System and method for producing water from air

Abstract

Embodiments of the present disclosure may include a system for absorbing water from air comprising moisture, the air representing a first water source. The system includes a water absorption device configured to absorb water from the first water source using a liquid desiccant such that a water concentration of the liquid desiccant may be increased. Embodiments may also include an evaporation device operatively connected to the water absorption device and configured to receive liquid desiccant in order to evaporate absorbed water from the received liquid desiccant to produce regenerated liquid desiccant and water. In some embodiments, the regenerated liquid desiccant has a lower water concentration than the received liquid desiccant. Embodiments may also include a water inlet configured to operatively connect a second water source to the evaporation device and / or the water absorption unit.

Description

[0001] SYSTEM AND METHOD FOR PRODUCING WATER FROM AIR

[0002] The present patent disclosure concerns a system and method for producing water from air.

[0003] In regions where water is scarce, such as regions with a relatively dry climate, it is possible to obtain water from air using a system for absorbing water from air. This is known in general as atmospheric water harvesting. Such systems may comprise a water absorption device, such as water absorption devices configured to absorb water from air using a liquid desiccant. The liquid desiccant with absorbed water is then typically fed to an evaporation device to remove the water and to regenerate the liquid desiccant. The regenerated liquid desiccant can then be used again in the water absorption device to absorb water. The water obtained by the evaporation device may thereafter be used in various processes of the process industry, such as in the chemical industry, pharmaceutical industry, or food processing industry.

[0004] For example, systems for producing water from air may be provided at, or integrated in, chemical sites or food processing sites. The water that is produced may be used, for example, as a solvent or reactant, or for cooking, cleaning or processing food.

[0005] Sometimes, however, the relative humidity of the air may be too low for the absorption device to obtain sufficient water from the air. Also, sometimes there is no need for water to be produced. In this case, the system for producing water from air is stopped, which is impractical within the processing industry where processes are often continuous and start up and shut down take time and result in suboptimal processing conditions.

[0006] It is an object, among objects, to provide for an improved system and method for producing water from air.

[0007] To this end, in accordance with a first aspect, there is provided a system for producing water from air comprising moisture, the air representing or being a first water source. The system includes a water absorption device configured to absorb water from the first water source using a liquid desiccant such that a water concentration of the liquid desiccant may be increased. Embodiments may also include an evaporation device operatively connected to the water absorption device and configured to receive liquid desiccant in order to evaporate absorbed water from the received liquid desiccant to produce regenerated liquid desiccant and water The evaporation device may comprise a first water outlet arranged to output the produced water. In some embodiments, the regenerated liquid desiccant has a lower water concentration than the received liquid desiccant. Embodiments may also include a water mlet configured to operatively connect a second water source to the evaporation device and / or the water absorption unit. In some embodiments, the system may be configured to increase the water concentration of the liquid desiccant using the water inlet. The second water source may be the water originating from the first water outlet of the evaporation device or it may be a different water source, such as from a processing system in which the produced water is used.

[0008] The system advantageously allows for changing the concentration of the liquid desiccant going to the evaporation device independent from the amount of water entering the liquid desiccant at the water absorbing device. In this way, it becomes possible to keep the evaporation device online while the water absorption device is offline or produces little, or insufficient, water. This is especially beneficial since startup and shutdown are preferably avoided in the evaporation device. In addition, when the system for producing water is operatively connected to another processing system, which takes the produced water as an input, this beneficially allows the other processing system to still receive water produced by the evaporation device even if the absorbing device is not producing any water, such that neither of the systems will have to be shut down completely.

[0009] It will be understood that air representing a first water source means the air comprises moisture, in other words, water vapor. The moisture or water vapor is absorbed by the absorber using the liquid desiccant.

[0010] In some embodiments, the system is an atmospheric water harvesting system or an atmospheric water generation system.

[0011] The system may comprise a plurality of water absorbing devices. There may be, for example, ten or more absorbing devices for each evaporation device. This beneficially allows for scaling up the quantity of water produced while needing a lower number of evaporation devices than the number of absorbing devices.

[0012] Embodiments may also include a controller configured to increase the water concentration of the liquid desiccant using the water inlet when one or more conditions may be met. In some embodiments, the one or more conditions may include one or more of the water concentration of the desiccant being below a threshold water concentration. In some embodiments, the one or more conditions may include the desiccant concentration being above a desiccant concentration threshold. In some embodiments, the one or more conditions include a relative humidity of the air being below a threshold relative humidity. In some embodiments, the one or more conditions include the absorber, or one or more of the plurality of absorbers, switching off.

[0013] In some embodiments, the controller may be configured to control the water inlet, which may be implemented as or comprise a valve.

