The Intertubes are ablaze with news that the Earth holds 530,000 potential sites for pumped hydro energy storage in its hot little hands. If that sounds too good to be true, well, maybe. The devil is in the details. On the other hand, the number-crunching does indicate that a massive amount of energy storage capacity is already close at hand, even without fancy new breakthroughs in battery technology. The new pumped hydro numbers come from a study by researchers at Australian National University…pumped hydro energy storage refers to pumping water uphill to a reservoir. After that, gravity does all the work. The stored energy — in the form of water — is let loose on turbines to generate electricity on demand. Pumped hydro has limited utility when fossil fuels do the pumping. It is mainly used for load balancing, meaning the reservoir typically refreshes once a day. With renewables on the scene it’s a whole new kettle of fish. In a mixed grid, pumped hydro facilities respond to shifts in wind and solar production as well as demand.