WO2003002451A1

WO2003002451A1 - Method for storing hydrogen in a hybrid form

Info

Publication number: WO2003002451A1
Application number: PCT/CA2002/000998
Authority: WO
Inventors: Robert Schulz; Guoxian Liang; Jacques Huot; Patrick Larochelle
Original assignee: Hera Hydrogen Storage Systems Inc
Current assignee: Hera Hydrogen Storage Systems Inc
Priority date: 2001-06-29
Filing date: 2002-06-28
Publication date: 2003-01-09
Anticipated expiration: 2003-12-29
Also published as: JP2004530628A; BR0210764A; MXPA03011759A; US20030042008A1; RU2004101771A; EP1404611A1; KR20040012993A; CA2452067A1; CN1522224A

Abstract

A method for storing hydrogen which combines the advantages of at least two known methods for storing hydrogen, selected amongst the methods for storing hydrogen in a gaseous form, in a liquid form and in a solid form. More specifically, the above method consists in coupling and using in a single tank at least two of the methods for storing hydrogen mentioned hereinabove, namely: A) the method for storing hydrogen in a gaseous form; B) the method for storing hydrogen in a liquid form; and C) the method for storing hydrogen in a solid form, in volume or surface, preferably by means of a suitable hybride. The only condition is that each of the above methods be used for storing at least 5% by weight of the total amount of hydrogen to be stored within a tank. Such a method permits to obtain fast release of hydrogen whenever required while ensuring high storage capacities. It also permits to satisfy transitory periods especially during the accelerations of a hydrogen-powered automotive vehicle.

Description

METHOD rOK S I KING HYDROGEN IN A HYBRID FORM

FIELD OF THE INVENTION

The present iπventiσn-relates to a method for storing hydrogen in a hybrid form. More specifically, it relates to a method for storing hydrogen in two different forms within a siπgle tank.

The inventiσn-also-relates to^'tanks hereinafter called "hybrid tanks", which are specially adapteτJ fσrcarryiπgOut the aboveτπetbσd when the hydrogen is stored in liquid and solid forms-and when the hydrogen is stored in solid and gaseous forms, respectively.

BRIEF DESCRIPTION OFTHE PRIOR ART

Methods for storing hydrogen can be classified in three main categories :

(A) gaseous storage in high-pressure tanks ;

(B) liquid storage in cryogenic tanks ; and

(C) solid storage irrtanks cOπtainirιy rτιaterialsthatabsorb (in volume) or adsorb (on surface) hydrogen.

The last category listed above as category (C) is the one that makes use of metal hydride storage tanks. Each of the abOvexategories-has advaπtages and disadvantages that are summarized in the following Table I :

TABLE I Characteristics of the different methods for storing hydrogen

Byway of example, inthe case of a methσd forstoring hydrogen in a gaseous form (category A), a tank of one (1) liter will contain the following amounts of hydrogen at the various-pressures indicated in Table II :

TABLE II

Gaseous storage

In the case of a method for- storing hydrogen in a liquid form (category B), a tank σ σπe (1 ) liter will contain 0.0708 kg of hydrogen siπce the l o density of liquid hydrogen at -252.8°C (that is at the cσπventional boiling point of hydrogen) is equal to 0.0708 kg/I.

Last of all, iπ the case ofaTiielliud forstoring hydrogen in a solid form with a metal hydride (category C), a tank of one (1 ) liter containing a hydride of formula AB5 like LaNisHβ (density: 6.59 kg/I, hydrogen storage

15 capacity ~ 1.4%) occupyrng all the volume of the tank, will contain 0.0923 kg of hydrogen, that is almost twicethe^arrrount σf hydrogen stored in a gaseous form in a tank of one literat 15,000 psig.

