Wind turbine with low induction tips

Abstract

A wind turbine having a rotor blade geometric design which reduces blade loads in particular, blade root bending moments, tilt moments and yaw moments.

Claims

1. A wind turbine of the fast runner type comprising: a rotor having a diameter larger than 80 meters (m) wherein the ratio of the solidity at radial position 0.5 radius (R) to the solidity at radial position 0.7R is larger than 1.5.

2. The wind turbine according to claim 1 wherein the ratio of solidity at radial position 0.5R to the solidity at radial position 0.7R is larger than 1.6.

3. The wind turbine according to claim 1 wherein the ratio of solidity at radial position 0.5R to the solidity at radial position 0.7R is larger than 1.7.

4. The wind turbine according to claim 1 wherein the ratio of solidity at radial position 0.7R to the solidity at radial position 0.9R is larger than 1.65.

5. The wind turbine according to claim 1 wherein the ratio of solidity at radial position 0.7R to the solidity at radial position 0.9R is larger than 1.8.

6. The wind turbine according to claim 1 wherein the ratio of solidity at radial position 0.5R to the solidity at radial position 0.9R is larger than 2.5.

7. The wind turbine according to claim 1 wherein the ratio of solidity at radial position 0.7R to the solidity at radial position 0.9R is larger than 3.0.

8. The wind turbine according to claim 1 wherein the rotor further comprises at least one blade having vortex generators.

9. The wind turbine according to claim 8 wherein the vortex generators are located at a radial position larger than 0.5R.

10. The wind turbine of claim 8 wherein the vortex generators are located at a radial position larger than 0.7R.

11. The wind turbine according to claim 8 wherein the blade has an airfoil at a radial position larger than 0.8R having a maximum lift coefficient of more than 1.6 when tested under 2-dimensional conditions and at a Reynolds number of 1.5 million and with the at least one vortex generator present.

12. The wind turbine according to claim 1 wherein the rotor further comprising a blade with an airfoil at a radial position larger than 0.8R having a maximum lift coefficient of more than 1.4 when tested under 2-dimensional conditions and at a Reynolds number of 1.5 million and with vortex generators removed if present.

13. A wind turbine of the fast runner type comprising: a rotor having a diameter larger than 80 meters (m), and a blade with an airfoil at a radial position larger than 0.8 radius (R), the airfoil having a maximum lift coefficient of more than 1.4 when tested under 2-dimensional conditions and at a Reynolds number of 1.5 million and with vortex generators removed if present, wherein the ratio of the solidity at radial position 0.5R to the solidity at radial position 0.7R is larger than 1.5.

Description

(1) The figures below show preferred embodiments of the invention.

(2) FIG. 1 wind turbine;

(3) FIG. 2 wind turbine blade;

(4) FIG. 3 induction distribution.

(5) FIG. 1 shows a wind turbine 1 with a tower 2, a nacelle 3, a hub 4 and a blade 6 with blade root 5. The radius of the turbine is R. The distribution of the chord versus radial position is according to the invention. FIG. 2 shows the suction side of a blade 6 with blade root 5. The blade has local chords 10, 11, 12 and 13 at respectively 0.3R, 0.5R, 0.7R and 0.9R (0.1R is not made explicit in the figure). The blade has lift enhancing means in the form of vortex generators 14 which are shown on a larger scale and by smaller numbers for reasons of clarity. In the figure the chord 10 divided by the chord 11 equals sol(0.3R/0.5R) and is 1.5. FIG. 3 shows an example of the axial induction versus radial position for a rotor according to the invention at rated wind speed of 11 m/s (curve “invent a rated”) and at 8 m/s wind (curve invent a 8 m/s). It can be seen that at rated the outer part of the rotor is rather far from a=⅓, while the inner part is still close to a=⅓. The relations for a state of the art design are shown by the curves “a rated” and “a 8 m/s”. In this rated case the induction at the outer part of the rotor is much closer to a=⅓. Therefore, the state of the art rotor will have a higher power coefficient C.sub.p but experience higher loads. The rotor according to the invention can be made larger so that it captures even more energy at less loads. The precise induction values at the y-axis are not relevant and can be higher or lower. Relevant are the respective trends in the curves, which illustrate the principles behind the invention.

(6) It will be obvious for the expert in the art that the figure and the description are just examples of the invention and that many variations are possible which are covered by the enclosed claims.