Method for production of water from air based on low-temperature heat, and machine and system thereof

Abstract

A method for production of water from air includes cyclically and successively repeating the following two phases: a first phase a), which includes the following steps: a1) taking air from the outside, a2) conveying the air towards an enthalpic exchanger containing an adsorbent material that internally accumulates the moisture that is present in the air, a3) outputting dry air, and a second phase b), which includes the following steps: b1) supplying heat to the enthalpic exchanger by way of a low-temperature heat source, b2) conveying an air flow through the enthalpic exchanger, wherein the air in contact with the enthalpic exchanger is heated and at the same time collects the moisture contained in the adsorbent material, and b3) bringing the heated and humidified air flow to ambient temperature in order to cause the moisture contained therein to condense, thereby obtaining water.

Claims

1. A method for production of water from air, comprising cyclically and successively repeating the following two phases: a first phase a), which includes the following steps: a1) taking air from the outside, a2) conveying said air towards an enthalpic exchanger containing one or more surfaces and an adsorbent material in contact with said one or more surfaces, wherein said adsorbent material internally accumulates moisture that is present in said air, wherein said enthalpic exchanger comprises a plurality of lamellar panels and wherein said adsorbent material is applied onto said lamellar panels or is in granular form and is arranged between two adjacent lamellar panels of said enthalpic exchanger, a3) outputting dry air, and a second phase b), which includes the following steps: b1) supplying a quantity of sensible heat to said one or more surfaces of said enthalpic exchanger by means of a low-temperature heat source, thereby heating said adsorbent material of said enthalpic exchanger by conduction via contact between said one or more surfaces and said adsorbent material, b2) conveying an air flow through said enthalpic exchanger, wherein said air in contact with said enthalpic exchanger receives from said enthalpic exchanger (i) said quantity of sensible heat supplied by said low-temperature heat source to said one or more surfaces and said adsorbent material of said enthalpic exchanger and at the same time (ii) said moisture contained in said adsorbent material of said enthalpic exchanger, said quantity of sensible heat being such as to compensate for the temperature reduction caused by water evaporation at said adsorbent material in order to perform isothermal regeneration of said adsorbent material, and b3) bringing said air having received said quantity of sensible heat and said moisture from said enthalpic exchanger to ambient temperature in order to cause the moisture contained therein to condense, thereby obtaining water.

2. The method according to claim 1, wherein the second phase b) includes, between said step b2) and said step b3), an intermediate step b2.1) of recovering heat.

3. The method according to claim 2, wherein said intermediate step b2.1) of recovering the heat includes two steps: r1) heat recovery by means of an air/air exchanger, and r2) heat recovery by means of a liquid/air exchanger.

4. The method according to claim 3, wherein said intermediate step b2.1) of recovering the heat generates a closed cycle with recirculation of the air obtained after the steps of the second phase b), so as to recover the moisture still contained in the recirculating air.

5. The method according to claim 1, wherein two enthalpic exchangers are used, which work in parallel and in turn in the two phases a) and b), wherein in a first period of time the first enthalpic exchanger works in the first phase a) and the second enthalpic exchanger works in the second phase b), and in a second period of time the first enthalpic exchanger works in the second phase b) and the second enthalpic exchanger works in the first phase a).

6. The method according to claim 1, wherein said adsorbent material is in granular form and is arranged between two adjacent lamellar panels of said enthalpic exchanger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will be illustrated in the following detailed description, which is provided merely by way of non-limiting example with reference to the annexed drawings, wherein:

(2) FIG. 1 shows an exemplary conceptual scheme of the operation of the solution described herein, which comprises a phase a) and a phase b),

(3) FIG. 2 and FIG. 3 are two graphs of the thermodynamic cycle,

(4) FIG. 4 shows an example of a system composed of two machines alternately working in the two phases a) and b),

(5) FIGS. 5, 10 and 11 show an embodiment of the system of FIG. 4,

(6) FIGS. 6, 7, 8 and 9 show some elements constituting the system of FIG. 4.

