Optimization of wind blade tip designs is the focus of the InnoTip research project launched by LM Wind Power’s aerodynamics team and the Energy Research Center of the Netherlands (ECN). Advanced tip designs can reduce noise and the leveled cost of energy while increasing power output.

New designs were tested by extending blades with a temporary add-on tip extension, demonstrating power increases up to 6% during initial trials. The engineers sought to increase the Annual Energy Production (AEP) of an offshore wind farm by 2%.

“Considering that one offshore wind turbine with 88.4 meter blades can power 10,000 households, even a small increase in AEP has a significant impact on reducing the cost of energy,” said Jordy van Kalken, InnoTip Project Manager at LM Wind Power. “The cost of producing blades with different tips is relatively small compared to the improved power output, so the InnoTip project could lead to a cost of energy-reduction of up to 2 percent, making the use of wind energy more competitive.”

Three different geometries were developed for testing: a shark fin tip, a winglet tip and turbulators. The bending of the blade tip (winglet) effectively increases the length of the blade but in an altered direction, imparting some beneficial effects on the complex aerodynamic phenomena in the tip area of the blade. The turbulator causes a faster mixture of the wake, which is beneficial for turbines further downstream in the wind farm.

Instead of building costly new blades, the team replaced only the tips on blades already in operation at ECN’s test site in the Dutch Wieringermeer. After the experiments, all the tips were successfully removed without damaging the blades so that the turbines could continue to operate safely.

The evaluation was conducted with a side-by-side configuration where all the tips were on the turbines and measured at the same time for the same wind climate.

From left to right: the winglet, shark fin and turbulators. (Photo courtesy of Skysurvey BV)