Fluent material handling – with receiver or receiver coacting mea – Processes – Gas or variation of gaseous condition in receiver
Reexamination Certificate
2002-01-24
2003-11-25
Jacyna, J. Casimer (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Processes
Gas or variation of gaseous condition in receiver
C141S018000, C222S003000, C137S014000, C137S255000, C206S000700
Reexamination Certificate
active
06651701
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a hydrogen storage apparatus that supplies hydrogen to a fuel cell or other hydrogen-using devices, and to a method of charging hydrogen to the hydrogen storage apparatus.
On environmental considerations in recent years, attention is being given to a fuel cell electric vehicle (FCEV) in which carbon dioxide emissions causing global warming may be reduced. The fuel cell electric vehicle includes a fuel cell (FC) that triggers an electrochemical reaction of hydrogen (H
2
) with oxygen (O
2
) in the air, and electric power produced by the fuel cell is supplied to a traction motor to generate driving force.
Among apparatuses for supplying hydrogen to the fuel cell or other hydrogen-using devices, a hydrogen storage apparatus using a gastight pressure vessel containing a hydrogen occlusive alloy is very popular, which gastight pressure vessel will hereinafter be referred to as “MH tank”. The MH is an abbreviation for metal hydride. The hydrogen occlusive alloy is an alloy that may absorb (or occlude) a great mass of hydrogen (or hydrogen gas), and give out (or emit) the occluded hydrogen as necessary. The hydrogen occlusive alloy characteristically generates heat upon occlusion of hydrogen, raising a temperature thereof, and absorbs heat upon emission of hydrogen, lowering the temperature thereof. In addition, as shown in
FIG. 6
, an equilibrium hydrogen pressure in the hydrogen occlusive alloy characteristically increases with a rise in temperature of the hydrogen occlusive alloy (the phenomenon is called high-temperature shift), and lowers with a drop in temperature of the hydrogen occlusive alloy (the phenomenon is called low-temperature shift). To be more specific, upon occlusion, a rise in temperature of the hydrogen occlusive alloy would raise the equilibrium hydrogen pressure, and thus reduce the amount of hydrogen that can be occluded. On the other hand, upon emission, a drop in temperature of the hydrogen occlusive alloy would lower the equilibrium hydrogen pressure, and thus inhibit hydrogen occluded from being emitted sufficiently.
Accordingly, the hydrogen storage apparatus is configured to cool the MH tank upon occlusion of hydrogen to prevent a rise in temperature, and to heat the MH tank upon emission of hydrogen to prevent a drop in temperature.
However, for example, upon startup of the hydrogen-using device (esp. upon cold startup thereof) or on other occasions where no heat source may be available for heating the MH tank, hydrogen cannot be sufficiently emitted from the MH tank.
Therefore, the hydrogen storage apparatus usually incorporates an auxiliary tank capable of emitting hydrogen at a low temperature, or is otherwise configured to make up a shortfall.
For instance, Japanese Laid-Open Patent Application, Publication No. 5-106513 discloses a hydrogen supplying apparatus for a hydrogen engine including a normal-time hydrogen occlusive tank and a startup-time hydrogen occlusive tank. The startup-time hydrogen occlusive tank in the hydrogen supplying apparatus includes a hydrogen occlusive alloy capable of emitting hydrogen under low-temperature conditions without application of heat. Since an internal pressure of the startup-time hydrogen occlusive tank tends to build up, the startup-time hydrogen occlusive tank is made relatively compact to acquire resistance to pressure while restricting increase in weight. Upon startup under cold conditions, the hydrogen supplying apparatus supplies hydrogen from the startup-time hydrogen occlusive tank to start a hydrogen engine.
Japanese Laid-Open Patent Application. Publication No. 7-101255 discloses a hydrogen automobile including a main fuel tank filled with a hydrogen occlusive alloy, and a small-volume subordinate fuel tank. In this hydrogen automobile, hydrogen is supplied from the subordinate fuel tank to an engine thereof upon startup. The subordinate fuel tank may be charged with hydrogen from the main fuel tank on some occasions. The subordinate fuel tank may be filled with a hydrogen occlusive alloy in some instances.
