Utilizing water towers for pumped storage hydropower*

Pumped storage hydropower (PSH) stores electrical energy as gravitational potential energy. Water is pumped from a lower elevation reservoir to a higher one and later flows back to the lower reservoir through a turbine. For areas with naturally large elevation changes, PSH has been an effective way to store excess energy produced from renewable sources by pumping water into the higher reservoir during times of lower energy consumption (off-peak, lower associated energy cost) and discharging during times of higher energy consumption (peak, higher associated energy cost). However, areas that have relatively small elevation changes (such as the Midwest of the United States) require man-made height differences for PSH. Water towers could provide one method for obtaining the required height differences. Here, three different commercially available water tower designs (small, medium, and large) with varying pipe diameter and Pelton Wheel Turbine nozzle diameter are examined numerically to determine an optimal system configuration for energy storage. Maximum water level and Pelton Wheel blade angle are held constant across the three different water towers considered. The results suggest that each of the water towers considered has a maximum energy capacity that can be achieved with multiple combinations of pipe and nozzle diameter. Finally, historical data for differences in energy prices from the Midwest Indiana hub is used to estimate energy cost savings for the water tower PSH system.