Abstract
An assembly and a method for photovoltaic (PV) panel recycling is disclosed. The assembly comprises (a) a mechanical means to remove aluminium frames; (b) a furnace; (c) a cooling station; (d) a wet bench; (e) a filtration system; (f) a tilt furnace, and (g) a plurality of crushers for used in crushing recovered glass and silicon wafers.
Claims
1. An assembly for recycling of solar panel having an aluminium frame, backsheet and EVA encapsulant, comprising: (a) a mechanical means to remove aluminium frames and junction boxes of a solar panel to be recycled, wherein the solar panel is deframed; (b) a furnace having an incineration temperature of 550 C. which provides incineration process to the deframed solar panel from (a), wherein the backsheet and the EVA encapsulant are being removed, and glass piece is being retrieved as one piece; (c) a cooling station for cooling the solar panel exited from the furnace as the solar panel is of high temperature; (d) a wet bench which is being used to proceed the solar panel with a Ag stripping process; (e) a filtration system for filtering of Ag from the Ag stripping process in (d), (f) a tilt furnace for melting of Ag from Ag sludge, wherein the tilt furnace burns the Ag sludge at 800 C. for 30 minutes to remove any unreacted agents being used in Ag stripping in (d), (g) a plurality of crushers for used in crushing recovered glass and silicon wafers into smaller fragments and pieces for easy transport, packaging and storage for further downstream recyclers.
2. The assembly for recycling of solar panel as set forth in claim 1, further comprising a conveyor belt (100) being used to link from the mechanical means to the furnace, from the furnace to the cooling station, and from the cooling station to the wet bench, and from the wet bench to the filtration system, from the filtration system to the tilt furnace, and from the tilt furnace to the crushers.
3. The assembly for recycling of solar panel as set forth in claim 1, wherein a carrier (90) is deployed to deliver solar panel in recycling process.
4. The assembly for recycling of solar panel as set forth in claim 1, wherein a holder is used in holding the solar panel for thermal processes in the assembly.
5. A method for solar panel recycling, the method comprising the steps of: providing solar panel with a plurality of solar cells, aluminium frame and junction boxes, and having one surface of a glass bonded by an encapsulant and a backsheet being coated between the one surface of the glass and the encapsulant; deframing of the solar panel by a deframing machine to remove any inverters and copper wirings on the solar panel, wherein the deframed panels are then inserted into a holder; incinerating the deframed panels in the holder at a furnace being conducted at 550 C. for a period of 30 minutes, and transferring the incinerated panels in the holder to a cooling station where the panels are cooled to room temperature; stripping the solar cells which are being inserted into the holder and soaked in a container to obtain a stripped solution, wherein the container contains a stripping solution; washing and rinsing the stripped solar cells and filtering the stripped solution to obtain a Ag sludge; and filtering, rinsing and washing the Ag sludge and then proceeding to a tilt furnace to obtain Ag melt.
6. The method as set forth in claim 5, wherein the temperature of the tilt furnace is fired up to 1100 C. to melt the Ag sludge.
7. The method as set forth in claim 5, further comprising the step of pouring the Ag melt onto a preheated mold to form Ag ingot.
8. The method as set forth in claim 5, wherein the striping solution comprises 50% diluted HNO3.
9. The method as set forth in claim 5, wherein the Ag stripping is completed within 30 seconds.
10. The method as set forth in claim 5, wherein hydrochloric acid is first added to the stripped solution to precipitate the silver ions so as to convert AgNO.sub.3 into AgCl.
11. The method as set forth in claim 5, wherein EVA encapsulant is being removed when the incineration temperature is raised to 550 C., and the glass is also obtained as one piece.
12. The method as set forth in claim 5, wherein the backsheet is being removed when the incineration temperature is at 550 C.
13. The method as set forth in claim 5, wherein the optimal temperature and duration for the process to obtain glass of the solar panel is 550 C. and 30 minutes respectively.
14. The method as set forth in claim 5, wherein a conveyor belt system is used to transport the solar panels.
15. The method as set forth in claim 9, wherein the temperature of the Ag stripping at 800 C.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] The above and other aspects, features, and advantages of the present disclosure will be more clearly understood from the following detailed description, taken in conjunction with the accompanying drawings.
