Electrochemical device with efficient ion exchange membrane

Abstract

To provide a system and a process capable of reducing both energy consumption and overall cost for desalination using an electrochemical battery.SOLUTION: An electrochemical device includes a first type of membrane arranged between a first reservoir and a second reservoir containing an input solution, a second type of membrane different from the first type is arranged between a first redox-active electrolyte chamber and the first reservoir, and a second redox-active electrolyte chamber and the second reservoir. The first type of membrane and one of the second type of membranes form a membrane pair, and the pair has an area specific resistance below y=5065.3x3-1331.1x2+90.035x+39 Ohm cm2 when the pair is equilibrated in an electrolyte and for at least part of a range where 0<x<0.4 and x is the mass fraction of salt in the electrolyte.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] This disclosure relates, in general, to a desalination and salting system in which energy storage is optionally possible, a method for operating the same, and an electrochemical battery for use in the system. [Background technology]

[0002] The deployment of grid-scale electrical energy storage will enable deeper penetration of energy generation from intermittently available renewables. While today's batteries offer load-shifting capabilities, their high price still restrains widespread integration of storage, potentially slowing the adoption of renewables. At the same time, rising water scarcity is necessitating the installation of energy-intensive desalination technologies to meet increasing water demands.

[0003] For example, as a result of climate change and the rapid pace of global population growth, pressure on the supply of freshwater continues to increase. In communities located in areas with limited access to freshwater, such as the Persian Gulf and other desert regions, freshwater is produced through the desalination of seawater. In these areas, this process is highly energy-intensive, whether driven hydrodynamically (e.g., via reverse osmosis, RO), thermally (e.g., via flash distillation), or electrochemically (e.g., via electrodialysis). Elsewhere, all of these methods are routinely used to treat wastewater contaminated by industrial activities.

[0004] Additionally, the price of power generation from renewable sources is falling rapidly, mainly driven by technological improvements in solar and wind power generation. As recently as October 2017, Saudi Arabia received bids to supply electricity from solar power at a price of $17.90 per MWh for a 300 MW plant. The availability of inexpensive electricity presents an opportunity for electrochemical methods of water desalination (or treatment) to play a greater role in meeting the increasing demand for water. What is described herein are systems and processes that reduce both the energy consumption and overall cost of desalination using an electrochemical battery.

Summary of the Invention

[0005] The embodiments described herein are directed to an electrochemical device. The device includes a first reservoir having an input and an output, wherein the concentration of the input solution increases to a threshold concentration during the operating mode, and a second reservoir having an input and an output, wherein the concentration of the input solution decreases during the operating mode. The first redox-active electrolyte chamber includes a first solution of a redox-active electrolyte material and at least one first electrode configured to have a reversible redox reaction with the first redox-active electrolyte material, and drives at least one ion into the input solution in the first reservoir. The second redox-active electrolyte chamber includes a second solution of a redox-active electrolyte material and at least one second electrode configured to have a reversible redox reaction with the second redox-active electrolyte material, and receives at least one ion from the input solution in the second reservoir. A first type of membrane is disposed between the first reservoir and the second reservoir, and a second type of membrane different from the first type is disposed between the first redox-active electrolyte chamber and the first reservoir and between the second redox-active electrolyte chamber and the second reservoir. One of the first type of membrane and the second type of membrane forms a membrane pair, and the pair is balanced in the electrolyte and for at least a portion in the range of 0 < x < 0.4, where x is the mass fraction of salt in the electrolyte, and the pair is y = 5065.3x3 -1331.1x 2 +90.035x + 39 ohm-cm 2 has an area resistivity less than

[0006] A further embodiment is directed to an electrochemical device. The device includes a first reservoir having an input and an output, wherein the concentration of the input solution increases to a threshold concentration during an operating mode, a second reservoir having an input and an output, wherein the concentration of the input solution decreases during the operating mode. The first redox-active electrolyte chamber includes a first solution of a redox-active electrolyte material and at least one first electrode configured to have a reversible redox reaction with the first redox-active electrolyte material, and drives at least one ion into the input solution within the first reservoir. The second redox-active electrolyte chamber includes a second solution of a redox-active electrolyte material and at least one second electrode configured to have a reversible redox reaction with the second redox-active electrolyte material, and accepts at least one ion from the input solution within the second reservoir. A first type of membrane is disposed between the first reservoir and the second reservoir, and a second type of membrane different from the first type is disposed between the first redox-active electrolyte chamber and the first reservoir and between the second redox-active electrolyte chamber and the second reservoir. The device has a concentration efficiency greater than -0.0800226x 4 +0.0641781x 3 -0.0156863x 2 +0.0008604x + 0.00007 g / J for at least a portion of the range 0 < x < 0.35, where x is the average mass fraction of salt in the electrolyte.

[0007] Additional embodiments relate to an electrochemical device. The device comprises a first reservoir having an input and an output, wherein the concentration of the input solution increases to a threshold concentration during the operating mode; and a second reservoir having an input and an output, wherein the concentration of the input solution decreases during the operating mode. The first redox active electrolyte chamber includes a first solution of a redox active electrolyte material and at least one first electrode configured to have a reversible redox reaction with the first redox active electrolyte material, driving at least one ion into the input solution in the first reservoir. The second redox active electrolyte chamber includes a second solution of a redox active electrolyte material and at least one second electrode configured to have a reversible redox reaction with the second redox active electrolyte material, receiving at least one ion from the input solution in the second reservoir. A first type of membrane is placed between a first reservoir and a second reservoir, and a second type of membrane, different from the first type, is placed between a first redox active electrolyte chamber and a first reservoir, and between a second redox active electrolyte chamber and a second reservoir. The combination of the first type of membrane and one of the second type of membrane is configured to equilibrate the solution in the first reservoir with the solution in the second reservoir at a concentration difference of 1% salt / amp of the current applied to at least one first and second electrode.

[0008] The above summary is not intended to describe each of the disclosed embodiments or all practices of this disclosure. The drawings and the following detailed description illustrate exemplary embodiments more specifically. [Brief explanation of the drawing]

[0009] The following discussion refers to the following figures, and the same reference numbers may be used to identify similar / identical components in multiple figures. However, the use of numbers to refer to components in a given figure is not intended to limit components in other figures labeled with the same number. The drawings are not necessarily to scale. [Figure 1A]This is a schematic diagram of an electrodialysis system having a positively charged redox shuttle according to a specific embodiment. [Figure 1B] This is a schematic diagram of an electrodialysis system having a negatively charged redox shuttle according to a specific embodiment. [Figure 2A] This is a schematic diagram of a charging cycle for an electrodialysis battery having a pair of positively charged reactants, according to a specific embodiment. [Figure 2B] This is a schematic diagram of the discharge cycle of the electrodialysis battery shown in Figure 2A, according to a specific embodiment. [Figure 3A] This is a schematic diagram of an energy storage system coupled to a power supply unit and power grid, according to a specific embodiment. [Figure 3B] This is a schematic diagram of an energy storage system coupled to a power supply unit and power grid, according to a specific embodiment. [Figure 4A] This is a graph of the open-circuit potential as a function of the cell's charge state, according to a specific embodiment. [Figure 4B] This is a graph of each reservoir salt as a function of the cell's charge state, according to a specific embodiment. [Figure 5A] This shows the discharge operation modes of an electrodialysis battery having four chambers according to a specific embodiment. [Figure 5B] This shows a charging operation mode for an electrodialysis battery having four chambers, according to a specific embodiment. [Figure 5C] This shows the electrodialysis operating modes of an electrodialysis battery having four chambers according to a specific embodiment. [Figure 5D] This shows a dehumidification operation mode of an electrodialysis battery having four chambers according to a specific embodiment. [Figure 6A] This graph shows the performance metrics of an electrodialysis system with four chambers that utilize ferrocyanide as a redox shuttle. [Figure 6B]This graph shows the performance metrics of an electrodialysis system with four chambers that utilize ferrocyanide as a redox shuttle. [Figure 6C] Figures 6A and 6B show graphs illustrating the salt concentration as a function of the charge that has passed through an electrodialysis system with four chambers. [Figure 6D] Figures 6A and 6B show graphs illustrating the salt concentration as a function of time in an electrodialysis system with four chambers. [Figure 7A] Figure 5 is a graph comparing the operating potential and specific energy consumption of a conventional redox-assisted electrodialysis system in a cell stack. [Figure 7B] This graph compares the relative specific energy consumption for a conventional redox-assisted electrodialysis system for a fluctuating number of salting / desalting chambers per anode and cathode. [Figure 8A] This graph shows the system cost, revenue, and performance metrics of an electrodialysis battery with four chambers, using traditional pricing for water and electricity. [Figure 8B] This graph shows the system cost, revenue, and performance metrics of an electrodialysis battery with four chambers, using traditional pricing for water and electricity. [Figure 8C] This graph shows the system cost, revenue, and performance metrics of an electrodialysis battery with four chambers, using traditional pricing for water and electricity. [Figure 8D] This graph shows the system cost, revenue, and performance metrics of an electrodialysis battery with four chambers, using traditional pricing for water and electricity. [Figure 9A] This graph shows the system cost, revenue, and performance metrics of an electrodialysis battery with four chambers that utilizes optimal water and electricity pricing in the Persian Gulf region. [Figure 9B]This graph shows the system cost, revenue, and performance metrics of an electrodialysis battery with four chambers that utilizes optimal water and electricity pricing in the Persian Gulf region. [Figure 9C] This graph shows the system cost, revenue, and performance metrics of an electrodialysis battery with four chambers that utilizes optimal water and electricity pricing in the Persian Gulf region. [Figure 9D] This graph shows the system cost, revenue, and performance metrics of an electrodialysis battery with four chambers that utilizes optimal water and electricity pricing in the Persian Gulf region. [Figure 10] This is a graph of component costs for a cell having four chambers according to a specific embodiment. [Figure 11] This is a flowchart of the method according to a specific embodiment. [Figure 12] This is a flowchart of the method according to a specific embodiment. [Figure 13] This is a flowchart of the method according to a specific embodiment. [Figure 14A] This graph shows performance metrics for an electrodialysis system with four chambers that utilize BTMAP-Fc as a redox shuttle. [Figure 14B] This graph shows performance metrics for an electrodialysis system with four chambers that utilize BTMAP-Fc as a redox shuttle. [Figure 14C] Figures 14A and 14B show graphs illustrating salt concentration as a function of charge passed through an electrodialysis system with four chambers. [Figure 14D] Figures 14A and 14B show graphs illustrating salt concentration as a function of time in an electrodialysis system with four chambers. [Figure 15] This graph shows the concentration efficiency of membrane pairs in various embodiments. [Figure 16] This graph shows the area resistivity of film pairs in various embodiments. [Figure 17] This graph shows the current efficiency of film pairs in various embodiments. [Figure 18] This graph shows the electroosmotic transport coefficients of membrane pairs in various embodiments. [Modes for carrying out the invention]

[0010] This disclosure relates, in general terms, to electrochemical desalination systems and optional, corresponding simultaneous energy storage. Current research efforts in grid storage currently benefit from a single approach to minimize cost per wkh, with a cost target of $125 / kWh by the U.S. Department of Energy by 2022. An alternative strategy is to increase the revenue associated with each kWh of storage, which is not available in conventional energy storage technologies. However, the electrochemical batteries described herein are capable of this alternative because they generate a valuable secondary product, desalination water, during filling and discharging. Since aqueous flow batteries share many capital requirements (e.g., pumps, membranes, piping) with electrochemical desalination technologies, a system combining the two may result in significant capital cost savings compared to two separate systems. The revenue from desalination water leverages process enhancements that offset additional capital costs and break below the dollar / kWh barrier encountered by conventional energy storage technologies. Electrochemical approaches to desalination have the potential to easily scale modulus and lamp production while maintaining high energy efficiency and the ability to handle high salinity supplies.

