Motor Vehicle with a Cryogenic Pressure Vessel and Method for Refuelling a Cryogenic Pressure Vessel of a Motor Vehicle

Abstract

A method is provided for refueling a cryogenic pressure vessel of a motor vehicle. The motor vehicle has: a) a cryogenic pressure vessel having an internal vessel which stores a fluid, an external vessel and heat insulation which is arranged between the internal vessel and the external vessel, at least in certain areas; and b) a controller, wherein the controller is designed to interrupt refueling of the motor vehicle if, in the case of damaged thermal insulation, a lower fluid density limiting value for the fluid in the internal vessel is exceeded. The lower fluid density limiting value is lower than an upper fluid density limiting value for the fluid in the internal vessel in the case of refueling of the internal vessel with intact thermal insulation.

Claims

1. A motor vehicle, comprising: a cryogenic pressure vessel with an inner vessel storing a fluid, an outer vessel and thermal insulation which is arranged at least in regions between the inner vessel and the outer vessel; and a controller, wherein the controller is configured to interrupt refueling of the motor vehicle if, in an event of damaged thermal insulation, a lower fluid density limit value for the fluid in the inner vessel is exceeded, wherein the lower fluid density limit value is lower than an upper fluid density limit value for the fluid in the inner vessel in the case of refueling of the inner vessel with intact thermal insulation.

2. The motor vehicle as claimed in claim 1, further comprising: a refueling valve configured to interrupt the inflow of fluid into the inner vessel.

3. The motor vehicle as claimed in claim 2, further comprising: a communication interface that transmits a refueling termination signal and/or a refueling limiting signal to a refueling device.

4. The motor vehicle as claimed in claim 1, further comprising: a communication interface that transmits a refueling termination signal and/or a refueling limiting signal to a refueling device.

5. A method for refueling a cryogenic pressure vessel of a motor vehicle, the method comprising the steps of: determining damage to thermal insulation which is arranged at least in regions between an inner vessel and an outer vessel of the cryogenic pressure vessel; and interrupting refueling of the motor vehicle if, in an event of damaged thermal insulation, a lower fluid density limit value for the fluid in the inner vessel is exceeded, wherein the lower fluid density limit value is lower than an upper fluid density limit value for the fluid in the inner vessel in the case of refueling of the inner vessel with intact thermal insulation.

6. The method as claimed in claim 5, wherein the lower fluid density limit value is selected such that the inner vessel in an uninsulated state can store a fluid without the maximally permissible inner vessel pressure being exceeded.

7. The method as claimed in claim 5, further comprising the step of: interrupting, via a refueling valve, inflow of fluid into the inner vessel in the event of damaged thermal insulation when the lower fluid density limit value is reached.

8. The method as claimed in claim 6, further comprising the step of: interrupting, via a refueling valve, inflow of fluid into the inner vessel in the event of damaged thermal insulation when the lower fluid density limit value is reached.

9. The method as claimed in claim 5, further comprising the step of: transmitting, via a communication interface, a refueling termination signal and/or a refueling limiting signal to a refueling device.

10. The method as claimed in claim 6, further comprising the step of: transmitting, via a communication interface, a refueling termination signal and/or a refueling limiting signal to a refueling device.

11. The method as claimed in claim 7, further comprising the step of: transmitting, via a communication interface, a refueling termination signal and/or a refueling limiting signal to a refueling device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic diagram of the basic construction of a cryogenic pressure vessel 100.

[0026] FIG. 2 is a graph of the fluid density D in the inner vessel 110 over the temperature for various inner vessel pressures.

DETAILED DESCRIPTION OF THE DRAWINGS

[0027] The cryogenic pressure vessel 100 illustrated in FIG. 1 is mounted at its two ends on the vehicle body 50. The outer vessel 120 delimits the cryogenic pressure vessel 100 in relation to the environment. Possible additional components of the cryogenic pressure vessel (for example heat exchangers) have been omitted in this simplified illustration. The inner vessel 110 is arranged in the outer vessel 120 at a distance from the outer vessel 120. The inner vessel 110 illustrated here comprises domes at its two ends. A substantially evacuated or super-insulated space V is located between the inner vessel 110 and the outer vessel 120. The inner vessel 110 is connected via a suspension system at its domes to the outer vessel 120. At one end of the inner vessel 110, a supply line 300 is connected to the inner vessel 110. The inner vessel 110 is refueled through the supply line 300. The sensor 130 can measure the pressure and/or the temperature of the evacuated space V.

[0028] A connection 150 is provided at the other end of the supply line 300. The connection or filler neck 150 is designed to be coupled to a corresponding connection 200 of a refueling device.

