Based on power which is produced, hydro power is divided into several types:

  • Large-hydro              : more than 100 MW
  • Medium-hydro         : between 15 – 100 MW
  • Small-hydro               : between 1 – 15 MW
  • Mini-hydro                 : between 100 kW – 1 MW
  • Micro-hydro              : between 5 kW – 100 kW
  • Pico-hydro                 : less than 5 kW

Hydro Power Plant has two models, they are Run Off River and Run On River. Run Off River is a system which water that is used has separated way from river flow. This model is common used on Mini and Micro Hydro. Whereas Run On River is a system which water that is used is on single track of river flow. This model is usually used on Large and Medium Hydro Power Plant.

run off river

Fig. 1 – Run Off River Model

Technically, micro hydro has three main component, they are water (energy source), turbine, and generator. Running water with a certain capacity distributed at a certain height to power house. In the power house, water will rotate the turbine and change into mechanical energy because turbine shaft will rotate. The rotated shaft is transmitted to generator using the coupling. Generator produces electricity which will enter to electric control system before distributed to the houses or other load.

Main Components Hydropower of Run Off River Model:

  1. Weir
  2. Intake Gate
  3. Connecting Tunnel
  4. Waterway / Head Race
  5. Forebay Tank / Desilting Basin
  6. Penstock
  7. Power House
  8. Tail Race
  9. Turbine
  10. Generator
  11. Transformator
  12. Load Controller
  •  Weir, Intake Gate, and Connecting Tunnel

Weir is used to collect water which will be used for power plant. From weir, water will enter to the intake gate leading to the connecting tunnel which go out into the run off river. After pass connecting tunnel, water will pass waterway.


Fig. 2 – Weir


Fig. 3 – Intake Gate

  • Waterway / Head Race

Waterway or head race usually follow contours of the hill to keep the elevation of the channeled water and keep the potential energy stable on the value.


Fig. 4 – Waterway

  • Forebay Tank / Desilting Basin

Forebay tank is used to control water output difference between penstock and head race. Moreover, its function as final separation impurities in the water such as sand and wood. The function of forebay tank is also as desilting basin (sand trap). The assignment of the desilting basin (sand trap) is to settle out the particulate matters floating in the water to the bottom of the construction. The water which is used for the turbine can therefore be separated from these solids. This function is very important because to protect other micro hydro power plant components from the impact of sand.

head tank

Fig. 5 – Forebay Tank

  •  Penstock

Penstock is water supplier from head tank which will rotate the turbine. Penstock connects a high elevation to a lower elevation to the turbine.


Fig. 6 – Penstock

  • Power House and Tail Race

Power house contains the main equipments to change potential energy become electricity, they are turbine, generator, and control panel. After water rotate turbine then water will be returned again to the river through specific tunnel which is called tail race.

power house2

Fig. 7 – Outside The Power House

power house

Fig. 8 – Inside The Power House

tail race

Fig. 9 – Tail Race

  • Turbine and Generator

Turbine and generator are used to change water potential energy which is fallen through penstock become electricity. Turbine is connected with a pulley on the generator so between water side and electricity still separated. To regulate changing electic is used AVR (Automatic Voltage Regulator) on the generator.



Fig. 10 – Turbine and Generator

turbine generator

Fig. 11 – Turbine and Generator Scheme

  • Transformator

Transformator is used as AC conversion of generator output voltage to transmission line or use voltage. The transformation may involve the loss of some power as waste heat. After from transformator, electricity go to the transmission line before go to load.

switch yard

Fig. 12 – Transformator

  • Load Controller

Electronic Load Controller is an electronic governor which the functions as a frequency and voltage regulator on a generator. There are some advantages of load control:

  1. Avoiding expensive mechanical/electrical tools.
  2. Load control tools are relatively simpler and cheaper.
  3. Load control is possible to accept very big load changes.
  4. Simple maintenance.

Load Controller

Fig. 13 – Electronic Load Controller