[0042] FIG. 1 shows visual observation of the backsheet and EVA encapsulant after the mini-modules were incinerated in the various as-stated temperatures and durations in accordance with the present invention.
[0043] FIG. 2 illustrates further optimization studies for the thermal incineration process in accordance with the present invention.
[0044] FIG. 3 illustrates images showing the cells before and after the stripping process in accordance with the present invention, wherein there are changes on the busbars and fingers after the stripping process.
[0045] FIG. 4 indicates visual changes that occur with each step of conversion from AgNO.sub.3 into Ag metal in accordance with the present invention.
[0046] FIG. 5 indicates recycling line concept for solar panels on the industrial scale level in accordance with the present invention.
[0047] FIG. 6 indicates a perspective view of holder and the front view of the holder in accordance with the present invention, wherein the shaded area of the front view represents deframed solar panels.
[0048] FIGS. 7A-7C respectively illustrate a perspective view, bottom view and top view of the carrier for the solar cells for the chemical process in accordance with the present invention, wherein FIG. 7D is a close-up of the top view when the carrier is loaded with solar cells.
[0049] FIG. 8 is an overview of the PV recycling pilot line layout in accordance with the present invention, which comprises a deframing machine, a furnace, a cooling station, a wet bench station (chemical station), a filtration system, a tilt furnace, and a plurality of crushers.
[0050] FIG. 9 shows close-up images of the individual components of FIG. 8 of the PV recycling pilot line layout plan in accordance with the present invention.
[0051] FIG. 10 shown the wet bench in accordance with the present invention, which comprises an incoming loading section, a bath container for stripping and recovery, a container for DI water rinsing, a partition for drying, and an outgoing/unloading section.
[0052] FIG. 11 shows a proposed floorplan layout/equipment footprint in accordance with the present invention.
[0053] FIG. 12 shows exemplification of the circular PV economy related to solar panel production by year 2030.
[0054] FIG. 13 shows composition percentage of a typical silicon-based solar panel.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0055] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. While the disclosure is subject to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are explained in detail in the description. However, the disclosure should not be construed as being limited to the embodiments set forth herein, but on the contrary, the disclosure is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the embodiments. In the drawings, the sizes or shapes of elements may be exaggerated for convenience and clarity of description.
[0056] In general, the present invention provides an assembly and a method for photo voltaic (PV) cells, panels or system recycling.
[0057] FIG. 8 illustrates an assembly for photovoltaic (PV) panels recycling which comprises a deframing 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 a tilt furnace (60). There are several components in each solar panel that can be removed or extracted by employing the assembly and method of the present invention. These components will be removed in the following order: Al frame together with the junction box, following by removing of the backsheet of the solar panel, and EVA encapsulant, and finally the removal of Ag and Si. FIGS. 8 and 11 show a list of the key process stations to remove these components mentioned above, with a detailed description of the process hereinafter.
[0058] As shown in FIG. 5, which the recycling line concept for solar panels on the industrial scale level in accordance with the present invention is indicated. Schematically, the recycling process in accordance with the preferred embodiment of the present invention is as follows: [0059] 1. At start/end point: this is where the solar panels will be loaded into a carrier (90) which will be transported around the various stations (station 1 to station 8) through a conveyor belt system (100). The processed solar cells will also be transported to this point when the entire process is completed. The implementation of the conveyor system (100) marks the automation of this recycling line, which differentiates itself from that of a laboratory setting. [0060] 2. At station 2: Al frame+junction box removal [mechanical]: this step is necessary to remove the Al frames and junction boxes attached to the outermost framework of the solar panels. This will be carried out by a commercially available tool designed specifically for this purpose. [0061] 3. At station 3: Removal of top glass and backsheet via EVA encapsulant incineration [thermal]after the solar panels are stripped on the outside, this is followed by the rear backsheet layer and the EVA encapsulant layers removal to get access to the embedded solar cells. This step will be carried