## = Vp.g.Ah, where is the volume of the cuboid, and = amplitude (A)

Now, mg. Ah = Vp.g.Ah, where V is the volume of the cuboid, and Ah = amplitude (A) of the waves. Therefore, the potential energy is:

wavelength (h)

If all this potential energy can be converted into kinetic energy then the power generated would be kinetic energyltime, and if this time corresponds to the period (T), then the power available would be:

It can also be shown that the power carried forward by a wave of amplitude (A), period (T), wavelength (X) and per unit length across the top of the wave is:

where

A typical ocean wave has wavelength about loom, period about 8s, and amplitude about 1.5 m; so that the power carried forward is about 70 kW m-'. In practice, the state of ocean waves is complex, with waves of different wavelength and direction coming together. It has been suggested that, to take into account the variability of the heights of the waves, the wave-power (P) can be expressed by the more sophisticated model:

where W is the width of the wave-front, p the density of sea-water = 1030kgm-3, T the wave period and H the 'significant wave height', which is the mean height of the highest

third of the waves. Height in this case is the vertical distance between trough and crest. For example, if the heights of 900 successive waves were measured, the top one-third would be isolated, i.e. 300. H would be the arithmetic mean of these 300 heights.