Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
APPARATUS FOR COOLING A DEVICE COMPRISING A FUEL CELL
Document Type and Number:
WIPO Patent Application WO/2005/112156
Kind Code:
A2
Abstract:
According to the invention, there is provided an apparatus for cooling a device powered by a fuel cell (6) and having at least one component which requires cooling, the apparatus comprising an evaporative cooler (1) for cooling the or each component and wherein the evaporative cooler (1) comprises a cooling member having a surface from which evaporation can occur, means for interconnecting a waste fluid outlet of the fuel cell (6) to the evaporative cooler (1), and means for drawing the fluid to the evaporative surface of the cooling member.

Inventors:
Day, Richard Francis (47 Monkfield Lane, Great Cambourne, Cambridgeshire CB3 6AH, GB)
Application Number:
PCT/GB2005/001806
Publication Date:
November 24, 2005
Filing Date:
May 13, 2005
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
CAMBRIDGE CONSULTANTS LIMITED (Science Park, Milton Road, Cambridge CB4 0DW, GB)
Day, Richard Francis (47 Monkfield Lane, Great Cambourne, Cambridgeshire CB3 6AH, GB)
International Classes:
F28D5/00; F28F13/00; G06F1/20; G06F1/26; H01M8/00; H01M8/04; (IPC1-7): H01M8/00
Domestic Patent References:
WO2001009969A12001-02-08
Foreign References:
US20020075651A12002-06-20
US4935169A1990-06-19
EP0301757A21989-02-01
Attorney, Agent or Firm:
Cozens, Paul Dennis (Mathys & Squire, 120 Holborn, London EC1N 2SQ, GB)
Download PDF:
Claims:
Claims:
1. Apparatus for cooling a device powered by a fuel cell and having at least one component which requires cooling, the apparatus comprising an evaporative cooler for cooling the or each component and wherein the evaporative cooler comprises a cooling member having a surface from which evaporation can occur, means for interconnecting a waste fluid outlet of the fuel cell to the evaporative cooler, and means for drawing the fluid to the evaporative surface of the cooling member.
2. Apparatus according to Claim 1, wherein the interconnecting means defines at least in part a closed fluid path extending from the evaporative cooler toward the fuel cell, preferably extending to the waste fluid outlet or a store for waste fluid or the fuel cell.
3. Apparatus according to Claim 2, wherein the fluid pressure in the fluid flow path is generally at a different pressure to atmospheric pressure.
4. Apparatus according to any of claims 1 to 3, wherein the drawing means controls the fluid pressure in the apparatus.
5. Apparatus according to any of the preceding claims, wherein the cooling member includes an inlet and wherein the drawing means is adapted to draw fluid from the inlet to the evaporative surface, and preferably wherein the inlet is connected to the interconnecting means so as to be sealed therewith.
6. Apparatus according to any of the preceding claims, wherein the drawing means is adapted to draw fluid by capillary action.
7. Apparatus according to any to the preceding claims, wherein the drawing means includes at least one capillary tube.
8. Apparatus according to Claim 7, wherein the or each capillary tube is directly (and preferably sealably) connected to the interconnecting means.
9. Apparatus according to Claim 7 or 8, wherein the or each capillary tube controls the fluid pressure in the interconnecting means.
10. Apparatus according to any of the preceding claims, wherein the drawing means includes a wick.
11. Apparatus according to Claim 10, wherein the wick is in the form of a porous member.
12. Apparatus according to any of the preceding claims, wherein the drawing means includes a conduit incorporating porous material.
13. Apparatus according to any of the preceding claims, wherein the drawing means includes a sandwich of plates, conduits for the fluid being defined between said plates.
14. Apparatus according to Claim 13, wherein each plate comprises a network of branched capillary channels.
15. Apparatus according to Claim 13, wherein each plate comprises a plurality of outwardly radiating channels.
16. Apparatus according to any of the preceding claims 13 to 15, wherein the conduits are in the form of capillary channels.
17. Apparatus according to any of the preceding claims 13 to 16, wherein the conduits are etched into the plates.
18. Apparatus according to any of the preceding claims 13 to 17, wherein the sandwich of plates is arranged to from a finned structure.
19. Apparatus according to any of claims 13 to 18, wherein spacer elements are provided between the plates.
20. Apparatus according to any of the preceding claims, which further comprises means for collecting waste fluid produced by the fuel cell.
21. Apparatus according to Claim 20, wherein the interconnecting means is adapted to interconnect the collecting means with the evaporative cooler.
22. Apparatus according to any of the preceding claims, wherein the interconnecting means is adapted to directly interconnect the fuel cell with the evaporative cooler.
23. Apparatus according to any of the preceding claims, which further comprises means for storing the waste fluid.
24. Apparatus according to Claim 23, wherein the interconnecting means is adapted to interconnect the fuel cell with the evaporative cooler and the storing means.
25. Apparatus according to Claim 23 or 24, wherein the interconnecting means is adapted to interconnect the evaporative cooler to the fuel cell via the storing means.
26. Apparatus according to any of the preceding claims, which further comprises means for controlling fluid flow between the fuel cell and the evaporative cooler.
27. Apparatus according to Claim 26, wherein the controlling means comprises at least one valve.
28. Apparatus according to Claim 26 or Claim 27, wherein the controlling means comprises at least one pump.
29. Apparatus according to any of the preceding claims, further comprising means for sensing atmospheric pressure.
30. Apparatus according to Claim 29, further comprising means for controlling fluid flow between the fuel cell and the cooling means in dependence on atmospheric pressure.
31. Apparatus according to any of the preceding claims, wherein the interconnecting means is adapted to convey fluid.
32. Apparatus according to Claim 31, wherein the interconnecting means is adapted to convey fluid by passive or nonmechanical means.
33. Apparatus according to Claim 32, wherein the interconnecting means is adapted to convey fluid by capillary action.
34. Apparatus according to Claim 33, wherein the interconnecting means includes a capillary tube.
35. Apparatus according to Claim 33 or Claim 34, wherein the interconnecting means includes a wick.
36. Apparatus according to any of Claims 33 to 35, wherein the interconnecting means includes a conduit incorporating porous material.
37. Apparatus according to any of the preceding claims, wherein a plurality of bores are provided in the evaporative surface.
