Falling Pond Brine Circulation for Salinity Gradient Control
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Solution Overview
Problem
Existing Salinity Gradient Solar Pond (SGSP) systems face challenges in maintaining the salinity gradient efficiently, particularly due to upward diffusion of salt, which affects their reliable and efficient operation, especially when scaling up for commercialization, as traditional methods like Surface Wash require additional land, water, and heat losses.
Innovation Solution
The Falling Pond method, facilitated by a Falling Pond Device, continuously cycles the pond's layers downward by extracting water from the saturated brine and returning it to the top, matching the rate of salt diffusion, using a Flash Tank Evolver and Mix Tank Condenser to manage brine circulation and reduce water and heat losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Surface Wash method is used to control salinity gradient, then salt diffusion is managed, but additional land, water, and heat losses occur
Solution Approach 1:
The patent extracts and removes the harmful upward diffusion of salt from the system by implementing a Falling Pond Device that continuously cycles brine downward, extracting salt from the upper layers and returning it to the lower layers, thereby eliminating the need for water-intensive surface washing methods
Solution Approach 2:
The Falling Pond Device acts as an intermediary mechanism between the upper and lower brine layers, facilitating controlled salt redistribution through a mechanical cycling system that prevents direct contact between surface water and salt-laden brine, thus avoiding water loss
2Reliability
If the Surface Wash method is used to control salinity gradient, then salt diffusion is managed, but additional land requirements increase
Solution Approach 1:
The patent merges the salt control function directly into the existing SGSP structure by integrating the Falling Pond Device within the pond's brine circulation system, eliminating the need for separate evaporation ponds or additional land areas required by traditional Surface Wash methods
3Reliability
If the Surface Wash method is used to control salinity gradient, then salt diffusion is managed, but heat losses increase
Solution Approach 1:
The Falling Pond Device implements continuous brine cycling that maintains constant thermal contact between the hot lower brine and the cooling mechanism, ensuring continuous heat recovery and utilization without the intermittent heat losses associated with periodic surface washing operations
Solution Approach 2:
The patent converts the harmful upward salt diffusion into a beneficial process by using the rising warm brine as the working fluid for power generation while simultaneously using the Falling Pond Device to redirect it downward, thereby converting what would be a loss into a productive thermal cycle
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 minimizes water, heat loss, and land requirements, making it more cost-effective and practical for large-scale commercialization by maintaining the salinity gradient efficiently and reducing parasitic losses, enabling SGSP systems to operate effectively as a reliable renewable energy source.
Implementation Method 1
solar energy is absorbed by the pond's bottom which in turn heats the adjacent salt-saturated fluid (the 'Lower Convective Zone', or LCZ, in FIG. 1)
Implementation Method 2
solar energy is absorbed by the pond's bottom
Implementation Method 3
a portion of the hot brine is routed into the flash tank evolver which drives the H2O off of the saturated brine
Implementation Method 4
the superheated steam is drawn into the mix tank condenser where it is condense by contact with cool water
Implementation Method 5
A 'Falling Pond Device' shown in the figure is intended to continuously maintain the salinity gradient in-place by extracting water from the saturated brine on the bottom of the pond and moving it to the top
Data Source
AI summary
A Salinity Gradient Solar Pond has saturated salt water in the bottom of the pond and nearly fresh water at the top, with a gradient zone between the top and bottom. Due to this salinity stratification the upward diffusion of salt is a natural consequence in SGSP's. This upward diffusion of salt has been found to range 60-80 gr/m2/day (Tabor, H.; Solar Ponds, Solar Energy, v. 27 (3), pp. 181-194, 1981 and v. 30 (1), pp. 85-86, 1983). Controlling the salinity gradient in SGSP systems is vital to their reliable operation. One proposed method for controlling the salinity gradient is the so called “Falling Pond” method, where water is extracted from the saturated bottom layer by some means and returned to the nearly fresh upper layer. This action creates a downward velocity in the pond's layers which can be matched to counter the upward diffusion of salt, thereby maintaining the pond's gradient stationary in space.