Capacitive deionization device

Abstract

The present disclosure relates to a capacitive deionization (CDI) device (40) having at least one cell comprising a first electrode (72) and a second electrode (73), the second electrode (73) opposing the first electrode (72), wherein the device further comprises a third electrode (77) arranged between the first electrode (72) and the second electrode (73), the third electrode (77) configured to allow a flow of aqueous media from a first side of the third electrode (77) facing the first electrode (72) to a second side of the third electrode facing the second electrode (73), wherein the third electrode (77) and one of the first electrode (72) and the second electrode (73) are configured to be positively charged, while another one of the first electrode (72) and the second electrode (73) is configured to be negatively charged.

Description

CAPACITIVE DEIONIZATION DEVICETECHNICAL FIELD

[0001] The present disclosure relates to a capacitive deionization (CDI) device.BACKGROUND

[0002] The need for clean and potable water is continuously increasing due to factors such as environmental issues and population growth. As a consequence, also the need for desalination or deionization of water, such as seawater or brackish water, is increasing. There are several techniques for deionization of water, including for example distillation, reverse osmosis and electrodialysis. Another example of a technique for deionization of water is capacitive deionization (CDI).

[0003] CDI is generally used for electrosorption of charged contaminants like salts, metal ions, and charged organics from brackish water or other water sources which are not immediately suitable for human consumption. Compared to the formerly mentioned techniques, CDI has the advantage of being a relatively energyefficient technology, especially for water having a fairly moderate charged contaminant concentration such as brackish water.

[0004] In the CDI technology, electrically conducting electrodes of activated carbon maybe utilised for electrosorption of all types of charged contaminants. A selected number of CDI cells can be arranged in a CDI device depending on required electrosorption capacity of the CDI device; the higher the capacity, the greater the number of CDI cells. A typical CDI cell comprises of two oppositely placed electrodes separated by a non-conductive spacer through which water can flow. The electrodes are polarized positively and negatively using a DC power source. Charged contaminants of counter-charge are electrically attracted to the respective electrodes and temporarily held by the electrodes. Thereby, the charged contaminants are removed from water present between the electrodes and the water being output from the CDI cell has thus been deionized and purified.

[0005] A problem with prior art CDI devices is that the electrodes are subjected to oxidation, which decreases operational life of the electrodes.SUMMARY

[0006] One objective is to solve, or at least mitigate, this problem in the art and thus to provide an improved CDI device.

[0007] This objective is attained in an aspect by a capacitive deionization device having at least one cell comprising a first electrode and a second electrode, the second electrode opposing the first electrode, wherein the device further comprises a third electrode arranged between the first electrode and the second electrode, the third electrode configured to allow a flow of aqueous media from a first side of the third electrode facing the first electrode to a second side of the third electrode facing the second electrode, wherein the third electrode and one of the first electrode and the second electrode are configured to be positively charged, while another one of the first electrode and the second electrode (3) is configured to be negatively charged.

[0008] Advantageously, voltage applied to the electrodes is distributed over a greater volume (the electrodes being made of e.g. carbon), i.e. over twice the carbon mass embodied by the first electrode and the third electrode taken together, which reduces the voltage over the first electrode by 50% and hence roughly doubles the lifetime of the first electrode given the reduction in oxidation.

[0009] In an embodiment, the capacitive deionization device further comprises a switching circuitry via which the first electrode, second electrode and third electrode is connected to a power supply applying the charge to the first, second and third electrodes, wherein the switching circuitry is configured to be controlled to selectively apply a positive charge to the first electrode and a negative charge to the second electrode in a first deionization state and, a negative charge to the first electrode and a positive charge to the second electrode in a second deionization state, while maintaining a positive charge on the third electrode in both the first and the second deionization state.

[0010] In an embodiment, the switching device is further configured to be controlled to cause a short circuit of the first electrode, second electrode and third electrode in a regeneration state.

[0011] In an embodiment, the switching device comprises a first switch connected in the first deionization state to positive charge, a second switch connected in the first deionization state to negative charge, a third switch connected in the firstdeionization state via the first switch to positive charge, a fourth switch connected in the first deionization state via the second switch to negative charge, and a fifth switch connected in the first deionization state via the third switch and the first switch to positive charge, wherein the first electrode is connected in the first deionization state via the third switch and the first switch to positive charge, the second electrode is connected in the first deionization state via the fourth switch and the second switch to negative charge, and the third electrode is connected in the first deionization state via the fifth switch to the first electrode.

