A tidal turbine is a method of generating electricity from tidal flows. It uses a turbine strategically placed in a tidal area to change the mechanical energy of the moving water into electrical energy which is then distributed to consumers.
There are three major type of tidal turbines: bulb turbines, rim turbines and tubular turbines.
A bulb turbine is a turbine that has the generator inside it. This means that it is very efficient in terms of space and size--by putting the generator inside the turbine, the need for a separate housing unit is eliminated, which means the turbine is less of an eyesore.
On the other hand, these turbines cannot be maintained without stopping the flow of water to them. This means that when the inevitable maintenance needs to be carried out the turbine will have to stop producing power for the duration of the maintenance.
A rim turbine's generator is separate from the turbine itself, and is connected through a shaft that moves with the turbine. This means that the generator can be maintained easier. However, the more-delicate nature of the rim turbine means that it is harder to pump water through it and regulate the amount of power it produces. Where the bulb turbine is hardy, yet difficult to maintain, the rim turbine is precisely the opposite.
Tubular turbines are the turbines already commonly used in hydroelectric power generation. Rather than have the generator mounted directly on top of the turbine, it is mounted at a 45-degree angle from it.
However, the real advantage of a tubular turbine is that the blades can be adjusted. This means that they can be changed to meet electricity demand; smaller blades will generate less power while larger blades will generate more power. This allows the turbine to run more efficiently, generating only the amount of power it needs to without excessive wear and tear.