Flywheels, superconductor storage or supercapacitors are somewhat more efficient [1], but they are an order of magnitude more expensive per unit of energy they

Flywheels, superconductor storage or supercapacitors are somewhat more efficient [1], but they are an order of magnitude more expensive per unit of energy they can store. (Thousands of dollars per kWh capacity, rather than $200-$300.) The real competitor is Li-Ion batteries which now cost about the same as pumped storage, and have similar cycle efficiency. Problem is the capacity decline after a few hundred cycles, which is unfortunate if you want to build infrastructure that is low-maintenance and survives decades. If you are interested in the area, this blog post gives some thoughts to implications [2] though it is a bit outdated by now. [1] https://www.researchgate.net/figure/Comparison-of-various-EES-technologies-in-cycle-efficiencies-4_fig5_283831474 https://www.researchgate.net/figure/Comparison-of-various-EE... [2] https://dothemath.ucsd.edu/2011/08/nation-sized-battery/ https://dothemath.ucsd.edu/2011/08/nation-sized-battery/