[0011] The most advanced technology in electrochemical water desalination is electrodialysis; however, it consumes relatively more energy for salt removal than other desalination techniques such as reverse osmosis (e.g., 0.06-0.08 kWh / kg NaCl) (e.g., approximately 0.26-0.30 kWh / kg NaCl), but less energy than thermal techniques such as vapor compression (e.g., 0.6-1.0 kWh / kg NaCl). Capacitive deionization also uses electrical energy, but this is also energy-intensive at approximately 0.22 kWh / kg NaCl, and is best suited for removing trace amounts of dissolved salt from water because the electrodes are solid by definition. Unlike reverse osmosis, electrodialysis is a technique that can be used to treat saline water with any salt content, but its use has been limited due to its high specific energy consumption for salt removal.

[0012] Energy consumption in electrodialysis is proportional to the applied voltage, and reducing (or minimizing) the voltage to be applied to the cell reduces the specific energy consumption of the electrodialysis stack. In conventional electrodialysis, ions are driven from or into seawater by a Faraday reaction at the anode and cathode. In most cases, the Faraday reaction is simply water splitting; that is, water is oxidized to oxygen at the anode and reduced to hydrogen at the cathode. This creates a charge imbalance in the electrodes, which are balanced by the movement of ions through strategically placed ion-selective membranes. However, water splitting involves an energy penalty because energy is required to do so. This problem is exacerbated by the fact that significant overpotentials are associated with both the oxidation and reduction of water. Furthermore, the oxygen and chlorine gases generated at the anode are highly destructive, necessitating the use of platinum / iridium plated electrodes.

[0013] In California alone, solar power can replace fossil fuel sources for electricity generation in the state (0.40 times, 41% of all sources), and when paired with desalination batteries for storage as described herein, it can bring an additional 0.63 times of solar power online, based on a 64% cost-optimized round-trip energy efficiency. At the same time, desalination batteries will provide water resources equivalent to 30% of the state's consumption.

[0014] As described herein, the electrochemical cell is designed to perform electrodialysis in an energy-efficient manner by circulating redox-active species that dissolve in water and return from the anode to the cathode. The redox-active species have rapid dynamics for reduction or oxidation, which significantly reduces the high operating voltage required for conventional electrodialysis, where water splitting drives intermembrane salt transport, such as in an ion-selective membrane. Reducing the operating voltage reduces the specific energy consumption, as specific energy consumption is proportional to the operating voltage. The system can further be reversibly adapted to coupled electrical energy storage by pairing two separate redox bonds at the anode and cathode instead of a single redox shuttle circulating around both.

[0015] In certain embodiments of lower potential electrodialysis systems with lower energy efficiency, a redox support dissolved in water is reduced at the cathode, then shuttled to the anode, where it is reoxidized and subsequently redelivered to the cathode to complete the cycle. Referring to Figures 1A and 1B, an electrochemical cell 100 providing energy-efficient electrodialysis according to such embodiments is shown. The cell 100 consists of four chambers 102, 104, 106, and 108 in series. Each chamber is separated from its neighbors by a suitable membrane 110, 112, 114 (Figure 1A) or 116, 118, 120 (Figure 1B). Two central chambers 104 and 106 contain a salting stream 130 and a desalting stream 132, and two external chambers 102 and 108 contain a cathode and anode (Figure 1A) or anode and cathode (Figure 1B), respectively.

[0016] The membrane may be an ion-selective membrane, such as a cation exchange membrane or an anion exchange membrane, depending on the cell design. If the redox shuttle has a sufficiently high molecular weight (e.g., essentially a dendrimer or polymer), the membrane may be a microporous membrane. The membrane may also incorporate several ion-selective elements and several microporous elements within the same membrane. In certain embodiments, the membrane may also be a composite membrane.

[0017] For example, Figure 1A shows a redox-assisted electrodialysis system having a positively charged redox shuttle (i.e., 1,1'-bis(trimethylammoniopropyl)ferrocene dichloride (BTMAP-Fc)). The movement of the redox shuttle from anode 108 to cathode 102 is indicated by arrow 128, and the movement from cathode 102 to anode 108 is indicated by arrow 126. The cathode chamber 102 and the salting chamber 104 are separated by an anion exchange membrane 110, and the anode chamber 108 and the desalting chamber 106 are also separated by an anion exchange membrane 114. Membranes 110 and 114 do not necessarily have to contain the same material or have similar dimensions. The salting chamber 104 is also separated from the desalting chamber 106 by a cation exchange membrane 112. As can be seen, the chloride and sodium ions cross membranes 110 and 112 and enter the salting stream 130 in chamber 104, but cross membranes 114 and 112 and exit the desalting stream 132 in chamber 106.

[0018] The design of cell 100 is modified as shown in Figure 1B using a negatively charged redox shuttle (e.g., ferrocyanide / ferricyanide (Fe(CN))). Here, the movement of the redox shuttle from cathode 108 to anode 102 is indicated by arrow 128, and the movement from anode 102 to cathode 108 is indicated by arrow 126. The anode chamber 102 and the salting chamber 104 are separated by a cation exchange membrane 120, and the cathode chamber 108 and the desalting chamber 106 are also separated by a cation exchange membrane 116. However, membranes 120 and 116 do not necessarily have to contain the same material or have similar dimensions. The salting chamber 104 is also separated from the desalting chamber 106 by an anion exchange membrane 118. As can be seen, the chloride and sodium ions cross membranes 118 and 120 and enter the salting stream 130 in chamber 104, but cross membranes 116 and 118 and exit the desalting stream 132 in chamber 106.

[0019] In various embodiments, any number of pairs of alternating salting and desalination chambers can be used. However, water splitting may begin to occur in a higher number of chambers when the applied voltage exceeds 1.26V. Solid redox supports can be used in various embodiments, but because solid redox active materials cannot be easily transported from one side of the electrochemical cell to the other, a large amount of support and frequent switching between salting and desalination streams are required.

[0020] The energy efficiency of cell 100 is achieved through the selection of the redox support / shuttle. An effective redox support should have as many of the following characteristics as possible. For example, the redox support should be chemically stable in both oxidized and reduced forms, highly water-soluble in both oxidized and reduced forms, and not oxygen-sensitive in both oxidized and reduced forms. The support should not be proton-bonded, should have rapid redox dynamics, and should be chemically compatible with any components present in the water being treated. Furthermore, the support should have low permeability through an ion-selective membrane and be non-toxic.

[0021] The most common redox carriers reported currently are Fe 2+ / Fe 3+ , iron-containing compounds including ferrocyanide / ferricyanide (Fe(CN)) bonds, and Fe(II)-EDTA / Fe(III)-EDTA. All three are considered for reverse electrodialysis, i.e., the generation of electricity from a salinity gradient instead of the consumption of electricity to generate a salinity gradient. The use of redox bonds for conventional electrodialysis has not yet been reported. Unfortunately, Fe 3+ ions are only soluble at low pH, form insoluble oxides or hydroxides at neutral pH, Fe(CN) forms highly insoluble Prussian blue type compounds when in contact with many transition metals (especially iron), and the Fe-EDTA complex exhibits limited electrochemical stability.

[0022] Systems having Fe(CN) as a redox carrier have been demonstrated to be successful in laboratories having only NaCl as simulated seawater, but the ubiquitous presence of calcium and iron in seawater (typically at levels of 400 parts per million (ppm) and 1 - 3 parts per billion (ppb)) causes rapid membrane fouling when these ions cross into the reservoir. They form insoluble precipitates of potassium calcium and iron when in contact with Fe(CN). Further, even under neutral to slightly acidic conditions generated at the anode, it causes the release of highly toxic hydrogen cyanide.

[0023] However, ferrocene derivatives having all of the attributes listed above can be a suitable redox carrier, e.g., BTMAP-Fc. Compare this with various iron-containing redox bonds in Table 1 below.

[0024]

Table 1

[0025] The four-chamber cell design discussed above in relation to Figures 1A and 1B can also be adapted for use as an energy storage device (i.e., an electrodialysis battery). When the cell uses a small number of salting / desalting chamber pairs (e.g., one pair), performance is improved compared to conventional electrodialysis, as shown in Figure 7B. A smaller number of chamber pairs is also advantageous for energy storage applications where the preferred operating current density is also lower than that for electrodialysis. The above cell is adapted for energy storage by using two different redox-active reactants as separate anolites and catholites instead of shutting the same compound between the anode and cathode. Unlike the three-chamber cell design (e.g., U.S. Patents 9,340,436, 9,670,077, and 9,673,472, each of which is incorporated herein by reference), the four-chamber design is capable of continuously generating desalinated water during operation, instead of only half the time. Furthermore, in the event of crossover, the design with four chambers avoids the problem of insoluble solid precipitates.

[0026] An embodiment of an electrodialysis battery having four chambers is shown in Figures 2A and 2B. The desalination battery is a flow battery having multiple chambers. The reduction of anolite and oxidation of catholite during a half-cycle of charging are carried out by Na through an appropriate ion-selective membrane, either inside or outside the intervening chamber that holds seawater. + and Cl - Ions are moved. The reverse process occurs during a half-cycle of discharge. At every point in the cycle, one of the water chambers experiences a net inflow of salt, while the other sees a net outflow. The energy required to influence desalination is simply the difference between the energy input during charging and the energy recovered during discharge.

[0027] Figure 2A shows a charging cycle of a battery having four chambers using positively charged reactant pairs. The battery includes four chambers 202, 204, 206, and 208, and three membranes 210, 212, and 214. During the charging cycle, the salting stream 230 is located in chamber 204 between the catholite chamber 202 and chamber 206, which contains the desalting stream 232. The anolite chamber 208 is separated from chamber 206 and the desalting stream 232 by an anion exchange membrane 214, while the catholite chamber 202 is separated from chamber 204 and the salting stream 230 by another anion exchange membrane 210. As discussed above, membranes 210 and 214 do not necessarily have to contain the same material or have similar dimensions. The salting chamber 204 is also separated from the desalting chamber 206 by a cation exchange membrane 212. During the charging cycle, chloride and sodium ions enter chamber 204, which forms a salting stream 230 across membranes 210 and 212, but exit chamber 206, which forms a desalting stream 232 across membranes 214 and 212.

[0028] Figure 2B shows the same battery as in Figure 2A during a discharge cycle. Thus, the chloride and sodium ions exit chamber 204, which forms a desalting stream 232 across membranes 210 and 212, but enter chamber 206, which forms a salting stream 230 across membranes 214 and 212. In particular, if the reactants are negatively charged, the membranes are inverted. That is, membranes 210 and 214 are cation exchange membranes, and membrane 212 is an anion exchange membrane. As mentioned above, membranes 210 and 214 do not necessarily have to contain the same material or have similar dimensions if they are cation exchange membranes.

