Rezultaty A direct route to produce solar grade silicon at low cost General objectives of the project were to research and develop a new two-step high- temperature process for solar grade silicon (sog-Si) production, to test the processing and conversion efficiency of solar cells made from SolSilc material, to evaluate an approach for scale-up and to investigate relevant technical, environmental and economical aspects. After the SolSilc project a pilot demonstration on scale (several 100tons/a, 2 years) is anticipated, in order to achieve a competitive market price below 20Euros/kg.sog-Si at a scale of 5000mt/y. In the new 2-step high-temperature process, silicon metal is formed from high-purity quartz from natural deposits and from very pure carbon black, with silicon carbide as an intermediate product. In a rotary plasma furnace, pellets of quartz and carbon black are reacted to form silicon carbide. In the second furnace, an electric arc furnace, the reaction of quartz and silicon carbide leads to the formation of silicon melt. This melt is saturated with carbon, which is removed in a subsequent purification process. The attractive features of the SolSilc-process are its expected low cost and low energy consumption. For the second high-temperature step, a furnace was designed and constructed at ScanArc for a production of 20kg silicon per hour. This furnace has been operated with high-purity linings but not yet completely clean starting materials. Hence, the metal produced thus far had not yet the required purity for solar grade silicon. This furnace has been operated under steady-state conditions for periods up to 36 hours, during which more than 80kg of silicon was produced, with multiple tapings of the formed metal. The furnace was placed in a newly constructed clean-room at the ScanArc premises. The carbon-saturated melt is subsequently treated by a combination of three methods to reduce the carbon concentration from several hundred to 2-5ppmw. These methods are, respectively, controlled SiC precipitation, oxidative gaseous purging and directional solidification. Individual purification tests of the different methods were performed in SOLSILC and the effectiveness was demonstrated. From literature data and from chemical analysis of commercially available PV wafers, a minimum specification for solar grade silicon has been derived. The chemical composition of SolSilc silicon has been estimated from the composition of the starting materials and the expected segregation during the process. The tolerance of cell performance for specific impurities has been investigated by making solar cells from intentionally contaminated EG-silicon. The results indicate that it should be possible to obtain good cell performance on wafers made from SolSilc silicon. An environmental evaluation and an LCA were made of the SolSilc process and competing routes towards solar grade silicon. Criteria used are availability of resources, energy consumption, safety and emissions to the environment. The SolSilc process is expected to be the environmentally most benign process. Wyszukiwanie danych OpenAIRE... Podczas wyszukiwania danych OpenAIRE wystąpił błąd Brak wyników
