Evaluation and optimization method of ion salt differential power generation unit based on loss factor

Abstract

Disclosed are an evaluation and optimization method of an ion salt differential power generation unit based on a loss factor, a periodic unit of large-scale ion salt differential power generation, a single anion selection membrane system and a cation selection membrane system, and output performance characterization and input parameter classification. Circuit analysis is performed, and a power loss factor of the ion salt differential power generation unit is proposed to evaluate the power loss of the ion salt differential power generation unit. Based on the power loss factor, the output performance of the ion salt differential power generation unit is optimized from three aspects of channel parameters, ion species and common parameters. Based on the optimized single anion selection membrane system and cation selection membrane system, corresponding ion salt differential power generation units are constructed to achieve high output performance and low loss factor, and are applied to large-scale ion salt differential power generation systems.

Description

Technical Field

[0001] This invention relates to the field of power generation technology, and in particular to an evaluation and optimization method for ion salt difference power generation units based on loss factors. Background Technology

[0002] Ion salinity gradient power generation utilizes the concentration difference between highly saline water (such as seawater) and less saline water (such as river water) to drive ions through an ion-selective membrane, creating a potential difference that generates electricity. Ion salinity gradient energy is a potentially powerful clean energy source with wide applications in river estuaries, islands, hydroelectric power plants, and wastewater treatment plants. Most existing technologies focus on single-ion-selective membrane systems, such as using only cation-selective membranes. While single-ion-selective membranes are simple in structure and easy to control, their inability to be used in multi-stage series significantly limits output performance. Large-scale ion salinity gradient power generation systems require alternating arrangements of anion and cation-selective membranes with varying concentrations to utilize the potential generated by each concentration gradient. Although the power generation is large, there is a lack of analysis and evaluation for the periodic units of large-scale ion salinity gradient power generation. Therefore, there is an urgent need to develop a new method for evaluating and optimizing ion salinity gradient power generation units with common characteristics to guide the entire large-scale ion salinity gradient power generation system.

[0003] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] To address the shortcomings or defects of the existing technology, an evaluation and optimization method for ion salinity gradient power generation units based on loss factors is provided. This method improves the utilization efficiency of salinity gradient energy and evaluates and optimizes large-scale ion salinity gradient power generation systems. The objective of this invention is achieved through the following technical solutions.

[0005] An evaluation and optimization method for ion salinity gradient power generation units based on loss factors includes,

[0006] Step S100: Construct a periodic ion salt difference power generation unit, and measure the input parameters and characterize the output performance of the ion salt difference power generation unit;

[0007] Step S200: Characterize the output performance and classify the input parameters of the single anion-selective membrane system and the single cation-selective membrane system corresponding to the ion salt difference power generation unit;

[0008] Step S300: Perform circuit analysis on the ion salt difference power generation unit and the single anion-selective membrane system and cation-selective membrane system, propose the power loss factor of the ion salt difference power generation unit, and calculate the magnitude of the loss factor to evaluate the power loss of the ion salt difference power generation unit.

[0009] Step S400: Optimize the output performance of the ion salt difference power generation unit based on the power loss factor. According to the characteristics of the loss factor, determine the relative magnitude of the permeation current of the single anion-selective membrane system and the cation-selective membrane system, and optimize the one with the smaller permeation current.

[0010] Step S500: Based on the optimization of channel parameters, prioritize changing the surface charge density of the system with the smaller permeation current, and then change the channel length and radius; based on the optimization of ion types, prioritize replacing the ions corresponding to the system with the smaller permeation current to improve the ion diffusion coefficient; based on the optimization of common parameters, changes in common parameters will cause changes in the permeation current of both the single anion-selective membrane system and the cation-selective membrane system, adjust the amplitude of the common parameters to make the permeation current of the two consistent.

[0011] Step 600: Based on the optimized single anion-selective membrane system and cation-selective membrane system, construct the corresponding ion salt gradient power generation unit for application in large-scale ion salt gradient power generation systems.

[0012] In the method described, the periodic ion salt gradient power generation unit includes a low-salt chamber, an anion-selective membrane, a high-salt chamber, a cation-selective membrane, and a low-salt chamber; the single anion-selective membrane system includes the low-salt chamber, anion-selective membrane, and high-salt chamber in the ion salt gradient power generation unit, and the single cation-selective membrane system includes the high-salt chamber, cation-selective membrane, and low-salt chamber in the ion salt gradient power generation unit.

