Patent Application
20250230522
This patent application claims the benefit of priority of Singapore Patent Application No. 10202250065Q, filed 6 Jun. 2022. The above application is incorporated by reference herein.
The present disclosure relates generally to assembly and method for PV panel recycling, and in particular, a fully integrated indoor assembly for solar panel recycling and the method of recycling using the same.
Silicon based photovoltaic (PV) systems capacity has increased exponentially over the years, as reported by the International Renewable Energy Agency (IRENA), with a global installed PV capacity exceeding 700 GW as of end 2020, and is predicted to rise further to 1600 GW in 2030 and onwards to 4500 GW in 2050. Correspondingly, the PV-related waste is also expected to increase, and effective PV end-of-life management solutions are required.
This is a significant move towards reducing reliance on conventional energy sources which worsens the climate change issue. However, the amount of PV-related waste generated from these systems is expected to rise as well, where the current PV waste stands at 250k tonnes, and is predicted to increase to 8M tonnes by 2030 and 78M tonnes by 2050. If considering an average module power of 400 W, the total number of decommissioned solar panels amounts to 625k, 20M, and 195M pieces respectively. This is a massive quantity of decommission panels that needs to be handled in time to come.
At the moment, the conventional way of handling this PV waste is to turn to landfill dumping, which raises issues relating to the reduction in usable land space and increasing environmental pollution. It is also a huge waste of resources if these potentially reusable constituent materials within the solar panels end up disposed. Therefore, it is important to recycle these constituent materials as much as possible. In this regard, delivering a circular PV economy is necessary, which ensures the sustainability of the PV ecosystem both at the point of installation and at their end-of-life management. By breaking down the decommissioned solar panels into their respective components and repurposing these recovered materials back into new PV systems, millions of new panels can be reproduced.
EP 2997169 A1 entitled “Process for treating spent photovoltaic panels” discloses treatment of photovoltaic end-of-life panels, such as those made of CdTe and crystalline and amorphous silicon. The process involves automated physical and chemical operations that, combined in a sequence, allow recovering glass in the first place and also tellurium, zinc, cadmium, iron, and concentrate silicon, TiO2 and silver. By means of this process the different types of panel can also be treated all together, without any kind of preliminary selection.
WO2017009062A1 entitled “Method for recycling photovoltaic solar cells module” discloses recycling/recovering a core (9) of a silicon solar cells module (8) in its raw components comprising the steps of: d) providing a core (9) of a silicon solar cells module wherein the cells (6) are interconnected by connection ribbons (5) and embedded in an encapsulation layer (4) said encapsulation layer (4) being sandwiched between a back sheet (7) and a front glass plate (3); e) introducing the core (9) of the silicon solar cells into a reactor; f) dismantling the solar cells core (9) by hydrothermal treatment under subcritical atmosphere to generate recovered clean glass component and a residual laminate (10).
The cumulative PV capacity is predicted to reach 1600 GW by 2030, while the cumulative PV panel waste would also reach to the scale of millions of tonnes as well. Therefore, it becomes necessary to recycle the components from these decommissioned panels, so that there would be enough raw material recovered to produce an equally enormous number of new panels—thus delivering a circular PV economy. Additionally, with the incoming wave of panels to be dealt with, it also becomes necessary to create a high throughput PV recycling system capable of handling this volume.
Often, a general reluctance to adopt PV panel recycling stems from the concern of recycling costs as compared to the conventional approach of landfill dumping. Therefore, the efficiency of this PV recycling process becomes critical, and the purity of the recovered materials has to be as high as possible. This ensures that these recycling activities deliver both environmentally and financially feasible outcomes, which in turn helps to encourage more PV asset owners to adopt the recycling approach instead of landfill dumping for their end-of-life panels.
Currently, most recyclers handle PV waste by crushing into smaller bits. These pieces will then either be resold for a low price or dumped into landfills. Alternatively, commercial tools could also be purchased to deframe the panels prior to their crushing, but the efforts often stop at this point. On the other hand, laboratory-scale recycling methodologies have been demonstrated with single standalone solar cells bought directly from solar cell/panel manufacturers. There have been limited reports of the integration of both processes at the solar panel level. This leaves a gap, where there are current technical solutions for surface-level solar panel dismantling and cell-level stripping of silver and aluminium but not an integrated linkway between these two, which is required for a complete recycling of solar panels.
