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[Off-grid] Solar-grade silicon
refers to silicon crystals which have a sufficiently high grade of purity to be used in photovoltaic applications. The chemical element silicon is a semi-conductor and forms crystals with a resistant diamond structure. It is the second most common element in the earth's crust after oxygen. For processing in the solar sector, raw silicon is purified to achieve solar-grade silicon and then cast into blocks for further processing into wafers.
SolarWorld : Solar glossary
solar power systems which are not connected to an electricity network. The electricity produced is consumed or stored directly on site (so-called stand-alone systems).