Non-destructive methods for measuring photovoltaic modules are discussed in this paper, with the aim of comparing different quality-assurance methods for different module technologies (e.g. crystalline and thin-film technologies: a-Si, CdTe, CIS). For a complete quality control of PV modules, a combination of fast and non-destructive methods was investigated. In particular, camera-based measurements, such as electroluminescence (EL) and infrared (IR) technologies, offer excellent possibilities for determining production failures or defects in solar modules, which cannot be detected by means of standard power measurements. These methods are applied effectively in quality control and development support, and EL is already an important characterization tool in industry and research. Most short circuits reduce the voltage in their surrounding area and appear dark in EL images. However, as this failure is not always critical and apparent, short circuits are only precisely identifiable in combination with IR measurements. Therefore, to quickly detect at high resolution the most common defects in a PV module, a combination of EL and IR measurements is advisable.
Crystalline silicon solar modules installed in the field are exposed to atmospheric conditions and experience stress, which induces a wear-out phenomenon in various parts of the modules and degrades performance over time. The performance eventually reaches a point where the output power falls below an acceptable level. Thermal cycling (TC) and damp heat (DH) are two important reliability tests for estimating infant failures related to materials and the manufacturing process, as well as providing the information on performance degradation with respect to time. In this study, modules composed of 156mm × 156mm multicrystalline silicon cells were subjected to TC and DH tests. By applying acceleration models, such as the Norris-Landzberg model for TC and the Hallberg-Peck model for DH, the minimum guaranteed life was calculated. The electrical and reliability results were interpreted and explained on the basis of the respective models.
This paper presents a novel glue-membrane integrated backsheet specifically for PV modules, which has been designed and fabricated by utilizing a flow-tangent cast roll-to-roll coating process combined with a plasma technique. Polyethylene terephthalate (PET) is adopted as a substrate and is surface activated and etched by atmospheric plasma. Then a special coating formulation containing reactive fluoropolymers is applied to both sides of the PET, followed by thermal curing, resulting in a glue-membrane integrated coating layer with a polyurethane structure. Finally, a monolayer of silane molecules is grafted onto the surface via plasma-enhanced deposition to provide the surface medium with surface energy, rendering excellent long-term adhesion to ethylene vinyl acetate (EVA).
The improved performance and reduced manufacturing costs of photovoltaic (PV) modules that have been achieved in recent years have positioned this technology as an economically attractive renewable electric energy source. In order to verify that this also has a positive impact on energy payback time (EPBT) and carbon footprint, the Energy Research Centre of the Netherlands (ECN) has conducted a life cycle analysis (LCA) for REC Peak Energy-series PV modules produced by Renewable Energy Corporation (REC). The LCA study was based on a full set of actual production data obtained for the first quarter of 2011from REC’s manufacturing sites. Because REC is an integrated manufacturer, the LCA study includes internal data for the production steps from polysilicon production to module assembly, as well as for all materials and transportation associated with production. ECN used generic figures for installation, operations and recycling together with the REC data to assess the environmental impact indicators. For polysilicon produced in the USA, and for wafers, cells and modules produced in Singapore, an EPBT of 1.2 years was achieved, with a corresponding carbon footprint of 21g CO2-eq/kWh for PV systems located in southern Europe (1700kWh/m2year irradiation). For modules with wafers and cells produced in Norway, the corresponding values were 1.1 years and 18g CO2-eq/kWh. A key contributor in achieving these values is REC’s highly efficient fluidized bed reactor (FBR) process for the production of polysilicon.
Solar enterprises will each be faced with the occasional surplus or lack of solar modules in their lifetimes. In these instances, it is useful to adjust stock levels for modules at short notice, thus creating a spot market. Spot markets serve the short-term trade in different products, by enabling the seller to permanently or temporarily offload surplus, while buyers are able to access attractive offers on surplus stocks and supplement existing supply arrangements as a last resort.
This paper presents a new differential scanning calorimetry (DSC) method that allows the determination of the degree, or level, of crosslinking of ethylene-vinyl acetate (EVA) copolymers, including EVA films used as encapsulants for photovoltaic (PV) applications. This method can also determine additional characteristics of EVA, such as its weight per cent (wt %) vinyl acetate (VA) content and its fluidity. The paper describes the procedure and its application to EVA film samples laminated at 145°C, for different lengths of time in an industrial-type laminator for PV modules, as well as to EVA uncrosslinked samples of different composition and fluidity. The scope of the method compared to other characterization methods for the degree of crosslinking of EVA is discussed. An experimental comparison is also made to rheological and gel content methods.
Photovoltaic (PV) modules and components are products which have to withstand the diverse effects of extreme conditions during their lifetime. The wide range of climatic conditions and possible mechanical stresses must be taken into account when designing a PV component. To assess whether the quality of a product is sufficient to withstand such influences, some international standards have been developed. TÜV Rheinland operates several ISO 17025-accredited laboratories worldwide for type approval testing of PV components – such as junction boxes, connectors and cables – as well as concentrating PV modules, flat-plate modules and solar thermal systems. Experience of testing PV components has been gained over the last 12 years, and even over the last 20 years in the case of PV modules. New developments in photovoltaics mean that continuous development and review of standards is necessary.
This paper describes the technical concepts and current status of back-contact module technology. A back-contact module has the advantage of a higher conversion efficiency because of less shading of the front of the cell, fewer inactive areas in the module and lower series resistance in the interconnection. Aesthetically, back-contact modules are more attractive than standard modules. Furthermore, module manufacturing is gentler due to there being less cell handling during the process. The two main technical concepts related to back-contact modules – interconnector technology and printed circuit backsheet technology – are discussed in this paper. An overview is given of the production status of current back-contact module manufacturers to also show the significant potential of this technology in economic terms.
Solar enterprises will each be faced with the occasional surplus or lack of solar modules in their lifetimes. In these instances, it is useful to adjust stock levels for modules at short notice, thus creating a spot market. Spot markets serve the short-term trade in different products, where the seller is able to permanently or temporarily offset surplus, while buyers are able to access attractive offers on surplus stocks and supplement existing supply arrangements as a last resort.
By definition, PV module certification is simply based on conformance to standards. The IEC norms for PV modules are considered to be adequate quality requirements for guaranteeing initial quality. However, it is commonly understood that two products A and B may meet the standard’s requirements, but overall qualty – considering long-term stability, performance and safety – can still be quite different. PV module testing should therefore be carried out more frequently and beyond IEC requirements. A factory inspection once a year – as suggested by most certification bodies to ensure continuous quality of certified crystalline modules – may not be sufficient. The need for additional control is demonstrated in this paper, with reference to our experience from PV module testing and quality assurance activities for wholesalers and project developers. We present the necessity of additional measurements under standard test conditions (STC) and advanced testing methods, which are becoming essential for reliability.