Short History

Milestones

Tide mills

Tide mills were in use on the coasts of Spain, France and the UK before 1100 AD and in tidal estuaries (e.g. the Schelde River in Belgium) around 1800 AD. They remained in common use for many centuries, but were gradually replaced by cheaper and more convenient methods of power generation. Tidal mills remained established until the 18^th century when their major competitors were windmills and waterwheels. A tide mill consisted of a pond filled through a sluice during the flood tide and emptied on the ebb tide via an undershot waterwheel. Tide mills basically disappeared with the introduction of cheap steam engines. The only large modern version is the 240 MWe La Rance scheme, built in France in the 1960s, which is the world’s largest tidal barrage, using conventional bulb turbines.

Wave energy

The first patent for a wave energy device was filed in Paris in 1799. It was a barge connected by a long lever with a water pump. However the device was never built because of technical difficulties. By 1973 there were already 340 British patents for wave energy devices and the number continues to rise. Considerable research and development was initiated in several countries following the second oil price shock and numerous prototype devices have been developed. However, enthusiasm gave way to some scepticism because of the high cost estimates associated with early prototypes. Despite this, considerable progress was made during the 1990s. Today several companies are developing and deploying new devices that represent a significant improvement over older concepts.

Currents energy

Tidal and marine current energy is the most recent of the marine energy resources to be seriously studied, with most work dating from the 1990s. All that has been done so far is the short-term demonstration of small experimental model systems in the sea.

Ocean energy

Exploiting natural temperature differences in the sea by using some form of heat engine, potentially the largest source of all renewable energies has been considered and discussed for the best part of 100 years. The concept of converting ocean energy into electricity, being envisaged by the French physicist Jacques Arsene d'Arsonval, goes back to 1881. The first working OTEC appeared some time later in 1928, when Georges Claude, a French engineer, constructed a machine to utilize the temperature difference of the ocean. He simply drove warm surface water into an evaporator. When pressure was lowered the water vaporized, which was then forced through a turbine to generate electricity. To begin the cycle anew, the vapour was cooled by cold water piped from lower ocean depths. Although Claude actually invented the first prototype version of open-cycle OTEC, he finally abandoned it, as its operation required excessive maintenance.