HYBRID COOLING SYSTEM FOR FUEL CELL

Abstract

A hybrid cooling system for a fuel cell vehicle uses evaporative cooling to supplement a radiator. Liquid water produced by the fuel cell is used by the evaporative cooling system. A vacuum pump reduces the pressure in a cooling unit to increase the evaporation rate of the liquid water. A control system manages the collection of liquid water during periods of low fuel cell power demand for use during periods of high fuel cell power demand.

Description

AREA OF TECHNOLOGY

[0001] The disclosure relates to a hybrid cooling system for a vehicle fuel cell. In particular, this disclosure relates to the use of evaporative cooling to supplement a radiator. GENERAL STATE OF THE ART

[0002] The amount of power required by a vehicle varies over time. During acceleration uphill, a high level of power is needed for propulsion. The drive system should be designed to generate this amount of power. However, steady-state operation generally requires only a small fraction of this amount of power. SUMMARY

[0003] A fuel cell cooling system includes a fuel cell, a water storage tank, a cooling unit, a coolant pump, and a vacuum pump. The fuel cell is configured to generate electricity and produce water. The fuel cell has a coolant inlet and a coolant outlet. The water storage tank is configured to store liquid water produced by the fuel cell. The cooling unit is configured to receive liquid water from the water storage tank and extract heat from the coolant by evaporating the liquid water. The coolant pump is configured to circulate the coolant from the coolant outlet through the cooling unit to the coolant inlet. The vacuum pump is configured to reduce the pressure in the cooling unit to facilitate the evaporation of the liquid water.A water control valve can be configured to control the flow rate of liquid water from the water tank to the cooling unit. A separator can be configured to separate liquid water from water vapor and direct the liquid water to the water storage tank. A separator bypass valve can selectively direct the water generated by the fuel cell to the separator. A water drain valve can selectively drain liquid water from the water storage tank, bypassing the cooling unit. A cooler can extract heat from the coolant by convection with ambient air. A selection valve can selectively direct a portion of the coolant flow from the coolant outlet to the coolant inlet through the cooling unit, with the remainder of the coolant flow passing through the cooler.

[0004] One method for controlling a fuel cell cooling system involves directing a coolant from a coolant outlet of the fuel cell through a cooling unit to a coolant inlet of the fuel cell. In response to the coolant temperature exceeding a first threshold, liquid water is released from a water storage tank into the cooling unit. A vacuum pump is used to reduce the pressure in the cooling unit, causing the liquid water to evaporate and extract heat from the coolant. The rate at which the liquid water is released into the cooling unit can be controlled based on the pressure within the unit. The pressure in the cooling unit can be controlled to a setpoint pressure based on the coolant temperature. Water produced by the fuel cell can be directed to a separator.Liquid water from the separator can be routed to the water storage tank. Coolant from the fuel cell's coolant outlet can be routed through a cooler to the fuel cell's coolant inlet, bypassing the cooling system. Liquid water from the water storage tank can be drained in response to an ambient temperature falling below a second threshold.

[0005] A vehicle includes a fuel cell, a coolant pump, a water storage tank, and a control unit. The fuel cell generates electricity and produces water. It has a coolant inlet and a coolant outlet. The coolant pump circulates coolant from the outlet through a cooling unit to the inlet. The water storage tank holds liquid water produced by the fuel cell. The control unit is programmed to release liquid water from the storage tank into the cooling unit when the coolant temperature exceeds a predefined threshold. It then instructs a vacuum pump to reduce the pressure in the cooling unit, causing the liquid water to evaporate and thus extract heat from the coolant.A separator separates liquid water from the water produced by the fuel cell and directs the liquid water to the water storage tank. The controller can be programmed to bypass the separator in response to a water level in the storage tank exceeding a second threshold. The controller can also be programmed to adjust the rate at which liquid water is released into the cooling system based on a pressure in the cooling system and a second coolant temperature. A drain valve can empty liquid water from the storage tank in response to an ambient temperature falling below a third threshold. The controller can also be programmed, based on a third coolant temperature, to direct a variable portion of the coolant flow rate through the radiator, bypassing the cooling system. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of a fuel cell vehicle. Fig. 2 is a schematic representation of a fuel cell cooling system designed for use in the fuel cell vehicle made of Fig. 1 is suitable. Fig. 3 is a cross-section of a cooling device intended for use in the fuel cell cooling system made of Fig. 2 is suitable. Fig. 4 is a flowchart for a process for controlling the fuel cell cooling system from Fig. 2, while the vehicle is in operation. Fig. 5 is a flowchart for a process for controlling the fuel cell cooling system from Fig. 2, while the vehicle is not in operation. DETAILED DESCRIPTION

[0006] Depending on the requirements, detailed embodiments of the present invention are disclosed here; however, it is understood that the disclosed embodiments are merely exemplary of the invention, which can be implemented in various and alternative forms. The figures are not necessarily to scale; some features may be greatly enlarged or reduced to show details of specific components. Therefore, specific structural and functional details disclosed in this document are not to be interpreted as limiting, but merely as a representative basis to teach those skilled in the art the diverse applications of the present invention.

[0007] Fig. Figure 1 illustrates some of the components of a hydrogen fuel cell vehicle. The illustrated vehicle has four wheels, at least two of which are drive wheels. Hydrogen fuel (H2) is stored in a hydrogen storage tank. The hydrogen is fed to a fuel cell, where it combines with oxygen (O2) to form water (H2O) and electricity. The oxygen can be taken from ambient air, which is a mixture of nitrogen (N2), oxygen, and small amounts of many other substances. The nitrogen and other substances can be expelled from the fuel cell along with the water. In this document, the term "water" without modifier refers to any form of H2O, including ice, liquid water, water vapor, and mixtures of the foregoing.The electrical energy generated by the fuel cell flows into a power electronics unit 18, which conditions it and directs it to a battery 20 and / or an electric motor 22. The motor converts the electrical power into mechanical power, which is directed to the drive wheels. Electrical energy can flow into the battery 20 at certain times, while at other times it can flow from the battery 20. Similarly, electrical energy can flow into the motor 22 when needed to propel the vehicle and can flow out of the motor during regenerative braking. The control unit 24 can manipulate actuators of the aforementioned components and other components discussed below based on input from sensors and a vehicle operator. Some of the algorithms used by the control unit 24 are discussed in detail below.

[0008] Cooling fuel cells is very challenging due to the small initial temperature difference (ITD) (ITD = coolant inlet temperature - air inlet temperature). This necessitates the use of a large radiator, the size of which may be limited by the front of the vehicle. To address this challenge, a complementary two-phase cooling system utilizing the fuel cell's exhaust water is proposed. The exhaust water is passed through a heat exchanger (cooling unit) where a vacuum pump is used to cause the water to evaporate at the temperature of the incoming coolant from the fuel cell stacks, thus cooling the coolant and providing additional cooling capacity to the system. At low loads, the complementary cooling is not required, as the fuel cell's exhaust consists primarily of liquid water.Under high loads, additional cooling is required, while the fuel cell exhaust water is primarily in vapor form and therefore not useful. A tank is used to store the exhaust water, if available, so that it can be released to the cooling system as needed during high-load maneuvers.

[0009] Fig. 2 is a schematic representation of a fuel cell cooling system designed for use in the vehicle made of Fig. 1 is suitable. The representation is intended to convey connections between components, but not sizes, shapes, or relative physical positions of components. The hydrogen inlet and electrical connections of the fuel cell 16 are shown in Fig. 2 omitted. The discharged water from the fuel cell 16 is expelled via a pipe 30. The coolant pump 32 pumps a coolant from a coolant outlet 34 of the fuel cell to a coolant inlet 36 of the fuel cell. Inside the fuel cell, the coolant flows from the coolant inlet 36 to the coolant outlet 34 and absorbs heat to maintain an internal temperature of the fuel cell within an acceptable range. The amount of heat that needs to be absorbed varies depending on the operating conditions. When the fuel cell is required to generate a high level of electrical energy, the rate at which heat must be removed increases.

[0010] The coolant is pumped from the fuel cell outlet to the fuel cell inlet via one or more of three possible paths. The bypass valve 38 can be a two-position selector valve that directs coolant either through the cooler 40 to the cooler outlet 42 or directly back to the pump inlet 44. In some embodiments, the bypass valve can be a proportional valve that splits the flow between these two paths in a controlled manner. A portion of the flow can be directed through the cooling device 46 to the cooling device outlet 48. The selector valve 50 can be a proportional valve that controls what portion of the flow enters the pump inlet 44 from the cooling device outlet 48, with the remainder coming from a cooler outlet 42. In some embodiments, the valve 50 can act as an on / off valve to block all coolant flow to the cooling device 46.For example, the flow rate through the cooler 40 can be nominally about 320 liters per minute, while the flow rate through the cooling device 46 can be in the range of zero to about 20 liters per minute.

[0011] The cooler 40 extracts heat from the coolant to the ambient air via convection. A fan can force the ambient air through the fins of the cooler 40. The amount of heat extracted from the coolant as it flows through the cooler depends on the ambient air temperature, the temperature of the coolant entering the cooler, the coolant flow rate through the cooler, the air flow rate through the cooler, and the cooler size. The cooler can be sized to dissipate the heat generated by the fuel cell 16 and return the coolant at an acceptable temperature during most operating conditions, except during periods when the fuel cell 16 is operating at its highest rated power.

[0012] The cooling device 46 extracts heat from the coolant via evaporative cooling. As described below, liquid water is dripped from the water storage tank 52 onto coils at a rate controlled by the water control valve 54. The vacuum pump 56 generates a pressure below atmospheric pressure within the cooling device 46, which lowers the boiling point of water within the cooling device. This causes the liquid water to evaporate much faster than at atmospheric pressure. As the liquid water evaporates, it absorbs heat from the coolant flowing through the cooling device 46. The coolant exits the cooling device outlet 48 at a lower temperature than when it entered the cooling device. The cooling capacity of the cooling device 46 supplements the cooling capacity of the radiator 40 when the fuel cell is operated at or near its rated power.

[0013] The water storage tank 52 is filled using liquid water produced by the fuel cell 16. The exhaust from the fuel cell 16 can contain a mixture of liquid water, water vapor, and other gaseous compounds. The separator 58 separates the liquid water from the gaseous components and directs the liquid water to the water storage tank 52, while directing the gaseous components to the exhaust manifold 60, from where they are released into the environment. In the illustrated embodiment, gravity causes water to flow from the separator to the water storage tank. In alternative embodiments, a small pump can be used, allowing the water storage tank to be positioned higher than the separator. To prevent overfilling of the water storage tank, the separator bypass valve 62 can divert the exhaust directly to the exhaust manifold when the water storage tank is full.The drain valve 64 can be used to drain liquid water from the water storage tank 52 when the ambient temperature is near or below freezing, in order to prevent damage caused by the expansion of water when it freezes in the tank. In alternative embodiments, the drain valve 64 could also be used instead of the separator bypass valve 62 to prevent overfilling of the water storage tank 52.

[0014] In the embodiment from Fig. 2. During periods of high cooling demand, the coolant flows in parallel through the radiator and the cooling device. In other words, the coolant flow is divided so that a portion (usually less than 10%) flows through the cooling device and the remainder flows through the radiator. The selector valve 50 limits the flow through the cooling device when evaporative cooling is not required. The selector valve 50 can be an on / off valve that limits the flow to zero when evaporative cooling is not required. In other embodiments, the relative amount could be controlled by a valve at the point where the two flows diverge. In still other embodiments, the coolant could flow in series through the radiator and the cooling device.

[0015] Fig. Figure 3 illustrates a cooling device 46, which is a forced convection refrigerant-coolant heat exchanger, with water acting as the refrigerant. The cooling device can be a crossed-flow heat exchanger, with the hotter refrigerant inlet meeting the outgoing vapor / liquid water to ensure complete evaporation of the water, resulting in optimal cooling performance. The water section of the cooling device is connected to the vacuum pump 56 via a vapor port 74. Careful control of the speed of the vacuum pump 56 and the position of the proportional valve 54 provides a low pressure inside the cooling device, so that the temperature of the refrigerant entering the cooling device is significantly above the water saturation temperature at the cooling device pressure. The liquid water evaporates rapidly. As it evaporates, it absorbs heat from the refrigerant.

[0016] Fig. 4 is a flowchart for a process for controlling the fuel cell cooling system from Fig. 2. This process is executed at regular intervals while the vehicle is in operation by a controller, such as controller 24. For example, the process can be executed every 100 milliseconds in response to interrupt signals. In some embodiments, the process can be divided into separate subprocesses that are executed independently but can share data. Independent subprocesses can be executed on a single controller or on separate interacting controllers. The operations can be performed in a different order than shown. Fig. 4 will be carried out.

