[schiffern]

Even pumped hydro is pretty small for seasonal storage.

Probably the only economical approach will be some sort of factobattery[1], which can be thought of as a flow battery which operates "once through" to avoid round-trip losses. Instead of outputting electricity, the beneficiated material itself is the economic output.

This eliminates the entire chemistry-to-electricity side of the process, which may require dissimilar equipment under some approaches.

[1] https://www.moderndescartes.com/essays/factobattery/

[PaulHoule]

When I try to model out an all-renewable grid I think of it this way: capital cost is the sum of generation capital cost + storage capital cost + transmission capital cost.

In the winter you get less energy from your solar panels, one answer to that is build enough storage to shift energy from summer to winter, another is to build an excess of solar panels. In the latter case you need less storage but you have an excess of cheap energy in the summer you can do something with (e.g. factobattery, desalinating water, making e-Fuels, e-Fertilizers, etc.)

To realize that benefit you need additional investment in transmission (with an option of locating sinks close to sources to minimize transmission cost) Also the capital cost of any facility that you run 50% of the time is effectively doubled.

I have yet to seen a cost analysis of a 100% renewable + storage system as it needs a detailed analysis. One problem is that you occasionally have the bad luck of an extended patch of unfavorable weather. It's going to cost more to build a system that runs out of juice once every 20 years compared to one that runs out of juice every year. Advocates of renewable + storage systems claim to be a lot cheaper than AP-1000, my back of the envelope calculation is that that renewables + storage might be a little cheaper than AP-1000 under favorable assumptions, but I haven't done detailed enough modelling to have much confidence in that and I haven't seen anyone else do it.

[herewego]

Distributed energy resources eliminate a large portion of the transmission cost, leaving only the distribution grid in an idealized/future-state scenario (as I assume you’re talking about). In the summer, you lower the solar output so as not to overload the s distribution grid.

Also, batteries come in several long-term flavors. Thermal sand batteries are able to provide many months of energy storage today. A mid-term future will surely include even longer term storage as we develop improved storage technology. LiPo batteries are a bridge storage solution.