Chemical treatment of crystalline silicon solar cells as a method of recovering pure silicon from photovoltaic modules (original) (raw)
Related papers
Pure Silicon Recovering from Photovoltaic Modules
Advances in Materials Sciences, 2008
Photovoltaic technology is worldwide used to provide reliable and cost-effective electricity for industrial, commercial, residential and community applications. The average lifetime of PV modules can be expected to be more than 25 years. The disposal of PV systems will emerge as a problem, considering the still increasing production of PV modules. Recycling of such modules can be done at about the same cost level as its disposal. Recovering the pure silicon from damaged or end-of-life PV modules can lead to economical and environmental benefit. Chemical treatment conditions need to be precisely adjusted in order to achieve the required purity level of the recovered silicon. For crystalline silicon based PV systems, a series of etching processes has been carried out as follows: electric connectors (etching or removing), ARC and n-p junction etching. The chemistry of etching solutions was individually adjusted for the different silicon cell types. Efforts were taken in order to formulate a universal composition of etching solution.
Experimental validation of crystalline silicon solar cells recycling by thermal and chemical methods
Solar Energy Materials and Solar Cells, 2010
In recent years, photovoltaic power generation systems have been gaining unprecedented attention as an environmentally beneficial method for solving the energy problem. From the economic point of view pure silicon, which can be recovered from spent cells, is the most important material owing to its cost and limited supply. The article presents a chemical method for recycling spent or damaged modules and cells, and the results of its experimental validation. The recycling of PV cells consists of two main steps: the separation of cells and their refinement. Cells are first separated thermally or chemically; the separated cells are then refined. During this process the antireflection, metal coating and p-n junction layers are removed in order to recover the silicon base, ready for its next use. This refinement step was performed using an optimised chemical method. Silicon wafers were examined with an environmental scanning electron microscope (ESEM) coupled to an EDX spectrometer. The silicon wafers were used for producing new silicon solar cells, which were then examined and characterized with internal spectral response and current-voltage characteristics. The new cells, despite the fact that they have no SiN x antireflective coating, have a very good efficiency of 13-15%.
Materials
As the use of photovoltaic installations becomes extensive, it is necessary to look for recycling processes that mitigate the environmental impact of damaged or end-of-life photovoltaic panels. There is no single path for recycling silicon panels, some works focus on recovering the reusable silicon wafers, others recover the silicon and metals contained in the panel. In the last few years, silicon solar cells are thinner, and it becomes more difficult to separate them from the glass, so the trend is towards the recovery of silicon. In this paper, we investigate the experimental conditions to delaminate and recovery silicon in the recycling process, using a combination of mechanical, thermal, and chemical methods. The conditions of thermal treatment to remove the ethylene-vinyl acetate (EVA) layer were optimized to 30 min at 650 °C in the furnace. To separate silicon and metals, the composition of HF/HNO3 solution and the immersion time were adjusted considering environmental aspects...
Recovery of Pure Silicon and Other Materials from Disposed Solar Cells
International Journal of Photoenergy, 2021
The disposal of used photovoltaic panels is increasing day by day around the world. Therefore, an efficient method for recycling disposed photovoltaic panel is required to decrease environmental pollution. This work is aimed at efficiently recovering pure silicon and other materials such as aluminium, silver, and lead from disposed solar cells using chemical treatments. Earlier, the pure silicon was recovered by treating the solar cells with hydrofluoric acid or mixture of hydrofluoric acid and other chemicals. The usage of hydrofluoric acid is eliminated in the present work as it is highly toxic and corrosive chemical. The pure silicon (99.9984%) has been recovered by sequentially treating with three different chemicals. Aluminium, silver, and lead are also recovered as aluminium hydroxide, silver chloride, and lead oxide, respectively.