38. Apparatus according to Claim 37, wherein each bore defines an opening to a respective capillary tube.
39. Apparatus according to Claim 37 or 38, wherein the bores are in the form of micropores.
40. Apparatus according to any of the preceding claims, wherein the cooling member is covered by a layer of porous material.
41. Apparatus according to any of the preceding claims, wherein the cooling member is finned.
42. Apparatus according to any of the preceding claims, further comprising the fuel cell.
43. Apparatus according to any of the preceding claims, which further comprises means for connecting the evaporative cooler directly to the or each component.
44. Apparatus according to any of the preceding claims, further comprising means for transferring thermal energy between the cooling means and the or each component.
45. Apparatus according to Claim 44, wherein the means for transferring thermal energy comprises a heat exchanger.
46. Apparatus according to Claim 44 or 45, wherein the thermal transfer means comprises a thermally conductive interface.
47. Apparatus according to any of the preceding claims 44 to 46, wherein the means for transferring thermal energy includes a heat pipe.
48. Apparatus according to any of the preceding claims 44 to 47, wherein the means for transferring thermal energy includes a closed fluid circuit which is adapted to link the cooling means with the or each component.
49. Apparatus according to Claim 48, further comprising means for conveying fluid around said circuit.
50. Apparatus according to Claim 49, wherein the conveying means includes a pump.
51. Apparatus according to Claim 49, wherein the conveying means is adapted to convey fluid by passive nonmechanical means.
52. Apparatus according to Claim 51, wherein the conveying means is adapted to convey fluid in dependence on gravity.
53. Apparatus according to Claim 51, wherein the conveying means is adapted to convey fluid in dependence on convection.
54. Apparatus according to any of the preceding claims, wherein the evaporative cooler is adapted to be exposed directly to the atmosphere.
55. Apparatus according to any of the preceding claims, further comprising means for transferring moisture from the evaporative cooler to the atmosphere.
56. Apparatus for cooling a device powered by a fuel cell and having at least one component which requires cooling, the apparatus comprising an evaporative cooler for cooling the or each component, the evaporative cooler being adapted to be exposed directly to the atmosphere and comprising a cooling member having a surface from which evaporation can occur, means for interconnecting a waste fluid outlet of the fuel cell to the evaporative cooler, and means for transferring moisture from the evaporative cooler to the atmosphere.
57. Apparatus according to Claim 55 or 56, wherein the transfer means comprises a formation adapted to promote air flow over the evaporative cooler.
58. Apparatus according to Claim 57, wherein the formation includes at least one duct adapted to link the evaporative cooler with the atmosphere.
59. Apparatus according to any of claims 55 to 58, wherein the evaporative cooler is adapted to form part of an outer casing of the device.
60. Apparatus according to any of the preceding claims, wherein the evaporative cooler includes a fan.
61. A device adapted to be powered by a fuel cell, which comprises an apparatus according to any of the preceding claims.
62. A device according to Claim 61, further comprising the fuel cell.
63. A device adapted to be powered by a fuel cell, which comprises an evaporative cooler adapted to be exposed directly to the atmosphere, means for interconnecting a waste fluid outlet of the fuel cell to the evaporative cooler, and means for transferring moisture from the evaporative cooler to the atmosphere.
64. A device according to any of Claim 63, wherein the transfer means comprises a formation adapted to promote air flow over the evaporative cooler.
65. A device according to Claim 64, wherein the formation comprises at least one duct adapted to link the evaporative cooler with the atmosphere.
66. A device according to Claim 65, wherein the duct further comprises a fan.
67. A device according to any of the preceding claims 63 to 66, wherein the device comprises a casing, and wherein the formation comprises at least a pair of orifices provided in the casing, the pair of orifices being adapted to facilitate air flow over the evaporative cooler.
68. A device according to any of Claims 63 to 67, further comprising a cavity, said cavity being adapted to accommodate the evaporative cooler such that at least a portion of the evaporative cooler is directly exposed to the atmosphere.
69. A device according to any of Claims 63 to 68, wherein the evaporative cooler comprises a fan.
70. A device according to any of Claims 63 to 69, wherein the device is portable.
71. A portable device adapted to be powered by a fuel cell, which comprises an apparatus according to any of Claims 1 to 60. 72.
72. A portable device according to Claim 71, further comprising the fuel cell.
73. An evaporative cooler for cooling components, which comprises a cooling member having an evaporative surface from which evaporation can occur, means for drawing fluid to the evaporative surface, and means for exchanging heat with the component.
74. An evaporative cooler according to Claim 73, wherein the drawing means is adapted to draw fluid by capillary action.
75. An evaporative cooler according to Claim 73 or 74, wherein the drawing means includes at least one capillary tube.
76. An evaporative cooler according to Claim 75, wherein the or each capillary tube together define a threedimensional cooling structure.
77. An evaporative cooler according to any of the preceding claims 73 to 76, wherein the evaporative surface comprises a plurality of bores each bore defining an opening to a respective capillary tube.
78. An evaporative cooler according to any of the preceding claims 75 to 77, further comprising a manifold connected to the or each capillary tube and adapted to be connected to a fluid outlet.
79. An evaporative cooler according to any of the preceding claims 73 to 78, wherein the evaporative cooler includes a sandwich of plates, conduits for the fluid being defined between said plates.
80. An evaporative cooler according to Claim 79, wherein each plate comprises a network of branched capillary channels.
81. Apparatus for cooling a device substantially as herein described and illustrated with reference to the accompanying drawings.
82. A device substantially as herein described and illustrated with reference to the accompanying drawings.
83. A portable device substantially as herein described and illustrated with reference to the accompanying drawings.
84. An evaporative cooler substantially as herein described and illustrated with reference to the accompanying diagrammatic drawings.
Description:
COOLING