[0029] A wide variety of membrane types and materials can suitably function as membranes 210, 212, and 214 in the embodiments of the electrodialysis battery described herein, but ion-exchange membranes exhibit properties that promote improved battery performance, such as increased efficiency of material transfer across the membrane. Ion-exchange membranes contain chemically or physically immobilized ions and counterions of opposite charge to the immobilized ions, which interact with the charge of the immobilized ions via Coulomb forces. The immobilized or fixed charge is charge-equalized by the oppositely charged counterions to maintain the charge neutrons within the membrane. In certain embodiments, the charge can be immobilized on the membrane by covalent bonding with entangled or crosslinked polymers (e.g., polymer molecules having a molecular weight greater than 1,000 kg / mol or polymer molecules having a molecular weight greater than 5,000 kg / mol). In other embodiments, the charge can be immobilized by covalent bonding with particles dispersed in the membrane, such as particles having a minimum particle size greater than 1 nm.

[0030] The immobilized ions determine the type and function of the ion exchange membrane. An anion exchange membrane (AEM) contains cationic fixed charges (i.e., the immobilized charge is net positive). A cation exchange membrane (CEM) contains anionic fixed charges (i.e., the immobilized charge is net negative). The co-ions within the membrane are non-immobilized ions that share the same charge sign as most of the immobilized charges (e.g., in an AEM, the co-ions have a positive charge). The ion exchange membrane can be selective for the transport of counterions (i.e., the flux of counterions through the membrane is greater than the flux of co-ions). When the membrane is equilibrated with an electrolyte solution, cations, anions, and the solvent (e.g., water) from the electrolyte solution can be incorporated into the membrane from the co-ions. The efficiency of any combination of membranes 210, 212, 214 is affected by one or more of the following phenomena.

[0031] Membrane efficiency can be referred to as an evaluation of the performance of a membrane pair (e.g., any two of membranes 210, 212, 214). An efficient membrane exhibits a high flux of counterion species with respect to the driving force or combination of driving forces acting on the counterions. Examples of driving forces are spatial differences in electrochemical potential, concentration, or pressure across the membrane. Additionally, an efficient membrane exhibits high selectivity for counterion transport. The ratio of counterion flux to the flux of other species such as solvent, water, or co-ions is high, but the ratio depends on the type of counterion. For a pair of membranes including a CEM and an AEM, the high-flux counterions are different for the two membrane types.

[0032] The ion current through the pair of membranes is limited by the area-specific resistance (ASR). For various embodiments described herein, an efficient membrane pair of one CEM and one AEM has, for all or part of the range 0 < x < 0.4, where x is the mass fraction of salt in the electrolyte, y = 327.93x 2 - 84.743x + 19 ohm cm 2 less than, or y = 2528.5x 3 - 493.61x2 +1.7501x + 19 ohm·cm 2 less than, or y = 5065.3x 3 -1331.1x 2 +90.035x + 39 ohm·cm 2 may have an ASR less than this.

[0033] Figure 16 shows the ASR of different pairs of membranes. An ASR below line 1616 is good or shows acceptable performance, and an ASR below line 1614 shows improved performance compared to that of line 1616. However, an ASR below line 1612 shows the most improved performance in the electrochemical devices described herein. For example, the data for the membrane pairs shown as 1604 and 1610 are considered to have good performance, the performance for the pair shown at 1606 is better in comparison, and the performance shown for pairs 1602 and 1608 is the most improved performance in the illustrated group.

[0034] Another factor involves coulombics, or current efficiency. Coulombic efficiency describes the charge efficiency with which ions move through the membrane. For example, coulombic efficiency is reduced by the transport of "wrong" types of ions through the membrane in the opposite direction, such as cations transported through an AEM. For the various embodiments described herein, an efficient membrane pair of one CEM and one AEM has a coulombic efficiency greater than 70%. This may also be determined by a coulombic efficiency greater than -170x + 89 (%) or -150x + 97 (%), where for all or part of the range 0 < x < 0.4, x is the mass fraction of salt in the electrolyte. In various embodiments, the salt is LiCl. In various embodiments, the solution is aqueous, and in further embodiments, the solution contains more than 60% water.

[0035] Figure 17 shows the current efficiencies of different pairs of membranes. Current efficiencies above line 1714 indicate good or acceptable performance, and current efficiencies above line 1712 indicate improved performance in the electrochemical devices described herein. Line 1714 represents the performance line -170x + 89 (%), and line 1712 represents the aforementioned performance line -150x + 97 (%). For example, the data for the membrane pair indicated as 1710 may not provide acceptable performance at all salt mass fractions within a given range. The membrane pairs indicated as 1702, 1704, and 1706 show good performance across a range of salt mass fractions, and the membrane pair indicated as 1708 provides consistently improved performance across a range of salt mass fractions.

[0036] Further phenomena that affect membrane efficiency are electroosmotic and hydrodynamic currents. When ions move across the membrane due to a driving force acting on them, such as an applied voltage or concentration gradient, the ions pull water along with them. This phenomenon is related to the electroosmotic transport coefficient t w It is expressed as t, which is defined as the molar ratio of transported water to moles of transported salt. To improve the efficiency of a membrane pair of one CEM and one AEM, electroosmosis is performed for all or part of the range 0 ≤ x ≤ 0.4, where x is the solute mass fraction in the input solution, and t w = -39x + 16 less than, t w = -39x + 15 or less, or t w It should be low, such as less than -39x + 14. In certain embodiments, the salt or solute is LiCl. In certain embodiments, the solvent is water, and embodiments of LiCl and water may be combined or not.

[0037] Figure 18 shows the electroosmotic transport coefficients of different pairs of membranes. Coefficient t below line 1816. w It exhibits good or acceptable performance, and the coefficient t is below line 1814. w It shows improved performance compared to line 1816. However, it is inferior to line 1812. wThe most improved performance in the electrochemical devices described herein is shown. For example, the data for the membrane pair shown as 1602 may not be acceptable, and the membrane pair shown as 1806 may provide acceptable performance at a particular salt mass fraction. The performance of the membrane shown as 1804 is better at lower salt mass fractions. The performance of the membrane pair shown as 1810 provides good or better performance over a range of salt mass fractions, while the membrane pair shown as 1808 provides consistently acceptable performance over that range of salt mass fractions. w To provide.

[0038] Similarly, when water moves across a membrane due to a driving force acting on the water, such as a difference in chemical potential corresponding to a difference in concentration, water can pull ions. This is called hydrodynamic current and can be expressed as a ratio defined as the hydrodynamic ratio of moles of ions per mole of water. In the various embodiments described herein, a membrane pair of one CEM and one AEM has a hydrodynamic current ratio of t w It is considered efficient when it is greater than or equal to the reciprocal of the value, for example, 50% or more.

[0039] In addition to the phenomena described above, the properties of specific membrane types affect the efficiency of the membrane and, therefore, the efficiency of the entire electrodialysis battery system, which may include a large number of individual membranes and membrane types. The following properties are described for individual membranes that may be implemented as one of the membranes in the disclosed embodiments.

[0040] High counterion selectivity leads to improved membrane efficiency, but as the concentration of the co-ion increases, the membrane selectivity and Coulombic efficiency generally decrease. As discussed above, the co-ion is a free ion in the membrane having the same charge sign as the immobilized charge in the membrane, and a decrease in the co-ion concentration results in improved membrane efficiency. The co-ion concentration can be defined in various ways, such as the number of moles of co-ion per volume of the membrane swollen in the electrolyte, the number of moles of co-ion per dry mass of the membrane, the number of moles of co-ion per dry mass or dry volume of the membrane, or the number of moles of co-ion per volume of the solvent (e.g., water) in the swollen membrane. A closely related property is the salt partition coefficient. The quantitative property here is defined as the number of moles of co-ion per liter of the solvent (e.g., water) in the membrane. For the various embodiments described herein, an efficient membrane has a co-ion concentration below the molar salt concentration of the electrolyte solution when the membrane is equilibrated in the electrolyte solution. This may alternatively be defined as less than 21x - 0.87 mol / L, where x is the mass fraction of the salt in the electrolyte, for all or part of the range 0 < x < 0.4. In various embodiments, the salt is LiCl, and in various embodiments, the solvent is water. These various embodiments may or may not be combined.

[0041] Similarly, a high fixed charge concentration C fix improves the selectivity of the membrane for counterion transport. C fix is the equivalent of the fixed charge per volume of water in the membrane after equilibration with the electrolyte solution and is similar to the ion exchange capacity of the membrane, which is the number of moles of counterions per dry mass of the membrane. C fix depends on both the ion exchange capacity in the electrolyte solution and the uptake of the solvent (e.g., water). An increase in only the ion exchange capacity does not account for the accompanying increase in the uptake of the solvent (e.g., water) that can reduce the volume density of the fixed charge and increase the solvent penetration. For the various embodiments described herein, an efficient membrane has a C fix of at least 5 charge equivalents per liter when equilibrated in the electrolyte at a salt mass fraction of less than 0.4. In various embodiments, the salt is LiCl.

[0042] Additional properties relate to the relationship between the membrane and the solvent (e.g., water). For example, osmosis is the spontaneous and non-electrically driven transport of solvent (e.g., water) molecules across a membrane from a solution of low salt concentration to a solution of high salt concentration. For the various embodiments described herein, an efficient membrane is equilibrated in an electrolyte for at least a portion of the range 0 < x < 0.4, where x is the mass fraction of salt in the electrolyte, and has an osmosis flux of less than -1x + 0.43 L / m 2 / h, or less than -0.48x + 0.205 L / m 2 / h. In various embodiments, the salt is LiCl. The degree of swelling refers to the amount of solvent (e.g., water) taken up by the membrane after equilibration with an electrolyte solution. There are many closely related properties such as water uptake, hydration number, water mass fraction, water volume fraction, water partition coefficient, and solvent / water permeability (i.e., the product of the diffusion coefficient of water and the water partition coefficient), but the degree of swelling is defined as the mass of solvent (e.g., water) in the electrolyte-equilibrated membrane per mass of the dry membrane. For the various embodiments described herein, an efficient membrane has a degree of swelling of less than 30% when equilibrated in an electrolyte, and the salt mass fraction is less than 0.4. In various embodiments, the electrolyte solution is LiCl salt in water. Further, the membrane thickness affects the transport distance and the area available for fixing ions. For the various embodiments described herein, an efficient membrane has a thickness of 150 micrometers or less, or 100 micrometers or less, or 75 micrometers or less, or 50 micrometers or less to reduce the ASR of the membrane.

[0043] Many of the above phenomena and properties are interrelated, such that changing one affects the others (e.g., changing the membrane thickness changes the ASR). For the various embodiments described herein, an efficient combination of membranes combines the above properties to control the above phenomena to achieve a high salt separation efficiency (e.g., for all or a portion of the range 0 < x < 0.354, equilibrated in an electrolyte, where x is the mass fraction of salt in the electrolyte, -0.0800226x 4 + 0.0641781x 3 - 0.015686x 2Greater than +0.0008604x+0.00007g / J, more preferably 0.2011769x 4 -0.1695373x 3 +0.0543430x 2 Greater than -0.0081837x + 0.00054 g / J (for example, the salt may be LiCl). For example, each membrane has a combination of low ASR, high salt selectivity (and correspondingly high Coulomb efficiency and low coion transport) and low water transport, which reduces and / or minimizes electroosmosis and osmosis.

