WO2001084066A1

WO2001084066A1 - Device for collecting water from air

Info

Publication number: WO2001084066A1
Application number: PCT/US2000/011716
Authority: WO
Inventors: Reinhard K. Radermacher; Hisham Fawzi
Original assignee: University Of Maryland
Priority date: 2000-05-01
Filing date: 2000-05-01
Publication date: 2001-11-08
Also published as: AU2000246850A1

Abstract

The present invention is directed to a water making device that collects the moisture contained in the atmosphere and condenses it into high purity water. In one embodiment, moist air (180) entering the system flows first through a precooler (air-to-air heat exchanger) (100) and then passes across an evaporator (110) that cools the air below the dew point and producers water. The dry, cold air that leaves the evaporator flows through the second path of the precooler, such that the dry, cold air is used to precool the incoming moist air. In a second embodiment, an integrated water maker/water cooler system is disclosed in which two evaporators are employed. The first evaporator (410) serves the same function as that of the conventional water maker, to remove the moisture. The second evaporator (415) is submerged inside a water storage tank (510) or mounted in a heat transfer relationship with the storage tank, for cooling the water collected in the tank.

Description

Device for Collecting Water from Air

Background of the Invention

Field of the Invention

The present invention is directed to a device for collecting water from air and more particularly, to a device for collecting the moisture contained in the atmosphere and condensing it into water of high purity.

Related Art

Several devices have been previously described for making water from moisture in the atmosphere. For the sake of simplicity, these devices are termed herein "water-makers." Typically, these systems are based on a refrigeration device operating according to the vapor compression refrigeration cycle. They are known from other applications as dehumidifiers. In the vapor compression refrigeration cycle, a refrigerant is circulated through a closed circuit cycle of condensation and evaporation to produce a cooling effect. Cooling is accomplished by the evaporation of the liquid refrigerant at low pressure. The refrigerant first enters a compressor, where the temperature of the refrigerant is elevated by mechanical compression, turning the refrigerant into a superheated, high pressure vapor. The high pressure vapor enters a condenser, where the vapor condenses to a liquid and the resultant heat is dissipated to the surroundings. The resultant high pressure liquid then passes through an expansion valve through which the fluid pressure and temperature are lowered. Finally, the low-pressure fluid enters the evaporator, where it evaporates by absorbing heat from the cooled space. The resultant vapor then reenters the compressor and the cycle is repeated. As air flows across the evaporator, it is cooled below its dew point. Thus, water, in the form of condensation, is obtained as a byproduct of the vapor compression refrigeration cycle. A condensed water collection device is disposed below the evaporator to collect water than condenses as air flows over the evaporator. Often, these water-makers are also equipped with various devices for water storage and for maintaining and controlling water purity, such as UV lights and filters. Conventional water supply devices, such as water fountains and dispensers for spring water, are designed to provide water that is either cooled or heated for the convenience of the user.

The prior water-makers all have in common that the preferred operating mode requires air of high moisture content which is readily available in high temperature/high humidity climates. For most devices, the operating range begins at 65 °F and 50% relative humidity and ranges to higher temperatures. If the temperature drops below 65 °F, the evaporator coil will show frost accumulation and eventually be covered by a solid block of ice. Under low temperature conditions, the water production rate is very low or zero and the power consumption is very high. The effectiveness of the system, expressed in liters of water per kWh of electricity consumed is very low or zero and accordingly the operating cost unacceptably high.

The inefficiency of the conventional systems results from the fact that for each pound of water produced, a large amount of air has to be cooled below the dew point. The colder the air temperature, the lower the water content and the lower the dew point. Consequently, more air has to be cooled before any moisture is condensed. This leads to very large evaporator capacities that do not contribute to the production of water per se.

However, once a user has a water-maker in operation, he will expect water production even under colder and dryer conditions. Thus, there is a need for a more reliable device, the water production capability of which is not so sensitive to weather and environmental conditions. This is especially important for applications in deserts, military uses and the like, where no other back-up water source may be available. Summary of the Invention

The present invention solves the need in the art by providing a more reliable water making device, wherein the water production capability is not so sensitive to weather and environmental conditions. In particular, the present invention is directed to a device for collecting water from air particularly well suited for dry, low air temperature environments.

