WO2014177207A1 - Échangeur de chaleur dans un empilement de pile à combustible à oxyde solide (sofc) - Google Patents

Échangeur de chaleur dans un empilement de pile à combustible à oxyde solide (sofc) Download PDF

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Publication number
WO2014177207A1
WO2014177207A1 PCT/EP2013/059065 EP2013059065W WO2014177207A1 WO 2014177207 A1 WO2014177207 A1 WO 2014177207A1 EP 2013059065 W EP2013059065 W EP 2013059065W WO 2014177207 A1 WO2014177207 A1 WO 2014177207A1
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WO
WIPO (PCT)
Prior art keywords
stack
heat exchanger
solid oxide
oxide fuel
fuel cell
Prior art date
Application number
PCT/EP2013/059065
Other languages
English (en)
Inventor
Claus FRIIS PEDERSEN
Original Assignee
Topsøe Fuel Cell A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Topsøe Fuel Cell A/S filed Critical Topsøe Fuel Cell A/S
Priority to PCT/EP2013/059065 priority Critical patent/WO2014177207A1/fr
Publication of WO2014177207A1 publication Critical patent/WO2014177207A1/fr

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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
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • H01M8/04067—Heat exchange or temperature measuring elements, thermal insulation, e.g. heat pipes, heat pumps, fins
    • H01M8/04074—Heat exchange unit structures specially adapted for fuel cell
    • 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
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M2008/1293—Fuel cells with solid oxide 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
    • H01M8/002—Shape, form of a fuel cell
    • H01M8/006—Flat
    • 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
    • H01M8/247—Arrangements for tightening a stack, for accommodation of a stack in a tank or for assembling different tanks
    • H01M8/248—Means for compression of the fuel cell stacks
    • 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

