TWI459569B - Method for recycling photovoltaic cell modules - Google Patents

Description

Solar battery module recycling method

The invention relates to a recycling method of a solar cell module, in particular to a recycling method of a solar cell module using segment heating.

As the amount of solar energy equipment continues to increase, a large number of discarded solar cell modules will inevitably be generated in the future. Therefore, the decomposition and recycling method of solar cell modules will be a very important technology in the future.

Taking a traditional twin crystal solar module structure as an example, the structural composition comprises a polycrystalline or single crystal solar cell, a welding electrode serially connected to each cell (the main component is copper tin), a packaged fixed solar cell sheet and an electrode encapsulating film. a back sheet, and a front glass sheet, wherein the encapsulating film and the back sheet are usually made of a plastic material, such as ethylene vinyl acetate (EVA) and polyvinyl fluoride (PVF), respectively. The weight % is about 65.8 wt% of glass, 10.4 wt% of plastic material, 2.9 wt% of solar cell, 1 wt% of electrode, 17.5% of aluminum frame, and 2.4 wt% of junction box. In order to recover the materials of the solar cell module, the solar module must be decomposed. The aluminum frame and the junction box can be easily removed and recycled. The remaining materials must be used because they are firmly covered by the plastic material such as EVA. Special treatment can be further broken down.

EVA and PVF are thermosetting plastic materials that do not melt under heating, but directly burn and decompose when they reach a certain temperature range. Therefore, one of the difficulties encountered in decomposing a twin solar cell module is how to effectively remove plastic materials such as EVA and PVF. The previous literature (Solar Energy Materials & Solar Cells 67 (2001) 397-403) mentions the use of solar cell modules immersed in acid or organic solvents to decompose EVA, but acid or organic solvents take some time to penetrate into solar energy. For battery modules, for large-area modules, the solution must take up to tens of hours to penetrate the center of the module. Therefore, the above acid or organic solvent immersion method can only be limited to small-area modules. In addition, the use of organic solvents is also more likely to cause pollution to the environment.

Another method of removing EVA from PVF is heating. US 6,063,995 discloses heating a twinned solar cell module at a temperature of 480 ° C to 520 ° C to separate the glass plate from the solar cell, and introducing an inert gas during the heating process to avoid carbonization of the plastic in the solar cell module. combustion. However, EVA will deform during the high temperature process, causing the solar cell and the glass plate to rupture, so it is almost impossible to obtain a complete solar cell and glass plate smoothly. In addition, the introduction of a large amount of inert gas (for example, nitrogen) in the heating process causes a large amount of ash to appear at the exhaust end, and the gas containing ash causes difficulty in separation. It can be seen from the above data that the glass plate accounts for a very large proportion (65.8 wt%) in the composition of the twin solar cell module, so the recovery of the glass plate is also one of the key projects for the recovery of the twin crystal solar module. If the integrity of the glass plate can be maintained during the module decomposition process, the recycled glass plate can be directly reused on the module package, which is very helpful for reducing production costs and reducing garbage pollution.

Therefore, there is a need to propose a recycling method for a solar cell module that can solve the above problems.

The invention provides a method for recycling a solar cell module, comprising: (a) providing a solar cell module comprising: a solar cell sheet; a pair of encapsulating films sandwiching the solar cell sheet; a back sheet and a glass sheet Sandwiching the pair of package films; (b) heating the solar cell module at a temperature of 330-380 ° C to separate the pair of package films and the back plate; (c) heating the solar energy at a temperature of 400-450 ° C a battery module for carbonizing the separated pair of package films and the back sheet; and (d) recovering the glass sheet.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The embodiments of the present invention are described in detail below with reference to the drawings, and the same reference numerals are used in the drawings or the description of the same or similar parts, and in the drawings, the shapes of the embodiments or The thickness can be enlarged and simplified or conveniently marked. Further, portions of the various elements in the drawings will be described separately, and it is noted that elements not shown or described in the drawings are shapes known to those of ordinary skill in the art. Further, when a layer is described as being on or over another layer (or substrate), it can mean that the layer is in direct contact with another layer (or substrate) or otherwise. In addition, the specific embodiments are merely illustrative of specific ways of using the invention, and are not intended to limit the invention.

