Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/08—Fuel cells with aqueous electrolytes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/08—Fuel cells with aqueous electrolytes
  • H01M8/083—Alkaline fuel cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
  • H01M8/2457—Grouping of fuel cells, e.g. stacking of fuel cells with both reactants being gaseous or vaporised
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
  • H01M8/2459—Comprising electrode layers with interposed electrolyte compartment with possible electrolyte supply or circulation
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
  • H01M8/2465—Details of groupings of fuel cells
  • H01M8/2483—Details of groupings of fuel cells characterised by internal manifolds
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells

Definitions

• the present invention relates to liquid electrolyte fuel cells, preferably but not exclusively alkaline fuel cells, and to the arrangement of such fuel cells in stacks .
• Fuel cells have been identified as a relatively clean and efficient source of electrical power. Alkaline fuel cells are of particular interest because they operate at relatively low temperatures and have a high theoretical efficiency compared to other fuel cell technologies. Acidic fuel cells and fuel cells employing other aqueous electrolytes are also of interest. Such fuel cells operate at a voltage of usually less than one volt (typically 0.5-0.9 V). To achieve higher voltages, fuel cells are typically arranged in stacks. Fuel cells employing a liquid electrolyte typically comprise an electrolyte chamber that is separated from a fuel gas chamber (containing a fuel gas, typically hydrogen) and a further gas chamber (containing an oxidant gas, usually air) .
• a fuel gas chamber containing a fuel gas, typically hydrogen
• a further gas chamber containing an oxidant gas, usually air
• the electrolyte chamber is separated from the gas chambers using electrodes that are gas permeable, and carry a catalyst such as platinum.
• a catalyst such as platinum.
• the electrolyte may be circulated through the electrolyte chambers from headers or distribution ducts, so that the electrolyte flows through all the cells are in parallel.
• a problem with such an arrangement is that there will be some electrical (i.e. ionic) leakage current between one cell and another through the electrolyte in the headers or distribution ducts. This can be minimised by designing the electrolyte flow paths to raise their ionic resistance, but this measure cannot eliminate the ionic leakage currents altogether.
• Another problem with such fuel cell stacks is to ensure uniformity of pressure and mass flow rates between the cells and within every cell.
• a fuel cell stack comprising a plurality of fuel cells each with a chamber for electrolyte with at least one inlet and at least one outlet, and at least one header to supply electrolyte to all the cells in parallel, and means to collect electrolyte that has flowed through the cells, wherein for each cell the or each outlet for electrolyte communicates with an electrolyte flow channel arranged such that in use there is a free surface of electrolyte within the electrolyte flow channel, the electrolyte flow channel being separate from the
• electrolyte flow channels for other cells, but such that the free surfaces of all the electrolyte flow channels are at a common pressure.
• electrolyte flow channels may be referred to as open channels.
• Each such open electrolyte flow channel may include means to break up the flow into droplets.
• the flow may pass over a projecting lip from which the electrolyte falls freely to a collection means, and in that case there may also be a baffle onto which the falling electrolyte impacts, to help break it up.
• the electrolyte may flow through a multiplicity of apertures to emerge as streams of
• the outlet from each cell communicates with the open electrolyte flow channel at an upper surface of the cell stack, and the open electrolyte flow channel also defines a weir to ensure that, in use, the electrolyte fills the channel to a consistent depth before overflowing. This ensures that the pressures at all the outlets are equal, which helps ensure uniform pressure throughout any one cell, and between all the cells.
• the open electrolyte flow channel may form the uppermost part of the electrolyte chamber, but preferably the electrolyte chamber communicates via a plurality of outlet channels with the open electrolyte flow channel.
• the electrolyte is fed from the header into the cell through a long narrow flow channel, for example with a cross-sectional area less than 2 mm 2 , for example 1 mm 2 , and of length greater than 50 mm, for example between 75 mm and 150 mm, such as 100 mm.
• baffles to enhance flow uniformity within the chamber, for example transverse notched baffles to diffuse the electrolyte flow from each inlet.
• the fuel cell stack must also be supplied with the fuel gas and the oxidant gas. These may be supplied through header ducts within the stack.
• the air chambers may communicate directly with the surrounding air.
• air may be allowed to enter each a chamber through one or more entry channels communicating with the faces of the stack, for example the side or bottom face.
• the air is arranged to be at a higher pressure than the electrolyte, that portion of the cell stack provided with the air entry channels being enclosed within a plenum to which air is supplied at an elevated pressure. This avoids the requirement for there to be any air header ducts defined through the plates making up the stack, and so simplifies the structure of the plates.
• Figure 1 shows a cross-sectional view perpendicular to the cell plane through a fuel cell stack of the
• Figure 2 shows a cross-sectional view parallel to the cell plane of a container enclosing the fuel cell stack of figure 1 ;
• Figure 3 shows a plan view of an electrolyte plate of the fuel cell stack of figure 1;
• Figure 4 shows a plan view of an air plate of the fuel cell stack of figure 1.