[0012] In an embodiment, wherein the first switch is connected in the second deionization state to negative charge, the second switch is connected in the second deionization state to positive charge, the third switch is connected in the second deionization state via the first switch to negative charge, the fourth switch is connected in the second deionization state via the second switch to positive charge, and the fifth switch is connected in the second deionization state via the fourth switch and the second switch to positive charge, wherein the first electrode is connected in the second deionization state via the third switch and the first switch to negative charge, the second electrode is connected in the second deionization state via the fourth switch and the second switch (62) to positive charge, and the third electrode is connected in the second deionization state via the fifth switch to the second electrode.

[0013] In an embodiment, the third switch is connected in the regeneration state to the fourth switch and either, depending on switch status of the fifth switch, the third switch is connected in the regeneration state to the fifth switch or the fourth switch is connected in the regeneration state to the fifth switch, wherein the first electrode and the second electrode are interconnected in the regeneration state via the third switch and the fourth switch, and the third electrode is connected in the regeneration state to the fifth switch, and either to the first electrode or the second electrode depending on switch status of the fifth switch, thereby causing short circuiting of the first, second and third electrodes.

[0014] In an embodiment, a plurality of capacitive deionization device cells are connected in series, and the first, second, third and fourth switch are commonly utilized by the plurality of cells, the third switch being connected to the first electrode of a first cell in the series of cells and the fourth switch being connected to the second electrode of a last cell in the series of cells, wherein the series of cells are formed byconnecting the second electrode of a cell in the series to the first electrode of the next cell in the series, and each cell is connected to an individual fifth switch.

[0015] In an embodiment, the capacitive deionization device further comprises a processing device configured to detect polarity of the power supply and control the switching of the switching circuitry for connecting the third electrode to the positive polarity of a power supply.

[0016] In an embodiment, the processing device is configured to continuously switch the polarity of the power supply, and further to control the switches to correspondingly switch between the first and the second deionization state with the switching of the polarity of the power supply.

[0017] In an embodiment, the capacitive deionization device further comprises an interface to which the power supply is configured to be connected.

[0018] In an embodiment, the capacitive deionization device further comprises an internal power source configured to at least partly power the capacitive deionization device.

[0019] In an embodiment, the internal power source is configured to be chargeable by the power supply via the interface.

[0020] In an embodiment, the first, second and third electrodes are made of carbon or a carbon-based material, preferably an activated carbon cloth, a graphite plate or one or more graphene sheets.

[0021] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Aspects and embodiments are now described, by way of example, with reference to the accompanying drawings, in which:

[0023] Figure 1 schematically illustrates a prior art CDI device;

[0024] Figure 2 schematically illustrates the electrical field of, and the ion transport in, a prior art CDI device;

[0025] Figure 3 shows in a left-hand illustration a 3-electrode CDI device while a right-hand illustration shows a cross-section of the CDI device taken along line B-B;

[0026] Figure 4a illustrates a front perspective exploded view of a CDI device according to an embodiment; and

[0027] Figure 4b illustrates a back perspective exploded view of the CDI device of Figure 4a according to an embodiment;

[0028] Figure 4 schematically illustrates one example of a possible circuit diagram for a DC power supply with three terminals and its connection to a CDI cell in the art;

[0029] Figure 5a illustrates a prior art polarity configuration where the central electrode of a CDI cell is connected to ground;

[0030] Figure 5b illustrates a polarity configuration where the central electrode of a CDI cell is connected to positive polarity according to an embodiment; and

[0031] Figure 6a illustrates an embodiment where a switching circuitry is provided in order to carry out CDI device deionization;

[0032] Figure 6b illustrates an embodiment where the switching circuitry carries out CDI device deionization with a switched power supply polarization;

[0033] Figure 7 illustrates an embodiment where the switching circuitry carries out CDI device regeneration; and

[0034] Figure 8 illustrates an embodiment where the switching circuitry handles a plurality of series-connected CDI cells.DETAILED DESCRIPTION

[0035] The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown.

[0036] These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully conveythe scope of all aspects of invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0037] Figure 1 schematically illustrates a prior art CDI device 10 comprising a first electrode 2 and a second electrode 3 as disclosed by the Applicant in European patent no. EP 3 642 165. These electrodes are sometimes referred to as "primary electrodes" or "master electrodes". This is referred to as a flat cell architecture, and while the architecture of prior art CDI devices may take on many different forms that does not necessarily have the appearance of that of Figure 1, Figure 1 is included for describing basic operational principle of a CDI device. As is understood, the CDI device of embodiments to be discussed hereinbelow does not necessarily have the appearance and / or formfactor of the prior art CDI device disclosed throughout Figures 1-3.