FIG. 1 is a schematic view showing a recycling process of a solar cell module according to an embodiment of the present invention. However, it should be understood that the schematic flow diagram shown in FIG. 1 is merely exemplary and not exhaustive, and other steps may be performed among or among the steps. Figure 1 begins with the step 10 of providing a solar cell module, and then proceeds to step 20, in which the solar cell module is heated at a temperature of 330-380 ° C to separate the encapsulation film and the back plate, and then step 30 is performed. The solar cell module is heated at a temperature of 400-450 ° C to carbonize the separated encapsulation film and back sheet. Upon completion of the heating, the separated glass sheet (step 40), the electrode (step 50), and the solar wafer (step 60) may be recovered directly or indirectly. For example, if the separated glass plate is intact, it can be reused directly. On the other hand, the separated electrode can be purified to recover the metal contained in the electrode. Further, the solar cell sheet may be cleaned with an acid and/or alkali etching solution to obtain a solar wafer.

In an embodiment of the invention, a solar cell module 100 as shown in Fig. 2 is first provided. It should be understood that the solar cell module in FIG. 2 is merely illustrative, and the recycling method of the present invention is not limited thereto. The solar cell module can be a variety of different solar cell modules, such as P-type or N-type solar cells, conventional solar cell structures, metal wrap through (MWT), heterojunction cell structures (heterojunction) With intrinsic thin layer, HIT), selective emitter cell structure (selective emitter) and the like. In a preferred embodiment, the solar cell module 100 is a single crystal germanium or polycrystalline germanium solar cell module.

Referring to FIG. 2 , the solar cell module 100 of the present embodiment may include a solar cell sheet 1 , an electrode 2 connected in series with the solar cell sheet 2 , a pair of encapsulating films 3 sandwiching the solar cell sheet 1 and the electrode 2 , and being disposed on the solar energy The glass plate 5 on the front side of the battery sheet and the back plate 4 disposed on the reverse side of the solar cell sheet 1 are disposed, and the pair of packaging films 3 are interposed between the glass plate 5 and the back plate 4. The electrode 2 may be a copper-tin alloy, but is not limited thereto and may be other suitable metals or alloys. The encapsulation film 3 completely covers the periphery of the solar cell sheet 1 and the electrode 2. The material of the encapsulation film 3 of the present embodiment is usually ethylene vinyl acetate (EVA), and the material of the back sheet 4 is usually polyvinyl fluoride (PVF), such as DuPont ^TM Tedlar. . In some embodiments, the backsheet 4 can be a composite layer comprising two PVF layers 4a with a polyester layer sandwiched between the two layers.

Next, the solar cell module 100 is subjected to sectional heating, wherein the segmented heating includes two-stage or more-stage heating, and can be directly heated in the air without passing other gases. In the present invention, the encapsulating film 3 and the backing plate 4 are separated by segment heating, and then burned and carbonized. If only one-stage heating is used, since the package film 3 in the solar cell module 100 is sandwiched by the back plate 4 and the glass plate 5, the package film 3 will be hindered by the back plate 4 when burned, and thus the module is The structure of 100 causes stress, causing problems such as breakage of the glass plate 5. The inventor of the present invention found that by using segmented heating, the encapsulating film 3 and the backing plate 4 are separated first, and then the combustion carbonization of the encapsulating film 3 and the backing plate 4 is performed, which can reduce the stress on the module 100 during heating to separate. The other components of the complete module 100.

