Split-Beam Humidity Sensor for Fuel Cell Water Vapor Measurement

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Solution Overview

Problem

Fuel cells using polymer electrolyte membranes require accurate and reliable real-time measurement of water vapor concentrations to maintain optimal hydration levels, ensuring efficient operation, which existing technologies fail to provide consistently.

Innovation Solution

A humidity sensor apparatus that splits a light beam into two paths, one passing through a sample chamber with a flowing gas stream and the other through the instrument enclosure, using detectors to quantify light intensity and calculate water vapor partial pressure, with optional integration into fuel cell or combustion systems for feedback control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a single light beam path is used for humidity measurement, then the device structure is simple, but the measurement precision and reliability are insufficient

Engineering Contradiction:

Improvewater vapor concentration measurement accuracyVSAvoidoptical path structure complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The optical beam path is segmented into multiple separate paths (first path through sample chamber, second path through reference chamber) instead of using a single path. This segmentation allows independent measurement of water vapor concentration in the sample while using the reference path to compensate for environmental variations, thereby improving measurement precision without requiring complex real-time environmental compensation algorithms.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A reference chamber containing nitrogen gas is introduced as an intermediary element in the optical measurement system. This reference chamber acts as a mediator that provides a stable baseline for comparison, allowing the system to differentiate between water vapor in the sample and environmental interference factors, thus enhancing measurement accuracy while maintaining structural simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If real-time humidity measurement is implemented, then fuel cell performance is optimized, but measurement reliability becomes insufficient

Engineering Contradiction:

Improvereal-time measurement speedVSAvoidmeasurement reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system implements feedback by continuously comparing the optical signal from the sample chamber with the reference chamber and providing real-time humidity measurements to the fuel cell control system. This feedback loop enables dynamic adjustment of fuel cell operation based on actual humidity conditions, ensuring both real-time responsiveness and reliable control decisions through the dual-chamber comparison method.

Inventive Principle:

Principle #23Feedback

3Reliability

If existing humidity sensor technologies are used, then device complexity is low, but measurement reliability and accuracy are insufficient

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidsensor system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces conventional mechanical or capacitive humidity sensors with an optical measurement system that uses light transmission through chambers. This substitution eliminates the need for complex mechanical moving parts or calibration mechanisms while achieving higher reliability through the optical comparison method between sample and reference chambers, thereby improving measurement reliability without significantly increasing device complexity.

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

Enables quick, accurate, and reproducible measurements of water vapor partial pressure in gas streams, suitable for fuel cell operation and combustion process monitoring, allowing for optimized performance and control.

Implementation Method 1

A light source that emits a light beam directed within the instrument enclosure. A beam splitter is disposed within the instrument enclosure to split the light beam into a first split beam and a second split beam. A sample chamber configured to accept a flowing humidified gas stream can optionally be positioned within or outside of the instrument enclosure and disposed so that the first split beam passes through the sample chamber over a sample chamber path length.

Methodology Applied

Scientific EffectAbsorption Spectroscopy: Absorption Spectroscopy

Implementation Method 2

A beam splitter is disposed within the instrument enclosure to split the light beam into a first split beam and a second split beam.

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS7499169B2Fuel cell and product of combustion humidity sensor

Publication Date: 2009.03.03 ECOTEC SOLUTIONS

AI summary

Densities of water vapor can be detected and quantified at a high sampling rate for a gas. The gas can be contained within a sample chamber within or outside of an instrument enclosure. A first split beam passes through the enclosure and the sample chamber while a second split beam that passes only through the enclosure provides a reference that can be used to correct for ambient humidity in the instrument enclosure.