[0038] In Figure 1, the first and second electrodes are planar electrodes arranged in opposite, preferably in parallel to, each other. Aqueous media from which charged contaminants are to be removed is intended to flow through the entire volume of the CDI device 10 including the first electrode 2 and the second electrode 3, as the electrode materials are permeable to aqueous media being for instance brackish water.

[0039] The first and second electrodes 2, 3 are usually separated by a first electrically nonconductive spacer 4. The device 10 further optionally comprises more than one non-conductive spacer, as illustrated in Figure 1 by a second electrically nonconductive spacer 4'. The purpose of the nonconductive spacer(s) is primarily to avoid the risk of electrical short-circuit between the first electrode 2 and the second electrode 3 during operation of the device 1.

[0040] Aqueous media, such as water to be purified, is preferably passed through the nonconductive spacer(s). Usually, the electrodes 2, 3 are in direct contact with the spacer(s).

[0041] The CDI device 10 further comprises a first current collector 5 connected to the first electrode 2, and a second current collector 6 connected to the second electrode 3. In a conventional CDI device, the electrode selected as cathode is generally connected to the negative terminal of a DC supply, which is typically connected to electrical ground and the electrode selected as anode is polarized withreference to the cathode and connected to the positive terminal of the DC supply. The electrodes 2, 3 are connected via the respective current collectors 5, 6 to a DC power source (not shown) in order to enable polarization of the electrodes.

[0042] During operation of the CDI device 10, negatively charged contaminants are attracted to the positive electrode and held non-permanently in the positive electrode, while positively charged contaminants are attracted to the negative electrode and held non-permanently therein. Thereby, the charged contaminants are removed from the aqueous media present between the electrodes.

[0043] The Applicant has further in European patent no. EP 3642 165 disclosed use of a third electrode 7 arranged between the two primary electrodes 2, 3. The third electrode 7 comprises a connection means 8 enabling the third electrode 7 to be electrically grounded. As is understood, ion removal and capacity is proportional to the distribution and strength of the electric field generated at each of the primary electrodes 2, 3.

[0044] The third electrode 7 is in EP 3642 165 configured to be electrically grounded and the two primary electrodes 2, 3 are configured to be polarized with opposite charges with respect to the grounded third electrode 7. This ensures that the potential is divided substantially equally between the positive and negative electrodes, thus enabling symmetric removal capacities of negatively and positively charged contaminants which prevents unwanted changes in water pH and chemistry.

[0045] However, in embodiments discussed herein, the third electrode 7 is configured to be positively charged and is thus connected to a positive polarization of a power source.

[0046] Figure 2 schematically illustrates the electrical field of, and ion transport in, the prior art CDI device 10 of EP 3642 165 during operation. As illustrated in Figure 2, the third electrode 7 provides the CDI device with two electrical half-cells 12, 13, one on either side of the third electrode 7 (without causing any physical division of the device as described above). In the figure, the first electrode 2 is positively polarized and the second electrode 3 is negatively polarized with respect to the third electrode 7. It is however evident that the opposite can apply, i.e. that the first electrode 2 is negatively polarized and the second electrode 3 is positively polarized with respect to the third electrode 7.

[0047] Negatively charged species, in Figure 2 exemplified by chloride ions (C1-), are drawn to the positively polarized first electrode 2. Correspondingly, positively charged species exemplified by sodium ions (Na+), are drawn to the negatively polarized second electrode 3.

[0048] Figure 3 shows in a left-hand illustration a 3-electrode CDI device 20 operating according to the above description for Figure 1.

[0049] The CDI device 20 of Figure 2 comprises an outer housing 21 adapted to confine the aqueous media inside the CDI cell during the deionization process. The outer housing 21 may have a cylindrical configuration such that it comprises a first end surface 21a, an envelope surface 21b, and a second end surface (not shown) opposing the first end surface 21a.

[0050] The housing 21 comprises an inlet 29 through which the aqueous media is introduced into the CDI device 20, and an outlet 30 through with the aqueous media exits the CDI device 20 after the deionization. The inlet and outlet may be concentric with the central axis of the CDI device 20, however other configurations are also possible. It may alternatively be envisaged that the inlet 29 and the outlet 30 are arranged at the same end of the CDI device 20.