In one embodiment, two-stage heating can be performed, and wherein the temperature of the first stage is lower than the temperature of the second stage. In some embodiments in which two-stage heating is performed, the solar cell module 100 is heated at a temperature of 330-380 ° C to separate the encapsulation film 3 and the back sheet 4. The separation of the encapsulating film 3 and the backing plate 4 is achieved by decomposition combustion, pick-up, and even structural cracking of the backing plate 4 to expose the encapsulating film 3. This period of heating can be at least 10 minutes, preferably about 10-30 minutes. Next, the heating temperature is raised to 400-450 ° C and the solar cell module 100 is heated at this temperature to simultaneously burn the carbonized encapsulating film 3 and the back sheet 4. This period of heating can be at least 2 hours, preferably 2-3 hours. In another embodiment, the second stage heating can be further divided into two sections, wherein the heating is performed at 400-420 ° C for about 1-1.5 hours to carbonize the back sheet 4, and then heated at 420-450 ° C for about 1-3.5 hours. The encapsulating film 3 is carbonized, so that the three-stage heating is performed by carbonizing the back sheet 4 and the encapsulating film 3 of different materials at different temperatures of the second and third stages of heating to burn the back sheet 4 and the encapsulating film 3. Carbonization is more complete. Although the above description is based on two-stage or three-stage heating, the skilled person can adjust the temperature according to the heating characteristics of the material of the package film 3 and the back plate 4 and select a suitable number of heating sections so that the module 100 is heated. The structure is subjected to minimal stress, and other various components of the completed solar cell module 100 can be obtained later.

After the solar cell module 100 is heated and the carbonized encapsulation film 3 and the back sheet 4 are completely burned, the solar cell module 100 is washed with water to remove ash generated during the heating process. At this time, the decomposition and removal of the package film 3 and the back sheet 4 are completed, and the solar cell sheet 1, the electrode 2, and the glass sheet 5 are separated. If the ash content remains on the solar cell sheet 1, the electrode 2, and the glass plate 5, it can be washed with water. It is particularly noted that in the embodiment of the invention, a complete glass sheet 5 is obtained, and the clean and intact glass sheet 5 after cleaning is directly reused in the new solar cell module. The recovered electrode 2 may require additional processing prior to reuse, such as re-separation and purification to obtain a clean metal material. In addition, in the embodiment of the present invention, since the heating temperature is low (lower than the heating temperature of about 480-520 ° C used in the prior art US 6,063,995), it is less likely to have impurities thermally diffuse into the solar cell sheet 1 and The glass sheet 5, therefore, the solar cell sheet 1 and the glass sheet 5 are less contaminated.

The solar cell sheet 1 comprises a wafer, such as a germanium wafer, on which metal electrodes, anti-reflective layers, metal wires and emitter layers are typically formed. The material of the metal electrode may be, for example, aluminum. The material of the antireflection layer may be, for example, SiN _x . The material of the wire can be, for example, silver. In order to obtain a recyclable wafer, the metal electrode, the anti-reflection layer, and the metal wire on the wafer are first removed, but the order of removal is not limited. The wafer can be cleaned by acid etching to remove a metal electrode such as a mixed aqueous solution of hydrochloric acid/hydrogen peroxide (HCl/H ₂ O ₂ ) at 80 °C. The wafer can also be cleaned by acid etching to remove the anti-reflective layer and metal wires, such as a hydrofluoric acid (HF) solution. The wafer can be cleaned with an lye etch to remove the emitter layer, such as a 80 ° C sodium hydroxide (NaOH) solution. Finally, after the wafer is washed with water, it can be used as a raw material in twin growth.

The recycling program of the present invention can solve the problem of solar cell module waste generation and can be applied to many different types of battery modules. The method of the invention firstly and efficiently burns the carbonized EVA and the PVF through the segmented heating. After removing the EVA and the PVF, the solar cell sheet, the welding rod, and the unbroken and complete glass plate can be obtained, wherein the glass plate can be taken directly again. To package the battery module. The separated solar cell sheet can be cleaned by appropriate etching to obtain a clean tantalum wafer, which can be used as a long crystal material. In addition, the separated electrode can be purified to obtain a clean metal material.

Embodiments of the present invention also have the following advantages: (1) the selected heating temperature is low, thereby reducing the possibility of electrode cracking, electrode and bismuth reaction, and diffusion of impurities into the ruthenium wafer and the glass plate, so the purity of the ruthenium wafer is The original wafer is equivalent and can be used as a long-crystal raw material; (2) The segmented heat treatment temperature can prevent the glass plate from being broken due to excessive thermal stress, so the obtained glass plate is exactly the same as the glass plate before packaging, and does not need It can be used directly after recasting, suitable for large-area and large-scale module recycling procedures; (3) It can be heated in the air without introducing inert gas, and the recovery cost is low and the exhaust ash is too high. The problem that is difficult to handle is that the ash generated in the process is removed by washing with clean water, and the cleaned sewage can be purified by sedimentation, so that it is highly feasible to implement in a large number of processes.

