Nautricity’s CoRMaT Spins This Way and That


Nautricity is a UK company that develops tidal energy technology. Its CoRMaT tidal turbine, a 500kw device in its largest form, will be installed and tested in the Thames River alongside a former Royal Navy sloop called the HQS Wellington (see Clean Technica article).

The CoRMaT turbine is the subject of at least one international patent application, WO 2007/017629, and U.S. Application Publication No. 2008/0226450 (’450 Application).

According to Nautricity’s web site, the CoRMaT turbine is the result of R&D conducted at the University of Strathclyde, which is the owner of record of the two patent applications.

The ’450 Application is directed to a turbine (5) having two adjacent sets of coaxially mounted blades. The first set (10) is coupled with a first shaft (20); the second set (15) is coupled with a second shaft (25).

The first shaft (20) is directly coupled with a rotor (45) of a generator (50), and the second shaft (25) is directly coupled with a rotatable stator (55).

The first set (10) of blades (65) contra-rotates relative to the second set (15) of blades (66). This causes contra-rotation of the respective shafts (20, 25) and of the rotor (45) and the stator (55) of the generator (50).

According to the ’450 Application, generator performance can be optimized by arranging the blade sets (10, 15) so one set cannot be completely eclipsed by the other at any point in the power generation cycle.

Nautricity’s web site describes the turbine technology as:

two closely spaced contra rotating rotors, driving a contra rotating electrical generator. The first rotor has three blades rotating in a clockwise direction while the second rotor, located directly behind the first, has four blades rotating in an anti-clockwise direction.

According to Nautricity, the contra rotating rotor arrangement doubles the relative rotational speed compared to a single rotor turbine and splits the torque equally between the two rotors.

The torque-splitting eliminates reactive torque acting on the support structure, thereby allowing the turbine to be moored rather than rigidly attached to the seabed.

Thus, the CoRMaT can be deployed in a variety of locations at depths varying from eight meters to 500 meters.

According to Nautricity’s press release, the trial is the first stage in a large project to site hundreds of tidal turbines along the river and generate enough electricity to power 35,000 homes.

Eric Lane is a patent attorney at Luce, Forward, Hamilton & Scripps in San Diego and the author of Green Patent Blog. Mr. Lane can be reached at elane@luce.com.



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2 comments on “Nautricity’s CoRMaT Spins This Way and That

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It seems like this same concept would be useful for wind turbines, and yet I see none like it. Is that because the people developing wind energy just never thought of this idea?

Could be because one of the problems being solved by the torque-splitting here is dispensing with the need to rigidly attach the turbine to the seabed, not an issue for most wind turbines.

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