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Mooring Screw-type Ocean Current Power Generation Apparatus  

Main Points: Considering Japan’s experience of a nuclear accident after the 2011 earthquake disaster, it urgently needs the development of a safe, renewable alternative to nuclear energy. We have devised a new type of apparatus for ocean current power generation—a system that satisfies the above need and can be quickly and stably implemented to provide a large amount of electric power. We invite technical companies and organizations who are eager to realize the potential of this power generating apparatus in its early development stage to apply through the Internet.
We are willing to pay for the actual fabrication cost of the demonstration apparatus.

Outline of


The apparatus is a screw-type device, which consists of water-receiving plates attached to the side of a bullet-shaped floating body. The apparatus is anchored to the seabed and can freely rotate. Since a weight is suspended from the central shaft of the apparatus so as to prevent the shaft from rotating, the shaft of a generator, whose gear is engaged with the shaft rod attached to the floating body, can rotate to generate electric power.
The apparatus allows side mooring as well as front mooring. Side mooring not only stops the rotation of the apparatus but also reduces the resistance of water caused by the screw, so that side mooring allows the apparatus to be surfaced, which makes it possible to perform maintenance work easily on the floating body.
The simple structure of the apparatus also makes it possible to fabricate it at low cost, to construct large units, and to reduce the frequency of failures caused by drifting articles. In addition, since the entire apparatus rotates slowly, failures and malfunctions caused by deposits are reduced.
The apparatus, which operates under the sea, also offers the advantage of not having an adverse impact on the navigation of ships and scenery, and there are many candidate locations where it can be placed at low installation cost.

The following estimates assume a purchasing price of 25 yen/kW for a power generation base equipped with 100 units of the power generating apparatus, with a total generating capacity of 2,669.5 kW.
Since the annual electric power generation of such a setup is 2.338 × 10 kWh in total, its annual profit will amount to 58.45 billion yen.
On the other hand, if the running costs including losses due to suspension of operation during annual inspection and repair amount to 20 million yen per unit, the expenditures for the 100 units will become 2 billion yen.
Accordingly, when the depreciable life of the apparatus is five years, it will make a profit of 282.25 billion yen during the period.
If the installation of a submarine power transmission cable costs 100 million yen per kilometer as part of the initial cost, cable installation from a location 100 km off the coast will cost 10 billion yen.
Therefore, the power generating base will be profitable when expenditures required for fabrication and mooring of the apparatus are approximately 2.7 billion yen or less per unit.

  Patent : Japanese patent No.5048882

The following estimates are for a screw 70 m in diameter with water-receiving plates attached to the side of a floating body 30 m in diameter. The water current receiving area of the screw, a circle with a radius of 35 m, is calculated as 3,846.5 m.
The output of the water turbine is calculated by W = (1/2) × ρAVC, where the parameters are given as follows:
ρ: Density (kg/m) (1,020 kg/m for seawater);
A: Water current receiving area (m);
V: Velocity (m/s);
C: Energy conversion efficiency.
When V = 1.4 m/s and C = 30%, W = 2,669.5 kW.
On the other hand, if the tip speed ratio of the water turbine is 1, the water turbine, whose circumference is 235.5 m, rotates at 168 rps. Accordingly, its angular velocity is 0.0374 rad/s.
Since the output of the water turbine is also expressed by W = (angular velocity) × (the torque of the generator), torque induced by the weight required for exceeding the reaction torque (load torque) of the generator is 7.14 × 10 N・m.
On the assumption that a weight, which is a water-filled tank 5 m in radius and 10 m in length (785 t of water), is present at a location 10 m away from the central shaft of the apparatus, the gravitational force caused only by the water will exert a torque of 7.69 × 10 N・m on the central shaft when the weight tank has risen to a location 90 degrees above. Therefore, this weight will be able to prevent the central shaft from being rotated by the torque induced by the generator.

  If you require more details, please contact us using the information below:

 Makoto Yasukagawa, Director of Morito Senai Hospital
 8-13 Hitokita-nishi, Moniwa, Taihaku Ward, Sendai City, Miyagi Prefecture
E-MAIL  rijityou@midorijuji.or.jp


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Renewable Energy Patents for Sale Makoto Yasukagawa.
8-13 Hitokita-nishi, Moniwa, Taihaku Ward, Sendai City, Miyagi Prefecture,〒982-0263,JAPAN
 TEL:+81-(0)22-281-0033 FAX:+81-(0)22-281-0585