[0051] The CDI device 20 further comprises a first electrode 22 and a second electrode 23 (i.e. the primary electrodes) energized via conductors 25 and 26.

[0052] The right-hand illustration shows a cross-section of the CDI device 20 taken along the line B-B where water to be cleaned flows through the cylindrically shaped CDI device 20 entering at inlet 29 and exiting at outlet 30.

[0053] The first electrode 22 and the second electrode 23 are wound about each other inside the cylindrical CDI device 20 and thus forms a circular cross-section. Further, the CDI device 20 comprises at least one electrically non-conductive spacer arranged in the space 24 between each turn of the electrodes around the central axis in order to avoid electrical short-circuiting between the first electrode 22 and the second electrode 23.

[0054] During operation of the CDI device 20, negatively charged contaminants are attracted to the positive electrode and held-non-permanently in the positive electrode (i.e. to the first electrode 22 or the second electrode 23 depending on the energization). Simultaneously, positively charged contaminants are attracted to thenegative electrode and held-non-permanently therein. Thereby, the contaminants are removed from the water flowing through the CDI device 20 hence cleaning the water. As discussed, the CDI device 20 may further optionally comprise the third electrode 27 grounded via conductor 28 for serving the purpose of enabling control and distribution of the energy substantially equally between the first electrode 22 and the second electrode 23.

[0055] Occasionally, the positive and negative contaminants in water - i.e. the water waste - temporarily held by the electrodes of the CDI cells must occasionally be released and flushed from the CDI device in order to prevent excessive accumulation of the contaminants at the electrodes, since such accumulation will decrease the contaminants removal capacity of the CDI device 40. This process is referred to as regeneration.

[0056] During regeneration of a CDI cell, the positive polarity will be removed for the first electrode 2 while the negative polarity will be removed for the second electrode 3 (and they may both be connected to the third electrode 7 which is connected to circuit ground; in other words the three electrodes will be short- circuited with each other). As a result, the positive and negative contaminants will be released from the respective electrode.

[0057] Figure 4a illustrates a front perspective exploded view of a CDI device 40 according to an embodiment. This particular CDI device 40 is arranged with both inlet 41 and outlet 42 through the same pipe at a front end covered by a front end plate 43. Thus, the pipe will be switched from serving as an inlet 41 to serving as an outlet 42 and vice versa.

[0058] The CDI device 40 further comprises a cylindrically shaped main body 44 accommodating a plurality of CDI cells.

[0059] The main body 44 is closed at a back end by a back cover plate 45 to which a back end plate 45 is attached by means of fasteners such as screws 54. The back end plate 46 is arranged with a cavity in which a processing device (CPU) 47, e.g. a microprocessor, is accommodated, to which CPU 47 CDI cell electrode conductors 48 are connected via through-holes 49.

[0060] Alternatively, the processing device may be embodied in the form of a field-programmable gate array (FPGA) a complex programmable logic device (CPLD), an application-specific integrated circuit (ASIC), etc.

[0061] In this example, an I / U sensor 50 is further arranged in the cavity of the back end plate 46 for measuring voltage and / or current of the conductors 48 and possibly also the amount of power being supplied to the individual CDI cells and the whole CDI device 40, as will be described.

[0062] The CPU 47 may further be connected to a wireless communication receiver and / or transmitter, such as a transceiver 51, for communicating with a remotely located device such as a smart phone (not shown). As previously mentioned, the CDI device 40 may in an embodiment be capable of receiving configuration instructions from the user via the smart phone and the transceiver 51 which are forwarded to the CPU 47.

[0063] The CDI 40 may further comprise a control interface (CI) 53, such as a touch screen or a keypad and display, via which a user may enter configuration instructions to the CPU 47 for configuring the cells as desired.

[0064] The CDI device 40 may comprise an internal power source (PS) 55, for instance located in the cavity of the back end plate 46 which in an embodiment may be configured to at least partly power the CDI device 40.

[0065] Figure 4b illustrates a back perspective exploded view of the CDI device 40 of Figure 4a according to an embodiment.

[0066] As illustrated, the main body 51 of the CDI device 40 accommodates a multitude of CDI cells 56. In this exemplifying embodiment, the CDI device 40 comprises 18 cells, but any appropriate number may be envisaged depending on application. Further shown is an interface 57 to an external power supply arranged at a back face of the back end plate 46. It may be envisaged that the internal power source 55 may be charged by an external power source via the interface 57.

