The wave power in the ocean is mainly defined by its own height (H) and period (T).

The height of the wave is the predominant parameter in determining the amount of energy of a wave since its Energy (E) is proportional to the square of the height. In other words, if wave A is 2x the height of wave B, the energy of wave A will be 4x greater than that of wave B.
The height of a wave is defined by the distance from the crest (highest point) to the trough (lowest point). Wave height is for sure the most know wave feature in or out of the surf/science world, and that’s it because is the easiest way to characterize a wave when you look at the sea. When the sea is flat or crowded by big hollow waves, the height of that water perturbation is what comes to mind immediately.

What’s the power of this wave?

It’s quite hard to define the direction of the waves just looking especially when you aren’t a specialist. The period comprises the time spent between the passage of two successive waves through a fixed point and the wave energy is directly proportional to its period, so the longer the period of a wave, the greater its energy. Close to the beach in shallow waters, it’s possible to estimate the wave period using a simple and very known technique. The waves are counted over a certain period of time, and then can be found the approximate wave period of each wave. This is not feasible in the deep ocean, where the waves have another moving approach as they not feeling the ground.

The wave energy can be divided into kinetic and potential energy.
The first one refers to the movement of the water particles that cause the wave motion, while the second refers to the vertical distance of the wave crest at the average level of the water. The power of a wave can be defined as a flow of energy, resulting from the sum of the en. kinetic + potential, multiplied by its speed.

In the image, we have a wave height of approximately H = 2.5m (vertical line) as the bodyboarder was used as a scale,  a period (T) of 12 seconds, and a crest length (horizontal line) of approx. 5 meters. With this information, we can calculate the power of this wave’s wall, for the total length of the crest (5 m).

Using the equation above, we have: P = 225kWh / 5m.

It’s very important to say here that it is an approximate result since this equation used is derived from the linear wave theory which is designed for waves with small heights that propagate over deep water conditions. When the waves are breaking due to the depth like in a surfing wave, or just because of the steepness as occurs in the deep ocean, the mathematical treatment should be more robust using non-linear equations that consider bottom effects, wave-wave, and wave-current interactions.

Leave a Reply

deep knowledge on sea waves

Lisbon, Portugal