Speed Multipliers for Renewable Energies

Generating Electricity from Oceanic Tidal currents.

Tidal currents carry kinetic energy that can be tapped and turned into a important energy source. When such currents are channeled into narrow locations by the neighboring land masses, their speed, and energy density increase.

Europe has over 100 sites with major ocean currents. Their total energy potential is estimated to be around 12.5 GW. The United Kingdom, Ireland, France, Spain, Italy and Greece hold the best emplacements, that may be able to generate over 10 MW/km2

Advantages :

  1. Predictable availability.

  2. Higher power generation capacity than other intermittent renewable energy systems. For example while a 15 m/sec wind generates 2 kW/m2, a 2 m/sec ocean current generates 4 kW/m2 and 3 m/sec one produces 14 kW/m2

  3. Low environmental impact, since there is neither visual nor acoustic pollution, and the slow immersed rotors do not affect marine life.

  4. Storm immunity.


  1. The single major disadvantage is navigational traffic impact, since the best currents are mainly found in or near straits and wide river mouths, that usually sport marine traffic.


Marine electric power generation technology is similar to the one used in wind turbines, only situated undersea. The rotor turbine is mounted on a fixed structure on the sea floor, or suspended from a float. It is best to position the rotor close to the surface, where water velocities are higher.

With both tidal and oceanic currents, electric power is generated by a low speed rotating blade. This low speed rotation is converted by a “speed multiplier gear unit”, to an appropriate input speed for an electric generator.

Water is 1000 times denser than air and thus generates very high forces, even with low flow rates. This requires specifically designed transmission systems, since undersea rotor blades are considerably smaller than wind turbines. Even at low speeds, the whole system of power generation, blades, bearings, speed multiplier gearbox and electric generator is subjected to high forces. Speed multiplier gearbox transmission technology is an area where Servotak has working prototypes in submarine applications.