Fuel Cell Exhaust Moisture Recovery Using a Two-Pass Sorbent Wheel
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Solution Overview
Problem
Hydrogen fuel cells produce water vapor as a waste product, which needs to be efficiently separated from the exhaust stream for efficient energy generation and to recover waste heat, while existing methods are inadequate in achieving high water removal efficiency and heat recovery.
Innovation Solution
An exhaust moisture removal system incorporating a sorbent wheel and interchanger that absorbs water under low humidity and rejects it under higher humidity, combined with a hydrogen evaporator that transfers heat to increase hydrogen fuel temperature, and condensate scuppers to capture liquid water, enabling >99% water capture and heat recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional water separation methods are used in hydrogen fuel cell exhaust systems, then the system structure is simple, but water removal efficiency is insufficient and heat recovery is inadequate
Solution Approach 1:
The exhaust stream is divided into two separate passes flowing in opposite directions through the sorbent wheel. The first pass flows from the exhaust source through the sorbent wheel to the interchanger, while the second pass flows from the interchanger through the sorbent wheel back to the exhaust source. This segmentation allows the sorbent to absorb water vapor in one pass and reject it in the other pass, achieving >99% water removal efficiency while maintaining a relatively simple system structure.
Solution Approach 2:
A sorbent wheel acts as an intermediary component between the two exhaust passes. The sorbent wheel includes a sorbent material that selectively absorbs water vapor from the exhaust stream under low humidity conditions and rejects it under high humidity conditions. This intermediary enables efficient water separation without requiring complex mechanical separation equipment.
2Productivity
If a sorbent wheel with rotating sorbent is used to absorb and reject water, then water removal efficiency increases, but the device complexity increases
Solution Approach 1:
The sorbent wheel rotates periodically to cycle the sorbent material between different operational zones. As the sorbent wheel rotates, the sorbent absorbs water vapor when exposed to the exhaust stream in the first pass, then rejects the absorbed water when exposed to the exhaust stream in the second pass. This periodic action enables continuous water removal with high capture rate while using a simple rotating mechanism rather than complex continuous separation equipment.
3Loss of energy
If the interchanger transfers heat between exhaust passes, then heat recovery efficiency improves, but system complexity increases
Solution Approach 1:
The interchanger is integrated into the existing exhaust flow path, merging the heat exchange function with the water separation process. The interchanger transfers heat between the first and second exhaust passes as they flow through the sorbent wheel, recovering waste heat without requiring separate heat exchanger equipment. This merging achieves efficient heat recovery while minimizing additional system complexity.
4Productivity
If condensate scuppers are added to capture liquid water, then water removal completeness improves, but device complexity increases
Solution Approach 1:
The condensate scuppers are positioned within the exhaust passageway to automatically capture and remove liquid water condensate as it forms during the cooling and dehumidification process. The scuppers utilize gravity and the natural flow of exhaust gases to collect and drain condensate without requiring external pumps or complex control systems. This self-service approach achieves complete water removal including liquid condensate while adding minimal system complexity.
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
The system effectively removes >99% of water vapor from hydrogen fuel cell exhausts and recovers waste heat, enhancing energy efficiency and reducing weight and fuel consumption in applications like commercial aircraft.
Implementation Method 1
a sorbent wheel including a sorbent configured to absorb water under a first humidity and reject the water under a second humidity that is higher than the first humidity
Implementation Method 2
an interchanger configured to remove a selected amount heat from the exhaust in the first pass of the exhaust outflow stream passageway within the interchanger and transfer the selected amount of heat to the exhaust in the second pass of the exhaust outflow stream passageway within the interchanger
Implementation Method 3
a hydrogen evaporator configured to transfer a selected amount of heat from the exhaust to the hydrogen fuel to increase a temperature of the hydrogen fuel
Implementation Method 4
one or more condensate scuppers configured to capture liquid water formed through condensation within the exhaust outflow stream passageway and remove the liquid water from the exhaust outflow stream passageway
Data Source
AI summary
An exhaust moisture removal system for an electric generation system including: a sorbent wheel; an interchanger; a hydrogen evaporator including an exhaust portion; and an exhaust outflow stream passageway configured to convey an exhaust from a hydrogen fuel cell of the electric generation system through a first pass and then through a second pass, the second pass being located downstream of the first pass, wherein the first pass of the exhaust outflow stream passageway passes through the sorbent wheel, then through the interchanger, and then through the hydrogen evaporator, and wherein the second pass of the exhaust outflow stream passageway passes through the hydrogen evaporator, then through the interchanger, and then through the sorbent wheel.