Evolutions in the contexts of transportation, industry, and energy have occurred over the past decade, and even greater change can be expected in the coming years. From renewable energy to electric cars, big changes in technologies bring evolutions in components, and recycling of derived waste presents increasingly complex and intricate challenges, both from the standpoint of regulatory regulation and from an environmental perspective. Although many steps have been taken both in Europe and globally to reduce sources of waste and pollution,companies, especially small ones, face quite a few major issues in maintaining economic balance. For example, the GHG Protocol developed by international bodies (WRI and WBCSD) identifies the logistical and treatment sources of materials at the end of their life cycle (defined as "Scope 3") as the main contributor to de facto pollution and GHG emissions in all companies active in every industrial sector and beyond. Choosing to recycle materials instead of simply "disposing" them into the environment is a process that is not easy but nevertheless has countless benefits not only in terms of image but also in economic terms.
Recycling photovoltaic panels
A prime example of the issue of the importance of recycling is given by the recovery of disposed PV panels.
In this context, the explosion in the use of PV as a clean source of energy is already bringing significant challenges in the disposal of discarded panels due to the presence of impurities (semiconductors such as arsenic, cadmium, tellurium, and lead). Given that the estimate is that by 2050 10 percent of waste material will consist of material from photovoltaics and solar, preparing appropriate strategies for the valorization of such waste is a determining factor. Further compounding the problem is that second-generation panels, such as thin-film technology, have a different chemical and physical structure, which makes their recycling even more complex. The importance of the mechanical separation processPhotovoltaic cells consist of semiconductors and contain impurities. Being able to obtain material of sufficient quality for recycling is a difficult task not only in solar/photovoltaic but also in WEEE recycling in general. The chemical processes so far developed require huge economic resources in terms of machines and energy, as well as involving the use of toxic and polluting solvents and catalysts.
The mechanical recycling process for photovoltaic panels is the one that yields materials that are attractive to be recycled for a better cost-benefit ratio:
- Aluminum, with high value for industry, from automotive application to plant engineering
- Glass, which can be reused in bottle production or other areas (e.g., metallurgy)
- EVA (ethylene vinyl acetate), globally useful as fuel or in infrastructure
- The high-value copper in the electrical industry and beyond
Considering also that chemical treatments can often take place from mechanical shredding, it seems clear that in the long run this will be the main process of recycling not only in the photovoltaic field but also outside, as in the recovery of electronic materials or batteries. Further advantage of mechanical recycling plants for spent PV panels is their low cost, ease of maintenance and reliability.
The crushing and separation process
The typical mechanical process of a decommissioned panel treatment equipment can be schematized as follows:
The shredder
The panel, once electrical components such as cables and splices have been removed, is fed into a shredder where an initial coarse grinding takes place to separate out the coarsely sized aluminum. The aluminum thus obtained can be separated directly with excellent purity and resold.
The shredder is equipped with replaceable inserts with varying sizes according to process requirements.
The delaminating mill
The remaining material, consisting of glass, metals, EVA (polymeric material used for adhesion of photovoltaic cells to the substrate) and low concentrations of semiconductor is then fed into the heart of the plant, the horizontal delaminator mill (M series). This machinery is equipped with a rotor with high-density, high-hardness steel blades capable of crushing the pezzato to grains as small as 2 mm in the case of more brittle material (e.g., glass), coarser in the case of plastic or ductile material. In fact, the latter tends with its physical characteristics to agglomerate and form thicker grains of excellent percentage of purity.
The conformation of the channel through which the material to be shredded passes allows selective grinding depending on the material, which follows different trajectories according to the mechanical characteristics of the particle, and makes it possible to separate the plastic part from the heavier and more fragile part already at this stage. The glass obtained from delamination comes in the form of spheres and granules of two size classes, the first coarser but with higher purity and the second with an acceptable concentration of impurities within the framework of EU regulations.
The strength of the delaminator mill lies in the fact that the production of metallic material powders with consequent losses in efficiency are minimal.
Together with the inverter power supply, the speed of the rotor can be adjusted according to the requirements of the processed material, and the fact that it is constructed of material with high mechanical strength facilitates the task of operational flexibility and variability of the type of product to be processed.
The classification of the output material
The final step in the recycling of spent PV panels is the screening and classification of the fractions coming out of the vertical mill. A densimetric table (VT series) is usually used to separate the material according to its specific gravity.
The powders are conveyed from above, and with an airflow from the bottom, the heavier fractions tend to fall following an almost vertical trajectory, while the light fractions are separated.
Another popular technology for separation is the optical sensor (OS series), which separates material by color, on par with the human eye.
Conclusion
In the context of renewable energy, being able to reduce emissions and waste is crucial not only ecologically but also economically.
However, expensive, state-of-the-art installations are not always the best and most effective solution. Delicate equipment, toxic substances and consumption mean that the choice is based on considerations related to the efficiency and convenience of the recycling plant.
The M horizontal delaminator mill makes it easier to separate materials on an ongoing basis
The mechanical process makes it possible to recover materials from photovoltaic panels and frames so that the output material is attractive for re-entering the market instead of being disposed of.
Stokkermill with its offer of reliable machines entirely manufactured in Italy allows to combine quality, reliability and convenience to equip in total safety in a rapidly changing context, such as the recycling of decommissioned photovoltaic panels. The service goes beyond simple machinery: the offer includes plants designed ad hoc according to the customer's needs, taking into account the needs to interface with operators and the constraints imposed by regulations and legislations.
Easily interfacing with the needs of each company in the sector thanks to the delamination and shattering of the panel and photovoltaic cells.