DETAILED DESCRIPTION

(7) The following description will illustrate various specific details useful for a deep understanding of some examples of one or more embodiments. The embodiments may be implemented without one or more of such specific details or with other methods, components, materials, etc. In other cases, some known structures, materials or operations will not be shown or described in detail in order to avoid overshadowing various aspects of the embodiments. Any reference to “an embodiment” in this description will indicate that a particular configuration, structure or feature is comprised in at least one embodiment. Therefore, the phrase “in an embodiment” and other similar phrases, which may be present in different parts of this description, will not necessarily be all related to the same embodiment. Furthermore, any particular configuration, structure or feature may be combined in one or more embodiments as deemed appropriate.

(8) The references below are therefore used only for simplicity's sake, and do not limit the protection scope or extension of the various embodiments.

(9) The atmosphere, or rather the water contained therein, can be a solution to the above-mentioned problem.

(10) The atmosphere is a huge and widespread renewable resource of potable water, and it has been estimated to contain approx. 12,900 km.sup.3 of water in the form of water vapour. Since water is available in the vapour state, it is necessary to carry out a series of thermodynamic transformations in order to condense it into the liquid state.

(11) Air is a mixture of different gaseous substances, including water vapour. The quantity of water vapour in the air is defined by its partial pressure Pv.

(12) At given conditions of total air temperature and pressure, the partial pressure Pv does not exceed a limit value, called saturation pressure Ps.

(13) Relative humidity RH is defined as a percent ratio between these terms: RH=Pv/Ps.

(14) As temperature increases, the value of the saturation pressure Ps increases as well, thus improving the capability of containing water in vapour state.

(15) By approximating vapour to a gas, it is possible to apply the thermodynamic relations of perfect gases PV=nRT to determine the vapour mass, the temperature and pressure conditions being known.

(16) The parameter that defines the quantity of water per kilogram of air in specific terms is absolute humidity, indicated as “x”, the unit of measure being gr_H.sub.2O/Kg_air.

(17) For example, at a temperature of 35° C. and a relative humidity RH=20% (typical conditions of a dry climate), the air contains about 7 grams of water per kilogram of air (x=7).

(18) When the saturation condition is reached at the same temperature (35° C., 100%), specific humidity reaches 37 g/kg, i.e. x=37.

(19) If air is brought to 50° C., upon saturation it will contain approximately x=87 g/kg.

(20) On the contrary, in given conditions of temperature and partial pressure Pv, if some heat is subtracted, the temperature of the air mixture will progressively decrease and relative humidity RH will increase.

(21) When relative humidity RH=100% is achieved, the so-called dew point is reached.

(22) If more heat is subtracted, a condensation process will be activated, and water will switch from the vapour state to the liquid state.

(23) In conclusion, therefore, in order to extract water from air it is necessary to reach the dew point.

(24) Dry regions are characterized by a dew point in the range of 0-10° C. and an ambient temperature in the range of 30-45° C.

(25) The use of an electrically powered refrigeration machine for subtracting heat within this range of temperatures requires considerable energy consumption.

(26) By using specific components and materials, the solution proposed herein allows implementing a thermodynamic cycle that raises the dew point of the air to over 50° C.

(27) In this manner, the air flow can be condensed at ambient temperature, thus avoiding the use of refrigeration machines.

(28) The primary energy source of such a system is low-temperature heat, which is the most abundant and economical energetic resource that can be found.

(29) The solution described herein exploits the ability of some desiccant materials to capture water vapour from air.

(30) When these materials are brought in contact with ambient air, a dehumidification process is activated which transfers the water vapour from the air to the desiccant material.

(31) This vapour-capturing mechanism ends when local equilibrium conditions are reached, which define the saturation condition of the desiccant material.

(32) This process is reversible and it is possible, by supplying heat, to “regenerate” the desiccant or dehumidifying materials by removing the amount of water contained therein.

(33) In this case, a transfer of water vapour from the desiccant or dehumidifying material to the surrounding air will occur.

(34) Generally, heat is provided by the air itself, which is heated beforehand.

(35) In order to be able to receive vapour into its mixture, the air must yield some heat to the desiccant or dehumidifying material, and this implies a temperature reduction.

(36) This type of thermodynamic transformation is referred to as “isoenthalpic”, i.e. a transformation in which enthalpy remains constant.

(37) The air temperature reduction that occurs during the regeneration of the desiccant or dehumidifying materials reduces the saturation pressure Ps, and hence the water mass that can be contained in the mixture.

