I agree that hydro appears to be the only viable storage tech at the moment, but I worry that expanding it will cause significant damage to the environment. I don’t think new dams will get support in rich countries anymore because of this.

There is one solution you missed out: an expansion of nuclear energy to provide low-carbon electricity that doesn’t suffer from the duck curve. Advanced design’s such as Moltex look to combine with “solar salts” so that energy can be stored as heat and called on to meet peak demand (i.e. run as peakers). What do you think?