WO2004034497A2

WO2004034497A2 - Fuel cell system

Info

Publication number: WO2004034497A2
Application number: PCT/GB2003/004403
Authority: WO
Inventors: Stephen David Voller; Richard Michael Clarke
Original assignee: Voller Energy Limited
Priority date: 2002-10-10
Filing date: 2003-10-10
Publication date: 2004-04-22
Also published as: GB0223480D0; GB2394115A; AU2003271936A1; GB2394115B; WO2004034497A3

Abstract

A first aspect of the invention relates to a portable electrical power supply comprising: a first housing (20) which contains at least one fuel cell (40); a second housing (10) containing power output means (56); and means (25) movably attaching said second housing to said first housing, said movement means permitting said second housing to be moved between a first position and a second position relative to the first housing; the arrangement being such that in said first position said at least one fuel cell is operable to produce electricity and said power output means is accessible to a user; and in said second position said at least one fuel cell is at least substantially deactivated. A second aspect of the invention relates to a portable electrical power supply comprising: a first housing (20) which contains at least one fuel cell (40), a second housing (10) containing power output means, and means (25) movably attaching said second housing to said first housing, said movement means permitting said second housing to be moved between a first position and a second position relative to the first housing; the arrangement being such that in said first position the output means is accessible to a user and said at least one fuel cell is operable to produce electricity, and in the second position the output means is inaccessible to a user.

Description

FUEL CELL SYSTEM

Field of the Invention

The present invention relates to a fuel cell system, that is, a device where reactants are fed into one or more individual cells to produce electrical energy.

As is well known in the art, there is some confusion regarding use of the term "fuel cell". In particular, the term is commonly used to refer to individual cells, as well as to a system as a whole which employs one or more of the aforementioned individual fuel cells to generate electricity. Hereafter, the term "fuel cell" will be used to refer to an individual cell, the term "fuel cell system" will be used to refer to the system as a whole, and the term "fuel cell stack" will be used to refer to a plurality of fuel cells connected together. Background to the Invention

A previously proposed fuel cell is fuelled by hydrogen and oxygen. Hydrogen and oxygen gases are held in chambers separated by a proton exchange membrane (PEM) or other electrolyte (the oxygen is often supplied as air rather than in a pure form). At an anode the hydrogen ionises to produce positively charged hydrogen ions. These pass through the proton exchange membrane to the chamber in which the oxygen is situated, where the oxygen reacts with electrons from a cathode and the hydrogen ions to form water molecules. This reduction/oxidation (redox) reaction creates a voltage between the electrodes, and typically a number of such cells are connected together to form a fuel cell stack that increases the electrical energy output by the fuel cell system. As water builds up in individual cells of the stack, it decreases the volume available for the hydrogen ions and oxygen to mix and decreases the area of catalyst available for the reactants, thereby lowering the efficiency of the fuel cells. Water is therefore removed, usually being vented as the oxygen is forced into the system. Whilst not all previously proposed fuel cells operate in this manner, other types of fuel cell (such as alkaline electrolyte fuel cells, or phosphoric acid fuel cells) convert hydrogen and oxygen to water, and some fuel cells which use fuels other than hydrogen also produce water as a waste product.

It will be apparent that the generation of water in the vicinity of an electrical outlet could present quite a hazard to a user of the fuel cell. Furthermore, as the aforementioned redox reaction is highly exothermic, it is also not unusual for the fuel cell stack to reach hazardously high temperatures. An aim of the present invention is to provide a safe and convenient fuel cell unit which helps to reduce the impact of the aforementioned hazards. Statement of Invention In pursuit of this aim, one presently preferred aspect of the present invention provides a portable electrical power supply comprising: a first housing which contains at least one fuel cell; a second housing containing power output means; and means movably attaching said second housing to said first housing, said movement means permitting said second housing to be moved between a first position and a second position relative to the first housing; the arrangement being such that in said first position said at least one fuel cell is operable to produce electricity and said power output means is accessible to a user; and in said second position said at least one fuel cell is at least substantially deactivated. In a preferred configuration, the output means is not accessible to the user in the second position.

