Description:
A SYSTEM FOR COOLING AND HUMIDIFICATION OF PROTON EXCHANGE MEMBANE FUEL CELL

FIELD OF INVENTION
[0001] The present disclosure relates to a system for cooling and humidification of reactant air supplied by the turbo air compressor for proton exchange membrane fuel cells (PEMFC) which convert chemical energy directly into electrical energy. The present invention particularly relates to a method to humidify the reactant air external to proton exchange membrane fuel cell (PEMFC) stack.
BACKGROUND
[0002] Ionic conductivity of the membrane is known to be of critical importance to obtain better performance of PEM fuel cell and it is limited to operate temperature below 800C to ensure thermal degradation of the membrane. a temperature of the air supplied by the turbo air compressor under a high power operational condition of the stack is raised to about 100 to 150°C due to a high compression ratio and a large amount of air being supplied. Therefore, it is required for the fuel cell system to cool the high-temperature compressed air to temperature below the permissible limit of fuel cell stack.
[0003] In practice, gas streams are humidified by flowing the reactants through a humidity exchanger which is an additional subsystem to stack. The present invention generally relates to humidification of reactant gases (hydrogen and air) for proton exchange membrane fuel cells (PEMFC) which convert chemical energy directly into electrical energy. Precisely, the present invention relates to humidification of gases external to the fuel cell stack using porous honeycomb which does dual function of cooling and humidification of gas by a process called evaporation.
[0004] A combined cooling of stack and humidifying of reactant gases in the fuel cell system has been attempted using stack coolant water is carried out in two steps liquid feed device as first strand (fluid line) and gas separator as second strand. The first line strand has a supply line for feeding water to a heat exchanger (stack coolant section) of the fuel cell system and a return line (stack coolant exit) for receiving a water-steam mixture from the fuel cell system. The gas separator is in the return line to at least partially separate the steam from the water-steam mixture and provide it at a steam connection. The second line strand is in fluid communication with fluid inlet of gaseous fluid which is feeding to the fuel cell system. The steam connection is coupled to the second line strand downstream of the fluid inlet to admix steam with the fluid (air/ Hydrogen). An additional water feed device is coupled to the supply line to compensate loss of separating mass flow of steam in the first line strand wherein some steam is lost.
[0005] There are some systems/methods known in the prior art showing some efforts on development of the cooling system. These are discussed in the following sections:
[0006] An available state of art relates to a subsystem for humidification of reactant gases comprising a cylindrical candle consisting of multiple number of through holes over the candle length with high internal surface area, enclosed in a hollow cylindrical pipe whose inner diameter and length is equal or higher than the candle diameter and length having provision for reactant gas inlet and exit for the enclosed pipe, wherein the enclosed candle integrated and used as humidification chamber in which atomized spraying nozzle attachment is provided prior to the gas inlet of candle enclosure, the gas carried in the form of mist of water from the nozzle into the humidifying chamber wherein the excess water would be absorbed by the candle.
[0007] Yet another state of art relates to a fuel cell power system having a fuel cell stack receiving humidified oxidant (air) into an oxidant inlet of stack from a compressor progressively pressurizing the oxidant from an inlet pressure to a discharge pressure where a recycled oxidant effluent from the fuel cell is used and the same is progressively pressurized within the compressor at an intermediate pressure not greater than the oxidant effluent pressure and between the compressor inlet pressure and the compressor discharge pressure. In one aspect of the invention, the fluid connection to a compressor is made through the compressor housing into the interior pressurization space of the compressor. In another aspect of the invention, a pressure regulator is provided to manage the flow and pressure of the fuel cell stack effluent oxidant into the fluid connection to the compressor. Ultimately, the fresh oxidant is humidified by recirculation of partial amount of cathode exit unreacted oxidant (air) which is highly saturated with water vapor.
[0008] Another state of art relates to a generic fuel cell system The fuel system comprises an exchange device, which combines the two functions "cooling" and humidification". The exchanging device, which is referred to as a function unit in that document, permits a material flow from the exhaust air of the fuel cell to the intake air to the fuel cell, while a heat exchange occurs from the intake air heated by a compression device to the comparatively cool exhaust air.
