Wind turbines with flexible blades found to be 35% more efficient. They also work over a wider range of wind conditions than standard turbines new study finds

wind turbine
Credit: Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science (2017)

In their tests, some of the turbines ran with the standard hard blades, some ran with very flexible blades, and some ran with blades that were approximately in the middle—not hard, but not as floppy as the other blades. They then tested each of the turbines for efficiency.

 

Efficiency maps CP as a function of the headwind velocity U and the resistive torque C for a pitch angle θ0=30°, for, (a) the case RB (reference), (b) F1 and (c) F2. The efficiency CP is expressed as a percentage of the maximum efficiency reached at θ0=30° for the rigid case (CmaxP=0.0936). Resolutions for both U and C are respectively 1 m s−1 and 8 mN m. As can be observed, the case F1 shows an extension of the working domain of the turbine and of its high-efficiency range (above 50% of CmaxP). Case F2, though, shows a strong decrease of the performance compared with its rigid counterpart.
Efficiency maps CP as a function of the headwind velocity U and the resistive torque C for a pitch angle θ0=30°, for, (a) the case RB (reference), (b) F1 and (c) F2. The efficiency CP is expressed as a percentage of the maximum efficiency reached at θ0=30° for the rigid case (CmaxP=0.0936). Resolutions for both U and C are respectively 1 m s−1 and 8 mN m. As can be observed, the case F1 shows an extension of the working domain of the turbine and of its high-efficiency range (above 50% of CmaxP). Case F2, though, shows a strong decrease of the performance compared with its rigid counterpart.

The researchers report that the hard-bladed turbines performed as expected, but the floppy blades did not work well at all—they were less efficient than the hard blades.
But the middle option proved to be approximately 35 percent more efficient than the standard hard-blade turbine. They also found that the turbines worked over a wider range of wind conditions than standard turbines—they would turn under lower wind conditions and were not as susceptible to wear and tear under high wind conditions.

The idea for flexible blades came to the researchers after noting that most insects have flexible wings, which prior research has suggested provides creatures such as the dragonfly more power without expending more energy, by contrast with inflexible wings.
The idea for flexible blades came to the researchers after noting that most insects have flexible wings, which prior research has suggested provides creatures such as the dragonfly more power without expending more energy, by contrast with inflexible wings.

The researchers suggest the use of flexible blades on wind turbines offers the advantage of increased versatility and efficiency. More research is required to discover optimal flexibility and to determine if such blades are commercially viable.

Source: http://rspa.royalsocietypublishing.org/content/473/2198/20160726

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