The Freestream Darrieus Water Turbine
Designed and manufactured by Alternative Hydro Solutions Ltd., the Darrieus Turbine was first conceived by Mr GJM Darrieus in the early 1920’s. This “cross flow axis of rotation design” turbine has had a few variations, and is used today in large wind power turbines.
AHS believes this design is the best choice for small and medium river sites. To achieve adequate power production, the water’s current needs to have a minimum of 2.6 feet per second flow rate.
The Darrieus Turbine is available in 4 sizes, each a proper fit for the width, depth and flow rate of your river. The sizes in diameter are: 1.25 Meter, 1.5M, 2.5M, and 3M in varying shaft depths. Machining of the rotating assembly is from 60635T Aluminum alloy to endure a long corrosion free underwater life.
The shaft, bearings and fasteners are all stainless steel. A permanent magnet DC generator or a brushless alternator are available as power heads, which accept power from a flexible coupling and gearbox combo to increase the RPMs. An output graph of varying turbine sizes and water flows seen below:
1. 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.
2. The vertical shaft provides easy maintenance as the electrical components and bearings are above water.
3. increased efficiency over propeller turbines not specifically designed as water current turbines.
Considerations for installations:
1. The prevention of river borne debris. A ‘trash rack’ or similar screening system should be constructed to protect the rotating assembly. Planning should also be done for quick removal in storm runoffs or spring season.
2. Mounting of the vertical shaft frame. A partial or complete support beam needs to span horizontally over the swift running water portion of your stream or river. Existing infrastructure is ideal; or a raft, vertically driven stanchions, etc.
3. Sizing the correct turbine for your site. Maximum power potential should be observed, and AHS will work with you to achieve the best suited model for your needs. Learning your annual flow rates, as well as your local governing bodies’ waterway restrictions are primary goals.
4. Wiring. Follow local codes if possible, using copper cable in the biggest AWG you can afford. Whether you have a short run to your batteries or not, the bigger the better to minimize power losses.
Alternative Hydro Solutions sells the turbines themselves, or the complete set up and installation if desired. They are located in Toronto, Ontario Canada. See their website at www.althydrosolutions.com