Pulled constantly by the moon's gravity and warmed by thermal currents, the ocean's energy is created by winds whipping across its surface. The greater distances involved, the higher and longer the waves will be. Energy is stored in the waves until they reach the shallows and beaches, sometimes with destructive force. If only two trillion watts of electricity could be harvested from the sea it would be the equivalent of twice the world's energy production from nuclear, oil, gas, and coal-fueled power stations.
One meter of a single North Sea wave front is strong enough to power 50 electric heaters. As a general rule, coastlines with an ocean "fetch" greater than 400 km (250 miles) are suitable for exploitation but even greater energy resources are available between latitudes 30
Global warming and international conservation agreements to reduce greenhouse gases have encouraged industry to investigate how the ocean's powerful energies can be exploited economically. In the UK, devolution and suitable ocean conditions has given the latest fillip to installation in Scottish waters.
Inverness-based Wavegen is installing its 500 kW Limpet turbo-generator on the Scottish island of Islay to provide electricity for the residents of the Inner Hebrides Islands. Consisting of a collector and oscillating water column, the Limpet uses wave power to force air up through the collection chamber, spinning the pneumatic turbine, which is driven in the same direction regardless of the air flow, sucking the air down and creating electricity as the waves subside.