This invention relates to a cooling apparatus. The invention also relates to a device powered by a fuel cell, and in particular to portable devices powered by fuel cells. The invention also relates to a device and to a method of cooling. The invention also relates to an evaporative cooler.

Fuel cells are emerging as power sources for power-hungry portable electronic devices. Their benefits compared to battery packs include instantaneous recharge capabilities, by supplying new fuel, and inherently higher power-density than conventional rechargeable batteries. They are therefore especially attractive for power-hungry applications such as portable computers, advanced mobile phones, video cameras and the like. The fuel cells which are emerging as power sources for portable electronic applications are hydrogen fuelled Proton Exchange Membrane Fuel Cells (PEMFC) and methanol fuelled Direct Methanol Fuel Cells (DMFC). In both of these technologies water of a high purity is generated as a by-product on the anode side of the fuel cell. To prevent flooding and damaging the electronic equipment the water is typically collected in a separate compartment, for example, of the fuel cartridge supplying the methanol.

Power hungry portable electronic devices frequently have a cooling problem. Laptops are often equipped with noisy fans to dissipate the heat generated by high performance processors. There are even reports of users burning themselves while using laptops.

Portable electronic devices often contain components with high specific heat emissions. Examples are central processing units (CPU's) where the area specific heat emissions have increased substantially with increasing computation power and the number of transistors per unit area. The provision of sufficient cooling to prevent thermal degradation of the electronic component is increasingly difficult. Thus, laptops either: • contain fans increasing the convective flow, or • conduct the heat from the CPU into the laptop housing and then dissipate the heat via natural convection over a larger surface area.

The above approaches have disadvantages. In particular, the application of cooling fans either requires substantial packaging space or in the case where a device has been designed to minimise space, the high flow speeds required make the system noisy. Furthermore the additional energy required to drive the fan reduces the lifetime of the power source for the portable electronic device.

When using the second approach, the casing can get very hot especially if the laptop is placed on a surface, which restricts the air circulation. This can lead to health and safety issues. In the publication Lancet™ there has been an article about a laptop computer user who inflicted severe burns by working with a laptop on his lap for approximately one hour.

According to a broad first aspect of the invention, there is provided apparatus for cooling a device powered by a fuel cell and having at least one component which requires cooling, the apparatus comprising means for cooling the or each component, and means for interconnecting the fuel cell with the cooling means, thereby to enable waste fluid produced by the fuel cell to cool the or each component.

By providing means for interconnecting the fuel cell with the cooling means may enable the device to work more efficiently, since the waste fluid produced by the fuel cell is used to cool components in the device which require cooling.

The term "component" as used herein is preferably intended to denote any part of a device, for example, in the case of a laptop, the central processing unit, other microprocessors, or the casing of the laptop itself, etc.

Typically, waste fluid such as water is produced as a by-product of chemical reactions which occur in the fuel cell during operation of the fuel cell.

When using a fuel cell power source generating water as a by-product (e.g. a PEMFC or DMFC), the water produced has to be collected or managed in some way to prevent it damaging the electronic equipment or its surroundings. Provisions made in the prior art include water storage tanks incorporated in the fuel supply cartridge carrying a weight and packaging volume penalty. When collecting the water within the portable device, the weight will increase. If the fuel cell is operated by oxidising hydrogen (H2 + Vi 02 => H2O) the weight of the collected water will be 9 times higher than the weight of the hydrogen fed into the system. If the system is fuelled by pure methanol the weight increase is smaller (CH3OH + 3/2 O2 => CO2 + 2 H2O) due to the release of gaseous carbon dioxide and the weight of water collected is 36/32 times the weight of methanol put into the system. Thus, using the waste water for cooling reduces the necessity to store all the waste water by-product of the fuel cell, thereby improving the usability of the device.

According to another aspect of the invention, there is provided an apparatus for cooling a device powered by a fuel cell and having at least one component which requires cooling, the apparatus comprising an evaporative cooler for cooling the or each component and wherein the evaporative cooler comprises a cooling member having a surface from which evaporation can occur, means for interconnecting a waste fluid outlet of the fuel cell to the evaporative cooler, and means for drawing the fluid to the evaporative surface of the cooling member.

In this way the apparatus is able to control cooling of a component more efficiently.

Preferably, the interconnecting means is adapted to directly interconnect the fuel cell with the cooling means.

Preferably, the apparatus further comprises means for storing waste fluid produced as a by-product of chemical reactions which occur in the fuel cell.

By providing a storing means, the apparatus may enable waste fluid to be drawn on demand when required, or stored for later use when not required, thereby improving efficiency of operation.

Preferably, the interconnecting means is adapted to interconnect the fuel cell with the cooling means and the storing means. Preferably, the interconnecting means is adapted to interconnect the cooling means to the fuel cell via the storing means.

Preferably, the apparatus further comprises means for controlling fluid flow between the fuel cell and the cooling means. By providing controlling means the apparatus may further improve efficiency.

Preferably, the controlling means comprises at least one valve.

Preferably, the controlling means comprises at least one pump.

Preferably, the apparatus further comprises means for sensing atmospheric pressure.

Preferably, the apparatus further comprises means for controlling fluid flow between the fuel cell and the cooling means in dependence on atmospheric pressure.

Preferably, the interconnecting means is adapted to convey fluid.

More preferably, the interconnecting means is adapted to convey fluid by passive or non-mechanical means.

The phrase "passive or non-mechanical means" as used herein is preferably intended to denote means which do not require input of power or energy, acting instead for example as a result of gravitational forces or capillarity.

Preferably, the apparatus comprises means for conveying fluid by capillary action from the fuel cell to the cooling means.

The phrase "capillary action" as used herein is preferably intended to denote any phenomenon associated with surface tension, such as the elevation or depression of liquids in capillary tubes, the action of blotting paper and the operation of wicks, i.e. any and all phenomena associated with surface tension, regardless of whether an actual capillary tube is used. By providing conveying means for conveying fluid by capillary action from the fuel cell to the cooling means the invention can enable fluid to be drawn as required from the fuel cell. The apparatus is thus passively self-regulating, which can enable it to work more efficiently. Furthermore, additional energy is not required to transport fluid to the cooling system.

Thus, the forced supply of liquid to the cooling surfaces (by pump or pressurised tank) may no longer be required.

Preferably, the interconnecting means includes a capillary tube.

Preferably, the interconnecting means includes a wick.

Preferably, the interconnecting means includes a conduit incorporating porous material.

Preferably, the interconnecting means includes a sandwich of plates, conduits for the fluid being defined between said plates.

Preferably, each plate comprises a network of branched capillary channels.

Preferably, each plate comprises a plurality of outwardly radiating channels.

Preferably, the apparatus further comprises the fuel cell.

Advantageously, the cooling means preferably comprises an evaporative cooler. By providing an evaporative cooler, the apparatus may cool components requiring cooling more efficiently and without requiring any additional energy.

It is known that the surface specific cooling power achievable with evaporation is much higher than with convective cooling. One major challenge to overcome when applying evaporative cooling is that the evaporated liquid has to evaporate without any residue otherwise the heat exchanger surface fouls over time reducing the heat transfer achievable.

Proposed open circuit evaporative cooling devices for electronic components require an external pump and a fluid vaporising without residue, otherwise the evaporative heat exchanger will foul, which reduces heat transfer capabilities. The heat exchanger therefore has to be cleaned regularly or be replaced. Fluids pure enough to vaporise without residue are typically quite expensive and the requirement for refilling a fluid adds inconvenience to the operation of the equipment. Furthermore, active control is required in order to prevent flooding of the cooler and neighbouring components.

