Darrieus turbines can be used in wind and hydropower generators. The operation of this type of turbine is the post’s subject.
How it works?
Darrieus turbine rotates around a vertical axis. Has blades in airfoil shape, the airfoil’s motion creates an air flow (red arrow). The wind direction (white arrow) and air flow due to airfoil speed (red arrow) create a resulting flow which forms an angle (black arrow) with air flow. Resulting flow creates a torque in the blade (green arrow) due to difference of pressure in the blade’s opposite sides. This torque and the airfoil’s speed are used to produce electric energy.
Advantages and disadvantages
Advantages of this type of turbine are:
- Gear box, generator and controller are in the base, facilitating maintenance.
- Unlike wind turbines with horizontal axis, don’t have to be pointed to wind direction, simplifying the project.
- Can be installed in urban area, for be quieter, and even in top of buildings.
- Blades move slower, reducing environmental impact of bird collision.
- Can be installed in mountainous regions.
The disadvantages are:
- Needs an induction motor to start, but this motor can be used as generator.
- The turbine operates close to ground, where winds are weaker.
- Has lower efficiency than horizontal axis turbine.
- Stress in blades caused by centrifugal force.
- Vibration caused by air flow close to the ground.
- Requires cables for support.
Darrieus turbine H-type
This is another type of Darrieus turbine. Also called Giromill, has strait blades instead of curved ones.
This turbine is cheaper and easier to build. Can work with turbulent winds. However is less efficient than curved Darrieus. The Cycloturbine is a variation of Giromill. Blades can be oriented in a way that always have an angle with the wind to create torque. It is capable to self-start.
This video shows another blade guiding mechanism. Click here if you can’t see the video.
Darrieus turbines in hydroelectricity
This portable hydropower plant can be installed in rivers to generate electric energy. Has 2 Darrieus turbines made of aluminum.
According to the company, has low maintenance cost, can generate between 2 and 6 KWh/day (kilowatts-hour per day). The minimum stream speed must be 1,2 m/s and depth can be minimum of 2 feet (60.96 cm). This is the power plant’s video.