CA2398195A1 - High performance gas unit storage micro cell, use thereof in portable fuel cells, in zero emission vehicle and in power generation plant - Google Patents

Abstract

Highly efficient gas unit storage cell comprising at least, a pressure vessel;
gas conducting means; micro-channels for the reversible storage of said gas, said micro-channels having a hydraulic diameter that is preferably comprised between 100 and 600 micrometers, preferably between 200 and 500 micrometers; and reversible heating and cooling means for the chemical and/or physical storage of gas and it's use in an exchangeable cartouche or cartridge for the storage of a gas.

Description

HIGH PERFORMANCE GAS UNIT STORAGE MICRO CELL, USE
THEREOF IN PORTABLE FUEL CELLS, IN ZERO EMISSION
VEHICLE AND IN POWER GENERATION PLANT
Field of the invention The invention relates to a high performance unit storage micro cell, to a gas unit container constituted by a micro cell according to the invention wherein at least part of the free volume inside the micro cell is filled with means susceptible to reversible stock a gas, by a gas storage system comprising a plurality of gas unit container according to the invention.
The invention further relates to the use of this gas unit container and/or to the use of this gas sorption storage system inter alia for the storage of hydrogen in zero emission automotives, in portable power fuel cells or in power generation plant system.
Descriution of the prior art In a near future, the demand for transportation with growing economies will inexorably increases in developing countries. The environmental consequence of that is the emission of greenhouse gases (GHG), mostly CO2, in huge amounts.
The road transportation sector now accounts for more than one quarter of all COZ
emissions in Canada (27 % 185 megatons equivalent COZ) [1]. Under these circumstances, hydrogen vehicles with a fuel cell or internal combustion engine will certainly offer the most environmentally friendly automotive technology. An other way of measuring the negative impact of fossil fuel is to consider that burning 1 litre of gasoline will produce 2.5 kg of CO2; it means that a car having a fuel efficiency of 10 litres per 100 km and that is driven for 20,000 km per year will need 2000 litres of gasoline and emit 5000 kg of COZ per year. Moreover, by developing a technology helping the emergence of hydrogen as an alternative energy Garner, the society is offered a chance to reduce of its dependence on the rapidly depleting fossil fuels.
Hydrogen, which can be produced with little or no emissions, is therefore projected to become a major energy source for both passenger vehicles and power generation.
Safe and convenient storage of hydrogen is crucial for the introduction of hydrogen into energy markets.
A hydrogen reservoir for portable and vehicular applications needs to be compact, lightweight, safe, technologically simple in use and inexpensive.
Metal hydrides have been seen for years as an appropriate medium for hydrogen storage. From the safety standpoint, metal hydrides are ideal. Hydrogen (which is chemically bonded in metal-hydrogen compounds) is stored in the tank in the solid form of hydrides at pressures and temperatures close to ambient and hydrogen release can be fully controlled. Moreover, hydrogen released from metal hydrides is extremely pure, and so poses no risk of fuel cell poisoning. In spite of these advantages, little work has been done on the development of practical metal hydride reservoirs for small-scale applications and for onboard fuel cells. The main reason is that the standard metal hydrides, such as those based on La-Ni compounds, have insufficient hydrogen capacity. In recent years, however, significant advances have been made in the development of novel metal hydride systems that offer new prospects for fuel cell related applications. In particular, a technique of catalysis of nanostructured magnesium based composite and sodium alanates (through a combination of mechanical, physical and chemical treatment) has resulted in materials with outstanding intrinsic hydrogenation performance. The nanocomposite materials possess enhanced kinetic properties and exhibit excellent resistance against decrepitation. These novel techniques allow magnesium based nanocomposites and sodium alanates to operate respectively down to temperatures below 250°C and 100°C
with hydrogen capacity of up to five times the capacity of LaNi5H6. These high capacities combined with relatively low operating temperature are unique: to date no other metal hydrides exhibit comparable characteristics. Furthermore, complex magnesium based nanocomposites (MgH2-Zr4~Ni53 and MgH2-Crz03) and sodium alanates (NaAlH4 and Na3AlII6) consist of very common and inexpensive elements and can be produced in large quantities by the simple process.
It now appears that catalysed magnesium, lithium, sodium, and aluminium hydrides are indeed the promising formulations that could overcome the hydrogen dissociation energy barrier. Numerous studies [2-14]. have shown the positive effect of transition metals (Ti, V, Mn, Fe, Ni and Zr), metal oxides (Sc203, Ti02, V205, Cr203, Mn203, Fe304, CuO, A1203, and Si02) and alloys (LaNis, FeTi and Mg2Ni) as catalysts for the stimulation of the sorption kinetics of nanocrystalline Mg-based and lithium and sodium alanate systems. Such catalysts additions give rise to a substantial reduction in the discharge temperature of magnesium, lithium, sodium, and aluminium hydrides. Dehouche et al. [15] have shown that the major advantage of such catalysts is that the metal work synergistically to enhance the activity of non transition complex hydride materials.
Various models of prototypes hydrogen/hydride storage beds have been constructed and evaluated over the last few years. Most of them have been constructed for vehicle use. The details of some storage units have been given by Baker et al. [6] and Dehouche et al. [7].
Hydride storage avoids high-pressure concerns since hydrides are stable with relatively low gas overpressures. It also avoids the technological complexity associated with liquid hydrogen and the relatively high cost associated with liquefaction. Hydride storage also permits the use of hydrogen as a car fuel without the need to establish a complete distribution infrastructure; hydride reservoirs could be filled from the gas output of little electrolyses units that could be installed at home.
Most important however remains the safety advantage in a container rupture situation; because of the endothermic nature of dehydrating, hydride tanks are self limiting.

