Thermal management system for a cooling system of an fuel cell

Abstract

The invention relates to a thermal management system (1) for a cooling system (9) of at least one fuel cell of a vehicle, wherein the cooling system (9) has a plurality of cooling components (4.1, 4.2, 5.1, 5.2), including at least one cooling pump (4.1, 4.2) and at least one fan (5.1, 5.2) which can be open-loop controlled and / or closed-loop controlled by a heat output controller (6) of the thermal management system (1) depending on a current waste heat output (I) of the fuel cell, a current travel speed (v) of the vehicle and a current ambient temperature (TU), wherein the heat output controller (6) is configured to operate with a comparatively slow operating stroke, wherein the thermal management system (1) also has an online optimizer (7) which is configured to estimate a currently dischargeable heat output (II) of the cooling system (9) for different combinations of operating points of the cooling components (4.1, 4.2, 5.1, 5.2) with a comparatively fast operating stroke on the basis of a physical model taking into account at least the current travel speed (v) and the current external temperature (Tu), and to choose that combination with which the dischargeable heat output (II) can be achieved with a low or the lowest possible electrical power (PP1, PP2, PL1, PL2) to be applied for the cooling components (4.1, 4.2, 5.1, 5.2).

Description

[0001] Daimler Truck AG Özvatan December 1, 2023 Thermal management system for a cooling system of a fuel cell The invention relates to a thermal management system for a cooling system of a fuel cell according to the preamble of claim 1 and to a vehicle according to the preamble of claim 9. ^ 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, on the other hand, first be warmed up. Over the course of its ^^ service life, the fuel cell system ages and thus loses efficiency, so that^ ever larger amounts of waste heat have to be cooled away. A ^^ fuel cell system therefore requires a thermal management system in order to always be able to operate in the ^ correct temperature range. ^ ^^ Thermal management must be able to cope with changing conditions and different^ heat quantities.Depending on the ambient conditions ^^ (outside temperature) and driving situation (driving speed), it can dissipate different amounts of heat into the environment. At cold outside temperatures and higher driving speeds, these heat quantities are greater because the radiators are flowed through with a lot of cold air, which ensures good heat transfer to the ambient air. At warm outside temperatures and / or low driving speeds, the amounts of heat that can be dissipated are lower, so the cooling capacity must be increased by using powerful cooling pumps and several independent fans. The order of magnitude of the power required for this is up to 70kW of electrical power with full control of all components. A conventional control system regulates pumps and fans so that the control target is achieved - but this means energy is wasted in the ancillary units.US 10,369,899 B2 describes systems and methods for determining battery heating conditions and preheating lead times of at least one minute or more based on input parameters and sets of input parameters in order to proactively and dynamically heat a secondary battery so that the battery achieves a specific power output and a specific performance level when used in an electric or hybrid vehicle application. The invention is based on the object of specifying a novel thermal management system for a cooling system of a fuel cell and a novel vehicle. This object is achieved according to the invention by a thermal management system for a cooling system of a fuel cell having the features of claim 1 and a vehicle having the features of claim 9. Advantageous embodiments of the invention are the subject of the dependent claims.According to the invention, a thermal management system for a cooling system of at least one fuel cell of a vehicle is proposed, wherein the cooling system has a plurality of cooling components, including at least one cooling pump and at least one fan, which can be controlled and / or regulated by a heat output controller of the thermal management system depending on a current waste heat output of the fuel cell, a current driving speed of the vehicle and a current ambient temperature.According to the invention, the heat output controller is configured to operate at a comparatively slow operating cycle, wherein the thermal management system further comprises an online optimizer configured to estimate, with a comparatively fast operating cycle, a currently dissipated heat output of the cooling system for different combinations of operating points of the cooling components based on a physical model, taking into account at least the current driving speed and the current outside temperature, and to