[0013] In the method described, the output performance includes the current-voltage characteristic curve, permeation current, diffusion potential, and maximum power. The permeation current, diffusion potential, and maximum power of the ion salt gradient power generation unit are expressed as I0, E0, and P0, respectively, while the permeation current, diffusion potential, and maximum power of the single anion-selective membrane system are expressed as I... a E a P a The permeation current, diffusion potential, and maximum power of a single cation-selective membrane system are expressed as I. c E c P c .

[0014] In the method described, the input parameters are classified into channel parameters, ion types, and common parameters, wherein the channel parameters include the surface charge density σ of the anion-selective membrane. a Length L a radius R a Surface charge density σ of cation-selective membrane c Length L c radius R c Ion types include anion diffusion coefficient D a cation diffusion coefficient D cCommon parameters include high concentration of C h Low concentration of C l High concentration side temperature T h Low concentration side temperature T l .

[0015] In the method described, the circuit analysis of the ion salt difference power generation unit, the single anion-selective membrane system and the cation-selective membrane system applies the principle of current conservation. The potentials of the single anion-selective membrane system and the cation-selective membrane system under the same current are connected in series, and the total potential is equal to the potential of the ion salt difference power generation unit.

[0016] In the method described, the power loss factor Lf measures the power loss of the ion salt difference power generation unit compared to a single anion-selective membrane system and a cation-selective membrane system. The power loss factor Lf is greater than or equal to zero, taking condition I. a =I c or E a =0 or E c =0, meaning that the closer the permeation current or the smaller the diffusion potential of a single anion-selective membrane system and a cation-selective membrane system, the smaller the power loss factor Lf.

[0017]

[0018] In the method described, the optimization strategy for the ion salt difference power generation unit is to make the permeation current of the single anion-selective membrane system and the cation-selective membrane system as close as possible, so as to achieve a low loss factor, while ensuring that the diffusion potential does not decrease.

[0019] In the method described, the magnitude of the permeation current of one system is changed by optimizing the channel parameters without affecting the permeation current of another system.

[0020] In the method described, changes in ion species and common parameters lead to alterations in the permeation current of both the single anion-selective membrane system and the single cation-selective membrane system.

[0021] Compared with the prior art, the beneficial effects of this invention are as follows:

[0022] This invention determines the output performance of periodic ion-salinity gradient (ISG) power generation units and corresponding single systems in large-scale ion-salinity gradient power generation systems. It proposes an evaluation index based on the loss factor, reflecting the performance utilization efficiency of the ISG power generation unit compared to the single system. Based on this evaluation index, optimization of the ISG power generation unit from the perspectives of channel parameters, ion types, and common parameters is beneficial for achieving high output performance and low loss factor, and can be further applied to large-scale ISG power generation systems. This invention enables the evaluation and optimization of ISG power generation units, has significant social and economic benefits, and can be widely applied in the power generation field.

[0023] The description provided is merely an overview of the technical solution of this invention. In order to make the technical means of this invention clearer and more understandable, so that those skilled in the art can implement it according to the contents of the specification, and to make the described and other objects, features and advantages of this invention more obvious and understandable, specific embodiments of this invention are described below. Attached Figure Description

[0024] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0025] In the attached diagram:

[0026] Figure 1 A flowchart illustrating an evaluation and optimization method for an ion salt difference power generation unit based on a loss factor, provided as an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of an ion salinity gradient power generation unit, which is provided as another embodiment of the present invention, for evaluating and optimizing an ion salinity gradient power generation unit based on a loss factor.

[0028] Figure 3 The current-voltage curves of an ion salt difference power generation unit, a single anion-selective membrane system, and a single cation-selective membrane system are provided for another embodiment of the present invention to evaluate and optimize an ion salt difference power generation unit based on a loss factor.

[0029] Figure 4 The output performance and evaluation index results of ion salinity difference power generation units of different ion types are provided by another embodiment of the present invention for the evaluation and optimization method of ion salinity difference power generation units based on loss factor.

[0030] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0031] The following will refer to the appendix. Figures 1 to 4Specific embodiments of the invention will be described in more detail below. While specific embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0032] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0033] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0034] To better understand, such as Figure 1 As shown, an evaluation and optimization method for ion salt difference power generation units based on loss factors includes,

[0035] Step S100: Construct a periodic unit for large-scale ion salinity gradient power generation, and measure the input parameters and characterize the output performance of the ion salinity gradient power generation unit.