In one embodiment of the present invention, moist air entering the system flows first through a precooler and then passes across an evaporator that cools the air below the dew point and produces water. The dry, cold air that leaves the evaporator flows back through the precooler, such that the dry, cold air is used to precool the incoming moist air. The precooler can be an air-to-air heat exchanger and may consist of a design that includes a heat pipe, a thermo-syphon, a heat exchange wheel or similar devices known to those skilled in the art. A refrigerant is circulated between the evaporator and a condenser through a closed circuit cycle of condensation and evaporation to produce the cooling effect. The refrigeration device can operate according to either the vapor compression refrigeration cycle, through the use of a mechanical compressor, or the absorption refrigeration cycle, incorporating a heat source, absorption generator and a secondary fluid or absorbent. In one embodiment of the invention, two fans are used, one to move air across the evaporator and the other to move air across the condenser. Alternatively, a single fan arrangement can be used, in which a single fan simultaneously moves air across both the evaporator and the condenser.

In a second embodiment of the present invention, an integrated water maker/water cooler system is disclosed in which two evaporators are employed. The first evaporator serves the same function as described above, to remove the moisture from the air, while the second evaporator is submerged inside a water storage tank or mounted in a heat transfer relationship with the water tank, for cooling the water collected in the tank. The refrigerant flow for both evaporators is controlled by a thermostatic expansion valve that maintains constant refrigerant superheat at the outlet of the second evaporator. A control system for controlling the compressor, evaporator fan and expansion valve may be employed, such that the control system turns on the compressor and the evaporator fan in response to a signal indicating that water making is required and the control system turns on the compressor and turns off the evaporator fan in response to a signal indicating that water making is not required but water cooling is required. Additionally, the control system can adjust the expansion valve based on the superheat downstream of the second evaporator.

In a third embodiment, relatively dry, cold air flowing through a first air duct is passed across a desiccant wheel, which absorbs moisture in the air stream.

The wheel is then rotated into a regeneration zone of a second air duct where it is exposed to hot air of very small flow rate for regeneration. The heat supplied by the air to the wheel is just sufficient enough to heat the wheel to a temperature level of about 90 °C, so that all absorbed water is released into the air stream. In this manner, the moisture content of the hot regeneration air stream is much higher than that of the original air stream and the dew point of the regeneration air stream is also increased considerably. The regeneration air stream is then passed across an air-to-air heat exchanger, such that the regeneration air stream is cooled below its dew point and a significant portion of its moisture content is condensed. The desiccant material may be continuously rotatable, such that there is always some desiccant material in the first air duct and there is always some desiccant material in the second air duct. In order to extract as much moisture as possible from the regeneration air stream, a vapor compression system may be added and operated in the same manner as described above. In certain applications, when the system has to be operated independent of any supply of electricity, the vapor compression system can be operated using an internal combustion engine or any other such power plant (micro turbine, gas turbine, fuel cell, etc.) as the source of power for the compressor, fan(s) and controls. In this case, the waste heat of the engine can be utilized to heat the regeneration air. Brief Description of the Figures

The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

FIG. 1 is a schematic diagram of one embodiment of a water maker according to the present invention.

FIG. 2 is a psychometric diagram comparing a conventional water maker to the embodiment of the present invention shown in FIG. 1.

FIG. 3 is a schematic diagram of another embodiment of a water maker according to the present invention.

FIG. 4 is a schematic diagram of yet another embodiment of a water maker according to the present invention.

FIG. 5 is a schematic diagram of one embodiment of a complete water making/water cooling unit according to the present invention.

FIG.6 is a schematic diagram of another embodiment of a complete water making/water cooling unit according to the present invention.

FIG. 7 is a schematic diagram of still yet another embodiment of a water maker according to the present invention.

FIG. 8 is a psychometric diagram of the embodiment of the present invention shown in FIG. 7. Detailed Description of the Preferred Embodiments

The present invention is directed to a device for collecting water from air and more particularly, to a device for collecting the moisture contained in the atmosphere and condensing it into water of high purity. Preferred embodiments of the present invention are now described. While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the invention. It will be apparent to a person skilled in the relevant art that this invention can also be employed in a variety of other devices and applications.

Fig.1 shows one embodiment of the present invention. Moist air entering the system flows first through a precooler 100 before it passes across an evaporator 110 that actually cools the air below the dew point and produces water. (Air flow is represented by arrows 180 in Fig. 1.) The dry, cold air that leaves evaporator 110 flows through a second path of precooler 100. In this way, the cold, dry air is used to precool the incoming moist air. Since both air streams have approximately the same specific heat capacity and the same mass flow rate, precooler 100 cools the incoming air stream almost to the dew point when the effectiveness of precooler 100 is chosen in the appropriate range, preferably approximately 0.9 depending on operating and design conditions. Thus the capacity of evaporator 110 can be devoted almost entirely to the production of water, rather than for the cooling of air.