The results ofthis-comparative-example are given in Table III : TABLE III

f the-stoiaye capacityof the-thm basic methods f or storing-hydrogen

Of course, in the case of the method for storing hydrogen in a liquid form (category B), there-is^:always som yaseous hydrogen in equilibrium with the liquid because-of-some^revapuration of the latter. Also, in the case of the method forstoring hydrogen in a solid form with a metal hydride (category C) typically opeτatiπg at low pressure (10 bar), there is some gaseous hydrogen because the hydride πeveroccupies all the space in the tank. Moreover, in the case of the method for- storing hydrogen in a gaseous form at a very high pressure (category A), there is always-some hydrogen that is adsorbed (such adsorbed hydrogen is also called "solid hydrogen" according to the above terminology) σntσtheϊπlernal wallsof the tank. Therefore, in each rrtethod listed hereiπabove (gaseous, liquid and solid), there is always a small amount of hydrogen that is stσred accσrdirrg-to another method of storage.

By way σf-example, oriemay evaluate-therrraximum-percentage of hydrogen that may come from-arrothermethod of storage in the case of a tank of one liter containing a metal hydride powder (LaNisHβ). Assuming that the powder is not compacted and, therefore, occupies about half of the volume of the tank, that is about half a liter, cσrrsidering alsσthat the density of LaNisHs is equal to 6.59 kg/I and furtherassuming that the gaseous hydrogen within the tank (about half a liter) is at a pressure 10 bar, the amσuπt of hydrogen that is not solid within the taπk of σne literwill be as-reported in Table IV:

TABLE IV

This example clearly shows that forany given method of storage, there can usually be 1% of -hydrogen-stored in a different form. However, in all cases, this amount/will always be lowerthan 5% by weight.

It has already been suggested that there could be some advantages in coupling different-means forstoring hydrogen within a single category.

By way of example, U.S. patent No. 5,906,792 entitled "Nanocrystalliπe coTTηrosite-forhydrogen storage" in the πame of the Applicant and the McGill University, discloses that there are advantages when one combines within a same tank a low temperature metal hydride with a high temperalure metal hydride- in contact with each other. When such a mixture is used for an internal combustion engine, the low temperature metal hydride allows cold starting of the-engine by providing the hydrogen at the start up. When the engine is hot, the heat that is generated by the same permits to inducethe desorption of hydrogen from the higlTtemperature-rπetal hydride (see column 3 of this U.S. patent No. 5,906,792 fσrmσre details).

Similarly, international laid-σpen patent application No. WO 01/16021 published on March 8, 2001 in the name of David G. SNOW et al, discloses that there are some advantages in combining solid storage in the volume (absorption) with solid storage on the surface (adsorption) in nanoparticles of a hydride in order to improve, inter alia, the hydrogen absorption and desorption kinetics.

U.S. patent No. 5,872,074 entitled <c Leached naπocrystalline materials, process for manufacture the same aπd use thereof in the energetic field" in the name of the Applicant, also discloses that the hydrogen sorption kinetics can be irπproved when-use isτnade of a hydride having high specific surface.

Independently of the above, it is also known that the method (C) for storing hydrogen in a solid form usually has a response time (loading and unloading) much-slowerthan theτπethod (A) forstoring hydrogen in a gaseous form and slowerthaττ the method (B) for storing hydrogen in a liquid form. Actually, at least 15 rrrirrutes-and sometiiiies iiiure than 1 hourare required to fill up a hydride storage tank. In spite of this drawback, the method for storing hydrogen in a solid forπrr hasihe- highest capacity of storage per volume unit (see again Table III heretrrabove).

It is kπowπ-that some technical applications require a response time much fasterthan untrminute.

Thus, for example, in UPS systems (uninterruptible powersupply) using fuel cells fed with hydrogen, a response time of about one hundred milliseconds is usually-required. Of course, a hydrσgerrstoring tank using metal hydride-rarnTot-satisfythis-rjarticularrequirement. However, in such a case, use could be made of a tank in which hydrogen is stored in a gaseous form at high pressure.

Similarly, in hydrogen-operated vefricles, there are-different types of transitory-periods, like : short duration accelerations (second) which usually require a response time of abσurσne hundred nillisecond frσπrthe propulsion system; and power increases wherrthe vehicle is climbing up a hill, which may last a few minutes.

