Abstract
Crystalline silicon panels are the most widespread photovoltaic technology in the world. Solar modules installed globally reached a capacity of 940 GW in 2021, and according to reports from the International Energy Agency, this value is expected to increase to 5 TW by 2050. The life of a photovoltaic panel has a lifespan of around 25 years and since the first significant installations date back to the 2000s, within the next two years there will be tons of modules to dispose of.
A report co-authored by the International Energy Agency Photovoltaic Power Systems Program (IEA PVPS) and the International Renewable Energy Agency (IRENA) hypothesizes that by 2030 spent photovoltaic modules will amount to almost eight million tonnes, and by 2050 they could become about eighty. Mind-boggling figures! These are piles of blue panels as large as mountains destined for landfill, and they are numbers that tell us that behind the challenge of the energy transition lies another, that of the urgency of accelerating the development of effective methodologies capable of disposing of them and, above all, to recycle them. In Porto Marghera, in Venice, there are those who work effectively in this direction, and the experiments developed during years of research paint a scenario in which the exhausted module does not end up in waste, but is completely recycled and the noble elements of which it is compounds return to the supply chain as secondary raw materials.
New technologies for recycling exhausted solar panels
Solar panels… in the oven
«We are the only ones in Italy to have designed a system not only capable of recovering all the noble materials present in silicon-based photovoltaic panels, but also making them available for other applications with a very high level of purity». It is the voice of Pietrogiovanni Cerchier, the young founder of the innovative start-up 9-Tech in which nine people including engineers and researchers work.
He is working on an exhausted panel as he talks about the innovations contained in the process created by the company. He seems to be witnessing a sort of technological dissection: the photovoltaic module is placed on a table and dismembered to separate the different layers. With the exception of the frame, components and plastic supports, the remaining levels will be subjected to a high temperature thermo-mechanical treatment (more than 400 degrees centigrade) to carefully separate the individual materials, guaranteeing them a level of purity that allow reuse. «Our system is characterized by a belt oven and various separation screens, both of our invention, which allow us to recover the aluminium, glass, copper and, above all, the photovoltaic cells, that part of the panels that generates electricity when hit by the sun. It is a very thin layer composed of noble elements such as silver and silicon. When the panel arrives we dismantle it, insert it into the oven to free the components and treat the fumes generated. Everything then arrives in three separate machines that separate the glass, copper and photovoltaic cells. Silicon must be at least 98% pure to be reinserted into the supply chains and a further chemical step is necessary which allows us to purify it. We treat it with ultrasound in a solution with reagents with very low environmental impact, and thus manage to separate these two elements which are fused together».
With the “9PV” project, the 9-Tech start-up founded in 2021 has patented a thermo-chemical system for the recycling of photovoltaic panels at the end of their life which allows the recovery of all inorganic materials with superior yield and purity compared to treatments, solely mechanics, employed for this type of activity. On an industrial scale, in fact, mechanical delamination is the most used method today for the disposal of solar panels. It consists of a downcycling process which involves the complete grinding of the module and the sorting of the materials obtained. The process recovers aluminum from frames and glass and copper granules after sifting the panel reduced to crumbs. The glass is recycled but the remaining dust which also contains silicon and silver is sent to landfill or used for low-value applications. It is an economical and rapid approach but it is not capable of valorising the silicon or silver because they are contaminated by the dust generated by crushing. In a photovoltaic module, in fact, the silicon cells are grouped in a very fragile sheet and shredding drastically reduces their purity, economic value and the possibility of using it as a secondary raw material. The approach pioneered by 9-Tech, however, is oriented from the perspective of upcycling, of improving the quality of noble materials through a transversal method that combines thermal, mechanical and chemical treatments for the correct separation of the elements. «On an industrial scale, no recycling line is currently capable of adequately recovering the materials encapsulated in the modules. The main technical challenge is precisely that of adequately separating these materials, each of which, if recovered with high purity, has a resale value capable of financing the entire recycling activity” explains Cerchier.
Thanks to this research, the Venetian start-up won the “In action ESG Climate” award in 2022, the call for innovative and sustainable entrepreneurship from the Intesa San Paolo group which is among the main financiers of the futuristic project set up by the start-up.
PV Lighthouse: Workflows automated by artificial intelligence
The possibility of giving a new perspective to the materials present in electronic devices is an impulse that has accompanied the founder of the company since he was at school and has today become the ethical urgency that guides 9-Tech’s work: «I have always had interest in recovering materials from waste. I have never accepted the idea that a television, a broken computer or a simple obsolete memory bank end up in the garbage without doing something else with it. My degree thesis focused on the recovery of gold from electronic cards and during my doctorate I specialized in the recycling of strategic elements from waste by doing research on different types of materials including the silver present in photovoltaic cells. Subsequently, with the metallurgy group of the University of Padua I followed the ReSiELP project (Recovery of Silicon and other materials from End-of-Life Photovoltaic Panels) supported by the European Institute of Innovation and Technology (EIT Raw Materials), the who financed the first prototype of the oven» says Cerchier. The 9-Tech experimental plant is located in the industrial area of Fusina, in the municipality of Marghera, and operates within the Green Propulsion Laboratory of the Veritas group, a platform financed by the Ministry of the Environment and the municipality of Venice for the ecologic relaunch of Porto Marghera, which invents new green technologies and is an incubator for various start-ups committed to the environment.
