When it comes to green energy alternatives wind turbines are certainly up there with solar energy and hydropower generators as being one of the most attractive green energy options. In the paragraphs to follow I’m going to be sharing with you some Darrieus wind turbine facts you may not be aware of, including important distinctions between the popular and iconic propeller driven wind turbines and the somewhat mysterious Darrieus types. These vertical axis wind turbines (VAWT’s for short) can very easily be seen as a superior design, let’s take a look at exactly why that is.
Low Wind Efficiency
When considering which type of wind turbine to go for one obvious factor stands out and that’s efficiency. After all the whole point here is to generate as much electricity as possible and remarkably this is where the Darrieus type of wind turbine really shines. Typical propeller designs are optimised to function best when the wind direction is headed straight into the front of the propeller which means when the wind changes (as it does on a moment by moment basis) the propeller stops spinning or at best severely reduces its rotation speed until the wind once again hits that sweet spot, which often must be achieved by rotating the propeller to face into the wind.
The Darrieus wind turbine however has a number of unique characteristics which enhance its performance, even under low wind conditions. The first being the unique shape of the aerofoil blades, curved out and shaped just like that of an aeroplanes wing, which when wind is applied produces high pressure on the inner side of the blade and low pressure on the outer side which then propels the blades and shaft around in a circular motion. The second and probably most distinctive attribute of this type of wind turbine is that while many have only two blades they typically can have three to four blades also, which means regardless of which direction the wind is blowing the shaft will continue to turn so long as there is wind. Even in low wind conditions the Darrieus wind turbines will keep spinning, only stopping when the wind comes to a complete stop.
In a world where we’re trying to become more energy independent, sources of renewable green energy must also be practical… and practicality starts at home. When talking about wind turbines Darrieus versions are well known for being super quiet, which is crucial considering they are typically active day and night and I’m sure the last thing you want are complaining neighbours. So it’s important. They are well balanced and because they vibrate less they simply don’t produce as much noise.
A common problem often associated with wind turbines is that of birds flying into them and meeting their maker. This is obviously something to avoid and in this case, it’s something that can be avoid with great success. Many owners of Darrieus wind turbines report of having no such issues with birds flying into them, as opposed to propeller type wind turbines which have an unfortunate track record of causing harm to birds. This is likely due to the fact that because of the way the Darrieus turbines are designed, they appear like more of a solid object to birds and they tend to keep away from them.
Take Your Pick
There are a number of different designs which can be classed as Darrieus wind turbines. They share many similarities, however they also share key differences each with their own advantages. Giromills or H-bars as they are otherwise known are a “less efficient” design in normal conditions compared to the Darrieus designs, however often work well and in fact better in more turbulent wind conditions. They’re also more affordable.
Cycloturbines are an interesting creation as each blade is mounted so that it can rotate around its own vertical axis. This allows for the blades to be pitched for the optimum angle of attack which results in improved performance in a variety of wind conditions. The ability to adapt makes this design easily the most effective and most powerful Darrieus wind turbines available because it can produce more consistent torque. It’s also able to self start much easier because of the ability to pitch the blades. The only real downside is the complexity and added weight and cost of the pitch mechanism.
And finally the helical design is well known for it’s ability to spread the torque evenly over the entire rotation, which prevents what could otherwise be destructive pulsations, especially in turbulent conditions. These are often smaller units making them a great choice in residential areas.
All in all, nothing is perfect. Green energy has always been a challenging field, especially when competing with the dirty forms of energy we as a society have become so dependent upon. This of course is not a comprehensive list of pro’s and con’s, however it was never mean’t to be. It’s designed to get you thinking and considering Darrieus wind turbines as a viable green energy alternative.
The great thing about green energy technologies such as these (and a huge advantage over polluting alternatives) is that once you’ve set them up, they just run and run and run. You always need more coal, more oil, more “stuff” to break down, burn, etc.
But with wind power, it-just-works!