[0014] In some embodiments, the liquid desiccant is a salt-based aqueous solution, wherein the threshold water concentration is at least 10%, preferably 20%, higher than a water concentration of the liquid desiccant at which the salt precipitates. In other words, the salt concentration is kept below the concentration of the maximum solubility of the salt in water. The maximum solubility changes with temperature. In some embodiments, the threshold water concentration is temperature dependent.

[0015] In some embodiments, the liquid desiccant is a potassium-acetate aqueous solution. When the liquid desiccant is a potassium-acetate aqueous solution, the threshold water concentration may be at least 28 wt% water per total weight of liquid desiccant. The threshold water concentration may lie in the range of 28 - 45 wt% water of a total weight of liquid desiccant. The threshold water concentration may be, for example, 29 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, or 42 wt%. These threshold water concentrations are suitable for potassium-acetate, keeping a balance between feeding liquid desiccant with an increased water content to the evaporation device and feeding liquid desiccant with a decreased water content to the absorber.

[0016] In some embodiments, the threshold water content may be about 30 wt% per total weight of liquid desiccant.

[0017] In some embodiments, for example when the liquid desiccant comprises glycerol, the threshold water content may lie in the range of 6-15%, preferably 7-12 wt%, of a total weight of liquid desiccant.

[0018] In some embodiments, the evaporation device is configured to heat the liquid desiccant using a non-ambient evaporation energy source. The non-ambient evaporation energy source may, for example, comprise or be electricity, concentrated solar heat, or a burnable fuel (e.g. hydrocarbon-based fuel, or hydrogen). Other heat may additionally be used, such as using a heat exchanger as described below, and / or from the gas being or comprising steam. With the term “non-ambienf ’, an energy source having an energy density that is higher than, for example, air at an ambient temperature having ambient humidity, and / or atmospheric conditions. In some embodiments, the evaporation device is configured to output the produced water as pure water. In other words, the evaporation device is configured to output only water from the first water outlet. “Pure water” and “only water” may indicate that the produced water is output as a stream comprising at least 90% by weight of water, or at least 95% by weight of water, or at least 99% by weight of water. The produced water may, in some embodiments, be potable water. The produced water may, in some embodiments, be in the form of liquid water, of steam, or both. In case liquid water is output, the system may in some embodiments further comprise a condenser to condense the evaporated water formed in the evaporation device.

[0019] In some embodiments, the evaporation device may comprise a gas inlet and may be configured to heat the received liquid desiccant using a gas including, or being, steam, such that at least the steam of the second gas may be condensed to form condensed water. In this way the sensible heat of the steam, as well as the heat of condensation of the steam, is used to heat the liquid desiccant to be regenerated.

[0020] In some embodiments, the evaporation device is implemented as a flash boiling device comprising a heat exchanger and a flash container, wherein the evaporation device is configured to first heat the liquid desiccant in the heat exchanger at elevated pressure by the steam and thereafter release the heated liquid desiccant into the flash container at lower pressure such that the water is boiled out of the liquid desiccant. The pressure in the heat exchanger results in the liquid desiccant to not boil within the heat exchanger.

[0021] In some embodiments, the evaporation device may include a second water outlet arranged to output the condensed water In some embodiments, the second water outlet may be operatively connected to the water inlet such that the system may be configured to increase the water concentration of the liquid desiccant using the condensed water.

[0022] In some embodiments, the evaporation device comprises a heat exchanger and an evaporator. The heat exchanger may be configured to transfer heat from the regenerated liquid desiccant coming from the evaporator to the liquid desiccant to be regenerated by the evaporator, forming pre-heated liquid desiccant. The heat exchanger may be configured to output the pre-heated liquid desiccant to the evaporator.

[0023] In some embodiments, the evaporator is configured to heat the liquid desiccant, such as the preheated liquid desiccant, such that water is evaporated from the liquid desiccant and the regenerated liquid desiccant is formed. In case the gas including the steam results in a mixture of fluids including the condensed water to exit the evaporation device, the system may comprise one or more separation devices to separate the condensed water from a remainder of fluids in the mixture of fluids. Alternatively, the gas may be steam. The steam may be filtered before it is used in the evaporation device using a filter device. The filter device may, for instance, be configured to remove other substances, such as oil, from the steam.

[0024] In some embodiments, the system for producing water is operatively connected to a processing system comprising a steam outlet, wherein the steam outlet is then the second gas including, or being, the steam. In some examples, the wet-bulb temperature has a wet-bulb temperature of at least 80 °C. The second gas may further comprise other gases such as oxygen, nitrogen, carbon dioxide, carbon monoxide, and argon. The processing system may be a food treatment system configured to heat food such that water is evaporated from the food to form the second gas including the steam The system for producing water from air is thus effectively and energy efficiently working together with the processing system, since waste heat from the processing system is used in the production of the water.

