High and low tides come alternately, that is, one after the other. In high tides, the level of water rises and covers a 
part of the coast, and in low tides it flows away again. This energy of the tides is used to run turbines. Special water turbines are used in tidal power plants. Water – rising in case of high tides and receding in case of low tides – can flow through these turbines in both the directions. Electricity is generated in tidal power plants due to the rotary movement of the turbines. These power plants need a tidal hub – the difference in the height of water between high and low tides – of more than 5 m to be able to work economically. Such a power plant is in the French Bretagne, in St. Malo. Here, the tidal hub is at 12-15 m.
