Fuel cell system with evaporative cooling of cathode exhaust gas turbocharging

Abstract

The present disclosure provides a method for recovering turbine-based energy from an exhaust gas stream in a fuel cell system. The fuel cell system may include an expansion turbine (200) arranged to capture electrical energy from a cathode exhaust gas stream. The cathode exhaust gas stream (151a, 151b, 151c) may flow through an intercooler (250) to be preheated before entering the expansion turbine (200), wherein heat is increased by transferring heat from a compressed air stream. The method may include operating the fuel cell system in a warm-up mode, the mode including reducing fan operation associated with a condenser to reduce liquid recovered from the exhaust gas stream and increasing the exhaust gas stream temperature for turbine-based energy recovery. The warm-up mode may be controlled to limit the operating time based on the coolant fluid level in the fuel cell system.

Description

Technical Field

[0001] The present disclosure relates generally to fuel cell systems and, more particularly, to fuel cell systems having systems for electrical energy recovery from cathode exhaust and electrical output boosting. Background Art

[0002] Fuel cells generate electricity through an electrochemical reaction between a fuel gas and an oxidizing gas. The fuel gas is usually hydrogen, and the oxidizing gas is air. Metals such as palladium and platinum are used as catalysts to cause the electrochemical reaction between the fuel gas and the oxidizing gas.

[0003] Conventional electrochemical fuel cells convert fuel and oxidant into electrical energy and reaction products. Common types of electrochemical fuel cells include membrane electrode assemblies (MEA), which include polymer ion (proton) transfer membranes and gas diffusion structures between anodes and cathodes. Fuel (e.g., hydrogen) and oxidant (e.g., oxygen in the air) pass through the respective sides of the MEA to produce electrical energy and water as reaction products. A stack including a plurality of such fuel cells can be formed, which are arranged with separate anode and cathode fluid flow paths. Such a stack is typically in the form of a block, which includes many individual fuel cell plates held together by end plates at either end of the stack.

[0004] It is important that the polymeric ion transport membrane remain hydrated for efficient operation. It is also important to control the temperature of the stack. Thus, a coolant may be supplied to the stack for cooling and / or hydration. Thus, for example, a fuel cell system may include a water / coolant storage tank for storing water for hydration and / or cooling of the fuel cell stack.

[0005] In an evaporatively cooled fuel cell system, a net water balance must be maintained to keep available coolant for cooling the stack and hydration of the stack. Components that recover additional amounts of coolant from the fuel cell system for reuse may be larger or heavier as their capacity increases. It is desirable that the total weight and volume of components associated with the electrical energy output from the entire fuel cell system be minimized.

[0006] Therefore, there is a need for a fuel cell system that can provide adequate hydration and cooling while having a desired power density and capacity for electrical energy output. The present disclosure addresses these and other important needs. Summary of the invention

[0007] According to some aspects of the present disclosure, a fuel cell system and method of use are disclosed, which provide a method for recovering electrical energy from cathode exhaust gas of a transpiration-cooled fuel cell system. In some implementations, the method can provide additional energy recovery by setting the air fan delivering cooling air to the primary air-cooled condenser to zero or reducing the operating set point value. In some implementations, this can allow a higher inlet temperature to the turbine for electrical energy recovery.

[0008] In some aspects, the present disclosure provides a method of recovering excess electrical energy via a dedicated generator using a higher inlet temperature to the turbine. In other implementations, the net motor input power can be reduced if the turbine is connected to a common motor with an inlet air compressor. In further implementations, the turbine can be connected to a compressor in an exhaust module as described herein.

[0009] In some aspects, the present disclosure provides a method for recovering additional electrical energy from a cathode exhaust gas of a transpiration-cooled fuel cell system. In certain implementations, the method may include operating the fuel cell system in an energy recovery mode during an operating state where reduced condensate recovery can be tolerated. In some implementations, such a tolerable state includes an operating state where the primary coolant level is already sufficiently high.

[0010] In some aspects, the present disclosure provides a method of recovering additional electrical energy from cathode exhaust gas of an evaporatively cooled fuel cell system. In certain implementations, the method may include operating the fuel cell system in an energy recovery mode during an operating state with a partial load or a low load, wherein a minimum set point of a fan delivering cooling air to a main air-cooled condenser provides a load greater than that required for water balance. In certain implementations, the fan may be square wave to achieve net water balance and additional turbine recovery.

[0011] The present disclosure provides a fuel cell system including a fuel cell assembly, a coolant storage module, a thermal module and an expansion turbine. In some embodiments, the fuel cell assembly has an anode inlet, a cathode inlet, an anode exhaust gas and a cathode exhaust gas, the coolant storage module is configured to provide a coolant to the fuel cell assembly, the thermal module is fluidly connected to the fuel cell assembly and the coolant storage module, the thermal module includes a condenser and a separator, the expansion turbine receives an expansion exhaust gas flow, and the expansion exhaust gas flow includes a cathode exhaust gas leaving the fuel cell assembly, a cathode exhaust gas leaving the thermal module separator, an anode purge gas flow and a fluid flow leaving the thermal module condenser. A combination of at least a portion of one or more. In a further embodiment, the fuel cell system may include an intercooler disposed in the flow path of the expansion exhaust gas flow before the expansion turbine, wherein the intercooler is configured to increase the temperature of the expansion exhaust gas flow. In some embodiments, the intercooler may be fluidically connected to a compressed flow stream and configured to transfer heat from the compressed flow stream to the expansion exhaust gas flow. In some embodiments, the compressed flow stream may include a fluid flow connected to the cathode inlet of the fuel cell assembly. In a further embodiment, the expansion turbine may include or be coupled to a compressor. In yet further implementations, the fuel cell system may further include a dilution tank configured to dilute the hydrogen concentration in the exhaust gas flow to a hydrogen concentration below a predetermined concentration.