According to another aspect of the present invention there is provided a portable electrical power supply comprising: a first housing which contains at least one fuel cell, a second housing containing power output means, and means movably attaching said second housing to said first housing, said movement means permitting said second housing to be moved between a first position and a second position relative to the first housing; the arrangement being such that in said first position the output means is accessible to a user and said at least one fuel cell is operable to produce electricity, and in the second position the output means is inaccessible to a user. Air may be drawn into the first housing fiom the outside environment, transferred from the first housmg to the second housing, and vented from the second housing. Alternatively, air may be drawn into the second housing from the outside environment, transferred from the second housing to the first housing, and vented from the first housing.

The at least one fuel cell may be of a type whose waste material includes water vapour. The at least one fuel cell may be of a type whose feed material includes hydrogen.

By providing two compartments in such a manner ensures that it is very clear when the fuel cell system is in an activated or activatable state, and when it is deactivated. A user can therefore be sure that when the fuel cell system is in a deactivated configuration, no electricity is being produced, and any electrical equipment to be powered by the fuel cell system cannot have live current supplied to it. Further, it allows the fuel cell to be kept separate from the power output means, reducing the possibility of waste products (such as water), or reactants (such as hydrogen) from the fuel cell stack coming into contact with the power output means (including, for example, power conditioning circuitry, output sockets, etc.). Brief Description of the Drawings

A preferred embodiment of the invention will now be described, by way of illustrative example only, with reference to the accompanying drawings, in which:

Fig. 1 is an illustrative perspective view of a fuel cell unit in an open position;

Fig. 2 is an illustrative diagrammatic view of the internal components of a fuel cell unit;

Fig. 3 is another illustrative perspective view of a fuel cell unit in an open position, showing two sides not visible in Figure 1 ; Fig. 4 is an illustrative perspective view of a fuel cell unit in a position intermediate between an open position and a closed position; Fig. 5 is another illustrative perspective view of a fuel cell unit in a closed position;

Figs. 6a and 6b are illustrative perspective views of an alternative fuel cell unit design in an open and closed position respectively; Figs. 7a and 7b are illustrative perspective views of another alternative fuel cell unit design in an open and closed position respectively; and

Figs. 8a and 8b are illustrative perspective views of yet another alternative fuel cell unit design in an open "and closed position respectively. Detailed Description of Preferred Embodiments Referring to figure 1, the fuel cell unit comprises a fuel cell stack compartment 20 (hereinafter referred to as the "lower compartment") and a power supply compartment 10 (hereinafter referred to as the 'upper compartment'), attached together by a hinge 25, and linked by a flexible conduit 30 (visible in figure 5). Referring also to figure 2, the lower compartment 20 contains a fuel cell stack 40, and various control means 41 to operate the fuel cell unit, hydrogen supply and the fans 42, which will be described in more detail below. The upper compartment 10 includes a replaceable hydrogen canister 50 secured by a cap 51 governed by a regulator mechanism 52 which supplies hydrogen via tubing 54 to the fuel cell stack 40, and power conversion circuits 60 including (for example) a DC-DC converter to hold the supply at a steady voltage over a range of currents, and an inverter which convert the direct current from the DC-DC converter to an alternating current. The power output from the fuel stack is conducted to the power conversion circuits by a flexible cable, the tubing 54 and cable being protected by the flexible conduit 30 between the two compartments. The power conversion circuits are connected to a three-pin socket 56 mounted in the wall of the upper compartment 10. The upper compartment includes an on-off power supply toggle switch 58.

The two compartments are joined by a hinge 25, which allows the compartments to be configured between two positions, referred to here as the "closed position" and the "open position". In the closed position, the face of the three-pin socket 56 is accessible. Swinging the upper compartment 10 through to the open position (figure 4 shows an intermediate position between the closed position and the open position) causes the face of the three pin socket 56 to be brought against a wall of the lower compartment 20 and hidden.

