Unexpectedly Intriguing!
March 10, 2017

The flights of birds have been inspiring human invention for thousands of years. And for thousands of years, people haven't had much success in mimicking the flapping motion of a bird's wings to produce the kind of thrust needed to power themselves into the air outside of very small drones.

But what if instead of trying to generate both the upward and forward thrust to fly, somebody tried to simply model the motion of a bird's flapping wings in flight to generate electrical power by more efficiently capturing energy from the wind?

Somebody in this case is a team of Tunisian engineers employed by Tyer Wind, who have developed a prototype wind turbine whose blades model the flapping motion of hummingbird's wings to generate electricity. Here's their promotional video that introduces the technology, which is made all the more impressive by its soundtrack.

Before anybody gets too excited, we should recognize that the only way that we would ever see a forest of pylons with flapping, power-generating wings mounted on top of them is if they can successfully generate more electricity both more efficiently and more economically than a more traditional wind turbine can produce.

Engineering's Tom Lombardo did some math to find out how much power Tyer Wind's prototype flapping wind turbine might produce:

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 45° 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.)

So the concept has some potential, but isn't the kind of clear home run that wind power enthusiasts might have hoped. It will be interesting to see the data from the prototype's testing.

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