[0012] The present disclosure provides a fuel cell system including a fuel cell assembly, a coolant storage module, a thermal module, an exhaust module, and an expansion turbine. In some embodiments, the fuel cell assembly has an anode inlet, a cathode inlet, an anode exhaust gas, and a cathode exhaust gas, the coolant storage module is configured to provide a coolant to the fuel cell assembly, the thermal module is fluidly connected to the fuel cell assembly and the coolant storage module, the thermal module includes a condenser and a separator, the exhaust module is configured to remove hydrogen from the fluid flow entering the exhaust module, the expansion turbine receives an expanded exhaust gas stream, and the expanded exhaust gas stream includes a cathode exhaust gas leaving the fuel cell assembly, a cathode exhaust gas leaving the thermal module separator, and a fluid flow leaving the thermal module condenser. A combination of at least a portion of one or more of the fluid flow. In a further embodiment, the fuel cell system may include an intercooler disposed in the flow path of the expanded exhaust gas stream before the expansion turbine, wherein the intercooler is configured to increase the temperature of the expanded exhaust gas stream. In some embodiments, the intercooler may be fluidically connected to the compressed flow stream and configured to transfer heat from the compressed flow stream to the expanded exhaust gas stream. In some embodiments, the compressed flow stream may include a fluid stream fluidly connected to the cathode inlet of the fuel cell assembly. In further implementations, the expansion turbine may include or be coupled to the compressor.

[0013] The present disclosure provides a method for operating a fuel cell system as described herein. The method may include providing coolant to a fuel cell assembly from a coolant storage module, providing an anode gas flow to the anode inlet of the fuel cell assembly, providing a cathode gas flow to the cathode inlet of the fuel cell assembly, operating a thermal module condenser and a thermal module separator to provide coolant to the coolant storage module, directing a fluid flow to an exhaust module and operating the exhaust module to remove hydrogen from the fluid flow, and directing an expanded exhaust gas flow to an expansion turbine and operating the expansion turbine to generate an electrical output. In some implementations, the method further includes operating an intercooler to increase the temperature of the expanded exhaust gas flow before directing the expanded exhaust gas flow to the expansion turbine. In certain implementations, the method further includes connecting an intercooler fluid to a compressed flow stream and transferring heat from the compressed flow stream to the expanded exhaust gas flow. In further implementations, the method further includes directing the compressed flow stream to the cathode inlet of the fuel cell assembly after heat transfer. In some implementations, the method further includes connecting a compressor to an expansion turbine. In further implementations, the method further includes generating a compressed flow stream using a compressor connected to an expansion turbine and connecting the compressed flow stream fluid to an intercooler. In some implementations, the method further includes operating the fuel cell system in a warm-up mode, wherein the warm-up mode includes controlling one or more fans to reduce the set point of the one or more fans below a predetermined threshold level to increase the exit temperature of the fluid flow from the condenser. In some implementations, the method further includes operating the fuel cell system in the warm-up mode for a predetermined time period less than or equal to a first predetermined operating time limit when the amount of coolant in the coolant storage module is less than a first threshold amount. In some implementations, the method further includes limiting the operation of the fuel cell system in the warm-up mode when the amount of coolant in the coolant storage module is less than a second threshold amount. In some implementations, the method further includes operating the fuel cell system in the warm-up mode for a second predetermined operating time limit when the amount of coolant in the coolant storage module is greater than the second threshold amount. In some implementations, the second predetermined operating time limit may be longer than the first predetermined operating time limit. In some implementations, the method further includes continuously operating the fuel cell system in the warm-up mode when the amount of coolant in the coolant storage module is greater than the second threshold amount until the amount of coolant in the coolant storage module drops below a third threshold amount.