Some, seeing the problems involved with the storing of a gaseous fuel, have suggested producing the hydrogen on-board through gasoline reforming; but since the reformer emits COz, this solution is totally unacceptable from the point of view of environment and it is necessary to develop hydrogen reservoirs.
There was therefore a need for new highly efficient hydrogen metal hydrides reservoirs that can be used for significantly reduce the size of gas storage on-board vehicles and on stationary power plants applications, these reservoirs being intended free from the limitation associated with already available gas storage reservoirs intended to provide hydrogen to fuel cells.
Brief description of the drawings Figure 1: represents the under view, the cross section and the top view of a hydride microchannels hydrogen storage reservoir according to first embodiment of the present invention.
1 S Figure 2 represents a hydride micro channels hydrogen storage reservoir according to an another embodiment of the present invention.
Figure 3 represents a hydride micro channels hydrogen storage reservoir according to a further embodiment of the present invention.
Description of the invention An object of the present invention is constituted by a new and highly efficient metal hydride storage container. An advantage of his container is that it may be use to develop reservoir that can be used in other applications that will bring about the hydrogen era. For example the containers according to the invention may be used as an hydrogen buffer into renewable energy systems; these systems based, on wind or solar energy, can be installed in remote locations and replace diesel generator.
The basis of the storage system is the dissociation of hydrogen gas by catalytic action into individual hydrogen atoms that bond to the magnesium, forming a metal hydride.
Such storage system can safely store hydrogen at an energy density equivalent to more than 100 g per L, whereas liquid-hydrogen density is about 71 g per L, and 5000-psia gas is about 31 g per L. That makes it practical to store enough fuel to allow a car a range of 500 km before refuelling. More recently Chrysler has unveiled a fuel cell concept car powered by sodium borohydride. The Chrysler Town & Country Natrium uses the hydrogen on demand system developed by Millennium Cell, which extracts hydrogen needed for fuel cell from sodium borohydride. This zero emissions vehicle has a range of 482 km and a top speed of 128 km/h.

