Conventional hydroelectric plants use gravity and the potential energy stored in an elevated reservoir of water to force water through a turbine and generator. There are over 225 small conventional hydroelectric generators that are in operation across the state of Michigan.[*] The Ludington Pumped Storage Plant is a much larger hydroelectric facility — reported by Consumers Energy as having a total nameplate capacity of 1,875 MW — that is in the midst of an upgrade and expansion. Consumers Energy reports that, when completed, the station’s capacity will be expanded to 2,172 MW.
In the evening, when electricity prices are relatively low, the Ludington Pumped Storage Plant reverses its turbines and consumes electricity to run pumps and move water from Lake Michigan, uphill and into a 1.3 square mile reservoir. That water is held in the reservoir until the next day, when electricity prices are higher, or there is a need for additional generation capacity. Then, the water is released, and run back through the generators to produce electricity that is fed into the state’s grid. The water in the reservoir effectively acts like a big battery that is recharged when electricity prices are low and depleted when they are higher.
[*]The average nameplate capacity of Michigan’s conventional hydroelectric generation is 1.6 MW. The largest producer is 11.5 MW. Source: U.S. Energy Information Administration, Form EIA-860.