New glass-to-glass PV module design enables rapid delamination

An international research team has developed an induction heating-assisted delamination method for end-of-life photovoltaic modules to improve recyclability and facilitate the recovery of individual components.

“We designed a glass-glass photovoltaic module that is easier to take apart at the end of its life,” corresponding author Yonghwan Lee told pv magazine. “Using induction heating, we rapidly separated the layers of our test module and recovered 99.8% of its original mass, including the glass, the silicon cell and the polymer encapsulant.”

Lee said the team was surprised by how quickly and cleanly the silicon cell separated using the new technique and modified module design.

“In our fastest test, the module layers separated in just 5 seconds. We recovered the cell intact, with no visible polymer residue on its surface, without having to remove the entire encapsulant layer first,” he said.

The researchers first used Comsol Multiphysics simulations to investigate induction heating in passivated emitter and rear contact (PERC) cells and heat transfer through the surrounding module layers. They examined the effects of operating frequency, coil current, coil-to-cell distance and electrode thickness on heating.

They then produced simplified samples comprising a 2 cm × 2 cm PERC cell laminated onto tempered glass with ethylene vinyl acetate (EVA) encapsulant, leaving the rear of the cell exposed. They tested the method using a water-cooled copper induction coil operating at 270 kHz to 300 kHz to rapidly heat the cell’s metal contacts, triggering localized EVA decomposition at the cell-encapsulant interface. The samples were suspended with the cells facing downward to enable gravity-assisted separation.

The tests showed that induction heating created a temperature difference of more than 200 C between the cell and glass at a coil current of 100 A, enabling localized EVA decomposition at the cell interface. With gravity-assisted separation, the cells detached in approximately 14 seconds.

Microscopy revealed no significant polymer residue or structural damage on the recovered cell surfaces, while spectroscopy indicated that the remaining EVA largely retained its chemical structure.

The researchers then fabricated modified glass-glass mini-modules incorporating a single PERC cell, EVA encapsulant and two tempered glass sheets measuring 5 cm × 8 cm and 1 mm thick. Polytetrafluoroethylene (PTFE) release films, each with a central opening measuring 1.8 cm × 1.8 cm, were inserted between the cell and EVA on both sides to allow gases generated during heating to escape. The researchers suspended the mini-modules in a custom support jig and applied induction heating at coil currents of 100 A, 150 A and 200 A.

The modified mini-modules separated in 18.6 seconds at a coil current of 100 A, compared with 8.3 seconds at 150 A and 5.4 seconds at 200 A. The process recovered 99.8% of the total module mass, with negligible losses of glass, cells and release films.

After delamination, the researchers mechanically scraped the EVA from the glass, resulting in less than 10% encapsulant mass loss. Analysis of the recovered cells showed no significant surface residue.

“For us, this points to a way to recycle modules quickly and brings the goal of 100% material recovery closer,” Lee said. “Our next step is to apply the process to full-size commercial PV panels and scale it up for use in commercial recycling operations.”

The researchers presented their findings in “Inductive heating for photovoltaic module recycling and near-complete component recovery,” which was published in Communications Materials. The research team included scientists from South Korea’s Korea Electronics Technology Institute (KETI) and Australia’s University of New South Wales (UNSW).