Assembly and method for recycling of a photovoltaic (PV) system

Abstract

An assembly and method for the recycling of photovoltaic (PV) panels are disclosed. The assembly comprises: (a) mechanical means for removing an aluminum frame; (b) a furnace; (c) a cooling station; (d) a wet bench; (e) a filtration system; (f) an inclined furnace; and (g) a plurality of crushers for use in crushing the recovered glass and silicon wafers.

Description

Technical Field

[0001] Cross - reference to Related Applications This patent application claims the priority of Singapore Patent Application Publication No. 10202250065Q, filed on June 6, 2022. The above application is incorporated herein by reference.

[0002] The present disclosure generally relates to assemblies and methods for the recycling of PV panels, and more particularly, to a fully integrated indoor assembly for recycling solar panels and a recycling method using the same.

Background Art

[0003] As reported by the International Renewable Energy Agency (IRENA), the volume of silicon - based photovoltaic (PV) systems has been increasing rapidly over the years. As of the end of 2020, the global PV installed volume exceeded 700 GW, and it is predicted to further increase to 1600 GW by 2030 and further to 4500 GW by 2050. Accordingly, it is expected that PV - related waste will also increase, and effective PV life - cycle management solutions are needed.

[0004] This is an important move towards reducing dependence on conventional energy sources that exacerbate climate change issues. However, the amount of PV - related waste generated from these systems is also expected to increase. The current PV waste is 250,000 tons, but it is predicted to increase to 8 million tons by 2030 and 78 million tons by 2050. Assuming the average power of the module is 400 W, the total number of decommissioned solar panels will be 625,000, 20 million, and 195 million respectively. This is a huge amount of decommissioned panels that will need to be handled in the future.

[0005] At present, the conventional methods of dealing with this PV waste rely on landfill disposal, which gives rise to problems related to the reduction of available land space and the increase of environmental pollution. When the reusable constituent materials in the solar panels are finally processed, they become a huge amount of waste resources. Therefore, it is important to recycle these constituent materials as much as possible. In this regard, it is necessary to realize a circular PV economy that ensures the sustainability of the PV ecosystem both at the time of installation and in the management after the end of life. By disassembling the decommissioned solar panels into their respective components and reusing the recovered materials in a new PV system, millions of new panels can be regenerated. Figure 12 shows an illustration of a circular PV economy related to the production of solar panels until 2030.

[0006] European Patent Application Publication No. 2997169 (A1) titled "Process for treating spent photovoltaic panels" discloses the treatment of end-of-life photovoltaic panels made of, among others, CdTe and crystalline silicon, amorphous silicon, etc. This process includes automated physical and chemical operations combined in sequence, first recovering the glass, and further recovering tellurium, zinc, cadmium, iron and concentrated silicon, TiO2, and silver. This process allows all different types of panels to be treated together without any prior selection of any kind.

[0007] International Publication No. WO 2017 / 009062 (A1) entitled "Method for recycling photovoltaic solar cells module" discloses recycling / recovering the core (9) of a silicon solar cell module (8) in its raw material state, the method comprising: d) providing the core (9) of a silicon solar cell module, wherein the cells (6) are interconnected by connection ribbons (5) and embedded in a sealing layer (4), and the sealing layer (4) is sandwiched between a backsheet (7) and a front glass plate (3); e) introducing the core (9) of the silicon solar cell into a reactor; f) disassembling the solar cell core (9) by hydrothermal treatment in a subcritical atmosphere to produce recovered clean glass components and a residual laminate (10).

[0008] It is predicted that by 2030, the cumulative volume of PV will reach 1600 GW, and the cumulative waste of PV panels will also reach the scale of millions of tons. Therefore, it is necessary to recycle the components of these decommissioned panels, thereby recovering raw materials sufficient to produce a similarly huge number of new panels, thus bringing about a circular PV economy. Furthermore, with the incoming wave of panels to be processed, it is also necessary to create a high-throughput PV recycling system capable of handling this volume.

[0009] In many cases, the general negativity towards adopting PV panel recycling is due to concerns about recycling costs compared to the conventional landfill approach. Therefore, the efficiency of this PV recycling process becomes important, and the purity of the recovered materials needs to be as high as possible. This will ensure that these recycling activities bring environmentally and economically viable results, thus helping to encourage more PV asset owners to adopt a recycling approach instead of landfilling end-of-life panels.