[0044] One or more of the membranes 210, 212, and 214 may be homogeneous or heterogeneous. If homogeneous, the membrane may be reinforced or unreinforced. Reinforced homogeneous membranes contain a nonionic conductive structured macroscopic reinforcement, such as a mesh, woven mesh, cloth, fiber mat, or perforated sheet. If heterogeneous, the membrane has a ceramic dispersion or other phase of nonionic conductive material mixed with the ionomer within an ionomer matrix, but does not have a defined macroscopic shape such as a reinforced mesh. The presence of a heterogeneous phase has been shown to reduce electroosmotic water transport in conventional electrodialysis under certain conditions and is therefore suitable as an efficient membrane in the disclosed embodiments.

[0045] The nonionic conductive phase may be selected to be a hydrophobic polymer. Some examples of nonionic conductive phases that can be used are polyamides, polytetrafluoroethylene, polyether ether ketones, polyethylene, polyethylene terephthalate, polypropylene, fluoroelastomers, polyvinylidene fluoride, fluorinated ethylene propylene, polysulfones, polybenzimidazoles, perfluoroalkoxy polymers, polymers containing aromatic groups, polyolefins, aromatic polyamides (aramids), carbon fibers, graphene, graphene oxide and graphene-derived materials, clay, ceramic particles, polyoligosylsesquioxane, silica particles, titania particles, or alumina particles. -4 It may have an intrinsic ionic conductivity of less than S / cm.

[0046] For AEMs, the ion-conducting groups may be, for example, cationic groups, quaternary amines, cationic aromatic amines, imidazolium, pyridinium, guanidinium, piperadinium, diallyldimethylammonium, strong bases, and weak bases. For CEMs, the ion-conducting groups may be, for example, anionic groups, sulfonated polyether ether ketones, sulfonates, perfluorosulfonates, phosphonates, carboxylates, weak acids, and strong acids. These groups are typically bonded to larger polymer molecules via side chains or directly onto the polymer backbone. In some embodiments, they can be bonded to particles embedded in the film.

[0047] In certain embodiments, ionic groups are present in the membrane at levels such that the ion exchange capacity when the membrane is equilibrated in NaCl solution is less than 3 milliequivalents (meq / g), less than 2.5 meq / g, less than 2 meq / g, less than 1.75 meq / g, less than 1.5 meq / g, less than 1.25 meq / g, less than 1 meq / g, less than 0.75 meq / g, less than 0.5 meq / g, less than 0.4 meq / g, 0.4 to 3 meq / g, 1 to 2 meq / g, or 0.4 to 2 meq / g per gram of dry membrane.

[0048] The efficiency of the membranes, or the combination of membranes, is based on the amount of salt transported from the desalination stream to the salting stream. Ions are transported between these streams and from the anolite and catholite sources. In the embodiments shown in Figures 2A and 2B, the anolite is zinc and the catholite is BTMAP-Fc. In other embodiments, (ferrocenylmethyl)trimethylammonium chloride (FcNCl) can be used instead of BTMAP-Fc to increase the battery cell potential to approximately 1.41V.

[0049] Anolites and catholites are not limited to the embodiments described above. The redox active components of anolites and / or catholites may be in one or more of their oxidation states and may be aqueous solutions of any combination of the following, as ions or oxocations or oxoanions, and / or complexed with ligands. That is, titanium(III), titanium(IV), vanadium(II), vanadium(III), vanadium(IV), vanadium(V), chromium(II), chromium(III), chromium(VI), manganese(II), manganese(III), manganese(VI), manganese(VII), iron(II), iron(III), iron(VI), cobalt(II), cobalt(III), nickel(II), copper(I), copper(II), zinc(II), ruthenium(II), ruthenium(III), tin(II), tin(IV), cerium(III), cerium(IV), tungsten(IV), tungsten(V), osmium(II), The polymer incorporates osmium(III), lead(II), zincate, aluminate, chlorine, chloride, bromine, bromide, tribromide, iodine, iodide, triiodide, polyhalides, halide oxyanions, sulfides, polysulfides, sulfur oxyanions, ferrocyanides, ferricyanides, quinone derivatives, alloxazine derivatives, flavin derivatives, viologen derivatives, ferrocene derivatives, other metallocene derivatives, nitroxide radical derivatives, N,N-dialkyl-N-oxoammonium derivatives, nitronyl nitroxide radical derivatives, and / or any of the aforementioned complexed or covalent components.

[0050] The anolite and catholite may also comprise aqueous solutions of components of the pH buffer, which may be redox-active or inactive under typical operating conditions. In certain aqueous embodiments, the pH of the anolite and catholite matches the pH of the electrolyte in the central chamber, which may be, for example, nearly neutral (pH 5-9) for water desalination, acidic (pH 0-5) for treating acidic wastewater, or alkaline (pH 9-14) for treating alkaline wastewater. In some embodiments, it may be advantageous for the anolite pH to be slightly lower than that of the other chambers, such as when the anolite is zinc / zinc chloride. In further embodiments, the pH of each electrolyte in the system is substantially the same within the electrochemical cell. In further embodiments, the anolite, catholite, and water each have a pH between 3 and 10. Thus, the cell may include a pH monitoring and adjustment system for periodic and / or continuous pH monitoring and adjustment.

[0051] In further embodiments, electrodialysis battery cells, such as those shown in Figures 2A-2B, may be coupled to an energy storage system when designed as a flow battery. Flow batteries are attractive for energy grid storage because they allow for the separation of the battery's energy storage capacity from the power the battery can deliver. Aqueous flow batteries can be incorporated into electrochemical desalination systems because they share many common desalination capital requirements, such as pumps, piping, and cell stack design, which can be used for both desalination and energy storage. In principle, integrating electrical energy storage into desalination batteries further reduces costs by facilitating load shifting on the electrical grid, enabling electrical arbitrage, and / or allowing for a grace period for investment in transmission and distribution infrastructure. Desalination batteries with high cell potential would function as viable energy storage devices. By leveraging the revenue streams available to energy storage technology, the system can bear the desalination costs while simultaneously enabling increased adoption of renewable energy.

[0052] An example of an electrochemical desalination and salting system is shown in Figure 3. The described electrochemical desalination battery can operate in batch mode in certain embodiments or in continuous mode in other embodiments. In batch mode, a certain volume of water to be processed is supplied to (e.g., pushed into) the redox desalination system. A potential is applied to the electrodes, and ions are collected on the two electrodes until the salt concentration in the desalination water chamber falls below a set limit (e.g., parts per thousand, ppt) or 0.5 ppt). The water is then removed from the system. In continuous flow mode, water flows through the system, and the total residence time of a certain volume of water in each part of the system is sufficient to achieve the desired reduction in salt concentration. In certain embodiments, separate units with independently controlled electrodes are broken down into different stages and / or components to accommodate the decrease in salt concentration at each successive step in the desalination process. This can also accommodate the increase in salt concentration at each successive step in the salting process.

[0053] Referring to Figure 3, the energy storage system 300 includes an electrochemical desalination battery (EDB) unit 320a. A set of electrical switches (S1A, S1B, S2A, S2B, S3A, S3B) is provided within the energy storage system 300 to provide multi-configuration electrical connections that connect various nodes of the energy storage system 300 to a power supply unit PS (which may be either AC or DC according to the various embodiments described herein, whether as stated herein), a power (e.g., electric) grid, and / or other nodes of the energy storage system 300, and any combination thereof. As used herein, “electrical switch” refers to any device that can change the electrical connections of a circuit. The set of electrical switches (S1A, S1B, S2A, S2B, S3A, S3B) constitutes an operating mode control device that controls the operating modes of the energy storage system 300. As used herein, “operating mode control device” refers to any device that can be used to select an operating mode within a device configured to operate in two or more selective operating modes. The operating mode control device is configured to select between charging, discharging, and electrodialysis modes, in particular, based on the presence or absence of power demand from the power grid and / or the availability of external power provided by the power supply unit PS for the operation of the energy storage system 300.

[0054] The EDB unit 320a includes an anode (318, 308) and a cathode (316, 302) that can be embedded in various configurations. The anode (318, 308) may be receptive to a reversible redox reaction with a redox shuttle dissolved in water. The cathode (316, 302) may be receptive to a reversible redox reaction with a redox shuttle dissolved in water. The anode (318, 308) includes a negative electrode plate 318 and an electrolyte chamber 308 for containing an electrolyte solution (i.e., anolite). The cathode (316, 302) includes a positive electrode plate 316 and an electrolyte chamber 302 for containing an electrolyte solution (i.e., catholite). In certain embodiments, one or both of the cathode and anode include an intercalation material as an optional component for battery chemicals using intercalation. A cell with four chambers operates when both the anolite and the catholite have the same charge sign (i.e., both are positively charged, or both are negatively charged).

[0055] Two electrolyte chambers (e.g., water with a dissolved salt such as sodium chloride) 304 and 306 are provided between the anode (318, 308) and the cathode (316, 302) and contain solutions (e.g., water) to be salted and desalted, respectively.

[0056] In some embodiments, the separation distance between the anodes (318, 308) and cathodes (316, 302) decreases along the direction of water flow during operation. Desalination is driven by ion diffusion within the EDB unit 320a. As the salt concentration decreases within the desalination chamber, ions require greater effort to reach the electrodes (i.e., anodes and cathodes), effectively increasing the cell resistance. Reducing the electrode distance at a rate that keeps the internal resistance substantially constant leads to a substantially energy-efficient desalination process and an energy-efficient recharging during the salting process. In certain embodiments, the separation distance between the anodes (318, 308) and cathodes (316, 302) can be approximately inversely proportional to the ion concentration as the water being treated passes through water chambers 304, 306 in either a charging or discharging mode. In alternative embodiments, the separation distance between the anodes (318, 308) and cathodes (316, 302) remains substantially constant or increases.

[0057] The negative electrode plate 318 and the positive electrode plate 316 each contain a solid conductive material. In a given EDB, plates 318 and 316 may contain the same conductive material or different conductive materials. Each electrode plate 318 and 316 may contain one or more solid materials, namely zinc, iron, chromium, nickel, lead, titanium, copper, tin, silver, lead(IV) oxide, manganese(IV) oxide, sulfur, Prussian blue, Prussian blue derivatives, transition metal analogs of Persian blue, carbon fiber, graphite, carbon felt, conductive carbon black as a solid or aqueous suspension, solid or aqueous suspension, and other conductive forms of carbon. If the electrode plates 318 and 316 are porous, they may occupy a portion of the anorite chamber 308 and the catholite chamber 302, through which anorite and catholite flow. Alternatively, one or both of the electrode plates 318 and 316 may be constructed as gas diffusion electrodes with hydrogen gas or oxygen gas as reactants.

