Swell and its energy

Wind drives the swell

Wind blowing for a long time over a large stretch of ocean passes its energy to the surface. Waves formed offshore then travel thousands of kilometres with very little loss: this is swell, regular and powerful, reaching the coast even on calm days.

L = \frac{g T^{2}}{2 π}

Longueur d’onde en eau profonde : g pesanteur, T période

How much energy?

The energy carried grows with the square of the height and in proportion to the period. A 1.5 m, 10 s swell brings about 11 kW per metre of coastline; a storm swell brings hundreds.

P = \frac{ρ g^{2}}{64 π} H_{s}^{2} T_{e} \approx 0,49 H_{s}^{2} T_{e}

Puissance de la houle par mètre de front de vague (kW/m) : Hs hauteur significative (m), Te période énergétique (s)