In hybrid vehicles which make use of a fuel cell and batteries, the very short accelerations (second) can be taken care by the batteries whereas thetraTTsitory periods-ofa lαngerduration (a-fewτπτrιutes) may require hydrogen stored in a gaseous-form. On the other hand, the average powerwhich is of about 20 KW for a typical vehicle, may easily be accomodated by a metal hydride tank. The energy contained in the batteries of such a vehicle usually represents about 1 % of the^energy on board. Therefore, one-needs an amount of hydrogen higherthan 1% to take charge- of -the traπsitory periods.

To sump up, in view of the above, it is obvious that there is presently a majσrτιeBd-fora-ιτrethrjd-forsto combine the advantages of the-differentτ i lethυds listed hereinabove.

5

OBJECT AND SUMMARY OFTHE^'INVENTION

An object of the present invention is to satisfy the above mentioned need by providing a new method for storing hydrogen which combines the advaπtages of at least two ofthe above-mentioned methods for o storing hydrogen, namely the-inethσds-forstoriπg-hydrogen in a gaseous form, in a liquid fσrπrarrd in a solid form.

The present invention basically-consists in coupliπgaπd using in a singletank hereinafter called « hybrid tankfor storing hydrogen » at least two of the methods foi sloriMg-hydrogerrmentioπed hereiπabove, namely : 5 A) the-method-forstoriπg- hydrogen in a gaseous form ;

B) the method forstoring hydrogen in a liquid form ; and

C) the method forstorirrg hydrogen in a solid form, in volume or on surface.

The only condition- is that each-σf the above methods is used for o storing at least 5% by weight of the total amount-of hydrogen- within the tank.

Therefore, the invention as claimed is directed to a method for storing hydrogen-in-arι-hybrid-foτm, which omprises the step of coupling and using within a single tank at least two hydrogen storage rneans selected from the group consisting of : 5 a) means forstoriπg-hydrogen in a gaseous form ; b) meaπs-forstoring-hydrogen iπ a liquid form ; and c) means forstoring hydrogen in a solid form by absorption or adsorption, with the proviso that each of the storing means that are used, is o sized to store at least 5% by weight of the total amount of hydrogen stored within the tank. The means mentioned hereinabσve for storing hydrogen in different forms are those comrπonly used fσrcarryiπg out each of the above mentioned methods. They are very conventional and need not be further described in detail. The-onlyτequiremenf isthatthey beooupled within the same 5 tank in σrderto be-used-stmultaneously for-each storing at least 5% by weight of the hydrogen.

ArrotherObjectOftrre-present invention is to provide a hybrid tank for storing hydrogen- in- both liquid and solid -forms, comprising two concentric containers, one of the containers hereiπaftercalled "inner" container is located l o within the other one whichϊs hereinafter called "outer container", the containers being separated by an iπsulating-sleeve fσr-rrrairrtaiπiπg the inrrer container at low temperature. The irtnercσntaiπeris used forstoring hydrogen in a liquid form. The outer cϋntaiπeris-in-directOorrrmuπicatiorrwitfrthe inner container and contains a metal hydrrde-for-storirrg-hydrogen in a solid form.

15 A furtherobjectOf the present invention is to provide a hybrid tank for storing hydrogerrin-both-solid and gaseous-forms, comprising:

- a cσntaiπerhaviπg a-metallic liner or inner wall covered with a polymeric outer-shell, said-containerbeing-devised tσstore hydrogen in gaseous form at a higherpressure-and to-reτjeive-aπd-stσre a metal hydride in order to

20 store hydrogen in solid form;

- at least one heat-pipe mounted within the container to allow circulation of a heat carryiπg fluid; and

- a heat exchangerlocated within the contaiπer in σrderto ensure thermal conπeclion between said at least-one heat pipe and the hydride. 5