[0014] The present disclosure provides a method for operating a fuel cell system as described herein. The method may include providing coolant from a coolant storage module to a fuel cell assembly, providing an anode gas flow to an anode inlet of a fuel cell assembly, providing a cathode gas flow to a cathode inlet of a fuel cell assembly, operating a thermal module condenser and a thermal module separator to provide coolant to a coolant storage module, and directing an expanded exhaust gas flow to an expansion turbine and operating the expansion turbine to generate an electrical output. In some implementations, the method further includes operating an intercooler to increase the temperature of the expanded exhaust gas flow before directing the expanded exhaust gas flow to the expansion turbine. In further implementations, the expanded exhaust gas flow includes a combination of at least a portion of one or more of the cathode exhaust gas leaving the fuel cell assembly, the cathode exhaust gas flow leaving the thermal module separator, the anode purge gas flow, and the fluid flow leaving the thermal module condenser. In certain implementations, the method further includes connecting an intercooler fluid to a compressed flow stream and transferring heat from the compressed flow stream to the expanded exhaust gas flow. In further implementations, the method further includes directing the compressed flow stream to the cathode inlet of the fuel cell assembly after the heat transfer. In some implementations, the method further includes coupling a compressor to an expansion turbine. In certain embodiments, the expanded exhaust gas stream includes at least a portion of the anode purge gas stream, and the method further includes burning at least a portion of the anode purge gas stream to increase the temperature of the expanded exhaust gas stream before it is delivered to the expansion turbine. In further embodiments, the method further includes generating a compressed flow stream using a compressor coupled to the expansion turbine and fluidly connecting the compressed flow stream to an intercooler. In some embodiments, the method further includes operating the fuel cell system in a warm-up mode, wherein the warm-up mode includes controlling one or more fans to reduce the set point of the one or more fans below a predetermined threshold level to increase the exit temperature of the fluid stream from the condenser. In some embodiments, the method further includes operating the fuel cell system in the warm-up mode for a predetermined time period less than or equal to a first predetermined operating time limit when the amount of coolant in the coolant storage module is less than a first threshold amount. In some embodiments, the method further includes limiting the operation of the fuel cell system in the warm-up mode when the amount of coolant in the coolant storage module is less than a second threshold amount. In some embodiments, the method further includes operating the fuel cell system in the warm-up mode for a second predetermined operating time limit when the amount of coolant in the coolant storage module is greater than a second threshold amount. In some implementations, the second predetermined operating time limit can be longer than the first predetermined operating time limit. In some implementations, the method further includes when the amount of coolant in the coolant storage module is greater than the second threshold amount, continuously operating the fuel cell system in the warm-up mode until the amount of coolant in the coolant storage module drops below a third threshold amount.

[0015] The general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure as defined in the appended claims.Other aspects of the present disclosure will be apparent to those skilled in the art in view of the detailed description of the present disclosure provided herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The Summary of the Invention and the following Detailed Description will be further understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the present disclosure, exemplary implementations of the present disclosure are shown in the accompanying drawings; however, the present disclosure is not limited to the specific methods, compositions, and apparatus disclosed. In addition, the drawings are not necessarily drawn to scale. All legends and annotations in the accompanying drawings are incorporated herein by this reference as if fully set forth herein. In the drawings:

[0017] Figure 1 is a schematic diagram of system and method of operation aspects of a fuel cell power system of the present disclosure;

[0018] Figure 1B is a schematic diagram of aspects of a fuel cell stack useful in some implementations of the methods and systems of the present disclosure;

[0019] Figure 2 is a schematic diagram of a coolant storage module according to the present invention.

[0020] Figure 3 is a schematic diagram of aspects of a thermal module of the present disclosure;

[0021] Figure 4 is a schematic diagram of aspects of a fuel cell system of the present disclosure; and

[0022] Figure 5 is a schematic diagram of aspects of components of a fuel cell system of the present disclosure, including an expansion turbine. DETAILED DESCRIPTION

[0023] By referring to the following detailed description in conjunction with the drawings and examples that constitute a part of the present disclosure, the present disclosure can be more easily understood.It should be understood that the present disclosure is not limited to the specific equipment, methods, applications, conditions or parameters described and / or shown herein, and the terms used herein are only used to describe specific examples by way of example and are not intended to limit the disclosure claimed for protection.In addition, as used in the specification including the attached claims, the singular forms "one", "a kind of" and "the" include plural forms, and references to specific numerical values ​​include at least the specific value, unless the context clearly specifies otherwise.As used herein, the term "multiple" refers to more than one.When expressing the range of values, another example includes from one specific value and / or to another specific value.Similarly, when a value is expressed as an approximation, by using the antecedent "about", it will be understood that the specific value forms another example.All ranges are inclusive and combinable.

[0024] It should be understood that, for the sake of clarity, certain features of the present disclosure described herein in the context of separate examples may also be provided in combination in a single exemplary implementation. On the contrary, for the sake of brevity, the various features of the present disclosure described in the context of a single exemplary implementation may also be provided individually or in any sub-combination. Further, references to values ​​stated in a range include every value within that range.

[0025] System Overview

[0026] Figure 1 Schematically illustrates some aspects of an exemplary implementation of a fuel cell system 10 including a fuel cell assembly 20 and a coolant storage module 30. The present disclosure includes operating a fuel cell power system.

[0027] The fuel cell assembly 20 includes one or more fuel cell stacks 21, which include a plurality of proton exchange membrane fuel cells stacked together and a balance of plant (balance of plant) BOP (not shown), which includes pumps, valves, fans, controllers and circuits, etc., which are well known in the art. The fuel cell assembly 20 shown is an evaporatively cooled fuel cell assembly. In this example, the coolant includes water, but it should be understood that other coolants can be used, such as ethylene glycol, water or other or aqueous solutions. In this example, the coolant or water storage module 30 stores pure water for hydration and / or evaporative cooling of the fuel cell assembly 20. The coolant storage module 30 includes a coolant storage tank 32 to accommodate a coolant supply 40.

