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Author: Arvid Nesheim

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Description of a practical method for conversion of

ocean wave energy into electrical energy


The conversion method is in the draft stage. The drawings show the principal working method.

The device is a spring mass oscillating system consisting of two water chambers connected via springs to a buoy that is floating on the ocean surface. This buoy is in addition connected via springs to a mooring buoy below the ocean surface. The spring mass system has a natural oscillating frequency that is equal to or lower than the frequency of the ocean waves. This will result in transfer of energy from the ocean waves into the spring mass system. The energy is extracted from the system by braking the relative movement between the masses. The brakes use braking forces equivalent to the critical damping forces of the mass spring system and convert the braking forces into electrical energy.  

The illustration above shows a power plant consisting of 4 energy converters where each surface buoy has a diameter of 3 m. The 4 energy converters are moored to 2 anchors on the ocean floor.  Electrical cables (not shown on the drawings) may be mounted along the mooring lines to the sea floor and further to shore. The surface buoys with water chambers and springs are free to rotate around vertical axes when the ocean waves change direction. The distance between the surface buoys may be larger than shown on the drawing.

Estimated amount of produced energy from the power plant:

Wave height 1 meter with wave periode 6 sec:                  26,8 kW  

Wave height 1,5 meter with wave periode 6,5 sec:            65,6 kW

Wave height 2 meter with wave periode 7 sec:                 126,0 kW

Wave height 2,5 meter with wave periode 7,5 sec:          210,8 kW

Wave height 3 meter with wave periode 8 sec:                 324,0 kW

Advantages of the method:

- relative low amount of materials to manufacture the power plant

- high efficiency in different wave heights

- ability to resist large wave forces due to flexible mooring of the components and as components are placed

   some distance below the surface where the wave forces are smaller

- the number of anchors on the ocean floor is small

Plant for conversion of ocean wave energy into electrical energy

(Click here for description in Norwegian)