BRIEFTJESCRIPTION UFTHETJRAWINGS

The invention and the way it can be reduced to practice will be better understood upon reading-the-following-πσn-limitative examples given with reference to the accompanying-drawings in which : 0 Figure 1 is a diagram illustrating the equilibrium plateau of the hydride used in a hybrid gas-solid storage-tank disclosed in example 1 ; Figure 2 is a schematic cross-sectional view of the hybrid liquid- solid storage tank disclosed in example 2 ;

Figure 3 is a diagram illustratfπg-the equilibrium plateau of the hydride used in the hybrid gas-solid -storage-tank disclosed in example 3 ;

Figure 4 is a schematic-crσss-sectiσπal view of the hybrid gas-solid storage tank disclosed in example 3; and

Figures 5 and 6 are diagrams givrng the equilibrium plateaux of several hydrides as^:afurrrtron of thetemperature-aπd indicating which one could be used in the hybrid gas^solid-storage tank disclosed in examples 1 and 3.

EXAMPLE 1 : Hybrid-sluiaye laiik for stoting iiydroy n in gas and solid forms

A hydrogerrstoragetank-having-a-volume of 1 liter has beerrfilled up with a powderof πaπoparticles of a hydride of LaNis having an average diameter of 5 nanometers. The powderσccupied 50% by volume of the tank, that is 0.5 liter, siπce it was πot-coTrrpacted. Thenumperσf atσrrrsσn-the surface of these naπσpartrcles-represeπted about 28% of the total amount of atoms within each partrcle considering a layerof 0.4 to 0.5 nanometerσn the surface of each nanσparticle. The-tank has-then been-filled up with gaseous hydrogen at differeπl μressures-raπging-from 10 bar (typical pressure of use of the metal hydride tanks) to 700 bars (typical pressure used in high pressure gaseous tanks). It was assumed that the arrrount of hydrogen in the volume and at the surface of the metal hydride coTresponded to H/M=1 (H = hydrogen, M = metal), which is typical to most-metal hydrides. Uπderthese conditions, the amounts of hydrogen associated tothetwo diffeient means of storage that were used, have been calculated and are reported in Table V hereinafter :

TABLE V

It is worth πoting-that in the first case reported in Table V, that is when the pressure is of 150 psi (10 bar), the amount of hydrogen in gaseous phase represented about 1 % of the total amount. This example is illustrative of what is-presentlyObtafπed in conventional metal hydride taπks-and is therefore outside the scope ofthe- present-invention. However, in the three othercases reported hereiπabσve where the pressures were of 3,600 psi, 5,000 psi and 10,000 psi, thearrrourrts-ofhydrogerrirrgaseous-phase-represerited about 15%, 19% and 28% respectively of thetotal amount-of hydrogerrwithrn the-tank. Such is much higherthan the limit of 5% as indicated hereiπabove.

The tank disclosedϊn example 1 is illustrative σfa tankthat can be used in a "back up" system based on a fuel cell or a hydrogen source generator. In the case of a failure of the electric supply, the hydrogen in the gaseous phase will irritially supply the fuel cell orthe generator that will slowly warm up. The pressure within the tank will be reduced. When the pressure reaches the equilibrium plateau of the hydride, that is about 2 bars for a AB₅ alloy at room temperature, there will be almost no more hydrogen in the gaseous phase. Then, the hydride will take over by providing hydrogen to the system thanks to he heat-generated by the fuel cell or the generator.

It is wortlrnoting that, in this example, the equilibrium plateau of LaNiδ which is a conventional low temperature metal hydride at the operating temperature (typicallyτanging between 0 to 100°C), is slightly higherthan the pressure of hydrυgei 1 i equired a the-inletOftherfuel cell, which typically about 2 bars. If the tank contains 50% by volume of hydride and the balance is occupied 5 with gaseous hydrogen at 690 bars (10,000 psi), the situation will correspond to that ofthe diagram-given in Figure 1.