  • Solid Oxide Cells are used for a wide range of purposes including the generation of electricity from different fuels (fuel cell mode) and the generation of synthesis gas (CO + H2) from water and carbon dioxide (electrolysis mode) .
  • the solid oxide stacks typically operate at temperatures in the range from 600 to 1000 °C . At these temperatures reduction of heat loss is essential to obtain a good efficiency.
  • Thermal insulation is used to reduce heat loss to the environment and heat exchangers are used to transfer heat from the outlet gas flows to the inlet gas flows.
  • Heat exchangers are therefore critical components in almost any solid oxide stack system (SOSS) and it is essential to optimise these to enhance heat transfer and reduce heat loss.
  • This invention relates to the design and integration of thermally matched heat exchangers and their integration with solid oxide stacks and systems to enhance the overall efficacy of these systems.
  • a parameter called the x hot surface area' can be defined as :
  • T (A) is the temperature for a given area
  • T Ma x is the maximum temperature across the entire area
  • T ext (A) is the temperature of the adjacent components and surroundings external environment
  • ⁇ ⁇ ⁇ ⁇ is the minimum external
  • the x hot surface area' can be interpreted as the actual surface temperature difference integrated for the entire device area and
  • the active area measures 8 cm x 8 cm x 12 cm giving it a surface area of 500 cm 2 .
  • the temperature of the heat exchanger however varies (linearly) from the maximum temperature to the cold input temperature. If the cold input temperature is similar to the external temperature, then the hot surface area of the heat exchanger is 250 cm 2 . This number does not include the manifolding and the piping which adds additional 250 cm 2 of hot surface area.
  • the stack (without enclosure and compression system) measures 12 cm x 12 cm x 10 cm and has a (hot) surface area of 750 cm 2 .
  • EP1602141 is an example of such a proposed invention and reveals a Solid Oxide Stack System that is modularly built, wherein the additional components such as the heat exchangers are directly arranged in the high-temperature fuel cell stack to avoid piping.
  • cold air (viz) is being preheated by exchanging heat with warm off gas (abgas) coming from a post-combustion
  • Fig. 3 also indicate hot areas with x black' colour and cold areas with x white' colour.
  • Fig. 2 indicates flow transfer also at the hot/cold interfaces A and B, which are therefore not free to move. Consequently, the invention of EP1602141 is only suited to deliver the desired flows and provide the desired reduction in piping and manifolding surface areas for relatively low values of inlet/outlet temperature differences ( ⁇ ) .
  • thermally matched is here understood that the thermal gradients of the heat exchanger are oriented in the same direction as those of the adjacent stack components. This can also be expressed as a criterion that the maximum temperature difference ⁇ between two adj acent /touching points of the heat exchanger and the adjacent components is substantially smaller than the maximum temperature difference ⁇ across the heat exchangers, please refer to Fig. 4.
  • Such heat exchangers have the advantages of being able to practically eliminate the heat loss from manifolding and piping. Furthermore, they can also be used to:
  • Fig. 5 One example of an embodiment (Hex A) of thermally matched heat exchanger is shown in Fig. 5.
  • the heat exchanger is in principle a x bended' counter flow plate heat exchanger. The flow propagates from one side ( x left' or x right' ) to the other side ( x right' or x left' ) and at the left and right edges, the flow is directed to another layer in the heat exchanger and the flow direction is reversed.
  • a thermally insulation layer is inserted between each x layer' of the heat exchanger. This layer could for example be just a hollow section using still air as insulation material.
  • the number of layers ⁇ ⁇ ' used in such a heat exchanger is determined by the maximum acceptable temperature difference ⁇ . As each layer handles 1/Nth of the overall temperature difference ⁇ , N can be expressed as N > ⁇ / ⁇ .
  • the heat exchanger proposed here is not only characterised by eliminating the heat loss from manifolding and piping, but it also have a very low effective surface area when integrated into solid oxide stack systems.
  • this equation 1 shows that if T (A) - T ext (A) is low for a given surface, then the effective hot surface area from this surface is also low. This basically indicates that if two hot surfaces are placed face to face, then the heat loss of both can be eliminated.
  • this heat exchanger can become an integrated part of the stack compression system and help to reduce the heat loss from the compression system, which in most solid oxide stack systems are substantial. Due to differences in thermal expansion coefficients between different stack components (e.g. cells and interconnects), external compression systems are typically applied to the two endplates of the stack.
  • One example of heat loss from a compression system is shown in Fig. 7 and used for the system in Fig. 1.
  • a steel shield is used to provide the stack compression.
  • the steel shield is bolted to a bottom plate and provides the compression pressure through the stack through a compression mat.
  • this compression mat has a relatively high thermal conductivity
  • the steel shield has the same temperature as the stack inside.
  • the surface area of the steel shield is 2000 cm2 or almost 3 times higher than the surface area of the stack. This implies that the hot
  • a very attractive alternative would be to use the proposed embodiment of a stack integrated thermally matched heat exchanger as an integrated part of the compression system.
  • a Solid Oxide Stack System configuration which is very popular when several stacks are need is the so-called 'boxer' configuration. Here two stacks are placed on top of each other with a centre manifold and compression provided from the two ends as shown in Fig. 8a and 8b.
  • One advantages of the 'boxer' configuration is that two hot stack surfaces are facing each other, thereby reducing the system heat loss compared to a configuration with two individual stacks.
  • compression from the two ends can be used to compress the two stacks simultaneously. This is shown for a standard
  • Fig. 8a An alternative and attractive configuration is shown in Fig. 8b.
  • the proposed heat exchanger Hex a
  • the heat exchangers have hot end surfaces towards the stacks and cold end surfaces opposite the stacks towards the compression systems.
  • Such heat exchangers could provide cold interfaces for the compression system and thereby in practise eliminate the heat loss from the compression system.
  • the electrical wiring is connected to the hot bottom and top-plates of the stacks as indicated in Fig. 9A. To reduce the ohmic losses of these wires they typically have a relatively broad cross section and hence a considerable thermal conductivity.
  • the compression system has to be electrically grounded, which leads to relatively high voltages between the end stack facets and the compression system, point I) and II) in Fig. 9b.
  • Hex A heat exchanger can be assembled in the same assembly processes used for assembling the stacks.
  • Hex A can be
  • the heat exchanger can be assembled by the same process (e.g. robot controlled stacking) as the fuel cell stack and the heat exchanger elements can be joined by the same methods used for the stack, e.g. glass soldering, Ni-brazing or diffusion bonding.
  • metal components for the heat exchangers it is assured that they as generally desired are electrically conductive .
  • FIG. 10 Another preferred embodiment of thermally matched, stack integrated heat exchangers is shown in Fig. 10. This is a preferred embodiment of thermally matched, stack integrated heat exchangers.