Thus, the use of the waste water by-product of the fuel cell can lead to more efficient operation of the evaporative cooler and can increase the mean time between failure of the evaporative cooler due to fouling.

Preferably, the evaporative cooler is adapted to be exposed directly to the environment.

Preferably, the evaporative cooler comprises a cooling member having a surface from which evaporation can occur.

More preferably, the apparatus comprises means for passively conveying fluid to the surface of the cooling member.

This important feature is provided independently. According to another aspect of the invention, there is provided apparatus for cooling a device powered by a fuel cell and having at least one component which requires cooling, the apparatus comprising an evaporative cooler for cooling the or each component, the evaporative cooler comprising a cooling member having a surface from which evaporation can occur, and means for passively conveying fluid to the surface of the cooling member. The provision of a conveying means can lead to passive self-regulation, which may optimise the operation of the apparatus.

Preferably, the cooling member is covered by a layer of porous material.

Preferably, the cooling member is finned.

Preferably, the conveying means is adapted to convey fluid from the fuel cell to the surface of the cooling member.

Preferably, the cooling member includes an inlet and wherein the conveying means is adapted to convey fluid from the inlet to the surface of the cooling member.

Preferably, the conveying means is adapted to convey fluid by capillary action.

Preferably, the conveying means includes at least one capillary tube.

Preferably, the conveying means includes a wick.

Preferably, the wick is in the form of a porous member.

Preferably, the conveying means includes a conduit incorporating porous material.

Preferably, the conveying means includes a sandwich of plates, conduits for the fluid being defined between said plates.

Preferably, each plate comprises a network of branched capillary channels.

Preferably, each plate comprises a plurality of outwardly radiating channels.

Preferably, the apparatus further comprises means for connecting the cooling means directly to the or each component. Preferably, the apparatus further comprises means for transferring thermal energy between the cooling means and the or each component. In this way, it is possible to cool multiple components or components that cannot be connected directly to the cooling means.

Preferably, the means for transferring thermal energy comprises a heat exchanger.

Preferably, the thermal transfer means comprises a thermally conductive interface.

Preferably, the means for transferring thermal energy includes a heat pipe.

Preferably, the means for transferring thermal energy includes a closed fluid circuit which is adapted to link the cooling means with the or each component.

Preferably, the apparatus further comprises means for conveying fluid around said circuit.

Preferably, the conveying means includes a pump.

Preferably, the conveying means is adapted to convey fluid by passive non- mechanical means.

Preferably, the conveying means is adapted to convey fluid in dependence on gravity.

Preferably, the conveying means is adapted to convey fluid in dependence on convection.

Preferably, the apparatus further comprises means for collecting waste fluid produced by the fuel cell.

Preferably, the interconnecting means is adapted to interconnect the collecting means with the cooling means. Preferably, the evaporative cooler is adapted to be exposed directly to the atmosphere.

Preferably, the apparatus further comprises means for transferring moisture from the evaporative cooler to the atmosphere. By providing means for transferring moisture from the evaporative cooler to the environment, the invention enables moisture to be more easily drawn away from the evaporative surface thereby improving the operation of the evaporative cooler.

This important feature is provided independently. According to a further aspect of the inventions, there is provided apparatus for cooling a device powered by a fuel cell and having at least one component which requires cooling, the apparatus comprising an evaporative cooler adapted to be exposed directly to the atmosphere, and means for transferring moisture from the evaporative cooler to the atmosphere.

The evaporative cooler may also include a fan for increasing air flow over the evaporative cooler.

Preferably, the transfer means comprises a formation adapted to promote air flow over the evaporative cooler.

Preferably, the formation includes at least one duct adapted to link the evaporative cooler with the atmosphere.

Preferably, the evaporative cooler is adapted to form part of an outer casing of the device.

Preferably, the cooling means comprises a cooler connected to each of a respective one of the components.

According to a further aspect of the invention, there is provided a device adapted to be powered by a fuel cell, which comprises an apparatus as aforesaid.

Preferably, the device further comprises the fuel cell. According to yet a further aspect of the invention, there is provided a device, which comprises an evaporative cooler adapted to be exposed directly to the atmosphere, and (preferably) means for transferring moisture from the evaporative cooler to the atmosphere.

Preferably, the transfer means comprises a formation adapted to promote air flow over the evaporative cooler.

Preferably, the formation comprises at least one duct adapted to link the evaporative cooler with the atmosphere.

Preferably, the duct further comprises a fan.

Preferably, the device comprises a casing, and wherein the formation comprises at least a pair of orifices provided in the casing, the pair of orifices being adapted to facilitate air flow over the evaporative cooler.

Preferably, the device further comprises a cavity, said cavity being adapted to accommodate the evaporative cooler such that at least a portion of the evaporative cooler is directly exposed to the atmosphere.

Preferably, the evaporative cooler comprises a fan.

Preferably, the device is portable.

According to a further aspect of the invention, there is provided a portable device adapted to be powered by a fuel cell, which comprises an apparatus as aforesaid.

Preferably, the device further comprises the fuel cell.

According to a further aspect of the invention, there is provided a method of cooling a device powered by a fuel cell, the method comprising using waste fluid produced during a chemical reaction in the fuel cell to cool the device. Thus, the invention proposed here uses fuel cell waste water, an inherently highly clean fluid, which evaporates without residue, thereby enabling the evaporative cooler to operate more efficiently. Furthermore when using the capillary effect or wicking to transport fluid to the cooling surface, the cooler does not require active pumping and is inherently self controlling.

The use of high purity waste water from the fuel cell, which is evaporated to cool the heat sources of portable electronic devices, eliminates the need of having a cooling fan thereby reducing energy consumption, manufacturing cost and package space requirements. The high purity of the waste water ensures that the evaporative cooler stays operable during the product life. The cooling water can be transported through wicking without the use of the pump ensuring a self-regulating water supply to the heat source.

In addition, evaporating part of the water reduces the weight of the device by reducing the requirement for water storage. Furthermore the device can be designed more compactly because the tank capacity for waste water collection can be substantially reduced. Energy conversion efficiency can be improved and system cost reduced since water does not have to be pumped actively into a storage tank.

Further features of the invention are characterised by the dependent claims.

The invention extends to methods and/or apparatus substantially as herein described with reference to the accompanying drawings.

Any feature in one aspect of the invention may be applied to other aspects of the invention5, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa.

