The present invention relates to power plants using tidal power or the water high difference between high tide and low tide and trap air for compression and generate power supply. More specifically, it relates to offshore power generating assemblies using tidal power as source of energy.

Many places in the world there is a considerable difference lift of tide, with a the sea level difference between ebb and flow of several meters. The object of the invention is to use the flow or higher tide and low tide to generate power.

The present invention thereby relates to a floating unit that will float on the sea and follow the tides up and down. The lifting and lowering of the floating unit is then used to compress air. The surface of the floating unit can be provided with various functionalities such as wind mills, a small floating town, etc. A number of generators are provided on the floating unit or in the vicinity to the floating unit, that will generate power as will be described below. The amount of power to be obtained will be defined by the amount and size of the floating unit lift and weight and the numbers of cylinders and generator units that are used.

Fig. 1 shows an assembly according to the invention.

Fig.2 shows a perspective view of a base plate suitable for use with an assembly according to the invention.

Fig.3 shows a sectional top view along A-A in fig.2.

Figs.4a-c show different views of a cylinder suitable for use with an assembly according to the invention.

Fig.5 shows a perspective view of the basic structure of a floating unit.

Fig.6 shows a sectional side view of the floating unit in fig.5.

Fig.7 shows a perspective sectional view of a technical room.

Fig.8 shows a perspective view of the upper part of the floating unit.

Fig. 1 shows an assembly according to the invention. The assembly comprises a floating unit 1 being provided with a deck 2 where one or more generators 3 is placed. A base 4 is securely attached to the sea bed below the floating unit 1. A number of cylinders 5 are connected to the floating unit 1 and the base 4. The floating unit can be connected to the sea bed to provide additional support against oceanic currents, or be self-contained if it is used in shallow water. There can be a frame or guides around with a deck and the floating unit arranged in the middle. Then the frame can be set one the sea bed and the cylinders are fitted to the frame deck.

There can be protective arrangements around the cylinders to prevent wear and damages to the cylinders and ensure that the cylinders are maintained in stable position in relation to each other. The protective arrangements can be tubular elements as shown in fig. 1 , a framework around two or more of the cylinders or stiffener elements connecting cylinders to each other.

Fig.2 shows a perspective of a partly equipped base plate 4 with flexible cylinder joints 6 suitable for use with an assembly according to the invention. A num- ber of cylinder joints 6 are arranged over the base plate 4, whereof only four are shown in the figure. The number of joints 6 will correspond to the desired number of cylinders 5. The base plate 4 can be fixed to the sea bed by poles driven through holes 7 in the base plate 4. The base plate can also be fixed by anchoring means being fastened to the base plate and anchored to the sea bed.

The embodied joints comprises an anchoring means 8 provided with a shaft aperture. A first bow shaped connecting element 9 comprising a shaft is arranged around and through the shaft aperture of the anchoring means. A cylinder spindle 10 of the cylinder 5 is provided with a bow shaped end section 11 and shaft. The shaft of the spindle is arranged through the bow shaped element 9. Thereby, the connecting element 9 can pivot in a first direction about the anchoring means 8 on the base plate 4, and the end section 11 of the cylinder spindle will pivot perpendicularly to the connecting element 9 providing full rotational freedom for the cylinder above the base plate. The same principle can be used for the connection of the cylinders to the floating unit.

Fig.4a shows a side view of a cylinder 5 with spindles 10 protruding from both end sections of the cylinder body 15. Fig.4b is a sectional view through A-A in fig.4a and fig.4b is a sectional view through B-B in fig.4b. The cylinder 5 comprises two annular fluid chambers 13 and a piston 14. The piston 14 separates the upper and lower fluid chambers 13. The cylinder body 15 is provided with upper pressure ports 12 letting out pressurized fluid when the floating unit is lifted and lower pressure ports 16 letting out pressurized fluid when the floating unit is lowered.

Figs. 5 and 6 show the basic structure of a floating unit suitable for use with a tidal power plant. The floating unit comprises buoyancy elements 17 ensuring that the floating unit has sufficient buoyancy to follow the changing surface level of the sea and extract and contract the below arranged cylinders. On the bottom surface of the floating unit there are a number of hook-ups or anchoring means 18 for connection of cylinder spindles. The floating unit is also provided with pressure tanks 19 in fluid connection with the fluid chambers of the cylinders, a technical room 20, and crane and compensators 21 for lifting and lowering of the cylinders.

Fig.7 shows a perspective sectional view showing the principle structure of a technical room 20. The room 20 is provided with at least a control unit 21 , pressure turbine 22 and generators 23. Fig.8 shows an example of basic structures that can be arranged on the upper part of the floating unit. The floating unit is provided with a helicopter landing stage or helideck 25, a crane 26, personnel unit 27 and mooring unit 28.

The crane 26 covers the whole deck. The personnel unit 27 can contain ac- commodation units, offices and entrance to other parts of power plant. One or more mooring units can be provided if needed for use in deep water.

When the floating unit is lifted due to rise of tide, the cylinders will compress fluid in the upper part of the piston in the cylinder. When the floating unit is lowered due to falling tide, the cylinders will compress fluid in the lower side of the piston. The basis of the invention is to provide two-way cylinders where fluid is compressed in the cylinders both during compression and expansion. The compressed fluid is then conducted to one or more storage tanks or the compressed power is transferred to a storable medium. The compressed fluid or medium is the channelled to the generator for transferral to electric power.

The assembly will suck and trap air on the way from low to high tide and opposite from high to low tide and compress the air in cylinders and tanks while the low tide is coming. This air will be stored in pressure chambers under the floating system, in the sea or on the sea bed.

Thereby it can be seen that this is a double working unit that utilizes the change from low tide to high tide and from high tide to low tide. This will be a continuous power generating process. The sizing of the assembly will give the limitation for how much power that is generated.

In some embodiments it will be used a large floating object to float up and down with the tide. The cylinders or the air traps that compress the air will be fix- edly connected to the sea-bed e.g. by means of a base 4. The amount of air that will be trapped and compressed will be used by an air/gas reservoir for running the power turbines continually. The system or assemble comprise several cylinders sucking and pumping/pressure up the reservoir tanks.

The cylinders and tanks are preferably removable connected to the seabed in a system that is automatic operated, so that each cylinder and tank can be separately released and lifted to the floating unit for maintenance. The floating unit can be adjusted in the sea to different heights to achieve more air in the movement from tide top and bottom. The surface area of the floating unit will set the capacity for the power generation. The floating unit can also utilize wave movement to suck and compress air.

From low tide the floating unit will be lifted up with the sea level whereby the upper chambers 13 of the cylinders are compressed providing pressurised fluid to the turbines thereby generating power during the lift. The lower chambers of the cylinders are refilled with equalised fluid. When the floating unit is lowered from high tide, the lower chambers 13 of the cylinders compressed and pressurized fluid is let out to the pressure tanks, while the upper chambers are refilled with equalised fluid. This will provide a continuous supply of compressed fluid for running the power generators.

On the top is also envisage ably to utilize the wind power with at wind mill, and also sun for power generation as there will be a large accessible surface on the floating unit 1 for power generation. The surface of the floating unit can also be used as accommodation for people.

In some embodiments it is conceivable to use an old semi rig to test lifting capacity on the rig and test the generators.

Even if the shown embodiment have arranged most technical features on the floating unit, it is equally possible to place some of these on the sea bad. The main inventive idea is to provide an arrangement on the sea bed connected to a floating unit by means of hydraulic two-way cylinders, where pressure generated in the cylinders, when the sea passes from high tide to low tide and back, is used to generate electricity.