select the combination in which the dissipated heat output can be achieved with a low or the lowest possible electrical power to be applied to the cooling components. In one embodiment, the fast operating cycle is 10 to 1000 times, for example approximately 100 times faster, in particular exactly 100 times faster, than the slow operating cycle.The optimizer calculates quickly, so that it finds an optimization result in, for example, a maximum of 100 steps of 10 ms each. In this case, a result is always found after a maximum of one second, and this is then used to control the components. In one embodiment, the slow operating cycle is between 0.5 s and 5 s, for example, approximately one second. In one embodiment, the fast operating cycle is between 5 and 50 milliseconds, for example, approximately ten milliseconds. In one embodiment, the heat output controller is configured to use the currently occurring waste heat output as a pilot control value and to increase or decrease the pilot control value in order to maintain a required setpoint for a coolant of the fuel cell. In one embodiment, the heat output controller is configured as a PI controller.In one embodiment, the online optimizer is configured to increase the operating points gradually from a lowest operating point and, at each step, to calculate individually for each cooling component how much the dissipated heat output increases as a result of the changed operating point and how much the energy consumption of the individual cooling component increases. For each cooling component, it determines a characteristic value that indicates how much energy the achievable heat output dissipation costs. Based on this characteristic value, a decision unit then decides which cooling component should be increased in the next step. Starting from the operating point thus found, the next calculation is carried out according to the method just described, and in this case, the cooling component that provides the most efficient form of cooling under the current conditions is again sought.This process is repeated until the required heat output is reached or exceeded. The optimizer therefore works in a step-by-step manner. In each individual step, the currently best component is selected and incremented by one step. If the optimizer selects the optimal solution in each calculation step, it ultimately arrives at the optimal result (“global optimum”). This means that not all theoretically possible combinations are tried out, but rather the optimum is found in, for example, a maximum of 100 steps. In one embodiment, the online optimizer is configured to increase the efficiency of the system when the distance to the required heat output is greater, for example when there is a difference between the required heat output ^̇. ^and with the current combination of cooling components dissipated heat output of more than 25 kW, increase the step size for changing the operating points of the individual cooling components so that the heat output is estimated in larger steps, and when reaching a smaller distance to the required heat output, for example at 25 kW difference or less between required heat output ^̇ ^and the heat output that can be dissipated with the current combination of cooling components, a smaller increment should be selected. For example, if a waste heat output of 300 kW is required, the optimization would not be performed in 1 kW increments, as 100 calculation steps are not sufficient to achieve the target result. Furthermore, such fine calculation steps are not necessary in this case. Therefore, larger increments are selected in such a case (e.g., 10 kW). Only when the required target cooling output is approached (e.g., less than 25 kW) is a smaller increment selected.According to one aspect of the present invention, a vehicle, in particular an electrically powered vehicle, is proposed, comprising at least one fuel cell, a cooling system for the fuel cell with a plurality of cooling components, including at least one cooling pump and at least one fan, wherein the vehicle has a thermal management system as described above. In one embodiment, the vehicle is designed as a commercial vehicle, in particular a heavy-duty commercial vehicle. The required cooling capacity is to be provided with minimal energy consumption for the auxiliary units or cooling components. Since the influencing conditions constantly change during travel, a solution is proposed that constantly searches for such an optimal distribution, a so-called "online optimizer." The present invention provides a control system that meets the control objective with the minimum possible energy requirement.This allows the optimal (most energy-efficient) distribution of the cooling components to be found during operation. The invention solves the control problem by dividing the control into a slow operating cycle (heat output controller) and a fast operating