• A machine or device to extract energy from ocean waves is called the Wave Energy Converter (WEC).
• A point absorber type WEC includes a floating structure i.e., a buoy which absorbs energy from all directions through its movements at or near the water surface.
• It undergoes heave motion under the action of ocean waves and converts the motion of the buoyant top relative to the base into electrical power.
• In order to extract maximum amount of energy from the ocean waves, a WEC’s natural frequency must match with the frequency of incoming waves or mathematically speaking, the force acting on the WEC due to waves must be in phase with WEC’s velocity. This condition is termed as Resonance.
• However, there are two main hindrances to achieve resonance. First, ocean waves are low frequency waves whereas WEC oscillates at a high frequency. Second, ocean waves are random (irregular) waves i.e. frequency of ocean waves varies rapidly whereas WEC oscillates at a single frequency. The present invention describes a point absorber-type WEC that overcomes some of the drawbacks of the existing converters.

• The invention proposes a Point absorber type Wave Energy Converter (WEC) and a method for efficient extraction of energy from the ocean waves.
• The WEC comprises of a buoy that floats on the ocean’s surface and a chamber that contains the bi-stable configuration of springs and magnets.
• The buoy absorbs energy from all directions through its movements at or near the water surface and undergoes heave motion under the action of ocean waves.
• The chamber further includes a power take-off mechanism to convert the heave motion of buoy into electrical output.

METHOD

• The method includes a bistable configuration of springs and magnets to reduce the natural frequency of buoy by countering its hydrostatic stiffness. (Fig.1)
• The bi-stable configuration also allows the buoy to resonate with the ocean waves at wide range of frequencies due to which the buoy’s hydrodynamic performance is enhanced significantly.

FIGURE

Fig. 1: the analogy between a buoy floating in water and a body lying on flat surface connected to a spring having stiffness equal to the hydrostatic stiffness of buoy.

Fig. 2A: the configuration of wave energy conversion system at equilibrium when there is no wave activity.

Fig. 2B: the configuration of wave energy conversion system during wave activity.

Fig. 3A:the side view of experimental setup for analysis of buoy with bi-stable configuration.

Fig. 3B: the top view of experimental setup for analysis of buoy with bistable configuration.