[0010] Figure 13 shows the component percentages of a typical silicon-based solar panel. This panel consists of glass (74%), encapsulant (7%), silicon (3%), backsheet (4%), silver / Ag (0.05%), and other very precious elements such as aluminum / Al, zinc, lead, copper, and tin (11.95%). The values in parentheses represent weight percentages. Each of these components, when extracted from the solar panel, is transferred to the next stage of recycling, where it is handed over to both upstream and downstream partners. Upstream recyclers take precious metals such as Ag and Al, and downstream recyclers take other components for proper disposal. In any case, a significant proportion (>90%) of these components can be reused and diverted to new solar panels, which helps to establish a circular PV economy.

[0011] Currently, most recyclers handle PV waste by crushing it into smaller pieces. These pieces are either resold at a low price or disposed of in landfills. Alternatively, it is possible to purchase a commercially available tool to remove the panel frame before crushing them, but often, the activity stops at this point. On the other hand, a laboratory-scale recycling method using a single stand-alone solar cell purchased directly from a solar cell / panel manufacturer has been demonstrated. Limited reports exist on integrating both processes at the solar panel level. This reveals that while current technical solutions exist for the disassembly of solar panels at the surface level and the peeling of silver and aluminum at the cell level, there remains a defect of the absence of an integrated linkway between these two, which is required for the complete recycling of solar panels.

[0012] The present invention discloses an indoor-based integrated PV panel recycling solution and a recycling method using the same. The preferred embodiments described herein aim to promote the effective and efficient recovery (>90%) of raw materials to achieve the results of a circular PV economy. The main advantages of this PV recycling facility and its various embodiments are as follows: (1) The panel backsheet and EVA encapsulant can be cleanly removed, and the glass pieces remain intact. (2) From the perspective of large volume and high throughput, the panel recycling problem can be addressed. (3) Silver can be selectively extracted without Al contamination. (4) The silver extraction process is rapid for high-throughput recycling. (5) The design has a simple operation. (6) It is expandable and suitable for industrial applications. By adopting the approach in the disclosure of the present invention, solar panels can now be recycled efficiently and effectively in an environmentally friendly approach.

[0013] The present invention provides a solar panel recycling turnkey solution to address the above problems. First, the discarded waste panel has its frame removed by a mechanical tool for removing the aluminum frame and junction box. Once this removal is complete, the panel is sent to a uniquely developed incineration process to remove the backsheet and EVA encapsulant. This process will be described in detail in the next section. Once the incineration is complete, the glass pieces are recovered as one piece and can be reused by downstream consumers. The solar cells are also separated and proceed to a chemical treatment process for silver extraction. The developed technical information on silver extraction will also be described in detail in the disclosure of the present invention. After silver extraction, the remaining peeled silicon pieces are rinsed and sold to downstream consumers. The extracted silver is purified and melted into ingots. In summary, by using the turnkey indoor-based solar panel recycling solution detailed in the disclosure of the present invention, more than 90% of the constituent materials within each solar panel can be recovered and reused for new applications, resulting in an economically sustainable environmental impact.

Summary of the Invention

Problems to be Solved by the Invention

[0014] An object of the present invention is to provide a turnkey solution for the recycling of solar panels.

[0015] Separate from the initial mechanical process, subsequent heat treatment processes for removing the backsheet and EVA encapsulant, and silver stripping and recovery processes included in the solar cells have also been developed in-house. As described above, the main novelty and advantages of the disclosed process methods and their respective device designs and modified embodiments can be summarized as follows: (1) Addressing the recycling needs of standard solar panels through a high-throughput process, (2) Cleanly removing the panel backsheet and EVA encapsulant to contact the underlying silicon solar cells, with the glass pieces remaining intact, (3) Selectively extracting Ag without Al contamination, (4) The Ag extraction process is rapid for high-throughput recycling, (5) The design is easy to operate, (6) It is expandable and suitable for industrial-scale deployment. By using the approach disclosed in the present invention, currently, solar panels can be effectively recycled in an environmentally friendly manner.

[0016] By using the approach disclosed in the present invention, it has been demonstrated both conceptually and at an industrial scale that valuable Ag metal can be effectively extracted from discarded solar panels. At present, most research efforts are centered around small silicon solar cells. Since there are no other viable solutions for panel-scale metal recovery, a large gap remains to be filled in the PV recycling industry. In the methods already reported, often crushed cells also result as the final product, but there is no way to recover the metal, reducing the value of these final components. In the disclosure of the present invention, the panels are recycled as a whole, and their components are extracted with high purity and almost no damage. At the end of the process, the individual pieces also remain intact. These are in line with the needs of the industry and are different from typical academic research in terms of the process steps, the technologies used, the products recovered, and most importantly, the throughput of the load. Furthermore, this Ag metal extraction process is highly scalable and adoptable.

