Tidal

Gravity from the moon and sun cause water in the ocean to bulge in a cyclical pattern as the Earth rotates, causing water to rise and fall relative to the land in what are known as tides. Land constrictions such as straits or inlets can create high velocities at specific sites, which can be captured with the use of devices such as turbines. Since seawater is about 800 times denser than air, tidal turbines can collect energy with slower water currents and smaller turbines than wind energy. While tidal currents are very predictable, challenges arise because devices need to collect energy from flow that changes direction and survive the harsh corrosive marine environment. Power may also be produced by extracting potential energy from the rise and fall of the tides in a manner similar to conventional hydropower. Modern tidal power generating turbines operate on the same principles as wind turbines. As the moving water passes the turbine’s blades, the current’s kinetic energy is converted into mechanical energy as the rotating blades spin a drive shaft. The mechanical energy in the drive shaft is then converted to electrical energy using a generator, often through a gearbox.