Method and device for thermal management of a fuel cell system of a vehicle
Patent Information
- Application Number
- EP2023820829
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-09
- Filing Date
- 2023-12-05
- Publication Date
- 2025-10-15
AI Technical Summary
Fuel cell systems in vehicles face inefficiencies due to limited thermal management capabilities, leading to overheating and reduced service life, especially as the fuel cell ages, and require a balance between heat dissipation and energy consumption to maintain optimal performance.
A method and device for thermal management that estimates thermal output based on driving situations and environmental conditions, using ECO and Power modes to optimize cooling performance, with an energy management system determining the necessary power input to dissipate waste heat efficiently, minimizing auxiliary energy use and extending fuel cell lifespan.
The solution allows for optimal thermal management, reducing overheating, minimizing energy consumption, and extending the service life of fuel cell systems by dynamically adjusting cooling performance based on current and predicted driving conditions, ensuring efficient hydrogen use and maintaining fuel cell performance.
Smart Images
Figure 1.1
Abstract
Description
[0001] Method and device for thermal management of a fuel cell system of a vehicle
[0002] The invention relates to a method for thermal management of a fuel cell system of a vehicle according to the preamble of claim 1 and to a device for thermal management of a fuel cell system of a vehicle according to claim 10.
[0003] A fuel cell system generates waste heat during operation, which must be dissipated by a cooling system. In cold outside temperatures or during warm-up, the fuel cell system must first be warmed up. A fuel cell system therefore requires a thermal management system to ensure it always operates within the correct temperature range.
[0004] The cooling capacity of a thermal management system has limits. However, the thermal management system can dissipate varying amounts of heat to the environment depending on the ambient conditions (outside temperature) and driving situation (driving speed, traffic). The fuel cell itself loses efficiency over the course of its service life and thus generates increasing amounts of waste heat while generating approximately the same amount of electrical energy. If a thermal management system for a fuel cell system were designed to dissipate the maximum possible waste heat from the fuel cell system in all operating conditions and at all stages of the fuel cell's aging process, it would be enormously large, heavy, and expensive, and thus inefficient. A moderately designed thermal management system may therefore result in the fuel cell's full performance not being available in all operating conditions. This can lead to overheating of the fuel cell system and a reduction in its service life.Furthermore, in some situations, it's possible that the waste heat could be dissipated, but the energy demand for the auxiliary units used would be so high that it doesn't make sense from an energy perspective. Therefore, the output of the fuel cell system must be reduced in such situations.
[0005] US 10 369 899 B2 describes systems and methods for determining battery heating conditions and preheat lead times of at least one minute or more based on input parameters and sets of input parameters to proactively and dynamically heat a secondary battery such that the battery has a specific power output and a specific performance level when used in an electric or hybrid vehicle application.
[0006] The invention is based on the object of providing a novel method and a novel device for thermal management of a fuel cell system of a vehicle.
[0007] The object is achieved according to the invention by a method for thermal management of a fuel cell system of a vehicle having the features of claim 1 and by a device for thermal management of a fuel cell system of a vehicle having the features of claim 10.
[0008] Advantageous embodiments of the invention are the subject of the subclaims.
[0009] In a method according to the invention for thermal management of a fuel cell system of a vehicle, a thermal output of an overall cooling system of the vehicle is estimated using a physical model, taking into account a current driving situation of the vehicle and existing ambient conditions. According to the invention, a thermal output in an ECO mode, which can be dissipated without switching on one or more auxiliary consumers, including at least one fan and, for example, including at least one valve, and a thermal output of the overall cooling system in a POWER mode, which can be dissipated when switching on one or more auxiliary consumers, including at least one fan and, for example, including at least one valve, are determined, wherein in an energy management system, which, for example, is determined with the aid of a current battery state of charge (SOC) and current driving resistances, which are the sum of air,Rolling and gradient resistance are combined, a fuel cell target power is calculated that is independent of the heat output, a target power that can currently be accessed by the fuel cell system and, if necessary, limited by the heat output is determined on the basis of this heat output, and a decision is made as to whether the fuel cell system is to be operated in ECO mode or in Power mode, whereby a heuristic logic is used to determine how much energy the auxiliary consumers required for cooling currently require in order to determine a characteristic value that states how much electrical power must currently be used to dissipate a certain heat output, whereby if the value exceeds 1 kW of electrical power per kW of dissipated heat output, the power of the fuel cell system is not increased.
