Renewable energyHydroelectric

Hydropower is electricity produced from flowing water. Hydropower produces approximately 7% of U.S. energy (19% of world energy) and accounts for 45% of total renewable energy in the U.S. Newer technologies harness energy in ocean tides, waves, and currents.

Hydroelectric level and flow applications

• SURGE TANK: The main function of a surge tank is to control pressure
  variations due to rapid changes in the velocity of water. When the
  power turbine is running at a steady load, there are no surges in the
  flow of water since the quantity of water flowing through the conduit is
  sufficient to meet the turbine’s requirements. When turbine load
  decreases, a governor closes the gates of the turbine to reduce water
  supply. The water is routed for storage in the surge tank—an action that
  prevents the conduit from bursting. When turbine load increases,
  additional water is drawn from the surge tank to meet the increased
  demand. A surge tank’s internal diameter may range from a few feet to
  several dozen feet. The tank relies on a level sensor to determine
  whether or not water stored in the tank should be removed.
• PUMP PROTECTION: Flow Switches protect pumps from damage due to
  leaks or if a valve is accidentally closed downstream. A switch will
  actuate an alarm and shut down the pump when flow drops below the
  minimum rate.