Wind turbine with slender blade
AssigneeCortenergy BV
InventorGustave Paul Corten
Life of this patent
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Abstract
Wind turbine with a rotor blade relatively insensitive to turbulence because it is more slender than prior blades and is nevertheless able to generate sufficient lift by virtue of the fact that flow enhancing elements such as vortex generators combat flow separation. The slenderness is defined by the chord numbers C and D of which C is defined as C=Ncrclrλ2/R2, in which N is the number of blades, cr is the local chord, cl the lift coefficient, r the radial position, λ the tip speed ratio and R the rotor radius. Subsequently, the chord should be less than what follows from the equation C=M in which M=−1.19+9.74Cp−21.01Cp2+17.50Cp3 and Cp is the power coefficient. This wind turbine is subject to about 2-12% less operational loads and to about 5-40% reduced survival wind speed loads compared to classical designs.
Claims26
A wind turbine comprising a blade with an aerodynamic profile, said profile having in the range of 0.2R to 0.95R a 10 minutes averaged lift coefficient cl larger than 1.1, wherein within a range from 0.4R to 0.95R a vortex generator is disposed on said blade.
A wind turbine comprising a blade with an aerodynamic profile, said profile having in the range of 0.2R to 0.95R a 10 minutes averaged lift coefficient cl larger than 1.1, wherein in the case that the power coefficient ⅓<Cp< 16/27 that M=−1.19+9.74Cp−21.01Cp2+17.50Cp3 and that in said case in the radial range between 0.5R and 0.9R for a horizontal axis turbine and between 0.8R and R for a vertical axis turbine, the local chord is smaller than which follows from the equation C=M and or the average chord in said ranges is smaller than which follows from the equation C=M assuming that cl=1.1.
A wind turbine comprising a blade with an aerodynamic profile, said profile having in the range of 0.2R to 0.95R and in particular of 0.5R to 0.95R a 10 minutes averaged lift coefficient cl larger than 1.1, wherein said blade in the direction from a tip towards a root at a radial position between 0.7R and 0.2R splits in an upper blade and a lower blade with in between a free space and that both the upper blade and the lower blade contribute to the aerodynamic lift and in particular that at a certain radial position the distance between the lower and the upper blade is larger than 5% R and more in particular is larger than 10% R.
A wind turbine comprising a blade with an aerodynamic profile, said profile having in the range of 0.2R to 0.95R and in particular of 0.5R to 0.95R a 10 minutes averaged lift coefficient cl larger than 1.1, wherein said blade comprises profiles of at least 25% thickness which are used at radial positions larger than 0.55R.
A wind turbine comprising a blade with an aerodynamic profile, said profile having in the range of 0.2R to 0.95R a 10 minutes averaged lift coefficient cl larger than 1.1, wherein said blade comprises vortex generators located at the pressure side of a profile which preferably is thicker than 25% c, wherein said vortex generators are located at a chord position larger than 30% c.
A method of replacing a wind turbine blade, comprising removing a first blade of an existing turbine, and replacing a replacement blade in the turbine, wherein said replacement blade includes an aerodynamic profile, said profile having in the range of 0.2R to 0.95R and in particular of 0.5R to 0.95R a 10 minutes averaged lift coefficient cl larger than 1.1, particularly larger than 1.2 and more particularly larger than 1.4 and more particularly preferably about 1.6, and particularly that said replacement blade in the range of 0.7R to 0.95R comprises a local chord cr which is at least 10% and more particularly at least 20% smaller than the local chord cr of said first blade.
Dependencies are inferred from the claim text.