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Silicon kerf loss recycling

Objective

Solar energy direct conversion to electricity is expanding rapidly to satisfy the demand for renewable energy. The most efficient commercial photovoltaic solar cells are based on silicon. While the reuse of feedstock is a severe concern of the photovoltaic industry, up to 50% of the valuable resource is lost into sawdust during wafering. Presently, the majority of silicon ingots are sliced in thin wafers by LAS (loose abrasive sawing) using slurry of abrasive silicon carbide particles. The silicon carbide is not separable from the silicon dust in an economical way. The newer FAS (fixed abrasive sawing) uses diamond particles fixed to the cutting wire. It is expected that FAS will replace LAS almost completely by 2020 for poly/mono-crystalline wafering. The intention of the proposed project is to recycle the FAS loss aiming at a sustainable solution. The main problem is the large surface to volume ratio of micron size silicon particles in the kerf loss, leading to formation of SiO2 having a detrimental effect on the crystallisation. The compaction process developed by GARBO meets the requirements of a reasonable crucible-loading factor. Overheating the silicon melt locally in combination with optimised electromagnetic stirring provides the means to remove SiO2. The technology developed by GARBO removes the organic binding agents, leaving about 200 ppm wt diamond particle contamination. If untreated, the carbon level is above the solubility limit. Formation of silicon carbide and precipitation during crystallisation is to be expected. The electromagnetic mixing, in combination with the effective means to separate electrically non-conducting silicon carbide and remaining SiO2 particles from the silicon melt by Leenov-Kolin forces and the control of the solidification front, is the proposed route to produce the solar grade multi-crystalline silicon blocks cast in commercial size in a unified process.

Call for proposal

FP7-ENV-2013-two-stage
See other projects for this call

Coordinator

HELMHOLTZ-ZENTRUM DRESDEN-ROSSENDORF EV
Address
Bautzner Landstrasse 400
01328 Dresden
Germany
Activity type
Research Organisations
EU contribution
€ 395 922
Administrative Contact
Rainer Maletti (Dr.)

Participants (4)

GARBO SRL
Italy
EU contribution
€ 284 282
Address
Via Prati Nuovi 9
28065 Cerano No
Activity type
Private for-profit entities (excluding Higher or Secondary Education Establishments)
Administrative Contact
Ilaria Lombardi (Mrs.)
UNIVERSITA DEGLI STUDI DI PADOVA
Italy
EU contribution
€ 262 574
Address
Via 8 Febbraio 2
35122 Padova
Activity type
Higher or Secondary Education Establishments
Administrative Contact
Andrea Stella (Prof.)
UNIVERSITY OF GREENWICH
United Kingdom
EU contribution
€ 233 396
Address
Old Royal Naval College, Park Row, Greenwich
SE10 9LS London
Activity type
Higher or Secondary Education Establishments
Administrative Contact
Alison Yakub (Ms.)
ELEKTRISCHE AUTOMATISIERUNGS- UND ANTRIEBSTECHNIK EAAT GMBH CHEMNITZ
Germany
EU contribution
€ 225 324
Address
Gottfried-schenker-strasse 4
09244 Lichtenau
Activity type
Private for-profit entities (excluding Higher or Secondary Education Establishments)
Administrative Contact
Heinz Steinbach (Prof.)