(38) The moist air flow obtained from the regeneration of the desiccant or dehumidifying material can be cooled down to its dew point in order to activate the condensation process and obtain water in the liquid state.

(39) In this case, the dew point will be higher than the temperature of the outside environment, because the hygrometric content of the air mixture will be greater than the atmospheric one.

(40) The invention proposed herein is based on the cycle of a machine for extracting liquid water as schematized in FIG. 1 and represented in the psychrometric diagram of FIG. 2.

(41) The solution according to the invention utilizes the alternation between two distinct phases, i.e. a) capturing water vapour from the atmosphere, or adsorption phase, and b) condensation of the captured vapour, or desorption phase.

(42) The phenomenon considered herein is adsorption, i.e. relating to a solid.

(43) Therefore, the proposed solution exploits the isothermal regeneration of the material that has adsorbed water, which isothermal transformation allows lowering the condensation temperature.

(44) During the adsorption phase a), the machine allows exchanging heat and mass at the same time, and an enthalpic exchanger EHX is brought in contact with the outside ambient air indicated as AIR (i.e. the atmosphere).

(45) The enthalpic exchanger EHX has a structure, which will be further described below, which is formed by a plurality of metal elements whereon an adsorbent (desiccant or dehumidifying) material is arranged, indicated as MAT_AD.

(46) The enthalpic exchanger EHX may also be made from other materials, e.g. high-conductivity plastic materials.

(47) In particular, the adsorbent material MAT_AD may be provided in granular form, in the form of panels that cover the metal elements of the exchanger EHX, or in the form of a paint or coating that coats the metal elements of the exchanger EHX.

(48) An air flow taken from the outside environment, i.e. from the atmosphere, laps the contact surface of the adsorbent material MAT_AD, i.e. the dehumidifying substance, which captures the water vapour thereof.

(49) For example, a fan FAN may be used in order to convey the air in the desired direction, i.e. towards the metal elements coated with adsorbent material MAT_AD of the enthalpic exchanger EHX.

(50) The air exiting the machine, obtained after the passage through the enthalpic exchanger EHX, can be either rejected into the environment or used for applications requiring dry air.

(51) The air can be moved by mechanical means (e.g. a fan or blower) and/or by exploiting the natural convection motions of air.

(52) The process carried out during the adsorption phase a) will then continue until the dehumidifying substance reaches the saturation condition in equilibrium with the ambient conditions.

(53) As an alternative, the process carried out during the adsorption phase a) may be interrupted earlier, in accordance with the machine control logics.

(54) In particular, the duration of phase a) will depend on the temperature of the air, the moisture contained therein, and the dimensions of the machine employed for extracting water from air.

(55) At the end of the adsorption phase a), the desorption phase b) will start.

(56) This desorption phase b) occurs at a low temperature, >50° C.

(57) To the same enthalpic exchanger EHX heat is supplied through a thermal vector or a heat source HS, e.g. a hot air flow, which allows the regeneration of the adsorbent material MAT_AD acting as a dehumidifying substance.

(58) In particular, the heat source HS heats an exchange fluid (such as air or a liquid) flowing and circulating in the enthalpic exchanger EHX.

(59) The heat source HS may be solar energy, heat extracted from biomasses, or waste heat generated in other processes.

(60) Therefore, a low-temperature (50° C.-80° C.) heat source HS is used.

(61) Water vapour is released from the adsorbent material MAT_AD and yielded to an air flow lapping its contact surface.

(62) The adsorbent material MAT_AD acting as a dehumidifying substance is in contact with a surface that also allows for exchanging sensible heat, e.g. the high-conductivity metal or plastic surface of the elements forming the enthalpic exchanger EHX.

(63) The heat supplied by the heat source HS goes through the adsorbent material MAT_AD by conduction and is transmitted to the same air stream.

(64) At the same time, this air stream receives a flow of sensible heat and a latent flow originated from the migration of the water from the adsorbent material MAT_AD to the air.

(65) The temperature of the air increases from the initial temperature, and so does specific humidity.

(66) The thermodynamic transformation undergone by the air can be represented in the psychrometric diagram as a steeper line of the isoenthalpic transformation shown in FIG. 3.