The wall 21 of the lower compartment against which the three pin socket 56 is hidden whilst the fuel cell unit is in the open position includes spring-biased plungers 22 which extend through the wall of the compartment, and control the operation of a position activated switch means provided inside the lower compartment (and hence not visible in the figures). The position activated switch means is operable to disconnect the power output means from the fuel cell stack, and as such acts as a "master" on-off switch for the system as a whole.

The position activated switch and the on-off toggle switch 58 are both required to be in their "on" position in order to activate the fuel cell unit, that is, if either switch is in the off position, the fuel cell unit will not be activated. When the fuel cell unit is in the closed position, the plungers 22 are extended and the position activated switch is in its "on" position. If the toggle switch 58 is also in the "on" position, the fuel cell stack is activated, with hydrogen and air being drawn into their respective portions of the fuel cells. The other necessary operations for the running of the fuel cell are also initiated, including operation of the fans 44 to draw air over the fuel cell stack.

Referring to Figure 3, the air enters the fuel cell unit from an inlet 62 situated in the upper housing 10. The air drawn through the upper housing 10 passes over the power conversion circuits 60, cooling them. As hydrogen is expelled from the hydrogen canister 50, the canister cools; the circulating air (warmed from the power conversion circuits) warms the camster 50. Where a metal hydride canister is used, for example, such warming is beneficial for promoting hydrogen production from the metal hydride. Referring to figure 5, the upper compartment 10 and the lower compartment 20 have corresponding communicating apertures 66 and 67, ideally at least one of which includes a gasket 68, so that air from the upper compartment 10 is drawn into the lower compartment 20. This air then circulates over the fuel cell, cooling it. The air then exits the lower compartment 20 through a vent 66. The speed with which the air circulates may be controlled by sensing circuitry in the fuel cell stack 40, so that the fuel cell stack and the other equipment is kept at an appropriate operating temperature for improved efficiency and power output.

The fuel cell stack 40 will not provide electricity immediately upon being activated. Therefore, a capacitor, rechargeable battery or other charge storage device is provided (located for example with the control means 41 or with the power conversion circuits 60) to provide current until the fuel cell stack 60 can supply power itself. This charge storage device may then be recharged from the fuel cell stack.

The fuel cell stack produces a direct current, the voltage of which is highly dependent upon the size of the current drawn. The current is therefore fed to a DC-DC converter and DC-AC converter in order to provide a steady AC current. Ideally, the power is converted to a 240N, output, alternating at 50 Hz, that is, the same as the output of the conventional UK mains. It will though be realised that the principles disclosed herein could be applied to fuel cell units required to provide direct current a different voltage output, or current conditioned in some other manner.

As previously discussed, the fuel cell stack 60 (and charge storage device, if necessary) provides power to the socket when the fuel cell unit is in the closed position and the "on-ofP' type switch is in the "on" position. Of course, the fuel cell stack may run at a reduced standby rate, or not run at all, if little or no power is being drawn from the unit. Having closed the fuel cell unit, the user may then treat the three-pin socket 56 in the same way as a domestic three-pin mains socket, switching the socket on and off as required using the toggle switch 58. It will be realised that alternative or additional switches may be supplied. For example, a similar plunger type switch 22 could be included between the upper compartment and the lower compartment to detect when the fuel cell unit is in a closed position (although in this instance the plunger type switch would be in the "off" position when extended). The switches could of course be of a different type, such as a proximity switch that can be flush or contained within the housing rather than a plunger type switch.

When the user no longer requires the fuel cell unit, the upper compartment is folded relative to the lower compartment as shown in figure 4, to the open position. As the upper compartment pivots about the hinge, the abutting apertures between the upper compartment and lower compartment part, so that air is drawn into the lower compartment through the lower compartment's aperture directly from the surrounding environment. When the fuel cell unit opens to switch the position activated switch means, the fuel cell is deactivated irrespective of whether or not the power switch is on or not.

