Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS
Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS

SiSil

Utilisation of urban silver and silicon sources

© pixabay

Old PV modules: Germany's most important source of silver and silicon

Photovoltaic modules (PV modules) are the largest urban source of secondary silicon and secondary silver in Germany. Each tonne of a PV module contains approximately 30 kg of silicon and up to 0.5 kg of silver. However, procuring both raw materials is challenging due to their dependence on imports.

The primary production of raw silicon is not only energy-intensive, but also burdensome in terms of CO₂ emissions. The recycling of secondary silicon and secondary silver could not only provide greater independence, but also bring economic and ecological benefits.

However, current recycling processes hardly recover these two raw materials as pure, reusable secondary raw materials, which is why there is an urgent need for action here. Due to the sharp increase in the return of PV modules that have reached the end of their life cycle (end-of-life), we must take action to recover raw materials, reduce environmental impact and decrease dependence on imports.

How SiSil aims to close the loop

The project aims to develop a scalable, economical process chain for recovering silver and silicon from end-of-life PV modules without energy-intensive thermal layer separation. This is achieved through:

  • High-throughput mechanical processing and sensor-based separation of module fractions
  • Hydrometallurgical extraction of metals with maximum recycling and regeneration of process chemicals
  • Reintegration of secondary silicon into industrial processes, in particular the production of chlorosilanes
  • Data-based business models and a recycling network that closes the entire value chain

Project objectives:

In order to reduce dependencies, lessen environmental impact and recover raw materials, the following objectives have been specified for the project:

  • 90 per cent recovery of silver and silicon from old modules
  • Technical testing with at least 10 tonnes of input material
  • Secondary silicon with at least 98 per cent purity should be economically competitive with primary silicon
  • Optimisation of the CO₂ footprint of secondary silicon: this can be less than a third of that of primary silicon, thereby significantly improving the ecological balance
  • Development and construction of a pilot line for metal and silicon recovery on an industrial scale
  • Establishment of a resilient recycling network with primary recyclers and buyers
© Fraunhofer IWKS
Cut-off old PV module
© Fraunhofer IWKS
Various material fractions from PV module recycling (fine fraction left; coarse fraction right)
© Fraunhofer IWKS
Recovered PV glass

Expected project results:

  • Industrially scalable process that enables true recycling instead of downcycling, thereby returning high-quality silver and silicon
  • Marketable secondary raw materials: silver (e.g. for electrical appliances) and silicon
  • Significant reduction in materials that were previously thermally recycled -> higher value creation of plastic and fine grain fractions
  • Prove economic viability on an industrial scale in order to build further annexes and locations
  • Contribution to security of supply in Germany: reduction in import dependency and noticeable CO₂ savings through the recovery of raw materials from PV modules
  • Transferability of the separation and processing processes to related applications (e.g. fuel cells) and impetus for further regulatory developments

 

SiSil closes the cycle of PV raw materials by turning silver and silicon into a competitive resource.