US-20260128336-A1 - HANDLING OF VARIABLE AND UNPREDICTABLE GAS COMPOSITION CHANGES TO MAXIMIZE HEALTH AND PERFORMANCE OF FUEL CELL SYSTEMS

US20260128336A1US 20260128336 A1US20260128336 A1US 20260128336A1US-20260128336-A1

Abstract

A disclosed fuel cell system includes a fuel inlet that receives a fuel gas from a fuel source, a gas analyzer that determines a composition of the fuel gas received by the fuel inlet, and a stack including fuel cells that generate electricity using the fuel gas received from the fuel source. The fuel cell system further includes a controller that controls at least one of a fuel utilization of the stack, a current generated by the stack, or a voltage generated by the stack, based on the composition of the primary fuel gas determined by the gas analyzer. The controller may control the fuel cell system by increasing or decreasing a fuel flow rate to thereby increase or decrease the voltage generated by the stack to maintain a predetermined target voltage or to maintain a predetermined rate at which usable fuel is supplied to the stack based on composition.

Inventors

Zeerek A. AHMAD
Adrian Ong
Suthitham KUSOLASAK
Ali ZARGARI
Jeffrey Crim CARLSON

Assignees

BLOOM ENERGY CORPORATION

Dates

Publication Date: 20260507
Application Date: 20260105

Claims (11)

1 . A method of controlling a fuel cell system, the method comprising: receiving a primary fuel gas from a first fuel source; determining, via a gas analyzer, a composition of the primary fuel gas; providing the primary fuel gas to a stack comprising fuel cells to thereby generate electricity using the primary fuel gas; and controlling at least one of a fuel utilization of the stack, current generated by the stack, or a voltage generated by the stack, based on the composition of the primary fuel gas determined by the gas analyzer.
2 . The method of claim 1 , further comprising determining a composition of the primary fuel gas based partially on first composition data generated by the gas analyzer and based partially on second composition data received from another data source.
3 . The method of claim 1 , further comprising: determining a fuel availability based on the composition of the primary fuel gas determined by the gas analyzer; and adjusting a fuel flow rate, based on the determined fuel availability, to maintain a predetermined rate at which usable fuel is supplied to the stack.
4 . The method of claim 3 , further comprising: determining that the fuel availability is below a fuel availability threshold; controlling the system to generate a blended fuel gas having an increased fuel availability by blending the primary fuel gas with a secondary fuel gas received from a second fuel source, the secondary fuel gas having a known fuel availability that is higher than the fuel availability threshold; and supplying the blended fuel to the stack.
5 . The method of claim 4 , further comprising controlling generation of the blended fuel by performing at least one of the following operations: using a closed loop control method to automatically blend an amount of the secondary fuel gas with the primary fuel gas to thereby generate the blended fuel gas having a predetermined minimum fuel availability or minimum lower heating value; using a closed loop control method to control a flow rate of the primary fuel gas, via a fuel control valve and flow meter, to thereby a maintain a predetermined flow setpoint of the primary fuel gas; or using an open loop control method to set a first constant flow rate of the primary fuel gas and to set a second constant flow rate of the secondary fuel gas.
6 . The method of claim 1 , further comprising automatically blending the primary fuel gas and secondary fuel gas having a fixed pressure when a pressure of the primary gas decreases to below the fixed pressure.
7 . The method of claim 1 , further comprising using a closed loop control method to control the voltage generated by the stack by performing operations comprising: measuring the voltage generated by the stack; and increasing or decreasing a fuel flow rate to thereby increase or decrease the voltage generated by the stack to maintain a predetermined target voltage.
8 . The method of claim 7 , further comprising: mixing anode exhaust gas from the stack with the primary fuel gas to generate a mixed fuel gas; supplying the mixed fuel gas to the stack; and controlling a rate at which the anode exhaust gas from the stack is mixed with the primary fuel gas to thereby control an oxygen/carbon ratio of the fuel supplied to the stack.
9 . The method of claim 8 , further comprising controlling the voltage generated by the stack by performing operations comprising: determining that a fuel utilization value is outside a predetermined range; and controlling the current generated by the stack to thereby control the voltage generated by the stack to maintain a predetermined target voltage.
10 . A method of controlling a fuel cell system, the method comprising: receiving a fuel gas from a fuel source; providing the fuel gas to a stack comprising fuel cells to thereby generate electricity using the fuel gas; determining a voltage generated by the stack; controlling the voltage generated by the fuel cell system according to a voltage control mode when at least one of a frequency or amplitude of voltage changes exceed one or more respective thresholds, wherein the voltage control mode comprises performing a closed loop control method to maintain a predetermined target voltage generated by the stack.
11 . The method of claim 10 , further comprising: controlling the voltage generated by the fuel cell system according to the voltage control mode for a predetermined time after determining that at least one of frequency or amplitude of voltage changes exceed the one or more respective thresholds; and controlling the fuel cell system according to a fuel composition control mode at times when voltage control mode is not performed, the fuel composition control mode comprising: determining, via a gas analyzer, a composition of the fuel gas; determining a fuel availability based on the composition of the primary fuel gas determined by the gas analyzer; and adjusting a fuel flow rate, based on determined fuel availability, to maintain a predetermined rate at which the fuel gas is supplied to the stack.