cycle (online optimizer). By calculating both the currently required cooling capacity and the currently dissipated heat output, and by performing a step-by-step precalculation of the cooling components, the energy optimum is found for each current situation. The energy-optimal control for the current situation is always found, taking into account the currently prevailing conditions such as fuel cell power, fuel cell waste heat, outside temperature, driving speed, and aging of the cooling system and the fuel cell.This allows a significant amount of energy to be saved for driving the cooling components, increasing the vehicle's range because more electrical energy remains for driving. The use of electrical energy in a fuel cell vehicle can be made efficient using the solution according to the invention. Operating conditions in which energy is consumed unnecessarily without generating any gain in driving performance or the on-board network are thus avoided. The use of the auxiliary units required for cooling is regulated to ensure energy consumption is as optimal as possible. Thanks to the invention, the heat output controller always ensures the correct waste heat output so that the fuel cell system is in its optimal "comfort zone." The energy consumption required for this is optimally managed, as the most energy-efficient solution is always found under the current external conditions.The invention also ensures that maximum efficiency in thermal management is maintained under changing operating conditions such as ambient conditions, aging of the fuel cell and the cooling system; it is always used optimally, so to speak. The cooling control can be adjusted more easily because the system always independently searches for and finds an optimal solution. Exemplary embodiments of the invention are explained in more detail below with reference to drawings. In the drawings: Fig. 1 shows a schematic view of a thermal management system of a fuel cell vehicle, Fig. 2 shows a schematic detailed view of the thermal management system, Fig. 3 shows a schematic view of a simplified model for estimating the cooling capacity dissipated by a cooler, and Fig. 4 shows a schematic view of a method for estimating air mass flows. Corresponding parts are provided with the same reference numerals in all figures.Figure 1 is a schematic view of a thermal management system 1 of a fuel cell vehicle, for example, a commercial vehicle. The thermal management system 1 can be implemented in a vehicle control system. The thermal management system 1 is connected on the input side to a fuel cell controller 2 of a fuel cell and a vehicle controller 3, and on the output side to at least one cooling pump 4.1, 4.2, for example, two cooling pumps 4.1, 4.2, and at least one fan 5.1, 5.2, for example, two fans 5.1, 5.2, for controlling them. The fuel cell controller 2 provides the thermal management system 1 with a current waste heat output ^̇ of the fuel cell as input data. The vehicle controller 3 provides the thermal management system 1 with a current driving speed v and a current ambient temperature T. Uas input data. Figure 2 is a schematic detailed view of the thermal management system 1. The fuel cell controller 2 transmits the currently occurring waste heat output ^̇ to the thermal management system 1, which uses this value as a pilot control value 8 for a heat output controller 6, for example a PI controller. The heat output controller 6 operates with a comparatively slow operating cycle of, for example, one second and corrects this pilot control value 8 and increases or decreases it in such a way that an actual temperature T i of the fuel cell coolant a required setpoint T S Thus, every second a heat output setpoint ^ ^ ̇generated, which currently has to be dissipated by the cooling system 9 as a controlled system. The basis for these calculations is a simplified physical cooling capacity model which describes the waste heat currently dissipated by the cooling system 9. This contains a characteristic map for each cooler or heat exchanger which outputs a thermal conductivity (e.g. in kW / K) based on the existing coolant and air mass flows. Together with the currently measured temperatures of the cooling water and the ambient air at the cooler inlet and taking into account a correction value KoW or a correction function, the current cooling capacity can be estimated for each cooler. Figure 3 shows a schematic view of a simplified model for estimating the cooling capacity dissipated by a cooler.To determine the correction value KoW, a difference between a cooling water inlet temperature TW and an air inlet temperature TL of the cooler is formed and multiplied by the thermal conductivity WLW determined by the characteristic map KF, which is calculated based on a cooling water mass flow ^̇. ^ and an air mass flow ^̇ ^ of the cooler. To estimate cooling water mass flows ^̇ ^ From the pump