For metal hydride hydrogen storage reservoir, it is of critical importance that adequate provision of heat supply be incorporated to bring heat at a rate sufficient to maintain HZ desorption at the maximum rate required by the application.
Similarly provision must be made to dissipate heat at a rate sufficient for rapid recharging of the tank.
High temperature rises are often encountered when reaction occurs and because metal hydrides show a quite low heat conductivity when used in ordinary powder beds, the hydrogen sorption processes are usually limited by internal heat transfer inside the bed. Therefore, research attention are focused on new reactor concepts (Dehouche et al. [8]) with advanced internal heat transfer insert matrix structure (Aluminium Foam and Star, Copper Ribbon and Cassettes) necessary to help maintaining isothermal condition, to avoid a thermodynamic limitation as well as to minimise the quantity of alloy required for the hydrogen storage. Under these circumstances, advanced micro channels concept is certainly a viable technology for enhancing the efficiency and the stability of metal hydride reservoir.
The high heat and mass transfer rates possible in micro fluidic systems could allow hydriding/dehydriding reactions to be performed under moderate conditions with higher yields than achievable with conventional systems The micro channel reservoir concept offers many advantages over the conventional metal hydride hydrogen storage system. It not only reduces heat and mass transfer resistances, but it also improves the sorption reactions as a result of the larger surface to volume ratio, the transport distance reduced by several orders of magnitude and small dead volumes. This concept also reduces weight by optimising the quantity of metal hydride required, which will improve fuel economy. This concept permits the easy integration of sensors and actuators, parallel screening, and mass fabrication of multiple units by replication. The presence of integrated sensors and control units could provide us with a truly "intelligent" reservoir allow; for example, if a reservoir module were to fail, it could be isolated and replaced while other parallel modules continues to feed the fuelled system. Finally this concept permits to get inherent safety characteristics that are absolutely critical for a wide scale use of hydrogen in vehicles and power generation applications.
The microchannels reservoir with innovative novel heat transfer design configuration will require an environmentally friendly fluids with improved heat transfer properties as well as new techniques to control the heat transfer fluid movement in networks of very small channels. Many approaches can be used for moving the heat transfer fluid through channels without having to use external pumps, such as electrokinetic and electrocapillary pressure pumping which requires electric fields. Gallardo et al. [9]
have shown that fields of less than 1 volt can be used to pump fluid and create droplet patterns on non patterned surfaces. Electrochemical reactions convert an aqueous compound from a surfactant to a non-surfactant species. Concentration gradients of these molecules lead to local differences in surface tension that can push thin layers of fluids along channels and through T connections. Prins et al. [ 10]
demonstrate control of fluid motion in three-dimensional structure with thousands of microchannels. Fluids are manipulated via electrocapillary pressure, originating from electrostatic control of the solid/fluid interfacial tension in the microchannels. They obtain velocities of several centimetres per second that are nearly two orders of magnitude larger than the velocities demonstrated by other electrofluidic actuation principles.
Microfabrication techniques are increasingly used in different fields to realise structures with capabilities exceeding those of conventional macroscopic systems.
Microfabrication techniques have shown spectacular advances in the electronics industry and chemical analysis systems and they are now creating new opportunities for energy related applications. There are many innovative techniques for machining the microchannels (200 to 500 microns thick) such as lithography, high-precision laser micromachining, microscale electrochemical micromachining, and low-cost laminate fabrication. In designing and developing microchannels hydrogen reservoir 1 S technology, it will be essential to focus on low-cost and advanced microsystems manufacturing techniques that are well adapted to mass production and that permit easy manufacture of customised modular units.
Reservoir evaluation The performances are evaluated under conditions as similar as possible to the ones under which it will be used. For this purpose the IRH has developed of a test bench for the evaluation of the performances of full-scale metal hydride hydrogen reservoirs. Sized in order to evaluate reservoirs holding up to 6 kg of hydrogen, the test bench has been designed to be able to operate at a maximum pressure of S00 psia and a maximum temperature of 3S0 C; the test bench can therefore be used with high 2S temperature materials (magnesium based hydrides) as well as room temperature ones (ABS sorption materials or alanates, for example) [11].
The gas unit container according to the invention may be advantageously used in a fuel tanks that works with a safe sorption, that is thermically managed and made commercially available to the public in the form of exchangeable cartouche or cartridge (blue, white, green or yellow) for the storage of preferably (natural gas, hydrogen and/or hythane in the case of urban pollution. Such selective storage means may be efficiently used to attempt to raise public awareness of ecological issues.
The long-term objective of the present project is to develop a metal hydride container that meets the demands of the emerging fuel-cell industry. Alloys able to operate at 3S temperatures of around and below 100°C (i.e. within the range of operation of PEM
fuel cells) with hydrogen capacities in the range 3-6 wt.% will be the first main goal.
As mentioned, magnesium based nanocomposites and sodium-based alanates come close to meeting these criteria. Over the next years, research will be aimed at the systematic enhancement of the properties of these metal hydrides. The Project will be complemented by the construction of a small-scale storage container with preliminary testing. Technical aspects of a small-size storage system will be analyzed and tested in operation with a portable fuel cell system.
S
References [ 1 ] Neitzert, F. F., K. Olsen, P. Collas, ( 1999) "Canada's greenhouse gas inventory, 1997 emissions and removals with trends", Environment Canada, 159 pages.
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[3] Jensen, C.M., R. Zidan, N. Mariels, A. Hee and C. Hagen, "Advanced titanium doping sodium aluminum hydride segue to a practical hydrogen storage material", Int. J. of Hydrogen Energy, 24 ( 1999), 246-465 [4] Jansen, C.M., S. Takara and R.A. Zidan, "Hydrogen Strorage via Catalytically Enhanced Metal hydrides", Proceeeding of the 1999 U.S.DOE Hydrogen Program Review, NREL/CP-570-26938 (5) G. Liang, S. Boily, J. Huot, A. Van Neste, R. Schulz: J. Alloys and Compounds 267 (1998) 302-306.

