Tidal Stream Energy and How it Works

Undersea currents are one of the oldest forms of power known to man and have been harnessed for their energy for millennia. Tidal energy is produced by the surge of ocean waters during the rise and fall of tides.

By the 20th century, engineers had devised many methods to use tidal movement to generate electricity in areas where there is a significant tidal range, all of which used special generators, drawing energy from currents in much the same way as wind turbines.

Tidal stream power systems take advantage of ocean currents to drive turbines, particularly in areas around islands or coasts where these currents are fast. They can be installed as tidal turbines, which resemble underwater wind turbines.

As a relatively new technology, first conceived in the 1970s during the oil crisis, the potential for power generation from an individual tidal turbine is greater than that of a similarly rated wind energy turbine. This is because water is 832 times denser than air, providing greater resistance and energy generating potential.

Tidal power can be produced with slower rotation speeds (e.g. 6 RPM tidal versus 20 RPM wind), and smaller rotor diameters (e.g. 15-meter tidal versus 45-meter wind). By comparison, an underwater turbine is able to generate energy at 2.2mph, while a wind turbine would need speeds of 7-9mph to produce power.

Given that power varies with the density of the medium, water speeds of nearly one-tenth of the speed of wind provide the same power for the same size of turbine system. Furthermore, at higher speeds in a flow between 2 to 3 metres per second a tidal turbine can typically access four times as much energy per rotor swept area as a similarly rated power wind turbine.

Sustainable Marine’s PLAT-I (PLATform for Inshore energy) technology offers an innovative take on tidal energy, through a floating tidal energy system, which is the first of its kind in the world. Its modular design allows for it to be easily assembled on-site and only requires 2 meters of water for launching.

Meanwhile, the system is moored with a turret configuration allowing it to ‘weather-vane’ with the tide or river flow. PLAT-I’s turbines are also mounted on SIT Deployment Modules (SDMs) allowing them to be quickly raised above the surface for inspection and maintenance, while also reducing draft for transit.