Recovery of pure silicon from photovoltaic modules. Researchers checking the industrial application | Gdańsk University of Technology

Within the scope of a project funded from the VENTUS  program,  pre-implementation works will be performed to start the industrial process of recycling the monocrystalline and polycrystalline photovoltaic (PV) modules, obtained from end-of-life or damaged modules. Researcher plan to apply a PV module recycling method, developed in at the Department of Energy Conversion and Storage at the Faculty of Chemistry of Gdańsk Tech, which was patented in 2014. At the end of 2021, Gdańsk University of Technology granted an exclusive license to use the invention to a company that is an industrial partner in the project.

– We have developed a patent-protected method of extracting a silicon cell from a module, so that 99.99% pure silicon remains in the recovery process, and can be reused in the production of PV cells. Our technology is unique when it comes to pure silicon recovery. Currently, similar solutions are not mentioned in worldwide scientific publications, however international industry is working within that scope. According to available data, there is no company that recycles modules in Poland – says Prof. Ewa Klugmann-Radziemska, project manager and Director of the Industrial Doctoral School at Gdańsk University of Technology. – This project focuses on verification whether our technology, effective in the laboratory trials, will be similarly effective and profitable on a large scale.

Pure silicon in an hour, valuable aluminum

In simple terms, the photovoltaic module consists of an aluminum frame, glass, laminate, which is to protect the cells against the atmospheric factors and silicon cells.

– In order to release the cell, the layers that were applied in the technological process must be separated from the silicon substrate. We use the following processes: mechanical (removal of the aluminum frame), thermal (evaporation of the laminate in the pyrolysis process), and chemical. The chemical process itself is divided into two stages: using mixtures of bases and acids. All processes together take about an hour – says Prof. Klugmann-Radziemska.

If, for various reasons, it is not possible to recover the entire so-called of the silicon wafer, researchers will work on its fragments that can be used in the production of further PV cells. For this purpose, they will melt the silicon powder in the Czochralski furnace, so that after obtaining a silicon crystalline cylinder (almost free from defects), they can cut silicon wafers in order to use them in the photovoltaic industry and electronics.

– The production of high-purity glass, aluminum and silicon, i.e. materials used in the production of photovoltaic modules, are the most energy-consuming technologies in industrial production, therefore the use of recycled materials will significantly reduce the consumption of primary energy – emphasizes the project manager.

The research is part of the global model of the circular economy. Thanks to the solution, it will be possible to recycle modules at the level of 90% (including the recovery of aluminum and glass).

Guidelines for industrial application

The first large photovoltaic installations in Europe were built in the 1980s, and the average lifetime of the modules is approximately 25-30 years.

– Therefore, there is already a lot of photovoltaic waste in Europe, produced at time and factories. It will be necessary to accurately identify the materials used in the production of modules, including verifying what materials or metals were applied – says Prof. Klugmann-Radziemska.

In addition to identifying the composition of modules and research in the field of their preparation for delamination, researchers from the Department of Energy Conversion and Storage and the Department of Polymer Technology, as well as the Faculty of Mechanical Engineering and Ship Technology, will study the performance of mixtures used in chemical processes, emissions to the atmosphere and aspects related to resistance of machines to the used mixtures. The results of the research will constitute guidelines for the business plan and technological line for the industrial partner. Due to the thermal and chemical methods used, the industrial process will be closed and automated.