Keeping solar out of landfill

Materials World magazine
24 Sep 2018

Solar panels installed around the turn of millennium will reach their end-of-life in 2030, creating a surge of photovoltaic waste. Ellis Davies reports on a technology that could recycle the out-of-date modules.

It is common to see the roofs of houses and other buildings adorned with solar panels – but with the technology advancing quickly, where will the out-dated systems go? In answer, German engineering company Geltz Umwelt-Technologie (GU) has developed a recycling plant to process up to 50,000 obsolete solar modules per year, recovering over 95% of the recyclable materials. The technology could improve the economic viability of solar panels both on an industrial and commercial scale by reducing the amount of materials that end up in landfills.

In the early 2020s, a wave of end-of-life solar modules will begin to hit European waste streams, an inflow that is expected to continue until 2050. Solar panel recycling has been minimal due to practicality and cost issues as the polymer layers that encapsulate the modules made mechanical separation impossible. However, the materials can be recycled once the polymer is removed. GU employs a pyrolysis process – a thermal decomposition of materials using high temperatures – to get rid of the polymer layers, allowing for electrolytical separation – the use of a direct current to separate material.

Fabian Geltz, Process Engineer at GU, told Materials World, ‘After pyrolysis of the polymer layers, the glass, solar cells and filler material are separated with a mechanical sieve system. The solar cells are further treated by metal stripping and electrolysis to separate the silicon and retrieve the metals in a pure form.’ This is done using a pyrolysis reactor, a mechanical separator, and several electrolysis cells and chemical vessels for metal recovery. Waste heat from the pyrolysis process is pumped back into the reactor, which can treat one tonne of solar module waste at a time.

Most of the materials can be re-used in electronic devices, whereas the recovered silicon is mainly applicable to the steel and aluminium industries as an additive for cast materials. ‘The status quo is to simply dismount the cables, aluminum frame and covering cables – the rest of the module has to be landfilled, which is not sustainable,’ says Geltz. ‘Without achieving sustainability in the whole lifecycle of the modules, solar technology won’t be credible as a solution for environmental problems.’

Growing a plant

The plant came to be after a ‘major recycler’ approached GU with the idea. The company requested EU funding via Horizon 2020, and was successful. ‘At first, we made experimental runs on laboratory and small scale, regarding the pyrolysis process, then built the industrial scale plant using the result,’ Geltz explained. ‘The mechanical separation and electrolysis was developed parallel to the pyrolysis process, using established technology.’

Currently in a test phase, the plant is processing at only a fraction of its full capacity, in order to slowly gather data about the process and ensure safe operations. Going forward, the aim is to ramp up production to reach max capacity with one pyrolysis reactor by the end of the year. A second reactor is slated for installation in 2019. GU has plans to build more plants in Europe in the future, which it believes will be aided by the experience gained with the first plant.