Fuel Cell Voltage Control via Current Pulses

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Solution Overview

Problem

Fuel cell systems face challenges in operating at reduced power output without negatively impacting their life cycle, particularly due to high voltage potentials that can lead to degradation.

Innovation Solution

The method involves interrupting air supply to the cathode, using a current pulse to rapidly decrease the electric voltage of the fuel cell stack, and regulating the voltage with a DC-DC transformer or adjustable electric load to maintain it within safe limits, while ensuring continuous hydrogen supply to the anode and utilizing recirculation circuits for oxygen management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the fuel cell system operates in a mode of reduced power output, then energy efficiency is improved and noise is reduced, but high voltage potentials may develop that negatively affect the life cycle of the fuel cell

Engineering Contradiction:

Improveenergy efficiencyVSAvoidlife cycle of the fuel cell

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies periodic action by implementing a control method that periodically monitors the operating mode of the fuel cell system. When transitioning to reduced power output mode, the system periodically adjusts the air supply and applies current pulses at specific intervals to prevent high voltage potentials, thereby maintaining both energy efficiency and fuel cell reliability throughout the operational cycle

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies parameter changes by dynamically adjusting key operating parameters including air supply quantity, current pulse amplitude and duration, and voltage thresholds. These parameter changes enable the system to operate efficiently at reduced power while preventing voltage conditions that would damage the fuel cell, thus resolving the contradiction between energy efficiency and reliability

Inventive Principle:

Principle #35Parameter changes

2Reliability

If air supply to the cathode is interrupted to rapidly decrease electric voltage, then voltage-induced degradation is prevented, but oxygen deficiency in the cathode may occur

Engineering Contradiction:

Improvedegradation preventionVSAvoidoxygen deficiency

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies partial action by partially interrupting air supply rather than completely stopping it. The system reduces air supply quantity to a controlled level that is sufficient to prevent oxygen deficiency and maintain cathode functionality, while still being restrictive enough to rapidly decrease electric voltage and prevent degradation

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent applies feedback by continuously monitoring the oxygen condition in the cathode and adjusting the air supply accordingly. The control system uses feedback signals about voltage levels and oxygen availability to dynamically regulate air supply quantity, ensuring that voltage-induced degradation is prevented while maintaining adequate oxygen supply to avoid harmful deficiencies

Inventive Principle:

Principle #23Feedback

3Loss of time

If a current pulse is applied to rapidly decrease electric voltage, then transition time is reduced, but additional control complexity is introduced

Engineering Contradiction:

Improvetransition timeVSAvoidcontrol complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The patent applies mechanics substitution by replacing complex mechanical voltage control mechanisms with electrical current pulses. Instead of using mechanical means to physically adjust voltage, the system uses controlled electrical current pulses that rapidly and precisely decrease voltage levels, reducing transition time while the control complexity is managed through electronic rather than mechanical systems

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 prevents voltage-induced degradation, reduces noise and energy usage, and allows for efficient transition between power modes without damaging the fuel cell system, thereby extending its life cycle and improving energy efficiency.

Implementation Method 1

Electrical energy is produced during the electrochemical reaction of the hydrogen and the oxygen to water

Methodology Applied

Scientific EffectElectrochemical reaction: Fuel Cell

Implementation Method 2

the current pulse initiates an increased use of the oxygen in the cathode, and that the electric voltage of the fuel cell stack thus decreases rapidly

Methodology Applied

Scientific EffectElectrochemical reaction: Fuel Cell

Data Source

PatentUS8192876B2Method for operating a fuel cell system in a mode of reduced power output

Publication Date: 2012.06.05 CELLCENTRIC GMBH & CO KG

AI summary

The invention relates to a method for operating a fuel cell system in a mode of reduced power output. The fuel cell system comprises a fuel cell stack (BS) having at least one fuel cell (BZ) with an anode (A), a cathode (K), and a proton exchange membrane, anode and cathode inlets, anode and cathode outlets, and a hydrogen and air supply. In order not to adversely affect the life span of the fuel cell system, the air supply to the cathode (K) is interrupted during the changeover to the mode of reduced power output, and an electric voltage (U) of the fuel cell stack (BS) is reduced by means of a current pulse.