speed n the following formulas can be used: ∗ 2 ∗ ^ ∗ ^ ∗ ^ ^ = 60000 P Drive power (kW) p Operating pressure pump outlet (bar) Q Volume flow (dm 3 / min) ηges Total efficiency (-) M Torque (Nm) n Pump speed (1 / min) The cooling water mass flow is determined by the density of the cooling water ^̇ ^ for example, in a known ratio to the volume flow. The mass flow ^̇ ^of a cooling pump 4.1, 4.2 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 ^̇ ^ , which was previously determined by testing the system in question. The current mass flow ^̇ ^ to a maximum mass flow as the current pump speed n to a maximum pump speed. The sum of the heat outputs dissipated by the individual coolers thus determined corresponds to the current cooling capacity of the cooling system 9. The air mass flows can be estimated using the current driving speed v, ambient temperature TU and a given fan speed, as shown in more detail in Figure 4. Figure 4 is a schematic view of a method for estimating air mass flows ^̇ ^ . The air mass flow ^̇ ^through the coolers can be calculated from a combination of simulation results SE, in particular for determining an air mass flow ^̇ ^^ by a fan 5.1, 5.2, and characteristic maps KFEW with empirical values, in particular for determining an air mass flow ^̇ ^^^ from the airstream, as well as current environmental conditions such as driving speed v and ambient temperature T U A total air mass flow ^̇ ^^^ can then be calculated as the sum of the air mass flow ^̇ ^^ by the fan 5.1, 5.2 and the air mass flow ^̇ ^^^ formed from the airstream. The thermal management system 1 estimates the currently dissipated heat output ^̇ in an online optimizer 7 with a comparatively fast working cycle of, for example, ten milliseconds, based on a physical model with the current driving situation and the existing ambient conditions (driving speed v, outside temperature TU, etc.). ^of the entire cooling system. For this purpose, the operating points for the cooling components 4.1, 4.2, 5.1, 5.2, i.e., the cooling pumps 4.1, 4.2 and the fans 5.1, 5.2, are gradually increased from a lowest operating point. At each step, the individual calculation is made for each cooling component 4.1, 4.2, 5.1, 5.2 to determine how much the dissipated heat output ^̇ ^ increased. In addition, the energy consumption of each cooling component 4.1, 4.2, 5.1, 5.2 is calculated. Thus, for each cooling component 4.1, 4.2, 5.1, 5.2, a characteristic value can be determined that indicates how much energy the achievable heat dissipation ^̇ ^^ , ^̇ ^^ , ^̇ ^^ , ^̇ ^^ costs. The characteristic value can be expressed, for example, in kW of dissipated thermal power ^̇ ^^ , ^̇ ^^ , ^̇ ^^ , ^̇ ^^per kW of electrical power to be generated PP1, PP2, PL1, PL2. Based on this characteristic value, a decision unit 10 can then decide which cooling component 4.1, 4.2, 5.1, 5.2 should be increased in this step, i.e., which is the most energy-efficient solution. This is continued until the required heat output ^̇ ^ is reached, i.e. the optimization is terminated as soon as the required heat output ^̇ ^is reached. This determines the energy-optimal distribution of the control of the cooling components 4.1, 4.2, 5.1, 5.2. The control of the individual cooling components 4.1, 4.2, 5.1, 5.2 then takes place again in the slow working cycle, i.e. the control found is passed on to the cooling components 4.1, 4.2, 5.1, 5.2 for one second, for example. In the meantime, the fast working cycle has started again and determines the control for the next slow working cycle based on the current conditions that are now valid. To ensure that the fast working cycle also reaches a solution in, for example, a maximum of 100 calculation steps, with a larger distance to the required heat output ^̇ ^ the step size for changing the operating points of the individual cooling components 4.1, 4.2, 5.1, 5.2 is increased so that the heat output ^̇ ^is estimated in larger steps. As soon as a smaller distance to the required heat output ^̇ ^ is reached, smaller step sizes are chosen. This optimizes the calculation time. In addition to the physical calculation models for estimating the current heat output ^̇ ^of the cooling system 9, the calculation can be corrected in certain situations using a learning process. Such situations can be, for example, constant driving situations in which the operating state of the vehicle and / or the fuel cell changes only insignificantly. Here, the controller output of the PI controller can be used to calculate a correction value for precisely this driving situation. If several such correction values ​​have been determined, these can be stored in the control unit memory in the form of, for example, load- or temperature-dependent characteristic maps and then used for correction for future journeys. Aging and tolerances of the cooling components 4.1, 4.2, 5.1, 5.2 can be compensated for in this way.