Precooler 100 can be an air-to-air heat exchanger that approaches counter flow as much as possible (although cross flow alone would be helpful, but not as good as counter flow) and may consist of a wide variety of materials, such as copper, aluminum and/or plastic, or a design that includes a heat pipe, a thermo- syphon, a heat exchange wheel or similar devices known in the art for use in air- to-air heat exchange. Another embodiment is the use of a heat exchange wheel. The heat exchange wheel is similar to a desiccant wheel, but the heat exchange wheel only transfers heat, not moisture, from one air stream to the other. The preferred embodiment uses both a heat pipe and a heat exchange wheel.

Evaporator 110, condenser 120 and compressor 130 operate according to the vapor compression refrigeration cycle to form a closed loop refrigeration circuit. As discussed above, in the vapor compression refrigeration cycle, a refrigerant is circulated through a closed circuit cycle of condensation and evaporation to produce a cooling effect. The refrigerant (not shown), for example Freon gas, first enters compressor 130. (Refrigerant flow is shown by arrows 190 in Fig. 1.) The refrigerant temperature is elevated by the mechanical compression performed by compressor 130, such that the refrigerant leaves compressor 130 and enters condenser 120 as a superheated, high pressure vapor. The vapor condenses to a liquid at this pressure within condenser 120 and the resultant heat is dissipated to the cooled surroundings. The refrigerant then leaves condenser 120 as a warm, high-pressure liquid. The pressure and temperature of the liquid refrigerant are decreased as the refrigerant flows through an expansion valve 160 and the resultant cool, low pressure liquid is vaporized in evaporator 110 by absorbing heat from the moist inlet air stream. Cooling is accomplished by the evaporation of the liquid refrigerant at low pressure. The refrigerant, as a cool, low pressure vapor, then enters compressor 130 and the cycle is repeated. A water collection device 170 is disposed below, or otherwise in association with, evaporator 110 to collect the condensed water outlet.

Condenser 120 of the system is cooled with a second air stream dedicated to just this purpose (indicated by arrows 185 in Fig. 1), this is unlike a conventional system, where condenser 120 is cooled with the cold air leaving evaporator 110. As shown in the psychometric diagram of Fig. 2, in the conventional system, the air stream leaving evaporator 110 has to absorb from condenser 120 an amount of heat (symbolized by the length of line 3 to 6) that is composed of two contributions. The first is the heat removed by evaporator 110 (which is the latent and sensible load, line 3 to 5) plus the work input to compressor 130, line 5 to 6. With this requirement, condenser 120 will heat the air stream significantly beyond its original temperature, which would be reached at point 4. Thus the temperature of evaporator 110 must be below T₃ and the temperature of condenser 120 above T₆. This is a rather large temperature lift, increasing quickly for decreasing air temperatures and moisture content. In the system according to the present invention, on the other hand, the temperature lift can be reduced by using air from the surroundings for cooling of condenser 120. This air flow rate can be chosen as large as necessary to lower the temperature of condenser 120 to a much more efficient operating condition. Preferably two fans 150 are used. Alternatively, a single fan 350 can be used, as shown in Fig.3 and discussed below.

As shown in Fig. 2, under low moisture conditions, the air has to be cooled to very low temperatures such as T_3a. However, because of precooler 100, the capacity of evaporator 110 has to take care of only the enthalpy difference from h_2a to h_3a (line 2a to 3a). Accordingly, heat from condenser 120 is smaller than in the conventional system (line 4a to 6a instead of line 3 to 6) and is rejected under more beneficial conditions as described above. Thus the process according to the present invention increases the energy efficiency of the water- making process. Fig. 3 shows another embodiment of the present invention that requires only one fan 350 to process both inlet air streams simultaneously. Moist air entering the system flows across both precooler 300 and condenser 320. A portion of the moist inlet air flows first through precooler 300 and then passes across evaporator 310, at which point the air is cooled below the dew point and water is produced. (This portion of the air flow is represented by arrows 380 in

Fig.3.) The dry, cold air that leaves evaporator 310 flows through a second path of precooler 300. In this way, the cold, dry air is used to precool the incoming moist air. The remainder of the moist inlet air is used to cool condenser 320. (This portion of the air flow is represented by arrows 385 in Fig.3.) The air flow rate can be chosen as large as necessary, depending on the desired operating condition of condenser 320. Preferably, the air flow rate across the condenser should be four to ten times the air flow rate across the evaporator. Fan 350 is utilized to control the air flow rate.