[0036] Step S200: In order to perform evaluation analysis, the output performance of the single anion-selective membrane system and the input parameter classification of the ion salt difference power generation unit corresponding to the ion-selective membrane system in step S100 are characterized and classified.

[0037] Step S300: Perform circuit analysis on the ion salt difference power generation unit in Step 1 and the single anion-selective membrane system and cation-selective membrane system in Step 2, propose the power loss factor of the ion salt difference power generation unit, calculate the magnitude of the loss factor, and use this value to evaluate the power loss of the ion salt difference power generation unit.

[0038] Step S400: Optimize the output performance of the ion salt gradient power generation unit based on the power loss factor. According to the characteristics of the loss factor, determine the relative magnitudes of the permeation current in the single anion-selective membrane system and the cation-selective membrane system, and optimize the system with the smaller permeation current.

[0039] Step S500: Based on channel parameter optimization, prioritize changing the surface charge density of the system with lower permeation current, and then change the channel length and radius. Based on ion type optimization, prioritize replacing the ions corresponding to the system with lower permeation current to improve the ion diffusion coefficient. Based on common parameter optimization, changes in common parameters will cause changes in the permeation current of both the single anion-selective membrane system and the cation-selective membrane system; adjust the amplitude of the common parameters to make the permeation currents of the two systems consistent.

[0040] Step 600: Based on the optimized single anion-selective membrane system and cation-selective membrane system, construct the corresponding ion salinity gradient power generation unit to achieve high output performance and low loss factor, so as to apply it to large-scale ion salinity gradient power generation system.

[0041] In one embodiment, such as Figure 2 As shown, preferably, in the method described, the ion salt gradient power generation unit is a periodic unit for large-scale ion salt gradient power generation, which includes a low-salt chamber, an anion-selective membrane, a high-salt chamber, a cation-selective membrane, and a low-salt chamber. A single anion-selective membrane system includes the low-salt chamber, anion-selective membrane, and high-salt chamber in the ion salt gradient power generation unit; a single cation-selective membrane system includes the high-salt chamber, cation-selective membrane, and low-salt chamber in the ion salt gradient power generation unit. Input parameters are classified into channel parameters, ion types, and common parameters, where the channel parameter is the surface charge density σ of the anion-selective membrane. a Length L a radius R a Surface charge density σ of cation-selective membrane c Length L c radius R c The ion type is anion with diffusion coefficient D. a cation diffusion coefficient D c The common parameter is high concentration of C. h Low concentration of C l High concentration side temperature T h Low concentration side temperature T l ,

[0042] In one embodiment, the output performance of the method includes current-voltage characteristic curves, permeation current, diffusion potential, and maximum power, wherein the permeation current, diffusion potential, and maximum power of the ion salt gradient power generation unit are expressed as I0, E0, and P0, respectively, and the permeation current, diffusion potential, and maximum power of the single anion-selective membrane system are expressed as I... a E a P a The permeation current, diffusion potential, and maximum power of a single cation-selective membrane system are expressed as I. c E c P cThe circuit analysis of the ion salt gradient power generation unit, the single anion-selective membrane system, and the cation-selective membrane system applies current conservation. Under the same current, the potentials of the single anion-selective membrane system and the cation-selective membrane system are connected in series, and the total potential is equal to the potential of the ion salt gradient power generation unit. The power loss factor is defined as Lf, as shown below. Applying Cauchy's inequality to the expression for Lf, it can be seen that the power loss factor Lf is greater than or equal to zero. Taking the equality condition I... a =I c or E a =0 or E c =0, meaning the closer the permeation currents of a single anion-selective membrane system and a cation-selective membrane system are, or the smaller the diffusion potential, the smaller the power loss factor Lf. Without wanting a decrease in diffusion potential, making the permeation currents of a single anion-selective membrane system and a cation-selective membrane system as close as possible can achieve a low power loss factor.

[0043]

[0044] In this embodiment, such as Figure 3 As shown, given the preferred current-voltage (volt-ampere) curves for both the single anion-selective membrane system and the single cation-selective membrane system, the current-voltage (volt-ampere) curve of the ion-salt gradient power generation unit can be obtained based on current conservation, and the corresponding diffusion potential and permeation current can be derived. According to the expression for the loss factor Lf, the loss factor Lf of the ion-salt gradient power generation unit under this condition can be calculated to be 0.1, meaning that compared to the combined power of the single anion-selective membrane system and the cation-selective membrane system, the ion-salt gradient power generation unit experiences a 10% loss.

