Gull Wings Can Power Buildings

In the process of designing a small, highly efficient wind-powered generator that can be easily mounted on buildings and is effective at low wind speeds, Festo Corp. decided to look to nature for a solution. The Festo team turned to one of the most efficient aerodynamic shapes in nature -- the seagull's wing. The result is the DualWingGenerator.

Festo noted that as measured in wind tunnel tests, the DualWingGenerator is 45% efficient at relatively low wind speeds of 9 to 18 miles per hour. To put this into perspective, the theoretical upper limit of efficiency for a wind-powered generator is 59%, only 14 percentage points above the DualWingGenerator.

The pilot unit measures just eight feet across. Wind flowing over the aerodynamic surfaces causes the two pairs of gull-contoured wings -- one pair on each side of the unit -- to rise and fall on a central column. This vertical up and down movement is transferred to a rotating belt that turns an electric generator. A Festo controller and servo motors continually optimize the angle of each pair of wings for the highest overall efficiency based on wind speed and direction.

The Festo design team looked at a number of biological models before settling on the seagull wing. "We learned a lot during this project, especially about the active torsion of the wings, which was absolutely necessary to realize this efficient flight behavior, and we found that the seagull was a good option," Elias Knubben, head of corporate bionic projects at Festo, tells Design News. "We used this knowledge to develop the DualWingGenerator. You can find this principle [of] efficiency in this project."

High efficiency and small size give the DualWingGenerator versatility not found with large wind turbines and wind farms. In the future, rooftop units may be used as residential and commercial solar panels are, to generate building power and feed electricity to the power grid. The units may also be used to conserve energy by pumping water or compressing air at food, pharmaceutical, or chemical processing plants.

While the Festo team has developed working models using the seagull wing design, it has not yet put the concept into production. "So far we have two versions of the DualWingGenerator. One version was made for scientific research and is more or less a testing device in a wind tunnel to measure efficiency and to figure out which parameters are relevant," says Knubben. "The other version is a demonstrator that shows how it will look, and serves as a future concept to discuss the wing efficiency principle in public."

He concedes that the seagull mini wind-farm concept extends outside the company's core market of automation and control. Even so, the design team believes it has a commercially viable product. "We think that there is a high potential in the market for this concept and we are working further on to develop it until it becomes available," he says. "Up to now it is outside the traditional Festo market, so we will see if we can get some partners for distributing this concept."

Festo is working on further increases to efficiency. Instead of the rigid wing surfaces, the company is testing adaptive wings through the Fin Ray Effect, another process borrowed from nature that mimics the flexible shape-shifting of a fish's fin as it moves through water. Utilizing the Fin Ray Effect, the wing surface will change shape depending on the angle of wind flow.

The DualWingGenerator is a Festo Bionic Learning Network project. The Bionic Learning Network is an open, multi-organization program that applies designs found in nature to motivate, inspire, and stimulate innovation.

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