(67) With reference to FIG. 3, the following will describe the difference between isoenthalpic transformation and isothermal transformation.

(68) In FIG. 3, the line of the abscissas shows the temperatures (° C.) and the line of the ordinates shows the absolute humidity values (gH.sub.2O/kgair)

(69) In systems already patented which are based on the use of adsorbent materials, the air is subjected to a transformation that, basically, can be defined as isoenthalpic, i.e. wherein variations in the latent content (humidity) occur at the expense of the sensible content (temperature).

(70) This means that, when an adsorbent material is regenerated by exploiting an isoenthalpic transformation (line joining points P1-P2_H), the latent content, and hence the humidity, of the air will increase, while the sensible content, i.e. its temperature, will decrease.

(71) Conversely, the cycle presented herein is based on an isothermal, as opposed to isoenthalpic, material regeneration.

(72) This type of transformation offers a remarkable advantage, which can be intuitively guessed by comparing the two points P2_T (isothermal transformation) and P2_H (isoenthalpic transformation).

(73) Point P2_T reaches distinctly greater values of absolute humidity, approx. 87 g/kg versus approx. 43 g/kg of the isoenthalpic transformation, starting from a temperature of 50° C.

(74) Furthermore, in the isoenthalpic transformation case the sensible jump is really small (in the example, reference is made to an ambient temperature of 35° C.) in comparison with the isothermal transformation.

(75) Consequently, dimensions and space occupation, as well as the specific costs of the system per water mass unit produced, are reduced when the thermodynamic cycle is based on an isothermal regeneration rather than an isoenthalpic one.

(76) Still with reference to FIG. 1, the second desorption phase b) may include a first block HX_REC1 for heat recovery.

(77) In particular, the first block HX_REC1 receives the air exiting the enthalpic exchanger EHX, indicated as reference P2, recovers the heat, and outputs two flows: the first flow P1, which is sent back to the inlet of the enthalpic exchanger EHX, and an air flow P2_R, which is sent to a second heat recovery block HX_REC2.

(78) The air flow P2_R is sent to a second block HX_REC2 for heat recovery and, finally, to the condenser COND (heat sink), which condenses the water contained therein. At the inlet of the condenser COND there is the flow P3, which is condensed in a collection chamber.

(79) In various embodiments, the flow P3 is sent back to the inlet of the first heat recovery block HX_REC1 as a flow P4.

(80) The flows indicated in FIG. 1 by the symbols P1, P2, P3 and P4 are the air flows that are in the temperature and humidity conditions indicated in the psychrometric diagram of FIG. 2.

(81) In particular, in one embodiment the same enthalpic exchanger EHX operates for a first period of time in the first adsorption phase a) and for a second period of time in the second desorption phase b).

(82) If the quantity of sensible heat yielded to the air is such as to compensate for the temperature reduction caused by water evaporation, the transformation can be isothermal, i.e. at the same temperature, as shown in FIG. 3, and/or heated, as represented by the line that joins points P1-P2 in FIG. 2, if the quantity of sensible heat yielded is greater.

(83) The air flow can be moved mechanically, e.g. by means of a fan FAN, FIG. 1, and/or by natural convection.

(84) After having gone through the exchanger EHX, the flow arrives at point P2 and proceeds towards the condenser COND.

(85) At point P2 the air flow has reached such conditions of temperature and humidity that a considerable amount of water can be condensed at the condenser COND (heat sink), even while yielding heat to the ambient temperature, e.g. 35° C.

(86) For example, with an air flow of 100 m3/h it is possible to reach, at point P2, a temperature of 50° C. and a relative humidity of 100%.

(87) By condensing this flow at an ambient temperature of 35° C., a flow rate of liquid water of approx. 0.1 lt/min is produced.

(88) The air flow moves within a closed circuit and, after having gone through the condenser COND, at point P4, returns to the exchanger EHX (optionally after passing again through the first heat recovery block HX_REC1).

(89) Between the exchanger EHX and the condenser COND a dual heat recovery system is interposed: an air/air heat exchanger, indicated as HX-REC1 (see FIG. 7); and/or a liquid/air heat exchanger, indicated as HX-REC2 (see FIG. 8).