Recycling of Raw Materials, Silicon Wafers and Complete Solar Cells from Photovoltaic Modules
Journal of Solar Energy Research Updates, 2016
Photovoltaic modules (PVs) are an attractive way of generating electricity in reliable and maintenance-free systems with the use of solar energy. The average lifetime of photovoltaic modules is 25 to 30 years. To offset the negative impact of photovoltaic modules on the environment, it is necessary to introduce a long-term strategy that includes a complete lifecycle of all system components from the production phase through installation and operation to disposal. Recycling of waste products and worn-out systems is an important element of this strategy. Environmental benefits of recycling are related not only to the limited space of landfills, but also to energy saving, raw materials and emission reduction. An important argument for the recycling of photovoltaic modules is the reduction of energy consumption at their production stage through the reuse of existing purified materials. The paper presents selected methods of recycling of used or destroyed PV modules and photovoltaic cells and the results of practical experiments.
Silicon photovoltaic modules at end-of-life: Removal of polymeric layers and separation of materials
Waste Management, 2019
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.
Recycling of solar cell silicon scraps through filtration, Part I: Experimental investigation
Solar Energy Materials and Solar Cells, 2008
This study investigated the removal of SiC and Si 3 N 4 inclusions from top-cut solar cell silicon scraps by filtration with foam filters. Laboratory experiments tested various models for the removal mechanism of inclusions and the efficiency of ceramic foam filters. Inclusions in solar cell silicon top-cut scraps were mainly needle-like Si 3 N 4 particles and lumpy SiC inclusions. SiC and Si 3 N 4 inclusions sometimes agglomerated as clusters. Si 3 N 4 inclusions were usually more than 500 mm long with diameters of $20 mm, and SiC inclusions were usually smaller than 500 mm. After filtration, no Si 3 N 4 inclusions were found. The remaining inclusions were mainly SiC inclusions smaller than 10 mm. Filters with smaller pores improved the removal of inclusions. It was discovered that contamination of the silicon may occur from components of the filters themselves, especially from binders. The crucible was also a source of contamination. A filtration process that does not produce contamination of its own should be developed before being used in real industrial processes. Mechanisms for the removal of inclusions from silicon through filtration are as follows: (1) cake filtration, for the removal of large Si 3 N 4 rods and large SiC inclusions; (2) deep-bed filtration of smaller Si 3 N 4 inclusions and most SiC particles; (3) formation of large SiC clusters and bridges across pores, and (4) silicon dissolution into carbon filters, and a subsequent reaction to form layers of SiC.
End-of-life of silicon PV panels: A sustainable materials recovery process
Waste Management, 2019
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 U 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).
Solar Energy and Sustainable Development Journal
As an alternative to the wet chemical etching method, dry chemical etching processes for Phosphorus silicate glass (PSG) layer removal using Trifuormethane /Sulfur Hexafuoride (CHF 3/SF6) gas mixture in commercial silicon-nitride plasma enhanced chemical vapour deposition (SiN-PECVD) system is applied. T e dependence of the solar cell performance on the etching temperature is investigated and optimized. It is found that the SiN-PECVD system temperature variation has a significant impact on the whole solar cell characteristics. A dry plasma cleaning treatment of the Si wafer surface after the PSG removal step is also investigated and developed. The cleaning step is used to remove the polymer f lm which is formed during the PSG etching using both oxygen and hydrogen gases.By applying an additional cleaning step, the polymer film is deposited on the silicon wafer surface after PSG etching is eliminated. T e effect of different plasma cleaning conditions on solar cell performance is inv...
Innovative recycling of end of life silicon PV panels: ReSiELP
Detritus
In Europe, an increasing amount of End of Life (EoL) photovoltaic silicon (PV) panels is expected to be collected in the next 20 years. The silicon PV modules represent a new type of electronic waste that shows challenges and opportunities. ReSiELP was a European project that aimed at recovery of valuable materials (aluminum, glass, copper, silicon, and silver) from EoL silicon PV modules. During the project a pilot plant, constituted by a furnace, a gas abatement system, an apparatus for the mechanical separation and a hydrometallurgical plant was designed and built. The pilot plan was realized to upscale recycling technology to TRL 7, with a 1500 panels/year capacity. The feasibility of industrial-scale recovery and the reintegration of all recovered materials in their appropriate value chain was investigated. The results obtained showed that 2N purity silicon and 2N purity silver can be recovered with high efficiency. In order to realize a zero-waste plant, a hydrometallurgical p...