The first generation of solar panels is reaching the end of their lifespan due to their age. A new laser technology can make recycling the panels much more efficient. This allows scarce raw materials to be reused, which is good for the environment and helps reduce dependence on imports. The laser technology was developed by TNO.
Solar modules are made to withstand weather and wind for at least 25 years. They have to withstand heat, cold, moisture and mechanical stress. That is why components such as glass and solar cells are firmly glued together. This is done with so-called encapsulants.
Difficult to recycle
The sturdiness of solar panels is an advantage during use, but a disadvantage during recycling. The adhesive layers make it almost impossible to detach components without damaging them. Once discarded, dismantling the panels and separating the materials used is therefore not easy.
Current recycling methods are often crude: panels are ground up or heated to high temperatures. With these techniques, materials such as silver and pure silicon are not recovered at all, or cost a very large amount of energy. This poses a major challenge in recycling. A new laser-based approach from TNO offers a solution. The technology dismantles solar panels much more efficiently, while preserving valuable raw materials.
Separating layers with targeted heat
TNO developed an alternative approach to dismantling solar panels. The panels are designed to capture as much light as possible. This principle is the key to recycling. A strong laser locally converts the light in the active layer of the solar panel into heat. The targeted temperature rise removes the adhesion between the solar cells and the encapsulants. Thus, the different layers are separated from each other in a controlled way, without heating or chemically treating the whole panel. The technology is applicable to different types of solar panels.
The approach leads to a much cleaner separation of materials, according to TNO. For example, the glass remains intact and the solar cells are released with hardly any glue residue. The process requires less than 1 kWh of energy per module. That is a fraction of the energy consumption of conventional techniques such as pyrolysis, which costs 25 kWh per module.
Silver and silicon
TNO cites circularity as a driver for development, but also points to the scarcity of raw materials and their value. And the value of raw materials is not small. Many valuable materials are present in solar panels. One example is silver. By 2024, about 24% of silver mined worldwide will be used in solar panels. New laser technology is expected to recover as much as 99% of the silver.
Besides silver, solar panels also contain high-purity silicon. This can be efficiently reused within Europe, for example in batteries or new solar cells. Furthermore, the glass and plastics in the solar panels are also easier to reuse if they are recovered cleanly.
The new laser technology could therefore become a profitable process, according to TNO. The revenues in the form of pure materials are much higher than the costs of recycling. This makes high-quality recycling economically interesting and promising as more solar panels reach the end of their useful life and volumes in the waste stream increase.
From optimisation to upscaling
TNO's research has been running for three years and is now beyond the exploratory phase. Almost all common solar panels have already been successfully treated and taken apart in the lab. In the process, the researchers continuously optimise the process, for example by looking at how different laser types affect the adhesive layers.
One striking aspect is that the process makes itself partly 'visible'. As the laser does its job and adhesion decreases, the surface subtly changes colour. This gives researchers instant feedback and helps to fine-tune the process.
The research has now been scaled up from laboratory set-ups to applications for industrial recycling. The next phase focuses on incorporating laser technology into the full process chain of PV recycling. This will involve testing under field conditions.
Cooperation with various parties
TNO is working not only on the technology itself, but also on how it fits within existing and future recycling chains. The researchers are working with industry, policymakers, government, machine builders, solar panel manufacturers and recyclers.
Several projects with industrial partners are currently underway and more collaborations are in the pipeline. These include testing on complete modules with a Dutch machine builder.
"This laser technology provides a goldmine of raw materials. Indeed, by 2030, a significant amount of discarded solar panels is expected in Europe. A unique economic opportunity!", says Mirjam Theelen, research leader at TNO. "With this laser-based technology, we are taking a big step towards a circular solar industry."