(90) The first heat recovery block HX-REC1 allows for thermal exchange between the air flow exiting HX-REC2, indicated as P2_R, and the air flow exiting the condenser COND, indicated as P4.

(91) Therefore, the temperature of the air flow entering the exchanger EHX is higher than the condensation temperature.

(92) The first heat recovery block HX-REC1 may be sized for reaching at most the temperature of point P2.

(93) The second heat recovery block HX-REC2 is located downstream of the first heat recovery block HX-REC1 and allows recovering the heat from the condensing flow to the medium that supplies the heat produced by the heat source HS.

(94) This recovery can take place, for example, by means of a closed water flow moved by the pump PUMP.

(95) The heat necessary for regeneration must be supplied at temperatures only slightly higher than the maximum regeneration temperature, which in the example is 50° C.

(96) This makes it also possible to use thermal solar systems, heat coming from thermal waste, or other low-temperature heat sources.

(97) When the dehumidifying substance, i.e. the adsorbent material MAT_AD, has been completely regenerated, the desorption phase b) will end and the adsorption phase a) will start again.

(98) As an alternative, the desorption phase b) may be interrupted earlier, in accordance with the system control logics.

(99) During the adsorption phase a) there is no production of liquid water from the same exchanger EHX.

(100) Therefore the air, as it flows through the machine, receives moisture from the adsorbent material (previously accumulated therein) and heat from the exchange fluid circulating in the exchanger EHX.

(101) The air flowing therethrough is not in direct contact with the exchange fluid, but there is a metal or plastic surface having high contact conductivity. In particular, said contact surface comprises pipes or ducts, in which the exchange fluid flows, and fins or lamellar panels. Lamellar panels provide a considerable increase in contact and exchange area.

(102) In various embodiments of the invention it is possible to consider a system made up of two machines, i.e. a system comprising two enthalpic exchangers EHX1 and EHX2, as shown in FIG. 4. In the exemplary embodiment, the two enthalpic exchangers EHX1 and EHX2 have the recovery blocks HX-REC1 and HX-REC2 and the condenser block COND in common.

(103) The system composed of the exchangers EHX1 and EHX2 is sized in such a way that the enthalpic exchange between the air and the dehumidifying substance will be continuous and extended for a long period of time.

(104) In particular, with reference to FIG. 4, in the left-hand portion (A) the exchanger EHX1 is executing the second desorption phase b) and the exchanger EHX2 is executing the first adsorption phase a). Conversely, in the right-hand portion (B) the exchanger EHX1 is executing the first adsorption phase a) and the exchanger EHX2 is executing the second desorption phase b).

(105) In this manner, there are no downtimes and the efficiency of liquid water production is increased.

(106) Therefore, in FIG. 4 (A) the exchanger EHX1 is executing the water condensation cycle and the exchanger EHX2 is executing the step of capturing vapour from air. Conversely, in FIG. 4 (B) the exchanger EHX1 is executing the step of capturing vapour from air and the exchanger EHX2 is executing the water condensation cycle.

(107) In order to ensure uninterrupted operation, the two exchangers EHX1 and EHX2 work in parallel in an alternate fashion.

(108) FIG. 5 shows, in schematic form, a configuration of a system that uses two exchanger EHX1 e EHX2 in alternate parallel operation, as already described in FIG. 4. In particular, all components are so arranged as to provide a compact system configuration.

(109) With reference to FIGS. 4 and 5, and to FIGS. 10 and 11, two air exchange valves VS1 and VS2 allow switching the beds 2, thus creating the closed circuit for the exchanger EHX in regeneration and putting the other exchanger EHX in communication with the outside environment.

(110) With reference to FIG. 4(A), the valves VS1 and VS2 are in a position such that the exchanger EHX1 is in the desorption phase b), so that the exchanger EHX1 is insulated from the outside air, and the exchanger EHX2 is in the adsorption phase a), so that the exchanger EHX2 is in contact with the outside air.

(111) In FIG. 4(B), on the contrary, the valves VS1 and VS2 are in a position such that the exchanger EHX2 is in the desorption phase b), so that the exchanger EHX2 is insulated from the outside air, and the exchanger EHX1 is in the adsorption phase a), so that the exchanger EHX1 is in contact with the outside air.

