Tidal stream power
The potential for power generation by an individual tidal turbine can be greater than that of similarly rated wind energy turbine. Water is about 800 times the density of air. So, water pushing against a turbine can provide much more power than air pushing against a similar turbine at the same speed. Also, the lowest water speeds needed for an economic power project is lower than the wind speed needed for a wind turbine project. In practice, the tide must move at speeds of at least 2 knots (1 m/s) even close to neap tides to be a source of power.