Uπder such a circumstance, duriπg σperatiσn ofthe system, the hydrogen will come frrsrfrom the-gaseous phase. Then, when the amount of hydrogen and the gas pressure become low, the hydride will take over by l o providing hydrogerrtσthe system. The-pressurewitrrirrthe tank will then be kept at the level oft e desυiμliuirplateau of the hydride. The kinetics of the system will therefore be quite high at the beginning (response time of the gaseous system) and there fter low (respuπse time-of the hydride system).

There are also other-advantages in using such a hybrid method

15 combining gas and"solid storage. In-particular, one can-mention : a) refilliπg upOf thσtaπk is carriedOut in a shσrt trme as compared to conventional metal hydride tanks ; b) the design of the heat transfer components of the tank is simplified ; and 0 c) the high storage capacity by-volume of the metal hydride and the high capacity of sloi age by weight of thenew cor i iμosite high-pressure gas storage tanks are-combined.

EXAMPLE 2 : Hybrid-taπk for storing-hydrogen in liquid and solid forms 5

A hybrid-tank 1 for storing hydrogen-having a total volume of one liter has been devised from two corrcerrtric-containers 3,5 (see Fig.2). The inner container 3 had a volume of 0.8 literwhereas the outer container 5 had a volume of 0.2 liter. Arriπsulating:sleeve 7 was-pσsitiσπed betweerrthe inner and o the outercontainers 3,5 to keep the irrπer cσntaiπer 3 at low temperature.

In use, the iππercontainer 3 of the tank 1 was filled up with liquid hydrogen. It contained about 0.0708 kg/I x 0.8 liter= 0.0566 kg of hydrogen. The outer container 5 was-filled with aτJθwderOf ametal hydride ofthe type LaNi₅He which occupied about 50% ofthe volume, that is about 0.1 liter. Therefore, the outeroontairrer 5 contained 6.59 kg/I x 0.1 liter x 1.4% = 0.0092 kg of hydrogen. The total amount-of hydrogen-stored within trie-tank 1 was equal to 0.0658 kg (14% in the outertank and 86% in the innertank).

As comparedtoa conventioπal tank for storing hydrogen in a liquid form, the tank disclosed in-example 2 has the advantage of having no loss of hydrogen overa-rjeriσd thatmay exceed two-weeks. Indeed, the problem with any conventional liquid-hydrogen-storage tank is that the hydrogen evaporates (boil off). Up to 1% of the amount of liquid hydrogen can evaporate each day from a conventional tank (1% x 0.0566 kg = 0.0006 kg/day). In the hybrid tank disclosed in example 2, the rjoil-erffhydrσgen-is absoibed by themetal hydride that extends in peripheryof theϊππercontaiπeraπd up to itsmaximum capacity (that is 0.0092 kg/0.0006 kg/day = 15 days). It is worth noting that the idea of using metal hydrides for

"catching" evaporated rrydrogen-from a liquid rrydrogerrstorage tank has already been suggested, but by means of two separate systems that must be interrelated, connected and independently controlled. In this regard, one can refer to U.S. patent No.5,728,483 to SANYO ELECTRIC CO. In contrast, in the present invention, these two-different mea s for slυring-hydrogeπ are combined within a single tank-and therefore-operate in a simplerrrraπner.

EXAMPLE 3 : Hybrtd'tank forstoTrng-hydrogeii in gas-solid form foT'iise- in a-systein haviny transitory-periods

In the tank disclosed in example 1 , use was made of LaNisHe as the hydride. This compound is known to have a low equilibrium plateau (viz. lower than 40 bar) at operating-temperature. Use could also have been made of other hydride with a low equilibrium plateau, such as NaAIH₄, LiAIH or MgH₂. According to the invention, it is however-possible to use also a hydride having an equilibrium plateau that is much higher at the operating temperature (typically ranging between 0° and 100°C) than the equilibrium plateau of the conventional hydrides (typically-ranging between 1 to 10 bar). Such a high equilibrium plateau is 40 bar or higher . An example of such hydrides is TiCr-i.β which has an equilibrium plateau at ruoin temperature much higher than 100 bars (see Fig.6). There are alsoτπediunτtemperature hydrides 5 with equilibrium-plateau attiigh pressures, like TiMn_2-y, Hf₂Cu, Zr₂Pd, TiCu₃ or Vo.855 Cr₀.ι 5 which can be ofϊnterest fσrthis kind of application (see Figs. 5 and 6).

