Tidal Turbines
In many ways, tidal turbines used for energy from tidal streams are analogous to wind turbines, in terms of the general shape, mounting and fixing technology, and power take-off system designs. The one critical difference between wind turbines and wave energy turbines is the size. For instance, tidal turbines generating 1 MW of power have sizes that are only about a third the size of a wind turbine with a similar generating capacity. Tidal turbines are arrayed underwater in rows, as in some wind farms. Ideal locations for tidal turbine farms are close to shore in water depths of 20–30 meters (65.5–98.5 feet). The turbines function best where coastal currents run at between 3.6 and 4.9 knots (4 and 5.5 miles per hour). In currents of that speed, a 15-meter (49.2-feet) diameter tidal turbine can generate as much energy as a 60-meter (197-feet) diameter wind turbine. Tidal Turbines Source: esru.strath.ac.uk The majority of tidal energy companies are developing horizontal axis turbines that are similar to wind turbines. Other types of tidal turbines being experimented are: 
