Abstract: An apparatus for extracting power from a fluid flow comprising a fluid driveable engine, a fluid directing arrangement defining a channel in the flow of a primary fluid, the channel with a flow accelerating constriction shaped. The primary fluid accelerates as it passes through the flow accelerating constriction, the arrangement being formed to impart a rotational flow component to the primary fluid entering the constriction thereby creating a radial pressure gradient in the primary fluid as it passes through the constriction. A conduit for directing flow of a driving fluid different from the primary fluid and in fluid communication with the engine and a portion of the channel having accelerated fluid flow. Flow of driving fluid through the conduit drives the engine and delivers driving fluid to the fluid directing arrangement such that it is drawn substantially along the central axis of the rotational flow.

Abstract: An apparatus for extracting power from a fluid flow comprises a fluid driveable engine, a conduit, disposed to enable fluid communication between a portion of the fluid flow, the fluid driveable engine and a transmission fluid, the fluid in the fluid flow and the transmission fluid being different fluids and the portion of the fluid flow being at a lower pressure than the transmission fluid by virtue of its flow rate, thus causing the transmission fluid to be drawn through the conduit to become entrained in the fluid flow, the fluid driveable engine being arranged such that the flow of the transmission fluid along the conduit acts to drive the fluid driveable engine.

Abstract: A device for extracting energy from underwater fluid flows, comprising at least one fluid formation directing device (10) defining a constricted channel (20) arranged to cause fluid entering it to accelerate. A conduit (30) in fluid communication with a constricted portion of the channel (20) such that fluid is caused to flow in the conduit (30) in response to fluid flow through the channel (20). The conduit (30) can be connected to a fluid drivable engine (40) which can be positioned remotely from the channel (20), the fluid flow through the conduit (30) acting to drive the fluid drivable engine (40).