[0058] The first ion exchange membrane 314 is disposed between the first water chamber 306 and the anode (318, 308). In certain embodiments, the first ion exchange membrane 314 can be an AEM that allows the passage of anions but not cations, or a negative balloon selectivity membrane that allows the passage of smaller or larger negatively charged anions but not larger or smaller negatively charged or positive ion anions. In one embodiment, the first ion exchange membrane 314 can be a semipermeable membrane. An example of a material for the first ion exchange membrane is NEOSEPTA AFX (8cm²) from ASTOM. 2 )

[0059] The second ion exchange membrane 312 is disposed between the first water chamber 306 and the second water chamber 304. In certain embodiments (for example, when the first ion exchange membrane is an AEM), the second ion exchange membrane 312 may be a CEM that allows the passage of cations but not anions, or a positive balloon selectivity membrane that allows the passage of smaller or larger positively charged cations but not larger or smaller positively charged or negatively charged cations. In one embodiment, the second ion exchange membrane 312 may be a semipermeable membrane. An example of a material for the second ion exchange membrane is Fumasep(trademark) FKE-50 (8cm) from FuMA-Tech GmbH in Germany. 2 )

[0060] The third ion exchange membrane 310 is positioned between the second water chamber 304 and the cathodes (316, 302). In certain embodiments (for example, when the first ion exchange membrane 314 is an AEM), the third ion exchange membrane 310 is also an AEM. In embodiments where the first ion exchange membrane 314 is a CEM, the third ion exchange membrane 310 is also a CEM. The first and third ion exchange membranes 314, 310 are not necessarily made of the same material and / or have the same dimensions within the EDB unit 320a.

[0061] The EDB unit 320a is an electrochemical cell used to process water, including desalination and salting. Both chambers 304 and 306 receive the water to be processed. During the filling cycle, the electrolyte (e.g., salt) concentration in chamber 306 increases, and the electrolyte concentration in chamber 304 decreases. Thus, in this embodiment, chamber 306 is the salting chamber, and chamber 304 is the desalination chamber. As described above, these chambers can be replaced, with chamber 306 being the desalination chamber and chamber 304 being the salting chamber. However, in all embodiments, the electrolyte concentrations in chambers 304 and 306 change in different directions during operation.

[0062] The water treated in chambers 304 and 306 may contain one or more electrolytes that can be treated. For example, the electrolytes in chambers 304 and 306 may be any combination of water-soluble ionic salts, including but not limited to those encountered in seawater or wastewater. Exemplary cations that may be present in the electrolyte include, but are not limited to, hydronium, lithium, sodium, potassium, magnesium, calcium, aluminum, zinc, and iron. Exemplary anions that may be present in the electrolyte include, but are not limited to, chlorides, bromides, iodides, halide oxyanions, sulfur oxyanions, phosphorus oxyanions, and nitrogen oxyanions. System 300 is configured to remove the above-mentioned dissolved ion species from water having an electrolyte concentration up to the solubility limit of the ion species in the desalination chamber. In certain embodiments, the electrolyte concentration may exceed 60 thousand parts per thousand, and in further embodiments, the electrolyte concentration may exceed 80 thousand parts per thousand. The system 300 is further configured to reduce the electrolyte concentration (e.g., salt) of water to about 5,000 parts per thousand, in a further embodiment to about 2,000 parts per thousand, or in yet another embodiment to about 0.5,000 parts per thousand.

[0063] As discussed above, the EDB unit 320a can operate as a flow battery in which untreated water is continuously supplied at the input and treated water is continuously extracted from the output. The EDB unit 320a, or cell stack, including the flow plate, electrodes, gasket, and membrane, may have a planar shape (similar to a typical fuel cell), or the stack may include a tubular system with an aspect ratio similar to that of a reverse osmosis desalination module.

[0064] In a particular embodiment, a first water tank 330 is connected to water chambers 304 and 306 through ports 332 and 334, respectively. The first water tank 330 contains a first type of water W1 having a first level of salinity (e.g., seawater). The pressure of the first type of water W1 can be controlled by a first pressure controller PC1 that can apply pressure to the first type of water W1. Alternatively, instead of or in addition to the pressure controller PC1, a water pump (not shown) may be used to push water from each water tank into the EDB unit 320a at a desired flow rate. During the filling cycle, the electrolyte (e.g., salt) concentration in chamber 306 increases, and the electrolyte concentration in chamber 304 decreases. These are output from the EDB unit 320a to the switching unit 340a through ports 336 and 338, where switches S4A and S4B direct the output water through the system to water tank 350, or the water is discharged through ports 342 and 344, respectively. Cell 320a, having four chambers, continuously generates a desalination stream of water, and the switching unit 340a controls the respective salting and desalination stream outputs of the EDB unit 320a. For example, before a discharge cycle, the contents of chambers 304 and 306 are replaced with new input water from tank 330. During the discharge cycle, the electrolyte concentration in 306 decreases, and the electrolyte concentration in 304 increases, which is the opposite of what happened in the previous half-cycle. Therefore, water must be collected alternately into tank 350 by passing through chambers 304 and 306, which changes with each half-cycle.

[0065] After passing through the switching unit 340a, the water in the second tank 350 is a second water type W2 (e.g., water with a different level of salinity) that is different from the first water type W1. For example, when desalinated water is collected in the second tank 350, the second type of water may be brackish water (e.g., salinity less than about 10,000 parts per thousand). Alternatively, saline water may be collected in the second tank 350 such that W2 has a higher salinity than W1. Similar to the first type of water, the pressure of the second type of water W2 can be controlled by a second pressure controller PC2 that can apply pressure to the second type of water W2, and / or a water pump may be used. The water discharged from either port 344 or port 342 may be completely discharged from the system or stored in a separate storage tank for further use.

[0066] A set of electrical switches also determines the operating mode of the EDB unit 320a. A first set of electrical switches (S1A, S1B) controls the electrical connections of the anodes (318, 308) and cathodes (316, 302) to the other electrical nodes 300. For clarity, hereafter, regardless of whether the EDB unit 320a is operating in charge or discharge mode, the negative terminals of the EDB unit 320a will be referred to as the "anodes" (318, 308) and the positive terminals as the "cathodes" (316, 302). This takes into account the fact that both electrodes of a battery, including those described herein, can be either anodes or cathodes, depending on whether the battery is being charged or discharged.

[0067] During operation in charging mode, the first set of electrical switches (S1A, S1B) can each connect the anode (318, 308) to the negative output voltage node of the DC power supply unit, i.e., power supply unit PS, and the cathode (316, 302) to the positive output voltage node of the DC power supply unit. As used herein, “DC power supply unit” refers to a power supply unit that provides DC power, i.e., direct current power that does not change polarity as a function of time. Ions are emitted from or taken in from the anode and / or anolite (318, 308) and cathode and / or catholite (316, 302) to salt the water in chamber 306 and desalinate the water in chamber 304. The EDB unit 320a can be configured to have a cell potential of at least 0.8V, or at least 1.25V in certain embodiments.

[0068] During operation in discharge mode, the first set of electrical switches (S1A, S1B) can each have their anodes (318, 308) connected to the negative terminal of the electrical load and their cathodes (316, 302) connected to the positive terminal of the electrical load, respectively. The EDB unit 320a desalinates the water in chamber 306 and salts the water in chamber 304 while releasing stored energy using the anodes (318, 308) as the negative output electrode and the cathodes (316, 302) as the positive output electrode. As used herein, “DC output power” refers to output power provided in the form of direct current, i.e., output power whose polarity does not change as a function of time.

[0069] The electrical load may include the power grid. A second set of switches (S2A, S2B) can connect the anodes (318, 308) and cathodes (316, 302) of the EDB unit 320a to the inverter 390. The inverter 390 converts the DC output of the EDB unit 230a into an AC power output having a matching amplitude (i.e., the same amplitude as the AC voltage amplitude of the power grid) and a synchronous phase to supply to the power grid. Thus, the power discharged from the EDB unit 320a during the discharge mode can be transmitted to the power grid via the first and second sets of switches (S1A, S1B, S2A, S2B) and the inverter 390. The inverter 390 can be provided as part of the energy storage system 300 or externally on the power grid side. In one embodiment, a second set of switches (S2A, S2B) can be controlled by a power grid load monitor 392, which monitors the total power load on the power grid and connects the inverter 390 and the second set of switches (S2A, S2B) to the peak power demand on the power grid, or near it.

[0070] In certain embodiments, the energy storage system 300 includes a further optional water treatment unit 380. For example, the tank 350 may be connected to an additional water treatment unit via ports 352, 354. The further treatment unit 380 may include one or more additional EDB units represented by cell stacks 320b. Each additional EDB unit 320b includes a corresponding switching unit represented by a switching unit 340b. One or more EDB units 320b and switching units 340b operate as considered above for EDB units 320a and switching units 340a. Other optional units may include one or more desalination units represented by 360.

[0071] One or more desalination units 360 can utilize desalination technologies other than electrochemical batteries, such as reverse osmosis, capacitive deionization, electrodialysis, and thermal technologies. In one embodiment, the desalination unit 360 can perform a second or further desalination or salting process depending on the operation of the EDB unit 320a. In a further embodiment, the desalination unit 360 may be present in the system 300 and may not always be utilized even when the EDB unit 320a is operating.

[0072] The desalination unit 360 may have a port (referred to herein as the third water port 362) connected to water having a higher total dissolved solids (TDS) count (e.g., higher salinity), and another water port (referred to herein as the fourth water port 364) connected to water having a lower TDS count. For example, the water having a higher TDS count may be second type water W2 contained in water tank 350, or water received from one or more optional EDB units 320b, and the water having a lower TDS count may be third type water W3 contained in third water tank 370. For example, the TDS count of third type water W3 may be less than about 0.5 ppt, or a level considered potable water, but higher TDS counts may also be used. The pressure of the third type water W3 in third water tank 370 can be adjusted by a third pressure controller PC3 which can pressurize the third type water as needed. Alternatively, instead of, or in addition to, the pressure controllers (PC2, PC3), a water pump (not shown) may be used to push water from each water tank into one or more desalination units 360 at a desired flow rate.

[0073] In certain embodiments, the direction of the water flow between the second water tank 350 and the third water tank 370 is selected depending on whether one or more desalination units 360 are operating in salting mode or desalination mode. The desalination unit 360 can alternately operate in desalination mode, in which ions are removed from the input water while consuming the power supplied to the unit 360, and in salting mode, in which ions are introduced into the input water while releasing the energy stored in the unit 360.

[0074] During the operation of one or more optional water treatment units 380, if it is necessary to provide power input for their operation, at least a portion of the output power generated from the EDB unit 320a can be applied to those units 380. The routing of a portion of the output power generated from the EDB unit 320a to further water treatment units 380 can be provided by a third set of electrical switches (S3A, S3B) which can be connected in parallel to the power grid and a second set of electrical switches (S2A, S2B). The power input required to operate the further units 380 is typically a small amount of power stored in the EDB unit 320a as an equivalent volume of water passes through the EDB unit 320a and the additional units 380. Therefore, by routing a portion of the energy released from the EDB unit 320a to optional additional units 380 via the third set of switches (S3A, S3B), one or more water treatment units 380 can be adequately powered, and additional power can be released from the EDB unit 320a to the power grid during discharge mode.

