Field of technology

The invention relates to a method and a line for recovering components from discarded photovoltaic panels that can be reused in the manufacture of new photovoltaic panels or in other products with minimal effort and emissions.

State of the art

Once the photovoltaics panels (abbreviation “PV” panel) of a solar power plant have reached the end of their useful life, either through age or external factors, they are replaced by new PV panels at the solar power plant without much delay, after which the discarded PV panels are sent for recycling as electrical waste.

In the framework of the legislatively mandated recycling of e-waste, the individual components of recycled e-waste are separated into reusable raw materials and unusable residual waste that can be landfilled. Since the primary objective is to recover the raw material for reuse, recycled e-waste is generally subjected to destruction into small particles. Unfortunately, the raw materials thus obtained from recycling, especially if they are not metals that can be remelted relatively easily, are often considered to be of lower quality, e.g. with contaminating impurities, so they are recovered in applications and production where the impurity-reducing impurity of the raw material does not matter, while new electrical products are generally made from newly prepared raw materials without impurities, contamination, etc.

The above-mentioned fact on recycling of e-waste to obtain raw materials for further use also applies to photovoltaic panels, which are approximately 70% made of tempered glass, and approximately 20% made of aluminium, while the last 10 % or so of the PV panel is made up of plastic components, adhesives, plastic cover sheets, plastic cover plates and PV cells made up of electrically conductive copper tracks and arrays of silicon-based semiconductors forming the solar cells. As far as the disassembly of the PV panels is concerned, it is disadvantageous that the PV panel assembly is held very tightly together, especially when it is a layered structure arranged on tempered glass, and furthermore when it is an aluminium frame which protects the layered structure lying on the tempered glass from the sides and provides it with a firm support. The layered structure is fixed to itself by the adhesion of the individual surfaces, with the use of adhesive means in the area of the aluminium frame or the melting of plastic parts. This fact makes the process of dismantling the PV panel into raw materials very complicated, since mechanical dismantling causes the tempered glass to crack and break into shards with individual fragments of the layered structure that are almost inseparable from the shards. Mechanical dismantling produces a large amount of waste that is difficult to reuse in the form of dirty shards, especially as around 70 % of the PV panel is tempered glass.

The problem of shards with remnants of the layered structure is solved by the invention of KR 102 283 519 Bl, which mechanically casts an aluminium frame from the laminated structure of a photovoltaic panel, then crushes the tempered glass with the layered structure and, by successive heating of the tempered glass shards, breaks the layered structure into individual components, which themselves detach from the tempered glass by heat. Although the known invention appears to be a suitable solution from a recycling point of view, as it cleanly separates the individual raw materials from the PV panel which can be sent for further processing, its main disadvantage is the destruction of the tempered glass and aluminium frame into a mould suitable only for energy-intensive remelting, while new raw materials and semifinished products must be energy-intensive to produce new PV panels.

The aim of the invention is to create a method and a line that would allow to recover from discarded photovoltaic panels mainly reusable components, not only raw materials. The invention would thus save the environment, as it would not only enable the waste to be processed, but would also save energy and material in the production of new components or in the processing of the recovered components into new products. In addition, the invention should be very environmentally friendly with a minimised emission footprint.

The summary of the invention The problem is solved by a method for extracting reusable components from photovoltaic panels and a line for carrying out the method according to the invention described below.

The essence of the method for extracting reusable components from photovoltaic panels, in particular for use in the manufacture of new photovoltaic panels, is that first, in process step a), the aluminium frame is cut off from the tempered glass with the adhered layered structure by a beam. Advantageously, the beam cutting process is gentle both to the aluminium frame and to the tempered glass, so that the aluminium frame is not deformed by force, as is the case, for example, in the known invention of the prior art, and the tempered glass is not damaged in any way, but on the contrary, has straight and smoothly sculpted edges by the beam. Moreover, when the beam is used to cut off the aluminium frame, the tempered glass is obtained in a new size format, or in several size formats if it is cut into several parts with a smaller area.

During the tempered glass cutting process, the aluminium frame is cut into individual aluminium profiles from which impurities are subsequently removed, making the aluminium profiles ready for reuse without the need to re-process the aluminium by melting and extruding it into new aluminium profiles. This is very advantageous, as aluminium processing is a very energy-intensive operation, whereas cleaning existing aluminium profiles is incomparably more economical and environmentally friendly.

Next, the layered structure is removed from the tempered glass, after which the tempered glass surface is re-polished to remove defects caused, for example, by the careless storage of discarded photovoltaic panels.