[0028] The fuel cell system 10 includes a hydrogen source. The hydrogen source provides hydrogen fuel gas to multiple parts of the fuel cell system 10 as needed. For example, the hydrogen source provides hydrogen fuel gas to the fuel cell assembly 20. The anode side in the fuel cell 20 receives hydrogen. The hydrogen source is fluidly connected to the anode inlet 22 of the fuel cell assembly 20. In some aspects of the present disclosure, the hydrogen source is provided to the coolant tank heater / catalytic heater, the anode tail gas burner and / or the anode exhaust gas absorber. The fuel cell system 10 may include a hydrogen storage tank (not shown) for storing a hydrogen supply.

[0029] The fuel cell system 10 includes an air source 12 for supplying an oxygen supply to a fuel cell assembly 20. The cathode side of the fuel cell assembly 20 receives the air source 12. The air source 12 is fluidly connected to the fuel cell assembly 20 at a cathode inlet 24. One or more compressors may be located upstream of the cathode inlet 25 to increase the pressure of the air before being introduced into the cathode side of the fuel cell assembly 20.

[0030] The fuel cell assembly 20 and one or more stacks therein are configured to receive a fuel and an oxidant. Figure 1B A schematic diagram of an array or grouping of fuel cell stacks 21 and 21 ′ within a single fuel cell assembly 20 is shown.

[0031] A fuel fluid flow, such as hydrogen, reaches the anode through the anode inlet 24, while a fluid flow of an oxidant, such as air, reaches the cathode through the cathode inlet 25. An anode exhaust 26 is provided to allow the flow of fuel. A cathode exhaust 27 is provided to allow the flow of oxidant. It should be understood that the exhaust gas flow also carries some reaction byproducts and any coolant / hydration liquid that may have passed through the assembly 20. The cathode exhaust 27 may include a coolant separator 28 to separate the generated water and coolant (water) 40' from the cathode exhaust gas flow. The separated water is stored in a coolant storage module 30. It should be understood that although this example shows the recovery of water (coolant) that has passed through the stack, the present disclosure is applicable to systems that do not recover coolant or recover coolant in a different manner. Air from the cathode exhaust 27 may be provided to a compressor 82 for use in an anode tail gas burner (AOBH). In some implementations, an anode gas purge flow may be provided, which may be directed to the anode tail gas burner.

[0032] The coolant storage module 30 is fluidly connected to the fuel cell assembly by a conduit, but it should be understood that the module 30 can be integrated with the fuel cells in the stack. The coolant storage module 30 is connected to the cathode inlet 25 to allow coolant to be introduced into the cathode stream for evaporative cooling of the fuel cell assembly 20. The coolant can be introduced into the stack by a separate conduit.

[0033] The coolant storage module 30 may include a plurality of coolant storage tanks. The compressor that drives the oxidant through the fuel cell assembly may heat up relatively quickly after the fuel cell assembly is started, and therefore a heat exchanger and working fluid and / or heat pipe (fluid connection) are used to move heat from the compressor within the oxidant (air source) 12 to the coolant storage module, and in some cases, the waste heat may be used at least in part to drive the anode tail gas burner. The coolant injection / flow controller 100 may form part of a fuel cell system controller 105 for controlling further operation of the fuel cell system.

[0034] In some implementations, the fuel cell system 10 may include at least one catalytic heater 52 that burns combustion fuel by catalysis of a combustion catalyst. The catalytic heater may be used to meet the heating needs of the system 10 in different ways. In other implementations, the fuel cell system may include an electric heater.

[0035] The catalytic heater 52 includes one or more catalytic heating elements 55. The catalytic heater 52 may provide a housing 57 to accommodate the catalytic heating elements 55. The catalytic heating elements 55 include a catalytic material for combustion. The catalytic material may be supported on a substrate. The present disclosure contemplates a variety of different structures for the catalytic heater 52 and the catalytic heating elements 55.

[0036] Preferably, the catalytic heater 52 is independent of the fuel cell assembly 20. An independent catalytic heater 52 is able to continue to operate when the fuel cell assembly 20 is shut down. This feature is particularly advantageous because the coolant temperature is maintained and is not a function of the fuel cell operation. If the catalytic heater 52 is not independent of the fuel cell assembly, fuel cell startup may be delayed under sub-zero operating ambient conditions.

[0037] In certain implementations, the fuel cell system 10 may include a thermal module 70 configured to recover water from the cathode exhaust gas. Figure 1 and Figure 3 As shown, the thermal module 70 is fluidly connected to the fuel cell assembly 20 and the coolant module 30. The thermal module 70 includes a condenser 71 and a separator 72. The condenser 71 and the separator 72 can be integrated into a single operation. The condenser 71 can be air-cooled or liquid-cooled. Alternatively, the condenser 71 can use a combination of air cooling and liquid cooling. For example, the first stage of the condenser 71 can use air cooling, while the second stage can use liquid cooling.

[0038] The cathode exhaust gas 27 can be directed from the fuel cell assembly 20 to a condenser 71, which is used to liquefy and recover any water vapor in the cathode exhaust gas. One or more fans 73 can be used to cool the condenser 71 during its operation. The cathode exhaust gas including the condensed water vapor then flows from the condenser 71 to the separator 72. The separator 72 is used to separate water from any remaining gas in the cathode exhaust gas. The separator 72 and the condenser can each provide a sub-water outlet 74'. The main water outlet 74 is fluidly connected to the coolant storage module 30. When the condensed cathode exhaust gas flows through the separator 72, the water is removed and directed to the coolant storage tank 32. The gas from the cathode exhaust gas stream leaves the separator at the gas outlet 76 and is discharged into the atmosphere.

