5 Facts about Darrieus Wind Turbines
Darrieus wind turbines are a type of vertical axis wind turbine or VAWT for short. The shape of the wind turbine is often described as an “eggbeater” design, since it incorporates the use of curved aerofoils (aerodynamic blades) that are vertically mounted on a rotating shaft. The idea for such wind turbine configuration goes back as far as 1931, when French aeronautical engineer Georges Jean Marie Darrieus first thought of the concept.
The rather unique design of Darrieus wind turbines allow them to have some of their very own quirks, which makes it quite distinct even for some of the other commonly used vertical axis wind turbine configurations. A few of the well known facts about this type of wind turbine is as follows:
- Darrieus wind turbines are capable of generating wind energy regardless of wind direction with relative efficiency. The basic principle is that the vertically erected curved aerofoils are arranged symmetrically, and the angle of incidence for each blade is zero. Since it does not need to be manually oriented towards a specific wind direction, it won’t need extra turning mechanisms like an ordinary wind turbine. This is one of the two most important advantages of the Darrieus wind turbine.
- Since this “eggbeater” wind turbine is installed vertically, the gear box and the generator can be placed very close to the ground. This means that tinkering with its inner mechanisms could be very easy and safe. You can conduct regular service repair and maintenance without the need to climb a considerable distance from the ground. This is the second of the two most important advantages of Darrieus wind turbines.
- Even if Darrieus wind turbines can be configured to increase energy generation efficiency, it is not self-starting, and is not a completely independent source of energy. The initial push that would make the blades start spinning on its own must be started by a small motor. When we equate this fact with ordinary wind turbines, it makes the Darrieus wind turbines comparatively inferior, since being able to produce energy on its own is very important in determining the actual energy efficiency of a specific energy source.
- Naturally, strong winds are supposed to be more beneficial and advantageous for a wind turbine. This is not the case for Darrieus wind turbines. The vertical blades have a strong tendency to flex and vibrate as the wind gets stronger. They are not typically recommended in areas where storms and strong gales are common, as these natural phenomena could send wind speeds that could literally break the configuration.
- Conversely though, even if Darrieus wind turbines are weak against very powerful winds, they are actually quite efficient (conceptually) when the wind speed is low. It creates a higher tip speed ratio (TSR) when wind speeds are relatively low, spinning a lot faster than the push that the wind provides. The only problem that limits this potential is the apparent weak transmission of the blade’s torque or spinning force to the gearbox and generator (compared to other wind turbines). The configuration seems to have general efficiency issues when transferring mechanical energy.
Many wind turbine design experts have dismissed the basic eggbeater design of the Darrieus wind turbine as an inefficient configuration for a sustainable wind energy system setup. Other variations of this configuration however, such as the Giromill and the Cycloturbine configurations, are a bit more promising, although they still hold negative points in practicality when paired with the standard propeller wind turbine configuration.
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