Patent ID: 8690541

Claim:
A turbine comprising: a rotor defining a main central rotational axis about which the rotor is rotatable, the rotor comprising: at least one elongated ribbon type blade extending between a first end and a second end and being of transverse cross-section along substantially its entire length of one of an airfoil and a hydrofoil cross-section, the first end of the at least one blade being located at a first location adjacent the main central rotational axis, and the second end of the at least one blade being located at a second location adjacent the main central rotational axis, the second location being axially spaced apart from the first location, the at least one blade defining a first spiral and a second spiral, the first spiral defining a first spiral axis, and the second spiral defining a second spiral axis, the first spiral extending from the first end of the blade and the second spiral extending from the second end of the blade to meet the first spiral intermediate the first and second ends of the blade with the first and second spiral axes substantially coinciding with the main central rotational axis, the first and second spirals of the at least one blade being of opposite hand when viewed axially in opposite directions from the respective first and second ends of the blade.