This study presents how tidal power is being harnessed internationally and furthermore introduces different methods of harnessing tidal energy. Its objective is to present the basic concepts of tidal phenomenon, thus representing different power plants working with alternative principles. Research materials have been acquired mainly from the industry’s studies and from the tidal power plants manufacturers’ web sites.

Tidal power plants can be divided in two different main categories: potential energy tidal power plants which consists of dams and lagoons, and kinetic energy tidal power plants including tidal turbines which are powered by tidal currents. Dams’ and lagoons’ basic principle is same as in hydropower but in tidal power the water runs regularly in both ways. Tidal turbines that harvest the energy from tidal currents work like submerged wind turbines.

Tidal power can offer cost-effective and fully renewable energy when the required terms are met. Tidal power plants require a suitable location where tides are big enough, so that limits locations obviously. Economies of scale applies to dams and lagoons so they need big investments so the electricity production can be profitable. The La Rance Tidal power station was constructed in France in 1960’s and it can be used as a great example of the cost-effective long-range solution that tidal power has to offer. The La Rance power station’s payback time was under 20 years and after that it has been one of the world’s cheapest forms of energy, producing energy fully renewably.

Other tidal power plants are being developed and at the moment the biggest project is Swansea Bay Tidal Lagoon in Great Britain. This is still in development and if it is decided to be constructed, it will need an estimated investment of 1.5 billion euros so it could produce electricity inexpensively for the next 120 years. About 10 times bigger tidal lagoon is also planned to Cardiff. It could power every home in Wales for the next 120 year fully renewably.