Power generator for generating power from water flow

A power generator for generating power from a water flow flowing in a flow direction, the generator comprising:

• a single blade with first and second faces on opposite sides of the blade;
• a base to which the blade is rotatably mounted;
• the blade being mounted so as to be reciprocally rotatable through a limited arc about a sweep axis, the sweep axis extending in the flow direction;
• the blade further being mounted to be rotatable through a limited arc about a pitch axis, the pitch axis being transverse to the sweep axis and extending along a mid-portion of the blade such the blade is overbalanced respect to the flow direction, and so as to be selectively retainable in a first rotary position in which its first face faces the flow, and a second rotary position in which its second face faces the flow;
• wherein when the blade is in the first rotary position, in use, the flow can push the blade in a first direction about the sweep axis, when the blade reaches the limit of its rotation in the first direction, it is configured to tack about the pitch axis so that the blade is in the second rotary position in which the flow can push the blade back in a second opposite direction about the sweep axis, and when the blade reaches the limit of its rotation in the second direction about the sweep axis, it is configured to tack about the pitch axis so that the blade is back in the first rotary position;
• the generator further comprising a power output coupled to receive power from the blade reciprocating about the sweep axis;
• wherein a respective passive tacking stop is provided to arrest the momentum of the leading edge of the blade and cause the blade to tack when the blade reaches the limit of its rotation in the respective first and second directions.