 2012) (Martínez-Moreno, 2010).…”