[Comparative Example 1: Single-stage heating]

A silicon solar cell module having a size of 200 mm x 200 mm is provided, which has the structure as shown in Fig. 2, including: solar cell sheet, electrode, encapsulation film, back sheet, glass plate, aluminum frame and junction box, And the encapsulation film uses EVA material and the back plate uses DuPont ^TM Tedlar material. Remove the aluminum frame and junction box. The silicon solar cell module after removing the aluminum frame and the junction box is placed in the heating furnace. The temperature in the furnace was raised to about 480 ° C, and the twin solar cell module was heated at this temperature for 1 hour.

The twin crystal solar cell module is taken out from the heating furnace, and the twin crystal solar cell module is cleaned with water to remove the ash generated during the heating process, and the electrode, the solar cell sheet, and the glass plate can be separated at this time. The remaining ash on each part separated is washed with water.

In order to obtain a clean tantalum wafer, the solar cell wafer was subjected to the following treatment. The solar cell was first washed with a mixed solution of 80 ° C hydrochloric acid (HCl concentration 37%) / hydrogen peroxide (H ₂ O ₂ concentration 31%) / water in a volume ratio of 1:1:5 to remove the aluminum metal electrode. Next, the solar cell sheet was washed with a 5% aqueous solution of hydrofluoric acid (HF) to remove the SiN _x antireflection layer and the silver wire. Finally, the solar cell was washed with a 25% aqueous solution of sodium hydroxide (NaOH) at 80 ° C to remove the emitter layer.

Observation of each part of the twin solar cell module separated after the treatment revealed that the separated glass plate was broken and contaminated, the quality of the electrode was deteriorated, and the wafer was contaminated.

[Example 1: Three-stage heating]

A silicon solar cell module measuring 200 mm x 200 mm is provided, which has a structure as shown in Fig. 2, including a solar cell sheet, an electrode, a packaging film, a back sheet, a glass plate, an aluminum frame and a junction box. And the encapsulation film uses EVA material and the back plate uses DuPont ^TM Tedlar material. Remove the aluminum frame and junction box. The silicon solar cell module after removing the aluminum frame and the junction box is placed in the heating furnace. The temperature in the heating furnace was raised to about 380 ° C, and the twinned solar cell module was heated at this temperature for 30 minutes to separate the encapsulating film 3 and the back sheet 4. Next, the temperature in the heating furnace was raised to about 400 ° C, and the twinned solar cell module was heated at this temperature for 1 hour to carbonize the back sheet 4. The temperature in the heating furnace was further raised to about 420 ° C, and the twinned solar cell module was heated at this temperature for 2 hours to carbonize the encapsulating film 3. Fig. 3 is a view showing the temperature change of the three-stage heating of the present embodiment.

After the heating is completed, the encapsulating film 3 and the back sheet 4 are completely decomposed by carbonization. The twin crystal solar cell module is taken out from the heating furnace, and the twin crystal solar cell module is cleaned with water to remove the ash generated during the heating process, and the electrode, the solar cell sheet, and the glass plate can be separated at this time, wherein The glass plate is unbroken and intact. The remaining ash on each part separated is washed with water.

In order to obtain a clean tantalum wafer, the solar cell wafer was subjected to the following treatment. The solar cell was first washed with a mixed solution of 80 ° C hydrochloric acid (HCl concentration 37%) / hydrogen peroxide (H ₂ O ₂ concentration 31%) / water in a volume ratio of 1:1:5 to remove the aluminum metal electrode. Next, the solar cell sheet was washed with a 5% aqueous solution of hydrofluoric acid (HF) to remove the SiN _x antireflection layer and the silver wire. Finally, the solar cell was washed with a 25% aqueous solution of sodium hydroxide (NaOH) at 80 ° C to remove the emitter layer. After the above treatment, a clean tantalum wafer can be obtained.

The purity of the obtained tantalum wafer was measured using a glow-discharge mass spectroscopy (GDMS), and Table 1 shows the concentration of each impurity in the tantalum wafer.

