Tidal energy is a renewable form of energy converting tides into power. Tides are created as a result of gravitational forces exerted by the Moon, the Sun, and the rotation of the Earth. Tidal energy technologies are evolving rapidly providing tremendous opportunities for green energy generation. Although for now, tidal power is not the cheapest energy source and its effect on the environment is not fully determined, new tidal technologies are expected to eradicate the potential issues.

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Interaction of the gravity of the sun, earth, and moon cause tides. High lows and tides are formed when the moon's and the sun's gravitational powers pull water upwards and the Earth’s power pulls water down. These motions of the tide create kinetic energy, which can be harnessed as renewable energy. Tidal energy can be generated along the coastline with the water difference starting from 5 meters high. The energy is predictable having two high tides and two low tides daily. 

Although new technologies of harnessing tidal energy have started to be developed only recently, the idea of using it can be traced back to ancient times. The Romans used tidal power turning wheels and grinding grains. In 1966, the first barrage producing tidal energy and generating electricity was created in France, which resulted in the development of numerous tidal plants globally. Today, the Sihwa Lake project in South Korea is the world’s largest tidal power station with 10 water turbine generators, an installed capacity of 254MW, and the potential to support households of approximately 500,000 people. 

The main technologies to harness tidal energy:

  • Tidal stream method is generating energy by placing the wheel-like turbines on the ocean floor and having them be pushed by the water.
  • Tidal barrage is a large reservoir in the ocean with the water flowing through tunnels inside it. The turbines inside the tunnels are pushed with the tide phases changing.
  • Tidal lagoons work similarly to the tidal barrages as they catch the ocean inside a dam, except they might be placed in the ocean without being connected to the shore.
  • Ultra-low-head tide is a new method allowing to generate power from tidal differences of less than 2 meters.
  • Hybrid forms of tidal energy are innovative technologies applied in multi-purpose platforms. 

Advantages of tidal energy

  • Renewable energy source. Gravitational fields from the sun and the moon in unity with the earth's rotation produce tides. This process will always exist and using its potential does not deplete natural resources.
  • Environment-friendly energy source. Tidal power does not emit any climate gases.
  • Predictable energy output. Due to the stability of the tides’ cycles, the amount of energy produced can be predicted and planned. 
  • High power. Water is about 1000 times denser than the air, that’s why tidal plants can generate a lot of energy at a low speed. 
  • Innovations in technology. New approaches in generating power from tidal energy make more efficient and cheaper technologies. 
  • Long lifespans. The tidal power equipment lasts about 4 times longer than wind and solar technologies with an asset life of 100-120 years.

Disadvantages of tidal energy

  • Environmental effect. Although tidal energy does not emit carbon and is renewable, it is still not completely clear how manipulation on ocean level might impact the sealife. 
  • Expensive. Tidal power plants need to have strong construction to be protected from sea force destruction, which raises the development cost. The innovative approaches in tidal power are supposed to reduce the costs in the nearest future. 

Tidal gaps. With the tide going in and out twice a day the power can be generated only about 10 hours daily requiring large battery energy storage for more effective use.

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