(6) G. Liang, S. Boily, J. Huot, A. Van Neste, R. Schulz: J. Alloys and Compounds 268 ( 1998) 302-307.

(7) G. Liang, J. Huot, S. Boily, A. Van Neste, R. Schulz: J. Alloys and Compounds 292 ( 1999) 247-252.

(8) L. Zaluski, A. Zaluska and J.O. Strom-Olsen, J. of Alloys and Compounds, 253-254, (1997), p. 70.

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(10) L. Zaluski, A. Zaluska, P. Tessier, J.O. Strom-Olsen and R. Schulz, J of Alloys and Compounds, 217 (1995), p. 295.

(11) S. Orimo, H. Fujii, K. Ikeda, Y. Fujikawa , and Y. Kitano, J. of Alloys and Compounds, 253-254 (1997), p. 94.

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(13) W. Oelerich, T. Klassen, R. Bormann, Journal of Alloys and Compounds 315 (2001 ),pp. 237-242.
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(15] Dehouche, Z., J. Goyette and T. K. Bose, G. Liang, J. Huot and R. Schulz (2001), "Bimetallic Catalyst Effect on the Sorption Properties of Nanocrystalline MgHz Hydride", Journal of Metastable and Nanocrystalline Materials, Vo1.377 (2001) pp. 77-84.

[16] Baker N., L. Huston, F. Lynch, L. Olavson and G. Sandrock (1981), "A
Clean Internal Combustion Engine for Underground Mining Machinery", Phase I
Report to US Dept. Of the Interior - Bureau of Mines. Contract H0202034, Minneapolis, Minn.
[17] Dehouche, Z., J. Goyette and T. K. Bose (1998), "Computational Evaluation of Multi-Hydrides Hydrogen Storage Concept", Workshop on Metal and Non-Metal Hydrides, NRC Ottawa, September 11.
[ 18] Dehouche, Z. W. de Jong, E. Willers, A. Isselhorst and M. Groll, "Modelling and Simulation of Heating/Air Conditioning systems Using the Multi-Hydrides Thermal-Wave Concept", Applied Thermal Enginneering, Vo1.18, No.6, 457 480, 1998.
[19] Gallardo, S. B., V. K. Gupta, F. D. Eagerton, L. I. Jong, V. S. Craig, R.
R. Shah and N. L. Abbott, "Electrochemical Principles for Active Control of Liquids on Submillimeter Scales," Science, vo1.283, 57-60, 1 January 1999.
[20] Prins, M. W. J., W. J. J. Welters and J. W. Weekamp, "Fluid Control in Multichannel Structures by Electrocapillary Pressure", Science, vo1.291, 277-280, 12 January 2001.
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Although the present invention has been described through specific embodiments, it is understood that many variations and modifications can be attached to these embodiments, and the present disclosure aims to cover such modifications , uses or adaptations of the present invention following, in general, the principles of the invention and including all variations of the present description which becomes known or accepted practice in the field of activity where the present invention is found, and may be applied to other essential elements mentioned below, and in agreement with the breath of the following claims.

Claims (29)

1. A gas (preferably an hydrogen) unit storage (micro) cell comprising at least:
- a pressure vessel;
- gas conducting means;
- micro-channels for the reversible storage of said gas, said micro-channels having a hydraulic diameter that is preferably comprised between 100 and 600 micrometers, preferably between 200 and 500 micrometers; and - reversible heating and cooling means for the chemical and/or physical storage of gaz, said unit storage cell having an internal volume that is preferably comprised between 2 and 5 cm3, preferably having an internal volume that is lower than 3 cm3.

2. A gas unit storage cell according to claim 1, wherein the pressure vessel has a cylindrical form.

3. A gas unit storage cell according to claim 1 or 2, wherein the length of the cylinder is about 4 time less that the diameter of said cylinder.

4. A gas unit storage cell according to claim 2, wherein the length of the cylinder is comprised between 0.75 and 1.5 cm and the diameter of said cylinder is comprised between 3 and 6 cm.