[0002] Daimler Truck AG Özvatan 01.12.2023 List of reference symbols 1 Thermal management system 2 Fuel cell control 3 Vehicle control 4.1, 4.2 Cooling component, cooling pump ^ 5.1, 5.2 Cooling component, fan ^ 6 Heat output controller ^^ 7 Online optimizer ^^ 8 Pre-control value ^ 9 Cooling system ^^ 10 Decision unit ^^ KF characteristic map ^^ KFEW characteristic map ^ KoW correction value ^^ ^̇ ^ Air mass flow ^̇ ^^ Air mass flow ^̇ ^^^ Air mass flow ^̇ ^^^ Total air mass flow ^̇ ^ Cooling water mass flow n Pump speed PL1, PL2, PP1, PP2 Electrical power ^̇ Current waste heat output ^̇ ^ dissipable heat output ^̇ ^^ , ^̇ ^^ , ^̇ ^^ , ^̇ ^^ dissipated thermal power or heat output of the cooling component ^ ^ ̇Heat output setpoint SE Simulation result Ti Actual temperature TL Air inlet temperature TS Setpoint TU Current ambient temperature TW Cooling water inlet temperature v Current driving speed WLW Thermal conductivity

Claims

Daimler Truck AG Özvatan 01.12.2023 Patent claims 1. Thermal management system (1) for a cooling system (9) of at least one fuel cell of a vehicle, wherein the cooling system (9) has a plurality of cooling components (4.1, 4.2, 5.1, 5.2), including at least one cooling pump (4.1, 4.2) and at least one fan (5.1, 5.2) which can be controlled and / or regulated by a heat output controller (6) of the thermal management system (1) as a function of a current waste heat output (^̇) of the fuel cell, a current driving speed (v) of the vehicle and a current ambient temperature (TU), characterized in that the heat output controller (6) is configured to operate with a comparatively slow working cycle, wherein the thermal management system (1) further comprises an online optimizer (7) which is configured to operate with a comparatively fast working cycle on the basis of a physical model, taking into account at least the current driving speed (v) and the current outside temperature (T. U ) a currently dissipated heat output (^̇ ^) of the cooling system (9) for different combinations of operating points of the cooling components (4.1, 4.2, 5.1, 5.2), and to select the combination for which the dissipated heat output (^̇ ^ ) can be achieved with a low or the lowest possible electrical power (PP1, PP2, PL1, PL2) applied to the cooling components (4.1, 4.2, 5.1, 5.2).

2. Thermal management system (1) according to claim 1, characterized in that the fast operating cycle is 10 to 1000 times faster than the slow operating cycle.

3. Thermal management system (1) according to claim 1 or 2, characterized in that the slow working cycle is 0.5 s to 5 s per second.

4. Thermal management system (1) according to one of the preceding claims, characterized in that the fast working cycle is 5 to 50 milliseconds.

5. Thermal management system (1) according to one of the preceding claims, characterized in that the heat output controller (6) is configured to use the currently occurring waste heat output (^̇) as ​​a pilot control value (8) and to increase or decrease the pilot control value (8) in order to achieve a required setpoint (T S) of a coolant of the fuel cell.

6. Thermal management system (1) according to one of the preceding claims, characterized in that the heat output controller (6) is configured as a PI controller.

7. Thermal management system (1) according to one of the preceding claims, characterized in that the online optimizer (7) is configured to increase the operating points step by step from a lowest operating point and, at each step, to calculate individually for each cooling component (4.1, 4.2, 5.1, 5.2) how much the dissipated heat output (^̇ ^ ) increases, and how much the energy consumption of the individual cooling components (4.1, 4.2, 5.1, 5.2) increases, and to determine a characteristic value for each cooling component (4.1, 4.2, 5.1, 5.2) that states how much energy the achievable dissipation of heat output (^̇ ^^ , ^̇ ^^ , ^̇ ^^ , ^̇ ^^) costs, in order to then decide on the basis of this characteristic value in a decision unit (10) which cooling component (4.1, 4.2, 5.1, 5.2) is to be increased in the next step, until the required heat output (^̇ ^ ) is reached.

8. Thermal management system (1) according to claim 7, characterized in that the online optimizer (7) is configured to, at a greater distance from the required heat output (^̇ ^ ) the step size for changing the operating points of the individual cooling components (4.1, 4.2, 5.1, 5.2) so that the heat output (^̇ ^ ) is estimated in larger steps, and when a smaller distance to the required heat output (^̇ ^) to select a smaller step size again.

9. A vehicle comprising at least one fuel cell, a cooling system (9) for the fuel cell with a plurality of cooling components (4.1, 4.2, 5.1, 5.2), including at least one cooling pump (4.1, 4.2) and at least one fan (5.1, 5.2), characterized in that the vehicle has a thermal management system (1) according to one of the preceding claims.

10. A vehicle according to claim 9, characterized in that the vehicle is designed as a commercial vehicle.

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