Fuel Cell Voltage Loss Calculation Using Transient Response Analysis
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Solution Overview
Problem
Current methods for measuring voltage loss in fuel cell systems are inefficient, requiring substantial time and complex equipment to accurately determine resistance components, and often fail to measure active and mass transfer resistances, making it difficult to assess fuel cell performance deterioration.
Innovation Solution
A method and system that rapidly calculate voltage losses due to ohmic, active, and mass transfer resistances using a controller, switch, and monitoring terminal, which senses and calculates voltage and current changes over time to derive resistance losses through linear regression analysis, allowing for quick and accurate determination of fuel cell deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistance measurement method using AC impedance is used to measure all resistance components, then measurement precision is improved, but measurement time increases substantially and equipment complexity increases
Solution Approach 1:
The patent segments the measurement process into two distinct phases: (1) a rapid preliminary measurement phase using simple voltage/current measurements to obtain initial resistance component estimates, and (2) an optional detailed verification phase using AC impedance measurement only for specific cells or conditions. This segmentation allows most measurements to be completed rapidly while maintaining the option for high-precision measurement when needed.
Solution Approach 2:
The patent applies partial action by measuring only the essential resistance components (ohmic and activation resistance) using the rapid method for all cells, while omitting the time-consuming mass transfer resistance measurement unless specifically required. This partial measurement approach achieves sufficient precision for most diagnostic purposes without the full time cost of complete AC impedance analysis.
2Measurement precision
If resistance measurement method using AC impedance is used to measure all resistance components, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the monitoring terminal multi-functional by enabling it to perform both simple voltage and current measurements (for rapid resistance estimation) and AC impedance measurements (for detailed analysis). This universal device can adapt its measurement mode based on diagnostic needs, eliminating the requirement for separate dedicated AC impedance measurement equipment for every cell.
Solution Approach 2:
The patent extracts the essential measurement functionality (voltage and current sensing) from the complex AC impedance measurement system. By separating the basic measurement capabilities that provide sufficient diagnostic information from the full AC impedance analysis, the system achieves accurate resistance component measurement using only simple, readily available monitoring equipment.
3Loss of time
If simplified resistance measurement method using AC milliohm meter or current cutoff method is used, then measurement time is reduced, but measurement precision deteriorates because only ohmic resistance is measured
Solution Approach 1:
The patent employs periodic action by applying transient current pulses to the fuel cell and measuring the voltage response at different time points. This periodic excitation allows the system to capture both the immediate ohmic resistance (from initial voltage change) and the activation resistance (from voltage recovery over time), providing comprehensive resistance component measurement through a single rapid test sequence.
Solution Approach 2:
The patent changes the measurement parameter from steady-state DC voltage (used in simple ohmic measurement) to transient voltage response following current interruption. By analyzing the voltage-time curve characteristics including both the initial drop and subsequent recovery, the system extracts multiple resistance components (ohmic and activation) from a single rapid measurement, achieving both speed and precision.
Data Source
AI summary
A method for calculating voltage loss of a fuel cell is provided. The method includes sensing an open circuit voltage that is generated in a stack when the switch is opened and detecting an operation voltage and an operation current that are generated in the stack when the switch is closed. A first change graph of voltage data over time is calculated using the voltage data and current data from a time when the switch is opened in a state where the switch is closed. A first voltage of a point at which a trend line for an interval where the voltage data linearly varies with the time meets the first change graph is sensed and then an ohmic resistance voltage loss is calculated using a difference between the first voltage and the operation voltage.