Gravitational Potential Energy

• Hydroelectric power plants that house turbines nearly always sit below a large water source, typically a damned reservoir. The lower elevation of the plant insures that the water above will supply enough gravitational potential energy to flow down into an inlet pipe at very high pressure. The gravitational energy of the water pressure is static, subject only to slight variations in water volume. The operation of a turbine starts with this energy provided by gravity and the water's mass.
  
  

Kinetic Energy

• Penstocks consist of very large inlet conduits or pipes that transport water from a reservoir to a turbine. The conduits or pipes taper into smaller diameters until they reach a valve gate just before the turbine. The valve gate contains a higher pressure nozzle that converts the inflow of water into a jet stream; the jet stream is powerful enough to strike the turbine blades and move them. This force used to drive or push the turbine blades is a result of kinetic energy.
  
  

Rotational Energy

• Water turbine blades are attached to a large generator shaft through a central axis. The pressure and force of water exerted on the blades from the high-pressure nozzle rotates the turbine shaft to spin at a high rate. Thus the high-speed jet of water begins its journey with a straight stream of high pressure, then its energy is transformed into mechanical, rotational energy.
  
  

Hydroelectric energy

• In a hydroelectric turbine generator, the turbine shaft is connected to a rotor; this rotor spins at a constant speed. As the rotor spins it causes powerful electromagnets to move past a series of conductors mounted inside a large ring; the outside ring is called the stator. When the magnets move past the electromagnets at high speed, they produce a flow of electricity, which is then transferred to the generator output terminal. In this way, rotational speed creates hydroelectric energy for the generator.