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In fuel cell vehicles, hydrogen is stored in an on-vehicle high-pressure hydrogen tank; however, this tank must be filled with high-pressure hydrogen produced outside the vehicle. The present invention provides a unit capable of producing and storing high-pressure hydrogen through electrolysis of water inside the on-board high-pressure hydrogen tank. This unit enables high-pressure hydrogen to be refilled inexpensively by simply connecting the power supply and a water hose while a vehicle equipped with this unit is parked at home, thereby eliminating the need for refilling facilities such as hydrogen stations as well as reducing the cost of supplying high-pressure hydrogen.


A solid polymer electrolyte membrane is secured inside the high-pressure hydrogen tank to partition the tank’s internal space. An anode is connected to the membrane’s upper surface, while a cathode is connected to the bottom surface. In addition, a needle extending upward is secured to the center of the solid polymer electrolyte membrane, constituting a needle valve fitted into the funnel-shaped valve exit. Moreover, from outside the tank, tap water can be injected into the upper space partitioned by this membrane using a pump equipped with a check valve; wiring is connected to each electrode from the controller located outside the tank.
The piping connected to the fuel cell and the piping connected to the safety valve extends from the space below the membrane partition. The piping connected to the safety valve can also serve as a discharge pipe for discharging water that leaks out of the membrane and accumulates at the bottom of the tank.


When tap water is injected into the upper space and electricity is supplied to each electrode, oxygen gas is generated from the anode and hydrogen gas is generated from the cathode, both of which accumulate inside the tank. However, if the pressure in the upper space is higher than that in the lower space, the membrane is pushed down, putting the needle valve in the upper space in an open state; therefore, oxygen gas and tap water are released outside the tank. For this reason, only the pressure of the hydrogen gas in the lower space gradually increases, eventually pushing up the membrane and thereby forcing the needle valve to close. However, since the pump is injecting high-pressure tap water from outside, the needle valve will not close unless this pump is stopped, and, although the pressure in the upper space gradually increases, it will eventually become almost equal to that of the lower space as oxygen gas and tap water continue to be released outside the tank. Therefore, even though the membrane is thin, it will not rupture since the pressure on both sides can be maintained equally. Regarding the solid polymer electrolyte membrane to which the anode and cathode are joined, it is desirable that the membrane be folded many times in the vertical direction to increase the surface area as well as supported using a net or other means from below so that the weight of the water will not lower it excessively.
Further, a mechanism is provided that detects when the hydrogen gas pressure reaches a specified level and releases that gas from the safety valve at the bottom, activating the controller to stop the supply of electricity to each electrode. At this time, supply of power to the high-pressure pump is also cut off, stopping the injection of tap water. Due to this, when the high pressure of the hydrogen gas pushes the membrane upward, the needle valve closes. Since the pump is equipped with a check valve, the membrane will not rupture due to the difference in pressure caused by excessive discharging of water in the upper space.
The high-pressure hydrogen gas stored in the tank is sent to and used by the fuel cell as necessary, and the pressure in the tank gradually decreases. However, even if the needle valve reopens and air enters the upper space, it will not thereafter affect the unit’s operation, and the process of accumulation and use of hydrogen gas can be repeated. In addition, water that accumulates at the bottom of the tank is easily discharged from the discharge pipe connected to the safety valve by the hydrogen gas pressure when the safety valve is activated.

<Utilization as a means of transportation for generated energy>

If this unit is equipped with piping for transporting hydrogen gas to a high-pressure hydrogen tank rather than a fuel cell, an even greater amount of high-pressure hydrogen gas can be stored (in other words, since in this case discharging of hydrogen gas from the unit’s safety valve does not occur until the pressure of the other high-pressure hydrogen tank also reaches the same specified pressure, electricity continues to be supplied to each electrode, generating hydrogen gas).
In addition, when the pump injects tap water, a greater amount of water than is necessary for electrolysis is injected, preventing impurities contained in the tap water from concentrating within the unit, thereby enabling the unit to continue operating without the use of pure water. Moreover, tap water alternatives (e.g., river water) may be used if purified with a filter. Hydrogen can even be generated using seawater if a manganese-based composite oxide is used as the anode material to prevent chlorine generation caused by electrolysis.
Therefore, if cars or ships having hydrogen gas tanks equipped with this unit are used, power obtained via photovoltaic, wind force, or ocean current power generation as well as ocean thermal energy conversion in areas without power transmission infrastructures can be transported as high-pressure hydrogen gas, making it easier to secure locations to install power-generation equipment that makes use of such renewable energies.
The pressure of the discharged oxygen gas is as high as the pressure inside the space above the membrane; therefore, in large units performing continuous electrolysis of large amounts of water, it is possible to utilize this high-pressure oxygen gas to operate air turbines for power generation.

<Energy required to operate the unit>

The energy required for electrolysis of water, including the energy needed to compensate for endothermic reactions, is considered to be 279 kJ per mole. The energy required to operate the pump can be obtained by the following calculation: when generating high-pressure hydrogen gas at 700 atm (700 × 10Pa), one mole of hydrogen gas can be generated using 1 mole of water (18 × 10m). Assuming that 5 moles of water are injected at that pressure, since the necessary work equals the pressure multiplied by the change in volume, work W = 700 × 10Pa × 18 × 10m× 5 = 6300 J = 6.3 kJ.
Therefore, the number of moles of hydrogen necessary to generate 100 L of high-pressure hydrogen gas at 700 atm is 100 L/22.4 L × 700 = 3125 mol, and the energy necessary for generation is 3125 mol × (279 kJ + 6.3 kJ) ≈ 8.9 × 10kJ. Since 1 kWh = 3.6 × 10kJ, this corresponds to approximately 247 kWh.
In other words, if 1 kWh costs 15 yen, it costs approximately 3,710 yen to fill a 100 L tank (53yen per Nm).

  Patent Application : Japanese patent application No.2014-092426
  Patent        : Japanese patent No.5685748

   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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