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Expanding solar energy production is the key to reducing emissions worldwide. Globally, solar panels produced 720 terawatt hours of energy in 2019, which is about 3% of global electricity production. And it took about 46 million metric tons of solar panels to do that.

By 2030, around 8 million metric tons of decommissioned solar panels could accumulate worldwide. By 2050, this number could reach 80 million. Recycling these panels could provide a new source of materials that would otherwise have to be mined (potentially in unsafe or exploitative operating conditions), making solar power a more sustainable piece of the clean energy puzzle.

What’s in a solar panel?

The solar panels are laid out as a sandwich with cells in the center. About 90% of commercial solar panels use silicon as a semiconductor, which converts light into electricity. Thin strips of metal, usually silver, cross the surface of the silicon crystals in each cell and carry electricity into the copper wiring of the panel.

The solar cells are enclosed in a protective barrier, usually of a transparent plastic called EVA. There is another layer of glass on top, and the back is covered with another plastic like PET. All this is surrounded by an aluminum frame.

This multi-layer construction protects cells from the elements, allowing sunlight to enter, but can be difficult to disassemble when panels have reached the end of their life.

Second Life

Some companies are trying to recover and reuse panels that have lost their effectiveness, or at least salvage some of their components. Reuse is the easiest and cheapest way to “recycle” panels – it requires the least processing and requires the highest price.

The panel can cost around $ 55, and a used panel can be resold for around $ 22. Meng Tao, an engineering professor at Arizona State University and founder of a solar panel recycling startup called TG Companies, could also sell used panel components for up to $ 18.

While some resellers offer used panels for sale to residential consumers, they do not offer significant cost savings. Panels account for no more than half the cost of a residential solar panel, with the rest of the equipment and permits making up the rest. Given that used panels do not generate as much electricity, the money saved on purchasing them may not pay off.

Used panels that cannot be resold are either sent to landfill or recycled. In the absence of federal mandates, Washington recently passed recycling requirements for manufacturers, and other states are now considering doing the same. Meanwhile, the EU is demanding that manufacturers collect and recycle used solar panels and fund research into end-of-life solutions for the technologies they produce.

Some recycling companies can recycle solar panels using mechanical methods. Most of them come off the aluminum frame and grind all glass, silicon and other metals into a mixture called cullet, which can be sold for building materials or other industrial applications.

But cullet is not that expensive – about $ 3 per plate of mix. It is unclear whether there will be buyers for all the cullet produced from recycling large quantities of solar panels, Tao said. The ability to recover pure, valuable materials can make recycling more profitable.

In 2018, recycling company Veolia, based near Paris, opened what it says was the first recycling line designed specifically for recycling solar panels. Located in Rousse, France, the plant also uses a mechanical recycling process, although because it is dedicated to solar panels, more components are recycled separately than plants using conventional e-waste equipment. But some companies are betting that other methods, such as thermal and chemical processes, will be even more efficient.

Extraction of old panels

Founded in 2017, French startup ROSI Solar recently announced plans to build a new recycling plant in Grenoble, France. Yun Luo, CEO of ROSI, says the company has developed a process to extract silver, silicon and other valuable materials from the used panels. The plant is due to open by the end of 2022 under a contract with the French trade association Soren.

Soren is also working with French logistics company Envie 2E Aquitaine, which will try to find other uses for the retired solar panels. If the panels don’t work, Luo said the company will remove the aluminum frame and glass before handing them over to ROSI for recycling.

ROSI focuses on the recovery of solar-grade silver and silicon, as these two materials account for over 60% of the panel’s cost. The company uses a proprietary chemical process on the remaining layers, with particular attention to removing the tiny silver filaments that transmit electricity through a working solar panel.

Luo declined to go into details, but says the company can recover almost all silver in solid form, making it easier to separate from other metals such as lead and tin. Luo says the company is also recovering silicon in a pure enough form to be reused in new panels or batteries for electric vehicles.

Luo says that in order to be profitable, ROSI needs to process at least 2,000 to 3,000 tons of panels per year. Soren expects to harvest around 7,000 tonnes of panels in 2021, and that number is likely to more than double by 2025.