The invention is now described, purely by way of example, with reference to the accompanying diagrammatic drawings, in which:- Figure Ia shows a laptop including an evaporative cooler and an internal fuel cell; Figure Ib shows a laptop including an evaporative cooler and an external fuel cell; Figure Ic shows a detailed schematic view of part of the laptop shown in Figures Ia and Ib; Figure IcI shows the position of an evaporative cooler within the laptop of Figure Ic, in a first embodiment; Figure Ic2 shows the position of an evaporative cooler within the laptop of Figure Ic, in a second embodiment; Figure Ic3 shows the position of an evaporative cooler within the laptop of Figure Ic, in a third embodiment; Figure Ic4 shows the position of an evaporative cooler within the laptop of Figure Ic, in a fourth embodiment; Figure Id shows the position of the evaporating surface of the evaporative cooler of Figure Ic in alternative embodiments; Figure Ie shows the position of the evaporating surface of the evaporative cooler of Figure Ic in further alternative embodiments; Figure 2a shows a schematic block diagram of the interconnection between a fuel cell and an evaporative cooler; Figure 2b shows a schematic block diagram of a further embodiment of the interconnection between a fuel cell and an evaporative cooler; Figure 3a shows a first embodiment of an evaporative cooler; Figure 3b shows a second embodiment of an evaporative cooler; Figure 3c shows a third embodiment of an evaporative cooler; Figure 3d shows a fourth embodiment of an evaporative cooler; Figure 3e shows a fifth embodiment of an evaporative cooler; Figure 3f shows a sixth embodiment of an evaporative cooler; Figure 3g shows a seventh embodiment of an evaporative cooler; Figure 4a shows a first embodiment of the connection between an evaporative cooler and a component; Figure 4b shows a second embodiment of the connection between an evaporative cooler and a component; Figure 4c shows a third embodiment of the connection between an evaporative cooler and a component. Figure 5a shows a further embodiment of an evaporative cooler; Figure 5b shows part of the evaporative cooler shown in Figure 5a; and Figure 5c shows another part of the evaporative cooler shown in Figure 5a.

In overview, Figures Ia to Ie show the integration of the cooling system or cooling apparatus in a fuel cell powered device, for example a laptop 100 with a screen or upper lid portion 4 (movable between open and closed positions). In Figure Ia the evaporative cooler 1 is mounted within a lower portion 3 of the laptop 100 casing. The air supply to dispose of the moisture from the evaporative cooler 1 is provided by air channels or ducts 2 (shown in Figure Ic), which are open to the ambient through orifices 5 in the lower portion 3 of the laptop 100 casing. The airflow could be generated by natural convection or induced by a fan (not shown). Figures IcI to Ic4 show different variations of the position of the evaporative cooler 1 within the laptop 100.

Figure Ia shows the arrangement of the fuel cell 6 and the evaporative cooler 1 in the lower portion 3 of the laptop 100 casing and its open upper portion 4. The fuel cell 6 is connected to the evaporative cooler 1 by a water pipe 7 with provides liquid waste water from the fuel cell 6 to the evaporative cooler 1.

Figure Ib shows an arrangement where the fuel cell 6 is located outside the lower portion 3 of the laptop computer 100 casing and the waste water from the fuel cell 6 is provided to the evaporative cooler by means of a water pipe 7.

Figure IcI shows a variant, where the evaporative heat exchanger or cooler 1 is mounted so close to the edges of the laptop casing 3 that there are no ducts required and the cooling system can work with orifices 5 in the casing only.

Figure Ic2 shows a variant, where the evaporative cooler 1 is mounted close to one edge of the housing or casing 3. The air inlet is formed by an orifice 5 in the casing 3 while the air outlet is provided by a duct 2 connecting the evaporative cooler 1 via an orifice 5 in the casing 3 to the ambient. Figure Ic3 shows a similar arrangement as Ic2, but in this case the inlet is formed as a duct 2 and orifice 5 while the outlet is formed by an orifice 5 which is connected to the evaporative cooler 1.

Figure Ic4 shows a similar configuration where the evaporative cooler 1 is located remote from both casing edges and there is a duct 2 connecting an orifice 5 in the laptop casing 3 to the evaporative cooler 1 and a water tight duct 2 connecting the evaporative cooler to an orifice 5 in the casing 3.

Figure Id and Figure Ie show various arrangements, where the water evaporating surfaces 8 of the evaporative cooler 1 are mounted in orifices or slots of the laptop 100 or computer casing, thereby allowing the evaporated water to be released directly into the ambient air.

Figure Id shows two alternative embodiments where the cooling surface 8 is mounted horizontally either in an opening in the lid 4 of the lap-top computer or in the lower casing 3 of the laptop computer.

Figure Ie shows two alternative arrangements, where the evaporating surfaces 8 are mounted in openings or slots on the vertical surfaces of the lower casing 3 or the lid 4. A vertical arrangement improves heat and mass transfer by natural convection.

Figures 2a and 2b show variants of the water connection between the fuel cell 1, the wastewater tank or reservoir 10 and the evaporative cooler 1.

Figure 2a shows a connection arrangement, where the evaporative cooler 1 is supplied with water through a side-branch of the wastewater connection 7 between the fuel cell 6 and the wastewater tank 10. The driving force for water flow from the fuel cell 1 to the wastewater tank 10 is provided by a pump 9. The water flow to the evaporative cooler 1 can be shut off with a valve 33.

Figure 2b shows an arrangement where the evaporative cooler 1 is connected with a water line 7 directly to the wastewater tank 10. Figures 3a to 3g show a variety of embodiments of the evaporative cooler 1.

Figure 3a shows an evaporative cooler, which is built up from a base plate with a water distributor 11 and a capillary block 12 of primarily unchanging cross-section. The capillary block 12 contains a multitude of capillary bores 13 connecting the water reservoir in the base plate 11 with orifices 23 on an evaporative surface, which provide the opening to the ambient, where evaporation is taking place.

Figure 3b shows an evaporative cooler 1 in a sandwich construction. Each of the sandwich plates 14 contains a branch system of capillary channels 15. The branch system is closed off laterally by bonding each sandwich plate to its neighbouring plate. Water is supplied through the water supply channel 16 which could be a through-hole on each sandwich plate. Evaporation takes place at the channel openings or orifices 23 representing the interface between ambient air and the channel system.

Figure 3c shows an evaporative cooler 1, which is similar in design to the cooler shown in Figure 3a in which the capillary block 12 is covered with an external porous layer 18, which distributes the water from the orifices 23 of the capillary bores 13 over the entire external surface of the evaporative cooler. The porous layer could be felt, an open cell metal foam or a wire mesh structure.

