This is a video of a steam locomotive describing it's working principles.
This video explains working principles of Turners Falls Hydroelectric Project and the Northfield Mountain Pumped Storage Project. Both Projects utilize water from the Connecticut River to generate hydroelectric power. We are very proud being involved creating the animation shown in this video.
While Hydroelectric Power Plants using Dam water well known, Pumped Storage power plans are less know. However Pumped Storage Power plants are vital part of any electrical grid system. Since coal and nuclear power plants can't be turned on or off instantly they operate 7/24. The demand for the electricity goes down at night which causes the price of the electricity go down. Pumped Storage Power plants purchase electricity during this time and pump the water to a reservoir which is located at the higher elevation. During the day time when the demand for electricity go up, stored water goes down to the water turbines to generate electricity. In short water in the Pumped Storage stations goes up when the price of the electricity goes down, and the water comes down when the price of the electricity goes up.
While Pumped Storage systems owe their existence to the difference in the price of the electricity between peak and off peak hours. They are still vital for the grid system. Assume for the moment that a wind turbine generate electricity off peak hour. And nobody wants to buy that power. This would make unpredictable green power less attractive. By acting like a giant battery to store electricity Pumped Storage System also regulate the price of electricity.