• FIG 1 there is shown a sectional view of a fuel cell stack 10, with the components
• the stack 10 consists of a stack of frames 62, 63 and 64, each being of an insulating plastics material, and each defining a rectangular through-aperture.
• Alternate frames 62 provide electrolyte chambers (marked K) , and between successive electrolyte chambers are gas chambers, which are alternately air chambers (marked 0) and fuel chambers (marked H) . All the chambers are separated from neighbouring chambers by electrode elements 70 with permeable portions adjacent to the electrolyte chambers K, and with impermeable
• each electrolyte chamber K is between an oxygen chamber 0 and a fuel chamber H, and is separated from them by a cathode 19 and an anode 18 respectively, these
• polar plates 65, 66 that define blind recesses, and there are end electrodes, an anode 18 at one end and a cathode 19 at the other end, which do not form components of a pair.
• Gaskets (not shown) ensure that the frames 62, 63 and 64 are sealed to the electrode elements 70.
• the anodes 18 and the cathodes 19 have a catalyst coating which may be on the surface facing the respective gas chamber H or 0, or on the opposite surface.
• the catalyst coatings for both cathode and anode electrodes may use a combination of catalyst particles and a binder.
• the coating on the cathodes 19 might comprise 10% Pd/Pt or silver on activated carbon, while the coating on the anodes 18 might comprise 10% Pd/Pt on activated carbon, in each case with 10% binder.
• the cell stack 10 is mounted within a container 12 which defines a horizontal shelf 14 around its periphery which divides it into a lower part 12a and an upper part 12b.
• the frames 62, 63, 64 that make up the cell stack 10 have a step 15 on each side, as do the end plates 65 and 66, so that the lower part is slightly narrower than the top part.
• the lower part of the cell stack 10 fits in a rectangular space defined by the shelf 14, and the upper part of the cell stack 10 is sealed to the shelf 14 around its periphery.
• Air is supplied from a pump (not shown) through a duct 20 into the lower part 12a, to flow through the air chambers 0 and to emerge into the upper part 12b, from which it is released through an exhaust duct 22.
• the liquid electrolyte is supplied to one end of the stack 10, and (as explained below) after flowing through the electrolyte chambers K collects on the top of the shelf 14 to flow out through an outlet duct 24.
• the fuel gas (hydrogen) is also supplied to one end of the stack 10, and the return duct is also connected to that end of the stack 10.
• FIG 3 there is shown a plan view of a frame 62 that defines an electrolyte chamber K.
• electrolyte is supplied to all the electrolyte chambers K in the stack 10 through
• each aperture 30 communicates through a long narrow groove 32 with the edge of the electrolyte chamber K; the grooves 32 at each corner are slightly narrower.
• the electrolyte emerges from the chamber K at the top through several parallel grooves 34 that lead to the top edge of the frame 62.
• baffles 35 there are baffles 35 that extend
• baffles 35, 36, 37 provide a substantially uniform electrolyte flow throughout the chamber K; during operation it
• electrolyte level fills up to just above the top of each raised portion 38, in the open-topped channel that is defined between the adjacent electrode elements 70, which as mentioned above both project above the top of the frame 62. Consequently there is a constant depth of about 2-3 mm of electrolyte above the top of the frame 62 with a free surface of electrolyte exposed to the air pressure within the upper part 12b of the container 12, and the electrolyte then flows continuously over the raised portions 38 and over the lips 39. The electrolyte may then trickle down on the outside of the frame 62 as a thin stream, or fall freely, possibly forming drops, to collect on top of the shelf 14.
• FIG 4 there is shown a plan view of a frame 63 that defines an air chamber 0.
• the lower part 12a of the container 12 acts as a plenum, and enables air to be supplied directly to each air chamber 0 through the respective frame 63, rather than being supplied through a distribution channel in the stack.
• the lower half of the frame 63 defines several grooves 52 on each side which communicate with the lower half of the chamber 0.
• the frame 63 also defines baffles 54
• the multiple inlet grooves 52 ensure that the pressure within the chamber 0 is only slightly less than the pressure within the lower part 12a of the container 12.
• the air flows through the chamber 0, to emerge via narrow S-shaped grooves 56 which communicate to near the top corners of the chamber 0, so the air flows out into the top part 12b of the container 12.
• the air flow rate was approximately 3 litres/min to each air chamber.
• chambers K, 0 and H may have a different shape to that shown here; and the outlet from the electrolyte chamber K may be through one or more wide grooves or slots in place of the several narrow grooves 34.
• the electrolyte chamber K may be filled with a porous material or a mesh which acts as a wick.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Fuel Cell (AREA)

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Citations (4)

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• 2010
  • 2010-05-11 GB GBGB1007858.2A patent/GB201007858D0/en not_active Ceased
• 2011
  • 2011-05-09 EP EP11718772.4A patent/EP2569815B1/en active Active
  • 2011-05-09 CA CA2790530A patent/CA2790530C/en active Active
  • 2011-05-09 AU AU2011251783A patent/AU2011251783B2/en not_active Ceased
  • 2011-05-09 JP JP2013509618A patent/JP5866716B2/ja not_active Expired - Fee Related
  • 2011-05-09 WO PCT/GB2011/050887 patent/WO2011141727A1/en not_active Ceased
  • 2011-05-09 KR KR1020127026938A patent/KR101891491B1/ko not_active Expired - Fee Related
  • 2011-05-09 US US13/695,453 patent/US9083025B2/en active Active

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