The disadvantage of a total metal hydride system is
HYDROGEN SUPPLY METHOD that the system is both heavy and expensive. The
weight problem becomes critical in mobile applications
BACKGROUND OF THE INVENTION such as automobiles, buses, etc., wherein transportation
This invention pertains to a system for supplying 5 of *e added wei8ht reduces the Juel economy of the
hydrogen to a hydrogen utilizing apparatus utilizing a vehlcle- In stationary system such as systems utilizing
combination of a metal hydride hydrogen storage and hydrogen in the generation of electricity, weight of the
microcavity hydrogen storage. svstem is not the cnt,cal factor however, in these sys
Because from an environmental standpoint hydrogen tems wherein large quantities of metal hydrides will be
can be cleanly used, because hydrogen has a large ca- 10 required the economics of the system become critical,
pacity for energy transference, and because there is a An additional factor to be considered in mobile sys
reversible supply of hydrogen in the form of water, the tems such as automobile usage of metal hydride systems
utilization of hydrogen as a fuel for many different is the refueling (i.e. regenerating the metal hydride) of
systems is becoming incresingly important. Hydrogen the on board metal hydride vehicle storage tank. Dur
can be used as a fuel in apparatuses which are powered in8 refueling the vehicle storage tank would have to be
by combustion engines wherein hydrogen is oxidized coupled to a unit which withdrew heat from the storage
and the energy obtained in this oxidation process is used tank allowing for the regeneration of the metal hydride,
to power the engine with the only product of oxidation This would require at complex hookup of hydrogen
being water. Additionally hydrogen can be used as a ,„ supply line and cooling line. Compared to the typically
fuel for electrical energy generation utilizing either the five minute stop now necessary to obtain a supply of
heat of combustion to drive conventional steam turbines gasoline, the regeneration of the metal hydride could
or direct use of hydrogen within fuel cells. require a prolonged fuel stop.
At all temperatures except cryogenic temperatures BRIEF SUMMARY OF THE INVENTION
hydrogen exists as a gas. The storage of large supplies of 25
hydrogen as a gas presently is done by compressing the In view of the above it is evident that there is a need hydrogen and storing in large tanks. However, because for new and improved systems which supply hydrogen the hydrogen is under high pressure it is necessary that to an apparatus utilizing hydrogen as a fuel. It is therethese tanks to very strong which in turn necessitates fore a broad object of this invention to fulfill this need, very thick walls and heavy tanks. When hydrogen is 30 It is a further object of this invention to provide a hystored as a liquid at cryogenic temperatures, as with drogen supply system which is not as expensive as an hydrogen as a gas, cryogenic liquid hydrogen must also exclusively metal hydride hydrogen system. Additionbe contained in strong, heavy tanks and additionally ally it is an object of this invention to furnish a system there is an energy penalty in the liquefaction process. which has a hydrogen capacity similar to that of liquid Aside from the weight disadvantages of hydrogen stor- 35 hydrogen yet does not involve the dangerous usage of age in tanks both as a liquid and a gas, the storage tank large quantities of either liquid or gaseous hydrogen, must be designed and constructed of suitable materials Additional objects include a hydrogen supply system to accommodate and control the permeability and reac- which will deliver hydrogen at greater than atmotivity of hydrogen with most metals. spheric pressure to the apparatus which will use the
It has been proposed to store hydrogen chemically 40 hydrogen yet does not require equilibrium storage presbound in a chemical carrier such as methylcyclohexane sures greater than approximately 50 or 60 atm. which is catalytically converted to toluene and hydro- These and other objects are fulfilled by providing a gen, the hydrogen being used as fuel and the toluene hydrogen supply system which utilizes a metal hydride being recycled back to methylcyclohexane. Use of such hydrogen supply component and a microcavity hydroa system requires two transporation networks, one for 45 gen storage hydrogen supply component both compothe delivery of the methylcyclohexane to a service nents supplying hydrogen to an apparatus using hydrostation for dispensing to the consumer, the other for the gen and additionally the microcavity hydrogen storage return of the toluene to a reconversion plant to be hy- hydrogen supply component supplying hydrogen to drogenated into methylcyclohexane. This type of sys- recharge the metal hydride hydrogen supply compotem is still in a semihypothetical state and much technol- 50 nent and the system incorporates the metal hydride ogy remains to be developed until each systems can hydrogen supply component including a storage tank hope to be functional. filled with a composition including a metal capable of
A system now being field tested for utilizing hydro- forming a metal hydride and having a heat exchanger to gen as a fuel to propel an automobile involves the use of regulate the temperature of the metal hydride to control a metal hydride as the carrier for the hydrogen fuel. 55 absorption/deabsorption of hydrogen from the hydride Basically this system involves having a storage tank and the microcavity hydrogen storage hydrogen supply filled with a metal that reversibly forms a metal hy- component includes a storage tank containing a midride. In the presence of hydrogen and the withdrawal crocavity hydrogen storage and a heating element for of heat, the metal absorbs the hydrogen forming a metal heating the microcavity hydrogen storage to release hydride. Upon the application of heat the hydride disas- 60 hydrogen from the microcavity hydrogen storage and sociates into the metal and hydrogen allowing the hy- further having regulating valves within the system to drogen to be utilized as fuel. The heat to disassociate the regulate the flow of hydrogen from both the metal metal hydride is obtained from the hot exhaust gases hydride hydrogen supply component and the mifrom the engine. Currently two metal hydride systems crocavity hydrogen storage hydrogen supply compoare being studied for use in automobiles. One system is 65 nent to the hydrogen utilizing apparatus and the flow of based upon a hydride of an iron titanium alloy and the hydrogen from the microcavity hydrogen storage hysecond system is based upon hydrides of magnesium drogen supply component to the metal hydride hydroalloys, gen supply component.
