If the numbers in the parent post are true, then you'd probably still be better off just pumping the water high up with that energy and letting it fall down when the energy is needed. On the other hand nabla9 quoted numbers that look very good.
BTW one solution is to use existing hydro dams as partners to wind/solar, add extra generation capacity to the dams, share the transmission infrastructure between the wind/solar/hydro and simply let the dams fill when the wind blows/sun shines. That's more efficient than pumped storage