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ENERGIX-Stort program energi

CONtrol of the STRUCTure for high purity and energy effective solar grade silicon feedstock production

Awarded: NOK 6.7 mill.

Elkem Solar is developing Solar Grade Silicon (SoG-Si) Feedstock based on a proprietary metallurgical refining process. Solar grade feedstock has been gaining market acceptance as the quality requirement are better known and its application during ingot c asting has shown that similar solar cell efficiency can be achieved using other types of feedstock. With production facilities in Norway, Elkem Solar can only be competitive if it maintains its technological advantage by rapid continuous improvement combi ned with step change R&D. It is essential that Elkem's Solar Grade Silicon feedstock keeps up with future advances in solar cell concepts compared to other higher purity feedstock processes. The present project is focused on the final route step of solar grade silicon: final refining by ingot casting. The main challenges of the (directional) casting method as final refinement step in Elkem's process are: i) the less efficient refining due to the in-take of impurities due to the destabilization of the crys tallization front, the presence of grain structures and grain boundaries, and ii) the precipitation of particles due to the higher amounts of impurities. Moreover, current technological solutions rely on a good control of the heat transfer in the furnace adjusted by additional heating of the ingot. This, however, results in increased energy consumption. It is the aim of this project to increase the efficiency by control of structure formation within the ingot (grain size and particles). An ambitious targe t is to i) achieve grain sizes in the 5 cm range (today < 1cm), ii) suppress particle precipitation over 90% of the useable ingot volume, and iii) reduce the energy consumption by 20%. Elkem's strategy to reach these goals is a combination of novel energy efficient and modular control of heat extraction in the crystallization furnace and the use of 3D modelling tools for process design and control.

Funding scheme:

ENERGIX-Stort program energi