[0017] The main object of the present invention is to provide an assembly and method for the recycling of solar panels, which assembly and method provide the following advantages. 1. From a large-scale perspective, addressing recycling (panels in the disclosure of the present invention versus cells in the literature). This makes the present invention available to a wider range of customers, including solar asset owners, solar EPC or O&M companies, in addition to existing groups of cell and module manufacturers. This expands the outreach activities towards landfill prevention. 2. The panel backsheet and EVA encapsulant can be cleanly removed, and the glass pieces remain intact. This increases the resale value of the glass pieces and enables them to be reused in the manufacture of new solar panels. 3. An extraction method with significantly high selectivity for Ag is adopted, and compared with the existing method of simultaneously dissolving both Al and Ag described in the literature, finally, Ag metal with high purity will be recovered. When the purity of the material is high, it can be sold at a higher price, which is a good incentive for the recycling of solar cells and solar panels. 4. Rapid Ag extraction process: The Ag stripping process is significantly faster (about 30 seconds) compared to most other published reports (time scale) [2-8], making it suitable for high-throughput cell and panel recycling. 5. Simple design, easy to handle and operate. 6. Expandable and suitable for industrial applications, and can be installed and replicated in other countries and regions.

[0018] Yet another main object of the present invention is to provide an assembly and method for recycling solar panels that, when deployed for industrial use, provide the following advantages. 1. A conveyor line for transporting solar panels / cells between stations. 2. Each station is designed to selectively remove the target component while leaving other components intact. This specific selectivity allows the components to be picked out and individually targeted, while the remaining parts remain undamaged. 3. The process line is automated, minimizing the manual monitoring required. This enables larger batch processing per run, improving throughput. 4. The process is clean and produces few waste by-products. 5. The stations are modular and can be changed part by part without interfering with the rest of the other stations / lines.

Means for Solving the Problems

[0019] To demonstrate the effectiveness of this recycling process, screening and optimization studies were conducted on both the heat treatment process and the silver stripping and recovery process for test solar cells and solar cell mini-modules, as described in detail in the following section.

[0020] (A) Thermal incineration of the panel backsheet and EVA encapsulant: After the step of removing the first frame to remove the aluminum frame and the junction box, it is necessary to remove the backsheet and the EVA encapsulant from the solar panel so that the solar cells (wafers) embedded therein can be contacted. This step is necessary for the cells to proceed to the next peeling and recovery steps. The mini-module was mounted in an industrial furnace, incinerated at various temperatures and holding times, and a suitable set of conditions was identified. The test temperature was 200 - 600 °C, and the time was 30 minutes - 1 hour. Observation results were obtained and are shown in Figure 1. This shows the visual observation of the backsheet and the EVA encapsulant after the mini-module was incinerated at various set temperatures and periods.

[0021] As confirmed in Figure 1, it was observed that the backsheet (and thus the EVA encapsulant) remained intact at 200 °C and 300 °C. However, when the temperature rose to 400 °C, visible decomposition was clearly observed. When the temperature was further raised to 500 °C, a clean burn-off of the backsheet and the EVA encapsulant was obtained. Despite a small amount of soot being observed on the exposed solar cells and glass after the incineration process, the upper tempered glass remained intact as one piece. This glass piece can be washed and cleaned and prepared for the next reuse.

[0022] From the positive initial results shown in Figure 2, further optimization studies of the thermal incineration process are shown. As previously shown in Figure 1, since 500 °C is already suitable when removing the backsheet and the EVA encapsulant, in this extended study, tests at higher temperatures of 550 °C and 600 °C were conducted to determine whether it is possible to increase the process temperature to improve throughput. At 550 °C, it was observed that the backsheet and the EVA encapsulant burned off cleaner without producing soot, but at 600 °C, the glass became brittle and began to break into pieces. Therefore, the optimal temperature and time suitable for this process are considered to be 550 °C and 30 minutes, respectively.

[0023] (B) Silver metal (Ag) peeling process: Next, the effectiveness of this turnkey recycling solution can be demonstrated by a rapid Ag stripping process. Solar cells without encapsulants were immersed in a plastic container containing 500 mL of 50% diluted nitric acid solution (1HNO3:1H2O) and an operating bubbler. Complete Ag stripping could be achieved within about 30 seconds and was reproducible with 10 different solar cells. A comparison of the stripped cells and non-stripped cells is shown in Figure 3, which shows images of the cells before and after the stripping process. Note the changes in the busbars and fingers after the stripping process.

[0024]

Table 1

[0025] For 10 test wafers, the average time required for complete Ag stripping was about 30 seconds. The concentration percentages of Ag and Al remaining on the stripped wafers were also preliminarily tested with an X-ray fluorescence (XRF) gun. After the stripping process, Ag could not be detected in 10 cells, but the amount of Al remained constant at 99%.