[0039] In some embodiments, the fuel cell system 10 may include an exhaust module 80 configured to purify the anode exhaust and remove hydrogen therefrom. Specifically in automotive applications, emission standards may strictly limit the ppm of hydrogen in the exhaust gas stream. The exhaust module 80 is fluidly connected to the air source 12, the fuel cell assembly 20, and the coolant module 30. The exhaust module 80 includes a compressor 82 and a tail gas burner 84. The tail gas burner can be a catalytic heater 52 as described above. The exhaust module receives hydrogen in the anode exhaust gas stream and burns the hydrogen to generate heat, which can be one or more of the exhaust gas discharged from the system for additional applications, such as electricity generated by a turbine, and recovered and used for coolant thawing.

[0040] The exhaust module 80 can be fluidly connected to the system and can receive air directly from the air source 12. The oxidant stream 25' and / or the exhaust gas 27' pass through the fluid connection via a fan or compressor 82, whereby it is pressurized. The feed from the compressor is provided to the tail gas burner 84. The tail gas burner not only reduces the hydrogen ppm in the exhaust gas stream, but also when placed in thermal communication with the hydrogen module 85, the heat loss from the exhaust gas combustion is captured and provided to regenerate the oxygen absorber medium 86 filled in the hydrogen module 85. The oxygen absorber or oxygen scavenger must be regenerated regularly to remove the oxygen captured thereby. The module is configured as an anode tail gas burner heater (AOBH), which provides heat to regenerate the medium. Regeneration is achieved by adding hydrogen to the fluid stream entering the exhaust module 80. By fully heating the oxygen absorber medium 86, oxygen and hydrogen form water and regenerate the medium. Water is taken out of the oxygen absorber medium 86 as water vapor in the air stream.

[0041] The oxygen absorber medium 86 is periodically regenerated during fuel cell operation. At startup, the anode will contain oxygen that has migrated into the anode, and operating (starting) the fuel cell in the presence of such oxygen will cause damage by corroding the cathode support by raising the cathode potential and thereby oxidizing the cathode support, thereby degrading the support and reducing the membrane surface area.

[0042] Typically, the tail gas burner may be surrounded by an absorbent material and the hydrogen module has the functionality to remove oxygen from a portion of the anode exhaust gas stream fluidly connected thereto and provide fuel with reduced oxygen for starting the fuel cell stack.

[0043] In an optional implementation, the exhaust module 80 is not present in the system. In certain implementations, one or more exhaust streams may be diluted with a dilution tank to reduce the concentration of hydrogen. In some implementations, the exhaust stream may be diluted to reduce the hydrogen concentration to below a threshold level that is safe for exhaust gas discharged into the atmosphere. The threshold level may be determined by an emission standard that limits the ppm of hydrogen in the exhaust stream. In further implementations, dilution may be provided before the exhaust stream is delivered to the expansion turbine, as described elsewhere herein.

[0044] Figure 2 The coolant storage tank 32 shown in holds a coolant supply 40. The coolant storage tank can include an outer layer 33. The outer layer can substantially surround the coolant storage tank. The outer layer can be formed and adhered to the coolant storage tank 32. The outer layer can be insulating to protect the temperature of the coolant storage tank and the coolant therein. The insulation can minimize any heat loss from the coolant supply. The outer layer can be rigid or flexible. The outer layer can be composed of a variety of suitable materials as discussed herein.

[0045] The outer layer may define an interstitial space "IS" between an inner boundary of the outer layer and an outer boundary of the coolant storage tank. At least one of an insulator and a heat transfer material may be present in the interstitial space, and the heat transfer material may include metal foam, honeycomb, wax. Within the coolant storage tank, one or more catalytic heaters 52, fans 36 for exhausting steam, and / or temperature sensors 37 for measuring temperature. An additional catalytic heater 55 may be located outside the coolant storage tank but in thermal communication therewith.

[0046] The fuel cell system 10 includes at least one coolant storage tank 32 for storing a coolant supply 40. In some aspects of the present disclosure, the coolant is water. The coolant storage tank can be constructed of a variety of suitable materials, including but not limited to light metals (such as aluminum) or high temperature plastic materials. Figure 2 Further aspects of the coolant storage module are described. The coolant storage tank can be insulated 33. For example, vacuum insulation panels can be used to insulate the tank. The storage tank can also include suitable ventilation as required.

[0047] The coolant storage tank is fluidly connected to the fuel cell assembly. The coolant storage tank has an inlet 34 and an outlet 35. The inlet of the storage tank receives coolant from the fuel cell assembly 20, which produces water as a byproduct of the electrochemical reaction. The outlet of the storage tank discharges the coolant to the fuel cell assembly to cool the fuel cell stack 21. The coolant storage tank is thermally connected to the catalytic heater so that at least a portion of the heat generated by the catalytic heater is provided to the coolant in the coolant storage tank.