[0009] The conventional proton exchange membrane (PEM) fuel cell system presents several disadvantages. It features a complex setup with numerous components, including a fuel cell stack, air and hydrogen supply systems, and a control unit, which can lead to increased maintenance and potential failures. Energy inefficiency arises from the need for a turbo compressor to supply air to the stack. The system also faces challenges in water management, relying on a reservoir and venting for excess water. External humidification adds complexity, and temperature control requires energy-intensive cooling. Integration and monitoring further complicate the system, collectively reducing its overall efficiency and reliability.
[0010] Therefore, it is quite evident that all of the above disclosures has drawbacks including complexity, energy consumption by the turbo compressor, water management issues, reliance on external gas humidification, and energy-intensive temperature control. These challenges collectively hinder system efficiency and reliability. Thus there is a pressing need to achieve the same.
OBJECTS OF THE INVENTION
[0011] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed herein below.
[0012] It is an object of the present subject matter to overcome the aforementioned and other drawbacks existing in the prior art systems and methods.
[0013] It is a principal object of the present subject matter to introduce a system for simultaneously cooling compressed air and humidifying it before supplying it to the proton exchange membrane fuel cell stack.
[0014] It is another significant object of the present subject matter to propose the system to cool the reactant air obtained from the turbo air compressor to stack's air inlet.
[0015] It is another significant object of the present subject matter to propose the system to control the relative humidity or dew point of the reactant air within proton exchange membrane fuel cells (PEMFC).
[0016] It is an object of the present subject matter to propose that water pressure on the shell side is always higher than the pressure of air in the air accumulation section.
[0017] It is yet another object of the present subject matter to propose continuous recirculation of hot water around the circumference of the humidifier candle (shell side) which can be extended to operate on semi-batch operation mode.
[0018] These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art after consideration of the following detailed description taking into consideration with accompanied drawings in which preferred embodiments of the present subject matter are illustrated.
SUMMARY OF THE INVENTION
[0019] This summary is provided to introduce the concept of the system for cooling and humidification of Proton Exchange Membrane Fuel. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0020] The present invention discloses a system for cooling and humidification of Proton Exchange Membrane Fuel. The system for cooling and humidification of Proton Exchange Membrane Fuel Cell comprises of a turbo compressor configured to provide the compressed air to the system, a turbo compressor control mechanisms connected to the turbo compressor configured for varying the speed of the turbo compressor and optimizing the air supply to the system, a temperature and pressure system configured to regulate the temperature of the hot air and to monitor the humidity levels of the input air, a candle humidifier positioned within a hollow shell configured to humidify the input air, a fuel cell stack connected to the candle humidifier configured to generate electricity and water, a water management system configured to the fuel cell stack to collect and regulate the water and excess oxygen and hydrogen, a controller unit connected to the fuel cell stack configured for monitoring and controlling the system, a plurality of pump to regulate the supply of air and coolant in the system, a liquid cooling system connected to the fuel cell stack wherein a mixture of ethylene glycol and water circulates through the stack to dissipate excess heat, with a radiator further cooling the hot coolant and maintaining it at a temperature lower than the stack's set point temperature and a plurality of sensors configured to regulate the temperature ,dew point and pressure of the water and air in the system.
[0021] In one aspect, the liquid cooling system comprises of a radiator configured to cool the hot coolant received from the fuel cell stack reducing its temperature below the set point of the fuel cell stack; a radiator fan configured to regulate the temperature of the coolant by controlling the airflow through the radiator and a reservoir connected to the radiator to store the cooled hot water
[0022] In another aspect, the candle comprises of multiple openings spread across the cross-section of the candle.
[0023] In one aspect, the back pressure on the shell regulated using a back pressure regulator to control and maintain the desired humidity set point for the fuel cell stack.
[0024] In another aspect, the plurality of sensors comprises of temperature sensors, dew point meter and pressure sensors.
[0025] To further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit the scope of the present subject matter.
[0026] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0027] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods or structure in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which
[0028] Fig. 1 illustrates the circuit diagram of a proton exchange membrane fuel cell system with inline candle humidifier in accordance with an embodiment of the present disclosure;
[0029] Fig. 2 illustrates the cross sectional view of porous honeycomb candle assembled in hollow shell in accordance with an embodiment of the present disclosure;
[0030] Fig. 3 illustrates the graphical representation of stack voltage versus current of the system in accordance with an embodiment of the present disclosure.
