NOVELTY - Device comprises tidal energy dam (2) blocking sea water, U-shaped louver-type water inlet valve dam (3), U-shaped louver-type water drain valve dam, piston vessel (7), movable piston (6), pool cylinder sleeve (12), pool cylinder sleeve water inlet valve (11), drain passage (13), high pressure water inlet valve (14), high pressure water inlet passage (15) and high pressure water conservation reservoir (18).    USE - The device is useful for generating electricity from tidal energy and desalinating sea water using electricity.    ADVANTAGE - The device is safe as it converts tidal energy into electricity for desalinating seawater through buoyancy, gravity, pressure and hydraulic power, reliable and cost-effective, has simple structure, and provides long term benefits and sustainable development of renewable energy source.    DETAILED DESCRIPTION - Device comprises tidal energy dam (2) blocking sea water, U-shaped louver-type water inlet valve dam (3), U-shaped louver-type water drain valve dam (4), piston vessel (7), movable piston (6), pool cylinder sleeve (12), pool cylinder sleeve water inlet valve (11), drain passage (13), high pressure water inlet valve (14), high pressure water inlet passage (15) and high pressure water conservation reservoir (18). The tidal energy sea dam is fixedly connected with the U-shaped louver-type water inlet valve dam. The U-shaped louver-type water inlet valve dam and the U-shaped louver-type water drain valve dam are connected to form a closed buoyancy pool (5). The piston vessel is arranged in the center of the closed buoyancy pool. The bottom of the closed buoyancy pool is fixedly connected with the pool cylinder sleeve inside having pool cylinder sleeve water inlet valve. The drain passage and the pool cylinder sleeve are fixedly connected with the high-pressure water conservation reservoir with high-pressure water inlet valve and high-pressure water inlet passage.    DESCRIPTION OF DRAWING(S) - The drawing shows schematic view of device.    Tidal energy sea dam (2)    U-shaped louver-type water inlet valve dam (3)    Closed buoyancy pool (5)    Movable piston (6)    Piston vessel (7)    Pool cylinder sleeve water inlet valve (11)    Pool cylinder sleeve (12)    Drain passage (13)    High pressure water inlet valve (14)    High pressure water inlet passage (15)    High pressure water conservation reservoir (18)