Abstract:
A system that provides both air conditioning and atmospheric water-harvesting has a refrigerant compressor and a refrigerant condenser that serve separate evaporators for the air conditioning subsystem and the atmospheric water-harvesting subsystem. The system can be controlled to operate in one mode that maximizes water production output or another mode that maximizes efficiency in terms of water output per unit of electricity consumed. The ability to switch between maximized water production and maximized water-production efficiency can be implemented in a stand-alone, dedicated water-harvesting system as well.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on and claims the priority benefit of U.S. provisional application No. 62/100,335 filed Jan. 6, 2015, the contents of which are incorporated herein in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    In general, the disclosure relates to air conditioning and atmospheric water-harvesting systems. 
       BACKGROUND OF THE INVENTION 
       [0003]    Air conditioning is a well-known technology. In general, air is passed across the cooling coil (e.g., an evaporator) of a refrigeration circuit, where it is cooled and dried to a certain extent. After flash-evaporating in the evaporator and absorbing heat from the air flowing across the cooling cool as it does so, refrigerant in the refrigeration circuit is compressed to high pressure (and high temperature) in a compressor and then condensed back to its liquid phase in a condenser. A cooling medium (e.g. air or, in some systems, water or other liquid medium) flows past the condenser to cool the refrigerant. Heat that the refrigerant has absorbed from the air flowing across the cooling cool (as well as heat that has been imparted to the refrigerant due to compression) is transferred to the cooling medium and “disposed” of, e.g., by venting the cooling air to an outside environment, thereby allowing the refrigerant to continue cycling. 
         [0004]    Atmospheric water-harvesting—that is, extracting moisture from the ambient atmosphere in sufficient quantities to provide for human/animal consumption—is a somewhat less common technology. Although atmospheric water-harvesting uses a cooling cycle that is, conceptually speaking, generally the same as or similar to the cooling cycle used for air conditioning, the operational points in terms of how much the ambient air needs to be cooled and how much air needs to be processed are relatively different as compared to the corresponding operational points for general air conditioning. As a result, air conditioning systems and atmospheric water-harvesting systems have historically been viewed as separate, independent systems and have been developed as such. 
       SUMMARY 
       [0005]    The present disclosure features a more-unified system that provides for both air conditioning and atmospheric water-harvesting. In one aspect, a system according to this disclosure has a single compressor and condenser that serve both an air conditioning system, i.e., a system that is configured to operate at design points suitable for air conditioning, and an atmospheric water-harvesting system, i.e., a system that is configured to operate at design points suitable for atmospheric water-harvesting. Such a system has lower capital costs, operational costs, and space requirements than would be the case if separate air conditioning and water-harvesting systems were to be installed and utilized. 
         [0006]    In another aspect, a system according to this disclosure is configured so that maximum water-production or maximum operational efficiency (in terms of water output per unit of electrical energy consumed) can be alternately selected. This may be done manually or according to some desired control scheme that is implemented by a controller, e.g., based on time of day when water consumption is greatest; time of day when energy rates (cost) are highest; etc. Furthermore, although this aspect of the invention can be utilized in a system that provides both air conditioning and water-harvesting, it can also be utilized in connection with a “stand-alone,” dedicated water-harvesting unit to provide generally similar benefits as in the case where it is utilized in connection with a combination air conditioning/water-harvesting system. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0007]    These and other features will become clearer in view of the following disclosure, in which 
           [0008]      FIG. 1  is a schematic, overall system diagram; and 
           [0009]      FIG. 2  is a schematic, overall control diagram for the system shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    An air conditioning and water-harvesting system  10  is illustrated in  FIG. 1 . The system includes an air conditioning subsystem  12  (e.g., a residential or other-sized air conditioning system) and an atmospheric water-harvesting subsystem  14 . In a generally conventional manner, the air conditioning subsystem  12  includes an evaporator  16  that is located within a duct  18  and a vent fan or other air-moving mechanism  20  that causes air to flow through the duct  18 , from inlet end  22  to outlet end  24 , and across the evaporator  16 . Air exiting the duct  18  is provided to a space in which cooled, conditioned air is required, e.g., for the comfort of human or other animal occupants or, perhaps, for keeping electrical components from overheating. Suitably, the air conditioning subsystem  12  includes an air filter  26 , to remove undesirable air-borne particles such as dust, mold, allergens, etc., as well as a condensate pan  28  to collect atmospheric moisture that may have condensed on and dripped off of the evaporator  16 . 