Figure 4 shows the relationship between the concentration of metal impurities contained in the germanium wafer versus the normalized efficiency, which indicates that the concentration of titanium, iron, and aluminum can be tolerated by the germanium wafer, wherein the titanium concentration is lower than 10 ^-5 ppmw and the iron concentration is lower than 2 ×10 ^-3 ppmw, aluminum concentration is less than 2 × 10 ^-2 ppmw. The wafer processed in the first embodiment of the present invention contains 0.02 ppmw of titanium, 0.09 ppmw of iron, and 0.07 ppmw of aluminum, and according to the segregation theory, the segregation coefficients of titanium, iron, and aluminum are respectively k _Ti = 3.2 × 10 ^{-6 .} , k _Fe = 6.4 × 10 ^-6 , k _Al = 2.8 × 10 ^-3 , after the wafer recovery of the first embodiment of the present invention is melted and re-grown into crystals, the concentrations of titanium, iron and aluminum will be reduced to 6.4×, respectively. 10 ^-8 ppmw, 5.8 × 10 ^-7 ppmw, 5.6 × 10 ^-5 ppmw, and as can be seen from Fig. 4, the impurities contained in the recycled material after re-growing the crystal have little effect on the efficiency of the final fabricated battery.

Observing the parts of the twin solar cell module separated after the treatment, not only the glass plate and the electrode were unbroken and intact, but also the contamination of the wafer and the glass plate was smaller than that of Comparative Example 1. Therefore, the portions of the twinned solar cell module separated by the above treatment have better integrity and suffer less pollution.

[Example 2: Two-stage heating]

A silicon solar cell module measuring 200 mm x 200 mm is provided, which has the structure as shown in Fig. 2, including: solar cell sheet, electrode, encapsulation film, back sheet, glass plate, aluminum frame and junction box And the encapsulation film uses EVA material and the back plate uses DuPont ^TM Tedlar material. Remove the aluminum frame and junction box. The silicon solar cell module after removing the aluminum frame and the junction box is placed in the heating furnace. The temperature in the heating furnace was raised to about 330 ° C, and the twinned solar cell module was heated at this temperature for 10 minutes to separate the encapsulating film 3 and the back sheet 4. Then, the temperature in the heating furnace was raised to about 400 ° C, and the twinned solar cell module was heated at this temperature for 2 hours to carbonize the encapsulating film 3 and the backing plate 4. Fig. 5 is a view showing the temperature change of the two-stage heating of the present embodiment.

After the heating is completed, the encapsulating film 3 and the back sheet 4 are completely decomposed by carbonization. The twin crystal solar cell module is taken out from the heating furnace, and the twin crystal solar cell module is cleaned with water to remove the ash generated during the heating process, and the electrode, the solar cell sheet, and the glass plate can be separated at this time, wherein The glass plate is unbroken and intact. The remaining ash on each part separated is washed with water.

In order to obtain a clean tantalum wafer, the solar cell wafer was subjected to the following treatment. The solar cell was first washed with a mixed solution of 80 ° C hydrochloric acid (HCl concentration 37%) / hydrogen peroxide (H ₂ O ₂ concentration 31%) / water in a volume ratio of 1:1:5 to remove the aluminum metal electrode. Next, the solar cell sheet was washed with a 5% aqueous solution of hydrofluoric acid (HF) to remove the SiN _x antireflection layer and the silver wire. Finally, the solar cell was washed with a 25% aqueous solution of sodium hydroxide (NaOH) at 80 ° C to remove the emitter layer. After the above treatment, a clean tantalum wafer can be obtained.

The purity of the obtained tantalum wafer was measured using a glow-discharge mass spectroscopy (GDMS), and Table 2 shows the concentration of each impurity in the tantalum wafer.

Similarly, the influence of the concentration of titanium, iron, and aluminum contained in the germanium wafer after the treatment in the second embodiment of the present invention on the efficiency of the germanium wafer can be found with reference to FIG. The wafer processed in the second embodiment of the present invention contains only 0.18 ppmw of metal aluminum impurities, and according to the segregation theory, the segregation coefficient of aluminum is k _Al = 2.8 × 10 ^-3 , so the wafer recovery of the second embodiment of the present invention is melted. After re-growth into crystals, the aluminum concentration will decrease to 5.1 × 10 ^-5 ppmw. It can be seen from the comparison that the concentration of aluminum contained in the treated germanium wafer has little effect on its efficiency.