(112) Therefore, in FIG. 4(A) the valve VS1 is closed for the exchanger EHX1 and open for the exchanger EHX2, and the valve VS2 is closed for the exchanger EHX1 and open for the exchanger EHX2.

(113) On the contrary, in FIG. 4(B) the valve VS1 is open for the exchanger EHX1 and closed for the exchanger EHX2, and the valve VS2 is open for the exchanger EHX1 and closed for the exchanger EHX2.

(114) Between the two exchangers EHX1 and EHX2, the first heat recovery block HX-REC1 is arranged. Downstream of the first recovery block HX-REC1 there are, in this order, the second heat recovery block HX-REC2, the condenser 12, and the condensed water collection tank 11 (see FIGS. 10 and 11).

(115) Water is collected into the tank 11 by dripping vertically from the condenser 12.

(116) The air is conveyed by means of converging bends and channels 14, and laps the two exchangers EHX1 and EHX2 to effect the above-mentioned transformations.

(117) If the air flows are moved mechanically, the fans 7 and 8 may be arranged close to the air exchange valves VS1 and VS2 (see FIGS. 5, 10 and 11).

(118) The components are sized for low load losses, and the maximum power of the fans 7 and 8 does not exceed 30 W. The fans 7 and 8 may be adjusted for treating a variable flow rate, in accordance with the control logics.

(119) As an alternative, the regeneration heat may also be exploited for activating natural convection motions that will induce an air flow through the components.

(120) Heat is supplied through an exchanger 5, which transmits the regeneration heat supplied by the heat source HS to the collectors 16 and distributed to the beds 2 through pipes 15.

(121) A pump 6 circulates hot water in the pipes 15, and valves 4 distribute the flow only to the bed 2 under regeneration, i.e. in phase a), while no hot water circulates in the other exchanger EHX in phase b).

(122) The condenser 12 yields the heat at ambient temperature to the heat sink through the collectors 9 and 10. The electric components for circulating the fluids 6, 7 and 8 and for actuating the switching valves SV1 and SV2 and the valve 4 have a maximum absorption of 70 W.

(123) The system can work uninterruptedly, and the hours of operation depend on the availability of the thermal resource. Assuming that a solar thermal system is used, solar radiation is available, on average, eight hours a day, which correspond to the production of approximately forty-five litres of potable water for a flow rate of 100 m3/h of treated air.

(124) With reference to FIG. 6, the enthalpic exchanger EHX is shown in the two operating phases.

(125) In particular, FIG. 6(A) shows the desorption phase b), and FIG. 6 (B) shows the adsorption phase a).

(126) In a normal cycle, during phase a) the air at ambient temperature A1, coming from the outside, is conveyed towards the enthalpic exchanger EHX and, while flowing therethrough in contact with the adsorbent material, loses part of its moisture and generates a flow of dry air A2 at the exit of the exchanger EHX.

(127) During phase b), an air flow A3 coming from the heat recovery block HX-REC is conveyed towards the enthalpic exchanger EHX, and at the same time the heat source HS supplies heat to the enthalpic exchanger EHX (hot air or water) and the flow A3, while passing through the exchanger EHX, is heated and acquires the moisture that was trapped in the adsorbent material during the previous phase, thereby generating the flow of hot and moist air A4, which is then sent to the condenser.

(128) FIG. 7 illustrates an embodiment of a first heat exchanger HX-REC1, wherein the hot air moves from top to bottom and the cold air moves from left to right, wherein the terms top, bottom, left and right refer to the representation shown in FIG. 7.

(129) FIG. 8 illustrates an embodiment of a second heat exchanger HX-REC2, wherein the hot and moist air moves from top to bottom and the cold and dry air moves from right to left, wherein the terms top, bottom, left and right refer to the representation shown in FIG. 8.

(130) In particular, FIG. 9 shows an embodiment of the enthalpic exchanger EHX. FIG. 9A shows a side view, in which a plurality of metal elements, in the form of ducts or pipes, form a radiator in which a heated fluid (air or water) flows and yields heat to the outside environment. On such ducts a plurality of lamellar panels (see FIG. 9B) are arranged, which increase the exposure area. FIG. 9C shows a sectional view along the line AA indicated in FIG. 9A.

