DE102006020393B4 - Fuel cell system with a hydrogen storage and method for cooling a fuel cell - Google Patents

Abstract

Fuel cell system (50) with a hydrogen storage (10, 100) with an inner housing (12), in which storage material (22) is arranged, in which hydrogen can be stored and which can receive and release hydrogen in a targeted manner, wherein the hydrogen storage (10, 100) a fuel cell exhaust stream (30) is acted upon, wherein the hydrogen storage (10) for releasing hydrogen from the hydrogen storage (10, 100) in a hot fuel cell exhaust stream (30) of the fuel cell (52) is arranged,
and wherein the fuel cell exhaust stream (30) flows around the inner housing (12) of the hydrogen storage (10) from the outside,
characterized in that
the fuel cell system comprises an arrangement for cooling the fuel cell (52), wherein the fuel cell (52) water from a liquid water supply (54) can be supplied and the fuel cell (52) is cooled by evaporation of the supplied water, wherein the fuel cell exhaust gas stream (30) when flowing around the inner housing (12) of the hydrogen storage (10, 100) cooled and water from the Brennstoffzellenabgasstrom (30) auskondensierbar, wherein the hydrogen storage (10, 100) has an output (34) through which the hydrogen storage ...

Description

The The invention relates to a fuel cell system with a hydrogen storage and a method of cooling A fuel cell according to the preambles of the independent claims.

to Storage of hydrogen is known to be either gaseous in this Pressure tanks with several hundred bar overpressure or at cryogenic temperatures liquid in special cooling tanks save.

Farther Solid storage are known, for example with so-called Metal hydrides in which the hydrogen is taken up in the storage material, held in their atomic structure and temperature increase or Pressure reduction is released again. Since these solid storage neither extreme temperatures still require high pressures are solid storage comparatively uncomplicated to handle. Such solid storage offer therefore for Mobile small applications, but also for use in land, water or air vehicles at. However, you can these storage materials at room temperature only about 2% of their Take up its own weight of hydrogen. That means, for example about 100 kg of the material needed to save about 2 kg of hydrogen.

Further need such solid storage for Hydrogen a cooling when refueling and heating when emptying, as hydrogen under heat absorption of the storage material is discharged.

The patent DE 69714233 T2 discloses a hydrogen solid reservoir having an open-celled metal foam that acts as a support matrix for a powdered, hydrogen-absorbing material. The material is finely distributed in the pores of the metal foam. To make it difficult to discharge the material from the hydrogen storage, the carrier matrix is divided into segments, which are partitioned off with partitions. The material can move within a segment, but is retained in the segment. Through the carrier matrix tubes are guided, in which either a cooling medium or a heating medium can be performed to cool the hydrogen storage during filling or to heat for emptying.

From the publication US 2005/0074657 A1 a fuel cell system with a solid storage for hydrogen is known, which is arranged in the exhaust stream of the fuel cell and is in heat exchange with this exhaust stream. Due to the waste heat of the exhaust gas flow, hydrogen is released from the hydrogen storage. For better control of the exhaust gas temperature, a heat exchanger is provided upstream of the hydrogen storage, via which the exhaust gas flow can be adjusted to a predetermined temperature.

From the patent US Pat. No. 6,861,168 B2 a fuel cell system according to the preamble of claim 1 is known.

The publication DE 103 32 438 A1 describes hydrogen storage material encapsulated in porous matrices for fuel cell systems.

From the publication DE 100 22 803 A1 For example, a reversible hydrogen storage tank is disclosed, inter alia, for fuel cell powered automobiles having an open cell metal sponge filled with hydrogen storage alloy powder.

The publication DE 35 42 185 C2 describes a pressure vessel filled with a porous material, particularly of metal, in which a hydrogen storage alloy is infiltrated and incorporated in powdered form to form a composite.

task The invention is a fuel cell system with a solid reservoir for hydrogen to provide as much as possible compactly built, easy to vary in design and especially for one Vehicle use is suitable. Furthermore, an efficient procedure for cooling a fuel cell can be specified.

The The object is achieved by the Characteristics of the independent claims solved.

Favorable price and further developments of the invention are the further claims remove.

According to the invention, a fuel cell system has a solid storage for hydrogen with an inner housing in which storage material in which hydrogen can be stored and which can receive and deliver hydrogen in a targeted manner is arranged. In order to release hydrogen, the hydrogen storage is arranged according to the invention in a fuel cell exhaust stream of the fuel cell, wherein the fuel cell exhaust stream, in particular a cathode exhaust stream, flows around the inner housing from the outside. The fact that cathode exhaust gas is used, a particularly effective heat transfer by condensation of the water contained mainly in the cathode exhaust gas is possible. The water is composed of the product water, which results from the fuel cell reaction, and the water, which is used for humidification and cooling ment of the fuel cell membrane is supplied. The fact that the inner housing is flowed around, separate lines for the fuel cell exhaust gas can be avoided within the inner housing.