The team operates in a container of approximately twenty-five square meters in which the special belt oven at the center of the company’s patented methodology was built. It is crowded with bins containing the material recovered during the experimentation. There is barely space to move, yet in this narrow white parallelepiped a decisive intuition has taken shape for the business models that make photovoltaics the key resource for the energy transition. The plant was authorized by the Veneto Region in July 2022 and to date approximately 1500 kg of panels have been recycled. The pilot plant has proven to have very high energy efficiency and the ability to recover materials in a sufficiently pure form to be reused as a secondary raw material.
Thanks to the good results obtained and the partnership with companies such as Veritas and Haiki, a new structure will be built, again in Porto Marghera, which will replicate the process on an industrial scale. «The new PV Lighthouse installation will be completed by 2025 and is co-financed by the PNRR as a “flagship” circular economy project. The operational flow of will be completely automated thanks to artificial intelligence systems capable of recognizing the shapes, types and direction of the panels. The design of the plant, which will treat three thousand tons per year, has already been completed and we are preparing the documentation to obtain the authorizations» specifies Alberto Nalon, the environmental engineer who is working on the industrial conversion.
Anatomy of photovoltaics: a blue mine
Solar panels are made up of layers of different materials. The frame that covers and guarantees robustness to the device is made of aluminum and represents approximately 16% of the total weight of a panel. The surface is made of glass, a material that protects and provides rigidity to the module while ensuring high transparency at the same time. This fraction is the most significant in terms of mass as it constitutes approximately 65% of the weight of the element. Below there are the photovoltaic cells, the energy core of the device: they capture solar radiation, transform it into electricity and give the module the unmistakable blue color that characterizes it. They are made of silicon and although they constitute only 3% of the weight of a module, they represent the most critical material. The electrical charges generated by the blue plates are collected and directed towards the conductors through the silver found on the front surface of the cell in the form of silk-screened contacts. Although the quantity present in a module is minimal (approximately 10 g), it constitutes more than 40% of the value of all the materials contained. Finally there are the copper contacts (1% weight) that connect the different cells to each other and the junction box (2%), made up of plastic and copper cables, which connects the module to the external electrical circuit.
«A photovoltaic panel at the end of its life still has a lot to give: it can be considered a small mine of precious elements» explains Francesco Miserocchi while he is working in the start-up’s chemical laboratory. «In addition to the glass and aluminum that can be recovered in large quantities, one ton of disused photovoltaic modules contains approximately thirty kg of very high purity metallic silicon, a material considered critical by the European Union, ten kg of copper and approximately half a kilo of silver. Recovering these metals from waste also represents a significant environmental benefit, considering the enormous energy consumption necessary for their extraction from virgin ore and the resulting pollution. The concentration of silver, in fact, is three times higher than that present in mines. With the same mass, there is more silver in the photovoltaic modules than in the mines from which it is extracted: from a ton of panels you can obtain around 500 g of silver while from a ton of raw material you can get around 165 g».
The recovery of critical and noble materials from panels that have reached their expiry date does not represent an advantage only in terms of environmental impact, but also becomes central on a strategic and economic level. The demand for components recovered from photovoltaic modules is set to skyrocket in the coming years, as the number of installations will increase to meet the needs of the energy transition and the threat of a bottleneck in the supply of raw materials could loom, especially for silicon produced largely in China and other countries outside of Europe. An analysis published in late 2022 by Rystad Energy – the most important independent energy research body in Finland – hypothesizes that recyclable materials from spent panels will be worth more than $2.7 billion in 2030 and will be close to $80 billion. dollars by 2050.
Parsival: an Italian-led European network
The model finalized by 9-Tech appears to be particularly promising both in terms of productivity and effectiveness, and for the significant saving of mineral resources. Although there are numerous industrial companies that carry out photovoltaic disposal (companies authorized to recycle glass or treat WEEE waste, for example), in the world those that have consolidated innovative methods for recovering waste can be counted on the fingers of one hand. critical elements with a degree of purity that can be used again in the electricity or energy sector.
Now the Venetian start-up is facing new challenges: on the one hand industrializing the large-scale recycling plant and on the other, as part of European research projects, verifying the performance of the recovered materials for various applications such as the production of new photovoltaic cells, lithium ion battery anodes or silicon ferroalloys. The goals achieved thanks to research applied to the recovery of critical materials, in fact, have paved the way for a new project called Parsival (Panels Recycling to create Silicon Value chain) where the Venice start-up leads and coordinates a team multidisciplinary project made up of nine partners from four European countries (Italy, France, Germany and Spain). Funded by EIT RawMaterials – a body of the European community promoting the correct management of raw materials – Parsival is a RIS capacity building project that is creating a network of European actors operating in the reuse of materials obtained from spent panels, in particular silicon.