[0075] Furthermore, the process control device 385 can control the operating modes of various components of the energy storage system 300. The process control device 385 may include a water flow control device as one of its components. The water flow control device controls the pressure of the first type of water W1, the second type of water W2, and / or the third type of water W3 via first, second, and / or third pressure control devices (PC1, PC2, PC3) or via a water pump (not shown). The water flow control device may be configured to guide the water flow in different directions as needed during charge and discharge modes, and for further salting / desalination processes.

[0076] Preliminary performance results for the above-described cell using zinc chloride / metal zinc as the anolite and (trimethylammoniummethyl)ferrocene chloride (FcNCl) as the catholite are provided in Figures 4A and 4B. Figure 4A shows a high nominal cell potential (e.g., about 1.5V) enabling high round-trip energy efficiency. Figure 4B shows the salinity of the salting and desalination streams, respectively, as a function of the cell's state of charge (SOC). As can be seen, a wide range of salt removal from seawater is possible (e.g., 35 ppt to 1.4 ppt or 96% TDS removal). However, an 80% removal rate (e.g., 35 ppt to about 7 ppt) is more economical. Even highly concentrated saline solutions that cannot be treated by reverse osmosis (e.g., about 100 ppt) can be treated with the cell having the four chambers described.

[0077] As discussed above, an electrodialysis battery with four chambers generates desalinated water during both charge and discharge half-cycles. The desalinated water can achieve salinity of 0.5 ppt or less, but this achievement comes at the cost of lower round-trip energy efficiency. The decrease in efficiency is due to the sharp increase in the battery's area resistivity (ASR) as the electrolyte content of the desalinated stream decreases. In certain embodiments, a cell with four chambers can operate in a third mode as an electrodialysis machine. If an anolite or another redox support circulates around the catholite and anolite chambers, a cell such as the one described in relation to Figures 1A-1B can operate as an electrodialysis machine in time when the cell does not need to be charged or discharged. The water with an intermediate salinity (e.g., 10 ppt) generated by the device operating in electrodialysis mode can be reintroduced into the system and further desalted to 1.2 ppt, or even 0.5 ppt (i.e., drinking water). Three alternative operating modes are further described below in relation to Figures 5A-5C.

[0078] Figure 5A shows the discharge operation mode (i.e., the first half-cycle) of an electrodialysis battery having four chambers. Water, such as seawater (e.g., about 35 ppt salinity), is input 400 to system 410. The system generates electricity that is sent to / stored in grid 420, and a saline water stream 430 (e.g., about 60 ppt salinity) that is distributed or further processed. System 410 also generates a desalination water stream with intermediate salinity 440 (e.g., about 10 ppt salinity) that is stored, for example, in a holding tank 450.

[0079] Figure 5B shows a second half-cycle, charging mode, of the electrodialysis battery having four chambers as shown in Figure 5A. Water, such as seawater (e.g., with a salinity of approximately 35 ppts), is input to the system 410 using electricity from the grid 420 (400). The system generates a saline water stream 430 (e.g., with a salinity of approximately 60 ppts) which is then disposed of or further processed. The system 410 also generates a desalination water stream with an intermediate salinity 440 (e.g., with a salinity of approximately 10 ppts) which is then stored, for example, in a holding tank 450. The cell charging and discharging modes utilize two redox active materials, as discussed above in relation to Figures 2A and 2B. The system operating in charging and discharging modes can optionally be operated in electrodialysis mode without any further additional cost.

[0080] Figure 5C shows a third electrodialysis operating mode of the electrodialysis cell having four chambers as shown in Figures 5A-5B, which is used when the cell is not in charge or discharge mode. However, in electrodialysis mode, only one redox active material is shut out, as discussed in relation to Figures 1A-1B. Therefore, a cell configured to operate in charge and discharge mode can be easily modified to electrodialysis mode, but conversely, this becomes more complex and costly due to at least a significant increase in the amount of material.

[0081] In electrodialysis mode, water from a holding tank 450 with an intermediate salinity of 440 (e.g., about 10 ppt salinity) is input to the system 410 using electricity from the grid 420. The input water may be the desalination output from one or both of the charge and discharge modes described above. The system generates a saline water stream 400 (e.g., about 35 ppt salinity), similar to the input water from the charge / discharge modes, which is then deployed and / or recycled. The system 410 also generates a desalination water stream with an even lower salinity of 460 (e.g., about 0.5 ppt salinity). For example, the desalination output stream from the electrodialysis mode may be potable and provided to consumers as fresh water. Notably, the electrodialysis mode does not store energy.

[0082] In each mode, the supply water is successively divided into salting and desalination streams. The salinity of the various supply, salting, and desalination solutions can vary independently based on the flow rate, operating current density, and many other factors in various embodiments. In further embodiments, the electrodialysis battery can produce desalination water with a salinity of 0.5 ppt or less during charging and / or discharging modes. The above modes allow the electrodialysis battery to produce fresh water using existing hardware, reducing and / or eliminating the need for a separate secondary desalination system (e.g., a secondary reverse osmosis system).

[0083] The electrodialysis mode shown in Figure 5C can be utilized in several further embodiments. The cell can also regenerate concentrated aqueous solutions of a solute (i.e., a liquid drying agent) that, when dissolved in water at a sufficiently high concentration, can remove water from different materials in which the solution is in contact. For example, a cell having four such chambers in various systems can be applied to various processes involving dehydration and / or drying, including aqueous inkjet inks, non-aqueous liquids containing dissolved water, and solid materials containing water. Exemplary embodiments may cover a variety of water removal functions, including dehumidification of air, concentration of aqueous liquids, drying of non-aqueous liquids, and dehydration of solids.

[0084] Exemplary embodiments relating to air conditioning are further described in relation to Figure 5D. Liquid desiccants are used for energy-efficient air conditioning of indoor air. To produce indoor air at a comfortable temperature and humidity (as defined, for example, by the American Society of Heating, Refrigerating and Air-Conditioning Engineers), the air conditioner may need to supercool the intake air to reduce the humidity to an acceptable level. The supercooled air is then reheated to the desired temperature using extra energy in a redundant process.

[0085] Alternatively, a smaller amount of cooling of the intake air can be combined with a different dehumidification process to produce conditioned air. One approach is to achieve dehumidification using liquid desiccants. For example, water is absorbed into a liquid desiccant medium that has a high affinity for water vapor, sometimes via a membrane. Examples of such liquid desiccants include concentrated aqueous solutions of ionic salts such as calcium chloride, lithium chloride, and lithium bromide. After the desiccant absorbs water vapor from the air, it is diluted to its original concentration or approximately its original concentration and must be reconcentrated (i.e., regenerated) to its original concentration or approximately its original concentration while removing any excess water absorbed from the intake air for reuse.

[0086] Some approaches involve heating the diluted solution to evaporate excess water, but these approaches are inefficient because the evaporation rate slows down as the salt content and relative humidity of the solution increase. Furthermore, the liquid desiccant needs to be cooled before starting a new process to avoid undesirable heating of the conditioned air. As discussed above in relation to Figures 1A and 1B, the four-chamber cell described herein performs energy-efficient electrodialysis in a non-thermal process. The four-chamber cell operating in electrodialysis mode can reconcentrate the diluted liquid desiccant solution by separating the concentrated liquid desiccant stream from the water absorbed from the intake air.

[0087] Figure 5D shows a system incorporating a cell with four chambers in a dehumidification process. The dehumidification module 470 takes in input air 474 (e.g., air to be cooled) and exposes the input air 474 to a liquid desiccant having a first concentration (e.g., 40% lithium chloride) 472. The liquid desiccant 472 dehumidifies the air by removing water vapor from the input air. The dehumidified air is then cooled and / or further processed and output from module 470. As the air is dehumidified, the liquid desiccant absorbs water vapor from the air, thereby diluting the liquid desiccant to a second concentration (e.g., 35% lithium chloride) 476. The diluted liquid desiccant 476 then becomes an input 478 to a system 410 containing a cell with four chambers, as described above in relation to Figure 3. For example, the dehumidification module 470 replaces the first water tank 330, and input 478 replaces ports 332, 334. The diluted liquid drying agent 476 will be introduced into chambers 304 and 306 for processing.

[0088] Next, the liquid desiccant is reconcentrated using a cell having four chambers, which is typically a concentrated solution of an inorganic salt (e.g., lithium chloride). In certain embodiments, to reduce the loss of water crossover from the desalting stream to the salting stream, system 410 may also include a cell having one or more additional different four chambers (e.g., represented by cell stack 320b), where the saltiness is reduced to a desired level in several stages. Embodiments targeting the regeneration of liquid desiccants utilize a single redox shuttle for energy efficiency. In some embodiments, the redox shuttle may also contain some amount of dissolved inorganic salt acting as a supporting electrolyte, osmotically balancing all four chambers of cell stack 320b. In certain embodiments, the dissolved inorganic salt is the same material as the liquid desiccant being regenerated. As discussed above, the system can operate at negligible overpotential. The single redox shuttle is also operated at a concentration that reduces and / or minimizes net water crossover to and from both the salting and desalting streams. An exemplary redox shuttle is BTMAP-Fc, as discussed above, because it has very high solubility in water that allows for or can closely match the concentration of the desiccant stream (e.g., up to about 1.9 moles to about 10 moles), or because it can remain dissolved in a solution containing a high concentration of dissolved inorganic salt that acts as a supporting electrolyte, while maintaining osmotic balance in all four chambers of cell stack 320b.

[0089] System 410 outputs a regenerated liquid desiccant stream 472 (e.g., a salt-added stream) having a concentration approximately the same as or the same as the first concentration (e.g., 40% lithium chloride). This stream is then supplied to return to the dehumidification module 470. Similar to FIG. 5C, system 410 also outputs a desalination stream 480. The desalination stream still contains at least a small amount of dissolved salts that can be discharged as waste. Alternatively, if the salt is inexpensive enough to discard, the desalination stream 480 can be reused as domestic wastewater, thereby generating operating costs. In a further embodiment, the desalination stream 480 can be reconcentrated using a technique other than electrodialysis, such as membrane pervaporation, and supplied to return to an intermediate processing stage of the system 410. In an HVAC embodiment, the reconcentration may be performed using an evaporation method to enable additional sensible cooling when integrated into a complete HVAC system. As discussed above, the dehumidification process, including the regeneration of the liquid desiccant, is performed with low specific energy consumption through the incorporation of a desalination cell having four chambers.

[0090] In some embodiments, the electrochemical device has a concentration efficiency greater than -0.0800226x 4 +0.0641781x 3 -0.0156863x 2 +0.0008604x + 0.00007 g / J for at least a portion of the range 0 < x < 0.35, where x is the average mass fraction of the salt in the electrolyte. In other embodiments, the device has a concentration efficiency of 0.2011769x 4 -0.1695373x 3 +0.054343x 2It has a concentration efficiency greater than -0.0081837x+0.00054 g / J. Figure 15 shows the concentration efficiencies of different pairs of membranes. Concentration efficiencies greater than line 1510 indicate desirable performance of membrane pairs in the electrochemical device described herein, and efficiencies greater than line 1508 indicate improved performance. For example, the data for the membrane pair shown by line 1504 is considered good performance, the performance of the pair shown by line 1506 is improved performance compared to the performance of line 1504, and the performance shown for the pair at 1502 is the most improved performance in the group.

