Status quo on recycling of waste crystalline silicon for photovoltaic modules and its implications for China’s photovoltaic industry

doi:10.1007/s11708-024-0923-y

2024, Vol. 18

Issue (5) : 685-698 https://doi.org/10.1007/s11708-024-0923-y

Status quo on recycling of waste crystalline silicon for photovoltaic modules and its implications for China’s photovoltaic industry

Yichen Zhou^1,², Jia Wen^1,²(

), Yulin Zheng^1,², Wei Yang^1,², Yuru Zhang^1,², Wenxing Cheng^1,²

¹. College of Environmental Science and Engineering, Hunan University, Changsha 410082, China
². Key Laboratory of Environmental Biology and Pollution Control of Ministry of Education, Hunan University, Changsha 410082, China

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Abstract

As a clean and efficient renewable energy source, solar energy has been rapidly applied worldwide. The growth rate of China’s installed capacity ranks first in the world. However, the life span of photovoltaic (PV) modules is 25 to 30 years, and the rapid development of installed capacity indicates that a large number of PV modules will be decommissioned in the future. Therefore, the ongoing treatment of the scrapped PV waste cells in the near future requires urgent plans and countermeasures. Proper recycling and disposal of decommissioned PV modules is a practical requirement for the sustainable development of the country and industry. Crystalline silicon (c-Si) solar cells currently occupy 85%–90% of the market share, and some scholars have begun to seek the utilization pathways of the waste Si in and outside the PV industry. In this paper, the research status of the separation and recycling process of crystalline Si PV modules is reviewed, and the recycling ways of crystalline silicon are particularly focused on. In addition, the current bottlenecks in the PV recycling industry in China are analyzed and some suggestions on the sustainable development of the PV industry are proposed.

Keywords waste photovoltaic (PV) modules crystalline silicon (c-Si) battery separation and recovery sustainable development

Corresponding Author(s): Jia Wen

Online First Date: 26 January 2024 Issue Date: 16 October 2024

Cite this article:

Yichen Zhou,Jia Wen,Yulin Zheng, et al. Status quo on recycling of waste crystalline silicon for photovoltaic modules and its implications for China’s photovoltaic industry[J]. Front. Energy, 2024, 18(5): 685-698.

URL:

https://academic.hep.com.cn/fie/EN/10.1007/s11708-024-0923-y
https://academic.hep.com.cn/fie/EN/Y2024/V18/I5/685

Fig.1 Installed capacity and growth of PV of countries and regions in the world.

Method	Critical process	Acquired materials	Results and comments	Ref.
Physical treatment
High-voltage pulse	First stage: 110 kV, 20 pulses;second stage: 90 kV, 250 pulses;dense medium separation	Glass;powder contains Si and metals	Ag was much condensed in the light product (sizes less than 20, 2.0–4.0, and 4.0–8.0 mm); product is a mixture	Akimoto et al. [20]
High-voltage pulse	160 kV, 300 pulses	Particles contain Si and metals	Cu, Al, Pb, Ag, and Sn are concentrated on the fractions under 1 mm;environmental-friendly;Hard to large-scale industrial recycling	Song et al. [21]
Hammering/cutting	Two-blade rotors crush;hammer crush	Glass	Around 85% (mass fraction) of the total panel weight can be recovered as glass form;a unique process line made up of conventional physical operations	Granata et al. [22]
Laser radiation	1064 nm optical-fiber pulsed laser	Ethylene-vinyl acetate (EVA) copolymer	Keep the solar cell undamaged;provide one effective way to remove the old EVA from the refurbishing region;High equipment requirements	Li et al. [23]
Thermal treatment
Direct pyrolysis	20 to 600 °C at 12.8 °C/min,600 °C for 30 min, air atmosphere	PV cells	complete degradation of the EVA;release dangerous metals (Cr, Pb) in the gas phase;ashes contain hazardous metals (Cr, Pb) and precious metals (Ag, Cu)	Tammaro et al. [24]
Direct pyrolysis	20 to 500 °C at a 10 °C/min,500 °C for 30 min, N₂ atmosphere	PV cells	Remove more than 99% of the polymers	Dias et al. [25]
Heat stripping	170 °C and mechanical force	EVA	Eco-friendly;no material degradation;No gas emission	Chitra et al. [26]
Two-step pyrolysis	300 °C, heat 30 min;400 °C, burn out 120 °C;	Glass;broken Si wafers;	Glass is completely recovered;produce noxious and harmful smokes	Wang et al. [27]
Two-step pyrolysis	150 °C for 5 min;500 °C for 1 h, N₂ atmosphere	Undamaged TPT (polyvinyl fluoride composite membrane) backing material, glass, and Si wafers	Recover full backboard;produce hydrocarbon compounds	Wang et al. [28]
Chemical treatment
Etching	HF, HNO₃, H₂SO₄, CH₃COOH	Si	Obtain Si with purity of 99.999%;Si recovery rate is 86%;Toxicity reagents	Kang et al. [29]
	HF, HNO₃	Si wafer	SiN_x, Ag, and Al are completely removed;toxicity reagents	Lee et al. [30]
	HF, HNO₃, CH₃COOH, KOH, Br₂	Si wafer	metal coating, the AR coating and the n-p junction were completely removed;Solutions need to be modified in accordance with the type of PV cells to be recycled;waste liquid needs further treatment	Klugmann-Radziemska & Ostrowski [31]
	HNO₃, NaOH, etching paste contains H₃PO₄	Si wafer	Recycled Si wafer is sufficient for current manufacturing processes for solar cells;minimize water consumption during the cleaning process and can eliminate the use of harmful surfactants	Shin et al. [32]
	HNO₃, KOH, H₃PO₄, 2-hydroxy-5-nonylacetophenone oxime	Si, Cu, Ag, Al, and Pb	Achieve recovery rates of 80%,79%, and 90% for Si, Cu, and Ag;Establish a sustainable system for recovering valuable elements	Jung et al. [33]
	HCl, TBP, 5-nonylsalicylaldoxime, 5-nonylsalicylaldoxime	Si, Ag, Cu, Sn, and Pb	Purities of final products are 99.84% for Si, 99.7% for CuO, 99.47% for PbO, 99.68% for SnO₂, and 98.85% for Ag;valuable materials are efficiently recycled	Chen et al. [34]

Tab.1 Major processing methods for recycling metal elements and Si from PV cells

Fig.6 Chemical process of Si cell purification. ARC: anti-reflection coating.

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