[0026]

Table 2

[0027] The reproducibility of this experiment was also demonstrated with 3 additional wafers. These wafers were subjected to the same stripping process, after which the stripped pieces were crushed into smaller pieces and digested with pure HNO3 for 5 minutes. These mixtures were filtered and ICP-OES was performed on the filtrate. For ICP-OES, calibrations were performed using Ag and Al standards of 2, 5, and 10 ppm. The results of the ICP-OES measurements are shown in Table 2 above. The amounts of Ag remaining on the stripped wafers were 0.08, 0.021, and 0.023 mg at minimum.

[0028] Combining the above results, the Ag stripping process in the disclosure of the present invention is rapid, taking about 30 seconds, highly selective for Ag compared to Al (about 50 to 1), with an average stripping efficiency of 99.95%, and is very efficient.

[0029] Silver metal (Ag) recovery process: Figure 4 shows the visual changes that occur at each step of the conversion of AgNO3 to Ag metal according to the present invention.

[0030] After Ag is stripped, it remains as silver nitrate (AgNO3; Ag + ) in the nitric acid (HNO3) solution. This can be precipitated to a solid and then reduced to Ag metal and resold to upstream consumers. For the conversion route to Ag metal, a small-scale solar cell was used in the construction of this process. In the present invention, these steps are further described as follows: 1. To precipitate silver ions, first add hydrochloric acid (HCl; 110 mL) to the reaction mixture. This converts AgNO3 to silver chloride (AgCl), which is insoluble in the aqueous medium. Thus, it precipitates as a white solid by the following reaction.

[0031]

Chemical formula

[0032] 2. After AgCl precipitates, it is filtered and washed with deionized water. Here, the filtration component is important. This is because the filtration component isolates the AgCl product from the acidic medium. By performing this filtration step, the amount of material required for subsequent inspection of AgCl can be reduced. This not only reduces the cost of subsequent steps but also the amount of chemical waste generated from those steps. After rinsing, AgCl is added to 90 mL of 50% diluted NaOH (1 NaOH:1 H2O). This converts AgCl to silver hydroxide (AgOH), which is a necessary step because the Ag complex needs to be in a form that can be safely reduced to obtain silver metal. The reduction of AgCl may generate chlorine gas, which is toxic to the human respiratory system when inhaled in large quantities. Therefore, this step is also necessary considering safety.

[0033] a. When AgOH is formed, in the natural decomposition reaction, it immediately decomposes into brown silver oxide (Ag2O) solid.

[0034]

Chemical formula

[0035] 3. The Ag2O obtained at this stage is ready to be reduced to silver metal. Dextrose (35.5 g) was added to this reaction mixture. This step is described as a redox reaction where Ag2O is reduced to Ag metal and dextrose is oxidized to gluconic acid.

[0036]

Chemical formula

[0037] b. Since Ag metal precipitates as sludge, it needs to be filtered and washed with deionized water. This sludge contains a mixture of Ag metal and undissolved, unreacted dextrose, which can be burned out in a subsequent incineration process.

[0038] 4. Before the Ag metal can be purified and formed into ingots, it is first necessary to remove excess unreacted reagents. The filter paper containing the Ag sludge mix is incinerated in an industrial furnace at 800 °C for 30 minutes, resulting in a residual product mixture of Ag metal and soot, presumably due to incomplete or partial combustion of the organic matter.

[0039] 5. This residual product is fed into an inclined furnace where the furnace is ignited and the Ag metal melts. Once melted, the Ag metal is poured into a preheated mold from this furnace, where the Ag metal forms ingots.

[0040] 6. Finally, the cast Ag ingots are left to cool, then rinsed with deionized water and dried. If other metals are included in the impurities, rinsing with sulfuric acid can also be performed.

[0041] Optical images of these processes are shown below. The total time required for these processes is estimated to be about 2 hours. The purity of the Ag metal obtained by these processes is about 95%.

[0042] In summary, the turnkey in-house based PV recycling solution described in the present invention consists of an initial step of removing the frame to remove the aluminum frame and junction box from the solar panel, followed by a 550 °C, 30-minute incineration step for thermal removal of the panel backsheet and EVA encapsulant, a rapid and selective Ag stripping process using a 50% diluted HNO3 solution, and an Ag recovery multi-step process that requires the addition of HCl, NaOH, and dextrose. The obtained Ag metal is purified by a heat treatment process before being formed into ingot form. The Ag recovery process is completed by rinsing these ingots.

