Ocean waves: How energy resides
How waves pack wind energy into a narrow coastline
What this tab covers The physical form in which the energy is held or carried, where it comes from, the chain of transformations that put it there, and how concentrated it is.Ocean waves carry energy that the wind has transferred to the sea surface, held half as kinetic energy of moving water and half as potential energy of water lifted above the mean level. Waves concentrate wind energy: a good Atlantic coast receives 50 kW or more per metre of shoreline.
Form Kinetic and potential energy of oscillating surface water Origin Indirect solarHow it got there
Fusion in the Sun Sunlight Uneven heating of the Earth Wind Wind drag on the sea surface builds waves Waves travel thousands of km as swell Energy arrives at coastsHow concentrated it is
| Measure | Value | Note |
|---|---|---|
| Wave power per metre of wave crest | about 0.5 x height squared x period kW per m (height in m, period in s)2 | Deep-water formula. A 2 m, 8 s sea gives about 16 kW/m; a 3 m, 10 s sea about 45 kW/m (calculated). |
| Energy stored per square metre of sea surface (regular 2 m waves) | about 5 kJ per m2 (for 2 m waves)2 | Calculated from E = 1/8 x water density x g x height squared for regular waves (half for an irregular sea of the same significant height); half kinetic, half potential. |
| Best open-ocean sites (southern Indian Ocean) | above 120 kW per m3 | Between Kerguelen Island and southern Australia, significant wave heights of 4.5 to 5 m. |
| Threshold for a technically useful resource (US assessment) | 8 kW per m6 | Below this annual average the US national assessment counts no technical resource. |
Wind blowing over water pushes and drags on the surface, building ripples into waves. The longer and stronger the wind blows, and the greater the stretch of open sea (the fetch), the larger the waves become. Once formed, waves travel as swell for thousands of kilometres with little loss, so a storm in the mid-Atlantic delivers energy to Ireland or Portugal days later.
This makes waves a concentrated form of wind energy. The water's motion stores only a few kilojoules per square metre of sea, but because the energy travels, a metre of coast facing a big ocean can receive tens of kilowatts on average. The challenge is mechanical: the energy arrives as slow, heavy, reversing oscillations in a corrosive environment, with storms many times stronger than average conditions.
Sources
- Study Pelamis system to capture energy of ocean wave (Equation 1: wave power per metre of crest) arXiv, 2015
- Review of Wave Energy Resource Characterisation, Metrics, and Global Assessments (Ramos-Marin and Guedes Soares, Journal of Marine Science and Application 24, 53-75) Springer / Harbin Engineering University, 2025
- Marine Energy in the United States: An Overview of Opportunities (Kilcher, Fogarty and Lawson, NREL/TP-5700-78773) National Renewable Energy Laboratory / US DOE, 2021