Photovoltaic solar panels of crystalline silicon: Characterization and separation

Abstract

Photovoltaic panels have a limited lifespan and estimates show large amounts of solar modules will be discarded as electronic waste in a near future. In order to retrieve important raw materials, reduce production costs and environmental impacts, recycling such devices is important. Initially, this article investigates which silicon photovoltaic module's components are recyclable through their characterization using X-ray fluorescence, X-ray diffraction, energy dispersion spectroscopy and atomic absorption spectroscopy. Next, different separation methods are tested to favour further recycling processes. The glass was identified as soda-lime glass, the metallic filaments were identified as tin-lead coated copper, the panel cells were made of silicon and had silver filaments attached to it and the modules' frames were identified as aluminium, all of which are recyclable. Moreover, three different components segregation methods have been studied. Mechanical milling followed by sieving was able to separate silver from copper while chemical separation using sulphuric acid was able to detach the semiconductor material. A thermo gravimetric analysis was performed to evaluate the use of a pyrolysis step prior to the component's removal. The analysis showed all polymeric fractions present degrade at 500 °C.

Assessment of the energy recovery potential of waste Photovoltaic (PV) modules

“…Due to the strong bonding capability of the EVA encapsulant in the solar cell, it was impossible to separate the layers cleanly at room temperature and so, a well-controlled thermal process was used. The thermogravimetric analysis (TGA) results of the decomposition of EVA and the PV backsheets confirmed that the thermal process employed did not exceed or operate near decomposition temperatures so as not to alter the overall structure of the EVA and backsheet layers 65,66 . Following extensive testing, it was determined that the solar cells were to be added to a genlab oven for 10 minutes at 190 °C for optimum results in removing the polymeric material by softening some of the polymers in the laminate structure.…”

Use of SnOx:F in the Recycling of Silicon Solar Cells

“…The X-rays diffraction and fluorescence analysis have been used to identify the components of photovoltaic modules made with silicon cells 1,2 . Figure 3 shows the X-rays diffractograms for samples with and without antireflection layer, respectively.…”

“…Amongst the photovoltaic technologies, the silicon semiconductor has dominance on the market; however, its limited lifetime means that silicon photovoltaic modules will become electronic waste 1 . The recycling of photovoltaic modules is important for the recovery of materials, reduction of costs and environmental impacts.…”

Development of recycling techniques in 1st and 2nd generation waste photovoltaic panels

“…conventional resources such as glass, Al, plastic, as well as valuable metals (Ag, In, Ga, Te, etc. ), whereas the latter have been recently determined to be at near-critical supply risk (Dias et al, 2016a). Instead, sound recycling processes can play a key role in protecting the environment by reducing the risks pertinent to hazardous substances such as toxic metals, poly/brominated flame retardants, etc.…”