[0031] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS
[0032] A few aspects of the present disclosure are explained in detail below with reference to the various figures. Example implementations are described to illustrate the disclosed subject matter, not to limit its scope, which is defined by the claims. Those of ordinary skill in the art will recognize a number of equivalent variations of the various features provided in the description that follows.
[0033] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0034] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the “invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0035] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
[0036] Various embodiments are further described herein with reference to the accompanying figures. It should be noted that the description and figures relate to exemplary embodiments and should not be construed as a limitation to the subject matter of the present disclosure. It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the subject matter of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the subject matter of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof. Yet further, for the sake of brevity, operation or working principles pertaining to the technical material that is known in the technical field of the present disclosure have not been described in detail so as not to unnecessarily obscure the present disclosure.
EXEMPLARY EMBODIMENT
[0037] The present invention generally relates to humidification of reactant gases (hydrogen and air) for proton exchange membrane fuel cells (PEMFC) which convert chemical energy directly into electrical energy. In general PEM fuel cells are fed with reactants like hydrogen and oxygen in the form of air. Here, hydrogen is fed at the anode inlet wherein it reacts at electrochemical interface to form electrons and protons (H+), air is fed at the cathode side wherein it reacts with H+ ions received from anode through hydrated membrane to the cathode side forms water as by-product and gives electricity as main product. Precisely, the performance of PEM fuel cell depends on level of hydration of the membrane which maintained through external humidification of the reactant gases. The present invention relates to humidification of air external to the fuel cell stack using porous honeycomb which does dual function of cooling and humidification of reactant air by a process called evaporation and absorption. More particularly, the invention relates to a system to continuously humidify the reactant hot air received from turbo air compressor external to proton exchange membrane fuel cell (PEMFC) stacks.
[0038] Fig. 1 illustrates the circuit diagram of a proton exchange membrane fuel cell system with inline candle humidifier in accordance with an embodiment of the present disclosure. The system for cooling and humidifying Proton Exchange Membrane Fuel Cells (100) comprises of a turbo compressor (24), a turbo compressor control mechanism (16), temperature and pressure device (25), a candle humidifier (17, a fuel cell stack (1), a water management, system (8, 9, 10, 11, 12) a controller unit (5), pumps (43,35), and a liquid cooling system (50). The liquid cooling system (50) incorporates a radiator (30) to cool hot coolant, a radiator fan (31) for temperature control, and a reservoir (11) for storing cooled water.
[0039] The proton exchange membrane (PEM) fuel cell system as shown in Figure 1, comprises of fuel cell stack (1), that receives humidified air (6) and hydrogen (7) supplied to stack inlet as feed gases from subsystems, the excess or unreacted oxygen in the air (8) and hydrogen (9), product water (10) exits from stack outlets through their respective outlets and the same product water is being collected in the reservoir (11) through drain lines and excess water could be bypassed through vent (12). The main controller (5) is used as central unit to ensure the functioning of the key subsystems using proper signal communication for any external load (13), cooling of stack to maintain specified set point (14), supply of air by communicating (15) turbo compressor control unit (16).
[0040] Further the liquid hot water (20) is collected in the reservoir (11) from Fuel cell stack (1) water drain lines (10) which is close to the stack set point temperature (14) would be circulated around the candle circumference over the length of the candle through the shell receiver port (21) and cooled liquid water exits through shell exit port (22). The device would also enable the process of cooling for the hot air (23) received from the turbo compressor (24) prior to that of stack air inlet (6) wherein stack (1) receives relatively low temperature than that of turbo compressor air outlet temperature measured using pressure-temperature sensor (25). In the process of cooling, air also receives moisture from the walls (26) of and air humidity/dew point is being monitored by temperature device (27) and dew point meter (28), the flow rate required dew point meter is adjusted using a control valve (29) to a desired level. In general stack is air/liquid cooled, in case of higher capacity stacks, wherein heat liberation is more it is preferred to be liquid cooled. The stack(1) is cooled with mixture of ethylene glycol and water is circulated through stack at coolant water inlet (4) and hot coolant is received at radiator (30) inlet and it is cooled further to lower temperature than the stack set point temperature (14) using a radiator fan (31) which is controlled using an ON/OFF power supply (32) signal from the main controller (5) of which the signal communication is governed by the pre-set temperature of the coolant (33) and the current value is being measured using (34) which is at least 5degree C lower than the stack operating temperature. Cooled hot water (20) is stored in the reservoir (11), the same water (20) is used to cool the turbo-compressor controller (16) using pump (35).
