How much silicon is there, in kg, in a 1kw panel? Thanks!
Fthenakis has published more on the subject than anyone, to my knowledge. His LCA lists a whole bunch of factors, but it's roughly 1.5kg of silicon in the PV itself.
But a module also has 16.1kg of tempered low-iron glass for a 210 Wp panel (p32). Glass is 60-80% silica, and silica is about half and half silicon and oxygen by weight. So there's 5kg - 6.5kg of silicon in the glass.
I'm not sure there is such a thing as a 1kW panel - it would be 5-7 square metres in size.
However, we can consider 1kW to be a useful unit - typically about five panels' worth - and that, very roughly speaking, would be roughly 40kg of silicon.
This isn't a sustainability issue though: not only are silicon cells recyclable, but the earth's crust is about 10% silica - it's one of the most abundant compounds on the planet.
I am replying to a necrothread here, but as this is one of the first hits that came up in Google, I'm going to post for future readers.
The number for the cell itself appears to be about 1/2 that mentioned in the answer by EnergyNumbers. According to this calculator at least.
They calculate a typical 6" (153mm) cell of 200um thickness to be 11g. A typical panel is 60 cells, so that would give us about 650g of pSi. Modern panels are around 350W, so around 2kg of pSi.
However, a 2018 report suggests the average thickness of a modern cell is closer to 175um. But they also report directly, 4g per Wp. So then we can directly calculate 4kg per 1000W of panel.
So I think it's safe to say it's somewhere between 2 and 4 kg per kW of panel, and likely closer to the later figure.