out by placing the solar panels into a furnace where an incineration temperature of 550 C. would be applied. The holding temperature is optimal at 30 minutes. This ensures that the backsheet would be burnt off, and that the EVA encapsulant that is holding the backsheet and top glass together would melt and degrade off as well. After this process is completed, the products that would be obtained are the top glass and the individual solar cells. [0062] 4. At station 4: Cooling [post-thermal]before proceeding onto the next step, the cells need to undergo a cooling session as they would exit the furnace with a high temperature. The cells need to be cooled to room temperature prior to the next process. [0063] 5. At station 5: Ag stripping process [chemical]in this stage, the cells would be soaked into a polypropylene/polyethylene basin containing 50% nitric acid bath (1 nitric acid:1 DI water) for 30 seconds. A bubbler or agitator should be operational during the stripping process. With this step, Ag would be stripped off the cells while leaving Al untouched on the wafer surface. [0064] 6. At station 6: Precipitation process [chemical]this process focuses on the treatment of the dissolved Ag. A series of conversions take place at this step. Firstly, HCl would be added into the basin. This would convert the AgNO.sub.3 from the previous step into white AgCl, which would precipitate out in an aqueous medium. Secondly, NaOH is added into the mixture to neutralise the excess acid and also to convert AgCl into Ag.sub.2O. This reaction is spontaneous and produces a brown precipitate. Additionally, dextrose is added into the mixture until a black, jelly-like precipitate is formed, which results from a redox reaction occurring between the Ag and dextrose moieties. In this case, Ag.sub.2O is reduced into Ag metal, while dextrose is oxidized into gluconic acid. This mixture would be filtered at the end, producing a dull-grey Ag sludge. All reagents added at this step were added until no more conversions were observed/no more reaction is observed. [0065] 7. At station 7: Purificationat this stage, the Ag sludge would be transferred into a furnace which would burn this mixture at 800 C. for 30 minutes to remove the excess (unreacted) reagents. This leaves behind Ag metal, soot and dross/scum. This mixture would then be transported into another custom-made furnace where it would be melted into molten state, and impurities would be removed from the Ag metal as they float upwards. After the Ag metal has been purified, it would be loaded onto a preheated mold to form Ag ingot. [0066] 8. At station 8: Wash baythis is where the silver-extracted solar cells as well as the precipitated Ag will be washed and dried. Both components will be transported back to the start/end point, station 1, for collection. This step is important so that the collected components will be pure and free from the remnants of the earlier steps. [0067] 9. Optional station 9: Additionally, the recovered glass and silicon wafers would be crushed with a mechanical crusher. This would reduce those materials into smaller fragments and pieces, which would ease the transport, packaging and storage of these materials to further downstream recyclers.
Sample Holders
[0068] FIG. 6 indicates a perspective view of holder and the front view of the holder in accordance with the present invention, wherein the shaded area of the front view represents deframed solar panels. In accordance with the present invention, the holder design is used for the thermal process of solar panel recycling. This will be used when the panels are sent into the furnace for the incineration of the backsheet and EVA encapsulant. The holder will be made of an alloy containing stainless steel and nickel (Ni) of the following dimensions: 2.2 m (l)1.5 m (w)1 m (ht) as depicted in (a) of FIG. 6. This holder has an array of slots in which the deframed solar panels will be horizontally inserted, with the glass facing downwards and backsheet side facing up, as shown in (b) of FIG. 6. During the incineration process, as the backsheet and EVA encapsulant are removed, the glass at the bottom will act as a tray to hold onto the loose, exposed solar cells. The individual solar panels will be separated from each other by 13 cm each. This holder is designed to hold up to 7 panels, an estimated total panel weight of 140 kg, and will be transported in and out of the furnace via a conveyor belt system.
[0069] After the incineration process, the exposed solar cells would be obtained in smaller, loose pieces. For the chemical station, these solar cells will be processed in a polypropylene/polyethylene carrier with dimensions of 2 m (l)0.7 m (w)1 m (ht) as shown in FIG. 7. These carriers are designed such that they are able to hold the loose solar cells in a vertical manner. There is an array of holes at the bottom of this carrier design to facilitate the flow of chemicals into and out of this carrier. The carrier will be removed from the soaking solution once Ag is fully stripped from the solar cells.