[0041] Further the controller is powered with the DC supply voltage supply (36) source, speed of the turbo compressor is varied using variable voltage variable frequency (VVVF) signals (37) upon communication from the main controller (15). Also, the compressor is cooled using exit coolant received at turbo compressor inlet port (24) and hot coolant from the compressor out is being circulated through PEM Fuel cell stack (1) via stack coolant port (4).
[0042] Typically, the temperature of hot air (23) of turbo compressor received at humidifier dome (38) would be expanded further prior to interact with the wall surface (26) of the humidifier candle, these walls becomes wet by absorbing water from the pool of water (18) present in the shell and same is used for cooling the hot air as the temperature of hot air is below the stack operating temperature (14) as it is maintained by the cooling circuit radiator (39) using the pre-set temperature (40) with an additional ON/OFF power supply (41) from the main controller using the current temperature measurement device (42) placed prior to the recirculation pump (43) of with check valve(44) to ensure only forward flow of liquid water through inlet port (21) of shell and water from the shell leaves through shell outlet port (22) whose pressure is being monitored using differential pressure transmitter (45) wherein the other of transmitter (45) is connected to dome (38) to measure the pressure difference between the shell side water and hot air, using which the temperature of the hot air and humidity are being controlled with the help of back pressure regulation system (46) which is being communicated with the main controller (5) using the feedback signals (47) of temperature monitoring device (48) and the humidity of the air being monitored (26) with the help of feedback signals received at the controller (5), finally the temperature and humidity of hot is controlled simultaneously with the help of both the signal of (47) and (49) for manipulating the feed inlet temperature of shell feed in water and by varying the back pressure on the shell water pool (18) using the back pressure regulation system (46).
[0043] Fig. 2 illustrates the cross section view of porous honeycomb candle assembled in hollow shell in accordance with an embodiment of the present disclosure. The candle of cylindrical in shape (17) is used as the humidification element which possess highest surface area structure. The candle humidifier (17) is concealed in a hollow shell (18) having higher diameter than the candle diameter (19). liquid hot water (20) collected in the reservoir (11) from Fuel cell stack (1) which is close to the stack operating temperature (14) would be circulated around the candle circumference over the length of the candle through the shell receiver port (21) and cooled liquid water exits through shell exit port (22). The liquid water is being absorbed by the candle from its circumference to interact with maximum surface area for the reactant gas (air) to be humidified. The device would also enable the process of cooling for the hot air (23) received from the turbo compressor (24) prior to that of stack air inlet (6) wherein stack (1) receives low temperature and humidified air which are being monitored by pressure-temperature device (25) and dew point meter (26). The candle (17) comprises of multiple openings spread across the cross-section of the candle (17). The back pressure on the shell (18) is regulated using a back pressure regulator (46) to control and maintain the desired humidity set point for the fuel cell stack (1).
[0044] Further the system consolidates both cooling and humidification functions into a single device, resembling a conventional shell and tube heat exchanger. The core of this modular humidifier is a cylindrical candle with a mesh-like cross-section, enclosed in a larger diameter hollow tube. It allows hot gas to pass through its mesh section, enabling cooling and moisture absorption through simultaneous heat and mass transfer. As compression increases, so does the air temperature, often reaching up to 1500°C. It's crucial to maintain the air temperature consistently below the stack's operational temperature, which is achieved by regulating the temperature of the water circulated around the humidifier candle's circumference.
[0045] The system to control the relative humidity or dew point of the reactant air within proton exchange membrane fuel cells (PEMFC). This control is achieved by adjusting the back pressure on the shell side of the system until the desired humidity set point is attained at the cathode side of the fuel cell stack, ensuring that only humidified air is supplied to the stack.
[0046] The air flow is continuous and water on the shell side is maintained on periodical basis for refilling of water in the humidifier shell volume wherein the differential pressure measured between shell dome wherein hot air is accumulated and shell side water zone becomes zero.