[0048] In some exemplary implementations, a thermal module may be used in the systems and methods herein to recover water from a gas / liquid stream. Figure 3 The exemplary thermal module shown in FIG. 1 is configured to recover water from the cathode exhaust gas. It can be fluidly connected to the fuel cell assembly 20 and the coolant module 30 .

[0049] Example: System and method for improved electrical energy recovery

[0050] In some aspects, the present disclosure provides a method for improved power recovery during operation of a fuel cell system. The air flow through the cathode air-cooled condensing radiator can be used to control the condensed water recovery rate to achieve a net water balance. The hot side cathode exhaust gas of the condensing radiator can pass through a water separator. The cathode exhaust gas can then be delivered directly to the turbine, or alternatively delivered via an intercooler, where when operating under pressurized conditions, the cathode exhaust gas recovers excess heat from the compressor tail gas. The cathode exhaust gas stream can then be expanded through a turbine stage to achieve power recovery.

[0051] In some implementations, the set point on the radiator fan can be reduced to reduce the heat exhausted via the air flow, resulting in a higher exit temperature from the air-cooled condensing radiator. In certain implementations, the higher temperature exhaust gas can be directed directly to the turbine after the water separation stage to increase the turbine inlet temperature. Optionally, the hot side exit gas from the radiator can be sent to an air intercooler, in which the heat is increased by heating due to the heat transferred from the hot side, and thus the temperature is increased, where the hot compressor outlet air is cooled to a temperature compatible with the fuel cell stack. The use of an intercooler can avoid the situation of 100% relative humidity, which can cause condensation on the turbine blades when the flow expands, resulting in tip erosion of the blades. Under operation using an intercooler, when the gas is sent to the turbine stage, its relative humidity is reduced, thereby reducing the possibility of condensation during expansion and tip erosion. The intercooler also provides an increased turbine inlet temperature, which can result in more electrical energy being recovered from the turbine stage.

[0052] In some aspects, these methods can be used when a reduced condensate recovery rate can be sustained for short periods of operation. This avoids affecting the net water balance during longer periods of operation. These methods are beneficial because they can provide a short-term boost in peak net power from the fuel cell system. Further benefits are provided at part load and low load, where marginal gains in electrical efficiency can be obtained when the minimum set point on the fan is high to result in excess condensate recovery.

[0053] Figure 4 and 5 Some further aspects of certain implementations of the fuel cell systems and methods of the present disclosure are depicted. Figure 4 Depicted Figure 1 Some aspects of turbine-based exhaust energy recovery systems of variations of the system shown. In some implementations, the cathode exhaust gas 27 (connected by stream 151a), the cathode exhaust gas stream exiting the separator at the gas outlet 76 (connected by stream 151c), the anode gas purge stream ( Figure 4 and Figure 5 At least a portion of the exhaust gas stream in one or more of the streams (not shown), and the streams exiting the condenser 71 (connected by stream 151b) can be directed through the expanded exhaust gas stream 150 to the expansion turbine 200. In some implementations, such as Figure 4 One or more of the streams 151a, 151b, and 151c shown may be combined into the expanded exhaust gas stream 150. All three streams 151a, 151b, and 151c are Figure 4 , but in some implementations, there may be only one or two streams. In some implementations, only stream 151a is present in the fuel cell system. In other embodiments, only stream 151b is present in the fuel cell system. In further embodiments, only stream 151c is present in the fuel cell system. In other implementations, two of streams 151a, 151b, and 151c are present in the fuel cell system. In further implementations, all three streams 151a, 151b, and 151c are present in the fuel cell system. In still further implementations, the anode gas purge stream may be combined with one or more of streams 151a, 151b, and 151c in the fuel cell system.

[0054] In some embodiments, the expansion turbine 200 may be coupled to or include the compressor 82 of the exhaust module 80 to provide some or all of the energy required to operate the compressor 82 during operation of the exhaust module 80. In other embodiments, the fuel cell system may omit the exhaust module 80, and in some cases may include a dilution tank to reduce the hydrogen concentration in the expanded exhaust gas stream 150 before the expanded exhaust gas stream 150 flows to the expansion turbine 200. In certain embodiments, the expansion turbine 200 may be coupled to or include a compressor 300, which provides compression for one or more fluid streams entering the fuel cell assembly 20. The expansion turbine 200 may also include a generator component known in the art, which can be used to recover electrical energy from the expanded exhaust gas stream 150. The generator output can be used to power auxiliary equipment components or contribute to the overall electrical energy output of the fuel cell system. In a further embodiment, an intercooler 250 may be disposed in the flow path of the expanded exhaust gas stream 150 before the expansion turbine 200. In some implementations, one or more fluid streams 155 from the compressor 300 may be cooled by the intercooler 250, which may be configured to heat the expanded exhaust gas stream 150 via heat transfer from the compressed fluid stream 155 to the expanded exhaust gas stream 150 through the intercooler component, such as Figure 5 The cooled fluid stream 156 may then be sent to the fuel cell assembly 20 at an appropriate, non-damaging temperature for fuel cell stack operation, while the further heated expanded exhaust gas stream 152 is sent to the expansion turbine 200 . Figure 5 An incoming fluid stream 154 is shown passing to the compressor 300. The fluid stream 154 may be an oxidant stream, such as air, that will flow to the cathode inlet 25.