The present invention discloses an indoor based integrated PV panel recycling solution and the method of recycling using the same. The preferred embodiments described herein with goals to facilitate an effective and efficient recovery of the raw materials (>90%) to realise a circular PV economy outcome. The key benefits of this PV recycling setup and its various embodiments include: (1) clean removal of panel backsheet and EVA encapsulant while leaving the glass piece intact, (2) tackling the panel recycling problem from a high volume, high throughput perspective, (3) selective extraction for Ag without contamination of Al, (4) rapid Ag extraction process for high throughput recycling, (5) simple to operate design and (6) scalable and suitable for industrial use. By adopting the approach in this invention disclosure, solar panels can now be efficiently and effectively recycled in an environmentally friendly approach.
The present invention provides a solar panel recycling turnkey to address the above-mentioned problems. Firstly, decommissioned waste panels will be deframed by a mechanical tool to remove the aluminium frames and junction boxes. Once this is complete, the panels will then be sent for a uniquely developed incineration process to remove the backsheet and the EVA encapsulant. This process will be described in details in the following sections. Once the incineration is complete, the glass piece would be retrieved in one piece, which can be reutilized by downstream consumers. The solar cells would also be detached and will proceed on to the chemical process for silver extraction. The developed silver extraction know-how will also be elaborated in this invention disclosure. After the silver extraction, the remaining stripped silicon pieces would be rinsed and sold to downstream consumers. The extracted silver would be purified and melted into an ingot. To summarize, with the turnkey indoor based solar panel recycling solution elaborated in this invention disclosure, over 90% of the constituent materials within each solar panel can be recovered and reutilized in new applications, thus delivering an economically sustainable environmental impact.
This invention seeks to provide a turnkey solution for solar panel recycling.
Apart from the initial mechanical process, the subsequent thermal process for the removal of the backsheet and EVA encapsulant as well as the stripping and recovery processes for the silver contained within the solar cells were developed in-house. As covered above, the key novelty and benefits of this disclosed process method and the respective device design and its modified embodiments can be summarised as: (1) tackling the full-size solar panel recycling needs with a high throughput process, (2) clean removal of panel backsheet and EVA encapsulant to obtain access to the underlying silicon solar cells while leaving the glass piece intact, (3) selective extraction for Ag without contamination of Al, (4) rapid Ag extraction process for high throughput recycling, (5) easy to operate design and (6) scalable and suitable for industrial scale deployment. Using the approach in this invention disclosure, solar panels can now be recycled effectively in an environmentally friendly manner.
Using the approach in this invention disclosure, the effective extraction of the valuable Ag metal from decommissioned solar panels has been demonstrated on a conceptual front as well as on an industrial-scale adaptation. At the moment, most research efforts center around the smaller-sized silicon solar cells. This leaves a huge gap for the PV recycling industry to fill as there are no other viable solutions for panel scale metal recovery. Existing reported methods also often lead to crushed cells as the end product without the metal recovery aspects, which reduces the value of these end components. In this invention disclosure, panels can be recycled whole and its components extracted with high purity and little to no damage. The individual pieces are also left intact at the end of the process. These are in line with industrial needs and differs from typical academic research in terms of the processing stages, the techniques used, the products retrieved, and most importantly, the load throughput. Additionally, this Ag metal extraction process is also highly scalable and adoptable.
A main object of the present invention is to provide an assembly and a method for solar panel recycling, wherein the assembly and method provides the advantages as follows:
1. Tackles recycling from a large-scale perspective (panels in this invention disclosure versus cells in literature). This allows the invention to cater to a wider range of customers, which now includes solar asset owners and solar EPC or O&M companies, on top of the existing group of cell and module manufacturers. This extends the outreach effort towards landfill prevention.
2. Clean removal of panel backsheet and EVA encapsulant while leaving the glass piece intact. This allows for a higher resale value of the glass pieces which could be reused for the manufacture of new solar panels.
3. Utilizes an extraction method with significantly higher selectivity for Ag, which ultimately leads to a recovered Ag metal with higher purity as compared to existing methods in literature which dissolves both Al and Ag simultaneously. With a higher material purity, it can be sold for higher prices which is a good motivator for solar cell and panel recycling.
4. Rapid Ag extraction process: The Ag stripping process is significantly faster (˜30 seconds) as compared to most other published reports (hours scale) [2-8]. Therefore, it is suitable for high throughput cell and panel recycling.
