The introduction of the Freestream Darrieus Water Turbine to the commercial market is a major step in small waterpower technology.
Alternative Hydro Solutions Ltd. believes that the Darrieus turbine is the best choice for small and medium river sites. The advantages that Darrieus turbines have over propeller type turbines include:
i) their ability to have a greater diameter than depth which enables more area to be swept in a shallow stream and therefore
more power production per turbine,
ii) the vertical shaft provides easy maintenance as the electrical components and bearings are above water, and
iii) increased efficiency over propeller turbines not specifically designed as water current turbines.
At lower rotational speeds relative to the water speed the turbine blades reach their stall point and therefore the turbines overspeed is naturally limited, at this point power production also starts to taper off. The water flow speed that is generally accepted as the minimum for power production is 0.8 m/s ( 2.6 ft/s ). As will be shown in the Applications