[0010] In one embodiment, it is provided that at a value of significantly less than 1 kW of electrical power per kW of dissipated heat output, in particular at a maximum of 0.2 kW of electrical power per kW of heat output, the energy management system increases the requested target power of the fuel cell.
[0011] In one embodiment, a driving speed and / or a temperature of a cooling medium is taken into account for the current driving situation.
[0012] In one embodiment, an ambient temperature is taken into account as an ambient condition.
[0013] In one embodiment, the energy management system calculates the possible electrical power of the fuel cell based on a characteristic map that takes into account the current aging of the fuel cell system and requests this from the fuel cell.
[0014] In one embodiment, an estimate for a mass flow of the cooling medium to be provided by one or more pumps is estimated from a current waste heat of the fuel cell system, which is taken into account in the estimation of heat that can be dissipated by one or more coolers in addition to the current driving situation and the existing ambient conditions.
[0015] In one embodiment, when the waste heat from the fuel cell system is low, the required target temperature at the fuel cell system inlet can be adjusted using one or more valves.
[0016] In one embodiment, when determining the additional waste heat required for the at least one fan, the current waste heat of the fuel cell system and the heat that can be dissipated by one or more coolers are taken into account. In one embodiment, the waste heat required for the at least one fan is used to estimate a mass flow that must be generated by the at least one fan in order to determine an energy-optimal distribution of the mass flows among the fans and a corresponding control of the fans.
[0017] In one embodiment, a prediction is made for an upcoming route, wherein a course of the expected driving speed of the vehicle and a course of the expected ambient temperature are determined on the basis of a planned route using a web-based traffic service and / or a prediction module, wherein a thermal model of the cooling system is used to determine, based on this data, how the achievable cooling capacity of the cooling system and the corresponding characteristic value will develop in ECO mode and in power mode for the upcoming route, and on this basis an optimal performance trajectory for the fuel cell system is planned, taking into account the route and the external environmental influences.
[0018] According to one aspect of the present invention, a device for thermal management of a fuel cell system of a vehicle is proposed, comprising an energy management system of the fuel cell system and a vehicle control system which is / are configured to carry out the method according to one of the preceding claims.
[0019] - The thermal management estimates the currently possible cooling performance of the cooling system in two performance levels (ECO and Power)
[0020] - via an interface to an energy management system, a central control unit is informed about the currently available cooling capacity,
[0021] - a key figure on the currently required power input per kilowatt of cooling capacity dissipated provides information on whether investing additional energy will also result in improved cooling of the system.
[0022] The thermal management of a fuel cell commercial vehicle determines the currently available cooling capacity of the cooling system, taking into account the current driving and ambient conditions. It can therefore provide information on the cooling potential without additional energy demand (ECO mode) and with additional energy demand (Power mode), for example, from fans. This information is made available to the energy management system via an interface, allowing the most energy-efficient operating points of the fuel cell system to be determined. A specific value of the power currently drawn by auxiliary units per kW of excess heat dissipated is used to determine whether more cooling capacity is beneficial or not.