  • thermally matched stack integrated heat exchanger is placed at one of the sides of the stack and uses a counter flow plate heat exchanger configuration.
  • the cold inlet is connected to the top of the heat exchanger at the x cold' right side and the hot x left' side of the heat exchanger faces the stack.
  • the hot flow between the stack and the heat exchanger goes through a manifolding plate at the bottom of the stack.
  • Hex B can be separate from the stack and for example an external heater can be inserted between Hex B and the stack.
  • Hex B can also be an integrated part of the stack and for example share components such as spacers and interconnects. This will require electrically insulating parts to be included in the heat exchanger design as described in the following.
  • Fig. 11 shows an embodiment of this invention, where the heat exchanger is realised from stack components by extending the length of interconnects and spacers.
  • every other set of heat exchanger plates (corresponding to the extensions of the cells) have to be based on a material which is electrically nonconductive in the vertical direction. This could for example be a ceramic plate or a ceramically coated metal sheet.
  • the two sets of heat exchanger plates can be separated by extended spacers, which are also used to lead the desired flows across the different heat exchangers plates.
  • the heat exchanger plates of Hex B can be assembled in exactly the same process as the stack and similar methods can be used for joining the heat exchanger and stack components.
  • Such joining methods could for example be glass sealing/soldering, brazing or diffusion bonding.
  • Hex B also can also have a low hot surface area.
  • the heat exchanger is assumed to have inlet and outlet flow temperatures of 25 and 50°C,
  • the Hex B heat exchanger can also be realised with low electrical resistance. Every other heat exchanger plate can be realised as a metal plate and thereby be electrically conductive. This makes it possible for example to have cold electrical connections to the top or bottom plates of the stack from the top or bottom plate on the heat exchanger.
  • a very interesting feature of this heat exchanger embodiment is that it is possible to have cold electrical connections to each interconnect in the stack. This can be used to provide a cold environment for electrical components used to control the current through individual cell or groups of cells. Such current control can for example be used to adjust the current over individual cells or cell groups in order to obtain very high fuel utilisations for all cells or cell groups in a stack. Another application could be to switch off the current in SOEC mode for cell or cell groups with defect (leaking) cells. This would avoid the excessive heating of defect cells to destroy adjacent cells.
  • the proposed heat exchanger embodiments can be used in many configurations to realise different SOFC, SOEC and even combined SOFC/SOEC configurations.
  • One example is shown in Fig. 12.
  • Fig. 12a four stacks are placed close to each other each sharing two hot sides with neighbouring stacks.
  • Each stack is also connected to one Hex A and one Hex B, providing cold external interfaces for all in-plane sides of this configuration. It is furthermore possible to cascade several similar configurations in the out-off-plane direction thereby realising a system with very few hot external
  • Solid oxide stack configurations with two heat exchangers are relevant for both SOEC and SOFC systems. This is exemplified in Fig . 13 and 14.
  • Fig. 13 shows a simple SOEC configuration which can be realised with two (integrated) heat exchangers and a heater.
  • Fuel e.g. H20
  • the cold flow e.g. 101°C steam
  • fuel inlet 1 is heated in Hexla by the hot fuel outlet flow coming from the stack.
  • the cold flow from fuel inlet 2 is heated in Hex2 by the hot oxygen outlet flow from the stack. No inlet flushing of the oxygen side is used and the output from the oxygen side is therefore 100% 02.
  • the two fuel inlets are combined and the temperature of the combined flow is increased in a heater before the fuel fed to the stack.
  • the stack is assumed to operate close to the thermo-neutral point and the temperatures of the output flows will therefore be close to the stack operating temperature.
  • the heat exchangers are not ideal and some heat will be lost to the environment, and these heat losses are compensated by the heater.
  • the main motivation for this configuration is that it makes it possible to balance the inlet thermal mass to the outlet thermal mass for all current levels. This is probably best demonstrated by two examples. Assuming that a 75 cell stack, with a 100 cm2 active area per cell is used. The stack can operate at currents up to 70A with a fuel utilisation up to 70%. In this case the fuel input flow to the stack should be 3.4 Nm3/h (steam) .
  • Fig. 14 shows a simple SOFC configuration which can be realised with two (integrated) heat exchangers.
  • Fuel e.g. H2
  • the cold inlet flow is heated in Hexl by the hot fuel outlet from the stack.
  • the cold air inlet flow is heated in Hex2 by the hot air outlet flow from the stack.
  • FIG. 12b One possible embodiment is shown in Fig. 12b.
  • Fig. 12b Here there are 12 stacks and 14 heat exchangers arranged in a very compact configuration. Using manifolding plates for fuel, air and oxygen distribution, it is possible for several stacks to share one heat exchanger and thereby realise for example the combined SOEC and SOFC system shown in Fig. 15.
  • This configuration is the common denominator of the SOEC and SOFC configurations shown in Fig. 13 and 14.
  • the air inlet and outlets are shut off (on the cold side of Hex3) and the system is operating exactly as the SOEC system in Fig. 13.
  • Hex B type heat exchangers for the air flow (Hex 3) as Hex B type heat exchangers can easily be designed for low pressure drop, which is less simple with the Hex A type design .
  • Hex A type heat exchangers for the main fuel heat exchangers are used in both SOEC and SOFC mode and therefore can provide cold interfaces for the compression system for both operating modes.
  • a solid oxide fuel cell (SOFC) system comprising one or more SOFC stack (s) and one or more stack-integrated, temperature-matched heat exchanger (s) in direct physical contact on at least 1/12, preferably at least 1/6, preferably at least 1/3 of the heat exchanger surface area with the SOFC stack (s), wherein the maximum
  • HSA syste m/HSA sa ⁇ 1 preferably HSA syste m/HSA sa 0.3, preferably HSA syste m/HSA sa ⁇ 0.1.
  • ⁇ difference between the maximum and minimum inlet temperatures of ⁇ > 300°C, preferably ⁇ > 450°C, preferably ⁇ > 600°C.
  • a solid oxide fuel cell system according to feature 1, wherein at least one of the heat exchangers is used for feeding current to the stack (s) or to and from the stack (s) and the at least one of the heat exchangers has an electrical resistance R He x between an cold surface and a stack element of R He x ⁇ 1 mOhm, preferably R He x ⁇ 0.1 mOhm, preferably R He x ⁇ 0.01 mOhm.
  • a solid oxide fuel cell system according to feature 4 wherein the stack element is cells or cell groups and current control of these is performed at cold interfaces of the at least one heat exchanger.
  • a solid oxide fuel system wherein the assembly of the integrated heat exchangers is integrated with the stack assembly, at least one of the heat exchangers share at least an interconnect or a spacer .
  • a solid oxide fuel system according to feature wherein the hot surfaces of the heat exchanger (s) the stack operating temperature or at maximum 50 °C colder .
  • a solid oxide stack system applying at least on heat exchanger according to feature 1, where the thermal management system is designed in a way where the system can operate with high efficiency in both SOEC and SOFC mode .
  • a solid oxide stack system according to feature 12 wherein the thermal management system can operate with as few as three heat exchangers .