Observing the parts of the twinned solar cell module separated after the treatment, not only the glass plate and the electrode were unbroken and intact, but also the contamination of the silicon wafer and the glass plate was smaller than that of Comparative Example 1. Therefore, the portions of the twinned solar cell module separated by the above treatment have better integrity and suffer less pollution.

Therefore, it has been experimentally confirmed that the method for recovering the solar cell module using the segmented heating of the present invention can separate the parts of the relatively complete and less polluting solar cell module, in particular, can be separated from the pollution-free Glass plates and wafers, and in which the glass plate is a complete glass plate, can be directly reused.

While the invention has been described above in terms of several preferred embodiments, it is not intended to limit the scope of the present invention, and any one of ordinary skill in the art can make any changes without departing from the spirit and scope of the invention. And the scope of the present invention is defined by the scope of the appended claims.

100. . . Solar battery module

1. . . Solar cell

2. . . welding rod

3. . . Encapsulation film

4, 4a, 4b. . . Backplane

5. . . glass plate

10, 20, 30, 40, 50, 60. . . step

FIG. 1 is a schematic view showing a recycling process of a solar cell module according to an embodiment of the present invention.

FIG. 2 shows a schematic cross-sectional view of a solar cell module 100.

Fig. 3 is a view showing the temperature change of the three-stage heating of Example 1.

Fig. 4 is a graph showing the relationship between the concentration of metal impurities contained in the germanium wafer after the treatment in the embodiment of the present invention with respect to the normalization efficiency.

Fig. 5 is a view showing the temperature change of the two-stage heating of Example 2.

10, 20, 30, 40, 50, 60. . . step

Claims (14)

A method for recycling a solar cell module, comprising: (a) providing a solar cell module comprising: a solar cell sheet; a pair of encapsulating films sandwiching the solar cell sheet; and a backing plate and a glass sheet sandwiching the (b) heating the solar cell module at a temperature of 330-380 ° C to separate the pair of encapsulating film and the backing plate; (c) heating the solar cell module at a temperature of 400-450 ° C To carbonize the separated package film and the back sheet; and (d) recover the glass sheet. The method for recovering a solar cell module according to claim 1, wherein the steps (b) and (c) are heating under air. The method for recovering a solar cell module according to claim 1, wherein the heating time of the step (b) is from 10 minutes to 2.5 hours. The method for recovering a solar cell module according to claim 1, wherein the heating time of the step (c) is 2 to 5 hours. The method for recovering a solar cell module according to claim 1, wherein the step (c) is heating at a temperature between 400-450 ° C for 2-5 hours to simultaneously carbonize the pair of encapsulating film and the back board. The method for recovering a solar cell module according to claim 1, wherein the step (c) comprises: (c-1) heating the backing plate by heating at 400-420 ° C for 1-1.5 hours; (c- 2) Heating at 420-450 ° C for 1-3.5 hours to carbonize the pair of encapsulating films. The method for recovering a solar cell module according to claim 1, wherein the encapsulating film is ethylene vinyl acetate. The method for recovering a solar cell module according to claim 1, wherein the back sheet is polyvinyl fluoride. The method for recovering a solar cell module according to claim 1, wherein the solar cell module further comprises at least one electrode connected to the solar cell sheet, and after the step (c), further comprising recycling the electrode . The method for recovering a solar cell module according to claim 1, further comprising, after the step (c), pickling and alkali washing the solar cell sheet, and recovering the germanium wafer on the solar cell sheet. The method for recovering a solar cell module according to claim 10, wherein the pickling comprises using a mixed aqueous solution of hydrochloric acid/hydrogen peroxide to remove the metal electrode on the tantalum wafer. The method for recovering a solar cell module according to claim 10, wherein the pickling comprises using a hydrofluoric acid solution to remove the antireflection layer on the tantalum wafer. The method of recovering a solar cell module according to claim 10, wherein the caustic washing comprises using a sodium hydroxide solution to remove an emitter layer on the tantalum wafer. The method for recovering a solar cell module according to claim 1, wherein the step (d) further comprises washing the glass plate with water.