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Energy, electricity and mechanics

Power of a water head (micro-hydro)

Hydraulic and electrical power of a water head based on flow rate and height.

L/s

Flow rate available continuously.

m

Elevation difference between the water intake and the turbine.

%

Head loss from friction in the penstock. Typical: 5-15 %.

%

Combined turbine and generator. Typical: 60-80 %.

Result

Gross hydraulic power
— W
Electrical power
— W
Energy in one day
— kWh

How it is calculated

Gross hydraulic power: P = ρ × g × Q × H, with the density of water ρ = 1000 kg/m³, g = 9.81 m/s², flow rate Q in m³/s (1 L/s = 0.001 m³/s) and gross head H in metres.

Net head after pipe losses: H_net = H × (1 − losses). Electrical power: P_e = ρ × g × Q × H_net × efficiency.

Energy in one day if the flow rate is constant: kWh/day = P_e × 24 ÷ 1000.

Keep in mind

  • The actual flow rate varies with the season: use the guaranteed minimum ecological flow, not a one-off flood peak.
  • Any water intake for energy use may need authorisation from the river basin authority and must respect an ecological flow downstream.
  • The turbine's electrical installation needs the same protection as any generator: residual-current device, circuit breaker and earthing.

See also

More tools in “Energy, electricity and mechanics”