[0045] In another embodiment, the finite element method is used to solve the Poisson equation and the Nernst-Planck equation to simulate and optimize the power generation of a single anion and cation membrane. The baseline operating condition is set as a 100 mM / 1 mM sodium chloride solution, and the absolute value of the surface charge density of both the anion and cation nanochannels is 0.01 C / m³. 2 All have a length of 1000 nm and a radius of 8 nm. Table 1 shows the optimization results of the ion salt difference power generation unit under different geometric conditions. Since the diffusion coefficient of chloride ions is 2.03 m... 2 / s, while the diffusion coefficient of sodium ions is 1.33m. 2Since the diffusion coefficient of chloride ions is significantly greater than that of sodium ions, the osmotic current of the cation-selective channel is less than that of the anion-selective channel. Therefore, the geometric parameters of the cation-selective channel are optimized. When the length of the cation-selective channel is reduced, the cation migration path becomes shorter, and the diffusion resistance decreases, thus increasing power. Simultaneously, the osmotic current values ​​of the anion and cation channels become closer, significantly improving the loss factor and successfully optimizing the ion-salt gradient power generation unit. Similarly, when the radius of the cation-selective channel is increased, the area available for cation migration increases, and the flux brought by cations increases, thus increasing power. Furthermore, the osmotic current values ​​of the anion and cation channels become closer, significantly improving the loss factor and successfully optimizing the ion-salt gradient power generation unit.

[0046] Table 1 Optimization of the ion salt difference power generation unit based on channel parameters

[0047]

[0048] In this embodiment, such as Figure 4 As shown, preferably, the baseline operating condition is that the absolute value of the surface charge density of both the anion and yin-yang nanochannels is 0.01 C / m. 2 All ions have a length of 1000 nm and a radius of 8 nm. The ion salt gradient power generation unit was optimized by changing the types of ions used. Four types of solutions—sodium chloride, potassium chloride, potassium fluoride, and sodium fluoride—were used for power generation. The diffusion coefficient of fluoride ions is 1.48 nm. 2 / s, the diffusion coefficient of potassium ions is 1.96m. 2 / s. By Figure 4 It can be seen that, regarding the loss factor, due to the symmetry of the cation-anion selective channels, the greater the difference in diffusion coefficients between cations and anions, the greater the difference in osmotic current. Therefore, the sodium chloride solution has the largest loss factor at 8.07%, followed by the potassium fluoride solution at 3.44%, then the sodium fluoride solution at 0.57%, and finally the potassium chloride solution at 0.08%. This demonstrates that the type of cations and anions affects their diffusion coefficients, thus influencing the osmotic current and the loss factor. In terms of output power, the potassium chloride solution is significantly superior to the sodium chloride solution because the diffusion coefficient of the cations is significantly increased. In conclusion, the ion salt gradient power generation unit based on ion type has been optimized.

[0049] In another embodiment, as shown in Table 2, preferably, the ion salt gradient power generation unit is optimized by changing common parameters such as concentration ratio. The baseline operating condition is selected as a 50 mM / 1 mM sodium chloride solution, and the absolute value of the surface charge density of both the anion and cation nanochannels is 0.01 C / m. 2All nanochannels have a length of 1000 nm, a cation nanochannel radius of 8 nm, and an anion nanochannel radius of 4 nm. With the low-concentration side concentration fixed, the concentration ratios for optimized operating conditions 3 and 4 are 75 and 100, respectively. Table 2 shows that changes in the concentration ratio affect both power and loss factor. By appropriately adjusting the concentration ratio, coordinated optimization of power and loss factors can be achieved, increasing power from 0.098 to 0.134 pW and decreasing the loss factor from 3.09% to 2.06%. In summary, the ion salinity gradient power generation unit based on common parameters has been optimized.

[0050] Table 2 Optimization of power generation unit based on concentration ratio ion salt difference

[0051]

[0052] Industrial applicability

[0053] The evaluation and optimization method for ion salt difference power generation units based on loss factors described in this invention can be manufactured and used in the power generation field.

