The Wave Energy Resource

On an average day, about 1TWh of wave energy enters the coastal waters of the British Isles. It is tempting to call this amount huge - it is about the same as the to-tal energy of the terrible Indian Ocean tsunami of the 26th of December 2004. It brings home the scale of human energy demands to realise that this is also about the same amount of energy as is used in electricity in the British Isles on an aver-age day. The same approximate equivalence holds at a world scale: the total wave energy resource is of the same order of magnitude as world electricity consumption (~ 2TW). The exploitable limit is probably at most about 10-25% of the resource; thus ocean wave energy is potentially a significant contributor to human energy demands, not a panacea. Its key advantages are that it comes in a high quality form - mechanical energy of oscillation - and that it travels very long distances with little loss, so that small inputs over a large ocean can accumulate and be harvested at or near the ocean’s edge. Other advantages include the point absorber effect, whereby devices can extract energy from a fraction of a wavelength on either side; this makes small devices, with capacities of the order of 1MW, relatively attractive.