[0043] The above and other aspects, features, and advantages of the present disclosure will be more clearly understood by reading the following detailed description in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0044]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 7C

Figure 7D

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0045] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The present disclosure is subject to various changes and alternative forms, but specific embodiments thereof are shown by way of example in the drawings and described in detail in the specification. However, the present disclosure should not be construed as being limited to the embodiments described herein. Rather, the present disclosure is intended to cover all modifications, equivalents, and alternatives included within the spirit and scope of the embodiments. In the drawings, the size or shape of elements may be exaggerated for convenience of explanation and clarity.

[0046] The present invention generally provides assemblies and methods for the recycling of photovoltaic (PV) cells, panels, or systems.

[0047] Figure 8 shows an assembly for recycling a photovoltaic (PV) panel comprising a frame removal machine (10), a furnace (20), a cooling station (30), a wet bench station (40), a filtration system (50), a first crusher (52), a second crusher (54), and an inclined furnace (60). Each solar panel has several components that can be removed or extracted by using the assembly and method of the present invention. These components are removed in the following order: the Al frame and junction box are removed together, then the backsheet and EVA encapsulant of the solar panel are removed, and finally Ag and Si are removed. FIGS. 8 and 11 show together the main process stations for removing the above components, and a detailed description of the process will be given later.

[0048] As shown in FIG. 5, a recycling line concept for industrial-scale solar panels according to the present invention is shown. The recycling process according to a preferred embodiment of the present invention is generally as follows.

[0049] 1. Start / End Point: Here, the solar panel is mounted on a conveyor (90) and transported via a conveyor belt system (100) to various stations (Station 1 to Station 8). The processed solar cells are also transported to this point when the entire process is completed. Implementing the conveyor system (100) indicates that this recycling line is automated and is itself distinguishable from that of a laboratory environment.

[0050] 2. Station 2: Remove the Al frame + junction box [mechanical]: This step is necessary to remove the Al frame and junction box attached to the outermost framework of the solar panel. This is carried out by a commercially available tool specially designed for this purpose.

[0051] 3. Station 3: Removal of the top glass and backsheet by burning the EVA encapsulant [Heat] - After peeling off the solar panel on the outside, the backsheet layer and the EVA encapsulant layer on the back are removed to contact the embedded solar cells. This step is carried out by putting the solar panel into a furnace, where a firing temperature of 550 °C is applied. The holding temperature is optimally 30 minutes. This will ensure that the backsheet burns out and the EVA encapsulant that holds the backsheet and the top glass together will also melt and decompose.

[0052] After this process is completed, the resulting products are the top glass and the individual solar cells.

[0053] 4. Station 4: Cooling [Post-heat treatment] - Before proceeding to the next step, the cells need to undergo a cooling session as they will be discharged from the furnace in a high-temperature state. It is necessary to cool the cells to room temperature before the next process.

[0054] 5. Station 5: Ag stripping process [Chemistry] - At this stage, the cells are immersed in a polypropylene / polyethylene container containing a 50% nitric acid bath (1 nitric acid: 1 DI water) for 30 seconds. During the stripping process, it is necessary to operate a bubbler or a stirrer. This step leaves the Al on the wafer surface untouched, and the Ag is stripped from the cells.

[0055] 6. Station 6: Precipitation Process [Chemistry] - This process focuses on the treatment of dissolved Ag. In this step, a series of conversions occur. First, HCl is added to the container. This causes the AgNO3 from the previous step to be converted to white AgCl and precipitate in the aqueous medium. Next, NaOH is added to the mixture to neutralize the excess acid and convert AgCl to Ag2O. This is a natural reaction and a brown precipitate forms. Further, dextrose is added to the mixture until a black jelly-like precipitate forms as a result of the redox reaction occurring between Ag and the dextrose moiety. In this case, Ag2O is reduced to Ag metal and dextrose is oxidized to gluconic acid. This mixture is finally filtered to yield a dull gray Ag sludge. All reagents added in this step are added until no further conversion is observed or until no further reaction is observed.

[0056] 7. Station 7: Purification - At this stage, the Ag sludge is transferred to a furnace and this mixture is burned at 800 °C for 30 minutes to remove excess (unreacted) reagents. This leaves behind Ag metal, soot, dross / skum. This mixture is transported to another custom furnace where it is melted in a molten state and the impurities are removed from the Ag metal while floating to the surface. After being purified, the Ag metal is poured into a preheated mold to form Ag ingots.

[0057] 8. Station 8: Washing Bay - Here, the solar cells from which silver was extracted and the precipitated Ag are washed and dried. Both components are transported back to Station 1, the start / end point for collection. This step is important to ensure that the components collected are pure and free of residues from the previous step.

