A turbine adapted to be constrained within a flow of fluid includes a stator adapted to be constrained within a flow of fluid, and a rotor defining an aperture and having rotor blades protruding from a peripheral region of the rotor into the aperture. The rotor is adapted to be rotatably mounted to the stator such that movement of fluid through the aperture causes rotation of the rotor relative to the stator. Electricity is generated as a result of rotation of the rotor relative to the stator.