[0023] The service life of fuel cell systems depends largely on good and consistent temperature control within the fuel cell's optimal comfort zone. The more often overheating is avoided, the longer the service life of the fuel cell will be. The interface according to the invention allows the fuel cell to be operated more reliably within the optimal temperature range. The use of hydrogen as a fuel should be as efficient as possible. Operating conditions in which unnecessary amounts of hydrogen are consumed without generating any benefit for driving performance or the vehicle's electrical system should be avoided. Therefore, the power demand on the fuel cell must be regulated so that the energy requirements of the auxiliary units are as optimal as possible.The present invention improves both of these aspects and allows for optimal design, as overheating and inefficient operating states of the fuel cell can be avoided by transmitting the current or anticipated states of the thermal management system to the energy management system. The invention minimizes the necessary design reserves of the thermal management system and allows for maximum efficiency in thermal management; thus, it is always used almost optimally.
[0024] Embodiments of the invention are explained in more detail below with reference to drawings.
[0025] Showing:
[0026] Fig. 1 is a schematic view of a method for estimating a dissipable heat output with and without fan activation in a fuel cell vehicle,
[0027] Fig. 2 is a schematic view of a reactive method for thermal management of the fuel cell vehicle, and
[0028] Fig. 3 is a schematic view of a predictive method for thermal management of the fuel cell vehicle, Fig. 4 is a schematic view of a simplified model for estimating the cooling power dissipated by a vehicle radiator,
[0029] Fig. 5 is a schematic view of a method for estimating air mass flows, and
[0030] Fig. 6 shows a schematic progression of a driving performance horizon FLH with predictive control.
[0031] Corresponding parts are provided with the same reference numerals in all figures.
[0032] Figure 1 is a schematic view of a method for estimating dissipable heat power with and without fan activation in a fuel cell vehicle.
[0033] Figure 2 is a schematic view of a reactive method for thermal management of the fuel cell vehicle.
[0034] The fuel cell vehicle has a vehicle controller 1 configured to control the thermal management system. Based on a physical model, the vehicle controller estimates the currently dissipated heat output of the entire cooling system, for example, the heat Q dissipated by one or more coolers 5, taking into account the current driving situation, for example, a driving speed v and a temperature TKM of a cooling medium, and the prevailing ambient conditions, for example, an ambient temperature Tu. K I , K2.
[0035] In a module 12 for performance-oriented and SOC-based energy distribution of a high-voltage battery, a current state of charge SOC of the battery and current driving resistances AFW, which are composed of the sum of air, rolling and gradient resistance, are taken into account to determine a fuel cell target power without thermal limitation.
[0036] The cooling water mass flows can be determined based on the current pump speed, while the air mass flows are known from simulation calculations, measurements, and empirical values. Any inaccuracies can be compensated for using a downstream correction factor or correction function.
[0037] For this estimation, the model uses, for example, characteristic maps relating to the thermal conductivity of the cooler manufacturers at a constant, specified air mass flow, which can be assumed to be different for ECO mode and power mode, through the cooler for the possible heat dissipation QKI, QK2. Figure 4 shows a schematic view of a simplified model for estimating the cooling capacity dissipated by a cooler 5. To determine the correction value KoW, a difference between a cooling water inlet temperature Tw and an air inlet temperature TL of the cooler 5 is formed and multiplied by the thermal conductivity WLW determined by the characteristic map KF, which this is calculated based on a cooling water mass flow m w and an air mass flow m L of the cooler.
[0038] For estimating cooling water mass flows m w From the pump speed n the following formulas can be used:
[0039] 600
[0040] 2 * n * M * n
[0041] P ~ 60000
[0042] P Drive power (kW) p Operating pressure pump outlet (bar)
[0043] Q Volume flow (dm 3 / min) r|ges overall efficiency (-)
[0044] M Torque (Nm) n Pump speed (1 / min)
[0045] The density of the cooling water determines the cooling water mass flow m w for example in a known ratio to the volume flow.
[0046] The mass flow m w of a pump can be determined either from the input drive power and the generated operating pressure as in the formulas mentioned or by a linear relationship between pump speed and mass flow m w , which was previously determined by testing the system in question. The current mass flow m wto a maximum mass flow as the current pump speed to a maximum pump speed.
