Fuel Cell Pump Current Feedback for Humidity Control
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Solution Overview
Problem
Fuel cell modules face voltage drops due to improper water content in polymer electrolyte membranes, which is challenging to manage with existing technologies as they either overhydrate or dehydrate, leading to inefficiencies in gas density and humidity control.
Innovation Solution
A hydrogen recirculation pump is used as a humidity sensor to control balance of plant elements, adjusting water removal rates by modifying purge rates, gas flow rates, and cooling system temperatures based on changes in gas density and humidity, ensuring optimal membrane water content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water content in membranes is increased to improve conductivity, then membrane conductive performance is improved, but voltage drops occur when water content exceeds optimal range
Solution Approach 1:
The system uses pump current as a feedback signal to monitor humidity levels in the recirculation loop. The controller continuously adjusts water removal rates based on this feedback, maintaining membrane water content within the optimal range for conductivity while preventing voltage drops from over-hydration
Solution Approach 2:
The system dynamically changes operational parameters including pump speed, cooling system temperature set point, and balance of plant element settings based on real-time humidity conditions. This allows the system to adapt membrane water content to maintain optimal conductivity and voltage performance
2Speed
If pump speed is increased to improve gas circulation, then gas flow rate is improved, but energy consumption increases
Solution Approach 1:
The pump operates dynamically with variable speed rather than at constant high speed. The pump speed is adjusted in real-time based on humidity conditions and gas density requirements, allowing the system to achieve necessary circulation rates only when needed and reduce energy consumption during normal operation
Solution Approach 2:
The system changes pump operational parameters based on real-time conditions. When humidity increases and gas density changes, the pump speed is adjusted to maintain effective circulation while minimizing energy consumption, rather than operating at maximum speed continuously
3Loss of substance
If cooling system temperature is decreased to remove water vapor, then water removal rate is improved, but operational efficiency decreases due to excessive cooling
Solution Approach 1:
The cooling system temperature set point is adjusted based on feedback from pump current readings that indicate humidity levels. The controller increases the temperature set point when pump current indicates low humidity conditions, reducing excessive cooling and improving operational efficiency while still removing sufficient water vapor
Solution Approach 2:
The system dynamically changes cooling system temperature parameters based on real-time humidity conditions. Rather than maintaining constant low temperature for maximum water removal, the temperature set point is adjusted to match actual humidity needs, improving operational efficiency while maintaining adequate water vapor removal
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 effectively maintains the desired humidity range within the fuel cell stack, stabilizing voltage and improving operational efficiency by quickly responding to humidity changes, thus preventing voltage drops and enhancing overall module performance.
Implementation Method 1
The density of gasses in the fuel side of a stack varies with humidity. Accordingly, when the humidity in the fuel side of a cell stack increases, more energy is required to achieve the same volumetric flow rate in the recirculation loop.
Implementation Method 2
Raising the cooling system temperature set point causes air to be exhausted at a higher temperature, and the hotter air removes more water as vapor from the stack.
Implementation Method 3
the hotter air removes more water as vapor from the stack
Data Source
AI summary
A fuel cell module has a hydrogen recirculation pump and a controller. The controller receives a signal indicating the response of the pump to changes in the density or humidity of gasses in the hydrogen recirculation loop. The controller is programmed to consider the signal in controlling one or more balance of plant elements that effect the removal of water from the stack. In a process for operating the fuel cell module, the signal is considered when controlling one or more balance of plant elements that effect the removal of water from the stack. For example, an increase in current drawn from a constant speed or voltage recirculation pump indicates an increase in humidity and suggests that water should be removed from the stack, for example by increasing a coolant temperature set point.