Fuel Cell System Dynamic SOC Control for Cold Start
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Solution Overview
Problem
Fuel cell systems in vehicles face delays in obtaining vehicle running permission due to the need to maintain a secondary cell's SOC above a predetermined value, leading to inefficient power usage and prolonged startup times, especially at low temperatures where hydrogen concentration issues can cause fuel cell power generation delays.
Innovation Solution
A fuel cell system with a controller that calculates discharge permission energy and running permission delay times to permit vehicle operation by the secondary cell when the fuel cell is unable to generate power, limiting energy consumption and stopping the circulation pump when necessary to expedite fuel cell startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SOC of the secondary cell is kept above a predetermined value to ensure power availability, then the reliability of vehicle operation is improved, but the time to obtain vehicle running permission increases and the power of the secondary cell cannot be effectively used
Solution Approach 1:
The predetermined SOC value is changed from a static fixed threshold to a dynamic value that varies based on temperature conditions. At low temperatures where fuel cell startup is delayed, the allowed SOC can drop below the normal threshold, enabling the vehicle to start using secondary cell power sooner. This dynamic adjustment resolves the contradiction by adapting the reliability criterion to environmental conditions.
Solution Approach 2:
The system changes the parameter of SOC threshold based on temperature conditions. When temperature is low and fuel cell startup is expected to be delayed, the SOC threshold parameter is lowered, allowing the secondary cell to provide power even at lower charge levels. This parameter change enables timely vehicle operation while maintaining sufficient power reserves.
2Loss of time
If the SOC threshold is lowered to reduce startup time, then the time to obtain vehicle running permission is reduced, but the power availability of the secondary cell becomes insufficient
Solution Approach 1:
The SOC threshold is made dynamic rather than fixed, adjusting based on temperature and fuel cell startup conditions. This allows the system to lower the threshold temporarily during cold startups when needed, then restore normal thresholds when conditions improve, ensuring power availability is maintained overall while enabling faster startup when necessary.
Solution Approach 2:
The system continuously monitors temperature, fuel cell status, and SOC levels to dynamically adjust the allowed SOC threshold. This feedback mechanism ensures that the threshold is lowered only when actually needed (low temperature, delayed fuel cell startup) and raised when power reserves are sufficient, balancing startup speed with power availability.
3Reliability
If the circulation pump operates continuously to maintain hydrogen concentration, then the fuel cell startup reliability is improved, but the energy consumption increases and startup time is prolonged
Solution Approach 1:
The circulation pump operation is changed from continuous to periodic or conditional operation. The pump operates only when needed to maintain hydrogen concentration, such as during initial startup phases or when hydrogen levels drop below thresholds. This periodic operation maintains fuel cell reliability while significantly reducing energy consumption compared to continuous operation.
Solution Approach 2:
The system monitors its own hydrogen concentration levels and activates the circulation pump only when self-diagnosis indicates hydrogen depletion. This self-service approach ensures the pump operates minimally to maintain reliability, avoiding unnecessary energy consumption when hydrogen levels are already sufficient.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the time to obtain vehicle running permission by optimizing secondary cell energy use and preventing hydrogen shortages during fuel cell startup, ensuring timely vehicle operation even at low temperatures.
Implementation Method 1
A fuel cell (FC) is a power generation device that generates electrical energy by electrochemical reaction between hydrogen (H2), which serves as fuel gas, and oxygen (O2), which serves as oxidant gas
Implementation Method 2
a circulation pump configured to circulate fuel off-gas discharged from a fuel electrode of the fuel cell and return the fuel off-gas to the fuel cell
Data Source
AI summary
A fuel cell system comprising: the fuel cell, the secondary cell and a controller, wherein, when a power generation pretreatment of the fuel cell is carried out, and when there is a request from the fuel cell to run the vehicle by output power of the secondary cell, the controller calculates discharge permission energy of the secondary cell, calculates a running permission delay request time from the discharge permission energy, which is a time necessary from the request to run the vehicle to the permission to run the vehicle, and measures a running permission delay time, which is a time that elapsed from the request to run the vehicle, and wherein, when the running permission delay request time value is smaller than the running permission delay time value, the controller permits the vehicle to run.