Their container, at least the inner layer contacting the molten silicon, is all graphite. That will also burn dramatically. Keeping atmospheric O2 out of the system would be a key engineering requirement.
Using 'renewable energy' on earth is a dumb liberal pipe dream, but this might make sense for a moon base. Plenty of real estate to site a solar mirror site there without killing any birds or turtles. Collect energy for two weeks, store half in molten silicon and recoup that the next two weeks. May need to import the graphite and some of the other working parts from the earth, but the silicon can be sourced from moon itself, saving megabucks. And no O2 worries with the lunar vacuum. The moon there has no hydropower and no fossil fuels (and wouldn't want to waste O2 on latter even if they existed) so the main alternative to solar would be nuclear, which has its own cost issues.