Dual rotor wind or water turbine
A dual rotor arrangement 100 for a wind or water turbine has a planetary gearbox with two inputs and an output. One rotor 1 is connected to one of the inputs 3 and the other rotor 8 is connected to the other input 6 . A generator is connected to the high speed shaft 11 . The rotational speed of the output is determined by the relative rotational speeds of the rotors which means that the generator produces electricity of a desired frequency. The arrangement enables electricity of constant frequency to be generated under conditions where the wind or water speed is variable.
1. A dual rotor arrangement for a wind or water turbine comprising:
a planetary gearbox having a first input connected to a first rotor, a second input connected to a second rotor, and an output connected to a generator, and in which said first rotor and second rotor comprise blades having a variable pitch;
wherein said output is coaxial with an axis around which the first and second rotors rotate, said first input is connected to a ring gear of said planetary gearbox, said second input is connected to a planet carrier of said planetary gearbox, said output is connected to a sun gear of said planetary gearbox, said first rotor is upstream of said planetary gearbox and said second rotor is downstream of said planetary gearbox;
wherein, in use, a rotational speed of said output is determined by a relative rotational speed of said first and second rotors and controlled by an angular position of said blades so that said generator produces electricity of a desired frequency under conditions where a speed of said wind or water is variable.
2. The dual rotor arrangement of claim 1 , in which in which said first rotor is positioned on an upwind side of said second rotor and said first rotor has a smaller diameter than said second rotor, wherein in use said second rotor is at least partly positioned away from turbulence caused by operation of said first rotor.
3. The dual rotor arrangement of claim 1 , in which in which said first rotor is positioned on an upwind side of said second rotor and said first rotor has a smaller diameter than said second rotor, wherein in use said second rotor is at least partly positioned away from turbulence caused by operation of said first rotor.
4. The dual rotor arrangement of claim 1 , an angular position of said blades may be varied to cause said first rotor and said second rotor rotate in a same direction or in a different direction.
5. The dual rotor arrangement of claim 1 , in which said output is connected to a generator via a high speed intermediate shaft and a high speed output shaft.
6. A wind or water turbine comprising said dual rotor arrangement of claim 1 .
7. The dual rotor arrangement of claim 1 , in which said rotational speed of said output is measured and said angular position of said blades is altered to change the relative speeds of said first rotor and said second rotor rotors.
8. The dual rotor arrangement of claim 1 , in which said rotational speed of said output shaft is given by the relationship (2n2(r2+r3)+n1r1)/r3, in which n1 is a rotational speed of said first rotor, n2 is the rotational speed of said second rotor, r2 is the radius of planetary gears, r3 is the radius of said sun shaft, and r1=2r2+r3.