ADVANTAGES OF THE INVENTION
[0047] The proposed system for cooling and humidifying Proton Exchange Membrane Fuel Cells has the following advantages over the contemporary system
[0048] Enhanced Fuel Cell Performance: Optimizes Proton Exchange Membrane Fuel Cell (PEMFC) efficiency by delivering conditioned air with precise temperature and humidity control;
• Prolonged Fuel Cell Lifespan: Maintains ideal operating conditions, reducing wear and tear on fuel cell components and extending their operational life;
• Energy Efficiency: Integrates cooling and humidification functions, reducing energy consumption and enhancing overall system efficiency;
• Effective Heat Dissipation: Efficiently dissipates excess heat with a radiator and fan, preventing overheating and ensuring stable fuel cell operation.
• Robust Water Management: Collects and regulates excess water and gases, ensuring efficient resource utilization and safe operation.

WORKING OF INVENTION
[0049] The present invention is about circulating water around a porous candle outer area which is microporous in nature and cylindrical in shape. It is placed in concealed assembly, the final assembled shell is having provision for circulation of water around the candle, candle is provided with gas inlet and out let. Dry reactant gas enters at inlet side and gains moisture while leaving from the other side of the candle. As the candle is provisioned with continuous water circulation of the other side it is maintained always in wet condition from which the dry gas gains moisture.
TEST RESULT
[0050] Performance test carried out on both the humidifiers, the results are shown in Figure 3. Besides humidification, the main advantage of the current humidifier is that it can cool the hot feed gas to lower temperature than the stack operating temperature, wherein the conventional humidifier (membrane humidifier) fails after temperature of 95 Degree Celsius as the membrane becomes softer because of its physical properties. In practice the temperature of turbo compressor in air would reach above 125 Degree Celsius at rated capacity. In such cases, the conventional humidifiers fail, and the existing one can fulfil both the requirements of humidification and cooling.
[0051] The above description does not provide specific details of the manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.
[0052] Further, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.
[0053] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.
[0054] It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
, Claims:We Claim:
1. A system for cooling and humidification of Proton Exchange Membrane Fuel Cell (100), the system (100) comprising:
a turbo compressor (24) configured to provide the compressed air to the system (100);
a turbo compressor control unit (16) connected to the turbo compressor (24) configured for varying the speed of the turbo compressor and optimizing the air supply to the system (100);
a temperature and pressure system (25) configured to regulate the temperature of the hot air and to monitor the humidity levels of the input air;
a candle humidifier (17) positioned within a hollow shell (18) configured to humidify the input air;
a fuel cell stack (1) connected to the candle humidifier (17) configured to generate electricity and water;
a water management system (8,9,10,11,12) configured to the fuel cell stack (1) to collect and regulate the water and excess oxygen and hydrogen;
a controller unit connected to the fuel cell stack (1) configured for monitoring and controlling the system (100); and
a liquid cooling system (50) connected to the fuel cell stack (1).
2. The system (100) as claimed in claim 1, wherein the liquid cooling system (50) comprises of
a radiator (30) configured to cool the hot coolant received from the fuel cell stack (1) reducing its temperature below the set point of the fuel cell stack (1);
a radiator fan (31) configured to regulate the temperature of the coolant by controlling the airflow through the radiator (30); and
a reservoir (11) connected to the radiator (30) to store the cooled hot water.
3. The system (100) as claimed in claim 1 or 2, wherein a mixture of ethylene glycol and water circulates through the stack (1) to dissipate excess heat, for cooling the hot coolant and maintaining it at a temperature lower than the set point temperature of fuel cell stack (1).
4. The system (100) as claimed in claim 1, wherein a plurality of pumps (35 &43) are connected to regulate the supply of air and coolant in the system (100).
5. The system (100) as claimed in claim 1, wherein a plurality of sensors (25,26,40,41, 42 &48) are configured to regulate the temperature, dew point and pressure of the water and air in the system (100).
6. The system (100) as claimed in claim 1 or 2, wherein the candle (17) comprises of multiple openings spread across the cross-section of the candle (17).
7. The system (100) as claimed in claims 1-3, wherein the back pressure on the shell (18) is regulated by a back pressure regulator (46) to control and maintain the desired humidity set point for the fuel cell stack (1).
8. The system (100) as claimed in claims 1-4, wherein the plurality of sensors (25,26,40,41, 42 &48) comprise of temperature sensors (42 &48), dew point meter (26) and pressure sensors (25).