Conceivable In addition to the use of cathode exhaust gas, the use of Anode exhaust gas. The fuel cell exhaust stream is effectively cooled. advantageously, Therefore, an efficient water recovery is possible. Further the fuel cell system according to the invention comprises a Arrangement for cooling the fuel cell, where the fuel cell from a water Liquid water supply supplied and the fuel cell by evaporation of the supplied water cooled is, wherein the fuel cell exhaust gas stream when flowing around the inner housing the hydrogen storage can be cooled and water is condensable out of the fuel cell exhaust stream, wherein the hydrogen storage has an output via which the condensed water in turn is the liquid water supply can be supplied.

When favorable Storage material for such solid storage are principally adsorptive materials like carbon structures, organometallic, so-called frameworks, Materials with intrinsic porosity, oxides, such as titanium or Suitable for silicon oxides. Preference is given to materials with chemical Binding of hydrogen, such as modified complex hydrides, for example, based on alanates, boranates, continue Amide / hydride systems, magnesium and its alloys, modified Aluminum hydrides, aminoboranes, metal hydrides, for example, modified AB2, AB5 alloys. Particularly preferred are materials having endothermic hydrogen release enthalpy in the range of 20-30 kJ / (mol H2). Also conceivable are organic materials, such as carbon nanotubes or organic polymers. The storage materials can be used as pellets, powders and Ganulat be used. However, the storage material can also pellet and granulate by itself under operating conditions. The filling the solid storage or the container and other handling the storage materials to the finished memory preferably find under inert gas or hydrogen atmosphere instead of to a degradation the storage materials in air to avoid. Basically the hydrogen storage also with a common pressure accumulator for hydrogen be combined.

When Storage material, such solids are particularly preferred the hydrogen endothermic release, wherein storage materials with an enthalpy in the range of 10-40 kJ / (mol H2), preferably 20-30 kJ / (mol H2) are particularly favorable. Cheap is for example, metal hydride or other similar solids, the under heat absorption Release hydrogen.

Especially Preferably, the fuel cell is cooled with evaporative cooling. at such fuel cells must within a short time a large amount of heat be transferred by condensation of water vapor to the water balance of the Close fuel cell system. This amount of heat can absorb the hydrogen solid storage, which by a endothermic reaction releases hydrogen. The hydrogen can in the fuel cell or in the fuel cell system, approximately in one catalytic burner, used. Advantageously, the volume of construction of fuel cell systems through this combination of hydrogen storage and refrigeration unit be reduced. It can achieved in a fuel cell vehicle greater vehicle performance be because the necessary specific radiator area can be reduced, which a limiting factor in the design of fuel cell vehicles represents.

By a particularly advantageous embodiment of the hydrogen storage can the heat transfer by condensation cooling the fuel cell exhaust gas are carried out particularly effectively. The housing can be filled with one or more porous bodies, in which or in which the memory material is locally concentrated is. Preferably, the storage material is in a gas-permeable container as fill or pressed concentrated. In general, such solid storage as a bad conductor of heat known, even if the storage material consists of metal hydride. The porous one Body, preferably a metal foam, in particular of a light metal such as Aluminum, is advantageous for storage of the container, as good thermally conductive coupling to the inner housing or the hot one Fuel cell exhaust stream and as an open-pored transport path for the hydrogen gas released from the storage material. The hydrogen storage is preferably constructed in the manner of a storage tube; it can also be several such storage tubes be summarized as memory.

Advantageous is when at least one hydrogen storage or multiple hydrogen storage combined into a unit with a storage enclosure and from the same fuel cell exhaust stream are umspülbar. At least the one hydrogen storage or several combined into one unit Hydrogen storage surrounded by a common storage enclosure and be umspülbar from the same fuel cell exhaust stream. Basically the hydrogen storage also with a common pressure accumulator for hydrogen be combined.

A greater flexibility in operation the hydrogen storage and thus in the supply of the fuel cell with hydrogen can be achieved if in the storage enclosure a additional cooling device is provided with a coolant flowed through is. Is appropriate especially for large ones Storage volumes.

at a method according to the invention for cooling a fuel cell of a fuel cell system with at least a hydrogen storage is the inner casing of the hydrogen storage of a fuel cell exhaust stream, preferably a cathode exhaust stream, flows around.

