Hydroelectric and Tidal Energy

Both hydroelectric and tidal energy, often called wave energy, work in a similar way. There is a huge dam that prevents water from flowing through, as it normally would. This means that there is a water imbalance on both sides, with one side having a much higher level of water than the other side.

The difference between the two renewable energy sources is how the water causes an imbalance in water levels.


In a hydroelectric dam, water flowing from upstream is trapped, preventing it from flowing out to the ocean. Trapping this water for a while eventually forms a reservoir, which is a large lake where water is stored.


Tidal barrages use tides, which are the regular rise and fall of sea levels, mainly due to the effect of the Moon’s gravity. A tidal barrage is built over an estuary, which is the point at which the river meets the ocean.

We can trap the water as the tide comes in, so when the tide flows out, there is a higher water level on one side of the dam than on the other. The kinetic energy from the moving waves turn the turbines.

Wave Machines

Wave machines use the kinetic energy in the movement of waves to drive electricity generators.

Both hydroelectricity dams and tidal barrages use a difference in water level to generate electricity. The difference in water level means that the stores of water have a large amount of gravitational potential energy, which is transferred to kinetic energy.

The kinetic energy from the moving waves turns the turbine. Those turbines are connected to generators which generate electricity as the turbines spin. This water then flows through to the other side.

Advantages of Wave Energy

  • With both hydroelectric and tidal energy, large amounts of energy can be produced with no pollution.
  • Tidal barrages and hydroelectric power stations are very reliable
  • Running costs of tidal barrages and hydroelectric power stations are quite low
  • It can work with low water speeds

Disadvantages of Wave Energy

  • A big impact on the surrounding environment
  • Hydroelectric dams can flood neighbouring areas
  • Tidal barrages and hydroelectric power stations can lead to an ecosystem imbalance when fishes are stopped from travelling up and down the river
  • The initial setup cost are expensive