There are three main types of turbines.  There’s the bulb turbine, the rim turbine, and the tubular turbine.  In a bulb turbine, water flows around the turbine.  Maintenance can be a problem: it can be time consuming and result in loss of generation.  In the rim turbine, the generator is mounted at a right angle towards the turbine blade.  Although access is easier, this type of turbine is not good for pumping and is difficult to regulate performance.  With the tubular turbine, the blades are connected to a shaft and are placed at an angle so that the generator is sitting on top of the barrage. 
     Another recent technology uses the kinetic energy of the tidal waves to generate power.  These turbines function best when wave currents run between 4 and 5.5 mph and are most likely found in water depths of 68.5-98.5 feet. 
     Current locations that use tidal power are St. Malo, France, which uses twenty-four 10-megawatt low-head bulb-type turbine generator sets and was the first commercial-scale modern-era tidal power plant.  The barrage was installed in 1965 and hasn’t missed a tide in 38 years.  Another one is at Annapolis Royale, Nova Scotia, Canada.  This one was built in 1982 to demonstrate the functioning of the STRAFLO turbine.  There are approximately 10 small barrages scattered throughout the world, but they are not intended for commercial power generation.  There is a 200 kW tidal barrage on the River Tawe in Swansea Bay, Wales that operates the gates of a lock. China has several tidal barrages of 400 kW and less in size.  There is currently a project being done in Northern Ireland.  The project is called the SeaGen.  It is currently running at 150 KW, and the turbine will be constrained to 300 KW.  Once the project is complete, SeaGen will have a capacity of 1.2 MW.  The SeaGen is shaped like a wind-turbine and generates electricity as water pushes past the slow moving blades that are underwater.