Overview of the Recycling Pilot Line Design
[0070] FIG. 8 shows the overall layout of the PV recycling pilot line at the industrial scale. The idea conception for the PV recycling line is materialized here, with this setup consisting of the following equipment: a deframer, a furnace, a cooling station, a wet bench (chemical station), a filtration system, a tilt furnace, and crushers. A close-up view of the individual equipment is provided in FIG. 9. The key processes are as follows: mechanicalto remove the aluminium frame and junction box, and to crush the glass and silicon wafers; thermalto incinerate off the backsheet and EVA encapsulant, and to mold raw Ag into Ag ingot; and chemicalto strip Ag from the solar cells and to recover Ag. The individual processes are described below: [0071] (1) Panel deframingthis is the initial step for the recycling line. The solar panels to be recycled must first have their aluminium frames and junction boxes removed. This includes the removal of any inverters and copper wiring. This tool is commercially available. [0072] (2) Furnacethe deframed panels will be inserted into the holder as described above, and will be transported into the furnace via a conveyor belt line. The incineration process will be conducted at 550 C. for 30 minutes before removing the panels from the furnace. [0073] (3) Coolingthe panels would then be transported into the cooling station via an extension of the conveyor belt line to be cooled down to room temperature. [0074] (4) Wet benchwith the conveyor transport, the panels would be brought over to the chemical station once they are cooled. From here, the loose, exposed solar cells would be inserted into the chemical holder (described above), which would then be soaked into a larger container containing the stripping solution. [0075] a. The stripping solution used here is 50% diluted HNO.sub.3 (1 HNO.sub.3:1 DI H.sub.2O) [0076] b. The conversion of AgNO.sub.3 into AgCl requires 110 mL of HCl per 20 panels' worth of Ag [0077] c. The conversion of AgCl into Ag.sub.2O requires 90 mL of NaOH per 20 panels' worth of Ag [0078] d. The conversion of Ag.sub.2O into Ag requires 35.5 g of dextrose per 20 panels' worth of Ag [0079] e. The stripped solar cells would require washing and rinsing [0080] (5) Post wet-bench [0081] a. Filtrationwhen AgNO.sub.3 is converted into AgCl, this has to be filtered first before proceeding on to the next step on AgCl conversion into Ag.sub.2O [0082] b. Filtrationthe Ag sludge obtained from the final step of the chemical process needs to be filtered and rinsed from the unreacted, excess reagents [0083] c. The stripped solar cells which have been rinsed and washed at the chemical station would be manually brought over to the crusher for further dismantling. Small pieces of the wafers would be collected at the end. [0084] (6) Tilt furnacethe Ag sludge that was filtered, rinsed and washed in step 5a would be brought over to this tilt furnace. The temperature would be fired up to 1100 C. to melt the Ag sludge. The impurities that cannot be melted e.g. the dross and scum would be scooped out and sifted aside. The pure Ag melt would then be poured onto a preheated mold to form the Ag ingot. This ingot must be rinsed and dried before it is ready for resale.
Wet Bench
[0085] FIG. 10 shows a detailed view of the wet bench chemical process. The wet bench chemical process comprises a total of 5 segments, which at the end is responsible for the stripping of Ag from the solar cells as well as the retrieval of the stripped wafers. These 5 segments are partitioned as follows: [0086] (a) Incoming loadingthis is the start of the chemical station, where the loose, exposed solar cells will be transported to before the stripping begins. The transportation will be executed via a conveyor belt system. [0087] (b) Reaction baththis is where the stripping of Ag and its subsequent recovery is performed. It is a single container capable of handling the multi-step reaction. [0088] (c) DI H.sub.2O rinsingthe stripped wafers will be brought over to this section to be rinsed thoroughly with DI water. [0089] (d) Dryerthe stripped wafers have to be dried prior to being unloaded to be sent for mechanical crushing [0090] (e) Unloading baydried-stripped wafers will be sent here for unloading.
Floorplan Layout/Equipment Footprint
[0091] FIG. 11 shows a proposed floorplan layout/equipment footprint in accordance with the present invention. Herein, the proposed floorplan layout/equipment footprint of the recycling pilot line is described. The dimensions of the floorplan is estimated to be 17 m (w)26 m (l). The outer perimeter encompasses the conveyor belt transportation system which primarily runs through the furnace, the cooling station and the wet bench (chemical station). The smaller equipment like the deframing machine, the filtration system, the tilt furnace and the crushers are positioned within this rectangular boundary.