Japanese Laid-Open Patent Application, Publication No. 9-142803 discloses a hydrogen supplying apparatus in which a gas tank is coupled with a gas vent of a hydrogen occlusive alloy tank filled with a hydrogen occlusive alloy via a check valve, and a hydrogen feed pipe for feeding hydrogen to an external device (i.e., fuel cell) is coupled with a gas exhaust vent of the gas tank. This hydrogen supplying apparatus has the gas tank provided between the hydrogen occlusive alloy tank and the fuel cell, and is configured to supply hydrogen from the gas tank to the fuel cell upon startup by utilizing sufficiently high pressure (approximately 0.9 MPa) kept by the check valve in the gas tank. On the contrary, when the temperature of gas emitted from the fuel cell itself rises after startup, the internal pressure of the hydrogen occlusive alloy tank builds up, so that hydrogen is supplied from the hydrogen occlusive alloy tank by the action of the check valve.
Japanese Laid-Open Patent Application, Publication No. 2000-12062 discloses a hydrogen supplying apparatus including a main hydrogen storage tank accommodating a higher-temperature hydrogen occlusive alloy that may emit hydrogen under conditions of predetermined higher temperature, and a subordinate hydrogen storage tank accommodating a lower-temperature hydrogen occlusive alloy that may emit hydrogen under conditions of lower temperature below the predetermined higher temperature, and the like. This hydrogen supplying apparatus supplies hydrogen from the subordinate hydrogen storage tank to an external load (i.e. fuel cell) upon startup when the internal pressure of the main hydrogen storage tank is low, and starts supplying hydrogen from the main hydrogen storage tank to the external load some time after startup when the internal pressure of the main hydrogen storage tank gets higher.
However, the above-cited prior arts, which might possibly clear up difficulties in supplying hydrogen during startup, could not overcome disadvantages in weight. To be more specific, the MH tank accommodating (or filled with) a hydrogen occlusive alloy is compact in size, but heavy in weight, and thus would disadvantageously entail poor fuel efficiency when installed for example in a fuel cell electric vehicle. In addition, the heavy weight would disadvantageously make it difficult to handle the apparatus. Accordingly, weight reduction is critical. On the other hand, reduced amount of storable hydrogen that might take place due to the weight reduction would yield unfavorable results, eg., shorten a distance the fuel cell electrical vehicle may travel.
Moreover, heat generated upon occlusion of hydrogen in the MH tank would slow down a hydrogen charging speed (occlusion speed) of the hydrogen storage apparatus. This would disadvantageously result in longer hydrogen charging time.
Therefore, it is an object of the present invention to provide a hydrogen storage apparatus and hydrogen charging method in which the above-described disadvantages may be eliminated, and more specifically to provide a hydrogen storage apparatus fit to install in a vehicle.
SUMMARY OF THE INVENTION
In order to achieve the above object, the present inventors have discovered as a result of their thorough study that a hybrid system formed by combining a hydrogen storage means accommodating a hydrogen occlusive alloy, and a hydrogen tank containing hydrogen in gaseous form, each of which is configured to have an internal pressure set appropriately, may work with the above disadvantages surmounted, and consequently have brought the invention to perfection.
A method of charging hydrogen to a hydrogen storage apparatus (in claim 1) as one exemplified aspect of the present invention, in which the above-described disadvantages are eliminated, comprises the steps of filling hydrogen to a hydrogen storage means provided in the hydrogen storage apparatus to accommodate a hydrogen occlusive alloy, and filling hydrogen to a hydrogen tank provided in the
Kuriiwa Takahiro
Nuiya Yoshio
Shimada Toshiaki
Honda Giken Kogyo Kabushiki Kaisha
Jacyna J. Casimer
Lahive & Cockfield LLP
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