[0025] Embodiments may also include the food treatment system comprising a cleaning unit for cleaning food using the water produced by the evaporation device.

[0026] Embodiments may also include a liquid desiccant container operatively connected to the water absorption device in a first loop such that liquid desiccant may be able to flow from the liquid desiccant container to the water absorption device and from the water absorption device to the liquid desiccant container. In some embodiments, the liquid desiccant container is operatively connected to the evaporation device in a second loop such that liquid desiccant may be able to flow from the liquid desiccant container to the evaporation device and from the evaporation device to the liquid desiccant container and / or the first loop. In some embodiments, the water inlet may be operatively connected to the second loop, preferably between the liquid desiccant container and the evaporation device such that the water concentration of the liquid desiccant may be increased before the liquid desiccant flows into the evaporation device.

[0027] In some embodiments, the regenerated liquid desiccant may be fed directly to the first loop towards the absorption device. Beneficially, this increases the liquid desiccant concentration such that the absorbing device is able to more efficiently absorb moisture from the air.

[0028] When water is added to the liquid desiccant going to the evaporation device, the water concentration in the liquid desiccant container can be lower than the minimum water concentration required by the evaporation device. In turn, the absorber, receiving the liquid desiccant with lower water concentration from the container, or directly from the evaporation device, works more efficiently since lower concentration water in the liquid desiccant results in more moisture to be removed from the output air of the dryer.

[0029] Embodiments may include that the liquid desiccant is a salt-based aqueous solution.

[0030] Other embodiments may include that the liquid desiccant is a glycerol based aqueous solution

[0031] In some embodiments, the salt-based aqueous solution is selected from the group consisting of potassium acetate-based solution, calcium chloride-based solution, sodium sulfate-based solution, lithium bromide-based solution, potassium carbonate-based solution, sodium chloride-based solution, potassium chloride-based solution, magnesium chloride-based solution, calcium chloride-based solution, ammonium chloride-based solution, zinc chloridebased solution, lithium chloride-based solution, and iron chloride-based solution.

[0032] Embodiments of the present disclosure may also include a method for absorbing water from a first water source being a gas mixture including water, including absorbing water from the first water source using a liquid desiccant such that a water concentration of the liquid desiccant may be increased. Embodiments may also include evaporating absorbed water from the liquid desiccant to produce regenerated liquid desiccant and water. In some embodiments, the regenerated liquid desiccant has a lower water concentration than the received liquid desiccant. Embodiments may also include increasing the water concentration of the liquid desiccant using a second water source.

[0033] In some embodiments, the method may include repeating the absorbing using the regenerated liquid desiccant. Embodiments may also include increasing the water content of the liquid desiccant using the second water source when one or more conditions may be met.

[0034] In some embodiments, the one or more conditions may include one or more of the water content of the desiccant being below a threshold water content.

[0035] In some embodiments, the desiccant concentration being above a desiccant concentration threshold.

[0036] Embodiments may also include a relative humidity of the air being below a threshold relative humidity. In some embodiments, the increasing the water concentration of the liquid desiccant using the second water source may be done before the evaporating of the absorbed water from the liquid desiccant and after the absorbing of the water from the first water source . In some embodiments, the method may be performed in a system according to any one or more embodiments of the first aspect.

[0037] It will be understood that technical advantages and effects associated with features and / or embodiments of one aspect, apply to the corresponding, similar or equivalent features and / or embodiments of the otber aspects. It will also be apparent that the features of the various aspects and / or embodiments thereof may be applied to the other aspects and / or embodiments thereof

[0038] BRIEF DESCRIPTION OF THE FIGURES

[0039] The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of devices of the present disclosure. The above and other advantages of the features and objects of the disclosure will become more apparent, and the aspects and embodiments will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

[0040] Figure 1 is a block diagram illustrating a system for producing water, according to some embodiments of the present disclosure;

[0041] Figure 2 is a block diagram illustrating a system for producing water, according to some embodiments of the present disclosure;

[0042] Figure 3 is a block diagram illustrating a system for producing water, according to some embodiments of the present disclosure;

[0043] Figure 4 is a block diagram illustrating a system for producing water operatively connected to a processing system, according to some embodiments of the present disclosure;

[0044] Figure 5 is a schematic graph showing example data of produced water (kg / h) versus time, with the absorbing device periodically being switched off; and

[0045] Figure 6 is a flow chart illustrating a method for producing water, according to some embodiments of the present disclosure.