5. Simple design, easy to handle and operate.
6. Scalable and suitable for industrial use; can be set up and duplicated in other countries and regions.
Yet another main object of the present invention is to provide an assembly and method for solar panel recycling, which provides advantages, if deploy for industrial use, as follows:
1. Conveyor line for transportation of solar panels/cells from station to station.
2. Each individual station is designed to selectively remove target components while leaving the other components intact. With this specific selectivity, components can be singled out and solely targeted which leaves the remaining portions undamaged.
3. Process line is automated, requires minimal manual supervision. This allows for higher throughput for larger batches to be processed in each single run.
4. Process is clean, produces little waste by-products
5. Stations are modular, and are modifiable portion by portion while not disrupting the other stations/the remaining parts of the line.
To demonstrate the effectiveness of this recycling process, test solar cells and solar mini-modules were subjected to screening and optimization studies for both the thermal process as well as the silver stripping and recovery process as elaborated in the following sections.
Subsequent to the initial deframing step for the removal of the aluminium frames and junction boxes, the backsheet and EVA encapsulant need to be removed from the solar panel to get access to the solar cell (wafers) which are embedded in between. This step is necessary in order for the cells to proceed to the stripping and recovery steps next. Mini-modules were loaded into an industrial furnace and incinerated at several varying temperatures and holding durations to identify a suitable set of conditions. The tested temperatures ranged from 200 to 600° C., and from 30 minutes to 1 hour. The observations were obtained and shown in
As seen in
From the positive initial results shown in
Next, the effectiveness of this turnkey recycling solution could be demonstrated by the rapid Ag stripping process. Solar cells without encapsulant were soaked into a plastic container filled with 500 mL of 50% diluted nitric acid solution (1 HNO3:1 H2O) and a working bubbler. Complete Ag stripping could be achieved within ˜30 seconds and was reproducible across 10 different solar cells. The comparison between the stripped and unstripped cells are featured in
With the 10 tested wafers, the average time taken for complete Ag stripping is ˜30 seconds. The concentration percentages of Ag and Al remaining on the stripped wafers were also tested preliminarily with an x-ray fluorescence (XRF) gun. After the stripping process, no Ag could be detected for the 10 cells, while the amount of Al remained constant at 99%.
The reproducibility of this experiment was demonstrated for 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 then filtered and ICP-OES was performed on the filtrate. For ICP-OES, calibration was performed with 2, 5 and 10 ppm Ag and Al standards. The results for the ICP-OES measurements are presented above in Table 2. The amount of Ag remaining on the stripped wafers are minimal at 0.08, 0.021 and 0.023 mg.
With the combination of these results above, the Ag stripping process in this invention disclosure is rapid at ˜30 seconds, is highly selective for Ag as compared to Al (˜50 to 1), and is highly efficient with an average stripping efficiency of 99.95%.
After the Ag has been stripped, it would remain in the nitric acid (HNO3) solution as silver nitrate (AgNO3; Ag+). This has to be precipitated into a solid and then reduced into Ag metal before it can be resold to upstream consumers. For the conversion pathway into silver metal, the small-scaled solar cells were used for this process formulation. These steps are further described in this invention:
AgNO3+HCl→AgCl+HNO3 a.
The optical images of these processes are presented below. The total time required for these processes is estimated to be ˜2 hours. The purity of Ag metal obtained in these processes is ˜95%.
To summarise the above results, the turnkey indoor based PV recycling solution described in this invention consists of: an initial deframing step to remove the aluminium frames and junction boxes from the solar panels, a subsequent incineration step at 550° C. for 30 minutes for thermal removal of the panel backsheet and EVA encapsulant, a rapid, selective Ag stripping process with 50% diluted HNO3 solution, and the Ag recovery multistep process which requires the addition of HCl, NaOH and dextrose. The obtained Ag metal is purified by a thermal process before molding into ingot form. Rinsing of these ingots finalizes the Ag recovery process.
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.
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.
In general, the present invention provides an assembly and a method for photo voltaic (PV) cells, panels or system recycling.
As shown in
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
In accordance with the present invention, additional preferred embodiments could be obtained with modifications.
The first modified embodiment looks similar to
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 AgNO3.
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.
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.
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.
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.
There are potential limitations to both the thermal and chemical steps in the above hybrid and modified models:
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10202250065Q | Jun 2022 | SG | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/SG2023/050365 | 5/25/2023 | WO |
