From the WhalePower company's website:

"The 16 degree stall angle found in the first wind tunnel experiment has been enhanced to produce airfoils that don't stall until they reach an astounding 31 degrees - far above anything previously known.
Unlike virtually every other airfoil which can stall violently and even damage the machines they‘re employed on, tubercle airfoils always stall gradually. That changes the rules for turbines -- forever. "