As discussed above, evaporator 310, condenser 320 and compressor 330 operate according to the vapor compression refrigeration cycle to form a closed loop refrigeration circuit. As discussed above, in the vapor compression refrigeration cycle, a refrigerant is circulated through a closed circuit cycle of condensation and evaporation to produce a cooling effect. The refrigerant, for example Freon gas, first enters compressor 330. (Refrigerant flow is shown by arrows 390 in Fig.3.) The refrigerant temperature is elevated by the mechanical compression performed by compressor 330, such that the refrigerant leaves compressor 330 and enters condenser 320 as a superheated, high pressure vapor. The vapor condenses to a liquid at this pressure within condenser 320 and the resultant heat is dissipated to the cooled surroundings. The refrigerant then leaves condenser 320 as a warm, high-pressure liquid. The pressure and temperature of the liquid refrigerant are decreased as the refrigerant flows through an expansion valve 360 and the resultant cool, low pressure liquid is vaporized in evaporator 310 by absorbing heat from the moist inlet air stream. Cooling is accomplished by the evaporation of the liquid refrigerant at low pressure. The refrigerant, as a cool, low pressure vapor, then enters compressor 330 and the cycle is repeated. A water collection device 370 is disposed below, or otherwise in association with, evaporator 310 to collect the condensed water outlet.

As mentioned in the background section above, whenever the surface temperature of evaporator 110 drops below freezing, frost will form on the coil. According to the present invention, this frost is removed periodically through one of three mechanisms (that also could be employed in combination). One of ordinary skill in the art will understand how to apply these mechanisms from the following brief description. The first is a defrost cycle, under which hot gas from the discharge of compressor 130 is recirculated through evaporator 110 until the frost is removed. The second is an electric heater that is integrated in evaporator coil 110 or attached to it or mounted in close proximity, which is periodically operated to melt any frost. The third is an electric heater external to evaporator 110 that radiates heat unto the frost until it is removed. For the latter two options, compressor 130 should be stopped for the defrost mechanism to be the most effective. For the first two methods, the design has to account for the possibility that ice may break off in pieces. Provisions have to be incorporated in the design to prevent these pieces from clogging the drains or drain pans. For example, the drain pan and the drain pipe may have to be heated to avoid any unwanted accumulation of ice. Preferably, when the system is driven through an internal combustion engine, the waste heat available from the engine can also be used as the heat source to defrost the evaporator.

While the above embodiments are based on the usage of a vapor compression system as the source of cooling capacity, whenever waste heat is available, or when only fuel, but no electricity is available, an absorption refrigeration system can be employed instead. Like the vapor compression refrigeration cycle, an absorption refrigeration system produces a cooling effect by circulating a refrigerant through a closed circuit cycle of condensation and evaporation. However, where a mechanical compressor is used in the vapor compression cycle to provide the pressure differentials required to circulate the refrigerant between the evaporator and the condenser, the absorption refrigeration system utilizes an absorption refrigeration generator, a direct heat source, such as a dedicated burner, or an indirect heat source, such as steam, hot water, or waste heat from other processes, and a secondary fluid or absorbent, such as aqueous lithium bromide solution, to circulate the refrigerant. The generator-absorber combination is equivalent to the compressor in the vapor compression refrigeration cycle. Heat applied in the generator causes the mixture of the refrigerant (typically water) and the absorbent to boil, evaporating water while leaving behind the absorbent, thus producing the refrigerant vapor. The refrigerant vapor passes to the condenser where it is condensed into a liquid refrigerant. The liquid refrigerant flows through an expansion valve into the evaporator which operates under a vacuum to absorb heat from the refrigerated space. The resultant refrigerant vapor is then converted back into a liquid before being return to the generator to repeat the cycle. In particular, the lithium bromide solution, which was concentrated within the generator when the refrigerant vapor was boiled off, passes from the generator through a heat recovery heat exchanger to the absorber. The concentrated lithium bromide solution absorbs the refrigerant vapor from the evaporator and is pumped through the heat exchanger, to recover heat from the concentrated solution, before returning to the generator to repeat the process. As an additional mechanism for removing frost from evaporator 110, hot gas leaving the generator of the absorption system can flow directly into evaporator 110. Alternatively, hot solution from the generator or from the absorber can be circulated through evaporator 110 or through a second path that is integrated for this purpose within evaporator 110. As shown in Fig.4, in an alternative embodiment of the present invention, two evaporators may be used to provide for a combined water maker and water chiller. The first evaporator 410 serves the same function described above. Air is moved across evaporator 410 by fan or any similar device or just by mere natural convection for the purpose of removing the moisture and producing water. The second evaporator 415 is submerged inside a water storage tank 510, as shown in Fig. 5, or mounted in a heat transfer relationship with a water tank (not shown), such that tank 510 is cooled by second evaporator 415. Tank 510 may be the main water storage device, as shown in Fig.5, or may serve as a secondary storage device for the mere purpose of producing cold water only, as shown in Fig. 6. When tank 510 is used as a secondary storage device for cold water only, a primary tank 600 serves as the main water storage device and a second secondary tank 610 may be used for the purpose of storing and producing hot water.