Figure 3d shows an evaporative cooler 1, which consists of a base block 19 manufactured from a material of high thermal conductivity, a water supply channel 20, a water distribution channel 21 both filled with a porous medium and a external porous layer 18. The bores 21 and 20 are too large in diameter to draw the cooling water by capillary action, rather the structure of the porous medium filling these channel provides sufficient capillary action to transport the fluid to the external porous layer 18 where evaporation of the fluid to ambient air occurs.

Figure 3e shows an evaporative cooler 1, which consists of a finned base block 22 of a material with high thermal conductivity. The finned base block 22 has a multitude of openings 23 to capillary channels, where evaporation of cooling fluid takes place. The corrugations increase the surface area exposed to the ambient air and thereby increase the volume specific heat transfer rate. Figure 3f shows an evaporative cooler 1 in sandwich construction similar to Figure 3b. In contrast to Figure 3b the sandwich plates 24 contain capillary bores 13 which spread out from the central water supply channel 16 without having a network structure. The openings 23 represent the interaction areas between cooling water and ambient air where evaporation takes place. The sandwich plates 24 are mounted on a base 17 that may have a channel that forms part of the water supply channel 16.

Figure 3g shows an evaporative cooler 1, which is built entirely from a porous material 25. This material could be an open-cell metal foam, a compressed wire mesh structure, or a fibre structure, which contains sufficiently small channels or pores to draw water from the water supply to the external surface. The material has to have high thermal conductivity.

Figures 4a to 4c show different arrangements for the thermal connection of the evaporative cooler 1 and the heat source or component 26, which has to be cooled.

Figure 4a depicts a design corresponding to a conductive connection. Here the evaporative cooler 1 is mounted closely thermally linked to the heat source 26 through an interface layer 27. This interface layer could be a bonding material 27, which has the combined function of providing the thermal as well as the mechanical link between the heat source and the evaporative cooler 1. Alternatively the interface layer 27 could be a material (e.g. paste or grease or aluminium block with pasted interfaces), which ensures low thermal resistance between the heat source and the evaporative cooler. The mechanical link between the heat source and the evaporative cooler 1 is provided in this case by alternative means (e.g. snap fit, bolts, bayonet link).

Figure 4b shows a convective arrangement where the evaporative cooler 1 is located remote from the heat source 26. Here heat transfer between these two elements is provided by a thermal connector 28 of low thermal resistance, which could be a heat pipe or a conductive connector.

Figure 4c shows a convective arrangement where the evaporative cooler 1 is located remote from the heat source 26. Here heat transfer between these two elements is provided by a closed fluid circuit consisting of a feed pipe 30 a return pipe 31 a heat exchanger 29 in the heat source 26 and a second heat exchanger 32 in the evaporative cooler. The flow in the cooling circuit could either be provided by a pump or by gravity flow. The cooling medium in the closed fluid circuit could be in liquid phase only or evaporate in the heat exchanger 29 in the heat source 26 and condense in the heat exchanger 32 in the evaporative cooler 1.

Figures 5a to 5c show further embodiments of an evaporative cooler 1.

Detailed Description of the Drawings In an embodiment, wastewater from generating electricity in a fuel cell 6 from hydrogen and air or methanol and air is used to cool heat emitting components 26 of a portable electronic device by evaporation. In contrast to the prior art, the proposed evaporative cooling is using evaporation in an open cycle with the evaporated liquid being lost to atmosphere rather than condensed and recycled. Open cycle evaporative cooling is commonly known from the biosphere where sweat glands releasing liquid to the skin surface and evaporation of the liquid is providing effective cooling to control the body temperature.

The problem of evaporative cooling is that any contamination of the evaporating liquid, which will not evaporate will lead to increased fouling of the evaporative cooler. By the use of fuel cell waste water proposed in this invention a high purity liquid is used, which is inherently evaporating with negligible residue, thereby keeping the evaporative cooler clean over a long period of time.

Waste water from fuel cells, specifically fuel cells containing a proton exchange membrane is inherently clean because the membrane selectively allows diffusion of H+ ions from the anode to the cathode only. The H+ ions react at the cathode side with the oxygen content of the air to produce water vapour. Thereby any water produced at the cathode is of high purity.

It can be calculated that for a methanol fuelled fuel cell with an efficiency of a typical electrical system of 23%, a methanol fuel flow of around 0.202 g/s is required to generate 1 kW electrical power output. According to the reaction stoichiometry (CH3OH + 3/2 O2 => CO2 + 2 H2O) this fuel flow corresponds to a water flow of 0.227 g/s per kW electrical power output. Assuming an operational temperature of the fuel cell of 50 C around 28% of this water would be released in vapour form with the exhaust gas (mainly nitrogen) from the fuel cell, while 72% of water would be available in liquid form as water supply to the proposed evaporative cooler. The latent heat of this water flow corresponds to 394 W of cooling power available per 1 kW electrical output from waste water evaporation alone.

Hydrogen fuelled fuel cells are typically of a higher efficiency. When assuming 40% of efficiency the available cooling power from waste water evaporation for a hydrogen fuelled fuel cell is 296 W per kW electrical power produced.

This means if 30-40% of the electrical energy produced by a fuel cell is dissipated as thermal energy at an elevated temperature level in an electronic device, this heat can be removed by evaporation of the waste water available. Taking a laptop computer as an example for a portable electronic device, the highest heat flow per unit area is typically generated by the central processing unit (CPU), which dissipates about 30% of the supplied electrical power. Therefore the evaporative cooler would be ideally suited to cool the CPU. One of the benefits of the invention is that the waste water flow is directly proportional to the amount of electricity generated, which is closely linked to the heat generated in the electronic components enabling a self-controlled mode of operation.

Figure Ia shows an embodiment of the invention where the fuel cell 6 as well as the evaporative cooler 1 are mounted within the casing of the electronic device, here a laptop computer 100. The evaporative cooler 1 receives its water through a pipe 7 connecting the cooler 1 with the fuel cell 6 assembly. The pipe 7 could be hollow, requiring a pump 9 to transport the water from the fuel cell 6 assembly to the evaporative cooler 1, or could be filled with a porous or fibrous medium and draw water from the fuel cell to the evaporative cooler by capillary action.

If the fuel cell 6 assembly is located outside the casing of the electronic device (or laptop 100), the water has to be supplied to the evaporative cooler through an external connector as shown in Figure Ib.