[0047] Figure 5 is a schematic view of a method for estimating air mass flows m L . The air mass flow m L through the coolers 6 can be calculated from a combination of simulation results SE, in particular for determining an air mass flow m LL by a fan 4 and characteristic maps KFEW with empirical values, in particular for determining an air mass flow m LFW from the airstream, as well as current ambient conditions such as driving speed v and ambient temperature Tu. A total air mass flow m < a y es can then be calculated as the sum of
[0048] Air mass flow m LL by the fan 4 and the air mass flow m LFW formed from the wind.
[0049] On the one hand, a heat output QECO is determined that can be dissipated without additional measures such as switching on one or more fans 4. In other words, the dissipable heat output QECO is determined, which results exclusively from the airflow. This results in a heat output value that represents the lowest energy consumption of the auxiliary consumers (ECO mode). On the other hand, a heat output QPOWER can be determined that can be dissipated including additional measures such as switching on one or more fans 4. This results in a heat output value that, although it represents an increased energy consumption of the auxiliary consumers, enables more power from the fuel cell (Power mode).
[0050] The vehicle control 1 for carrying out the thermal management has an interface 2 to an energy management system ENM of the fuel cell, which informs the energy management system ENM about these two currently possible thermal cooling capacities.
[0051] The energy management system ENM can in turn use this information to determine which electrical power can currently be drawn from the fuel cell. Using a characteristic map that also takes into account the current aging of the fuel cell system, the energy management system ENM can calculate the possible electrical power of the fuel cell and request this from the fuel cell. Depending on the current situation, the energy management system ENM can then decide whether the fuel cell should be operated at an operating point that requires the least energy for the ancillary units (thermal management in ECO mode) or whether the more energy-intensive Power mode is required. In addition, the vehicle control system 1 uses heuristic logic to determine how much energy the ancillary consumers required for cooling, such as pumps 6 and fans 4, currently require.From this, a characteristic value KW can be determined, which indicates how much electrical power must currently be used to dissipate a certain amount of heat.
[0052] In particular, an estimate for a mass flow m to be provided by one or more pumps 6 is made from a current waste heat QBZ of the fuel cell system. P of the cooling medium, which can be taken into account when estimating the heat QKI, QK2 that can be dissipated by one or more coolers 5 in addition to the current driving situation, for example the driving speed v and the temperature TKM of the cooling medium, and the existing ambient conditions, for example the ambient temperature Tu.
[0053] When determining additional waste heat QL required for at least one fan 4, a current waste heat QBZ of the fuel cell system and heat QKI, QK2 that can be dissipated by one or more coolers 5 can be taken into account.
[0054] From the waste heat QL required for at least one fan 4, a mass flow m L1 , m L2 be estimated, which is to be provided by at least one fan 4. From this, an energy-optimal distribution 9 of the mass flows m L1 , m L2 on the fans 4 and a corresponding control 3 of the fans 4 can be determined.
[0055] In certain situations, it is possible that the cooling system could generate a high cooling capacity by making heavy use of auxiliary units, such as fans 4, whereby the electrical energy consumption would be so high that the resulting additional fuel cell power would be completely used up or even exceeded.
[0056] In this case, only hydrogen consumption would increase without any positive effect on the high-voltage electrical system in the sense of a charging effect. The additional electrical power generated would be consumed directly by the auxiliary consumers. These situations should be avoided. This is possible using the thermal management parameter KW described above. If this
[0057] For example, if the KW parameter exceeds 1 kW of electrical power per kW of heat output, this indicates impractical operation. In this case, the ENM energy management system will not further increase the target power Ps of the fuel cell system, taking into account the thermal management limitations. If the value is significantly lower, for example, 0.2 kW of electrical power per kW of heat output, the ENM energy management system can increase the requested target power Ps of the fuel cell.
[0058] Figure 3 is a schematic view of a predictive method for thermal management of the fuel cell vehicle.