(131) In the illustrated example there are three ducts like the one shown in FIG. 9A, mutually connected to two inlet and outlet valves.

(132) FIG. 9D shows two different application configurations of the adsorbent material. In the first embodiment, the adsorbent material is applied onto the lamellar panels, for example, as a coating (by spraying, immersion or deposition), whereas in the second embodiment the adsorbent material is in granular form and is arranged between two adjacent panels.

(133) Therefore, the air, as it flows through the machine, receives moisture from the adsorbent material (previously accumulated therein during phase a)) and receives heat from the exchange fluid circulating in the exchanger EHX.

(134) The air flowing therethrough is not in direct contact with the exchange fluid, but a metallic contact surface is present. In particular, said metallic contact surface comprises the pipes or ducts in which the exchange fluid flows, as well as fins or lamellar panels. Lamellar panels provide a considerable increase in contact and exchange area.

(135) The adsorbent material is distributed on the metallic surface of the pipes in which the exchange fluid flows and of the lamellar panels. As aforesaid, it may be in granular or panel form, or may be distributed on the metal elements to form a coating.

(136) In summary, the following is provided:

(137) i) an innovative reference thermodynamic cycle;

(138) ii) a compact water production system for a family, or anyway a group of people, in dry climates;

(139) iii) negligible power consumption (max. 70 W) compared with competing technologies;

(140) iv) compatibility with the broadest possible range of thermal resources.

(141) Furthermore, the proposed solution makes it possible to produce drinking and sanitary water within contexts of high aridity and inaccessibility of water resources: exploitation of the proposed cycle allows creating a compact system that can be sized to meet the water requirements of a family or a group of people; moreover, due to the inherent modular approach of the invention, it is possible to “assemble” the system to increase the production of liquid water as needed; the application can thus be broadened as a function of the user's requirements; notwithstanding the invention has been proposed herein for the production of sanitary and potable water, other fields of application actually exist as well, wherein the demand for water, conjugated with heat availability, makes it desirable to use this invention.

