Pumped Hydro Dominates Energy Storage

At least 30 per cent of the wind farm sites west of the Mississippi River have topography and water resources suited to the development of closed loop pairs of upper and lower pools as bermed lagoons, usually within 1 km of each other and net operating heads of over 30 meters.

For example, for a PSH system matching the annual gross generation capacity of a 150 MW wind farm (about 3 or 4 times as large as would be needed for simply arbitraging of the off-peak low value wind generation), the civil infrastructure (lagoon construction and bottom sealing, plumbing, water source wells and erosion control structures) costs about $0.25 per watt; the hydro generation/back-pumping component and electrical connection to the wind farm's grid is about another $0.25 per watt, a combined expense that is 10 to 20 per cent of the original expense for the wind farm.

The round trip operational electrical efficiency, including the periodic replenishment of the water lost to evaporation and, less, to seepage, is about 75 per cent, considerably more than other methods at competitive costs per watt. Of course, the low value generation of wind farms on the regional grid, but lacking PSH on site could be transmitted to regionally contiguous sites with surplus PSH capacity.