Stacking concrete blocks is a surprisingly efficient way to store energy
I would think storing energy using compressed air would be more practical.  Excess electricity pumps air into a compressed air tank. When electricity supply is low, the compressed air is released turning a turbine to generate electricity. It's basically the same principle as the pumped hydro mentioned in the article but using compressed air. The advantages are size, cost, and availability. You can put it anywhere and scale when necessary.