[0055] In certain implementations, during the operating mode, the set point on one or more fans 73 in the thermal module 70 can be reduced below a predetermined threshold level to reduce the heat removed via the air flow, resulting in a higher exit temperature from the condenser 71, which can be used to provide a higher temperature expansion exhaust gas flow 150. This operating mode, also referred to herein as the warm-up mode, can result in a reduced condensation recovery rate and less coolant flowing into the coolant storage module 30. The warm-up mode can be operated for a short period of time to provide a short-term energy output provision. The limited operating time can avoid the net water balance from being compromised during a longer operation period. In certain implementations, when the amount of coolant in the coolant storage module 30 is less than a first threshold amount, the warm-up mode can be operated for a predetermined period of time less than or equal to a first predetermined operating time limit. The amount of coolant in the coolant storage module 30 can be measured with a level sensor or can be estimated from data about the operation of the fuel cell system. In some implementations, when the amount of coolant in the coolant storage module 30 is less than a second threshold amount, the occurrence of the warm-up mode can be limited. In some implementations, when the amount of coolant in the coolant storage module 30 is greater than the second threshold amount, the warm-up mode may be operated for a second predetermined operating time limit. In some implementations, the second predetermined operating time limit may be longer than the first predetermined operating time limit. In some implementations, when the amount of coolant in the coolant storage module 30 is greater than the second threshold amount, the warm-up mode may be operated continuously until the amount of coolant in the coolant storage module drops below a third threshold amount. The third threshold amount may be higher, equal to, or lower than the second threshold amount.

[0056] In some aspects, the present disclosure relates to a method of operating a fuel cell system. The method may include operating the fuel cell system in a warm-up mode in some cases. The warm-up mode can be used to respond to a demand for increased power output from a downstream user of the fuel cell system, an automated control system that determines the need to increase power, or a combination of a user and an automated control system. The warm-up mode may include operating a fan associated with a condenser at a lower set point, which reduces the amount of liquid condensed in the cathode exhaust gas stream connected to the separator fluid.

[0057] Those of ordinary skill in the art will appreciate that a variety of materials can be used to make the components in the devices and systems disclosed herein. Any suitable structure and / or material can be used for the various features described herein, and the technician will be able to select suitable structures and materials based on a variety of considerations, including the intended use of the systems disclosed herein, the fields in which they are expected to be used, the equipment and / or accessories in which they are expected to be used, and other considerations. Traditional polymers, metal-polymer composites, ceramics, and metallic materials are suitable for a variety of components. Materials that are determined to be suitable for use in the features and elements described herein that are found and / or developed hereinafter will also be considered acceptable.

[0058] When ranges are used herein for physical properties, such as molecular weight, or chemical properties, such as chemical formula, all combinations and subcombinations of ranges specifically recited therein are intended to be included.

[0059] The disclosures of each patent, patent application, and publication cited or described in this document are incorporated herein by reference in their entirety.

[0060] Those skilled in the art will appreciate that various changes and modifications may be made to the examples of the present disclosure, and such changes and modifications may be made without departing from the spirit of the present disclosure. Therefore, it is intended that the appended claims cover all such equivalent changes that fall within the true spirit and scope of the present disclosure.

Claims

1. A fuel cell system, comprising: A fuel cell assembly having an anode inlet, a cathode inlet, an anode exhaust gas, and a cathode exhaust gas; a coolant storage module configured to provide coolant to the fuel cell assembly; a thermal module in fluid connection with the fuel cell assembly and the coolant storage module, the thermal module comprising a condenser and a separator; an expansion turbine receiving the expanded exhaust gas flow; one or more fans coupled to the thermal module condenser; a controller configured to operate the fuel cell system in a warm-up mode, wherein in the warm-up mode, the controller is configured to control the one or more fans and reduce a set point on the one or more fans below a predetermined threshold level to increase an exit temperature of a fluid stream from the condenser; wherein the expanded exhaust gas stream comprises a combination of at least the cathode exhaust gas exiting the fuel cell assembly, the anode exhaust gas exiting the fuel cell assembly, an anode gas purge stream, the anode exhaust gas stream exiting the thermal module separator, and a fluid stream exiting the thermal module condenser; and The controller is further configured to operate the fuel cell system in the warming mode for a predetermined time period less than or equal to a first predetermined operating time limit when the amount of coolant in the coolant storage module is less than a first threshold amount, and to continuously operate the fuel cell system in the warming mode when the amount of coolant in the coolant storage module is greater than a second threshold amount until the amount of coolant in the coolant storage module drops below a third threshold amount.