[0046] DETAILED DESCRIPTION

[0047] Referring to Figure 1, there is shown a first example of a system 1 for absorbing water from air. The air is represented by a first water source 2. System 1 comprises a water absorption device 10 configured to absorb water from the first water source 2 using a liquid desiccant such that a water concentration of the liquid desiccant is increased. The water absorption device 10 receives the air via an air inlet 12 and expels the air with reduced moisture level from the air outlet 14 to the ambient 6. Water absorption device 10 comprises a first liquid desiccant inlet 16 and a first liquid desiccant outlet 18.

[0048] The water absorption device 10 may be equipped with one or more fans for providing air flow. The water absorption device 10 may comprise absorption pads along which the liquid desiccant is able to flow. The air flows through or along the absorption pads and thus the moisture from the air is absorbed by the absorption pads. Examples of suitable absorption pads are GLasPad and CelPad 0760 from Hutek. Other types of absorbers are able to function in a similar way.

[0049] The system 1 further comprises an evaporation device 20 operatively connected to the water absorption device 10 and configured to receive liquid desiccant in order to evaporate absorbed water from the received liquid desiccant to produce regenerated liquid desiccant and water The evaporation device 20 comprises a first water outlet 26 arranged to output the produced water to a water destination 9. The regenerated liquid desiccant has a lower water concentration than the received liquid desiccant. The evaporation device 20 further comprises a second liquid desiccant inlet 22 and a second liquid desiccant outlet 24, which outputs the regenerated liquid desiccant. The liquid desiccant inlet 22 in this example receives liquid desiccant from the water absorption device 10 via liquid desiccant outlet 18. The liquid desiccant inlet 16 of the water absorption device 10 receives liquid desiccant from the evaporation device 20 via its liquid desiccant outlet 24.

[0050] The system 1 comprises a water inlet 30 configured to operatively connect a second water source 4 to the evaporation device and / or the water absorption unit, wherein the system is configured to increase the water concentration of the liquid desiccant using the water inlet 30. In this example, the system 1 is configured such that the water is introduced into the liquid desiccant flow going from the water absorbing device 10 to the evaporation device 20, at connection or junction 34. The water inlet 30 may be a valve, such as an electronically controlled valve. The water may alternatively be introduced directly into the liquid desiccant container 50.

[0051] As is shown in the example of Figure 2, the system 1 may comprise a controller 40 configured to increase the water content of the liquid desiccant using the water inlet 30 when one or more conditions are met. The one or more conditions may comprise one or more of the water concentration of the desiccant being below a threshold water concentration, the desiccant concentration being above a desiccant concentration threshold, a relative humidity of the air being below a threshold relative humidity.

[0052] In the example of Figure 2, the controller 40 is configured to control the water inlet 30, which may be implemented as or comprise a valve. This control is indicated with the arrow with double lines.

[0053] System 1 of Figure 2 further comprises a liquid desiccant container 0, functioning as a liquid desiccant buffer. The liquid desiccant container 50 is operatively connected to the water absorption device 10 in a first loop such that liquid desiccant can flow from the liquid desiccant container 50 via a third liquid desiccant outlet 54 to the first liquid desiccant inlet 16 of the water absorption device 10 and from the first liquid desiccant outlet 18 of the water absorption device 10 to a third liquid desiccant inlet 52 of the liquid desiccant container 50.

[0054] The liquid desiccant container 50 is operatively connected to the evaporation device 20 in a second loop such that liquid desiccant is able to flow from a fourth liquid desiccant outlet 56 of liquid desiccant container 50 to the evaporation device 20 and from the evaporation device 20 to the liquid desiccant container 50 and / or the first loop, as indicated with the dashed lines after connection 59. The liquid desiccant container 50 is here shown together with other features, such as the controller 40, but the liquid desiccant container 50 can be implemented in the example of Figure 1, wherein then the second loop would comprise the second liquid desiccant inlet 22 and second liquid desiccant outlet 24.

[0055] The presence of the liquid desiccant container 50 allows the liquid desiccant flow speed between the liquid desiccant container 50 and the water absorption device 10 to be different from the liquid desiccant flow speed between the liquid desiccant container 50 and the evaporation device 20.

[0056] In Figure 2, the evaporation device 20 comprises a heat exchanger 60 and an evaporator 62. The heat exchanger 60 is configured to transfer heat from the regenerated liquid desiccant coming from a fifth liquid desiccant outlet 75 of the evaporator 62 and received by seventh liquid desiccant inlet 65, to the liquid desiccant to be regenerated coming to the heat exchanger 60 via sixth liquid desiccant inlet 76. The pre-heated liquid desiccant is then output via the sixth liquid desiccant outlet 64 of the heat exchanger 60 towards the fifth liquid desiccant inlet 74 of the evaporator 62. The cooled regenerated liquid desiccant is output via regenerated liquid desiccant 65 towards the liquid desiccant container 50 or directly to the first loop and the water absorption device 10, via the seventh liquid desiccant outlet 77. The evaporation device 20 may be configured to heat the received liquid desiccant using a second gas comprising steam, such that at least the steam of the second gas is condensed to form condensed water. In this configuration, the evaporation device 20 comprises a water outlet which is operatively connected to the water inlet 30, via connection or valve 32, such that the system 1 is configured to increase the water concentration of the liquid desiccant using the condensed water. In Figure 2, the evaporator 62 comprises a steam inlet 72 and a condensed water outlet 73. The second gas comprising steam, or being steam, originates from the second water source 4. The water outlet 73 may output a remainder of the water to a water receiver or water destination 8, which may be a container, or may be a further processing system that takes water as an input. Water receiver 8 may also be part of a system comprising the second water source 4.

