Mekanism solar generators rely on the vanilla method BlockAndTint#canSeeSky method to determine whether it has clear line of sight to the sky to generate power.

I would expect the solar panel to work even underground if i put a skyweave block in line of sight above the block.

In 1.20.1 that i tested with, that is not the case. It seems to act as an opaque block or something because a generator under the sky works, but putting a skyweave above it (directly or a block or two above) stops the generator from working.

Please see this feature request on the mekanism github

While Mekanism redirected you here, and as someone just randomly commenting on an issue, I feel like it should be up to the mods that add the solar mechanics to decide if something can negate their quirk and have them work underground.

@Therrous normally you would be right, but I think you are slightly misunderstanding. I am asking them to fix a bug with how they interact with a vanilla mechanic. I haven't run the test, but i expect that the vanilla daylight sensor would also not work under a skyweave block due to this behavior, even though it logically should.

Therefore, this is a bug filed here. I do still think it would be cool if mekanism added a way to override the vanilla behavior, but that is a completely separate discussion.