Ocean Energy, Tidal and Waves Blow Holes

There are other options to generate energy from the ocean waves and tides, among these we can mention a “blow hole caves” this could be a natural cavern modified to make it more suitable for converting it into a power generation system, or could be designed and constructed specifically for it. In this proposal the sea level variations due to waves and tides gets in and out of this pressure chamber forcing a huge amount of air to be expelled through a blow hole or exhaust pipe connected to high speed turbines. The air traveling through the pipe can reach very high speeds and can pack a lot of power. The air is pushed through the blow hole,

Just to show how powerful this system could be, lets assume the hypothetical system with the given dimensions and also considering that the system was well engineered, and the location was properly selected to obtain the most power possible

A= 100 meters (cavern depth)

B= 3 meters (height at the cavern entrance)

C= 100 meters (cavern entrance width)

D= 2 m2 (Transversal area of the exhaust pipe)

Wave Speed entering the cave = 3 m/second

Water mass receding speed = 2.5 m/second

If the cavern is completely empty at the time the wave front arrives at the gate and the whole gate is fully flooded by this front, the air volume to be displaced by the water mass will be:

Volume Displacement = A x B x C = 30,000 m3

If the speed of the wave entering the cave is as said 3m/sec, then the cavern air volume that has to be expelled is:

The total air volume expulsion time will be = A/Wave Speed = (100 m)/(3m/sec) = 33.33 seconds, in other words, all 30,000 m3 need to be expelled in just 33.33 seconds via the 2 square meters pipe.

The rate of air volume displacement will be = (30,000 m3) / (33.33 sec) = (900 m3) / sec

For the 2 m2 exhaust pipe the rate of expulsion per square meter will be:

= (900 m3) / 2 m2 = 450 m/sec; this is the speed at the which the air will be expelled by the pipe which is quite high, although the real speed could be less because the water front is not uniform and the compressed air would slow down the water in rush.

These calculations are just approximations because other considerations need to be taken such as average water density with air bubbles, air compression factor, cavern inside surface texture, length and quality of the wave etc, but in any ways these calculations give a good approximation of how much power can be harvested from this system.

This system concept has also the ability to work in reverse, during the wave receding cycle the cavern is emptied producing a vacuum that is filled trough the pipe, resulting in a very powerful suction effect.

The turbine(s) can be attached to diverse mechanisms like transmission gears flywheel to extend the inertial movement and store energy, attach an electrical power generator, a water pump to feed a reservoir tank and from there by gravity control a small power hydroelectric plant or any other device.

In nature exist some small blow holes that mainly serve as tourist attraction, examples are

“La bufadora” at the south of the city of Ensenada Baja California Mexico and the Halona Blow Hole in Oahu Hawaii.

In Scotland one similar actual operational system is in service since November 2000, in In this system a rectangular “box” or chamber is designed to permit the wave enters via the lower side, each time the shore wave penetrates in this box the water forces the air trapped inside to pass through the turbine and when the wave descends, the vacuum generated forces the air to go through the turbine but in opposite direction keeping the turbine working almost continuously, the turbine is connected to an electricity generator.