[0054] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0055] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A method for evaluating and optimizing an ion salt difference power generation unit based on a loss factor, characterized in that, It includes, Step S100: Construct a periodic ion salt difference power generation unit, and measure the input parameters and characterize the output performance of the ion salt difference power generation unit; Step S200: Characterize the output performance and classify the input parameters of the single anion-selective membrane system and the single cation-selective membrane system corresponding to the ion salt difference power generation unit; Step S300: Perform circuit analysis on the ion salt difference power generation unit and the single anion-selective membrane system and cation-selective membrane system, and calculate the power loss factor of the ion salt difference power generation unit to evaluate the power loss of the ion salt difference power generation unit. Step S400: Optimize the output performance of the ion salt difference power generation unit based on the power loss factor. According to the characteristics of the loss factor, determine the relative magnitude of the permeation current of the single anion-selective membrane system and the cation-selective membrane system, and optimize the one with the smaller permeation current. Step S500: Based on the optimization of channel parameters, prioritize changing the surface charge density of the system with the smaller permeation current, and then change the channel length and radius; based on the optimization of ion types, prioritize replacing the ions corresponding to the system with the smaller permeation current to improve the ion diffusion coefficient; based on the optimization of common parameters, changes in common parameters will cause changes in the permeation current of both the single anion-selective membrane system and the cation-selective membrane system, adjust the amplitude of the common parameters to make the permeation current of the two consistent. Step 600: Based on the optimized single anion-selective membrane system and cation-selective membrane system, construct the corresponding ion salt gradient power generation unit for application in large-scale ion salt gradient power generation systems.

2. The method according to claim 1, characterized in that, A periodic ion salt gradient power generation unit includes a low-salt chamber, an anion-selective membrane, a high-salt chamber, a cation-selective membrane, and a low-salt chamber; a single anion-selective membrane system includes a low-salt chamber, an anion-selective membrane, and a high-salt chamber in the ion salt gradient power generation unit; and a single cation-selective membrane system includes a high-salt chamber, a cation-selective membrane, and a low-salt chamber in the ion salt gradient power generation unit.

3. The method according to claim 1, characterized in that, Output performance includes the current-voltage characteristic curve, permeation current, diffusion potential, and maximum power. The permeation current, diffusion potential, and maximum power of the ion salt gradient power generation unit are expressed as follows: I 0, E 0, P 0. The permeation current, diffusion potential, and maximum power of a single anion-selective membrane system are expressed as follows: I a , E a , P a The permeation current, diffusion potential, and maximum power of a single cation-selective membrane system are expressed as follows: I c , E c , P c .

4. The method according to claim 1, characterized in that, Input parameters are categorized into channel parameters, ion types, and common parameters. Channel parameters include the surface charge density of the anion-selective membrane. σ a ,length L a ,radius R a Surface charge density of cation-selective membranes σ c ,length L c ,radius R c Ion types include anion diffusion coefficient D a cation diffusion coefficient D c Common parameters include high concentration of C h low concentration C l High concentration side temperature T h Low concentration side temperature T l .

5. The method according to claim 1, characterized in that, The circuit analysis of the ion salt difference power generation unit, the single anion-selective membrane system, and the cation-selective membrane system applies the principle of current conservation. The potentials of the single anion-selective membrane system and the cation-selective membrane system under the same current are connected in series, and the total potential is equal to the potential of the ion salt difference power generation unit.

6. The method according to claim 3, characterized in that, Power loss factor Lf The power loss factor measures the power loss of an ion salt gradient power generation unit compared to single anion-selective membrane systems and cation-selective membrane systems. Lf Greater than or equal to zero, equality condition I a = I c or E a = 0 or E c = 0, meaning the closer the permeation current or the smaller the diffusion potential of a single anion-selective membrane system and a cation-selective membrane system, the lower the power loss factor. Lf The smaller, 。 7. The method according to claim 1, characterized in that, The optimization strategy for the ion salt difference power generation unit is to make the permeation current of the single anion-selective membrane system and the cation-selective membrane system as close as possible, while ensuring that the diffusion potential does not decrease, so as to achieve a low loss factor.

8. The method according to claim 1, characterized in that, By optimizing channel parameters, the magnitude of the permeation current in one system can be changed without affecting the permeation current in another system.

9. The method according to claim 1, characterized in that, Changes in ion types and common parameters alter the permeation current of both single anion-selective membrane systems and single cation-selective membrane systems.

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