[freebeard]

Solutions are obtained by prioritizing storage for heat (in soil and water); cold (in ice and water); and electricity (in phase-change materials, pumped hydro, hydropower, and hydrogen), and using demand response. No natural gas, biofuels, nuclear power, or stationary batteries are needed.

Their missing the best opportunity, gravity. It's everywhere and it's cheap.

https://duckduckgo.com/?q=energy+storage+with+gravity

Gravitational potential energy storage with solid masses
Changing the altitude of solid masses can store or release energy via an elevating system driven by an electric motor/generator.

Companies such as Energy Cache and Advanced Rail Energy Storage (ARES) are working on this.[15][16] ARES uses rails to move concrete weights up and down.[17] Stratosolar proposes to use winches supported by buoyant platforms at an altitude of 20 kilometers, to raise and lower solid masses.[18] Sink Float Solutions proposes to use winches supported by an ocean barge for taking advantage of a 4 km (13,000 ft) elevation difference between the surface and the seabed.[19] ARES estimated a capital cost for the storage capacity of around 60% of pump storage hydroelectricity,[20] Stratosolar $100/kWh[21] and Sink Float Solutions $25/kWh (4000 m depth) and $50/kWh (with 2000 m depth).[19]

Potential energy storage or gravity energy storage was under active development in 2013 in association with the California Independent System Operator.[22][23][24] It examined the movement of earth-filled hopper rail cars driven by electric locomotives) from lower to higher elevations.[16]

ARES claimed advantages including indefinite storage with no energy losses, low costs when earth/rocks are used and conservation of water resources.[16][25]

https://en.wikipedia.org/wiki/Energy...energy_storage