[0057] The evaporation device 20 may be implemented to heat the liquid desiccant using the steam by allowing the steam to pass through a heat transfer pipe which is submerged in the liquid desiccant. This may be an embodiment of the evaporator 62. The steam will then condense within the heat transfer pipe and heat the liquid desiccant in order to evaporate the water from the liquid desiccant.

[0058] As an alternative, according to some examples, the evaporator 62 may be implemented as a flash boiling device comprising a heat exchanger and a flash container (not shown). The liquid desiccant is first heated in the heat exchanger at elevated pressure by the steam, such that the liquid desiccant does not boil within the heat exchanger. Then, the heated liquid desiccant is released into the flash container at a lower pressure such that the water is able be boiled out of the liquid desiccant.

[0059] Figure 3 shows a system 1 similar to the one shown in Figure 2, except that there is provided a second heat exchanger 80 configured to receive liquid desiccant as a heat source via its liquid desiccant inlet 86. Heat is then transferred to another liquid, such as water, which is input via the second heat exchanger water inlet 82, and output via the second heat exchanger water outlet 84. The cooled liquid desiccant is output via the second heat exchanger liquid desiccant outlet 88 towards the heat exchanger 60. The second heat exchanger 80 receives warm regenerated liquid desiccant from the evaporator 62 in order to heat the other liquid that may be used in a processing system 7 connected to the system 1. For example, water may be (pre-) heated and used for washing or cooking of food items, when the processing system is a food processing system. In this example, less heat is available for pre-heating the liquid desiccant coming into heat exchanger 60 to be heated before going to the evaporator. This means that, for the same amount of steam input into the evaporator 62, less water can be absorbed by the water absorption device 10. This is because the liquid desiccant flowrate through the evaporator 62 is reduced and less water is produced, which in turn leads to a lower concentration of salt in the liquid desiccant, which in turn reduces the amount of water that the absorbing device is able to produce. In other words, in this embodiment, the evaporator 62 requires more steam to produce the same amount of water, since it requires more energy to reach the boiling point of the liquid desiccant. Overall, however, when the system 1 and the processing system work together, this heat recovery done with the second heat exchanger 80 is done in order to increase the overall efficiency of both systems together.

[0060] In the example of Figure 4, the system 1 is operatively connected to a food treatment system 400 comprising the second water source, wherein the food treatment system 400 is configured to heat food such that water is evaporated from the food to form the second gas 102 comprising the steam. The food treatment system 400 may comprise a fryer 100, for example. The fryer 100 comprises heated oil, which is heated by a heater (not shown). The fryer 100 could fry food, like potatoes to make chips or crisps, which releases water when being cooked. The water turns into steam and is expelled via outlet or chimney 102. The steam is filtered using filter device 91 to filter out unwanted substances, such as oil, before it enters the evaporator 62

[0061] The food treatment system 400 may further comprise a cleaning unit for cleaning food (not shown) using the water produced by the evaporation device. The cleaning unit is then in fluid communication with the water outlet 26 of the evaporation device 20 The cleaning unit is thus an embodiment of the water destination 9.

[0062] The water source 4, water destinations 8 and 9 may all be part of the same processing system, such as the food treatment system 400, such that the overall efficiency can be increased by the presence of the water production system 1. The processing system 7 may also be or be implemented in the food processing system 400.

[0063] The water inlet 30 is operatively connected to the second loop, in this example between the liquid desiccant container 50 and the evaporation device 20 such that the water concentration of the liquid desiccant is increased before the liquid desiccant flows into the evaporation device 20.

[0064] The liquid desiccant is a salt-based aqueous solution, wherein the threshold water concentration is at least 10%, preferably 20%, higher than a water concentration of the liquid desiccant at which the salt precipitates. When the liquid desiccant is a potassium-acetate aqueous solution, the threshold water concentration may lie in the range of 28 - 45 wt% water per total weight of liquid desiccant.