[0059] In addition to the current situation, the vehicle controller 1 can be configured to make a prediction for the upcoming route. Based on the planned route, the course v(t) of the expected vehicle speed can be determined using a web-based traffic service and / or another prediction module 7.
[0060] In addition, a gradient and curvature profile of the route can be determined, for example, from a digital map. From this information, it is possible to determine a realistically drivable speed profile and the associated drive and / or braking torque power requirement over a forecast horizon or driving performance horizon FLH using a longitudinal dynamics model (see Figure 3). From the resulting energy requirements, a fuel cell power Ps(t) required in the forecast horizon can then be determined in the energy management system ENM, in particular in a module 13 for determining the driving performance-oriented and SOC-based energy distribution horizon of the high-voltage battery as part of the energy management system ENM, and waste heat can be determined from the fuel cell efficiency map.If the waste heat from the auxiliary consumers, the battery and a possible continuous braking is taken into account, the total cooling requirements are calculated, which can be plotted over the forecast horizon.
[0061] Figure 6 shows a schematic progression of a driving performance horizon FLH with predictive control with trajectories for driving speed v (e.g. from speed prediction), road gradient FBS (e.g. from map) and ambient temperature Tu (e.g. from web service) over a distance s ahead. The variables that can be calculated from this are an estimated drive power ATL, an estimated fuel cell power BZL, a state of charge SOC of a battery, a waste heat QBZ of the fuel cell system, an available cooling capacity QKI , QK2 (e.g. due to airflow) and a required fan activation BLZ.
[0062] Similarly, with a web-based weather service, a trend for the expected ambient temperature Tu(t) as well as other weather data, such as rain, can be retrieved, for example from Cloud 8. Using a thermal model of the cooling system, this data can be used to calculate how the cooling system's usable cooling capacity and the corresponding energy consumption parameter KW will develop for the upcoming route - both in ECO mode and in Power mode. For this purpose, it is calculated whether, based on the expected mileage for the upcoming route s, the resulting expected fuel cell waste heat can be dissipated with the aid of all actuators, for example one or more pumps 6, one or more coolers 5, one or more coolers 4, and one or more valves 11.If this is not the case, a limit violation LV is detected and the expected fuel cell target power is corrected in the energy management ENM.
[0063] Using this information, the energy management system ENM can plan an optimal power trajectory Ps(t) for the fuel cell system, taking into account the driving distance s and external environmental influences. For example, if the planning system already knows that the fuel cell power BZL must be reduced on an uphill stretch due to thermal management (limit violations of the LV thermal system are on the horizon), it can start up the fuel cell earlier – and in situations where cooling is easier – and provide a corresponding energy buffer in a high-voltage battery.
[0064] The device and the method can be used in a fuel cell vehicle, in particular in a commercial vehicle, for example a heavy commercial vehicle. List of reference symbols
[0065] 1 Vehicle control 2 Interface 3 Fan control 4 Fan 5 Cooler 6 Pump 7 Prediction module 8 Cloud 9 Distribution of mass flows 10 Consideration of thermal management limitations 11 Valve 12 Module 13 Module AFW Current driving resistance ATL Drive power BLZ Required fan activation BZL Fuel cell power
[0066] ENM Energy management FBS Road gradient FLH Driving performance horizon KF map KFEW Map with empirical values KW Characteristic value KoW Correction value LV Limit violation total Total air mass flow m L Air mass flow -LFW Air mass flow from airstream m LL Air mass flow through fan rä L1 , ^12 Mass flow for fan m P Mass flow pump m wCooling water mass flow n Pump speed
[0067] Ps target power
[0068] Ps(t) expected course of the target power, power trajectory
[0069] QBZ waste heat from the fuel cell system
[0070] QECO heat output in ECO mode
[0071] QKI , K2 heat dissipated by cooler
[0072] QL waste heat for fans
[0073] (jpowER Heat output in power mode s Driving distance
[0074] SE simulation results
[0075] SOC state of charge
[0076] TKM Temperature of a cooling medium Air inlet temperature
[0077] Tu ambient temperature