Evaporators 410 and 415 are disposed in series, such that second evaporator 415 is located after first evaporator 410 from a refrigerant flow point of view. Alternatively, the reverse order can be used as well. The refrigerant flow for evaporators 410 and 415 is controlled by a thermostatic expansion valve 460 that maintains constant refrigerant superheat at the outlet of second evaporator 415. The water maker/water cooler system according to the present invention is self regulating and works as follows:

Case 1: Water maker operation is required, but no water cooling is required. The water level control device (not shown) detects that water needs to be made and turns on compressor 430 and fan 450 for air movement across first evaporator 410. Since second evaporator 415 is assumed to have no cooling load and because expansion valve 460 maintains a certain superheat, superheated refrigerant leaves first evaporator 410 and second evaporator 415 serves just as a section of pipe with no heat transfer duty.

Case 2: Water cooling is required, but no water making operation is required. The thermostat (not shown) of water storage tank 510 calls for cooling and turns on compressor 430 only. Again expansion valve 460 causes a constant superheat at the outlet of second evaporator 415, but all the evaporation of refrigerant occurs within second evaporator 415. First evaporator 410 serves just as a section of tube without any or only very minimal heat transfer. Since in this case, fan 450 for first evaporator 410 is turned off, no air is cooled or moisture condensed.

Case 3: Both water making and water cooling operations are required at the same time. The water level control device detects that water needs to be made and the thermostat of water storage tank 510 (Fig. 5) calls for cooling, such that compressor 430 and fan 450 are turned on. Once again expansion valve 460 controls the superheat at the outlet of second evaporator 415. Now evaporators 410 and 415 both transfer heat, and water is made and cooled simultaneously.

The thermostatic expansion valve 460 meters the refrigerant flow such that there is always sufficient liquid refrigerant to fulfill the load requirements, while protecting compressor 430 from liquid flooding. A charge control device (not shown) is preferably employed at the outlet of condenser 420, as a receiver, or at the outlet of second evaporator 415, as a suction accumulator. For better control or to obtain higher capacities, two entirely separate refrigeration systems may be employed, one for water making and one for water chilling. This is, however, the more costly option. In yet another embodiment of the present invention, two evaporators are employed in parallel instead of in series, with appropriately adjusted controls. When the evaporators are arranged in parallel, each one has to be fitted with its own thermostatic expansion valve and a flow control valve. The first maintains the desired superheat at the outlet of the respective evaporator and the second admits refrigerant flow to the respective evaporator depending on whether or not the respective thermostat calls for cooling or not.

Fig. 5 shows a conceptual arrangement of the complete unit. Condensation dripping off the water maker evaporator coil 410 is collected in water storage tank 510. Here it is kept cold by second evaporator 460. When cold water is needed, it is drained from a cold water valve 520. When hot water is needed it is drained from a hot water valve 530. When hot water valve 530 is operated, it simultaneously operates a switch that turns on a hot water heater 540 that is installed within, at or in close proximity to hot water valve 530, such that cold water in tank 510 is heated instantaneously to the desired temperature.

An alternative version, shown in Fig.6, allows for one main water storage tank 600 and up to two secondary tanks 510 and 610. The first secondary tank 510 is used for the preparation and storage of cold water. Second evaporator 415 is integrated within tank 510, as discussed above. Second secondary tank 610 is used for hot water, and has an integrated electric heater 640 that maintains a constant hot water temperature. Alternatively, a two tank configuration could be employed where a single secondary tank could either be used for hot water or cold water storage in conjunction with primary water storage tank 600. Depending on available space, control strategy and other design criteria, the above described single tank configuration, two tank configuration, or three tank configuration can be employed.

Another implementation of this device includes in addition, or instead of, the water cooling section, the addition of an ice maker. In this way, the consumer can utilize the clean, fresh water as a source for fresh, clean ice. In contrast to the typical ice maker in a refrigerator, this ice is free of smell and taste and has the same purity as the water. The ice maker can be identical or similar to those used in refrigerator/freezers (although is should have its own evaporator for freezing purposes and should have an expansion device that controls the temperature levels so that ice making is possible); or may be a flake ice maker or other such device as known in the art. Alternatively, when two evaporators are used in series (or parallel) the ice maker function can be integrated using one of these evaporators. When ice is to be made, only the evaporator producing the ice can be in operation (no water can be made) and the thermostatic expansion valve has to be adjusted such that the evaporator temperature is lowered sufficiently (25 °F or lower) to produce ice.

