The PV manufacturers themselves say its 4. Those studies you mention say you could make them at 10-30 in theory if you could somehow purify the poli-silica differently. If we made PVs in the west with natural gas (and carbon recapture), perhaps it could get to that number (but perhaps not). However, PVs aren't made in the west and the poli-silica isn't purified with gas but instead using coal. That's why those numbers are different. And for reference, we could have made those PVs in the west, however politicians chose not to.
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The PV manufacturers themselves say its 4. Those studies you mention say you could make them at 10-30 in theory if you could somehow purify the poli-silica differently. If we made PVs in the west with natural gas (and carbon recapture), perhaps it could get to that number (but perhaps not). However, PVs aren't made in the west and the poli-silica isn't purified with gas but instead using coal. That's why those numbers are different. And for reference, we could have made those PVs in the west, however politicians chose not to.