Under these circumstances, when there is a need for hydrogen, the gaseous system of the storage tank will permit to accommodate such a o request with a very-short response time (t1 ) ofabout one second (forexample in the case of a carthataccelerates). When the pressure-withirrthe tank drops and changes from a value (1 ) to a value (2) (see Fig. 3), the hydride will regenerate the gaseous systeπrwith a lowerrespσnse-time (t2) of a few minutes, until the next acceleration. 5 This hybrid melhodmakes it possible-to substaπtially simplify the structural components required for heat transfer in order to induce the desoιptiσn-fro rrtfre-hydride-σrabsorptron therein. Moreover, this hybrid method permits, thanks tσ-the- high-pressure, to solve the problem of refilling hydrides such as the alanates (NaAIH₄ or LiAIH₄). As to the kind of hydrides that can be o used, refereTTCe-can be-rrrade to Figure 5 (hydrides of the AB₅ type) and Figure

6 (hydrides of the AB₂ type) enclosed herewith.

As an example of the way this method could be carried out, reference can be-made-to Figure 4 which shows a hybrid tank 11 for storing hydrogen in both-solid-and-gaseous form. The tank 11 comprises a container 5 having a metallic linerσrirτnerwall 15 covered with a polymeric outer shell 13.

This type of container is conventional and commonly used forstoring hydrogen in gaseous form at high pressure. It is preferably cylindrical in shape and provided with an axial opening 17. The liner 15 is usually made of aluminium whereas its outershell is made of a composite-material reinforced with carbon 0 fibers. In practice, thexontainer of the hybrid'tank 11 is intended to be used for storing hydrσgenϊn gaseous forrrrat a pressure usually hignerthan 40 bar and simultaneously to receive^and-store^ametal hydride in ordertostore hydrogen in solid form as well.

At least-one heat pipe 19 is mounted withiιτthe contaiπerto allow the circulatiσπ-of a tieat carrying fluidwithirrthe container 11. As shown, the tank 11 preferably comprises only one heat pipe 19 which is inserted into the coπtaiπerthrσugh-the-opeπiπg 17 and exterrds axially within the same. The tank 11 further comprrses a- heat exchanger located within the container to ensure thermal connection between the heat pipe 19 and the hydride. This heat exchangerpreferablyoorrsistsOfat leastσπe metallic grid, ora porous metallic structure orfibers 21 which-extends transversally withirrthe container and is in direct contact withtheaxial treat^" pipe 19, themetal liπerwall 15 of the container, and the hydride stored within the-same.

The use of such a system of heat pipe and heat exchanger to operate a metal hydride is already known (see, for example, U.S. patent No. 6,015,041 granted in 2000 in the name of WESTINGHOUSE SAVANNAH RIVER CO). In the present case, the invention essentially lies in that the incorpσratiσnOf such a-system into atank used so farσnly fσrstσring hydrogen in a gaseous form ar high-pressure in-ordertσ benefit from the advantages of both technσlσgies-sirrrultaneously.

Claims

1. A method for storing hydrogen in a hybrid form, characterized iπ that-it-comprises-coupling-and-ustng-within a single tank at least two hydrogen storage riieans-selected-from the-group consisting of : a) means-fσrstoriπg-hydrσgerr in^~a gaseous form ; b) means-forstσrirrg- hydrogen irra liquid form ; and c) meaπs-forstσriπg hydrogen in a solid form by absorption or adsorption, with the proviso trrat each-of the means fυr storing hydrogerrthat are used, is sized to store at least 5% by weight of the total amount of hydrogen stored within the tank.

2. The method according-to claim 1 , characterized in that the meansthat are coupled and used, iπclude-saidmeans for-storrrrg hydrogen in a gaseous foτm and-said-meaπs-fσrstσrrπg-hydrυgen in solid form with a metal hydride.

