Photovoltaic module recycling

Solar modules are sustainable and over 90 percent can be recycled. On average after around two years modern solar systems produce already more energy than would be necessary for their production and recycling. Everything that is produced in terms of energy after this time is pure energy gain. The main components such as silicon, aluminum, and copper can be recycled for new solar modules or other products. The recovery of other valuable metals such as gold, silver, tellurium, gallium, indium, and others is a challenge, but possible.

Photo by Anders Jacobsen on Unsplash

PV system structure and composition 

Photovoltaic systems consist of several solar modules and these consist of individual solar cells. The individual modules have a glass panel made of special solar glass on the surface for protection, which allows light to pass through almost unhindered in the spectral range that is interesting for electricity production. Below are solar cells made of silicon that are soldered together, and the metals silver, indium, gallium, tellurium, and selenium are used here too. For encapsulation, the solar cells are encased in a layer of plastic above and below. On the outside, an aluminum frame stabilizes the solar module. Each module also has its cable connection through which the electricity is transported away. Older, as well as newest modules, can also contain other metals due to the different development.

Solar modules wear out due to environmental influences

The modules are delivered unprotected from frost, wind, hail, rain, dust, and heat. Mechanical damage results in the affected module performing worse. If the defective module cannot be replaced or removed, the repair of the solar system can be expensive and time-consuming. Dismantling the system is then often easier and cheaper than repairing it. As a rule, however, you can easily count on an operating life of 20 years. It must also be borne in mind that older systems are nowhere near as efficient as new ones and that they are therefore often replaced earlier. This applies especially to first-generation modules.

Aluminum, glass, and copper are recovered

Mainly cables, frames, and glass are recycled. The metals aluminum and copper can be melted down and reused after a refining process. The glass, which is flat glass, can also be used again as such. It can be processed into window glass or new solar modules.

Together, these components make up around 90 percent of the weight of the modules. With the remaining ten percent, things get interesting. Around three percent of the cell consists of silicon, the rest are small amounts of valuable elements such as gold, silver, tellurium, gallium, indium, and selenium. The contents differ depending on the model. These materials are embedded in thin plastic films with which they are firmly fused. That makes it very difficult to recycle.

You have to cleanly separate them before they can be recycled. But this is extremely time-consuming. Therefore, today the most common end up in the waste incineration plant, and the valuable materials are lost.

Photo by Ricardo Gomez Angel on Unsplash

Pyrolysis solves the problem

The modules are heated under the exclusion of oxygen and high pressure so that the plastics dissolve into gas. This process is called pyrolysis. What is left is glass, aluminum, silicon, and other valuable metals. They can then be recycled using electrochemical processes. That process has been around for a long time in other areas, but it is still new in the recycling of solar modules and it is eagerly researched and developed.

Conclusion

Almost complete recycling of solar modules is possible and offers huge opportunities for a more sustainable future and a circular economy. There is ongoing research to optimize the process and there are great opportunities to build a company on it. One thing is clear, as the adaptation of renewable energies increases, so does the amount of waste, and this requires innovative solutions.

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