[0065] Figure 5 shows a graph of produced water in kg / h versus time. Two datasets are shown, the dataset 510 is for the system of Fig. 1 without water being fed by the water inlet 30 to the liquid desiccant going to the evaporation device 20, and the dataset 520 is for water being fed by the water inlet 30 to the liquid desiccant going to the evaporation device 20. The two datasets both have hills and valleys, wherein at the hills the absorbing device 10 is online and absorbing water, while in the valleys the absorbing device 10 is offline. As can be seen, beneficially, the dataset 520 shows that water is always produced by the evaporator. In this case, the produced water is about half when the absorbing device 10 is offline. In the dataset 510, however, it can be seen that no water is produced when the absorbing device 10 is offline. The average water productions for each dataset are also indicated. Dataset 10 has an approximate average 12, while dataset 520 has an approximate average 522. The average 522 is higher than the average 512.

[0066] As described in further detail below, dataset 520 may also apply to a situation where the air relative humidity is relatively low, and the water concentration in the liquid desiccant lowers and reaches the threshold water concentration (or, in other words, that the desiccant concentration in the liquid desiccant increases and reaches the threshold desiccant concentration). If the air relative humidity is not too low, then there is state of the system in which the absorber remains online, and water is added through the water inlet 30 at the same time in order to keep the water concentration of the liquid desiccant at a minimum level, such as 30%.

[0067] In Figure 6 is shown a flowchart of a method 600 for absorbing water from air, representing a first water source. The method comprises a step 610 of absorbing water from the first water source using a liquid desiccant such that a water concentration of the liquid desiccant is increased. The method 600 further comprises a step 620 of evaporating absorbed water from the liquid desiccant to produce regenerated liquid desiccant and water, wherein the regenerated liquid desiccant has a lower water concentration than the received liquid desiccant. The method 600 further comprises step 630 of increasing the water concentration of the liquid desiccant using a second water source.

[0068] The method 600 may comprise repeating the absorbing using the regenerated liquid desiccant. The method 600 may further comprise increasing the water content of the liquid desiccant using the second water source when one or more conditions are met. The one or more conditions comprise one or more of: the water content of the desiccant being below a threshold water content; the desiccant concentration being above a desiccant concentration threshold; and a relative humidity of the air being below a threshold relative humidity.

[0069] As will be understood, the water content of the desiccant and the desiccant concentration are interlinked, especially in case the liquid desiccant comprises substantially water and the desiccant, e g. one of the salts mentioned in the present patent disclosure or glycerol. The desiccant concentration (and thus also the water concentration) of the liquid desiccant flowing through the absorbing device is associated with a minimum relative humidity at which water is still absorbed in the absorbing device. The threshold relative humidity may thus be coupled to a threshold water and / or salt concentration. The threshold relative humidity may be higher than the minimum relative humidity, such as at least 5% higher than the minimum relative humidity. This may be a practical way to compensate for temperature changes of the air, of which the relative humidity changes with changing temperature.

[0070] As an example, when an aqueous solution of potassium acetate is used as the liquid desiccant, and the concentration of potassium acetate is 60% (and water concentration about 40%, in case no other substances, such as additives, are present in the liquid desiccant), gives an equilibrium relative humidity of about 38% for the absorbing device. The threshold relative humidity may be set to 38% or somewhat above that value, e.g 39% or 40%. If the relative humidity of the air is below that threshold relative humidity, the absorbing device may be stopped. Other examples include an equilibrium relative humidity of 35% when the concentration of potassium acetate is 62%, and an equilibrium relative humidity of 43% when the concentration of potassium acetate is 57%.

[0071] The controller may be configured to control based on the liquid desiccant salt concentration (or water concentration) in the following way. If the relative humidity of the air flowing through the absorbing device is relatively low, less water is absorbed from the air and the salt concentration of the liquid desiccant will start to increase since the water is continuously evaporated from the liquid desiccant by the evaporator. When the salt concentration reaches the threshold salt concentration (e.g. 62% (or some similar set value), water is added through water inlet 30 to regulate the salt concentration of the liquid desiccant to around 62%. Since the salt concentration is increased, it is an option that the absorbing device 10 is online and absorbing water from the air, while also water is added via the water inlet 30. It may be that the relative humidity of the air is so low, that the absorbing device 10 is offline and water is added via the water inlet 30. In both cases, the evaporator 20 can remain online. The increasing of the water concentration of the liquid desiccant using the second water source may be one before the evaporating of the absorbed water from the liquid desiccant and after the absorbing of the water from the first water source.

[0072] The method 600 may be performed using any one of the example systems 1 as shown in Figures 1 to 4.

[0073] The disclosure further comprises the following examples.