[0017] At 80, the control unit checks whether the temperature of the coolant at the fuel cell inlet T is within the set range. in below a first threshold temperature T h1 lies. T h1is a calibratable value that indicates the lower endpoint of a normal operating range of coolant temperatures.

[0018] Thresholds such as T h1 They can be constants or they can be calculated values ​​that vary based on conditions. If T in < T h1 Then the bypass valve 38 is set at 82 so that the coolant from the fuel cell outlet is routed directly back to the coolant pump, bypassing the radiator. This reduces the time required for the coolant to warm up to its normal operating range. If T in >= T h1 , then the bypass valve 38 at 84 is adjusted so that the coolant is routed through the radiator.

[0019] At 86, the control unit checks whether the temperature of the coolant at the fuel cell outlet T is correct. out below a second threshold temperature T h2 lies. T h2is a calibratable value that indicates the upper endpoint of the normal operating range of coolant temperatures, above which the fuel cell may lose performance. If T out < T h2 The control system takes a series of measures so that the cooling system is not used for cooling. (The control system can also check for a possibility of reducing parasitic load predicted by the vehicle connectivity system. Through vehicle connectivity and knowledge of the driving cycle, the control system can choose to still use evaporative cooling at relatively moderate cooling loads with Tout < Th, if the power consumption of the vacuum pump is less than that of the radiator fans.) If the control system previously determined at 80 that T in < T h1 , the control system can proceed with these measures without separately checking whether T out < T h2At position 88, the control unit adjusts the selector valve 50 to block the entire coolant flow through the cooling system. At position 90, the control unit closes the water control valve 54, preventing water from the water storage tank from entering the cooling system. At position 92, the vacuum pump 56 is switched off.

[0020] At 94, the controller checks whether the ambient temperature T amblower than the freezing point of water. The threshold may be slightly offset from the freezing point to provide a safety margin. If so, the drain valve 64 opens at 96 to drain the liquid water from the water storage tank. If liquid water were retained at sub-zero temperatures, it could freeze, which could cause problems due to the expansion when ice forms from liquid water. Additionally, the separator bypass valve 62 closes, preventing any additional liquid water from being directed to the water storage tank. If the temperature at 94 is above freezing, the controller closes valve 64 at 100. The risk of water freezing in the water storage tank is not limited to times when the vehicle is in operation. Fig.Figure 5 is a flowchart for an accompanying process that is executed periodically when the vehicle is not in operation. In some embodiments, the drain valve 64 can be passively controlled by a thermostat instead of being actively controlled by the control unit.

[0021] At 102, the controller checks whether the water storage tank 52 is full. If so, the controller at 100 closes valve 64 to prevent overfilling. If not, the controller at 104 opens valve 64. When valve 64 is open, water produced by the fuel cell flows to the separator 58, where the liquid water is separated from other exhaust components and directed back into the water storage tank 52. In alternative embodiments, overfilling could be prevented by controlling the drain valve 64 or by a passive overflow pipe.

[0022] If the control at 86 determines that T out >= T h2Then the controller takes a series of actions to operate the evaporative cooling system to supplement the cooler's capacity. At 104, the controller checks whether the water storage tank 52 is empty. If so, the evaporative cooling system is unable to provide additional cooling, so the fuel cell must operate at limited capacity at 106. If liquid water is available, the controller switches on the vacuum pump at 108, which reduces the pressure in the sealed housing of the cooling unit. At 110, the controller adjusts the selector valve 50 to allow coolant to flow through the cooling unit. At 112, the controller proposes a target pressure P. targetin a calibration table based on the coolant inlet temperature of the cooling unit. Lower coolant inlet temperatures lead to lower setpoint pressures, i.e., a higher demand on the vacuum pump 56 and a higher limit on the valve 54. At 114, the water control valve 54 is operated in a closed-loop manner based on the difference between a measured cooling unit pressure P chiller and the target pressure P targetThe system is controlled, resulting in a saturation temperature that is significantly lower than the coolant inlet temperature. This difference represents the error term of the closed-loop control scheme. If the measured pressure is higher than the set pressure, the valve is adjusted to reduce the water flow rate, allowing the vacuum pump to lower the cooling system pressure. If the measured pressure is lower than the set pressure, the valve is adjusted to increase the water flow rate, allowing the actual pressure to match the set pressure. While evaporative cooling is used, valve 62 at 102 is open to allow additional water to flow into the water storage tank. However, when the fuel cell is operated above its normal operating temperature range, most of the water produced is in vapor form.The system relies primarily on liquid water collected under previous operating conditions.

