Electrochemical Compressor Membrane Swelling for Ammonia Transport
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Solution Overview
Problem
Conventional electrochemical compressors using aqueous solvents have limitations in transporting larger molecules due to restricted channel sizes in ion exchange membranes, which hampers the efficient pressurization of working fluids containing condensable refrigerants like ammonia and hydrogen.
Innovation Solution
The use of a non-aqueous solvent with polar molecules to swell the ion exchange membrane channels to sizes between 200 nm to 400 nm, enabling the transport of larger molecules, such as ammonia and hydrogen, by forming an ionomer with polar ionic groups attached to nonpolar chains and applying an electric potential gradient across the membrane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If aqueous solvents are used in conventional electrochemical compressors, then the ion exchange membrane channels remain restricted in size, but this limits the transport of larger molecules such as ammonia and hydrogen
Solution Approach 1:
The patent changes the solvent parameter from aqueous to non-aqueous (specifically polar aprotic solvents like acetonitrile, dimethyl carbonate, or ethyl methyl carbonate). This parameter change causes the ion exchange membrane channels to swell from restricted sizes to expanded sizes (200-400 nm), enabling transport of larger molecules while maintaining electrochemical functionality
Solution Approach 2:
The patent creates a composite system combining non-aqueous polar aprotic solvent with the ion exchange membrane (Nafion®). This composite approach allows the solvent molecules to interact with the membrane structure, causing controlled swelling that creates adequate transport channels for ammonia and hydrogen molecules while preserving the membrane's ion exchange properties
2Quantity of substance
If ion exchange membrane channels are swollen to larger sizes, then transport of larger molecules is enabled, but the membrane structure must be carefully controlled to maintain functionality
Solution Approach 1:
The patent carefully controls the solvent parameters (choosing specific polar aprotic solvents with appropriate dipole moments and molecular sizes) to achieve controlled swelling. This parameter control ensures channels expand to the optimal 200-400 nm range without excessive swelling that would compromise membrane integrity or electrochemical performance
Solution Approach 2:
The non-aqueous polar aprotic solvent acts as an intermediary that mediates between the membrane structure and the working fluid molecules. The solvent molecules interact with the membrane's ionic groups, causing controlled structural modification that facilitates transport while the solvent itself can be removed or replaced, providing a reversible and controllable mechanism
3Reliability
If non-aqueous polar solvents are used to swell membrane channels, then electrostatic attraction to polar ionic groups enhances solvent-membrane interaction, but selection of appropriate solvent becomes more critical
Solution Approach 1:
The patent specifies particular parameter ranges for the solvent: polar aprotic character, specific dipole moment ranges, and molecular size constraints. These parameter specifications ensure strong electrostatic interaction with the membrane's polar ionic groups while excluding solvents that would cause excessive swelling or incompatible chemical reactions, thus balancing reliability with controlled versatility
Solution Approach 2:
The patent applies different solvent properties at different locations: the polar aprotic solvent specifically interacts with the polar ionic groups in the membrane channels while the nonpolar portions of the membrane structure remain relatively unaffected. This local quality approach ensures strong solvent-membrane interaction where needed without compromising overall membrane stability
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 allows for the efficient pressurization of working fluids, enhancing the migration of electrochemically active components and refrigerants, thereby improving the performance of electrochemical compression systems in refrigeration and heat transfer applications.
Implementation Method 1
The polar molecules of the non-aqueous solvent are associated with and electrostatically attracted to the polar ionic groups of the ion exchange membrane
Implementation Method 2
solvating a non-aqueous solvent comprising polar molecules with an ion exchange membrane by associating the polar molecules of the non-aqueous solvent with polar ionic groups
Implementation Method 3
an ion exchange membrane disposed between and in electrical contact with the cathode and the anode to pass an electrochemically motive material of the working fluid from the anode to the cathode
Implementation Method 4
applying an electric potential gradient across the ion exchange membrane through the anode and cathode to thereby enable an electrochemically motive material formed from the working fluid to pass from the anode to the cathode
Implementation Method 5
An electrochemical compressor is a device that raises the pressure of a component of a working fluid using an electrochemical process
Data Source
AI summary
An electrochemical compressor includes one or more electrochemical cells through which a working fluid flows, and an external electrical energy source electrically connected to the electrochemical cell. Each electrochemical cell includes an anode connected to the electrical energy source; a cathode connected to the electrical energy source; an ion exchange membrane disposed between and in electrical contact with the cathode and the anode to pass an electrochemically motive material of the working fluid from the anode to the cathode, the ion exchange membrane comprising polar ionic groups attached to nonpolar chains; and a non-aqueous solvent comprising polar molecules, the polar molecules of the non-aqueous solvent being associated with and electrostatically attracted to the polar ionic groups of the ion exchange membrane.