[0067] In an embodiment, rather than connecting the CDI central electrode to ground as illustrated in the prior art CDI device of Figures 1 and 2, the CDI central electrode is connected to positive polarity.

[0068] Figure 5a thus illustrates the prior art configuration discussed hereinabove where the central electrode 7 is connected to ground. In this example, the firstelectrode 2 is selected as anode and connected to the positive terminal of DC supply 66, while the second electrode 3 is selected as cathode and connected to the negative terminal of the DC supply 66. As is understood, in embodiments, the internal power source 55 may replace or complement the DC supply 66.

[0069] Figure 5b illustrates an embodiment of the invention utilizing a configuration where the central electrode 77 and the anode represented by the first electrode 72 is connected to the positive terminal of the DC supply 66, while the cathode represented by the second electrode 73 is connected to the negative terminal of the DC supply 66.

[0070] Advantageously, this has as an effect that electrode operational life is elongated by reduction of material oxidation. It should be noted that oxidation only occurs at the positively charged anode electrode 2, 72.

[0071] The oxidation of the anode electrode 2, 72 is a function of the magnitude of voltage being applied to said electrode. By connecting both the anode electrode 72 and the central electrode 77 to positive polarity, effectively two anode electrodes are created with twice the mass of the anode electrode utilized in the prior art configuration of Figure 5a.

[0072] Assuming for instance that the power supply 66 applies a voltage of 1V across the CDI cell; in the symmetrical prior art structure of Figure 5a, 0.5V will be applied over the anode electrode 2 and 0.5V will be applied over the cathode electrode 3 (with the central electrode 7 grounded at oV).

[0073] However, in the asymmetrical structure of the embodiment illustrated in Figure 5b, if the power supply 50 applies a voltage of 1V across the CDI cell, the positive 0.5V being applied will be divided by the anode electrode 72 and the (positively charged) central electrode 77 such that 0.25V is applied over each of the anode electrode 72 and the central electrode 77, while 0.5V still will be applied over the cathode electrode 73.

[0074] Thus, the voltage applied is advantageously distributed over a greater volume of carbon, i.e. over twice the carbon mass embodied by the anode electrode 72 and the central electrode 77 taken together, which reduces the voltage over the anode electrode 72 by 50% and hence roughly doubles the lifetime of the anode electrode 72 given the reduction in oxidation.

[0075] Further, in an embodiment, the anode 72, cathode 73 and central electrode 77 are made of the same material.

[0076] Figures 6a and 6b illustrate a further embodiment where a switching circuitry 60 is provided in order to handle any reversing of polarity of the power supply occurring during deionization of water in the CDI device 40.

[0077] In this embodiment, the switching circuitry 60 comprises five relays for attaining the switching, where the 1stand 2ndleft-most relays are used for polarity reversal, while the next 3rdand 4th relays determine whether deionization or regeneration is to be performed. The 5th relay to which the 3rdelectrode 77 is connected since a serial configuration of CDI cells is utilized instead of parallelly connected CDI cells, as will be discussed in more detail. Thus, the switching circuity 60 is embodied by five relays to providing switching functionality by means of first switch 61, second switch 62, third switch 63, fourth switch 64 and fifth switch 65.

[0078] In the Figures, common relay terminology is used: Normally Closed (NC), Normally Open (NO), while the common (COM) connection is the part of the relay that that moves, i.e the switch.

[0079] Thus, Figure 6a illustrates deionization being performed in a first deionization state with positive charge applied by DC power source 66 to the first electrode 72 and negative charge applied to the second electrode 73.

[0080] A second deionization state with negative charge applied to the first electrode 72 and positive charge applied to the second electrode 73 will be described below with refence to Figure 6b.

[0081] In this embodiment, since deionization is performed, 3rdand 4threlays are always on, i.e. the third switch 63 and the fourth switch 64 are switched to NO.

[0082] Further, 1stand 2ndrelay determine what polarity is applied by the DC source 66 to the third switch 63 and the fourth switch 64.

[0083] In other words, in the first deionization state illustrated in Figure 6a, the first switch 62 is connected to positive charge and the second switch 62 is connected to negative charge, which results in the third switch 63 being connected via the first switch 61 to positive charge while the fourth switch 64 is connected via the second switch 62 to negative charge.

[0084] Hence, the first electrode 72 is connected via the third switch 63 and the first switch 61 to positive charge, while the second electrode 73 is connected via the fourth switch 64 and the second switch 62 to negative charge.