(142) The advantages of the above-described solution will now be listed. It exploits an isothermal transformation, as opposed to an isoenthalpic transformation; consequently, dimensions and space occupation, as well as the specific costs of the system per water mass unit produced, are lower when the thermodynamic cycle is based on an isothermal regeneration rather than an isoenthalpic one. Low regeneration temperature: an additional advantage of the isothermal transformation over the isoenthalpic one lies in the fact that, the thermal-hygrometric conditions at the exit of the dehumidifying bed being equal, i.e. assuming that the cycle producibility is the same, the heat supply temperature in the isoenthalpic transformation case is distinctly higher; for example, supposing that the temperature at the bed exit is 45° C. with a relative humidity of 100%, if the condensation temperature is 35° C. there will be a water production of approx. 3 lt/hr; in the isoenthalpic transformation case, the inlet temperature is approx. 113° C., so that the heat supply temperature must be slightly higher than this value; in the isothermal transformation case, the heat supply temperature must be slightly higher than 45° C.; this aspect has an important practical and economical implication: the isoenthalpic transformation requires a heat supply at a distinctly higher temperature, i.e. a more precious primary resource compared with the isothermal transformation case; for the isothermal regeneration a low-temperature solar system may suffice (which is economical, requires little maintenance, has no operating costs, and uses low-skill technology), whereas for the isoenthalpic regeneration it will be necessary to employ either a high-temperature solar system (a more advanced technology with higher maintenance costs and complexity) or a combustion system (biomass or hydrocarbons), which greatly limits the applicability thereof in underdeveloped countries. Closed regeneration cycle: the operating cycle is open during the adsorption phase, in order to accumulate water from the atmosphere; conversely, it is closed during the regeneration phase, i.e. it is always the same air that goes through the various phases, without being rejected into the outside environment before regeneration is complete; the latter is an important difference compared with other systems studied for and based on adsorbent materials; in particular, this measure further improves cycle producibility, reducing the waste resulting from the atmospheric exchanges occurring during the regeneration; in fact, the air exiting the condensation phase will have a relative humidity close to 100%, while ambient conditions are distinctly lower; for example, a dry climate has relative humidity values not exceeding 35%; if the regeneration air were directly rejected into the environment, also the water removed from the adsorbent material would be discharged; using as a reference the cycle already studied above, with regeneration at 45° C. and a condensation temperature of 35° C., approx. 3 lt/hr would be produced and approx. 2.5 lt/hr would be rejected into the environment; this rejected quantity, although heat was spent in order to extract it from the adsorbent material, cannot be recovered, which translates into wasted thermal energy; vice versa, in the closed cycle case this quantity is always recirculated in the system and requires no additional heat to be removed; specific consumption of heat per litre of condensed water in the above-mentioned hypotheses ranges from 2.7 kWh/lt in the closed cycle case to approx. 4.7 kWh/lt in the open cycle case. Accordingly, a more efficient system will be smaller and more economical. Low power consumption: the values of power consumption of the system presented herein are related to the auxiliary systems employed for moving the fluids involved, i.e. the fan for moving the regeneration air flow and the pump for recirculating the thermal fluid supplying the regeneration heat; moreover, in the case wherein water condensation occurs in dry conditions, i.e. by exploiting ambient air (e.g. at 35° C.), also the power consumption of the condenser's auxiliary units will have to be taken into account; with good approximation, and using a highly conservative approach, it can be estimated that the electric power values involved are the following: 20 W of electric power for the circulation pump; 30 W of electric power for moving the regeneration air (100 m3/h, with total load losses of 300 Pa); 350 W of electric power for moving the condensation air (dry cooler, 4,000 m3/h, with total load losses of 100 Pa), for a total of 400 W of electric power in the worst-case conditions; it is possible to make a comparison in terms of drawn electric power between the system presented herein and an equivalent vapour compression refrigeration machine, in equal operating and producibility conditions; in order to obtain a water flow rate of approx. 3 lt/hr from an environment at 35° C. and 35%, it is necessary to subtract approx. 6.3 kW of refrigeration power from the air; as relative humidity decreases (which is a typical condition of dry environments), this value increases; supposing that a conventional heat pump is used (COP=3), the compressor will have an electric absorption of approx. 2.1 kW; the thermal power at the condenser, to be discharged into the environment, will be 8.4 kW (versus 2.3 kW in the isothermal regeneration cycle); it is therefore reasonable to suppose that the power of the condenser fan will be considerably higher than the previously estimated 350 W; in conclusion, therefore, the system proposed herein has a maximum power consumption of 400 W, which is approx. 85% less than a conventional heat pump (COP=3) in equal operating conditions (2.7 kW); these 400 W can be easily derived from photovoltaic technology, whereas a compressor (which operates on alternating current) requires alternating current and therefore a passage through an inverter, resulting in higher installation costs and lower efficiency. High environmental sustainability: no aggressive/toxic fluids; if combined with a solar thermal system, no gaseous emissions; thermally activated refrigeration cycles (absorption machines) utilize chemically aggressive and toxic fluids, such as ammonia, lithium bromide; vapour compression refrigeration machines utilize refrigeration fluids that generally have a strong impact on the environment (Global Warming Potential); for example, one of the fluids that are most commonly used for air conditioning purposes, R410a, has a GWP value of 2090, i.e. 1 kg of R410a released into the atmosphere has an effect on the environment that is equivalent to 2,090 kg of CO2. Low skill technology: the types of adsorbent materials that are applicable to this cycle are numerous, ranging from high-performance precious materials, such as synthetic zeolites, to less expensive materials that still offer good performance in terms of ability to capture moisture from air, such as silica gel (3 €/kg); extremely poor materials are interesting as well, such as expanded clays with salt additives such as sodium chloride; the other components required for the operation of the cycle proposed herein are water/air exchangers, air/air exchangers, and low-temperature solar systems. High adaptability, ranging from low scale to high scale.

(143) The solution proposed herein operates by extracting water from air.

(144) If dirty or contaminated water is available, it can be sprayed into the air being conveyed towards the machine for extracting water. At the end of the process, purified water will be obtained starting from dirty water vaporized into the air flow supplied to the machine.

(145) Of course, without prejudice to the principle of the invention, the forms of embodiment and the implementation details may be extensively varied from those described and illustrated herein merely by way of non-limiting example, without however departing from the protection scope of the present invention as set out in the appended claims.