[0023] Although exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms encompassed by the claims. The terms used in the description are descriptive rather than limiting, and it is understood that various modifications may be made without departing from the spirit and scope of these disclosed items.

[0024] As previously described, the features of different embodiments can be combined to form further embodiments of the invention, which may not be expressly described or illustrated. Although various embodiments may have been described in such a way that they offer advantages or are preferred over other embodiments or implementations according to the prior art with respect to one or more desired properties, the person skilled in the art understands that compromises may be made with respect to one or more features or properties in order to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, among others, strength, durability, marketability, appearance, installation, size, maintainability, weight, manufacturability, ease of assembly, etc.Therefore, embodiments which are described as less desirable than other embodiments or implementations according to the prior art with respect to one or more properties are not outside the scope of the disclosure and may be desirable for specific applications.

[0025] According to the present invention, a fuel cell cooling system is provided comprising: a fuel cell configured to generate electricity and produce water, the fuel cell having a coolant inlet and a coolant outlet; a water storage tank configured to store liquid water produced by the fuel cell; a cooling device configured to receive liquid water from the water storage tank and to extract heat from a coolant by evaporating the liquid water; a coolant pump configured to circulate the coolant from the coolant outlet through the cooling device to the coolant inlet; and a vacuum pump configured to reduce pressure in the cooling device to facilitate the evaporation of the liquid water.

[0026] According to one embodiment, the invention is further characterized by a water control valve configured to control a flow rate of liquid water from the water storage tank to the cooling device.

[0027] According to one embodiment, the invention is further characterized by a separator configured to separate liquid water from water vapor and to direct the liquid water to the water storage tank.

[0028] According to one embodiment, the invention is further characterized by a separator bypass valve configured to selectively direct the water generated by the fuel cell to the separator.

[0029] According to one embodiment, the invention is further characterized by a water drain valve configured to selectively drain liquid water from the water storage tank, bypassing the cooling device.

[0030] According to one embodiment, the invention is further characterized by a cooler configured to extract heat from the coolant by convection with ambient air.

[0031] According to one embodiment, the invention is further characterized by a selection valve configured to selectively direct a portion of the coolant from the coolant outlet to the coolant inlet through the cooling device, with a remainder of the coolant being directed through the radiator.

[0032] According to the present invention, a method for controlling a fuel cell cooling system comprises: directing coolant from a coolant outlet of a fuel cell through a cooling device to a coolant inlet of the fuel cell; and, in response to a coolant temperature exceeding a first threshold, releasing liquid water from a water storage tank into the cooling device and using a vacuum pump to reduce pressure in the cooling device in order to evaporate the liquid water to extract heat from the coolant.

[0033] In one aspect of the invention, the rate at which the liquid water is released into the cooling device is controlled based on a pressure in the cooling device.

[0034] In one aspect of the invention, the pressure in the cooling device is controlled to a target pressure which is based on a temperature of the coolant.

[0035] In one aspect of the invention, the method involves directing water produced by the fuel cell to a separator and directing liquid water from the separator to the water storage tank.

[0036] In one aspect of the invention, the method involves directing coolant from the coolant outlet of the fuel cell through a cooler to the coolant inlet of the fuel cell, bypassing the cooling device.

[0037] In one aspect of the invention, the method involves emptying liquid water from the water storage tank in response to an ambient temperature falling below a second threshold.

[0038] According to the present invention, a vehicle is provided comprising: a fuel cell configured to generate electricity and produce water, the fuel cell having a coolant inlet and a coolant outlet; a coolant pump configured to circulate a coolant from the coolant outlet through a cooling device to the coolant inlet; a water storage tank configured to store liquid water produced by the fuel cell; and a controller programmed to release liquid water from the water storage tank into the cooling device in response to a first temperature of the coolant exceeding a first threshold, and to command a vacuum pump to reduce pressure in the cooling device to evaporate the liquid water in order to extract heat from the coolant.

[0039] According to one embodiment, the invention is further characterized by a separator configured to separate liquid water from the water produced by the fuel cell and to direct the liquid water to the water storage tank.