3. The method according-to claim 2, characterized in that the metal hydride has an equilibriunrrplateau pressure higher than 40 bar at the operatirrg-terrrperature ofthe tank.

4. The rrrethod-according-to claim 3, characterized in that the hydride is a Ti- or alanate (AIH _x) based hydride.

5. The method accσrding to claim 1 , characterized in that the means that are coupled and used, include said means for storing hydrogen in a liquid form and said means forstoring hydrogen in a solid form with a metal hydride.

6. A hybrid tank fcrrstoriπg-hydrσgen in both liquid and solid forms, characteri ed irrthat-it-coniprises-two-conceiiliic coπtaiπers, one of said coπtaiπers-hereiπafler called "inner container" being located within the other one which is hereinafter called "outer-container", said containers being separated by an insulating sleevσforrrraintaiπiπg-the-iπiier container at low temperature, said inner container- being used for-storing hydrogen in a liquid form, said outer coπtainerbeiπg irrdirecl cυmmuπicatiσn witlτthe nner container andoσntaining a metal hydride- for slυiiiig hydrogen- in a solid form.

7. The hybrid tank according to claim 6, characterized in that the hydride that is used in the outer container is an hydride having low equilibrium-plateau-pressure-at the-operatirrg-terrrperature ofthe tank.

8. The hybrid-tank accord ing tσ-claim 7, characterized in that the hydride that is used is-selected from the group-cαrisisting of NaAIH , LiAIH , LaNi₅H₆ and MgH₂.

9. The hybrid-tank according to claim 6, characterized in that the hydride within the outercσntaineris an hydride having a high equilibrium plateau pressure-af the operating-temperature of the tank.

10. The hybrid-tank accordrπg to claim 9, characterized in that the hydride is selected from the- group consisting of TiCn.e, TiMn_2-y, Hf₂Cu,

Zr₂Pd, TiCu₃ and V₀.₈55 Cr₀.ι₄₅.

11. A hybrid tank forstoring hydrogen in both/solid and gaseous forms, characterized in that it comprises:

- a cσntaiπerhaving a metallic liπer σr inner wall covered with a polymeric outer shell, said-cσntainerbeing-devised to store hydrogerrin gaseous form at a high-pressure-arrd to-receive and store a-metal hydride in σrderto also store hydrogen in solid form; - at least one heat pipe mounted in the container to allow circulation of a rrearcarryiπg-fluid-within-said container; and

- a heat exchanger located witrrhTthe containerin order to ensure thermal connection- between said at least-one heat pipe and the hydride.

12. The hybrid tank according to claim 11 , characterized in that:

- the cσπtaineris cylindrical and provided with an axial opening;

- the tank-comprises only one ofsaid at least-one heaf pipe which is inserted into the cσntatrrerthrσugh the openiπg-thereof and extends axially within said container; and - the heat exchanger consists of at least one element selected from the group cσrrsistrπg of-metallic grid, fibers or porous metallic structure extending traπsversally wrthin the coπtainer, each of said at least one grid being in direct contact with-the-axial-heat-pipe, theτπetallic liπer σf the- container and the hydride.

13. The hybrid tank according to claim 11 or 12, characterized in that the hydride that is used in the outercσπtaiπer is an hydride having low equilibrium-plateau pressure at the operating emperature of the tank.

14. The hybrid tank accordiπgto-claim 13, characterized in that the hydroxide that is used is selected from the group consisting of NaAIH₄, LiAIH , LaNi₅H₆ and MgH₂.

15. The hybrid tank according to claim 11 or 12, characterized in that the hydride within the outer container is an hydride having a high equilibrium state at tlie operating-temperature of the tank.

16. The hybrid tank according to claim 15, characterized in that the hydride is selected from the group consisting of TiCn.e TiMn₂-_y, Hf₂Cu,

Zr₂Pd, TiCu₃ and Vo.βss Cr₀.ι₄5.