[0092] In accordance with the present invention, additional preferred embodiments could be obtained with modifications.
[0093] The first modified embodiment looks similar to FIG. 8, except that an additional furnace is added after the filtration step. This furnace would be used for the purification of the Ag sludge after the filtration process. In this additional incineration step, soot would most likely be produced from the burning of the excess, unreacted reagents such as dextrose. The addition of this furnace would then allow for an independent incineration-purification step without the clogging up of the tilt furnace.
[0094] The second modification would be to the wet bench (chemical station), where the reaction container would be used for Ag stripping and recovery. Instead of using HCl, NaOH and dextrose for the recovery stage, it could be replaced with zinc dust or copper strips for an alternative single-displacement reaction to precipitate Ag metal from AgNO.sub.3.
Commercial Applications of the Present Invention
[0095] This invention can be applied to both p- and n-type silicon solar cells in existing setups/systems, and can be adapted and modified to suit the needs of future panels. Single, standalone solar cells and wafers can also be recycled with this recycling technology. This includes solar cells that are partially processed, and low grade/scrapped solar cells which are rejected from solar cell/panel manufacturing plants as well as EPC and O&M companies. This allows our recycling initiative to bring in a higher resale revenue.
[0096] This design described in this invention is scalable in several aspects, hence it is able to cater to a wide range of solar cells and panels, which includes both the small and large variants. The recovery of raw materials as described by this invention is of a much higher concentration by weight, which therefore permits a higher resale revenue as well.
[0097] High load throughput is permissible with this invention design, which allows for high recycling processing per workday. This enables more solar cells and panels to be recycled at a time, which allows for the recycler to cater to more customers to speed up the rate of raw materials recovery and subsequently the re-input of these raw materials to generate newer solar cells and panels. By extension, this also means that this invention is capable of enabling the recycling of the high value precious metal Ag from the solar panel wastes, which is key to achieving a sustainable solar recycling business model. This would tackle the current common challenge faced by the commercial solar e-waste industry.
[0098] An industrial-scale setup can be built with the design described in this invention. Automated processing can also be implemented in this design. With an automation in the process line, less manpower is needed, and the recycling productivity can be increased. This helps to generate a higher resale revenue.
[0099] There are potential limitations to both the thermal and chemical steps in the above hybrid and modified models: [0100] 1. [Thermal]the furnace will be operating at high temperatures (550 C.) to ensure complete burn-off of the EVA encapsulant as well as the backsheet. This temperature is high enough such that many by-products will be obtained when plastics are burnt in the process. Furthermore, the burning off of the EVA encapsulant and backsheet would also produce CO.sub.2 on complete burning. Therefore, it is important to attach the furnace to a scrubber which would filter off toxic and harmful gases before release into the environment. A quencher is also required to quench off the hot flue gas produced from this incineration process. [0101] a. The high operating temperature also implies that a suitable fire extinguisher should be made accessible in case of overheating failures. [0102] b. With the use of a suitable scrubber, about 80-90% of CO.sub.2 produced from the incineration process can be removed, so this would not be a major concern. [0103] 2. [Chemical]in a large-scale operation, the volumes of liquid reagents would inevitably amount to a sizeable portion. Therefore, it is imperative to have the appropriate safety measures in place such as spill kits or spillage solutions. For the waste liquids, it should be appropriately treated before disposal. Proper training and risk assessment and prevention measures will help to mitigate and improve the safety measures. Proper labwear should also be worn when dealing with the wet bench processes. [0104] 3. Facility housingsufficient spacing should be given to house these stations and for manpower to move around with ease. An additional spacing should be set aside for a medical bay in case of emergency and the setups should not block any escape routes. Panel storage space should also be allocated for incoming decommissioned panels as well as recycled samples exiting from the recycling line. [0105] 4. Throughput integration between equipmentthe throughput obtained from the various stages could vary greatly from each other. This can be overcome by optimizing the design for each station. For example, the number of tools per process station could be adjusted so that the overall throughput would be balanced across the line.
[0106] While the invention has been described in connection with certain preferred embodiments, it is not intended to limit the scope of the invention to the particular forms set forth, but, on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the true spirit and scope of the invention as defined by the appended claims.
