CPC F03D 3/02 (2013.01) [F03D 3/005 (2013.01); F03D 3/06 (2013.01); F03D 7/06 (2013.01); F03D 9/25 (2016.05); H02K 7/183 (2013.01); F05B 2220/706 (2013.01); F05B 2240/37 (2020.08); F05B 2240/374 (2020.08); F05B 2260/70 (2013.01); F05B 2260/85 (2013.01)] | 20 Claims |
1. A vertical axis turbine comprising:
a first rotor and at least one second rotor,
the first rotor being configured to rotate around a first rotation axis, wherein the first rotation axis is vertical or more vertical than horizontal in use;
the at least one second rotor being provided on, comprised in or coupled to the first rotor such that the first rotor is operable to move the second rotor upon a rotation of the first rotor,
wherein the at least one second rotor is operable to drive a power take off system,
a tip speed ratio in use at a rated wind speed of the at least one second rotor is in a range from 3 to 4,
the first rotor and the at least one second rotor in use at a wind speed below the rated wind speed have a combined tip speed ratio in a range from 14 to 16; and
the at least one second rotor in use at the wind speed below the rated wind speed has an aerodynamic thrust coefficient (CT) to aerodynamic power coefficient (CP) ratio of more than 0.75.
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