Device for converting wave energy into electrical energy

It is a floating device tethered with chains to piles driven to ocean bottom. The wave action raises the heavy partially buoyant piston that drives the overhead crankshaft by half turn. The receding wave drops the piston completing the balance half turn. One revolution is obtained for every wave. Using gear box and generator the current is produced continuously.

Detailed description of the working of Indian wave energy device (iwave)

The ocean wave energy is very complex and hence it has been very difficult to tap it. The design of the device is most important for the successful production of cheap energy.

We all know that it is the energy that moves in the waves and not the water. It is the energy that raises the wave height and not the water. If you remove the energy from the water the wave height will not increase.

This device is positioned facing the waves and floating on the water at a point near shore where the waves rise significantly above the sea level. The waves travel towards land parallel to the shoreline. Piles are driven into the ocean bottom and by means of chains/stay wire the device is tethered to prevent its movement horizontally and vertically

The walls of the device help concentrate the waves into the opening. As the waves strike, the heavy buoyant piston rises driving an overhead crankshaft by half a turn. When the waves recede, the piston drops pulling down the crank by another half turn thus completing the rotation. The crankshaft connects gearboxes and alternators on either side to produce electricity. This is the simple working. Complexities arise due to variation in

  • Wave height.
  • Time elapsed when each wave strikes.
  • Combination of small and big waves.
  • Storms.

Imagine a bicycle and the pedal shaft is your crank. The more pressure you give on the pedals the faster you go. You give partial pressure you go only by that much. You reverse pedal nothing happens. You go fast downhill the speeding wheels do not influence your pedal. The energy is transferred in one direction only i.e. from the pedal to the wheel and not vice versa. The energy transferred could be intermittent (partial pedaling). The wheels move steadily without stalling based on the intermittent energy received.

The above analogy is used to describe the working of this device. Whenever the waves are higher, the torque exerted by the rising piston is higher. This higher torque is transferred by the crank to gearbox to the freewheel (alternator). Higher the torque, faster movement of the free wheel (alternator) tends to happen. In this condition more current can be produced. If excessive wave (like in a storm/tsunami) conditions are encountered a provision can be made at the top of the device to release the water and protect the device. The device can also be shut down by closing the walls.

For lower waves the torque exerted by the rising piston is lower, thus reducing the speed of the free wheel (alternator) and consequently the current produced is also reduced. The piston acts as a damper and transfers the energy as is received from the wave. The waves entering the device can be increased by extending the walls as and when required.

For very small waves the piston moves up partially, transferring energy to crank/gearbox. The crank will drop off without attaining full revolution and the piston will wait for the next wave.

Additional energy storing rotating wheels can be added to the device at the alternator end to maintain uniformity in the rotation in the short run, in spite of uneven energy transferred to it.

The rotation of the alternator is never stalled since it is a free wheel. The crank and gearbox may stop intermittently based on the wave condition and piston movement. As the next wave comes the crank and gearbox rotates. Depending on the intermittent transfer of energy from the crank/gearbox the speed varies. Intermittent transfer of energy is expected and provided for in the design. Thus the movement of the free wheel (alternator) does not influence the gearbox/crank/piston, whereas the forward movement of the piston/crank influences the gear box leading to rotation of the free wheel.

The device is simple and easy to maintain. All electrical and critical parts are above water and hence are easily accessible. Being a near shore device it can be accessed easily and economical maintenance is possible. The evacuation of the current is easy and no expensive cabling is required.

As compared to all other devices, in this device, the wave energy is directly converted to mechanical energy that produces the electricity using the alternator. Hence the energy losses are barest minimum. Other devices that convert from wave energy to pneumatic/hydraulic have substantial energy losses that the useful energy generated from a given sea wave is a fraction of the energy available in the wave. The energy produced by this device can compete with all other forms of energy.

<< back