The venting of the fuel cell stack is automatically controlled by circuitry incorporated in it. Air is drawn from that circulating over the fuel cell, and the waste water vapour is carried out of the fuel cell unit, to be vented from the lower compartment. When the fuel cell unit is folded to its open position, the fuel cell stack also vents the hydrogen from the fuel stack. Hydrogen is also vented from the tubing circuit connecting the fiiel cell stack to the regulator and hydrogen canister into the lower compartment. The fans in the lower compartment remaining operating after the fuel cell unit is in the open position until the hydrogen has been safely vented from the fuel cell unit.

The ancillary operations in the running of the fuel cell, such as the operation of the fans, is powered either from the charge storage device (particularly during the initial operation of the fuel cell) and the fuel cell stack itself The power for these operations may be drawn before or after the electricity has been conditioned by the DC -AC converter.

Although the fuel cell unit has been described as having a PEM type fuel cell, it will be seen that many other types of fuel cell could equally be used. The size of the fuel cell here illustrated is approximately 0.3 metres by 0.3 metres by 0.6 metres, and is intended to supply about 100W. The same principle could though be applied to other sizes of fuel cell units intended to supply smaller or larger amounts of power. For example, the fiiel cell unit having two compartments as previously described could be sufficiently small for a laptop computer or mobile phone, supplying in the region of 10W. Larger units could include handles and wheels in order to transport it. Alternative or additional outputs to a three-pin socket could be provided. It will also be realised that some of the components of the upper and lower compartments could be divided between the compartments in a different manner. For example, the hydrogen canister and its regulator could be located in the lower compartment, advantageously obviating the need to the hydrogen carrying tubing to extend between the compartments.

Not only the size, but also the relative proportions of the compartments may be varied. In the example described the side profile of each compartment is square, so that the fuel cell unit is a six-sided cuboid in both open and closed positions. Where the compartments are of different sizes, the open position will generally be a different shape than the closed position. The compartments need not be rectilinear; also, rather than a simple hinge, some other means could be used to allow one compartment to move in a constrained way relative to the other compartment, such sliding or rotating mechanisms.

Figs. 6a and 6a show one such alternative fuel cell unit design in its "closed" and "open" positions respectively. As shown in Fig. 6a the unit (in this instance in its "closed" position) comprises a lower compartment 20, and an upper compartment 10 which is pivotally attached to the lower compartment by means of a hinge 25 (visible in Fig. 6b). The upper compartment can be locked to the lower compartment by means of a pair of clasps 70 (or other securing means) and in this configuration the upper compartment provides a carrying handle for the unit. In the open position with the claps 70 undone and the upper compartment pivoted with respect to the lower compartment a planar surface 72 of the lower compartment is revealed, and access may be had by the user to power outlet means (not shown), such as a socket, provided therein. When the upper compartment is pivoted with respect to the unit to the "closed position" access to the planar surface, and hence to the power outlet means, is prevented. Figs. 7a and 7b illustrate another alternative fuel cell unit design wherein the entire top compartment is hinged along one edge to move with respect to the lower compartment. As will be appreciated, when the unit is in the "closed" position depicted in Fig. 7a, access to power outlet means (not shown) provided in a planar surface 72 of the lower compartment is prevented.

Figs. 8a and 8b illustrate another alternative fuel cell unit design. This particular unit is bigger and hence heavier than the preceding units, and to facilitate moving it around the lower compartment 20 has been provided with a pair of wheels 74. This unit, in a similar fashion to those depicted in Figs. 6 and 7 also prevents access to power outlet means (not shown) provided in a planar surface of the lower compartment when the unit is in the closed position.

The unit designs depicted in Figs. 6 and 7 include an aperture 76 in a sidewall of the lower compartment, and the unit design depicted in Figs. 8a and 8b includes two such apertures 76. These apertures are designed to permit a hydrogen (or other fuel) canister, such as a metal hydride canister, to be inserted into the lower compartment to provide a supply of hydrogen.

