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Ocean Thermal Energy Conversion/Wave Power Electricity Generation Vessel  


With the "Dual Purpose Vessel for Wave-Activated Power Generation and Energy Transportation", it is necessary to use a heavy plate weight and energy collection is difficult in countries and regions with no deep sea.  A wave power electricity generation vessel that can overcome these drawbacks by carrying energy generated by wave power by a "high-pressure hydrogen generation unit" in the form of hydrogen gas and generate more electricity by incorporation of an ocean thermal energy conversion system is provided.

<Summary of the wave power electricity generation unit>

In this wave power electricity generation vessel, as with “Dual Purpose Vessel for Wave-Activated Power Generation and Energy Transportation”, a bottom plate is dropped from the vessel; however, the bottom plate is hollow and thus so light as to have a specific gravity of around one in the sea.  However, the bottom plate fixed to the vessel via four columns is subject to the resistance of water not only on the side where the vessel is raised by wave but also on the side where the vessel is depressed by wave, enabling the vessel to rarely pitch even with wave of a long wavelength.  The parts of the columns connected to the vessel body can pivot and when the vessel comes alongside the pier of the port, the shafts of such parts are rotated to lay the respective columns rearward to lift the bottom plate up to the bottom of the vessel.
Inside the vessel, multiple baths are horizontally arranged, and on the bottom of each bath, a hydraulic turbine is installed.

<Effects of wave power electricity generation unit>

Since the bottom plate has a large area, installment of the bottom plate at a depth of around 50 to 60 m from the bottom of the vessel enables the vessel to be prevented by the resistance of water from pitching of the vessel body even with wave of a long wavelength.  Accordingly, water level up/down fluctuations caused by wave make seawater go into/out of the baths to generate electricity.  Here, an electricity output where each bath has a cylindrical shape with a diameter of 15 m and the average wave height is 3 m will be estimated.  The wave cycle is eight seconds and during that period, the water surface in a bath repeats vertical movement of three meters.  In eight seconds, 529.8 t of seawater goes in and out of a bath and rotates the hydraulic turbine, and if it is contemplated that the turbine is rotated only when the water reaches the maximum water level and the minimum water level, the seawater in the bath has an average height of 1.5 m, and the corresponding potential energy would be supplied to the hydraulic turbine.  Therefore, since E = mgh, E = 529.8 t ´ 9.8 ´ 1.5 m = 7788 kJ, and thus, an electricity output per second is 973.5 kW.  Accordingly, the electricity output of a vessel having twenty such baths is 19470 kW, and if the electricity generation efficiency is 80 percent, electricity of 15576 kW can be obtained.

<Effects of centrifugal high-pressure hydrogen generation unit (apparatus for which a patent is sought>

In the high-pressure hydrogen generation unit, a cathode and an anode are connected to opposite surfaces of a solid polymer electrolyte membrane in an electrolysis cell so as to be integrated with the membrane, enabling hydrogen gas to be generated on the cathode side by supply of water on the anode side.  In that case, the hydrogen gas can be separated from water by the solid polymer electrolyte membrane, and thus, can be stored in a high-pressure hydrogen gas tank without dissolving in supplied water.  In addition, during operation, the rotation speed of the unit is adjusted so that the same degree of water pressure and air pressure is applied on each of the opposite surfaces of the electrolyte membrane, enabling high-pressure hydrogen gas to be easily produced without breaking the membrane.  Even if seawater is used for the supplied water, oxygen gas can be generated if an manganese-contained composite oxide is used for the anode, and a flow of seawater can be generated by the buoyancy of the oxygen gas from the electrolysis cell section in the outer periphery of the rotating unit toward the center tube as with an air lift pump (You Tube: Ceramic Diffuser used in a Water Tank).  Thus, the flow of seawater enables not only preventing seawater in the unit from being frozen as a result of endothermic reaction caused by electrolysis, but also pumping up deep-sea water by means of the submersible pump function of the unit and jetting the flow of seawater to the rearward of the vessel to obtain propulsion.