2. A method of operating a fuel cell system, the fuel cell system comprising: a fuel cell assembly having an anode inlet, a cathode inlet, an anode exhaust gas, and a cathode exhaust gas; a coolant storage module configured to provide coolant to the fuel cell assembly; a thermal module in fluid connection with the fuel cell assembly and the coolant storage module, the thermal module comprising a condenser and a separator; an expansion turbine receiving the expanded exhaust gas flow; wherein the expanded exhaust gas stream comprises a combination of the cathode exhaust gas exiting the fuel cell assembly, the anode exhaust gas exiting the fuel cell assembly, an anode gas purge stream, the cathode exhaust gas stream exiting the thermal module separator, and a fluid stream exiting the thermal module condenser; The method comprises: providing coolant from the coolant storage module to the fuel cell assembly; providing an anode gas flow to an anode inlet of the fuel cell assembly; providing a cathode gas flow to a cathode inlet of the fuel cell assembly; operating the thermal module condenser and the thermal module separator to provide coolant to the coolant storage module; and, directing the expanded exhaust gas stream to the expansion turbine and operating the expansion turbine to generate an electrical output, wherein the fuel cell system further comprises one or more fans coupled to the thermal module condenser; and operating the fuel cell system in a warm-up mode for a predetermined time period less than or equal to a first predetermined operating time limit when the amount of coolant in the coolant storage module is below a first threshold amount; and Wherein the warm-up mode includes controlling the one or more fans to reduce a set point of the one or more fans below a predetermined threshold level to increase an exit temperature of the fluid flow from the condenser.

3. The method according to claim 2, wherein the fuel cell system further comprises: an exhaust module configured to reduce a hydrogen concentration in a fluid stream; and The method further comprises: A fluid flow is directed to the exhaust module and the exhaust module is operated to reduce a hydrogen concentration in the fluid flow.

4. The method according to claim 3, wherein the fuel cell system further comprises: an intercooler disposed in a flow path of the expanded exhaust gas flow before the expansion turbine, the intercooler being configured to increase a temperature of the expanded exhaust gas flow; and Wherein the method further comprises: The intercooler is operated to increase the temperature of the expanded exhaust gas stream prior to directing the expanded exhaust gas stream to the expansion turbine.

5. The method of claim 4, wherein the method further comprises fluidly connecting the intercooler to the compressed flow stream and transferring heat from the compressed flow stream to the expanded exhaust gas stream.

6. The method of claim 5, wherein the method further comprises directing the compressed flow stream to a cathode inlet of the fuel cell assembly after heat transfer.

7. The method of claim 5, wherein the expansion turbine further comprises or is coupled to a compressor.

8. The method of claim 7, comprising the compressor in or coupled to the expansion turbine generating a compressed flow stream fluidly connected to the intercooler.

9. The method of claim 7, wherein the method further comprises connecting a generator within the expansion turbine to provide power to one or more ancillary facility components in the fuel cell system or to supplement power supplied to an external load. 10 . The method of claim 5 , further comprising limiting operation of the fuel cell system in the warm-up mode when an amount of coolant in the coolant storage module is below a second threshold amount.

11. The method of claim 5, further comprising operating the fuel cell system in the warm-up mode for a second predetermined operating time limit when the amount of coolant in the coolant storage module is above a second threshold amount.

12. The method of claim 11, wherein the second predetermined operation time limit is longer than the first predetermined operation time limit.

13. The method according to claim 11 further comprises, when the amount of coolant in the coolant storage module is higher than a second threshold amount, continuously operating the fuel cell system in the warming mode until the amount of coolant in the coolant storage module drops below a third threshold amount.

14. The method of claim 12, wherein the method further comprises determining the amount of coolant in the coolant storage module by measuring with a level sensor. 15 . The method of claim 12 , wherein the method further comprises determining the amount of the coolant by calculating the amount of coolant in the coolant storage module from data regarding operation of the fuel cell system.

16. The method of claim 7, wherein the compressor comprises an exhaust module compressor in the exhaust module, the exhaust module compressor configured to pressurize a flow entering a tail gas burner in the exhaust module.

17. A method of operating a fuel cell system, the fuel cell system comprising: a fuel cell assembly having an anode inlet, a cathode inlet, an anode exhaust gas, and a cathode exhaust gas; a coolant storage module configured to provide coolant to the fuel cell assembly; a thermal module in fluid connection with the fuel cell assembly and the coolant storage module, the thermal module comprising a condenser and a separator; an expansion turbine receiving the expanded exhaust gas flow; wherein said expanded exhaust gas stream comprises at least said cathode exhaust gas stream exiting a heat module separator and a fluid stream exiting a heat module condenser; The method comprises: providing coolant from the coolant storage module to the fuel cell assembly; providing an anode gas flow to an anode inlet of the fuel cell assembly; providing a cathode gas flow to a cathode inlet of the fuel cell assembly; operating the thermal module condenser and the thermal module separator to provide coolant to the coolant storage module; and, directing the expanded exhaust gas stream to the expansion turbine and operating the expansion turbine to generate an electrical output; in; The expanded exhaust gas stream includes at least a portion of the anode gas purge stream; and, The method further includes combusting at least a portion of the anode gas purge flow to increase the temperature of the expanded exhaust gas flow before the expanded exhaust gas flow is directed to the expansion turbine, wherein the fuel cell system further comprises one or more fans coupled to the thermal module condenser; and operating the fuel cell system in a warm-up mode for a predetermined time period less than or equal to a first predetermined operating time limit when the amount of coolant in the coolant storage module is below a first threshold amount; and Wherein the warm-up mode includes controlling the one or more fans to reduce a set point of the one or more fans below a predetermined threshold level to increase an exit temperature of the fluid flow from the condenser.

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