[0091] In some embodiments, the solution in the first reservoir is equilibrated with the solution in the second reservoir at a concentration difference of 1% salt / amp of the current applied to the electrode.

[0092] In summary, the desalination cell having the four (or more) chambers described above may use either one redox active species circulating around the anode and cathode, undergoing a Faraday reaction at both electrodes, or two redox active species, each limited to either the anode or the cathode. Various embodiments utilizing such a cell can perform electrodialysis with low specific energy consumption and generate desalination and saline water optionally coupled to electrical energy storage during a half-cycle of charging or discharging, and may allow the device combining water desalination and energy storage to operate reversibly in a mode that enables electrodialysis with low specific energy consumption.

[0093] The above characteristics will be discussed in more detail with respect to the following examples. [Examples]

[0094] An energy-efficient redox-assisted electrodialysis system consistent with that shown in Figure 1 was constructed. The anode and cathode consisted of three sheets of porous carbon fiber paper (SGL 39AA) pressed onto a pyrosealed graphite block with a meandering flow channel (Entegris) and separated from the central desalination / salting chamber by a Viton gasket. The anion exchange membrane was Fumasep FAS-15, and the cation exchange membrane was Nafion 212.

[0095] When a 50 mL solution of 0.1 M Na3Fe(CN)6, 0.1 M Na4Fe(CN)6, and 1% NaCl was passed through the anode / cathode, and 0.6 M NaCl was present in both the salting and desalting chambers (50 mL each), the system's high-frequency ASR was 11.5 Ω·cm. 2 Measured at [location], the polarization ASR was 13.7 Ω·cm. 2 Figure 6A shows the relationship between the applied potential and the resulting current density 602 (square points, left axis), and the system polarization ASR as a function of the current density 604 (circular points, right axis). Figure 6B shows the relationship with the system's specific energy consumption as a function of the current density (or NaCl transport rate). Each experimental data point is shown as a square. The current density is directly proportional to the salt transport rate. Depending on how the cell operates, the specific energy consumption is approximately 80 mA / cm². 2 At current densities below this level, it is lower than that of conventional electrodialysis, approximately 20 mA / cm². 2 Although lower than that of seawater reverse osmosis, the specific energy consumption for reverse osmosis increases sharply with increasing salinity.

[0096] If necessary, the cell can produce a greater amount of desalination with a higher specific energy consumption. The improvement in the cell's specific energy consumption is expected as a result of a reduced ASR. In this system, the direct production of water with potable salinity (e.g., less than 0.5 ppt of NaCl) is possible in a single step from seawater (e.g., 35 ppt of NaCl). A constant voltage of 0.5 V was applied to the cell to increase the salinity of the water in the salting chamber and decrease the salinity of the water in the desalination chamber. The salinity can be reduced to below the threshold concentration of potable salinity. The progression of salinity of the water in the salting and desalination chambers is shown in Figure 6C as a function of charge passing through and in Figure 6 as a function of time. At the end of the experiment, the water in the desalination chamber had an NaCl concentration of 0.3 ppt, well below the threshold of potable salinity.

[0097] To compare the redox-assisted cell with conventional electrodialysis, the specific energy consumption was modeled for the conventional electrodialysis process performed in the same cell as described above. Figure 7A shows the obtained operating potential (solid line) and specific energy consumption (dashed line) for each conventional and redox-assisted electrodialysis system in the cell stack. Since ASR is governed by membrane resistance, ionic conductivity of the electrolyte in the intervening chamber, and intermembrane spacing, the cell ASR is expected to be similar between conventional and redox-assisted electrodialysis. In general, the contribution of additional potential to the specific energy consumption for conventional electrodialysis can be reduced by a multiple of n for all n pairs of salting / desalting chambers between each anode and cathode. However, it can never be reduced to zero. Figure 7B provides a comparison of the specific energy consumption of redox-assisted and conventional electrodialysis for a cell with one pair of salting / desalting chambers and 25 pairs of chambers per anode and cathode. In certain embodiments, such as the cell stack described in this example, n=1, but n=25 is typical in conventional electrodialysis. [Examples]

[0098] In a further embodiment, BTMap-Fc was used instead of Fe(CN) as the redox shuttle. The use of BTMAP-Fc is expected to avoid the formation of insoluble solids from the reaction of Fe(CN) with certain metal ions. A second energy-efficient redox-assisted electrodialysis system was constructed in accordance with that shown in Figure 1B. The anode and cathode consisted of three sheets of porous carbon fiber paper (SGL 39AA) pressed onto a pyrosealed graphite block with a meandering flow channel (Entegris) and separated from the central desalination / salting chamber by a Viton gasket. The anion exchange membrane was Fumasep FAS-30 and the cation exchange membrane was Fumasep E630.

[0099] 0.05M BTMAP-Fc, 0.05M BTMAP-Fc + A 1% NaCl solution (50 mL) was flowed through the anode / cathode, and 0.6 M NaCl was present in both the salting and desalting chambers (50 mL each). The system's high-frequency ASR was 17.9 Ω·cm. 2 Measured at [location], the polarization ASR was 26.0 Ω·cm. 2 Figure 14A shows the relationship between the applied potential and the resulting current density 1402 (square points, left axis), and the system polarization ASR as a function of the current density 1404 (circular points, right axis). Figure 14B shows the relationship between specific energy consumptions of the system as a function of current density (or NaCl transport rate). Each experimental data point is shown as a square. The current density is directly proportional to the salt transport rate. Depending on how the cell operates, the specific energy consumption is approximately 40 mA / cm². 2 At current densities below this level, it is lower than that of conventional electrodialysis, approximately 10 mA / cm². 2Although lower than that of reverse osmosis, the specific energy consumption for reverse osmosis increases sharply with increasing salinity. If necessary, the cell can produce more desalination with higher specific energy consumption. The improvement in the cell's specific energy consumption is expected as a result of reduced ASR. In this system, direct production of water with potable salinity (less than 0.5 ppt NaCl) is possible in a single step from seawater (e.g., 35 ppt NaCl). A constant voltage of 0.5 V was applied to the cell to increase the salinity of the water in the salting chamber and decrease the salinity of the water in the desalination chamber. The progression of salinity of the water in the salting and desalination chambers is shown in Figure 14C as a function of charge passing through and in Figure 14D as a function of time. At the end of the experiment, the water in the desalination chamber had an NaCl concentration of 0.3 ppt, well below the threshold for potable salinity.

[0100] In yet another embodiment, several stages of desalting are performed, and the redox-active reactant is optionally used with the salt-containing supported electrolyte in the salting / desalting stage, at a concentration appropriate to the salt concentration in the salting / desalting stage, in order to minimize water transport in each stage. This reduces or minimizes the energy inefficiencies resulting from water transport to and from the anolite / castholite chambers. [Examples]

[0101] To determine which combination of cell size and current density (and therefore water output) yields the most economical concept for a given battery capacity, an advanced bottom-up cost model was constructed for a Zn|FcNCl battery matching the design in Figures 2A-2B, with experimentally obtained polarization ASR values ​​reported in the above examples as input. A 1MW, 12MWh (delivery) system yielded 17.5mA / cm². 2 With an optimized current density, approximately 10 ppt of salinity, 2000 m³ per day 3It can generate brackish water. Various performance metrics of this electrodialysis battery system are shown in Figures 8A to 8D. Figure 8A shows the system cost and revenue of the electrodialysis battery with the four chambers described above, using the conservative pricing described. Short term (e.g., current), medium term (e.g., 5 years), and long term (e.g., 10 years) refer to the projected prices of the various components of the cell stack. Figure 8B shows the round-trip energy efficiency performance including estimated shunt and pumping losses, and Figure 8C shows the net system values ​​(i.e., lower system cost revenue) for the short term, medium term, and long term. Figure 8D also provides the projected break-even time, which decreases over the life of the system. As can be seen, the corresponding round-trip energy efficiency is 55%, and the overall specific energy consumption for desalination is 0.196 kWh / kg NaCl (or 4.91 kWh / m³ of desalination produced at 10 ppt). 3 )

[0102] The minimum break-even time is 7.4 years with an internal rate of return (IRR) of 13.5%, assuming a conservation price of $0.04 / kWh for electricity and $0.81 / m³ for completely desalinated water. 3 , and an additional cost of $0.17 / m for handling brackish water output. 3 This is assumed. The U.S. Department of Energy's cost target for energy storage ($150 / kWh) is taken as the first approximation of the "value" of energy storage.

[0103] However, economic problems become even more pressing in the world's arid regions where energy is readily available in the form of solar radiation or fossil fuels, and where there is a high demand for freshwater. Such places include Saudi Arabia and other countries around the Persian Gulf. In those regions, the price of freshwater is higher, at approximately $1.35 / m³. 3This reflects the increased demand and difficulty in desalination of the higher salinity saltwater of the Persian Gulf, which is typically around 45 ppt (compared to 35 ppt for typical seawater). Also, a lower price of approximately $0.02 / kWh for input electricity is possible in that region of the world. Equivalent system costs, revenue, and related performance metrics are shown in Figures 9A–D.

[0104] Short-term (e.g., current), medium-term (e.g., 5 years), and long-term (e.g., 10 years) again refer to price forecasts for the various components of the cell stack. Figure 9A shows the system cost and revenue of the electrodialysis battery with the four chambers described above, using optimistic but achievable pricing for the Persian Gulf region. Figure 9B shows the round-trip energy efficiency performance, including estimated shunt and pumping losses, and Figure 9C shows the net system values ​​(i.e., lower system cost revenue) for the short, medium, and long term. Figure 9D also provides the projected break-even time, which decreases over the lifespan of the system. In this scenario, recalculated for another 1MW, 12MWh system, the optimal current density is 25mA / cm² with a round-trip energy efficiency of 42%. 2 And, at 10 ppt, 1600m 3 It produces desalination per day. The specific energy consumption is 0.293 kWh / kg for NaCl removal, or 10.26 kWh / m³ for the desalination produced. 3 This is predicted. The minimum break-even period is 4.6 years with an IRR of 21.7%.

[0105] In both scenarios, as shown in Figure 10, the decomposition of component costs indicates that costs are dominated by the various ion-selective membranes within the cell. The IRR in both scenarios heavily depends on the polarization ASR of the cell stack, based on experimental results not optimized herein. Further improvements to the ASR can be made by refining the cell design to reduce and / or minimize inter-membrane separation, which currently accounts for the bulk of the system ASR. Since operating costs heavily depend on the lifetimes of the various membranes, ligands and / or surface treatments may be used. For example, Zn in a seawater chamber across an AEM. 2+ Ion crossover can cause anolite loss. Since zinc is inexpensive and easily removed downstream, some membrane crossovers can be tolerated by periodically adding zinc for rebalancing. However, if the measured crossover rate is unacceptably high (i.e., too expensive), ligands and / or surface treatments can be added to the membrane (even on the catholite side) to reduce the crossover. Based on this analysis, the system life is expected to be comparable to or longer than conventional electrodialysis (e.g., about 10 years) because the membrane is not exposed to extreme pH from water splitting or chlorine progression. The use of such electrochemical desalination flow batteries is described further below.