[0078] Tu(t) Course of the expected ambient temperature
[0079] Tw Cooling water inlet temperature v Driving speed v(t) Course of the expected driving speed
[0080] WLW thermal conductivity
Claims
A method for thermal management of a fuel cell system of a vehicle, wherein a thermal output of an overall cooling system of the vehicle is estimated using a physical model taking into account a current driving situation of the vehicle and existing ambient conditions, characterized in that a thermal output (QECO) in an ECO mode, which can be dissipated without switching on one or more auxiliary consumers, including at least one fan (4), and a thermal output (QPOWER) of the overall cooling system in a power mode, which can be dissipated when switching on one or more auxiliary consumers, including at least one fan (4), are determined, wherein in an energy management system (ENM) on the basis of these thermal outputs (ECO, POWER), a target power (Ps) currently available from the fuel cell system is determined and a decision is made as to whether the fuel cell system is operated in ECO mode or in power mode,wherein, by means of a heuristic logic, it is determined how much energy the auxiliary consumers required for cooling currently require in order to determine a characteristic value (KW) that indicates how much electrical power must currently be used to dissipate a certain heat output, wherein, at a value of more than 1 kW of electrical power per kW of dissipated heat output, the power of the fuel cell system is not increased. Method according to claim 1, characterized in that, at a value of significantly less than 1 kW of electrical power per kW of dissipated heat output, in particular at a maximum of 0.2 kW of electrical power per kW of heat output, Energy management system (ENM) increases the requested target power (Ps) of the fuel cell. Method according to one of claims 1 or 2, characterized in that a driving speed (v) and / or a temperature (TKM) of a cooling medium is taken into account for the current driving situation. Method according to one of the preceding claims, characterized in that an ambient temperature (Tu) is taken into account as ambient conditions. Method according to one of the preceding claims, characterized in that the energy management system (ENM) calculates back the possible electrical power of the fuel cell based on a characteristic map which takes into account the currently existing aging of the fuel cell system and requests this from the fuel cell.Method according to one of the preceding claims, characterized in that an estimate for a mass flow (m) to be provided by one or more pumps (6) is obtained from a current waste heat (QBZ) of the fuel cell system. P ) of the cooling medium is estimated, which in the estimation by one or more coolers (5) can be discharged Heat «?KI , ( is taken into account in addition to the current driving situation and the existing ambient conditions. Method according to one of the preceding claims, characterized in that when determining additional waste heat (Q ) required for the at least one fan (4), a current waste heat (QBZ) of the fuel cell system and a heat «?KI , QKZ) that can be dissipated by one or more coolers (5) are taken into account. Method according to claim 7, characterized in that from the waste heat (Q ) required for the at least one fan (4), a mass flow (m L1 , m L2) is estimated, which is to be provided by the at least one fan (4) in order to obtain an energy-optimized Distribution (9) of mass flows (m L1 , m L2) on the fans (4) and a corresponding control (3) of the fans (4). Method according to one of the preceding claims, characterized in that a prediction is made for an upcoming route, wherein a profile (v(t)) of the expected driving speed of the vehicle and a profile of the expected ambient temperature (Tu(t)) are determined on the basis of a planned route using a web-based traffic service and / or a prediction module (7), wherein a thermal model of the cooling system is used to determine, based on this data, how the achievable cooling capacity of the cooling system and the corresponding characteristic value (KW) will develop in ECO mode and in Power mode for the upcoming route, and on this basis an optimal power trajectory (Ps(t)) for the fuel cell system is planned, taking into account the route and the external environmental influences.Device for thermal management of a fuel cell system of a vehicle, comprising an energy management system (ENM) of the fuel cell system and a vehicle control (1) which is / are configured to carry out the method according to one of the preceding claims.