Abstract: An underwater trenching apparatus comprising a soil cutting arrangement having a forwardly disposed cutting portion and a rearwardly disposed non-cutting portion, a soil removal device configured to remove soil from a location forward of the soil cutting arrangement and barrier device located and configured substantially to prevent passage of soil to the non-cutting portion of the soil cutting arrangement. The soil cutting arrangement is typically a rockwheel or chain cutter. The soil removal device is typically a dredge pump or eductor.

Abstract: The invention relates to a sub-sea trenching machine (16) including two cutter units (26a, 26b). The cutter units are preferably chain cutter units. The cutter units are mounted to be moveable from a use position in which the cutter units are juxtaposed or spaced a limited distance apart to a stowed condition in which the cutter units are sufficiently spaced apart to allow mounting of an elongate workpiece (18) such as a pipe or cable onto the trenching machine.

Abstract: An undersea power generation apparatus (1) includes two turbines (3) mounted side by side at either side of a support strut of hydrofoil-shaped cross section, each turbine (3) having a set of turbine blades which counter rotate so as to cancel out the respective torque produced by each turbine. The apparatus (1) is pivotally interconnected at point (9) to a pair of mooring cables (7), which are releasably moored to the seabed (6). The turbines (3) are positively buoyant such that in zero current they point vertically upwards as denoted by (8). When the current flows in the direction shown by arrow A, the drag forces on turbines (3) and support strut cause the apparatus (1) to pivot about point (9) and pitch over into condition denoted by (10) and shown in broken lines.

Abstract: A tidally driven electricity generator (1) has a series of turbines (2), each of which is mounted under water in an offshore location. Each turbine (2) has blades (3) which are rotated by tidal flow of water, to power a respective generator (4), which outputs AC electrical power via a respective transformer (5) to a cable (6) and appropriate switchgear (7). The cable (6) is connected to a further transformer (8) located onshore, and the transformer (8) is connected to two AC inputs of a drive (9) containing an AC/DC converter, one input (10) of which is connected via a cable to a control feedback device (11). The control feedback device (11) may be a flow meter which determines the velocity of the tidal flow, or may contain look-up tables containing information relating to the velocity of tidal flow at any particular time. The drive (9) outputs DC electrical signals along cabling (13) to DC/AC converter (14), which outputs AC electrical powervia transformer (15) to a fixed frequency local supply grid (16).