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JP-2026514258-A - Methods for emptying liquid hydrogen tanks

JP2026514258AJP 2026514258 AJP2026514258 AJP 2026514258AJP-2026514258-A

Abstract

[Problem] To provide a technology for discharging residual hydrogen from a tank with high energy efficiency. [Solution] The present invention relates to a method for emptying a tank (13) for liquid hydrogen using a tank heater (15) in a vehicle (1) equipped with at least one hydrogen-driven drive unit (2). The present invention is characterized in that the drive unit (2) does not operate while the tank (13) for liquid hydrogen is being emptied, and a coolant is circulated to a cooling circuit (3) of the drive unit (2) or a cooling circuit (3) that is indirectly heat-conductively connected to the cooling system of the drive unit (2), and the heat in the coolant and the heat that the coolant receives from the ambient air are supplied directly or indirectly to the tank heater (15). [Selection Diagram] Figure 1

Inventors

  • クネーベル，ヨナス
  • クレムザー，ジェニー
  • シュタンゼル，ニコラス

Assignees

  • ダイムラー トラック アクチェンゲゼルシャフト

Dates

Publication Date
20260507
Application Date
20240313
Priority Date
20230505

Claims (6)

  1. A method for emptying a tank for liquid hydrogen (13) using a tank heater (15) in a vehicle (1) equipped with at least one hydrogen-powered drive unit (2), A method characterized in that, while the liquid hydrogen tank (13) is empty, the drive unit (2) does not operate, and the coolant is circulated through the cooling circuit (3) of the drive unit (2) or a cooling circuit (3) indirectly connected by heat conduction to the cooling system of the drive unit (2), thereby supplying the heat in the coolant and the heat received by the coolant from the ambient air to the tank heater (15) directly or indirectly.
  2. The method according to claim 1, characterized in that the heat from the coolant in the cooling circuit (3) is transferred to the coolant in the coolant circuit (12) of the tank (13) via the heat exchanger (11), and then the residual liquid hydrogen is heated and vaporized by the tank heater (15) using the heat.
  3. The method according to claim 2, characterized in that a further heat source (20) in contact with the cooling circuit (3) and/or the refrigerant circuit (12) of the tank (13) is used to heat the refrigerant in the refrigerant circuit (12) of the tank (13).
  4. The method according to claim 2 or 3, characterized in that at least one of the circuits (3, 12) is provided with an electric heating resistor (19) that operates when additional heat is required.
  5. The method according to any one of claims 1 to 4, characterized in that at least one fuel cell (2) is used as the drive unit (2).
  6. The method according to any one of claims 1 to 4, characterized in that at least one hydrogen combustion machine is used as the drive unit (2).

Description

This invention relates to a method for emptying a liquid hydrogen tank using a tank heater in a vehicle equipped with at least one hydrogen-driven drive unit. A hydrogen-driven drive unit in the sense of this invention may be, for example, a fuel cell in a fuel cell system or a machine that burns hydrogen. The hydrogen-driven drive unit may also be, for example, a hydrogen-driven combustion engine or a gas turbine. To extract liquid hydrogen from a vehicle equipped with such a tank during operation, the general approach is to heat the liquid phase of hydrogen to vaporize it. The resulting pressurized gas can then be extracted from the tank. Various heat sources can be used for this purpose. Patent Document 1 describes a system that extracts heat for liquefying hydrogen from either the environment or the cooling circuit of a fuel cell, depending on the season. Its configuration is correspondingly complex and suitable only for fixed installations. A similar concept is described in Patent Document 2. In addition to the hydrogen extraction described in these two patent documents, emptying liquid hydrogen tanks for maintenance purposes plays an important role, particularly in the field of vehicle technology, for supplying hydrogen to fuel cell systems or, in principle, other hydrogen-consuming devices. In vehicles, a separate tank circuit with an electric resistance heater or refrigerant (Kuhlmedium) is generally provided to operate the tank heater. For this purpose, a liquid refrigerant having a temperature higher than the boiling point of hydrogen flows through the tank circuit. When it is necessary to completely empty a liquid hydrogen tank for maintenance purposes, energy is generally supplied to this tank circuit to heat the refrigerant and vaporize the hydrogen in the tank so that it can be extracted. Since all other systems of the vehicle are no longer operating in such a situation, this energy is generally supplied via an electric heater, for example, an electric heating resistor. In practice, heating resistors provided in vehicles are mainly used in case the battery is already fully charged when regenerative braking is activated during driving and the resulting power cannot be received. In this case, the surplus power is consumed in the heating resistor. When completely emptying a liquid hydrogen tank for maintenance purposes, this heating resistor can be used to supply heat. However, this method has a significant drawback: it requires a relatively large amount of power, which is typically supplied by a battery. Therefore, after the tank is completely empty, the battery often has a very low or unstable charge level, or requires an external power source for electrical energy. U.S. Patent Application Publication No. 2020/0298651, Specification A1Chinese Patent Application Publication No. 115224306 Specification A1 This is a schematic diagram of a vehicle equipped with a fuel cell system and a liquid hydrogen tank. In Figure 1, vehicle 1 is schematically represented by a dashed line. This vehicle 1 may be, for example, a commercial vehicle electrically driven via a fuel cell system. In the embodiment illustrated herein, this fuel cell system shows two parallel fuel cells 2, so-called fuel cell stacks or fuel cell arrays. These form a drive unit 2 in the sense of the present invention. However, the drive unit may be replaced with an internal combustion engine, a gas turbine, etc., in which case vehicle 1 would be driven mechanically or in a serial hybrid manner via these. In that case, the remaining configuration will be similar to the examples described below in relation to fuel cell vehicle 1. In this case, the fuel cell 2 is located together with the fuel cell cooling circuit 3 and can be cooled in parallel by the volumetric flow rate of the coolant supplied (transported) via the coolant supply device (coolant transport device) 4 during normal operation. Furthermore, a fuel cell bypass 5 is provided. This makes it possible for the coolant to flow through the fuel cells 2 individually or simultaneously, or not to flow through at all, and for this purpose, a bypass valve 6 is provided to control the flow of coolant according to the desired operating state. The waste heat of the fuel cell 2 is dissipated through the cooling heat exchanger 7 during normal operation. The cooling heat exchanger 7, often also called a radiator, may consist of one or more elements, and one or more elements are generally positioned in the vehicle 1 so that sufficient cooling air flows through it while the vehicle 1 is running. If this cooling air is insufficient, an additional or enhanced airflow can be generated through the cooling heat exchanger 7 via the fan propeller 8 shown herein. This cooling heat exchanger 7 also includes a radiator bypass 9 with a bypass valve 10, which, for example, in a cold start scenario of a fuel cell system, avoids cooling the slowly warming refrigerant and heats the fuel cell 2 as quickly as possi