Module Recycling

The Fraunhofer Center for Silicon Photovoltaics CSP combines the expertise of two Fraunhofer institutes: the Fraunhofer Institute for Microstructure of Materials and Systems IMWS contributes its expertise in the optimization and evaluation of silicon process technologies and module integration. As the largest solar research institute in Europe, Fraunhofer ISE contributes its expertise in solar cell and module development, in characterization and in the field of recycling.

PV modules are classified as electronic waste according to the “Waste of Electrical and Electronic Equipment” guideline (WEEE guideline 2012/19 / EU). They must therefore be recycled (collection rate 85%, recovery rate 80%). In Germany, more than 60 GWp of PV capacity are currently installed. This corresponds to a volume of over 5 million tons of solar modules. These modules contain a variety of valuable materials that can be recovered. The PV modules currently installed in Germany contain a total of over 3.5 million tons of highly transparent, low-iron flat glass, 600,000 tons of aluminum (from the frames), 150,000 tons of silicon, 25,000 tons of copper and 1,800 tons of silver. The total value of the raw materials contained is over €4 billion. At the Fraunhofer CSP, we have developed recycling processes for the recovery of all inorganic components of solar modules. From the recovered silicon, new crystals can be produced from 100% recycled silicon, processed into wafers and then processed into new PERC solar cells. By recovering these materials, we are helping to improve the sustainability of solar power generation and to secure the supply of raw materials. At the Fraunhofer CSP, we have a wide range of analytical equipment to determine the purity of the recovered secondary raw materials.

Process Development for Recycling Processes

Prozessschema eines Recyclingverfahrens.
© Fraunhofer ISE
Process diagram of a recycling process.

We develop and optimize recycling processes, starting with mechanical disintegration, classification and sorting. We have a wide range of equipment at our disposal in the following areas:

  • Comminution technology:
    • Single-shaft shredder
    • Cutting mill
    • Ball mill
    • Jaw crusher
  • Sorting:
    • Tumbler screen
    • Magnetic tape cutter
    • Electrostatic corona drum separator
    • Air separation table
  • Thermal treatment:
    • Rotary kiln (continuously operable)
    • Muffle furnace
    • Incinerator

By combining various process steps, efficient processes can be developed for different materials.

Wet Chemical Etching

Links: Aus PV-Modulen abgetrennter Solarzellbruch (Mikroskop); rechts: Nasschemisch aufbereitetes Silicium aus Solarzellbruch (Mikroskop).
© Fraunhofer ISE
Left: solar cell scrap separated from PV modules (microscope); right: Wet-chemically processed silicon from solar cell scrap (microscope)

We carry out wet chemical processes on a laboratory and small technical scale (up to 300 liters of etching bath volume) for cleaning or separating materials. By varying the etching regime and process parameters, a wide range of tasks can be processed and mastered. For example, precious metals are recovered from EoL PV modules, or process waste from Si wafer production, such as saw dust or saw cuttings, is cleaned.

Dissolved metals are recovered from used etching baths by chemical precipitation reactions, the use of ion exchangers or electrolysis. Spent etching baths are recycled and reintroduced into the etching process by diffusion dialysis and other membrane separation processes. This minimizes the consumption of chemicals, conserves resources and reduces disposal costs.

Investigation of Impurity Contents in Silicon Using Glow Discharge Mass Spectrometry (GDMS)

Glimmentladungsmassenspektrometer Element GD.
© Fraunhofer ISE
Glow discharge mass spectrometer element GD.
Siliziumprobe mit Sputter-Krater nach Messung im GDMS.
© Fraunhofer ISE
Silicon sample with sputter craters after measurement in GDMS.

We determine the impurity content in solid silicon samples (other matrices possible on request) using glow discharge mass spectrometry (GDMS) down to the ppb range. The spectrometer “Element GD” from the manufacturer Thermo Scientific is used for this purpose. GDMS is a direct solid-state technique in which the sample does not have to be digested (dissolved) beforehand. For the measurement, the surface of the sample is simply polished. The sample serves as the cathode for a glow discharge, which gradually removes the surface. This means that the measurement is spatially resolved and can be used, for example, to create a depth profile. For further solid-state analysis, we use an energy-dispersive X-ray fluorescence spectrometer (ED-RFA). This allows concentrations of elements heavier than sodium to be determined with an accuracy of 0.01-1.0 %. Thanks to flexible sample preparation (e.g. ball mill, single-wire saw), a wide range of sample mixtures can be analyzed.

Other analytical instruments:

  • Particle size distribution
  • Moisture analysis
  • Sieve analysis

More Information on this Research Topic

 

APOLLO

A Proactive Approach to the Recovery and Recycling of Photovoltaic Modules

 

Press Release / February 07, 2022

PERC Solar Cells from 100 Percent Recycled Silicon

 

GreenSolarModules

Strengthening the German PV Industry for Effective Implementation of the Ecodesign Regulation and the EU Energy Label

EoL-Cycle

Development of an Industrial Recycling Process for PV Modules

Fraunhofer CSP