In coastal areas with large tides, flowing tidal waters contain large amounts of potential energy. The principal of harnessing the energy of the tides dates back to eleventh century England when tides were used to turn waterwheels, producing mechanical power. More recently, rising and falling tides have been used to generate electricity, in much the same manner as hydroelectric power plants.
Tides originate from the motions of the earth, moon and sun.
Although ocean tides contain extremely large amounts of energy, it is only practical to generate electricity at sites with exceptionally high tides such as the Bay of Fundy in Atlantic Canada which, at up to 17 metres, has the highest tides in the world. Tidal energy is an essentially renewable resource which has none of the typical environmental impacts of other traditional sources of electricity such as fossil fuels or nuclear power. Changing the tidal flow in a coastal region could, however, result in a wide variety of impacts on aquatic life, most of which are poorly understood. Gravitational Energy Tides, the daily rise and fall of ocean levels relative to coastlines, are a result of the gravitational force of the moon and sun as well as the revolution of the earth. The moon and the sun both exert a gravitational force of attraction on the earth.