[0085] Further, 5threlay is on (i.e. the fifth switch 65 is connected to NO) thereby connecting the third electrode 77 via the fifth switch 65 to the first electrode 72 and thus to positive charge.

[0086] Now, if the user would reverse the polarity (accidentally or purposedly) of the power supply 66, thereby configuring the first electrode 72 as cathode and the second electrode 73 as anode (i.e. the opposite of the configuration of Figure 6a), the switching circuitry 60 would advantageously be controlled to adapt to such polarity reversing as will be described in the following, thereby connecting the third central electrode 77 to positively charged second electrode 73 rather than the negatively charged first electrode 72. In an embodiment, the CPU 47 detects such reversal of polarity of the power supply 66 and controls the switches 61-65 accordingly to adapt to the polarity reversal.

[0087] Further, the CDI device 40 may in an embodiment be configured to continuously switch the polarity of the power source 66, in which case the control scheme is configured such that the deionization is performed by continuously having the switches 61-65 of the relays correspondingly switch between the first and the second deionization state with the switching of the polarity of the power supply 66.

[0088] Thus, by repeatedly reversing the polarity of the first electrode 72 and the second electrode 73 (in the manner illustrated in Figures 6a and 6b) in each subsequent cycle, the operational life of the anode electrode can advantageously be elongated by a factor 2 as compared to having the anode electrode connected to positive polarity at all times. In addition, as discussed hereinabove, the new powering concept proposed in embodiments will further reduce oxidation of the anode electrode by half due to lower voltage at the anode electrode. Hence, taking both these embodiments into account, it is advantageously possible to elongate the operational life of the anode electrode by a factor 4 by means of the reduced oxidation being achieved.

[0089] In an embodiment, the CPU 47 handles the switching of the polarity of the power source 66 and simultaneously control the switches 61-65 to correspondingly switch between the first and the second deionization state.

[0090] Thus, Figure 6b illustrates deionization being performed in a second deionization state with negative charge applied by DC power source 66 to the first electrode 72 and positive negative charge applied to the second electrode 73. As is understood, the end result of the deionization is the same regardless of whether the CDI device 40 is in the first or second deionization state.

[0091] Again, since deionization is performed, 3rdand 4threlays are always on, i.e. the third switch 63 and the fourth switch 64 are switched to NO.

[0092] Further, 1stand 2ndrelay determine what polarity is applied by the DC source 66 to the third switch 63 and the fourth switch 64.

[0093] In other words, in the second deionization state illustrated in Figure 6, the first switch 62 is connected to negative charge and the second switch 62 is connected to positive charge, which results in the third switch 63 being connected via the first switch 61 to negative charge while the fourth switch 64 is connected via the second switch 62 to positive charge.

[0094] Hence, the first electrode 72 is connected via the third switch 63 and the first switch 61 to negative charge, while the second electrode 73 is connected via the fourth switch 64 and the second switch 62 to positive charge.

[0095] Further, 5threlay is off (i.e. the fifth switch 65 is connected to NC) since due to reversed polarity thereby the fifth switch 65 will connect the third electrode 77 to the second electrode 73 and thus to positive charge.

[0096] To conclude, the first and second deionization states illustrated in Figures 6a and 6b, a switching circuitry 60 is provided via which the first electrode 72, second electrode 73 and third electrode 77 is connected to the power supply 66 applying the charge to the first, second and third electrodes.

[0097] Advantageously, the switching circuitry 60 is configured to be controlled to selectively apply a positive charge to the first electrode 72 and a negative charge to the second electrode 73 in the first deionization state, and a negative charge to the first electrode 72 and a positive charge to the second electrode 73 in the seconddeionization state, while maintaining a positive charge on the third electrode 77 in both the first and the second deionization state.

[0098] Hence, irrespective of any reversal of the polarity of the voltage applied across the CDI cell, the central third electrode 77 will advantageously always be connected to the positive voltage supply.

[0099] Figure 7 illustrates an embodiment where regeneration of the CDI cells are undertaken.

[0100] During regeneration, 3rdand 4threlays are shorted to each other. In other words, the third switch 63 is connected to the fourth switch 64 via NC of the respective relay. As a result, the first electrode 72 and second electrode are interconnected via the third switch 63 and the fourth switch 64, thereby shorting the first electrode 72 and the second electrode 73.

[0101] As is understood, since 3rdand 4threlays are shorted to each other in the regeneration state, it does not matter how 1stand 2ndrelays are switched.

