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Components of a hydroelectric power plant

Short answer

A hydroelectric plant uses a reservoir and dam for storage and head; intake with trash rack and gates; penstock to deliver water under pressure; a turbine (impulse or reaction) converting water energy to mechanical; a generator; a draft tube for reaction turbines recovering kinetic energy and allowing placement above tailrace; and a tailrace channel.

With the help of a neat layout, describe the essential components of a hydroelectric power plant and state the function of each.

A hydroelectric plant converts the potential energy of water stored at a height into electricity. Power available is P=ρgQHηP=\rho g Q H\eta.

  Reservoir
  ~~~~~~~~~~~|  Dam            Surge tank
  ~~~~~~~~~~~|====+             |
  ~~~~~~~~~~~|    Intake  ______|_____
  ~~~~~~[Trash   rack]--/ Penstock    \
         [Gate]                        \
                                       [Turbine]=[Gen]
                                        |
                              Draft tube|  Tailrace -->
                                       ~~~~~~~~~~~~~~

Essential components

  1. Catchment area and reservoir: collects and stores rainfall and river water. Its storage gives the control of flow through the year.
  2. Dam: raises the water level to create head and storage. Types: gravity, arch, buttress, earth or rockfill. It has a spillway for passing flood water safely.
  3. Intake structure with trash rack and gates: takes water into the waterway. The trash rack keeps out logs and debris; gates control and stop the flow. A silt-settling basin (desilter) is also used on rivers carrying silt.
  4. Headrace (canal or tunnel): carries water from the intake to the forebay or surge tank.
  5. Forebay or surge tank: the surge tank is a vertical open chamber near the penstock. It absorbs pressure rise (water hammer) when the turbine gates close suddenly and supplies water when load increases.
  6. Penstock: a steel or reinforced concrete pipe taking water at high pressure from the forebay to the turbine.
  7. Powerhouse: contains the turbines, generators, governors, control panel, and cranes.
  8. Water turbine: converts water energy to mechanical energy (Pelton for high head, Francis for medium, Kaplan for low head).
  9. Generator: coupled to the turbine to produce electricity.
  10. Draft tube (reaction turbines): a diverging pipe below the runner which allows the turbine to be set above the tailwater level and recovers the kinetic energy of the exit water.
  11. Tailrace: channel carrying the used water back to the river.
  12. Switchyard and transformer: step up voltage for transmission.

✓ Answer checked by Claude Sonnet 5.5

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