In Figures Ia and Ib the evaporative cooler 1 is open to the ambient air, thereby allowing the water vapour generated to diffuse into the atmosphere or to be transported away by convective flow.

The evaporative surface 8 of the cooler 1 exposed to the ambient air could be mounted horizontally as shown in Figure Id or vertically as shown in Figure Ie. A vertical arrangement of the area would promote the generation of a convective flow along the evaporative cooler 1 and thereby improve the cooling efficiency.

If the evaporative cooler 1 should be mounted within the casing of the electronic device, fresh air has to be provided to the cooler 1 and the more humid and warmer air has to be disposed of to the atmosphere. Figures IcI to Ic4 shows a number of variants as to how to arrange the air inlet and outlet via a prior art orifice 5 and ducts 2. On the outlet side it is important that the channel is water tight to prevent any condensate which might occur during warm-up to enter water sensitive areas of the device (or laptop 100).

Minimising the length of the air outlet channel as in Figure IcI and Ic3 would reduce the risk of condensate generation. Any of the variants shown in Figures IcI, Ic2, Ic3 and Ic4 could be combined with a fan in the inlet or outlet duct to improve the air throughput. Alternatively the inlet could be located lower than the air output thereby generating a buoyancy driven flow.

In currently proposed fuel cells for portable electronic devices the water generated is collected in water tanks, if not expelled with the exhaust gases. In this embodiment of the invention a water tank might still be required since it might not be guaranteed that all the water generated can be evaporated in the evaporative cooler. This is the case if the device is operated repeatedly for a short period of time. In this case, a substantial amount of electrical energy is consumed, but the thermal inertia of the heat emitting devices and the evaporative cooler would prevent the evaporative cooler to reach its steady state operational temperature, thereby leading to a reduced rate of evaporation.

There are a variety of ways how the fuel cell, the water tank and the evaporative cooler could be connected. Figures 2a and 2b show two exemplary embodiments. In Figure 2a, the evaporative cooler 1 is connected as a side branch to the water pipe 7 connecting the fuel cell 6 and the water tank 10. The pump 9 is providing a positive pressure to transport the fluid to the tank 10 and the evaporative cooler 1. The valve 33 can prevent or reduce the flow of cooling liquid to the evaporative cooler 1. This might be useful if a portable electronic device is taken to low pressure environments (e.g. during air travel) and the pressure within the water system might force liquid water out of the evaporative cooler leading to external water leakage or if the cooler should operate at a higher temperature level.

In the embodiment shown in Figure 2b the evaporative cooler 1 is linked directly to the water tank 10. This has the benefit, that previously generated water is accessible to the cooler and short term heat spikes, which are not directly linked to electricity output spikes from the fuel cell could be cooled effectively. Situations like this could be envisaged if the fuel cell 6 is combined with battery electricity storage. Thereby the electricity consumption is to some degree de-coupled from the electricity generation by the fuel cell. The configuration in Figure 2b is shown without a pump. The driving force could be provided by capillary action by filling the water pipe 7 with a porous or fibrous medium. Any other permutation of system with or without pump and with or without valve is possible.

The evaporative cooler 1 should effectively allow liquid water to be evaporated, while preventing liquid water to leak to the ambient. In the invention this is achieved by using capillary action as transporting force for at least part of the fluid path from the fuel cell 6 waste water supply to the evaporating surface 8 of the evaporative cooler 1.

In an embodiment the waste water tank or store 10 is in the form of an expandable bag.

Figures 3a to 3f show a variety of embodiments of the evaporative cooler 1. In the cooler 1 shown in Figure 3a the base plate allows distribution of the incoming water to a multitude of capillary bores 13, the water is transported by capillary action to the orifices 23, where the water/air interface stabilises and the water evaporation takes place. The system is self-regulating since any water evaporating increases the capillary force and leads to water being transported up the capillary bores 13. The effect used here is very similar to water transportation and evaporation through stomata in plants. The material of the capillary block 12 should have high thermal W 21

conductivity, since the heat input into the cooler is typically through the base plate, while the evaporation occurs at the orifices. Optimum performance can be achieved if the temperature difference between the area of heat input and the area of evaporation is minimised. 5 Figure 3b shows an embodiment, where the evaporative cooler is built up from multiple layers or plates 14 sandwiched together. Each layer 14 has cut out a channel profile 15 on one or both layer lateral surfaces. The channels 15 are laterally closed by bonding the layers together. One or a multitude of water supply channels 16 is 10 provided by a through hole in each layer 14. The channel 15 structure is of branch structure similar to the capillary channels supplying stomata in a plant leaf with water. The channel dimensions have to be small enough to ensure liquid transport to the orifices 23 by capillary action. The benefit of this approach is that low cost mass manufacturing by surface etching of the channels is possible. 15 In any of the embodiments 3a, 3b, 3e or 3f the surface area available for evaporation equates to the sum of the areas of the channel orifices 23. And therefore it is desirable to maximise the proportion of the cooler 1 surface area covered by orifices 23. The embodiment shown in Figure 3c covers a part or the whole external surface 20 of the evaporative cooler 1 with a thin layer of a porous medium 18. This medium could be felt, compressed wire mesh or open cell metal foam. The benefit of this is that any cooling liquid transported by capillary action to the orifices 23 will be transported further by capillary action across the felt layer. Therefore all of the surface covered by the porous medium 18 will be available for evaporation and 25 cooling. The layer would be preferably thin to make sure that there is not a substantial temperature drop from the capillary block to the external surface of the porous layer where evaporation occurs.

Figure 3d shows a similar arrangement as Figure 3c with the difference that the 30 cooling liquid supply occurs through one or several channels 21 of larger dimension. Capillary transport of the fluid along these channels is ensured by filling these channels with a porous medium (e.g. felt, metal foam, wire mesh). In this case conventional fabrication of the base block with macroscopic channels is easily possible. 35 Figure 3e shows an embodiment where the available surface area per unit volume is maximised by giving the evaporative cooler 1 a fin structure.

Figure 3f shows an embodiment of similar channel construction as 3b but different to 3b there is no branching of the channels 13 within each layer 24. The layers 24 are bonded to each other as well as to a base plate 17, which contains part of the water supply channel 16.

Figure 3g shows an embodiment where the entire evaporative cooler 1 is made up from a porous medium 25. The pores in this medium have to be of suitable size to allow transport of the cooling liquid to the external surfaces by capillary action. The porous medium 25 could be a felt, open cell metal foam or compressed wire mesh. It would be again desirable for the base material to be of high thermal conductivity to bring the external surface temperature close to the temperature of the device that is generating the heat.

