Silicon kerf recycling

The base material used in the production of PV modules is photovoltaic-grade silicon (PV-Si). This material suffers a major lost of value during one of the first steps of the manufacturing process. Indeed, the silicon wafers that are the basis of photovoltaic cells are produced by sawing a silicon ingot into very thin slices (less than 200 µm thick) with the help of a diamond wire. During this process, more than 40% of the material is lost as micro-chips of silicon flushed by a sawing liquid. The sludge created this way is called “kerf” and is composed of ultra-pure silicon. Unfortunately, it is currently considered as waste and is discharged at the manufacturer’s expense.

The technologies developed by ROSI Solar allow for the revalorization of this kerf. On the one hand, these processes fully separate the fine silicon particles and the sawing liquid. This liquid can thus be reused for ingot slicing instead of being treated as wastewater and released in the environment. On the other hand, the silicon particles are washed from the impurities generated during the sawing process and then reconditioned as ultra-pure silicon granules. These granules can then re-enter the manufacturing process upstream the value chain in order to produce new silicon wafers.

In 2019, the newly installed solar capacity reached 115 GW worldwide. Thus, the photovoltaic modules production resulted in loosing about 200 000 tons of photovoltaic-grade silicon discarded as waste, accounting for a lost value of 1.5 Bn USD. ROSI Solar’s technologies aim at strongly reduce this financial loss but also to cut down the greenhouse gas emissions triggered by the production of raw materials for the photovoltaic industry.