US-20260128331-A1 - FUEL CELL COOLANT OVER-PRESSURIZATION SYSTEM

Abstract

A system includes a fuel cell stack. A liquid coolant loop is coupled to provide coolant to the fuel cell stack. An expansion tank is coupled to the coolant loop and has an expansion tank inlet to couple to a fuel cell stack cathode inlet. An inlet check valve has a relative cracking pressure dp in and is coupled between the fuel cell stack cathode inlet and the expansion tank inlet to over-pressurize the coolant in the coolant loop.

Inventors

• Pavel Trnka
• Filip Brenner
• Jan Macka
• Ondrej Kotaba
• Jaroslav Tesar
• Martin Zlomek

Assignees

• HONEYWELL INTERNATIONAL INC.

Dates

Publication Date

20260507

Application Date

20241107

Claims (20)

1. 1 . A system comprising: a fuel cell stack; a liquid coolant loop coupled to provide coolant to the fuel cell stack; an expansion tank coupled to the coolant loop; an expansion tank inlet to couple to a fuel cell stack cathode inlet; an inlet check valve with a relative cracking pressure dp in coupled between the fuel cell stack cathode inlet and the expansion tank inlet.
2. 2 . The system of claim 1 wherein the expansion tank comprises: a top portion including the expansion tank inlet: a bottom portion coupled to the coolant loop; and a flexible membrane dividing the top portion and the bottom portion.
3. 3 . The system of claim 2 and further comprising: an air supply system coupled to the fuel cell stack inlet; and a hydrogen supply system coupled to a fuel cell stack anode.
4. 4 . The system of claim 1 wherein the coolant loop comprises: a supply channel coupled to the fuel cell stack; a return channel coupled to the fuel cell stack; and a radiator coupled between the supply channel and the return channel.
5. 5 . The system of claim 4 wherein the coolant loop further comprises a pump coupled to pump coolant through the supply and return channels.
6. 6 . The system of claim 5 wherein the coolant loop further comprises a temperature control valve coupled between the return channel and the supply channel to control a temperature of the coolant to a setpoint by controlling coolant flow to the radiator.
7. 7 . The system of claim 1 and further comprising: a gas exhaust line to ambient; a differential pressure regulating valve with a differential pressure setpoint dp coupled between the expansion tank and the exhaust line; and an outlet check valve having a absolute cracking pressure p out coupled between the differential pressure regulating valve and the exhaust line.
8. 8 . The system of claim 7 wherein the dp, p out , and dp in are selected to prevent fuel cell stack damage and coolant boiling.
9. 9 . A method comprising: providing liquid coolant to a fuel cell stack via a coolant loop; providing air to a cathode input of the fuel cell stack; and maintaining a pressure of the liquid coolant in the fuel cell stack greater than a pressure of gas in the cathode wherein a difference in pressure is within a selected range of pressures.
10. 10 . The method of claim 9 wherein the range of pressures is selected to prevent fuel cell stack damage.
11. 11 . The method of claim 9 wherein the range of pressures is selected to prevent gas from leaking into the liquid coolant.
12. 12 . The method of claim 9 wherein maintaining the pressure comprises providing air via a check valve having a selected cracking pressure to an expansion tank coupled between the cathode input and the coolant loop.
13. 13 . A system comprising: a fuel cell stack having a cathode input; a coolant loop coupled to cool the fuel cell stack; and means for maintaining a pressure of coolant in the fuel cell stack to be greater than a pressure of gas in the cathode.
14. 14 . The system of claim 13 wherein the means for maintaining the pressure of coolant in the coolant loop to be greater than a pressure of gas in the cathode loop comprises an expansion tank coupled between the coolant loop and the cathode input and means for restricting flow of coolant in the coolant loop.
15. 15 . The system of claim 14 wherein the means for restricting flow of coolant coupled in the coolant loop comprises an orifice coupled in the coolant loop.
16. 16 . The system of claim 14 wherein the means for restricting flow of coolant in the coolant loop comprises a constant delta pressure control valve coupled in the coolant loop.
17. 17 . The system of claim 13 wherein the means for maintaining the pressure of coolant in the fuel cell stack to be greater than a pressure of gas in the cathode comprises an expansion tank coupled between the coolant loop and the cathode input wherein the expansion tank includes a spring-biased diaphragm separating coolant and gas in the cathode input.
18. 18 . The system of claim 13 wherein the means for maintaining the pressure of coolant in the fuel cell stack to be greater than a pressure of gas in the cathode comprises: an expansion tank coupled to the coolant loop; a pressurized gas buffer; and a pressure difference control valve coupled between the pressurized gas buffer and the expansion tank.
