Chinese researchers developed a new swelling process to remove glass and EVA backing sheets from solar modules at the end of their life. The technique utilizes a dicarboxylic acid ester, known as a dibasic ester. It is said to prevent excessive cracking of solar cells.
“Our swelling process is non-violent and controllable,” said Wang Dong, lead author of the study. “It does not break solar cells and ensures an efficient recycling rate of cells and precious metals. In addition, it has very low toxicity and the swelling agent can be recycled.”
In an article published in “Recycling of solar cells of solar modules by an environmentally friendly and controllable swelling process using a dibasic ester” Clean technologies and environmental policythe researchers explained that the process uses a dibasic ester (DEB), which is an ester of a dicarboxylic acid commonly used as a lubricant, spinning finish and additive.
“DBE is a promising green solvent that is widely used in the coating industry, which is a mixed ester consisting of dimethyl succinatedimethyl glutarate, and dimethyl adipate,” they said. “Furthermore, DBE it has a boiling range of 196 to 225 C and can dissolve most resins.”
The DBE is claimed penetrate the glass-EVA gap effectively, when esiremoval of moisture from the air to the separation system to hydrolyze DBE. In the next step, an ultrasound field is used promote separation glass-EVA.
“Then the separation system can be filtered get glass and (solar cell + EVA) composite. Finally, the mixture is filtered to obtain (solar cell + EVA) and EVA can be removed by pyrolysis to recover sufficiently solar cells,” the researchers continued. “Unlike the direct thermal process, no fluorine is released during EVA pyrolysis because the backing plate has been removed beforehand.”
The team tested the new technology with a Jinko 535 W solar module measurement 1 956 e.g × 992 mm and weight 22.5 kg, with the junction box and the aluminum frame are removed in advance. It performed the glass-EVA separation in a glass reactor with a base diameter of 120 mm × 12.5 mm and a height of 195 mm × 20 mm.
Using these measurements, researchers discovered that The low swelling of DBE resulted in fewer cracks compared to the commonly used swelling process based on O-dichlorobenzene. They also noted that the price of O-dichlorobenzenezene is between CNY 16,000 ($2,316) and CNY 18,000/ton, while DBE is lower CNY 9,500-10,600/ton.
Finally, using DBE Separating glass-EVA can maintain the relative integrity of EVA to facilitate resource recovery to improve manageability and with DBE as a separation reagent its advantages are low cost and green environmental protection,” Dong emphasized. “However, the detailed cost calculation will be completed this year after the scale test.”