5. A gas unit storage cell according to anyone of claims 1 to 4, wherein the gas conducting means are micro-tubes perforated through their external surface.

6. A gas unit storage cell according to any one of claims 1 to 5 having filters situated between the gas conducting means and the reversible cooling means, said filters having a size ranging from 0.5 to 5 micrometers, and more preferably ranging from 0.5 to 2 micrometers.

7. A gas unit storage cell according to any one of claims 1 to 6, wherein the reversible heating and cooling means are constituted by micro-channels filled with an electrical conducting liquid, which is preferably an aqueous solution of a salt.

8. A gas unit storage cell according to claim 7, wherein said liquid is capable of being displaced inside said cooling means under the action of electrical field forces, as for example by electrokinetic or electrocapillary pressure pumpings which require electric fields.

9. A gas unit storage cell according to claim 8, wherein the electrical forces applies perpendicularly to the displacement direction of the cooling means.

10. A gas unit storage cell according to any one of claims 1 to 9, wherein the pressure vessel is constituted by a cylinder and the gas conducting means and/or the reversible heating and cooling means are constituted by microtubes that penetrate said cylindrical gas unit perpendicularly to one of its bases.

11. A gas unit storage cell according to anyone of claims 1 to 10, wherein said free volume comprises coaxial cylinders as retaining means susceptible to reversibly stock gas.

12. A gas unit storage cell according to anyone of claims 1 to 11, with a configuration as represented in Figure 1.

13. A gas unit storage cell according to anyone of claims 1 to 12, with a configuration as represented in Figure 2.

14. A gas unit storage cell according to anyone of claims 1 to 13, wherein the constituting elements are made of a metal or of metal alloys, preferably of aluminium alloys, more preferably of INOX coated with an aluminium oxide.

15. A gas unit container constituted by a gas unit cell according to anyone of claims 1 to 14, wherein the free volume inside said pressure vessel is at least partially filled with at least one means susceptible to~
reversibly stock a gas (preferably hydrogen), preferably the free volume is filled with at least one metal hydride.

16. A gas unit container according to claim 15, wherein at least 80, more preferably between 85 and 90 % of said free volume is filled with at least one light material with high storage capacity, with a high stability and with a good dynamic and/or with at least one metal hydride which is preferably selected in the group constituted by (magnesium based) nano composite materials such as MgH2-Zr47Ni53, MgH2-V-Ti, MgH2-oxide, Cr2O3, metal hydride alloys and mixtures thereof, more preferably wherein said nano composite is capable to desorb hydrogen at temperature less than 250 °C.

17. A gas unit container according to claim 16, wherein the total exchange surface generated by the perforations in the gas conducting means (microtubes)-being characterized, for microchannels with an interior diameter comprised 100 and 500 microns, by a ratio (internal surface of microchannels)/(total volume of the microchannels filled with metal hydride) that ranges from 20 to 500 cm2 par cm3, preferably from 25 to 125 cm2 par cm3.

18. A gas unit container according to any one of claims 15 to 17 for the storage of at least one gas selected in the group constituted by hydrogen, methane, propane, butane, ethane, hythane, natural gas and mixtures thereof.

19. A gas unit container according to claim 18, wherein the gas is hydrogen.

20. A gas unit container according to claim 19, wherein the hydrogen contains less than 120 ppm impurities, preferably between 10 and 20 ppm impurities.

21. A solid gas storage system, comprising a plurality of gas unit containers as defined in any one of claims 15 to 20, said containers~
being connected together and the sum of the diameters being preferably less than 1 meter.

22. A solid gas storage system according to claim 21, wherein said gas unit containers are connected in parallel.

23. Use of at least one container according to any one of claims 15 to 20 as on board portable fuel cell and/or as power generation plant.

24. Use according to claim 23 for zero emission vehicles.

25. Use of a metal hydride hydrogen storage system according to any one of claims 21 or 22 as hydrogen storage system for zero emission vehicles.

26. Use of a gas unit container according to any one of claims 15 to 20 as fuel tanks that works with a safe sorption, that are thermically managed.

27. Exchangeable cartouche or cartridge (blue, white, green or yellow) for the storage of preferably (natural gas, hydrogen and/or hythane in the case of urban pollution, said cartouche or cartridge containing at least one storage mean according to any one of the preceding claims.

28. Use of the storage means according to any one of the preceding claims in an attempt to raise public awareness of ecological issues.

29. Any aspect of the invention as described in the description and/or in the attached figures.