Another feature that can be added to water maker of the present invention are so called proximity valves that cause the water to be dispensed when an object, such as a hand with a water glass, a bottle, or other such container approaches the spout. This can be applied for cold and hot water dispensing and even for the dispensing of ice. The proximity valve may operate based on any of the concepts well known in the art. The preferred option is one in which the water flow is initiated by means of a small dispenser pump dedicated for this purpose. As an alternative, the water pump that is used to manage the water level in the tanks can also perform the duty of dispensing water when appropriate valves are included to direct the water flow as needed.

Another dispenser feature that can be incorporated into the water maker according to the present invention is the "push tube," in which the water dispensing tube itself is pushed in, pulled out and/or bent to cause the water (or ice) to be dispensed. Additionally, for all embodiments discussed above, as an alternative configuration, water filtration and purification devices can be integrated at various points of the water conduits. These can be activated carbon filters or other filters suitable for water purification and UN lights or other such devices to disinfect the water.

Finally, the water-maker according to the present invention may be equipped with a device that prevents the primary storage tank from overflowing while the water maker produces water and no water is consumed. Conventional designs employ a low cost option in which a float is used. When the water level reaches the intended upper limit of the tank capacity the float begins to float on top of the water and a switch, released from the weight of the float turns off the system. This device has the disadvantage that each time the tank is removed to be exchanged for an empty one or for cleaning, the float may not be correctly positioned to act as needed. The following alternative approaches avoid this problem. In one embodiment, a weight sensor may be employed, that measures the weight of the water tank and turns the system off when the prescribed weight is reached. In another embodiment, a differential pressure transducer is used, that measures the static pressure exerted by height of the water column and turns of the system when the prescribed height is reached. In yet another embodiment, an optical device, such as an infra red or light sensing device, may be employed, that measures the height of the water level and, when the light beam is interrupted or reflected by the rising water level, depending of the design, the system is turned off.

While the water maker system according to the present invention produces water that is in purity very similar to distilled water, it is expected that some consumers would like to add minerals to the water to cause it to resemble true spring water or water from a certain ground based source. In other uses, the consumer may want to add syrup, fruit juice concentrate or the like to produce beverages that are based on pure, distilled water. The preferred option to achieve this is to employ a small metering pump that is actuated whenever the dispenser pump is actuated. In this way, the syrup or added fluid or minerals are mixed into the water when it is used and the resulting beverage is always fresh. The metering pump receives its fluid from a storage container that needs to be replaced or refilled periodically. The fact that a metering pump is employed assures that exactly the desired dose of fluid is added. The flow rate produced by the metering pump can be made adjustable so that one device can be used to add minerals at the lowest possible flow rate and syrups or other flavors at higher flow rates as needed.

In another embodiment of the present invention, a desiccant system may be used to remove moisture from the air, in place of the above described vapor compression and absorption refrigeration systems. Desiccants are materials which attract and hold water vapor. Fig. 7 shows an embodiment of such a system. In this embodiment, relatively dry cold air, too low in temperature to be efficiently processed in a conventional vapor compression or absorption refrigeration design is passed through a first air duct 700 across a desiccant wheel

710, moving from point 1 to 2 (the numbers in Fig.7 and Fig.8 refer to the same state points). Desiccant wheel 710 may be any of the various configurations known to those skilled in the art, such as a laminar flow channel desiccant wheel consisting of a matrix of parallel channels, coated or impregnated with the desiccant material, through which air flows. In the process, as the dry cold air flows through first air duct 700, desiccant wheel 710 absorbs the moisture contained in the air and the heat of absorption heats the air stream as well as wheel 710. This process is also shown on the psychometric diagram of Fig. 8.

