01/20/2020
THE FUTURE OF SMALL-SCALE WIND
by Carissa Kucera
I have never been a big fan of wind power: small turbines for home use are expensive per watt in comparison to solar panels, require a minimum 30 foot tower, have restrictions on placement to avoid turbulence, are susceptible to damage in high winds, and have too many moving parts that are prone to wear out. Many of them are noisy, and they rarely produce even 50% of the energy they are advertised as making. In spite of all this, wind turbines have an appeal to many folks, who find in these machines a special fascination and beauty. Every now and then I dream of finding a high-quality small wind turbine, so I browse the internet looking for the newest and best of the home turbines being developed. The field of wind power seems to be constantly changing with a few promising designs emerging, but for now, nothing very substantially new or different is in production for the home user.
The currently available designs are the HAWD (horizontal axis wind turbine) and the VAWD (Vertical Axis Wind Turbine). In a horizontal axis design, the blades spin in a vertical circle, as in the traditional windmill. Many newer products in the market use a vertical axis, as the one pictured below. However this design in a size fit for home use has not proven to be more efficient than the traditional design. From an article in Mother Earth News: “As a design, [the VAWD] doesn't get a lot of respect in the engineering community, because it's an inefficient device. Wind devices are all pretty inefficient (a 100 percent efficient wind machine would capture 100 percent of the energy in a breeze, leaving dead-calm air downwind of it, which is impossible). The maximum efficiency theoretically possible for wind devices is around 58 percent. Most devices are in the 20 percent range. The Savonius design ( VAWD) is around 15 percent, and can't be improved much higher than that no matter what materials are used or how they are configured into a design.”
Both designs rely on the size of the “swept area” of the blades: the larger the swept area, the better the performance in kilowatt-hours of energy produced. This means that in order to have a turbine that makes enough energy to pay for itself, the swept area would need to cover a diameter of at least 5 feet, which is larger than is practical to mount in home energy applications.
Recently, the problem of poor efficiency of traditional turbine designs is being addressed by a few forward-thinking inventors. A Dutch company called The Archimedes has developed a small, highly efficient, and silent rooftop wind energy generator called the Liam1, which it claims could generate half the power a typical house would need, and which they say would be ideal for combining with solar rooftop PV panels. The company states that the Liam F1 turbine could generate 1,500 kWh of energy at wind speeds as little as 2 mph. The Liam's blades are shaped like a Nautilus shell. The design allows it to point into the wind to capture the most amount of energy, while also producing very little sound. The power output is 80 percent of the theoretical maximum energy that could be harnessed from the wind.
Another new design is the “bladeless’ wind turbine which is claimed to be twice as efficient as the traditional designs. Saphon, out of Tunisia, is interested in finding partners to mass-produce and market their unique wind energy device, based on their own Zero Blade technology. "The Zero-Blade Technology is largely inspired from the sailboat and is likely to increase the efficiency of the current wind power conversion devices. The blades are replaced by a sail shaped body while both hub and gearbox are removed."
An exiciting development in wind power is the Windcell. It may be the device that changes the entire discussion on wind power because it is a completely different design that captures the smallest breeze to create energy in small spaces and urban settings. The Windcell can be placed in areas that were previously not practical for wind power, such as porch railings or privacy walls.
I really hope to someday see a home wind turbine that incorporates the best of all possible worlds: efficient energy production, able to produce power at any wind speed, durable with few moving parts, quiet, and affordable. The wind industry is changing all the time, so next year or the next 20 years may bring even better small wind designs. If you have a penchant for mechanics and an adventurous spirit, you might be able to build a simple wind machine that will cost you very little and give a boost to your solar power system. Until turbines get better, this seems to be the best use for small wind.