The invented method is advantageous in that it economically and environmentally without unnecessary hazardous emissions obtains reusable components that make up nearly 90% of the newly manufactured photovoltaic panel, thus saving time, energy and natural resources. Moreover, the components thus obtained can be used in other areas of human activity.

From the point of view of the inventive method, it is advantageous if a laser beam or a water beam with an abrasive is used in step a). Both the laser beam and the water beam can cut the old PV panels well, as has been shown in practical tests. Preferably, the waterjet with abrasive was shown to have a completely negligible side effect on the quality of the extracted components from discarded solar panels, compared to tests with conventional cutting tools and with the laser beam. The water beam does not heat up the cutting area and is also completely inert to reflective tempered glasses, which proved to be very dangerous for laser cutting as they reflected the laser beam.

Further, it is advantageous from the point of view of the inventive method if the residues are removed mechanically as part of process step (c). The aluminium profiles are not substantially damaged if they are run over with brushes or scrapers to remove adhesive residues, etc. Preferably, the aluminium profiles and the residues adhering to them can first be heated to a temperature of 270 °C to prevent oxidation of the plastics and adhesives and the production of polluting flue gases. The heat will soften the plastics. In addition, the different thermal expansion of aluminium and the materials forming the residue can help to peel the residue from the aluminium profile even with moderate heating. Sandblasting has proven to be an advantageous mechanical removal method, using a stream of very fast-moving abrasive particles to remove adhesive residues, grease, dirt, etc.

Further advantageously, the inventive method wherein the layered tempered glass is cooled with liquid nitrogen in process step d). The production of liquid nitrogen is cheaper in terms of energy consumption than heating. In addition, nitrogen makes up the vast majority of the air, so its use is compliant with emission regulations as no gaseous waste products are produced as in processes using decomposition by heating. As soon as the cold of the liquid nitrogen hits the first layer of the layered structure, in particular the covering plastic film, the film will spontaneously roll up, thus tearing itself off. In this way, the majority of the layered structure reacts, or at least peels off enough that the remainder of the layered structure can be mechanically separated without much effort. Moreover, the subcooling caused by nitrogen does not affect the quality of the tempered glass to any great extent.

Advantageously, the subcooling of the layered structure makes the plastics so low temepratured that it is possible to sort out the plastics from the metal and semiconductor photovoltaic cells from the remnants of the layered structure. Such clean residual waste without the use of burning and chemistry has not yet been recovered from solar panels when they are recycled. The invention also includes a line for extracting reusable components from photovoltaic panels, which is carried out in a manner according to the above inventive method. The essence of the inventive line is that it comprises a station for cutting the aluminium frame from the tempered glass with a layered beam structure.

Further, the line according to the invention includes a station for dividing the aluminum frame into aluminum profiles, that further includes a station for cleaning the aluminum profiles, that further includes a freezing station for separating the layered structure from the tempered glass by cooling, and that further includes a station for polishing the surface of the tempered glass.

Among the advantages of the line according to the invention is the simplicity of the arrangement of the stations, where each station is equipped with a device to perform a particular step of the method. In particular, the innovative features of the line for extracting components from discarded photovoltaic panels are the separation of the aluminium frame from the tempered glass by means of beam cutting, as well as the cooling of the layered structure instead of the established thermal processes, which is more economical and environmentally friendly in comparison.

It is advantageous if the inventive line has a clay frame cutting station equipped with a laser cutting device or a waterjet cutting device with an abrasive. Both types of beams have proven to be sufficiently effective, but the water beam has proven to be ideal as it does not cause thermal shock and does not react to the optical reflectivity of the tempered glass.

It is further advantageous if the inventive line has a station for cleaning aluminium profiles equipped with a stretching gas or electric heater. It has been shown that a stretch heater, which heats the profiles to 270 °C maximum, is sufficient for cleaning the aluminium profiles. The heating is sufficient to soften the plastic parts, but not to cause them to burn.

Last but not least, it is equally advantageous if the line has a liquid nitrogen spraying device for separating the layered structure from the tempered glass. Liquid nitrogen has proven to be an ideal solution in terms of price/performance. In addition, it is a basic air gas, so it does not pose any threat to the environment. There are also no chemical reactions as pure nitrogen is an inert gas, so no dangerous emissions are produced. The invention has the major advantage of gently extracting whole components for the production of new photovoltaic panels or other products. By using components directly from waste, the energy and raw material consumption is reduced. In addition, the extraction process is as gentle as possible compared to the well-known thermal processing or to possible chemical processing. Moreover, the disposal of old photovoltaic panels using the invention produces a small amount of waste, which is easier to dispose of in an environmentally friendly manner, either by landfilling or by breaking down into basic feedstock.

