Closed-Loop Reverse Electrodialysis Cell for Salinity Gradient Regeneration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing reverse electrodialysis systems face limitations such as the need for continuous sources of salt and fresh water, susceptibility to contamination, and inefficiencies in maintaining salinity gradients, which restrict their practical application and efficiency.
Innovation Solution
A salt gradient heat engine system incorporating a regeneration system with methods like membrane distillation, salt decomposition, electrodialysis, and forward osmosis to maintain and regenerate salinity differences, utilizing a heat pump to optimize thermal energy transfer and enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If open-loop RED battery is used, then continuous sources of salt and fresh water are required, but this limits practical locations and increases susceptibility to contamination
Solution Approach 1:
The closed-loop RED battery system regenerates its own salinity gradient by separating and concentrating salt from the water circulating through the system. The system uses its own output to maintain the concentration difference between compartments, eliminating the need for external salt and fresh water sources while preventing contamination from external sources.
Solution Approach 2:
The system dynamically adjusts the salinity concentration parameters within the closed loop by controlling the separation and concentration processes. By changing the concentration parameters internally rather than relying on external sources, the system maintains operational capability while avoiding contamination risks.
2Reliability
If closed-loop RED cell is used, then ongoing regeneration of salinity difference is achieved, but this requires energy intensive processes
Solution Approach 1:
The system employs feedback mechanisms where the electrical output from the RED cell during power generation mode is used to drive the regeneration process. The system automatically adjusts the regeneration intensity based on the current salinity gradient levels, using feedback signals from concentration sensors to maintain optimal operation while minimizing energy consumption.
Solution Approach 2:
The closed-loop system operates in periodic cycles, alternating between power generation mode and regeneration mode. During power generation, the salinity gradient is utilized to produce electricity; during regeneration, the gradient is restored. This periodic operation allows the system to maintain reliability while managing energy consumption through efficient cycling rather than continuous energy input.
3Reliability
If traditional regeneration methods are used, then salinity difference is restored, but process is energy intensive and inefficient
Solution Approach 1:
The system merges the power generation and regeneration functions into a single integrated closed-loop system. The regeneration process is combined with the power generation cycle, using the same physical infrastructure and fluid pathways. This merging eliminates the need for separate, energy-intensive regeneration operations and improves overall productivity by making the regeneration process a natural part of the operational cycle rather than a distinct, resource-consuming step.
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 efficiently maintains and regenerates salinity gradients, enabling continuous operation and reducing energy consumption, while generating electrical power and hydrogen from thermal energy.
Implementation Method 1
a first membrane configured to be selectively permeable to cations; the first membrane selectively allows cations to migrate toward the cathode
Implementation Method 2
a second membrane configured to be selectively permeable to anions; the second membrane selectively allows anions to migrate toward the anode
Implementation Method 3
a regeneration system comprising a heat pump. The regeneration system may include one or more of: a salt precipitation system, a membrane distillation system
Implementation Method 4
When the regeneration system includes the membrane distillation system, the membrane distillation system includes: a vessel containing at least a portion of the first or second saline solution, the vessel being covered by a hydrophobic membrane; and the heat pump being a configured to warm the vessel, and cool the opposite side of the hydrophobic membrane
Implementation Method 5
The system also includes a thermal optimization system configured to transfer thermal energy to the concentrated saline solution or the dilute saline solution
Data Source
AI summary
A method and system of generating electrical power or hydrogen from thermal energy is disclosed. The method includes separating, by a selectively permeable membrane, a first saline solution from a second saline solution, receiving, by the first saline solution and/or the second saline solution, thermal energy from a heat source, and mixing the first saline solution and the second saline solution in a controlled manner, capturing at least some salinity-gradient energy as electrical power as the salinity difference between the first saline solution and the second saline solution decreases. The method further includes transferring, by a heat pump, thermal energy from the first saline solution to the second saline solution, causing the salinity difference between the first saline solution and the second saline solution to increase. The method may include a process of membrane distillation, forward osmosis, evaporation, electrodialysis, and/or salt decomposition for further energy efficiency and power generation.