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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)

Abstract

L'invention porte sur un système pile à combustible à oxyde solide (SOFC) ayant au moins un échangeur de chaleur intégré qui réduit au minimum la surface chaude de l'échangeur de chaleur et du système.
PCT/EP2013/059065 2013-05-01 2013-05-01 Échangeur de chaleur dans un empilement de pile à combustible à oxyde solide (sofc) WO2014177207A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2013/059065 WO2014177207A1 (fr) 2013-05-01 2013-05-01 Échangeur de chaleur dans un empilement de pile à combustible à oxyde solide (sofc)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2013/059065 WO2014177207A1 (fr) 2013-05-01 2013-05-01 Échangeur de chaleur dans un empilement de pile à combustible à oxyde solide (sofc)

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WO2014177207A1 true WO2014177207A1 (fr) 2014-11-06

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3282513A3 (fr) * 2016-08-11 2018-05-16 General Electric Company Systèmes de pile à combustible multi-piles et ensembles d'échangeur de chaleur

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20040086765A1 (en) * 2002-06-21 2004-05-06 Florence Stephen Fuel cell insulating heat exchanger
US20050089731A1 (en) * 2002-02-05 2005-04-28 Takashi Ogiwara Solid oxide fuel cell system
EP1602141A1 (fr) 2003-03-12 2005-12-07 Forschungszentrum Jülich Gmbh Systeme de piles a combustible haute temperature de structure modulaire
US20090053569A1 (en) * 2007-08-15 2009-02-26 Bloom Energy Corporation Fuel cell system components

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050089731A1 (en) * 2002-02-05 2005-04-28 Takashi Ogiwara Solid oxide fuel cell system
US20040086765A1 (en) * 2002-06-21 2004-05-06 Florence Stephen Fuel cell insulating heat exchanger
EP1602141A1 (fr) 2003-03-12 2005-12-07 Forschungszentrum Jülich Gmbh Systeme de piles a combustible haute temperature de structure modulaire
US20090053569A1 (en) * 2007-08-15 2009-02-26 Bloom Energy Corporation Fuel cell system components

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3282513A3 (fr) * 2016-08-11 2018-05-16 General Electric Company Systèmes de pile à combustible multi-piles et ensembles d'échangeur de chaleur
EP3595067A1 (fr) * 2016-08-11 2020-01-15 General Electric Company Systèmes de pile à combustible multi-piles et ensembles d'échangeur de chaleur
US10862141B2 (en) 2016-08-11 2020-12-08 Cummins Enterprise Llc Multi-stack fuel cell systems and heat exchanger assemblies

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