Preferably becomes a plurality of hydrogen stores from the same fuel cell exhaust stream lapped. In this case, the fuel cell exhaust stream cooled and water from the fuel cell exhaust stream condensed and recovered become.

Further Advantages and details of the invention are described below a preferred embodiment described in the drawing explained in more detail, without to this embodiment limited to be.

there demonstrate:

1 a schematic representation of a preferred fuel cell system with a preferred hydrogen storage,

2a , b; a preferred hydrogen storage in a first preferred embodiment (a) and a preferred second embodiment (b),

3 an embodiment of a memory with a plurality of hydrogen storage.

In The figures are functionally identical elements with the same reference numerals quantified.

This in 1 outlined preferred fuel cell system 50 for a preferred, not shown in detail vehicle is formed with a, preferably designed as a solid storage, hydrogen storage 10 . 100 equipped, wherein the basic structure preferably in the manner of a storage tube in the 2a and 2 B is explained in more detail.

The fuel cell system 50 includes a fuel cell 52 , which is constructed in a known manner from a plurality of individual cells, preferably with conventional ion-conducting polymer membranes (PEMFC). Particularly preferred is the fuel cell 52 by evaporative cooling, preferably by evaporation of water in the cathode, cooled.

The function of such a fuel cell system 50 is known in principle and will therefore not be further explained here. Input side is via a compressor 60 For example, air can be supplied as an oxidizing agent and hydrogen as a reducing agent, as well as dampening water from a liquid water supply 54 , which ensures a sufficient humidity of the fuel cell reaction gases oxygen and hydrogen. On the output side, there is a hydrogen feedback on the anode side 64 with a grant 62 provided as well as an exhaust pipe 66 for wet cathode exhaust leading to the hydrogen storage 10 . 100 leads. On the output side there is a capacitor 56 connected from the hydrogen storage 10 . 100 exiting cathode exhaust further dehumidified and an exhaust pipe 68 discharges into the environment. The capacitor 56 stands with a vehicle cooling system 58 in interaction.

An exit 16 of the hydrogen storage 10 . 100 is input side with the fuel cell 52 connected and supplies their anode with hydrogen ( 2a . 2 B ). From an exit 34 gets water from the hydrogen storage 10 the liquid water supply 54 fed, which also further, in the capacitor 56 obtained from the cathode exhaust gas recovered water.

The internal structure of a first preferred storage tube type hydrogen storage 10 is exemplary in 2a shown. 2 B shows a further embodiment of a second storage tube-like hydrogen storage 10 with larger storage capacity for hydrogen and additional temperature control option.

The hydrogen storage 10 has an inner housing 12 on, in the units 20 in the direction of a storage axis 18 strung together. Every unit 20 comprises a cup-shaped, formed of metal foam porous body 26 and storage material 22 that in a container 24 contained and thus locally concentrated and in the porous body 26 is embedded. The storage material 22 is preferably a metal hydride, in which hydrogen is storable and which can absorb and release hydrogen targeted. The container 24 is preferably formed of a sintered metal which is gas-permeable, but may also be formed of plastic. The porous body 26 preferably has a porosity of 5-90 ppi, preferably 10-20 ppi (pores per inch) (ie 2-35, preferably 4-8 pores per em). At an entrance 14 Hydrogen gas can be supplied for filling in the flow process, leaving hydrogen leaves the hydrogen storage 10 at the exit 16 ,

A storage enclosure 28 includes the inner housing 12 of the hydrogen storage 10 partially and leads hot cathode exhaust gas 30 to the inner housing 12 , At an exit 32 cooled cathode exhaust leaves the storage enclosure 28 while condensed water at an outlet 34 from the storage enclosure 28 is dissipated. The cathode exhaust gas 30 is typically supplied with a temperature of over 90 ° C and discharged at a significantly reduced temperature of T << 90 ° C. The from the storage material 22 escaping hydrogen is through out of the containers 24 Arcing arrows indicated. The porous body 26 represents the flow path of the hydrogen in the inner housing 12 outside the storage material 22 represents.

2 B shows a preferred hydrogen storage 10 in the manner of a storage tube having a plurality of such units 20 , pointing both towards the storage axis 18 as well as extend perpendicular thereto and are packed tightly together. The outer storage enclosure 28 is not shown explicitly. At the entrance 14 is one in porous material 40 arranged distribution element 36 , at the exit 16 is a collecting element 38 arranged so that hydrogen gas is as homogeneous as possible in the inner housing 12 can be distributed or flow. Furthermore, a tubular tempering device through which a temperature control medium can flow 42 inside the hydrogen storage 10 be provided to emptying the hydrogen storage 10 even better to control. The tempering device 42 is preferably a cooling device.