[0074] 1. System (1) for producing water from air, the air representing a first water source (2), the system (1) comprising: a water absorption device (10) configured to absorb water from the first water source (2) using a liquid desiccant such that a water concentration of the liquid desiccant is increased; an evaporation device (20) operatively connected to the water absorption device (10), wherein the evaporation device (20) is configured to receive liquid desiccant in order to evaporate absorbed water from the received liquid desiccant to produce regenerated liquid desiccant and water, wherein the evaporation device comprises a first water outlet (26) arranged to output the produced water, wherein the regenerated liquid desiccant has a lower water concentration than the received liquid desiccant; and a water inlet (30) configured to operatively connect a second water source (4) to the evaporation device and / or the water absorption unit, wherein the system is configured to increase the water concentration of the liquid desiccant using the water inlet (30).

[0075] 2. System according to example 1, wherein the system (1) comprises a controller (40) configured to increase the water content of the liquid desiccant using the water inlet (30) when one or more conditions are met.

[0076] 3. System according to example 2, wherein the one or more conditions comprise one or more of: the water concentration of the desiccant being below a threshold water concentration; the desiccant concentration being above a desiccant concentration threshold; and a relative humidity of the air being below a threshold relative humidity.

[0077] 4. System according to example 3, wherein the liquid desiccant is a salt-based aqueous solution, wherein the threshold water concentration is at least 10%, preferably 20%, higher than a water concentration of the liquid desiccant at which the salt precipitates.

[0078] 5. System according to example 3 or 4, wherein, when the liquid desiccant is a potassiumacetate aqueous solution, the threshold water concentration lies in the range of 28-45 wt% water per total weight of liquid desiccant.

[0079] 6. System according to any of the preceding examples, wherein the evaporation device (20) comprises a gas inlet (72) configured to receive a gas comprising steam, wherein the evaporation device (20) is configured to heat the received liquid desiccant using the gas comprising steam, such that at least the steam of the gas is condensed to form condensed water, wherein the evaporation device comprises a second water outlet (26) arranged to output the condensed water, wherein the second water outlet (26) is operatively connected to the water inlet (30) such that the system (1) is configured to increase the water concentration of the liquid desiccant using the condensed water.

[0080] 7. System according to example 6, wherein the system (1) is operatively connected to a food treatment system (400) comprising the second water source (4), wherein the food treatment system (400) is configured to heat food such that water is evaporated from the food to form the second gas (102) comprising the steam.

[0081] 8. System according to example 7, comprising a cleaning unit for cleaning food using the water produced by the evaporation device, wherein the cleaning unit is in fluid communication with a water outlet of the evaporation device

[0082] 9. System according to any one of the preceding examples, further comprising: a liquid desiccant container (50) operatively connected to the water absorption device (10) in a first loop such that liquid desiccant is able to flow from the liquid desiccant container (50) to the water absorption device (10) and from the water absorption device (10) to the liquid desiccant container (50), and the evaporation device (20) in a second loop such that liquid desiccant is able to flow from the liquid desiccant container (50) to the evaporation device (20) and from the evaporation device (20) to the liquid desiccant container (50) and / or the first loop.

[0083] 10. System according to example 9, wherein the water inlet (30) is operatively connected to the second loop, preferably between the liquid desiccant container (50) and the evaporation device (20) such that the water concentration of the liquid desiccant is increased before the liquid desiccant flows into the evaporation device (20); and / or wherein the liquid desiccant container (50) is configured to function as a liquid desiccant buffer.

[0084] 11. Method for absorbing water from air, the air representing a first water source (2), the method comprising: absorbing water from the first water source (2) using a liquid desiccant such that a water concentration of the liquid desiccant is increased; evaporating absorbed water from the liquid desiccant to produce regenerated liquid desiccant and water, wherein the regenerated liquid desiccant has a lower water concentration than the received liquid desiccant; increasing the water concentration of the liquid desiccant using a second water source

[0085] (4). 12. Method according to example 11, comprising repeating the absorbing using the regenerated liquid desiccant.

[0086] 13. Method according to example 11 or 12, comprising increasing the water content of the liquid desiccant using the second water source (4) when one or more conditions are met.

[0087] 14. Method according to example 13, wherein the one or more conditions comprise one or more of: the water content of the desiccant being below a threshold water content; the desiccant concentration being above a desiccant concentration threshold; and a relative humidity of the air being below a threshold relative humidity.

[0088] 15. Method according to any one of examples 11 to 14, wherein the increasing the water concentration of the liquid desiccant using the second water source (4) is done before the evaporating of the absorbed water from the liquid desiccant and after the absorbing of the water from the first water source (2).

[0089] 16. Method according to any one of examples 11 to 15, wherein the method is performed in a system (1) according to any one of examples 1 to 10.

[0090] Although the present invention has been described with reference to specific embodiments, also shown in the appended drawings, it will be apparent to those skilled in the art that many variations and modifications can be done within the scope of the invention as described in the specification and defined with reference to the claims below.