19. 19 . The system of claim 18 wherein the expansion tank includes a membrane coupled between coolant in the expansion tank and gas in the expansion tank.
20. 20 . The system of claim 13 wherein the means for maintaining the pressure of coolant in the fuel cell stack to be greater than a pressure of gas in the cathode comprises: an expansion tank coupled to the coolant loop; and a spring biased diaphragm disposed between an upper air portion of the expansion tank coupled to a cathode input and a lower coolant portion of the expansion tank coupled to the coolant loop.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with Government support under [S010174709] awarded by Clean Aviation Joint Undertaking. The Government has certain rights in the invention. BACKGROUND Proton exchange membrane fuel cells (PEMFC) are typically liquid cooled. Safety requires the coolant to be over-pressurized with respect to the oxidizer in the cathode and with respect to the fuel in the anode. This ensures that in a case of leakage the coolant leaks to the anode or cathode and not vice versa. This is important to prevent cooling circuit aeration and most importantly to prevent a risk of explosive oxidizer/fuel mixture accumulation in the cooling circuit or fuel leakage through the coolant circuit. It is a standard solution to include the expansion tank in the cooling circuit to pressurize it—typically to a constant pressure. However, this is not sufficient for the coolant pressurization for high power density PEMFCs that have thin bipolar plates that are easily damaged by high pressures. SUMMARY A system includes a fuel cell stack. A liquid coolant loop is coupled to provide coolant to the fuel cell stack. An expansion tank is coupled to the coolant loop and has an expansion tank inlet to couple to a fuel cell stack cathode inlet. An inlet check valve has a relative cracking pressure dpin and is coupled between the fuel cell stack cathode inlet and the expansion tank inlet to over-pressurize the coolant in the coolant loop. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified block flow diagram of a portion of an improved proton exchange membrane fuel cell-based power generator system having coolant over-pressurization according to an example embodiment. FIG. 2 is a block flow diagram illustrating an improved proton exchange membrane fuel cell-based power generator system according to an example embodiment. FIG. 3 is a simplified block flow diagram of a portion of an alternative improved proton exchange membrane fuel cell-based power generator system according to an example embodiment. FIG. 4 is a simplified block flow diagram of a portion of an alternative improved proton exchange membrane fuel cell-based power generator system according to an example embodiment. FIG. 5 is a simplified block flow diagram of a portion of an alternative improved proton exchange membrane fuel cell-based power generator system according to an example embodiment. FIG. 6 is a flowchart illustrating method of providing coolant over-pressurization according to an example embodiment. FIG. 7 is a block schematic diagram of a computer system to implement one or more example embodiments. DETAILED DESCRIPTION In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description of example embodiments is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims. Proton exchange membrane fuel cells (PEMFC) are typically liquid cooled. Safety requires the coolant to be over-pressurized with respect to the oxidizer gas in the cathode and with respect to the fuel in the anode. This ensures that in a case of leakage the coolant leaks that may aerate the anode or cathode and not vice versa. This is important to prevent cooling circuit aeration and most importantly to prevent a risk of explosive oxidizer/fuel mixture accumulation in the cooling circuit or fuel leakage through the coolant circuit. It is a standard solution to include the expansion tank in the cooling circuit to pressurize it—typically to a constant pressure. However, this is not sufficient for the coolant pressurization for high power density PEMFCs that have thin bipolar plates that are easily damaged by exposure to too much pressure. PEMFs would benefit by using narrow pressure difference control between the coolant and gas channels to avoid stack damage. For PEMFC used in aviation related applications, the pressure in gas channels changes not only with stack power, but also with flight altitude. The coolant pressure must follow the gas pressure, it must maintain the over-pressurization, but it must not exceed a pressure difference limit. An improved proton exchange membrane fuel cell system having a fuel cell stack coolant loop achieves coolant over-pressurization while not exceeding a pressure difference limit by connecting a gas side of a coolant expansion tank with fuel cell stack cathode inlet ducting to equalize their pressures. A coolant port of the coolant expansion tank is connected to an outlet of a fuel