So you live in a wind-poor “class 1” neighborhood, but still want to get a wind turbine. If moving to a resource-rich “class 7” community isn’t in your future plans, you can still find a wind turbine that will work for you in even the lowest wind speeds.
The first thing you need to know is that wind power is proportional to the cube of wind speed, meaning that if a turbine generates 1 KW at 10 mph, that same turbine will generate 8 KW at 20 mph (double the wind speed3 = 2 x 2 x 2).
That’s the reality of wind energy. Luckily, newer wind turbines are designed to work in wind speeds as low as 0.5 mph. Yes, less than 1 mph, a wind so light you’d have a hard time getting a feather to blow through the air. Though the amount of energy your turbine will produce at these speeds is miniscule, it is free energy. Rather than have your turbine sitting idle, you might as well be putting it to use. Here are five turbines that specialize in catching low wind.
Gearless blade tip
Wind speed is greatest at the tips of the blades. WindTronics capitalized on this aspect of wind power, by designing their Gearless Blade Tip Power System, a unique design that allows the turbine to quickly react to wind speed changes, thus maximizing its energy capture. Using a gearless direct drive design, the turbine’s small magnets located at the tips of its blades capture wind where it is greatest while virtually eliminating mechanical resistance and drag by foregoing the need to turn an internal generator. Instead, power is generated when the blade tip magnets spin around its perimeter frame.
Billed as the “highest output, lowest cost per kWh installed turbine ever made (in class and size),” Windtronics’s turbine can start-up at a speed of 0.5 mph, a mere wisp of wind, and generate electricity between 2 to 45 mph. That compared to traditional gearbox turbines that require minimum startup speeds of 7.5 mph means this gearless model is capturing a lot of wind when other turbines aren’t. In addition to its extremely low start-up speed, Windtronics claims their turbine performs without the same amount of noise and vibration as a traditional wind turbine.
Compact wind acceleration technology
The Optiwind turbine was specifically engineered for use in populated areas with slow, class 2 wind speeds (approximately 12 mph). This turbine increases the amount of wind power generated by 75 percent using an innovative wind acceleration technology that funnels wind into its five blades.
This new technology offers additional benefits. The turbines don’t need to be as high as the clouds to generate electricity, the small blades are not as likely to harm birds and bats since they are only as wide as the tower, and the turbine is quiet and simple to operate.
If a flock of geese flies more efficiently than a lone goose, a sailboat with more sails moves faster than a boat with a single sail and an animal with four legs runs faster than one with two, why wouldn’t a wind turbine with multiple rotors produce more energy than one with one rotor? That is the question Selsam Innovations designers asked themselves when developing their multiple rotor system.
Though larger rotors capture more wind, they are much heavier. Selsam designers believe that since the slower rate of rotation does not make the greater wind capture worthwhile, they designed a system with multiple small, light rotors mounted on a single driveshaft. The shaft is pointed downwards and the rotors are sufficiently spaced apart so that each rotor receives fresh wind. In testing done at Tehachapi, CA and monitored by Windtesting.com, their model generated the same amount of power at half the wind speed as a typical horizontal turbine. At the same wind speed, six times as much.
Specifically intended for marine and rooftop installations, the D400’s computer-designed rotor blades that are specifically optimized for low-speed operation run a 400 Watt direct drive generator.
In testing done by yachtsmen off the UK’s south coast, an area with average wind speed of 9 knots, the D400 outperformed the other eight turbines tested. Its output was more than double the next best turbine, despite being smaller. The manufacturer also claims that this model is extremely silent and vibration-free, making it a safe bet for the rooftop.
Made specifically for low wind performance, the Wren utilizes low TSR rotor blades proven to perform in 8m/s winds to power its small direct-drive micro-turbine. Being a micro-turbine, this model provides limited power, making it an ideal choice for applications such as powering an electric fence.
The Wren’s small size makes for an attractive, low-profile design. Despite its small stature, this sturdy turbine can handle severe weather conditions, all the while running smoothly and silently.
Purchasing a wind turbine is a major decision, so look around thoroughly at all the choices.
More and more options are becoming available every day, which makes your job as a consumer harder, but the benefit is that if you do your job right you will find a system that works just right for you. So if you live in Calmsville, USA where the air is always still, don’t give up on your dream of owning a wind turbine. Just take the time to shop around and you’ll find a model that will blow you away.
image: Appie Verschoor (Creative Commons BY)