Tidal energy is a type of hydropower that depends on the kinetic energy in the tides to create energy, mostly for electricity. It works by taking advantage of the rising and falling of the tides. During high tide, the rising water spins turbines and as the tide goes out the turbines spin again and collect the kinetic energy from the water. Currently, the Sihwa Lake Tidal Power Station in South Korea is the largest tidal power installation. The Sihwa plant has a total power output capacity of 245 MW. Because collecting tidal energy depends on the gravitational pull between the earth and moon, it is a renewable energy and will not run out.
Tidal energy, however, has many downfalls. The equipment is very expensive initially, although it can be installed on already-present buildings in the water such as bridges. Another downside is its possible negative affect on marine life. Fish and animals may get stuck in the turbines, or they could also be affected by the noise generated by the turbines, if they depend on echo-location. However, this does not affect the entire water supply, just in the proximity of the equipment.
Although tidal energy is not going to be our primary energy source anytime soon, technological advances may make the economical and ecological cost go down soon. Tidal energy may be worth the investment of research because tides are more constant and predictable than other alternative renewable energy sources such as solar or wind energy.