The turbines applied by Water2Energy are high efficient versions of the so called Darrieus or Vertical Axis Water Turbines, VAWT. These turbines are common in wind energy and can be used for extracting energy from free flowing water too. Compared to wind and air, the density ρ of the medium water is 850 times higher. The density is one of the governing parameters for energy available in a free flowing medium:
Pt = Cp 1⁄2 ρ At V∞^3
Cp = overall hydraulic efficiency
ρ = density of water, say 1000 [ kg/m3 ]
At = cross-sectional area of the turbine rotor [ m2 ]
V∞ = undisturbed free stream velocity [ m/s ]
Pt = turbine shaft power [ Watt ]
Altough the wind velocities are of course normally higher than those of free flowing waters, the water flows are far more predictable and constant than wind. So the hydro power supply often outperforms wind in this respect, as well as economically.
Pitch control increase Cp-values up to 0,45 !