The main point of these systems is to store energy for months without much loss. Considering the cooling costs of the mechanism you mentioned, it only seems via

The main point of these systems is to store energy for months without much loss. Considering the cooling costs of the mechanism you mentioned, it only seems viable for more rapid usage situations ie. the middle ground between fast discharging batteries and slow discharging hydro gravity storage. The beautiful thing about gravitational storage is that it is reversable. So the same pump that used energy to pump the water into a tank 20 stories up can also spin down as water pours through the turbines, acting as a hydroelectric generator as the water is released. Having a single reversable mechanism makes these systems pretty easy to maintain and the only places energy is lost is through friction during conversion and through leaks. They are pretty hard to beat. The idea of deep ocean pods is similar in execution but instead of working solely against and with gravitys energy potential, the water pressure is used as well...its just more compact..but the orbs will need to be well built to withstand insane pressures.