[0029] Furthermore, a communication interface 160 is arranged here in the connection 150. The communication interface is able to be connected to a corresponding communication interface 210 in the connection 200. A refueling termination signal and/or a refueling limiting signal can be transmitted to the refueling device 200 via the communication interface 160/210. In addition to this configuration, a radio-based communication (interface) is likewise contemplated (for example WiFi, WLAN, NFC, etc.) which does not have to be accommodated in the connection 200.

[0030] The refueling valve 180 is designed here to interrupt the fluid flow, here a hydrogen flow. The refueling valve 180 can be arranged anywhere in the supply line 300.

[0031] The controller 140 is designed to control the refueling and the operation of the cryogenic pressure vessel.

[0032] FIG. 2 shows the fluid density D in the inner vessel 110 for various inner vessel pressures over the temperature. If a cryogenic pressure vessel 100 with intact thermal insulation V is cryogenically refueled, hydrogen is filled into the inner vessel 110 up to an upper fluid density limit value D.sub.OB. For example, an inner vessel 110 which is designed for a maximum vessel inner pressure of approx. 250 to approx. 350 bar (also called maximally permissible inner vessel pressure Pmax or design pressure) can be refueled cryogenically at a temperature TKB of approx. 40 K up to an upper fluid density limit value D.sub.OB of approx. 80 gram/liter (point P′KB in FIG. 2). If the fluid in the inner vessel 110 with intact thermal insulation V is heated, comparatively small quantities of hydrogen should be converted via the BMS. The BMS is designed for these quantities of hydrogen. The hydrogen is therefore converted by the BMS without a hazardous mixture arising.

[0033] If the cryogenic pressure vessel 100 now has damaged thermal insulation V, the pressure vessel 100 has to comparatively rapidly dissipate comparatively large quantities of hydrogen so that the inner vessel 110 is not destroyed by the expanding hydrogen. In FIG. 2, such a great amount of hydrogen therefore then always has to be released starting from the point P′KB that the inner vessel 110 does not have a pressure above the design pressure of approx. 250 to 350 bar at any temperature T. In the heated state, for example at environmental temperature, the inner vessel 110 of the pressure vessel 100 can store, for example, a density of approx. 21 gram/liter in the inner vessel 110 (point PUV in FIG. 2 for a tank with a design pressure of approx. 350 bar). Consequently, the quantity of hydrogen which arises from the product of approx. 60 gram/liter and the inner vessel volume should therefore be released. Under some circumstances, this quantity of hydrogen may not be converted by the BMS in the comparatively short time, and therefore hydrogen has to be released directly into the environment via the safety valve or the bursting disk. A mixture with a hazardous potential may then arise under some circumstances in the environment of the motor vehicle.

[0034] If damage to the thermal insulation V is then determined, refueling should be ceased up to the upper fluid density limit value DOB. However, it is not necessary to completely dispense with refueling. On the contrary, it is possible to cryogenically refuel the inner vessel 110 in such a manner that a critical inner vessel pressure does not arise even in the heated state of the cryogenically filled fluid. For this purpose, at the cryogenic refueling temperature, the fluid density D should be limited to a lower fluid density limit value D.sub.UB for the fluid in the inner vessel 110, wherein the lower fluid density limit value D.sub.UB is selected in such a manner that the inner vessel 110 in the uninsulated state can store the fluid without the maximally permissible inner vessel pressure Pmax being exceeded. For an inner vessel 110 with a maximally permissible inner vessel pressure Pmax of approx. 350 bar, a lower fluid density limit value DUB of approx. 21 gram/liter (point PKB in FIG. 2) arises for hydrogen as the fuel. If refueling is permitted for hot use, the vehicle can continue to be used without danger—albeit with a reduced range—without hydrogen being inefficiently consumed in the process. If fiber-reinforced inner vessels are used, for example with braided and/or wound fiber layers around the inner vessel, ranges of more than 200 km can be achieved. Considerable distances can therefore be covered even with damaged thermal insulation. The vehicle driver himself can still bring the vehicle to the service garage and the vehicle does not break down out on the road.

[0035] The preceding description of the present invention serves only for illustrative purposes and not for the purpose of limiting the invention. Within the scope of the invention, various amendments and modifications are possible without departing from the scope of the invention and the equivalents thereof. Even though the description is primarily focused on hydrogen as fuel, other fuels, such as compressed natural gas, are likewise included therewith. The numerical values mentioned are merely preferred values. It is likewise possible, for example, to provide inner vessels 110 with higher or low design pressures.

[0036] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.