Fuel Cell Voltage Control via Intermittent Oxygen Supply
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Solution Overview
Problem
In fuel cell power supply systems, when load-required power decreases, existing methods lead to decreased energy efficiency due to excessive power generation and catalyst degradation, as the fuel cell's open circuit voltage becomes excessively high, causing elution of the cathode catalyst and reduced durability.
Innovation Solution
A voltage control method that interrupts electrical connection between the fuel cell and load in low load states, adjusts oxygen supply to maintain the open circuit voltage within a target range, and dynamically regulates oxygen amounts based on detected voltage states to prevent excessive power generation and catalyst degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fuel cell continues minute power generation to keep voltage within appropriate range, then the voltage is maintained, but excessive power generation occurs and energy efficiency decreases
Solution Approach 1:
The patent applies periodic action by intermittently supplying oxygen to the fuel cell in a controlled manner. Instead of continuous minute power generation, the system supplies oxygen in periodic intervals to maintain voltage within the appropriate range (0.05V to 0.95V per cell), thereby avoiding excessive power generation and improving energy efficiency while still maintaining voltage stability.
Solution Approach 2:
The patent changes the operating parameters of the fuel cell by controlling the oxygen supply rate and voltage levels. By adjusting these parameters dynamically based on the actual voltage state, the system optimizes the balance between maintaining voltage stability and minimizing energy waste from excessive power generation.
2Loss of energy
If the fuel cell power generation is stopped when load-required power is extremely small, then energy efficiency improves, but open circuit voltage becomes excessively high causing catalyst degradation
Solution Approach 1:
The patent applies preliminary anti-action by proactively controlling oxygen supply to prevent the open circuit voltage from rising to harmful levels. Before the voltage can become excessively high and cause catalyst degradation, the system intervenes by regulating oxygen supply to maintain voltage within the safe range, thereby preventing catalyst elution while still allowing the fuel cell to be stopped during low load conditions.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the voltage of the fuel cell and adjusting the oxygen supply accordingly. When the voltage approaches the upper limit of the appropriate range, the system reduces or stops oxygen supply to prevent excessive voltage rise and catalyst degradation, while ensuring energy efficiency is maintained.
3Reliability
If oxygen supply is increased to maintain voltage, then voltage stability is improved, but unnecessary power generation increases
Solution Approach 1:
The patent applies partial action by supplying only the necessary amount of oxygen required to maintain voltage within the appropriate range, rather than providing excessive oxygen that would lead to unnecessary power generation. This controlled partial oxygen supply ensures voltage stability while minimizing unwanted power output.
4Adaptability or versatility
If the fuel cell operates at extremely low power output, then load requirements are met, but system energy efficiency decreases
Solution Approach 1:
The patent applies dynamics by enabling the fuel cell to dynamically switch between different operating states based on load requirements. The system can operate at extremely low power output when needed to meet load requirements, while using controlled oxygen supply and voltage management to minimize energy efficiency losses that would otherwise occur in such low-power operation modes.
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 method maintains energy efficiency by avoiding unnecessary power generation, reduces catalyst degradation, and improves fuel cell durability by keeping the open circuit voltage within optimal limits.
Implementation Method 1
a fuel cell configured to supply an electric power to a load
Implementation Method 2
hydrogen remaining in the anode passage permeates to the cathode passage via the electrolyte membrane of the fuel cell
Implementation Method 3
the reaction by which hydrogen is oxidized on the cathode proceeds
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A voltage control method for a fuel cell (100) includes: interrupting electrical connection between the fuel cell and a load (170, 172) in a low load state; supplying oxygen to the fuel cell in accordance with a preset condition during the electrical connection is interrupted; detecting an OCV (open circuit voltage) of the fuel cell after oxygen is supplied to the fuel cell in accordance with the preset condition; reducing an amount of oxygen supplied to the fuel cell when the OCV is higher than a target voltage by a first value or larger; increasing the amount of oxygen when the OCV is lower than the target voltage by a second value or larger; and keeping the amount of oxygen when the OCV is lower than a sum of the target voltage and the first value and higher than a value obtained by subtracting the second value from the target voltage.