The idea of using the energy of the tides is not new. Tidal mills were built in France, Spain and Portugal as early as the twelfth century. A mill powered partially by tidal energy was built at Port-Royal, Nova Scotia, a National Historic Site of Canada in 1607. These early mills extracted the equivalent to power 10 modern homes (30-70 kW). A few of the early mills are now preserved as historic sites as the one existing in the National Park of Isla Cristina located in Huelva, Spain which is a touristic attraction and was built in XVIII century to mill grains. The recent history of the use of tidal energy start just after the oil crisis in 1974 where several designs for marine energy resources and tidal projects were created.
On the left, an old tidal mill located North of Spain, Picture from Raúl Hernández González (Flickr)
Later on, in 1976 an energy British company prepared a study which concluded that marine power, especially tidal energy, deserved more detailed research. After that, some UK companies started a research program to deploy prototypes of machines to harness the marine currents and tidal energy. In the 80s decade, important studies were carried out in UK, Canada, and Japan. In 1992 there was an important effort from the Tidal Stream Energy Review identifying specific sites in UK waters with suitable current speed to generate big amounts of energy. Out of these studies it was confirmed that approximately big amount of UK electricity demand (around 20%) could be covered with tidal power, if the necessary technology was developed. Afterwards, in the mid 90s, a European database was created to assess sea-bed sites where tidal energy could be harnessed and with high power densities.
According to the international studies and many experts in the field, tidal energy have the potential to supply a substantial share of future Europe electricity demand. There is a study of 106 possible sites in Europe for tidal turbines showing a power generation potential of about 50 TWh/year. One of the biggest spots in the world where tidal energy is exploited is River Rance, in France. The power plant has a total capacity of 240MW and is visited each year by more than 40.000 people. While estimates of global tidal potential may vary, it is commonly agreed that tidal power capacity exceeds 120GW around the globe. The UK has one of the largest marine energy resources in the world, estimated to be more than 10GW, representing about 50% of Europe’s tidal energy total capacity.
Tidal power projects are generally expensive because massive structures must be built in difficult environments but if this resource is to be harnessed, the technology required could form the basis of a major new industry to produce clean power for the 21st century.