Tidal Technology

Tidal turbines work underwater in the same way as wind turbines do in the air: the pressure of the tidal flow moves the blades, generating energy which is transmitted back to the grid. Simple and robust in design, they are mounted on the sea floor and are designed to work whichever direction the tide flows. As water is around 800 times denser than air, the pressure needed to drive a tidal turbine is less than with a wind turbine, meaning that the diameter of blades can be smaller. Invisible from above the waves, they do not impact on shipping routes or on the environment.

Tidal turbines are cheaper than tidal barrages to construct and install and offer a straightforward and easy to maintain tidal energy solution.

There are currently 4 main types of tidal turbines:

1. Enclosed or Venturi Turbine:
Fixed in the tidal current, this device is mounted in a duct which concentrates the flow of water through the turbine. This can either directly drive the turbine, or an air turbine can be powered by the pressure differential.
2. Horizontal axis Turbine:
Similar to a wind turbine, the rotors are driven by the flow of water which creates energy. These can be either a single turbine per station, or dual mounted.
3. Cross-axis Turbine:
Mounted on a vertical axis, these devices work in a similar way to the horizontal axis turbines. These devices are can also be installed horizontally which is particularly good for installation in shallow water.

Images Courtesy of EMEC/AQUARET

4. Oscillating Hydrofoil
A hydrofoil is attached to a moving arm which is powered by the tidal flow. This movement drives the conversion of fluid in a hydraulic system into electricity

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