[0058] 9. Optional Station 9: Further, the recovered glass and silicon wafers are crushed using a mechanical crusher. This breaks these materials down into smaller fragments and pieces, thereby facilitating their transport, packaging, and storage for downstream recyclers.

[0059] Sample holding part Figure 6 shows a perspective view and a front view of the holding part according to the present invention. The shaded part in the front view represents a solar panel with the frame removed. According to the present invention, the holding part design is used in the heat treatment process for recycling solar panels. This is used when sending the panel into the furnace to incinerate the backsheet and EVA encapsulant. The holding part is made of an alloy containing stainless steel and nickel (Ni) with the following dimensions as shown in Figure 6(a): 2.2 m (length) x 1.5 m (width) x 1 m (height). This holding part has an array of slots for horizontally inserting a solar panel with the frame removed, with the glass facing downwards and the backsheet side facing upwards, as shown in Figure 6(b). During the incineration treatment process, when the backsheet and EVA encapsulant are removed, the glass at the bottom functions as a tray and holds the exposed solar cells. The individual solar panels are approximately 13 cm apart from each other. This holding part is designed to hold up to 7 panels (estimated total panel weight 140 kg) and is transported into and out of the furnace via a conveyor belt system.

[0060] After the incineration treatment process, the exposed solar cells will be obtained as smaller separate pieces. At the chemical treatment station, these solar cells are processed in a polypropylene / polyethylene transport part with dimensions of 2 m (length) x 0.7 m (width) x 1 m (height) as shown in Figure 7. These transport parts are designed to hold the separate solar cells vertically. At the bottom of this transport part design, there is an array of holes to facilitate the flow of chemicals into and out of the transport part. When Ag is completely peeled off from the solar cells, the transport part is taken out of the immersion solution.

[0061] Overview of the recycling pilot line design Figure 8 shows the overall layout of the PV recycling pilot line at the industrial scale. Here, the idea concept of the PV recycling line is materialized, and this facility consists of a frame removal machine, a furnace, a cooling station, a wet bench (chemical treatment station), a filtration system, an inclined furnace, and a crusher. An enlarged view of each individual piece of equipment is shown in Figure 9. The main processes are as follows: Mechanical processing - removing the aluminum frame and junction box, and crushing the glass and silicon wafers; Heat treatment - incinerating the backsheet and EVA encapsulant, and forming raw Ag into Ag ingots. Chemical processing - stripping Ag from the solar cells and recovering Ag. Each individual process is described below.

[0062] (1) Removal of the panel frame - This is the first step of the recycling line. The solar panels to be recycled need to first remove the aluminum frame and junction box. This includes removing the inverter and copper wiring. This tool is commercially available.

[0063] (2) Furnace - The panel with the frame removed is inserted into the holding part as described above and transported to the furnace via the belt conveyor line. Before removing the panel from the furnace, an incineration process is carried out at 550 °C for 30 minutes.

[0064] (3) Cooling - The panel is transported to the cooling station via an extension of the belt conveyor line and cooled to room temperature.

[0065] (4) Wet bench - By conveyor transport, once the panel is cooled, it is carried to the chemical treatment station. From here, the exposed individual solar cells are inserted into the chemical holding part (described above) and immersed in a large container filled with the stripping solution.

[0066] a. The stripping solution used here is 50% diluted HNO3 (1 HNO3:1 DI H2O).

[0067] b. To convert AgNO3 to AgCl, 110 mL of HCl per Ag for 20 panels is required.

[0068] c. To convert AgCl to Ag2O, 90 mL of NaOH per Ag for 20 panels is required.

[0069] d. To convert Ag2O to Ag, 35.5 g of dextrose per Ag for 20 panels is required.

[0070] e. The detached solar cells need to be washed and rinsed.

[0071] (5) Post-wet bench a. Filtration - When AgNO3 is converted to AgCl, it is necessary to filter first before proceeding to the next step of converting AgCl to Ag2O.

[0072] b. Filtration - The Ag sludge obtained at the final step of the chemical treatment process needs to be filtered to rinse off unreacted excess reagents.

[0073] c. The rinsed and washed detached solar cells are manually carried to a crusher for further disassembly. Finally, small pieces of wafers are collected.

[0074] (6) Inclined furnace - The Ag sludge filtered, rinsed, and washed in step 5a is carried to this inclined furnace. To melt the Ag sludge, the temperature is heated to about 1100 °C. For example, non-melting impurities such as dross and scum are skimmed off and sieved. Next, the pure Ag melt is poured into a preheated mold to form Ag ingots. These ingots need to be rinsed and dried before being prepared for resale.