Claims

CLAIMS1. System (1) for producing water from air comprising moisture, the system (1) comprising: a water absorption device (10) configured to absorb water from the air using a liquid desiccant such that a water concentration of the liquid desiccant is increased; an evaporation device (20) operatively connected to the water absorption device (10), wherein the evaporation device (20) is configured to receive liquid desiccant in order to evaporate absorbed water from the received liquid desiccant to produce regenerated liquid desiccant and water, wherein the evaporation device comprises a first water outlet (26) arranged to output the produced water, wherein the regenerated liquid desiccant has a lower water concentration than the received liquid desiccant; and a water inlet (30) configured to operatively connect a second water source (4) to the evaporation device and / or the water absorption unit, wherein the system is configured to increase the water concentration of the liquid desiccant using the water inlet (30).

2. System according to claim 1, wherein the system (1) comprises a controller (40) configured to increase the water content of the liquid desiccant using the water inlet (30) when one or more conditions are met.

3. System according to claim 2, wherein the one or more conditions comprise one or more of: the water concentration of the desiccant being below a threshold water concentration; the desiccant concentration being above a desiccant concentration threshold; and a relative humidity of the air being below a threshold relative humidity.

4. System according to claim 3, wherein the liquid desiccant is a salt-based aqueous solution, wherein the threshold water concentration is at least 10%, preferably 20%, higher than a water concentration of the liquid desiccant at which the salt precipitates.

5. System according to claim 3 or 4, wherein, when the liquid desiccant is a potassium - acetate aqueous solution, the threshold water concentration lies in the range of 28-45 wt% water per total weight of liquid desiccant.

6. System according to any of the preceding claims, wherein the evaporation device (20) comprises a gas inlet (72) configured to receive a gas comprising steam, wherein the evaporation device (20) is configured to heat the received liquid desiccant using the gas comprising steam, such that at least the steam of the gas is condensed to form condensed water,wherein the evaporation device comprises a second water outlet (26) arranged to output the condensed water, wherein the second water outlet (26) is operatively connected to the water inlet (30) such that the system (1) is configured to increase the water concentration of the liquid desiccant using the condensed water.

7. System according to claim 6, wherein the system (1) is operatively connected to a food treatment system (400) comprising the water source (4), wherein the food treatment system (400) is configured to heat food such that water is evaporated from the food to form the second gas (102) comprising the steam.

8. System according to claim 7, comprising a cleaning unit for cleaning food using the water produced by the evaporation device, wherein the cleaning unit is in fluid communication with a water outlet of the evaporation device.

9. System according to any one of the preceding claims, further comprising: a liquid desiccant container (50) operatively connected to the water absorption device (10) in a first loop such that liquid desiccant is able to flow from the liquid desiccant container (50) to the water absorption device (10) and from the water absorption device (10) to the liquid desiccant container (50), and the evaporation device (20) in a second loop such that liquid desiccant is able to flow from the liquid desiccant container (50) to the evaporation device (20) and from the evaporation device (20) to the liquid desiccant container (50) and / or the first loop.

10. System according to claim 9, wherein the water inlet (30) is operatively connected to the second loop, preferably between the liquid desiccant container (50) and the evaporation device (20) such that the water concentration of the liquid desiccant is increased before the liquid desiccant flows into the evaporation device (20); and / or the liquid desiccant container (50) is configured to function as a liquid desiccant buffer.

11. Method for absorbing water from air (2) comprising moisture, performed in a system (1) according to any one of claims 1 to 10, the method comprising: absorbing water from the air (2) using a liquid desiccant such that a water concentration of the liquid desiccant is increased; evaporating absorbed water from the liquid desiccant to produce regenerated liquid desiccant and water, wherein the regenerated liquid desiccant has a lower water concentration than the received liquid desiccant;increasing the water concentration of the liquid desiccant using a water source (4).

12. Method according to claim 11, comprising repeating the absorbing using the regenerated liquid desiccant.

13. Method according to claim 11 or 12, comprising increasing the water content of the liquid desiccant using the second water source (4) when one or more conditions are met.

14. Method according to claim 13, wherein the one or more conditions comprise one or more of: the water content of the desiccant being below a threshold water content, the desiccant concentration being above a desiccant concentration threshold; and a relative humidity of the air being below a threshold relative humidity.

15. Method according to any one of claims 11 to 14, wherein the increasing the water concentration of the liquid desiccant using the second water source (4) is done before the evaporating of the absorbed water from the liquid desiccant and after the absorbing of the water from the air (2).

16. Method according to any one of claims 11 to 15, wherein the method is performed in a system (1) according to any one of claims 1 to 10.

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