Description

FIELD Aspects of this disclosure relate to fuel cell systems and methods, and more particularly, to a fuel cell system and method of controlling the fuel cell system. BACKGROUND Fuel cells, such as solid oxide fuel cells, are electrochemical devices which can convert energy stored in fuels to electrical energy with high efficiencies. High temperature fuel cells include solid oxide and molten carbonate fuel cells. These fuel cells may operate using hydrogen and/or hydrocarbon fuels. There are classes of fuel cells, such as the solid oxide regenerative fuel cells, that also allow reversed operation, such that oxidized fuel can be reduced back to unoxidized fuel using electrical energy as an input. SUMMARY An embodiment fuel cell system includes a fuel inlet that receives a fuel gas from a fuel source, a gas analyzer that determines a composition of the fuel gas received by the fuel inlet, and a stack including fuel cells that generate electricity using the fuel gas received from the fuel source. The fuel cell system further includes a controller that controls at least one of a fuel utilization of the stack, current generated by the stack, or a voltage generated by the stack, based on the composition of the primary fuel gas determined by the gas analyzer. The controller may control the fuel cell system by increasing or decreasing a fuel flow rate to thereby increase or decrease the voltage generated by the stack to maintain a predetermined target voltage or to maintain a predetermined rate at which usable fuel is supplied to the stack based on composition. An embodiment method may include receiving a primary fuel gas from a first fuel source and determining a composition of the primary fuel gas using a gas analyzer. The method may include providing the primary fuel gas to a stack including fuel cells to thereby generate electricity using the primary fuel gas. The method may further include controlling at least one of a fuel utilization of the stack, current generated by the stack, or a voltage generated by the stack, based on the composition of the primary fuel gas as determined by the gas analyzer. A further disclosed method may include receiving a fuel gas from a fuel source, and providing the fuel gas to a stack including fuel cells to thereby generate electricity using the fuel gas. The method may include determining a voltage generated by the stack and determining that a frequency and/or amplitude of voltage changes exceed one or more respective thresholds. The method may further include controlling the voltage generated by the fuel cell system according to a voltage control mode. The voltage control mode may include performing a closed loop control method to maintain a predetermined target voltage generated by the stack. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate example embodiments of the disclosure, and together with the general description given above and the detailed description given below, serve to explain the features of the disclosure. FIG. 1 is a schematic illustration of a solid oxide fuel cell system, according to various embodiments. FIG. 2 is a schematic showing fuel flow through the fuel cell system of FIG. 1, according to various embodiments. FIG. 3A is a sectional perspective view of a central column of the fuel cell system of FIG. 1, according to various embodiments. FIG. 3B illustrates an anode hub structure connected to the column of FIG. 3A, according to various embodiments. FIGS. 4A-4C are perspective and sectional views of components of the central column of FIG. 3A, according to various embodiments. FIG. 5 is a sectional view of a central column of a fuel cell system, according to various embodiments. FIG. 6 is an isometric view of a modular fuel cell system enclosure, according to various embodiments. FIG. 7 is an isometric view showing a location of a hot box inside the module enclosure with the enclosure door removed, according to various embodiments. FIG. 8A an isometric view of a modular fuel cell system enclosure, according to various embodiments. FIG. 8B is a schematic diagram of the embodiment illustrated in FIG. 8A, according to various embodiments. FIG. 9 is a flow chart illustrating various operations of a method of controlling a fuel cell system, according to various embodiments. FIG. 10 is a flow chart illustrating various operations of a method of controlling a fuel cell system, according to various embodiments. FIG. 11 is a flow chart illustrating various operations in a method 1100 of controlling a fuel cell system, according to various embodiments. DETAILED DESCRIPTION The various embodiments are described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes,