Silicon photovoltaic modules at end-of-life: Removal of polymeric layers and separation of materials.

An eco-friendly process to recover valuable materials deriving from silicon based photovoltaic panels at end-of-life has been proposed. In particular, in this paper a new two-step process to separate and recover glass, Si and metals has been investigated and discussed. A preliminary mechanical treatment to remove fluorinated polymers allows to exclude dangerous emissions of hydrofluoric acid and fluorinated compounds coming out from conventional heat treatments. A subsequent thermal treatment allows the complete removal of the residual polymers and the separation of valuable materials. The influence of treatment time, temperature and atmosphere, during the polymers degradation has been evaluated and the by-products have been examined. The process efficiency has been assessed by determining the quantity and quality of the recovered materials. The results have shown that the combination of the two mechanical/thermal processes allows energy efficiency and environmental sustainability with respect to conventional recovery treatments. The optimal operating conditions for the thermal treatment have turned out 500 °C for 1 h in oxidizing atmosphere. The quality of the recovered materials has been determined by analysing the residual carbon content after the thermal treatment. The gaseous products of the polymeric degradation have been characterized by gas chromatography-mass spectrometry (GC-MS) analysis.

End-of-life of silicon PV panels: A sustainable materials recovery process.

In this paper, the management of end-of-life PV modules based on an advanced eco-sustainable process has been presented and discussed. The thermal removal of the polymeric compounds contained in c-Si PV modules has been investigated to separate and recover Si, Ag, Cu, Al and glass. A two-step thermal process has been employed. In the first step, the rear polymeric layer has been removed without emissions of dangerous fluorinated substances. In the second step, the remaining polymers have been completely removed with low volatile organic compounds (VOCs) emissions. The polymers degradation has been studied at combustion equivalent ratios Φ varying from 0.5 to 2 and at 500 °C. The materials recovery has been evaluated from an environmental point of view and optimized by considering the energy cost, through the identification of the best operating conditions, in terms of temperature, time, atmosphere and gas flow. One hour of heat treatment and a slightly oxidizing atmosphere have been enabled to separate and recover the different materials of the module. The elemental compositions of the PV sample and the residue condensed organic products have been determined. The gaseous degradation products have been characterized by gas chromatographic analysis (GC).