Example of the embodiment of invention

It is understood that the specific embodiments of the invention described and illustrated below are presented for purposes of illustration and not as a limitation of the invention to the examples provided. Those skilled in the art will find or be able to provide, using routine experimentation, a greater or lesser number of equivalents to the specific embodiments of the invention described herein.

The discarded photovoltaic panels consist of a tempered glass plate, under which is arranged a layered structure consisting of photovoltaic cells, electrically conductive motifs, covering and fixing foils. The edge of the layered structure and the tempered glass is enclosed by a frame made of aluminium profiles, which protects the sides of the tempered glass and the layered structure from moisture penetration and mechanical damage. In addition, the aluminium frame protects the tempered glass plate from bending stresses that would cause the tempered glass to break.

As a first step, the PV panel is clamped and a beam is used to cut along the aluminium frame. The cut results in a loose aluminium frame and tempered glass with a layered structure. The source of the beam can be a commercially available industrial laser or a commercially available pressure pump with a nozzle to drive a waterjet carrying abrasive particles.

As part of the cutting process, the aluminium frame is cut into individual aluminium profiles. At the same time the format of the tempered glass is changed. The tempered glass format can be further cut into several smaller panes. Depending on the target use of the extracted components.

The result of cutting a rectangular frame is the gain of two longer and two shorter aluminium profiles, if the frame is square, the gain is four aluminium profiles of the same length. If the residues of tempered glass and layered structure have not fallen off spontaneously when handling the frame or profiles, these residues are scraped off with a brush grinder or scraper. If the adhesion of the residues is too great for mechanical separation, it is possible to pass the profiles through a heater consisting of a stretching furnace, where the profile and the residues are heated rapidly up to 270 °C. Some residues may become deformed enough to facilitate their removal by mechanical means. Others fall off on their own due to the different thermal expansion of the different materials. In the case of more resistant contamination, the profiles can be sandblasted.

This makes the aluminium profiles ready for further use. It is possible to polish or coat the profiles, but this does not fall within the example of an embodiment of the invention.

The tempered glass with a layered structure is cooled uniformly by spraying liquefied nitrogen. The cooling must be carried out evenly to avoid stresses that would lead to tempered glass cracking. The change in temperature will cause the polymer materials to curl in exactly the same way as when exposed to heat, but in this case, there is no risk of harmful substances being formed. Other materials of a layered structure will become so brittle that, unless they fall off spontaneously, it is very easy to scrape them off. Cooling does not have much effect on the tempered glass itself. Tempered glass is more brittle but stable. However, if the tempered glass is damaged but not visible to the eye, e.g. it is cracked, this process will clearly show the damage to the tempered glass and the tempered glass is discarded by itself so that it does not cause damage when it is planned to be used again.

Once the tempered glass returns to ambient temperature, it is re -polished so that its surface is free of, for example, scratches and dirt. The tempered glass is then ready for reuse.

The plastic waste from metal conductive tracks and semiconductor solar cells is sorted out from the remnants of the layered structure. The line itself is built in such a way that the individual stations are procedurally related to each other. It is possible that some of the stations will be intertwined. The aluminium frame separation station is equipped with commercially available laser or waterjet cutting equipment. Handling of the PV panels and components is either by human operators or by automation equipment such as robotic manipulators. The aluminium frame dismantling station is equipped with cutting beams (waterjet, laser). It can also be equipped with brush or disc grinders and chisels.

The aluminium profile processing station may include a stretching furnace with a gas burner or an electric stretching furnace. The rate of passage of the aluminium profile is adapted to the degree of residues adhering to it and their willingness to be released by heat. The station may include a sandblasting device.

The line station for separating the tempered glass from the layered structure consists of a work bench on which the tempered glass is placed. Further, the station is provided with at least one liquid nitrogen spray nozzle which is supplied from a liquid nitrogen tank. The invention would also work with other liquefied gases reaching low temperatures, but these must be gases with a profitable return. Theoretically, for example, liquefied helium could be used, but on the other hand the invention would lose its economic advantage. The skilled person may suggest the use of other liquefied gases according to the current price and production situation, but at the time of filing the application, liquefied nitrogen is the most suitable gas.

Subsequently, the line is equipped with a tempered glass surface treatment station, which includes rotary polishers.

Industrial applicability

The method and line according to the invention will find application in the supply chain of aluminium and tempered glass components, in particular for the production of new photovoltaic panels.