  Upgraded metallurgical grade silicon (UMG-Si) for photovoltaic (PV) solar
applications has been manufactured through the metallurgical route by means of
the process developed by Ferrosolar. In an ambitious mass production test,
performed in commercial solar cells and modules production lines, the silicon
was proven to be appropriate for photovoltaics applications (Fornies et al.,
2019 Mass production test of solar cells and modules made of 100% umg silicon.
20.76% record efficiency. Energies 12), reaching, in a conventional production
line, up to 20.76% of solar cell efficiency with multicrystalline cells made of
100% UMG silicon. In this paper we present more results from the mentioned
massive test. Defect engineering is being applied to improve the bulk lifetime
of the UMG wafers and to guide in the identification of the limiting defects in
the material. Moreover, the modules produced with 100% UMG silicon solar cells
were installed together with the modules produced in the same production line
with polysilicon material to assess the degradation of the UMG silicon when
compared to polysilicon. After 24 months of outdoor PV generation, the
degradation, in terms of Performance Ratio at 25C (25PR) diminution, has been
the same for both types of modules. Additionally, a Life Cycle Assessment (LCA)
has been performed for this UMG silicon and state-of-the-art Siemens
polysilicon to compare the environmental impact of both silicon feedstocks. The
results presented in this paper; chemical analysis of wafers, defect
engineering, low degradation, average efficiency and environmental assessment,
lead to a complete study of UMG silicon, confirming its potential to be used as
raw material for PV applications.