[0040] According to one embodiment, the control system is programmed to bypass the separator in response to a water level in the water storage tank exceeding a second threshold.

[0041] According to one embodiment, the control is further programmed to set a rate at which the liquid water is released into the cooling device based on a pressure in the cooling device and a second temperature of the coolant.

[0042] According to one embodiment, the invention is further characterized by a drain valve to empty liquid water from the water storage tank in response to an ambient temperature falling below a third threshold value.

[0043] According to one embodiment, the invention is further characterized by a cooler, and wherein the control is further programmed to direct a variable part of a coolant flow rate through the cooler based on a third temperature of the coolant, thereby bypassing the cooling device.

Claims

[1] Fuel cell cooling system, comprising: a fuel cell configured to generate electricity and water, wherein the fuel cell has a coolant inlet and a coolant outlet; a water storage tank configured to store liquid water produced by the fuel cell; a cooling device configured to receive liquid water from the water storage tank and to extract heat from a coolant by evaporating the liquid water; a coolant pump configured to circulate the coolant from the coolant outlet through the cooling system to the coolant inlet; and a vacuum pump configured to reduce pressure in the cooling system to facilitate the evaporation of the liquid water. [2] Fuel cell cooling system according to claim 1, further comprising a water control valve configured to control a flow rate of liquid water from the water storage tank to the cooling device. [3] Fuel cell cooling system according to claim 1, further comprising: a separator configured to separate liquid water from water vapor and to direct the liquid water to the water storage tank; and a separator bypass valve configured to selectively direct the water generated by the fuel cell to the separator. [4] Fuel cell cooling system according to claim 1, further comprising a water drain valve configured to selectively drain liquid water from the water storage tank, bypassing the cooling device. [5] Fuel cell cooling system according to claim 1, further comprising: a cooler configured to extract heat from the coolant by convection with ambient air; and a selection valve configured to selectively direct a portion of the coolant flow from the coolant outlet to the coolant inlet through the cooling device, with the remainder of the coolant flow passing through the radiator. [6] Method for controlling a fuel cell cooling system, comprising: Guiding a coolant from a coolant outlet of a fuel cell through a cooling device to a coolant inlet of the fuel cell; and In response to a coolant temperature exceeding an initial threshold, liquid water is released from a water storage tank into the cooling system, and a vacuum pump is used to reduce pressure in the cooling system to evaporate the liquid water and extract heat from the coolant. [7] Method according to claim 6, wherein a rate at which the liquid water is released into the cooling device is controlled on the basis of a pressure in the cooling device. [8] Method according to claim 7, wherein the pressure in the cooling device is controlled to a target pressure based on a temperature of the coolant. [9] Method according to claim 6, further comprising directing coolant from the coolant outlet of the fuel cell through a cooler to the coolant inlet of the fuel cell, bypassing the cooling device. [10] Method according to claim 6, further comprising emptying liquid water from the water storage tank in response to an ambient temperature falling below a second threshold. [11] Vehicle, comprising: a fuel cell configured to generate electricity and water, wherein the fuel cell has a coolant inlet and a coolant outlet; a coolant pump configured to circulate coolant from the coolant outlet through a cooling device to the coolant inlet; a water storage tank configured to store liquid water produced by the fuel cell; and a control system programmed to release liquid water from the water storage tank into the cooling system and to command a vacuum pump in response to an initial coolant temperature exceeding an initial threshold. to reduce the pressure in the cooling system in order to evaporate the liquid water in order to extract heat from the coolant. [12] Vehicle according to claim 11, further comprising a separator configured to separate liquid water from the water produced by the fuel cell and to direct the liquid water to the water storage tank, and wherein the control is programmed to bypass the separator in response to a water level in the water storage tank exceeding a second threshold. [13] Vehicle according to claim 11, wherein the control is further programmed to set a rate at which the liquid water is released into the cooling device based on a pressure in the cooling device and a second temperature of the coolant. [14] Vehicle according to claim 11, further comprising a drain valve configured to drain liquid water from the water storage tank in response to an ambient temperature falling below a third threshold. [15] Vehicle according to claim 11, further comprising a radiator, and wherein the control is further programmed to direct a variable part of a coolant flow rate through the radiator based on a third temperature of the coolant, bypassing the cooling device.

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