Figures 5a to 5c show a further embodiment of an evaporative cooler 1. In this embodiment an assembly of aluminium fins 34 having a network of capillary channels 15 etched therein are sandwiched together to create a multitude of capillary channels (or micro-channels) through which water may be transported. Each capillary channel 15 terminates in a pore or orifice 23 on the upper surface 8 of the evaporative cooler 1. Spacer elements 36 are positioned intermittent the layers or fins 34. The fins 34 are positioned back to back so that the capillary channels face outwardly in each respective fins 34 pair. A continuous water supply channel 16 is formed along the length of the evaporative cooler 1 by bores 16' provided in each of the fins 34 and spacer elements 36.

It can be seen from Figure 5a that the fins or layers 34 extend above the level of the spacer elements 36, thereby providing the evaporative cooler 1 with a finned upper surface, which may further enhance the cooling efficiency of the evaporative cooler 1.

The upper surface 8 of the evaporative cooler 1 presents a large surface area from which evaporation can occur, and the net effect of the sandwich of layers 34 each having multiple capillary channels 15 results in the evaporative surface having a multitude of pores 23.

The evaporative cooler 1 is held together by bolts that pass through holes 35 in the layers 34 and spacer elements 36. The evaporative cooler 1 may be covered with a porous cloth to increase the surface area for evaporation. The fins or layers 34 and spacers 36 may also be manufactured from a metal other than aluminium, and conduct heat to the evaporation surface 8.

Beside the thermal resistance in the evaporative cooler 1, the design of the thermal linkage between the heat producing device, which is to be cooled, and the evaporative cooler 1 is of great importance for the cooling performance of the system. Figures 4a to 4c show a variety of solutions for thermally linking the evaporative cooler 1 to the heat source or component 26. In Figure 4a, the heat transfer mechanism used is conduction. The cooler 1 is linked by a highly conductive interface layer 27. A thin layer or the use of high conductivity material for the layer (e.g. copper, aluminium) can ensure good thermal conduction. The interface layer 27 could be made up from a bonding material which provides a mechanical as well as a thermal link. Alternatively the mechanical link could be provided by separate means (e.g. bolts, clips, press fit) and a highly conductive paste, grease, or other material could be used to reduce thermal contact resistance and improve thermal conduction.

In Figures 4b and 4c, convective heat transfer provides the thermal link between the evaporative cooler 1 and the heat source or component 26. Figure 4b illustrates a two-phase closed circuit such as a heat pipe. Here a liquid would be evaporated by the heat source and subsequently condense in the evaporative cooler.

Figure 4c illustrates a single-phase closed convective circuit. Both of them could rely on natural convection as well as pump driven forced convection to ensure the convective flow in the circuit.

If the fuel cell is switched off or removed completely, perhaps when fuel runs out and power is drawn from a conventional external mains power supply, the cooling of the CPU could be achieved by a conventional fan integrated into the power supply. The power supply could attach to the laptop adjacent to a duct and draw air through it in the same way as a conventional CPU fan. A docking station could be used if the fuel cell is switched off in a stationary office environment, and a conventional fan could be integrated into the docking station.

In use, in an embodiment, waste water produced during the chemical reactions which occur in the fuel cell 6 is channelled into a waste water tank or reservoir 10, where it is stored. This tank is connected to the evaporative cooler 1 by means of a water line 7. The evaporative cooler is in turn connected, as described above, to a component 26, say, a microprocessor, which requires cooling.

Initially, any water contained within the water line 7 that enters the water supply channel 16 of the evaporative cooler 1 is drawn up the capillary channels 15 due to capillary action (wicking). Once the water reaches the upper surface 8 of the evaporative cooler 1 it forms droplets over the large evaporative surface 8 of the cooler 1 which then evaporate. As the component heats up, thereby heating up the body of the evaporative cooler 1, the rate of evaporation at the surface 8 increases thereby drawing (or sucking) further water up the capillary channels 15. Thus, the evaporative cooler 1 regulates the flow of water from the water supply channel 16 to the surface 8 of the evaporative cooler 1 in dependence on the temperature gradient between ambient and the temperature of the component 26. The cooler is thus self- regulating, since the flow rate through the capillary channels is dependent on the temperature of the component 26 being cooled, and only as much water as required for cooling the component is drawn up the capillary channels 15.

The water storage tank 10 or water line are typically initially filled with at least some fluid so as to enable the evaporative cooler 1 to cool components, if required, even before energy has been consumed by the device and, hence, waste water produced by the fuel cell. In this regard, in the case where the device runs off mains power, cooling using the evaporative cooler 1 is still possible so long as the water tank 10 is supplied with purified water, or a similar cooling fluid.

Thus, it will be apparent that the capillary channels 15 (or tubes) control the pressure in the water supply channel, and thereby regulate the flow of water or fluid through the evaporative cooler. Furthermore, the fluid or water flow path defined between the fuel cell (or storage tank or waste water outlet) and the capillary tubes is closed and suitably at a different pressure to atmospheric pressure (hence for example there is no opening to atmospheric at any of the junctions between the feed(s) to the evaporative cooler and the evaporative cooler itself, and more particularly the feed(s) open to the capillary tubes in the evaporative cooler by way of a sealed manifold). Thus, the capillary channels are able to control the drawing of fluid from the fuel cell (or storage tank or waste water outlet) and up the capillary channels, by controlling the pressure in the closed, sealed, fluid path. Furthermore, as the component heats up, the rate of evaporation on the evaporative surface will increase, thereby causing the rate of fluid flow through the capillary channels 15 to increase.

It should be noted that the water storage tank may be located anywhere in the fluid flow path defined between the fuel cell waste water outlet and the inlet to the evaporative cooler; for example, the storage tank 10 may be proximate the fuel cell (or even form part of the fuel cell), or may be located anywhere along the water line between the fuel cell and the inlet to the water supply channel 16 of the evaporative cooler. The closed capillary path may start before or after the storage tank.

Thus, the evaporative cooler is able to control the cooling of the component more efficiently. Furthermore, excess waste water produced by the fuel cell 6 is only drawn from the water store 10 as required, and is otherwise stored in the water tank 10. In addition, the fact that the waste water produced by the fuel cell is of a high purity means that the efficiency of evaporative surface is not affected by evaporative residue.

In summary, the invention enables the use of wastewater produced as a by-product in fuel cells for cooling purposes in an evaporative cooling device, which is passively self-regulating. A typical application would be in portable electronic devices.

It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination. Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.