[0075] Wet bench Figure 10 shows a detailed view of the wet bench chemical treatment process. The wet bench chemical treatment process consists of a total of five segments, and finally undertakes the peeling of Ag from the solar cell and the recovery of the peeled wafers. These five segments are partitioned as follows.

[0076] (a) Loading section - This is the start of the chemical treatment station, where exposed individual solar cells are transported here before the start of peeling. The transportation is carried out via a conveyor belt system.

[0077] (b) Reaction tank - Here, the peeling of Ag and subsequent recovery are carried out. This is a single container that can handle multi-step reactions.

[0078] (c) DI H2O rinsing - The peeled wafers are transported to this section and thoroughly rinsed with DI water.

[0079] (d) Dryer - The peeled wafers need to be dried before being taken out so that they can be sent out for mechanical crushing.

[0080] (e) Unloading bay - The dried and peeled wafers are sent here to be taken out.

[0081] Floor plan layout / Equipment installation area Figure 11 shows the floor plan layout / equipment installation area proposed according to the present invention. Here, the proposed floor plan layout / equipment installation area of the recycling pilot line is described. The dimensions of the floor plan are estimated to be 17 m (width) x 26 m (length). On the outer periphery, there is mainly a conveyor belt transport system passing through a furnace, a cooling station, and a wet bench (chemical treatment station). Small devices such as a frame removal machine, a filtration system, an inclined furnace, and a crusher are positioned within this rectangular boundary.

[0082] According to the present invention, additional preferred embodiments may be obtained by way of modifications.

[0083] Note that the first modified embodiment is similar to FIG. 8, except that an additional furnace is added after the filtration step. This furnace is used for the purification of Ag sludge after the filtration process. In this additional incineration step, excessive unreacted reagents such as dextrose are burned, which increases the likelihood of soot formation. By adding this furnace, an independent incineration-purification step becomes possible without clogging the inclined furnace.

[0084] The second modification is for the wet bench (chemical treatment station), and the reaction vessel is to be used for the stripping and recovery of Ag. In the recovery stage, instead of using HCl, NaOH, and dextrose, it can be replaced with zinc powder or copper strips for an alternative single-displacement reaction to precipitate Ag metal from AgNO3.

[0085] Commercial Applications of the Present Invention The present invention can be applied to both p-type and n-type silicon solar cells within existing facilities / systems, and can be adapted and modified to meet the needs of future panels. With this recycling technology, even a single stand-alone solar cell and wafer can be recycled. This includes partially processed solar cells, solar cell / panel manufacturing plants, and low-grade / scrapped solar cells rejected by EPC and O&M companies. Thus, a higher resale profit can be obtained with the recycling concept of the present inventors.

[0086] Since the design described in the present invention can be extended in several aspects, it can be provided for a wide range of solar cells and panels, including both small and large variations. The recovery of the raw materials described in the present invention has a much higher concentration per unit weight, enabling a higher resale profit as well.

[0087] The design of the present invention enables high load throughput, and thus enables high recycling process throughput per business day. This allows more solar cells and panels to be recycled at once, enabling recyclers to serve more customers, increasing the recovery rate of raw materials, and then reinvesting these raw materials to produce new solar cells and panels. Furthermore, this also means that the present invention can enable the recycling of high-value precious metal Ag from solar panel waste, which is key to achieving a sustainable solar recycling business model. This addresses the common challenges currently faced by the commercial solar-e-waste industry.

[0088] With the design described in the present invention, an industrial-scale facility can be constructed. In this design, an automatic process can also be implemented. In the process line, automation can reduce the required manpower and improve the productivity of recycling, which helps generate higher resale profits.

[0089] Both the above hybrid model and modified model have potential limitations in both the heat treatment step and the chemical treatment step.

[0090] 1. [Heat] - To completely burn out the EVA encapsulant and backsheet, the furnace is operated at a high temperature (550 °C). This temperature is high enough that when plastic burns during the process, many by-products are generated. Furthermore, when the EVA encapsulant and backsheet are completely burned out, CO2 is also produced during complete combustion. Therefore, it is important to attach a scrubber to the furnace to filter out toxic and harmful gases before they are released into the environment. A quencher is also required to extinguish the high-temperature flue gas generated from this incineration process.

[0091] a. A high operating temperature also means that in the case of a failure due to overheating, it is necessary to be able to use a suitable fire extinguisher.

[0092] b. By using a suitable scrubber, about 80 - 90% of the CO2 generated from the incineration process can be removed, so it may not be a major problem.

[0093] 2. [Chemistry] - In large-scale operations, the amount of liquid reagents will necessarily be a fairly large portion. Therefore, it is essential to have appropriate safety measures such as a spill kit or spill solution. Waste liquids need to be properly treated before disposal. Appropriate training as well as risk assessment and preventive measures are useful for reducing and improving safety measures. When handling wet bench processes, it is necessary to wear appropriate laboratory clothing.