[0106] Figure 11 shows an exemplary method for using an electrochemical desalination flow battery having the four chambers described above in an energy storage system. More specifically, the device operates as a desalination flow battery, storing electricity and desalination water in alternating cycles. Because the cycles are alternating, either a charging cycle or a discharging cycle can be considered “first”. In the example in Figure 11, the battery is discharged to generate salted and desalination outputs, storing energy in the first half-cycle (1102). In the second half-cycle, the electrochemical battery is charged to generate salted and desalination outputs (1104). In certain embodiments, the energy used to perform the charging cycle may be derived from renewable resources such as solar or wind power. The flow battery may operate with a single redox active species circulating around the anode and cathode, both undergoing Faraday reactions at both electrodes, or with two redox active species, one at each electrode.

[0107] The method shown in Figure 11 is further described below. In a discharge half-cycle, an electrochemical desalination battery unit is provided. The battery unit includes at least one pair of water reservoirs, each including an input and an output. Water (e.g., seawater with a salinity of about 35 ppt) is input to the two water reservoirs. During the discharge mode, the salinity of the water in the first reservoir decreases to below a threshold concentration (e.g., about 10 ppt, or about 0.5 ppt in other embodiments), and the salinity of the water in the second reservoir increases (e.g., to about 60 ppt). At least one anode is configured to contain a first solution of the first electrolyte material and to accept and have a reversible redox reaction with at least one redox active ion in the water of the first reservoir, and at least one cathode is configured to contain a second solution of the second electrolyte material and to accept and have a reversible redox reaction with at least one redox active ion in the water of the second reservoir. A pair of water reservoirs are separated by a first type of exchange membrane (e.g., AEM). A second type of exchange membrane (e.g., CEM), different from the first type of exchange membrane, is disposed between at least one anode and the first water reservoir, and also between at least one cathode and the second water reservoir. During discharge, the water to be treated (e.g., seawater) is transported into / through the first and second water reservoirs. The desalination water from the first water reservoir is stored, for example, in a holding tank, while removing / discharging the salted water generated in the second reservoir from the system. Alternatively, the salted stream may be stored, for example, in another holding tank, for further processing or use. Electricity is also generated and stored in the power grid. The desalination water may then be optionally supplied to one or more additional electrochemical desalination battery units having a similar design and / or one or more additional desalination systems using water treatment processes other than electrochemical batteries. Additional desalination batteries and / or desalination systems may be provided in series in any order and combination. The water output from the system may be potable, for example, having a salinity of 0.5 thousand parts per thousand or less.

[0108] Before the other half-cycle, in this case the charging half-cycle, the contents of the first pair of water reservoirs are replaced with new water to be treated (e.g., new seawater). During the charging cycle, the salinity of the second water reservoir decreases and the salinity of the first water reservoir increases (the reservoirs change their role during the opposing half-cycle). Therefore, it is necessary to alternately collect the water passing through each water reservoir. For example, during the charging mode, desalination water is collected and stored from the second water reservoir, and the salted stream output from the first reservoir is discharged. During the charging, discharging, and electrodialysis modes, the desalination battery generates desalination water.

[0109] Because desalination batteries are capable of both energy storage and desalination, the desalination process can be combined with energy storage, and the battery can be charged, discharged, and / or idled at different rates and durations. This variation can increase or maximize the amount of electrical energy stored and delivered, the amount of salted and / or desalination water flux, and / or the total system revenue. This versatility in use is not achievable with systems capable of only one of either desalination or energy storage.

[0110] When the above system contains a single redox active species and is not being filled or discharged, it may be operated in a third electrodialysis mode, as shown in Figure 12, to generate salting and desalting outputs. For example, the system may receive brackish water with an intermediate salinity (e.g., about 10 ppt) as input to cell 1202. Operating the cell 1204, as described in relation to Figures 1A and 1B, provides outputs of at least one salting stream with a salinity higher than the input water and at least one desalting stream with a salinity lower than the input water, such as drinking water (e.g., water with a TDS of 0.5 ppt or less).

[0111] Further embodiments utilizing the system described above in relation to Figures 11 and 12 are for HVAC applications such as dehumidification for air conditioning and are further described in Figure 13. Before input to the desalination system, water (e.g., water vapor) is removed from the air using a liquid desiccant (1302). The diluted liquid desiccant is input to a desalination cell system having four chambers, as described above (1304). Processing the input liquid desiccant (e.g., instead of seawater) produces salted and desalination streams of the regenerated liquid desiccant (e.g., at or near the concentration used in the dehumidification process) (1306). The system may be used in this manner in various embodiments, including non-aqueous solutions for separation into salted and desalination streams.

[0112] In certain embodiments, the hybrid desalination battery may be used to desalinate brine from seawater or saline aquifers. In other embodiments, the battery may be used to desalinate a wide variety of industrial waste streams or geothermal brine that may have different pH values ​​and / or may contain varying amounts of non-aqueous solvents. In further embodiments, the battery may be used to selectively remove / add ions to one of the water reservoirs while maintaining one or more properties of the electrolyte, such as pH, total suspended solids, and electrical conductivity. In particular, the hybrid desalination battery may operate at a pH similar to the incoming feed (e.g., seawater / brine) to reduce or minimize the need for pH adjustment. Also, as discussed above, in other embodiments, one chamber (e.g., anolite) may have a slightly lower pH than the other chambers.

[0113] Unless otherwise indicated, all numbers used in this specification and the claims to represent feature sizes, quantities, and physical properties should be understood in all cases to be modified by the term “approximately.” Therefore, unless otherwise indicated, the numerical parameters described in the foregoing specification and the appended claims are approximations that may vary depending on the desired properties that a person skilled in the art would seek to obtain using the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5), as well as any range within that range.

[0114] The foregoing description is provided for illustrative and explanatory purposes only. It is not intended to be exhaustive or to strictly limit the embodiments to those disclosed. Many modifications and variations are possible in light of the above teachings. Any or all features of the disclosed embodiments can be applied individually or in any combination and are not intended to be limiting, but are merely illustrative. The scope of the invention is not intended to be limited to these “modes for carrying out the invention,” but rather to be determined by the “claims” appended herein.

Claims

1. 1. An electrochemical device comprising: a first reservoir having an input and an output, the first reservoir having an input solution that increases in concentration to a threshold concentration during an operational mode; a second reservoir having an input and an output, wherein a concentration of the input solution decreases during the mode of operation; a first redox-active electrolyte chamber including a first solution of a redox-active electrolyte material and at least one first electrode configured to have a reversible redox reaction with the first redox-active electrolyte material to drive at least one ion into the input solution in the first reservoir; a second redox-active electrolyte chamber including a second solution of a redox-active electrolyte material and at least one second electrode configured to have a reversible redox reaction with the second redox-active electrolyte material, the second redox-active electrolyte chamber receiving at least one ion from the input solution in the second reservoir; a first type membrane disposed between the first reservoir and the second reservoir; a second type membrane different from the first type, the second type membrane being disposed between the first redox-active electrolyte chamber and the first reservoir and disposed between the second redox-active electrolyte chamber and the second reservoir, the first type membrane and the second type membrane being heterogeneous and comprising a dispersion of a ceramic and a non-ion-conducting hydrophobic polymer in a matrix of an ionomer, and the first type membrane and the second type membrane being unreinforced membranes.

2. 10. The device of claim 1, wherein the first solution of redox-active electrolyte material or the second solution of redox-active electrolyte material comprises LiCl.

3. 2. The device of claim 1, wherein at least one of the first type and the second type membranes has a swelling degree of less than 30% when equilibrated in an electrolyte having a salt mass fraction of less than 0.

4.

4. The device of claim 1 , wherein at least one of the first type and the second type films has a thickness of 50 micrometers or less.

5. 2. The device of claim 1, wherein at least one of the first type and second type membranes comprises one of polyamide, polytetrafluoroethylene, polyetheretherketone, polyethylene, polyethylene terephthalate, polypropylene, fluoroelastomer, polyvinylidene fluoride, fluorinated ethylene propylene, polysulfone, polybenzimidazole, perfluoroalkoxy polymer, polymer containing aromatic groups, polyolefin, aromatic polyamide (aramid), carbon fiber, graphene, graphene oxide, graphene derived material, clay, polyoligosilsesquioxane, silica particles, titania particles, and alumina particles.

6. 10. The device of claim 1, wherein the first type of membrane comprises ion-conducting groups comprising at least one of quaternary amines, cationic aromatic amines, imidazolium, pyridinium, guanidinium, piperazinium, and diallyldimethylammonium.

7. 10. The device of claim 1, wherein the second type of membrane comprises ion-conducting groups comprising at least one of sulfonated polyetheretherketone, sulfonate, perfluorosulfonate, phosphonate, and carboxylate.

8. 2. The device of claim 1, wherein a membrane pair of the first type membrane and the second type membrane has an electroosmotic transport coefficient (tw) value less than -39x+16 for at least a portion of the range 0≦x≦0.4, where x is the mass fraction of solute in the initial input solutions of the first and second reservoirs, and the electroosmotic transport coefficient (tw) is defined as the ratio of moles of water transported across the membrane to moles of salt transported across the membrane as ions move across the membrane due to a driving force acting on the ions.

9. 2. The device of claim 1, wherein at least one of the first type and the second type membranes has a fixed charge concentration (C) of at least 5 charge equivalents per liter when equilibrated in an electrolyte having a salt mass fraction of less than 0.4, where C is the equivalent of fixed charge per volume of water in the membrane after equilibration with the electrolyte.

10. 2. The device of claim 1, wherein at least one of the first type and the second type membranes has a co-ion concentration less than or equal to the molar salt concentration of the electrolyte solution when the membrane is equilibrated in the electrolyte solution, a co-ion being a free ion in the membrane having the same charge sign as a fixed charge in the membrane, and the co-ion concentration can be defined as moles of co-ion per volume of membrane swollen in electrolyte, moles of co-ion per dry mass or volume of the membrane, or moles of co-ion per volume of solvent in the swollen membrane.

11. 11. The device of claim 10, wherein the co-ion concentration is less than 21x-0.87 mol / L, where x is the mass fraction of salt in the electrolyte, for all or part of the range 0<x<0.4, the salt is LiCl, and the solvent comprises water.

12. 10. The device of claim 1, wherein at least one of the first type and the second type membranes has a permeation flux less than -1x+0.43 L / m2 / hr when the at least one membrane is equilibrated in an electrolyte and for at least a portion of the range 0<x<0.4, where x is the mass fraction of salt in the electrolyte, and permeation is the spontaneous, non-electrically driven transport of solvent molecules across the membrane from a solution with a low salt concentration to a solution with a high salt concentration.

13. 2. The device of claim 1, wherein a membrane pair of the first type membrane and the second type membrane has a Coulombic efficiency of greater than 70% when the pair is equilibrated in an electrolyte solution and for at least a portion of the range 0<x<0.4, where x is the mass fraction of salt in the electrolyte solution, the Coulombic efficiency describing the charge efficiency with which ions move through the membrane.

14. 14. The device of claim 13, wherein the salt is LiCl and the electrolyte solution comprises greater than 60% water.

15. 2. The device of claim 1, wherein the combination of the first type membrane and one of the second type membranes is configured to equilibrate the solution in the first reservoir with the solution in the second reservoir at a concentration difference of 1% salt / Amp of applied current to at least one of the first and second electrodes.

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