Process energy will still be a lot cheaper than .08 US$/kWh in China. I doubt they process glass with electric ovens. OTOH that is primary energy then, which kind of supports your argument. Still other emissions in the silicon supply chain that cause global warming are also relevant. If I find the time, I‘ll look for recent LCA.
I'm delighted to see Fraunhofer's report! I'll read it carefully.
You are probably right about the glass. Processing glass in electric furnaces has been a well-established technology for many generations, but it is more expensive than fossil-fuel-fired furnaces, and is used for making more expensive kinds of glass. But the glass in solar panels is an especially cheap kind of glass.
Coal is probably the cheapest form of energy.
https://www.coal-price.com/ says that currently in China coal is on the order of US$100 per tonne. Coal has up to 33MJ/kg, so that works out to 0.3¢ per megajoule, or 1.1¢ per kilowatt hour, or more if the US$100/tonne coal isn't the best anthracite. You probably can't literally run a glassmaking furnace with a coal firebox, because of the contaminants from the coal, but you almost certainly can't run it on cheaper energy than that. If 100% of the cost of the solar panels were coal energy instead of electric, that would extend my upper bound out from 7 months to a bit over 4 years.
This seems to be in rough agreement with Fraunhofer's more informed estimate that you cite.
