It's easy to make renewables look cheap if you assume some wundertech makes storage free. Will thermal storage, synthetic methane, or who knows what else fulfill this need? Who knows, but they don't yet. Thus renewables only present a solution coupled with an engineering breakthrough. It's like assuming moore's law held true and developed an app that assumed it'd run on a 1THz single-core processor presumably developed a decade in the future. Seems reasonable in 1995, but that's have been a very bad bet.
1. https://en.m.wikipedia.org/wiki/Pumped-storage_hydroelectric...
To recover energy, this is reversed, with the temperature difference driving the cycle in the other direction. Detailed calculations with inefficiencies show an overall round trip efficiency of 60% or better could be achieved. All the temperatures are below the creep limit of ordinary steel, so this system would require no exotic materials whatsoever.
It's also possible to design a thermal storage system without the cold store, using the ambient environment as a heat sink when running the generator. In that case, adding a backup heater (burning hydrogen, say) would make the store double as a backup generator at extremely low extra capital cost.
We solve climate change by raising CO2 costs high enough. Again, this is not a go-no go thing, it is just haggling over the price.
> We're already at the point where markets are starting to see saturation with renewables.
This just means CO2 taxes aren't high enough. BTW, they'd have to be $300-400/ton for new nuclear to compete with gas in the US.