[0094] 3. Facility accommodation - These stations need to be accommodated and sufficient space should be obtained so that personnel can move around easily. In case of an emergency, additional space for a medical bay should be secured and no evacuation routes should be blocked. The panel storage space should be allocated not only for recycled samples discharged from the recycling line but also for the acceptance of discarded panels.

[0095] 4. Integration of throughput between equipment - The throughput obtained from various stages may vary greatly from each other. This can be overcome by optimizing the design of each station. For example, the number of tools for each process station can be adjusted so that the overall throughput across the line is balanced.

[0096] Although the present invention has been described in connection with specific preferred embodiments, it is not intended to limit the scope of the invention to the specific forms described. Rather, it is intended to cover alternatives, modifications, and equivalents that may fall within the true spirit and scope of the invention as defined by the appended claims.

Claims

1. An assembly for recycling a solar panel having an aluminum frame, a backsheet, and an EVA encapsulant, comprising: (a) mechanical means for removing the aluminum frame and junction box of the solar panel to be recycled, wherein the solar panel is removed from the frame; (b) a furnace having an incineration temperature of 550° C., which provides an incineration treatment to the solar panel from which the frame has been removed in (a), wherein the backsheet and the EVA encapsulant are removed and the glass pieces are recovered as one piece; (c) a cooling station for cooling the solar panel discharged from the furnace because the solar panel is at a high temperature; (d) a wet bench used to carry out the Ag peeling process of the solar panel; (e) a filtration system for filtering Ag from the Ag peeling process in (d); (f) an inclined furnace for melting silver from the Ag sludge, the inclined furnace burning the Ag sludge at 800° C. for 30 minutes to remove any unreacted agents used in the Ag peeling in (d); (g) a plurality of crushers used to crush the recovered glass and silicon wafers into smaller pieces and fragments to facilitate transportation, packaging, and storage for downstream recyclers.

2. An assembly for recycling the solar panel according to claim 1, further comprising a conveyor belt (100) used to cooperate from the mechanical means to the furnace, from the furnace to the cooling station, from the cooling station to the wet bench, from the wet bench to the filtration system, from the filtration system to the inclined furnace, and from the inclined furnace to the crushers.

3. An assembly for recycling the solar panel according to claim 1, wherein a conveying unit (90) for sending the solar panel in the recycling process is arranged.

4. An assembly for recycling the solar panel according to claim 1, wherein a holding part is used when holding the solar panel for the heat treatment process in the assembly.

5. A method for recycling a solar panel, comprising: Providing a solar panel comprising a plurality of solar cells, an aluminum frame, and a junction box, wherein one surface of the glass is joined by a sealing material, and a backsheet is coated between the one surface of the glass and the sealing material; Removing the frame of the solar panel by a frame removal machine and removing any inverters and copper wires on the solar panel, wherein the panel with the removed frame is inserted into a holding part; Incinerating the panel with the removed frame in the holding part in a furnace at 550 °C for 30 minutes, transferring the incinerated panel in the holding part to a cooling station, and cooling the panel to room temperature; Peeling the solar cells inserted into the holding part and immersed in a container to obtain a stripping solution, wherein the container contains the stripping solution; Washing the peeled solar cells, rinsing, filtering the peeled solution to obtain Ag sludge; Filtering the Ag sludge, rinsing, washing, and advancing it to an inclined furnace to obtain an Ag melt, the method comprising these steps.

6. The method according to claim 5, wherein the temperature of the inclined furnace is heated to 1100 °C to melt the Ag sludge.

7. The method according to claim 5, further comprising the step of pouring the Ag melt into a preheated mold to form an Ag ingot.

8. The method according to claim 5, wherein the stripping solution contains 50% diluted HNO3.

9. The method according to claim 5, wherein the Ag stripping is completed within 30 seconds.

10. First, hydrochloric acid is added to the stripping solution to precipitate silver ions so as to convert AgNO ３ to AgCl. The method according to claim 5.

11. The method according to claim 5, wherein when the incineration temperature is raised to 550 °C, the EVA sealing material is removed and the glass is also obtained as one piece.

12. The method according to claim 5, wherein the backsheet is removed when the incineration temperature is 550 °C.

13. The method according to claim 5, wherein the optimum temperature and period for the process for obtaining the glass of the solar panel are 550 °C and 30 minutes, respectively.

14. The method according to claim 5, wherein a conveyor belt system is used to transport the solar panel.

15. The method according to claim 9, wherein the temperature of the Ag stripping is 800 °C.

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