> grid-scale energy storage

This is currently called natural gas. You store it in the ground, and in "day tanks" on land connected to pipes.

Nuclear can also be seen in the same way in relation to renewables.

Batteries are currently much further than I ever thought possible, but still nowhere close to being cost effective enough for most areas.

If you forced every solar or wind installation to have at least 48 hours of nameplate capacity in storage, you would get closer to the true cost of deploying renewables. Right now there is a whole lot of cherry picking going on, where investors are taking the profitable easy stuff, collecting subsidies, and then making the hard expensive stuff someone else's problem.

Right now battery deployments cover the few hour duck curve at best, because that's the only profitable way to deploy them. Hopefully the trend continues though!