> we still need a rotating chunk of steel to stabilise the grid
No we don't. Battery systems can stabilize the grid. You need inverters that are designed for this, but it isn't hard to make an inverter that will set then grid frequency and force it correct. You want most inverters to follow the source, but something needs to set it.
Most rotating steel isn't setting grid frequency either, an induction motor follows the frequency of the grid, and generates power if it is rotating faster than the grid frequency. (this is much more complex, but close enough for a quick comment).
No we don't. Battery systems can stabilize the grid. You need inverters that are designed for this, but it isn't hard to make an inverter that will set then grid frequency and force it correct. You want most inverters to follow the source, but something needs to set it.
Most rotating steel isn't setting grid frequency either, an induction motor follows the frequency of the grid, and generates power if it is rotating faster than the grid frequency. (this is much more complex, but close enough for a quick comment).