[0102] As can be seen, depending on switch status of the fifth switch 65, either the third switch 63 is connected to the fifth switch 65 (via NO) or the fourth switch 64 is connected to the fifth switch 65 (via NC).

[0103] Thus, in the regeneration state, the third electrode 77 is shorted via the fifth switch 64 either to the first electrode 72 via NO or to the second electrode 73 via NC and all three electrodes are shorted to each other.

[0104] To conclude, in the regeneration state, the switching device 60 is configured to be controlled to cause a short circuit of the first electrode 72, second electrode 73 and third electrode 77.

[0105] As previously mentioned, a reason for having the 5threlay is that in an embodiment, the cells of the CDI device 40 are configured in a series configuration.

[0106] Figure 8 illustrates six CDI cells being connected in series in an embodiment. As is understood, any appropriate number of CDI cells may be connected in series (such as the 18 CDI cells shown in Figure 4b), but for brevity six CDI cells are illustrated in Figure 8. Further, another row of CDI cells configured in series may be connected in parallel with the row of series-connected CDI cells of Figure 8.

[0107] In the series configuration, the first switch 61, second switch 62, third switch 63 and fourth switch 64 are commonly utilized by all CDI cells in the series configuration while each cell is connected to its own individual fifth switch 65. As is understood, the control of the switches 61-65 during deionization / regeneration is the same as that already described with reference to Figures 6a, 6b and 7.

[0108] If another row of series-connected CDI cells are connected to the row of cells in Figure 8, these will also share the first switch 61, second switch 62, third switch 63 and fourth switch 64 with the other series-connected cells, but have its own individual fifth switch 65.

[0109] As shown in Figure 8, the series of cells are formed by connecting the second electrode 73 of a cell in the series to the first electrode 72 of the next cell in the series.

[0110] If each cell was powered individually, as is the case in parallel configuration, the fifth switch 65 would not be required to switch the polarity of the third electrode 77 (as it can be always connected to positive charge of the power supply).

[0111] Also, the fifth switch 65 advantageously ensures that the third electrode 77 of each CDI cell in the series configuration receive the exact same voltage as the first and last electrode in the series, since the voltage may decrease with each CDI cell in the series.

[0112] An advantage of utilizing a series configuration for the CDI cells is that the current consumption of the CDI device 40 becomes far lower as compared to a parallel configuration. For instance, if with reference to Figure 8 six cells would have been connected in parallel where the six cells together would consume a current of 6A, the series configuration of Figure 8 will consume only 1A. In another example, if 12 cells would have been connected in parallel where the 12 cells together would consume a current of 12A, one row of six cells connected in series in its turn connected in parallel with another row of six cells in series will consume 2A.

[0113] In an embodiment, a microcontroller may measure the voltage polarity of the power supply 66 being connected to a port 57 of the CDI device 40 and control the switching circuitry 60 accordingly to control the switches 61-65 depending on how the power supply is connected to the port, thereby advantageously ensuring thatthe central electrode 77 always is connected to the positive polarity of the power supply 66 in order to provide an anode (i.e. effectively the combination of the anode electrode and the central electrode) having twice the mass as that of the prior art configuration.

[0114] Hence, irrespective of any reversal of the polarity of the voltage applied across the CDI cell, the central third electrode 77 will advantageously always be connected to the positive voltage supply.

[0115] The aspects of the present disclosure have mainly been described above with reference to a few embodiments and examples thereof. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

[0116] Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Claims

CLAIMS1. A capacitive deionization device (40) having at least one cell comprising a first electrode (72) and a second electrode (73), the second electrode (73) opposing the first electrode (72), wherein the device further comprises a third electrode (77) arranged between the first electrode (72) and the second electrode (73), the third electrode (77) configured to allow a flow of aqueous media from a first side of the third electrode (77) facing the first electrode (72) to a second side of the third electrode facing the second electrode (73), wherein the third electrode (77) and one of the first electrode (72) and the second electrode (73) are configured to be positively charged, while another one of the first electrode (72) and the second electrode (73) is configured to be negatively charged.

2. The capacitive deionization device (40) of claim 1, further comprising: a switching circuitry (60) via which the first electrode (72), second electrode (73) and third electrode (77) is connected to a power supply (66) applying the charge to the first, second and third electrodes, wherein the switching circuitry (60) is configured to be controlled to selectively apply a positive charge to the first electrode (72) and a negative charge to the second electrode (73) in a first deionization state and, a negative charge to the first electrode (72) and a positive charge to the second electrode (73) in a second deionization state, while maintaining a positive charge on the third electrode (77) in both the first and the second deionization state.