Desiccant wheel 710 is then rotated into a second air duct 720 where it is exposed to hot air of very small flow rate for regeneration. This hot air stream can originate from either one or both of the following two sources. It can be air from the same source as that of point 1 (as indicated by point 1 A in Fig. 7) or it can be air of point 2. As compared to the first option, the latter has the advantage that it is hotter than that of 1 , and the disadvantage is that it is dryer. The system designer will select the best option, but the concept works either way. In either case, the air stream in second air duct 720 is heated by heater 730. The flow rate within second air duct 720 is chosen as small as possible, such that the heat supplied by the air to desiccant wheel 710 is just sufficient to heat desiccant wheel 710 to a temperature level of at least 80 °C, so that all moisture absorbed by desiccant wheel 710 in first air duct 700 is evaporated into the air stream in second air duct 720. In this way, the moisture content of the warm air stream leaving desiccant wheel 710 at point 4 is much higher than that of the original air stream at point 1 and the dew point of this air stream is also increased considerably. The air stream in second air duct 720 is then passed across an air- to-air heat exchanger 740. The air stream on the other side of heat exchanger 740 is air from the surroundings of the same low temperature as at point 1. Thus, the hot, moist air stream in second air duct 720 is cooled below its dew point (point 5, not shown in Fig. 7), and a significant portion of its moisture content is condensed. Heat exchanger 740 may be cooled through a vapor compression or absorption refrigeration system or by any other cold source. The temperature of the air stream leaving heat exchanger 740 approaches ideally the temperature of the air at point 1. In order to extract as much moisture as possible from the regeneration air stream, this system can also be operated in conjunction with a vapor compression refrigeration system, as described above, to further remove moisture.

Thus the proposed system uses the absorption properties of desiccant material 710 to extract moisture from a large quantity of rather cold and dry air to create a small stream of warmer, but much moister air. From this warm, moist air stream the moisture can be extracted without any additional source of cooling capacity beyond the original cold air stream. The only energy required to operate this system is the heat required to produce the hot air stream in second air duct 720 for the regeneration of desiccant wheel 710. Heater 730 may be a dedicated burner (not shown) or waste heat from any source that produces heat of a sufficiently high temperature such as truck engines or diesel generators. While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Additionally, all references cited herein, including journal articles or abstracts, published or corresponding U.S. or foreign patent applications, issued U.S. or foreign patents, or any other references, are each entirely incorporated by reference herein, including all data, tables, figures, and text presented in the cited references.

The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art (including the contents of the references cited herein), readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning andrange of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance presented herein, in combination with the knowledge of one of ordinary skill in the art.

Claims

What Is Claimed Is:

1. A device for collecting water from air, comprising: a condenser; an evaporator; an expansion valve; a compressor; a closed loop refrigerant circuit connecting said condenser and said evaporator through which refrigerant flows from said condenser through said expansion valve to said evaporator and from said evaporator through said compressor into said condenser; a first duct having an inlet end and an outlet end, said outlet end connected to said evaporator for carrying moist inlet air to said evaporator; a second duct having an inlet end and an outlet end, said inlet end connected to said evaporator for carrying dry outlet air from said evaporator; a precooler device placed between said first duct and said second duct for cooling said moist inlet air with said dry outlet air; and a condensed water collection device below said evaporator.

2. The device according to claim 1, further comprising: a first fan disposed in said second duct for moving air across said evaporator; and a second fan disposed near said condenser for moving air across said condenser.

3. The device according to claim 1, further comprising: a third duct having an inlet end and an outlet end, said condenser disposed inside said third duct, said third duct inlet end positioned adjacent said first duct inlet end, said third duct outlet end positioned adjacent said second duct outlet end, and a fan near said outlet ends of said third and second ducts for simultaneously moving air through said first, second and third ducts.

4. The device according to claim 1, wherein said compressor is powered by an internal combustion engine.

5. The device according to claim 1, wherein said compressor is powered by a micro turbine.

6. The device according to claim 1, wherein said compressor is powered by a fuel cell.

7. The device according to claim 1 , wherein said precooler device is an air-to-air heat exchanger.

8. The device according to claim 7, wherein said air-to-air heat exchanger includes a heat pipe.

9. The device according to claim 7, wherein said air-to-air heat exchanger includes a thermo-syphon.

10. The device according to claim 7, wherein said air-to-air heat exchanger includes a heat exchange wheel.

11. A device for collecting water from air, comprising: a condenser; an evaporator; an expansion valve; an absorption refrigeration generator; a closed loop refrigerant circuit connecting said condenser and said evaporator through which refrigerant flows from said condenser through said expansion valve to said evaporator and from said evaporator through said absorption refrigeration generator into said condenser; a first duct having an inlet end and an outlet end, said outlet end connected to said evaporator for carrying moist inlet air to said evaporator; a second duct having an inlet end and an outlet end, said inlet end connected to said evaporator for carrying dry outlet air from said evaporator; a precooler device placed between said first duct and said second duct for cooling said moist inlet air with said dry outlet air; and a condensed water collection device below said evaporator.

12. The device according to claim 11, further comprising: a first fan disposed in said second duct for moving air across said evaporator; and a second fan disposed near said condenser for moving air across said condenser.

13. The device according to claim 11, further comprising: a third duct having an inlet end and an outlet end, said condenser disposed inside said third duct, said third duct inlet end positioned adjacent said first duct inlet end, said third duct outlet end positioned adjacent said second duct outlet end, and a fan near said outlet ends of said third and second ducts for simultaneously moving air through said first, second and third ducts.