It will be recognised, of course, that the embodiments depicted in Figs. 6 to 8 differ from that depicted in Figs. 1 to 5 in that in the arrangement of Figs. 1 to 5 the power outlet means is obscured when the unit is opened, whereas in Figs. 6 to 8 the power outlet means is obscured when the unit is closed. However, both arrangements fall within the scope of the invention.

It should also be noted that in the arrangement of Figs. 6 to 8, the fuel cell system is not activated or deactivated by moving the upper compartment with respect to the lower compartment. Rather, a separate master switch (not shown in the figures) is provided on the planar surface (or indeed elsewhere on the unit) to disconnect the fuel supply from the fuel cell stack. An alternative means to turn off the system of Figs. 6 to 8 would of course be to remove the fuel canister(s) from the aperture or apertures - although use of the master switch is preferred as it is relatively easy to damage the valve assemblies typically provided on such fuel canisters.

A principal advantage of the arrangements depicted in Figs. 6 to 8 is that the upper compartment cannot be locked to the lower compartment when one or more electrical flexes are plugged into the power outlet means provided in the planar surface of the lower compartment. If it were possible to lock the two components together whilst the unit is operating there is a danger that hydrogen gas might build up in the upper compartment to a point where there is a risk of an explosion. The arrangements depicted, in contrast, ensure that the two compartments are at least partially separated, thereby providing a means for hydrogen to vent to atmosphere. Whilst preferred embodiments of the invention has been described above in detail, it will be apparent and should be noted that modifications and/or alterations may be made to the embodiments described without departing from the spirit and scope of the invention. It should also be noted that whilst particular combinations and permutations of features have been claimed, the scope of the invention is not limited thereto and instead extends to any combination and permutation of features described or claimed herein irrespective of whether that particular combination or permutation has been explicitly enumerated in the accompanying claims.

Claims

1. A portable electrical power supply comprising: a first housing which contains at least one fuel cell; a second housing containing power output means; and means movably attaching said second housing to said first housing, said movement means permitting said second housing to be moved between a first position and a second position relative to the first housing; the arrangement being such that in said first position said at least one fuel cell is operable to produce electricity and said power output means is accessible to a user; and in said second position said at least one fuel cell is at least substantially deactivated.

2. A portable electrical power supply according to claim 1 wherein the output means is not accessible to the user in the second position.

3. A portable electrical power supply comprising: a first housing which contains at least one fuel cell, a second housing containing power output means, and means movably attaching said second housing to said first housing, said movement means permitting said second housing to be moved between a first position and a second position relative to the first housing; the arrangement being such that in said first position the output means is accessible to a user and said at least one fuel cell is operable to produce electricity, and in the second position the output means is inaccessible to a user.

4. A portable electrical power supply according to Claim 3, wherein said at least one fuel cell is operable to produce electricity irrespective of whether said second housing is in said second position or said first position.

5. A portable electrical power supply according to Claim 3 or 4, comprising switch means operable to connect or disconnect a fuel source to or from said at least one fuel cell thereby activating or deactivating the power supply.

6. A portable electrical power supply according to Claim 5, wherein the power supply may additionally be deactivated by decoupling said fuel source from an inlet connector of said power supply.

7. A portable electrical power supply according to any preceding claim wherein air is drawn into the first housing from the outside environment, transferred from the first housing to the second housing, and vented from the second housing.

8. A portable electrical power supply according to any of claims 1 to 7, wherein air is drawn into the second housing from the outside environment, transferred from the second housing to the first housing, and vented from the first housing.

9. A portable electrical power supply according to any of the previous claims wherein the fiiel cell is of a type whose waste material includes water vapour.

10. A portable electrical power supply according to any preceding claim, comprising a plurality of fuel cells arranged as a fuel cell stack.

11. A portable electrical power supply according to any preceding claim, wherein said power output means comprises one or more socket outlets.

12. A portable electrical power supply according to Claim 11, wherein said power output means additionally comprises power conditioning means.

13. A portable electrical power supply according to any of the previous claims wherein the fuel cell is of a type whose feed material includes hydrogen.

14. A portable electrical power supply according to any of the previous claims wherein the moveable attachment means is provided by a hinge means.