3 shows an embodiment of a hydrogen storage 100 in which four storage tube-like hydrogen storage 10 corresponding 2a and or 2 B with their inner housings 12 are arranged parallel to each other and to a unit in a common outer storage enclosure 28 are summarized.

All storage tube-like hydrogen storage 10 are from the same fuel cell exhaust stream or cathode exhaust stream 30 wash around. Condensed water is from an outlet 34 in the lower part of the housing 28 dischargeable.

On one side of the outer case 28 Hydrogen can be supplied (input 14 ), on the opposite side has the housing 28 an exit 16 through which hydrogen can escape and at a branch either the fuel cell or another consumer or a storage tank can be supplied.

Claims (9)

Fuel cell system ( 50 ) with a hydrogen storage ( 10 . 100 ) with an inner housing ( 12 ), in the memory material ( 22 ) is arranged, in which hydrogen is storable and which can absorb and release hydrogen specifically, wherein the hydrogen storage ( 10 . 100 ) with a fuel cell exhaust stream ( 30 ) is acted upon, wherein the hydrogen storage ( 10 ) for releasing hydrogen from the hydrogen storage ( 10 . 100 ) in a hot fuel cell exhaust stream ( 30 ) of the fuel cell ( 52 ), and wherein the fuel cell exhaust stream ( 30 ) the inner housing ( 12 ) of the hydrogen storage ( 10 ) flows around from the outside, characterized in that the fuel cell system has an arrangement for cooling the fuel cell ( 52 ), in which the fuel cell ( 52 ) Water from a liquid water supply ( 54 ) and the fuel cell ( 52 ) is cooled by evaporation of the supplied water, wherein the fuel cell exhaust gas stream ( 30 ) when flowing around the inner housing ( 12 ) of the hydrogen storage ( 10 . 100 ) and water from the fuel cell exhaust stream ( 30 ) is condensable, wherein the hydrogen storage ( 10 . 100 ) an output ( 34 ), over which the condensed water in turn the liquid water supply ( 54 ) can be fed. Fuel cell system ( 50 ) according to claim 1, characterized in that the inner housing ( 12 ) with one or more porous bodies) ( 26 ) in which or in which the storage material ( 22 ) is locally concentrated. Fuel cell system ( 50 ) according to claim 1 or 2, characterized in that the one hydrogen storage ( 10 ) or more hydrogen storage ( 10 ) into a single entity ( 100 ) with a storage enclosure ( 28 ) and from the same fuel cell exhaust stream ( 30 ) is or are umspülbar. Fuel cell system ( 50 ) according to claim 3, characterized in that in the storage housing ( 28 ) a tempering device ( 42 ) is provided, which can be flowed through with a temperature control. Fuel cell system ( 50 ) according to one of the preceding claims, characterized in that the fuel cell exhaust gas flow ( 30 ) Is cathode exhaust gas. Fuel cell system ( 50 ) according to one of the preceding claims, characterized in that the hydrogen storage ( 10 . 100 ) as a cooling device for the fuel cell ( 52 ) serves. Fuel cell system ( 50 ) according to one of the preceding claims, characterized in that the hydrogen storage ( 10 . 100 ) via a capacitor ( 56 ) for dehumidifying Brenn fuel cell exhaust with a vehicle cooling system ( 58 ) is operatively connected. Method for cooling a fuel cell ( 52 ) of a fuel cell system ( 50 ) with at least one hydrogen storage ( 10 . 100 ), in particular according to one of the preceding claims, wherein the hydrogen storage ( 10 . 100 ) with a fuel cell exhaust stream ( 30 ) is in heat exchange, characterized by the method steps a) supplying water to the fuel cell ( 52 ) from a liquid water supply ( 54 ); b) evaporation of the supplied water in the fuel cell ( 52 ), wherein the fuel cell ( 52 ) is cooled by evaporative cooling; c) supplying the fuel cell exhaust stream ( 30 ) of the fuel cell ( 52 ) to the hydrogen storage ( 10 . 100 ); d) flow around an inner housing ( 12 ) of the hydrogen storage ( 10 . 100 ) from the outside with the fuel cell exhaust gas stream ( 30 ), wherein the fuel cell exhaust stream ( 30 ) and water the fuel cell exhaust stream ( 30 ) is condensed out; e) supplying the condensed water from the hydrogen storage ( 10 . 100 ) to the liquid water supply ( 54 ). Method according to claim characterized in that a plurality of hydrogen storages ( 10 ) from the same fuel cell exhaust stream ( 30 ) is lapped.