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Biomimic Wind Turbine: What's All the Flap About?
Tom Lombardo posted on February 12, 2017 |
Machines imitating nature: this biomimic wind turbine flaps like a hummingbird.

The science of biomimicry can be traced back to the time of Leonardo da Vinci, whose early flying machine designs were inspired by his observations of birds flapping their wings. Leo's aircraft never got off the ground, but five hundred years later, a team of engineers at Tyer Wind decided that hummingbirds could provide insights into a new wind turbine design. Let's see what all the flap is about.

# A Wind Turbine with Wings

Designers at Tyer Wind analyzed the wing movements of hovering hummingbirds and found that their wings followed a three-dimensional figure-8 pattern, with the wings reaching angles of +/- 40from the horizontal. That formed the basis for this new turbine design:

# Dimensions

The avian impersonator is made of carbon fiber composite material. Each wing is 1.6 meters long with an 80o range of motion, giving the turbine a total swept area of 3.6 square meters. Its nacelle - about 0.6 cubic meters in volume - houses all the mechanics, including a small permanent magnet generator.

Check out the video to see the turbine in action, and then I'll crank a few numbers and discuss some of the company's claims.

# Wind Power Calculations

Tyer hasn't yet released a wind curve - they're waiting for the results of field testing. Their data sheet indicates that the turbine's rated output is 1 kW at a wind speed of 10 m/s (22.3 mph). At that velocity, the wind carries just under 5 kW of power, so this turbine is roughly 20% efficient.

Keep in mind that the rated outputs of small wind turbines are specified for wind velocities that you'll almost never see in places where they're likely to be located. If your wind speed were a steady 10 m/s, all of your trees would be bent over at 45o angles.

With that in mind, let's estimate this turbine's output at a more realistic wind velocity: 5 m/s (11.2 mph) - a moderate breeze. Since wind power varies with the cube of wind speed, cutting the velocity in half results in an eightfold decrease in the available wind power, dropping the wind input to only 616 Watts. With 20% efficiency, this turbine would generate a paltry 123 Watts. It's probably even lower than that, since turbines are less efficient at slower velocities. But in the absence of a power curve, I'm giving them the benefit of the doubt and assuming 20% efficiency across the board. (For comparison purposes, I checked into a popular horizontal axis wind turbine with a 1 kW rating; its power output is similar at 5 m/s wind speeds.)

# Claims

Tyer's website has numerous claims about the technology; here are just a few, along with my thoughts:

It generates work during both downstroke and upstroke.

True, it generates power during both the downstroke and the upstroke, but a rotating blade turbine generates power during the entire rotation, so I don't see the advantage of the hummingbird design.

Tyer converter generates limited vortex (as compared to that created by turbines) which would be tranquilized backwards quite quickly allowing a higher density of installed machines (in a wind farm).

This claim is a bit more intriguing. Essentially they're suggesting that these turbines could be placed closer to each other, allowing more turbines in a given area. So what's the advantage of several small, low-power turbines as opposed to one large, high-power one? Funny you should ask - a few years ago I addressed that in another article about biomimicry and wind power. Large utility-scale turbines are very expensive to produce and they require enormous manufacturing facilities. Smaller turbines can be produced in more modest facilities; mass production using standard techniques will lead to lower overall costs.

The machine has a great landscape integration potential and limited visual impact. It is also bird friendly and could be adapted to any environment (rural or urban).

Aesthetics are subjective and I'm an engineer, not an artist, so I'll let others decide whether this is more attractive than a traditional three-blade turbine. I don't see how it's more bird friendly, other than the fact that it covers less total area than a spinning rotor with blades.

As far as urban settings are concerned, cities are terrible places for wind turbines. Urban winds are turbulent, causing additional stress on the turbines, and buildings obstruct the high-velocity winds that contain large quantities of power. A turbine in an urban setting might look cool, but it only provides short bursts, not sustained power.

In the summer, my wife and I enjoy sitting on the deck and watching the hummingbirds come to our feeder. They're amazing creatures, gracefully and efficiently turning air and wing movement into lift. Whether they'd be good at converting wind into electricity remains to be seen, but it looks like we'll have some evidence in the near future.

Images and video courtesy of Tyer Wind

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