14. The device according to claim 11, wherein said absorption refrigeration generator is powered by waste heat from an internal combustion engine.

15. The device according to claim 11, wherein said absorption refrigeration generator is powered by waste heat from a micro turbine.

16. The device according to claim 11, wherein said absorption refrigeration generator is powered by waste heat from a fuel cell.

17. The device according to claim 11, wherein said precooler device is an air-to-air heat exchanger.

18. The device according to claim 17, wherein said air-to-air heat exchanger includes a heat pipe.

19. The device according to claim 17, wherein said air-to-air heat exchanger includes a thermo-syphon.

20. The device according to claim 17, wherein said air-to-air heat exchanger includes a heat exchange wheel.

21. A device for collecting water from air: a condenser; a compressor; a first evaporator for condensing water from air having a fan associated therewith; a second evaporator for chilling water or maldng ice; a closed loop refrigerant circuit connecting said condenser, said first evaporator and said second evaporator, through which refrigerant flows from said condenser to said first evaporator and said second evaporator and from said second evaporator through said compressor back into said condenser; and a condensed water collection device below said first evaporator.

22. The device according to claim 21, further comprising: a control system for controlling said compressor and said fan, said control system turning on said compressor and said fan in response to a signal indicating that water making is required, and said control system turning on said compressor and turning off said fan in response to a signal indicating that water making is not required but water cooling is required.

23. The device according to claim 21, further comprising: a flow control device disposed within said refrigerant circuit for controlling the superheat at the outlet of said second evaporator.

24. The device according to claim 23, wherein said flow control device is an expansion valve.

25. The device according to claim 23, further comprising: a control system for controlling said flow control device, said control system adjusting said flow control device based on the superheat downstream of said second evaporator.

26. The device according to claim 21, wherein said first and second evaporators are arranged in series, with one of said first and second evaporators disposed upstream of the other of said first and second evaporators.

27. The device according to claim 21 , wherein said condensed water collection device is a water storage tank.

28. The device according to claim 27, wherein said second evaporator is submerged inside said water storage tank.

29. The device according to claim 21, further comprising a first duct having an inlet end and an outlet end, said outlet end connected to said first evaporator for carrying moist inlet air to said first evaporator; a second duct having an inlet end and an outlet end, said inlet end connected to said first evaporator for carrying dry outlet air from said first evaporator; and an air to air heat exchanger device placed between said first duct and said second duct for transmitting heat from said moist inlet air to said dry outlet air.

30. A device for collecting water from air comprising: a first air duct; a second air duct; a heater disposed in said second air duct; a desiccant material, said desiccant material positioned in said first air duct for absorbing water from air moving through said first air duct, said desiccant material movable to said second air duct for releasing absorbed water into warm air moving through said second air duct; a heat exchanger disposed in said second air duct such that it cools below the dew point warm moist air moving through said second air duct downstream of said desiccant material; and a condensed water collection device in said second air duct for collecting water that condenses out of air at said heat exchanger.

31. The device according to claim 30, wherein said desiccant material is continuously rotatable such that there is always some desiccant material in said first air duct and there is always some desiccant material in said second air duct.

32. The device according to claim 30, wherein air from said first air duct downstream of said desiccant material is routed to said second air duct.

33. The device according to claim 30, wherein said heat exchanger is cooled through a vapor compression system.

34. The device according to claim 30, wherein said heat exchanger is cooled through a absorption refrigeration system.

35. A process for collecting water from air, comprising the steps of:

(a) directing moist air through a precooler;

(b) passing said air across an evaporator, to cool said air below its dew point and produce water and dry cold air; and

(c) directing said dry cold air back through said precooler, such that said dry cool air is used to precool said moist air.

36. A process for collecting water from air, comprising the steps of:

(a) directing moist air through a precooler;

(b) passing said air across an evaporator, to cool said air below its dew point and produce water and dry cold air; (c) contacting a second evaporator with a water storage tank, such that said water storage tank is cooled by said second evaporator; and

(d) directing said dry cold air back through said precooler, such that said dry cool air is used to precool said moist air.

37. A process for collecting water from air, comprising the steps of: (a) directing dry cold air across a desiccant wheel, which absorbs moisture from said air;

(b) rotating said wheel into a regeneration zone where it is exposed to hot air of very small flow rate for regeneration, such that said moisture absorbed by said wheel is evaporated into the air stream; and (c) passing said warm moist air stream across an air to air heat exchanger such that said moist air stream is cooled below its dew point and water is produced.