3. The capacitive deionization device (40) of claim 2, the switching device (60) further being configured to be controlled to cause a short circuit of the first electrode (72), second electrode (73) and third electrode (77) in a regeneration state.

4. The capacitive deionization device (40) of claims 2 or 3, the switching device(60) comprising: a first switch (61) connected in the first deionization state to positive charge; a second switch (62) connected in the first deionization state to negative charge; a third switch (63) connected in the first deionization state via the first switch(61) to positive charge;a fourth switch (64) connected in the first deionization state via the second switch (62) to negative charge; and a fifth switch (65) connected in the first deionization state via the third switch(63) and the first switch (61) to positive charge, wherein the first electrode (72) is connected in the first deionization state via the third switch (63) and the first switch (61) to positive charge; the second electrode (73) is connected in the first deionization state via the fourth switch (64) and the second switch (62) to negative charge; and the third electrode (77) is connected in the first deionization state via the fifth switch (65) to the first electrode (72).

5. The capacitive deionization device (40) of any one of claims 2-4, wherein: the first switch (61) is connected in the second deionization state to negative charge; the second switch (62) is connected in the second deionization state to positive charge; the third switch (63) is connected in the second deionization state via the first switch (61) to negative charge; the fourth switch (64) is connected in the second deionization state via the second switch (62) to positive charge; and the fifth switch (65) is connected in the second deionization state via the fourth switch (64) and the second switch (62) to positive charge, wherein the first electrode (72) is connected in the second deionization state via the third switch (63) and the first switch (61) to negative charge; the second electrode (73) is connected in the second deionization state via the fourth switch (64) and the second switch (62) to positive charge; and the third electrode (77) is connected in the second deionization state via the fifth switch (65) to the second electrode (72).

6. The capacitive deionization device (40) of claim 3, wherein: the third switch (63) is connected in the regeneration state to the fourth switch(64); and either, depending on switch status of the fifth switch (65): the third switch (63) is connected in the regeneration state to the fifth switch(65); or the fourth switch (64) is connected in the regeneration state to the fifth switch (65); wherein the first electrode (72) and the second electrode (73) are interconnected in the regeneration state via the third switch (63) and the fourth switch (64); and the third electrode (77) is connected in the regeneration state to the fifth switch (65), and either to the first electrode (72) or the second electrode (73) depending on switch status of the fifth switch (65), thereby causing short circuiting of the first, second and third electrodes.

7. The capacitive deionization device (40) of claim 4, wherein a plurality of capacitive deionization device cells are connected in series, and the first, second, third and fourth switch (61-64) are commonly utilized by the plurality of cells, the third switch (63) being connected to the first electrode (72) of a first cell in the series of cells and the fourth switch (64) being connected to the second electrode (73) of a last cell in the series of cells, wherein the series of cells are formed by connecting the second electrode (73) of a cell in the series to the first electrode (72) of the next cell in the series, and each cell is connected to an individual fifth switch (65).

8. The capacitive deionization device (40) of any one of claims 2-7, further comprising: a processing device (47) configured to detect polarity of the power supply (66) and control the switching of the switching circuitry (60) for connecting the third electrode (77) to the positive polarity of a power supply (66).

9. The capacitive deionization device (40) of claim 8, the processing device (47) being configured to continuously switch the polarity of the power supply (66), and further to control the switches (61-65) to correspondingly switch between the first and the second deionization state with the switching of the polarity of the power supply (66).

10. The capacitive deionization device (40) of any one of claims 2-9, further comprising: an interface (57) to which the power supply (66) is configured to be connected.

11. The capacitive deionization device (40) of any one of claims 2-10, further comprising: an internal power source (55) configured to at least partly power the capacitive deionization device (40).

12. The capacitive deionization device (40) of claim 11, the internal power source (55) being configured to be chargeable by the power supply (66) via the interface (57).

13. The capacitive deionization device (40) of any one of the preceding claims, the processing unit (42) being a microprocessor, a field-programmable gate array, FPGA, a complex programmable logic device, CPLD, or an application-specific integrated circuit, ASIC.

14. The capacitive deionization device (40) of any one of the preceding claims, wherein the first, second and third electrodes (72, 73, 77) are made of carbon or a carbon-based material, preferably an activated carbon cloth, a graphite plate or one or more graphene sheets.

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