<Calculation of propulsion>

The centrifugal force generated by the rotation of the unit makes the buoyancy of the oxygen gas be exerted in the seawater in the pipe, and the oxygen gas moves toward the center of the rotation with the seawater while expanding and is discharged upward from the cylindrical section in the center, and the seawater is jetted in the form of a water flow to the rearward of the vessel from the bottom of the vessel.  The centrifugal force applied to the seawater in the pipe is proportional to the square of the distance from the center of the rotation, and the buoyancy can be calculated from the difference in water pressure exerted on the air bubbles.  Since the value of the work of the buoyancy of the oxygen gas for the seawater can be obtained by integrating the buoyancy of each part from the center of the rotation to the electrode part, and thus, if the value is calculated assuming that the radius of the rotation of the unit is 10 m and the angular velocity is 40 radians/sec, the value amounts to approximately 5 kJ in the case of 0.5 mol of oxygen gas (for the details of the calculation, please inquire at the point of contact).  Accordingly, the propulsion of water flow generated by electrolysis of 1 mol of water per second is approximately 5 kW.  In other words, in the case of an average wave height of 3 m, electricity of 15576 kw can be generated, and thus, 55.8 mol of water can be electrolyzed per second, and the propulsion of 279 kw can thereby be obtained.  This propulsion means that the vessel can be moved one meter per second by a force of 279 t.  Therefore, since it is estimated that the wind speed is 10 m/sec when the wave height is 3 m, the force received by a vessel with a cross-section of 30 ´ 50 m from the wind is 750kg based on 0.5kg/m where the wind-force coefficient is 1.0, and thus, the vessel can be propelled against the wind.  Therefore, even if a hose is dropped into deep sea and an off-shore windmill is installed on the vessel, electricity generation can be continued at a fixed position without the vessel being driven by the wind.  Furthermore, directing jet nozzles downward or rightward/leftward enables adjustment of the speed and change in direction of the vessel, and thus, contributes to the vessel handling (however, when the vessel changes its position, the hose is wound up, and propulsion is obtained by pumping up water at the sea surface, and thus, ocean thermal energy conversion cannot be performed).

<Ocean thermal energy conversion>

In this unit, it is possible to drop a hose to deep sea around 1000 m deep from a seawater intake, pump up a huge amount of cold seawater by means of submersible pump action caused by generation of water flow as described above, further cool the seawater by means of endothermic reaction caused by electrolysis, and then guide the seawater to the rear of the vessel via piping for jetting.  Therefore, if an ammonia gas pipe is put around the piping, the piping can serve as a heat exchanger that cools and condenses ammonia gas, and the ammonia is gasified using the baths for wave power electricity generation as a heat exchanger, and electricity is generated by a gas turbine using the gas.  Also, in the electrolysis cell of the unit and the wave power electricity generation baths, electrolysis for generation of chlorine is also made to occur to generate sodium hypochlorite for seawater disinfection, enabling prevention of biofouling, and thus enabling prevention of failure of the hydraulic turbines and the heat exchangers.
The ocean thermal energy conversion system eliminates not only the need for a pump for pumping up seawater from deep sea but also the need for a pump for circulating seawater in the heat exchangers, enabling more efficient electricity generation compared to the conventional ocean thermal energy conversion systems.



As described above, upon wave power electricity generation in a sea area with an average of wave height of 3 m, the wave power electricity generation vessel can store energy of 15,576 kW in its tank in the form of high-pressure hydrogen gas and carry the energy to a port.  Assuming that the annual operating rate of the vessel is 90% and electricity is generated by, e.g., fuel cells using the hydrogen gas at an electricity generation efficiency of 50%, electricity of 15576 ´ 0.9 ´ 0.5 » 7000 kW can be obtained.  If the electricity is sold for 23 yen/kwh, an annual revenue of approximately 1.4 billion yen can be obtained.  Furthermore, if a part of the hydrogen gas is charged in a vehicle tank in the form of high-pressure hydrogen, the cost for compression of the gas can be saved (a hydrogen gas stored tank with a radius of 15 m, a length of 100 m and 700 atmospheres enables rapid charge of the gas in a vehicle tank of 70,000 m with 350 atmospheres. Furthermore, more revenues can be expected in combination with ocean thermal energy conversion.
  Assuming that the amortization period of the unit is five years, annual maintenance and personnel costs amount to 100 million yen and the unit and the vessel can operate by means of ocean wind power electricity generation and propulsion provided by the buoyancy of oxygen gas bubbles, the costs for five years amount to 500 million yen, and thus, if this vessel can be manufactured at a cost of 1.4 billion yen ´ 500 million yen - 500 million yen = 6.5 billion yen or less, the vessel pays for itself only with revenues for electricity from wave power electricity generation.

  Patent Application : Japanese patent application No.2013-097253
  Patent        : Japanese patent No.5347080

  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.
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