         [0011]    Similarly, in the specifically illustrated embodiment, the atmospheric water-harvesting subsystem  14  includes an evaporator  30  that is located within a duct  32  and a vent fan or other air-moving mechanism  34  that causes air to flow through the duct  32 , from inlet end  36  to outlet end  38 , and across the evaporator  30 . As air flows across the evaporator  30 , it cools substantially; as it does so, it becomes oversaturated with moisture, and moisture contained within the air will condense on the evaporator  30 . 
         [0012]    In more advanced configurations (not illustrated), the ducting arrangement of the atmospheric water-harvesting subsystem  12  could be configured as per the atmospheric water-harvesters disclosed in U.S. Pat. Nos. 7,954,335 and 8,627,673, the contents of both of which are incorporated by reference. According to those two patents, incoming air is precooled to varying degrees before it passes over the evaporator, with the amount of precooling that is provided varying inversely with ambient relative humidity levels since it is easier to extract moisture from air that is heavily laden with moisture such that precooling—with the operational costs or inefficiencies associated with it—becomes less important or beneficial. 
         [0013]    Further still, in alternate embodiments (not illustrated), some of the cooled/chilled air immediately downstream of the evaporator  30  could be ported so as to combine with the cooled-air output from the air conditioning subsystem  12 , thereby helping to cool the room or other environment that is being served by the air conditioning subsystem  12 . Doing so would alleviate some of the cooling load being carried by the evaporator  16 ; on the other hand, system efficiencies attributable to further ducting and/or blowers/fans necessary to “shunt” that cooled/chilled, downstream air might counteract or even negate any such alleviation of the cooling load on the evaporator  16 . Alternatively, cooled/chilled air immediately downstream of the evaporator  30  could be routed to the return air portion of the air conditioning subsystem  12 , where it would help provide the required fresh air requirements for the subsystem. While ducting some of the cooled/chilled air coming off of the water-harvesting evaporator  30  into the room being air-conditioned, as mentioned above, contributes to overall “carrying capacity” of the air conditioning subsystem  12 , “dumping” it into the return allows it to mix with room air and be distributed evenly through the existing air conditioning duct system. 
         [0014]    As further illustrated in  FIG. 1 , the atmospheric water-harvesting subsystem  14  includes a condensate pan or other water-collecting device  40  to collect atmospheric moisture that will have condensed on and dripped off of the evaporator  30  and, suitably, an air filter  42  to remove undesirable air-borne particles such as dust, mold, allergens, etc. from the incoming moisture-supplying airstream, which particles could otherwise foul the evaporator and the product water. Water collected by the water-collecting device  40  is treated downstream in a water-purification system  44 , which may include UV-sterilization, bacteriostatic treatment, re-mineralization, fluoride treatment, etc., to make the product water suitable for human consumption. 
         [0015]    Furthermore, condensate that collects in condensate pan  28  in the air conditioning subsystem may be added to the water that is collected in the water-collecting device  40  to augment the overall water-production output of the system  10 . Depending on the relative arrangement of the subsystems  12  and  14 , the condensate could be transferred from condensate pan  28  to the water-collecting device  40  simply via gravity-feed or, as illustrated, via a water pump  46  and conduit  48 . 
         [0016]    With respect to further refrigeration-related components, the system  10  includes a variable-speed compressor  50  and a condenser  52 . Suitably, the condenser  52  is located within the water-harvesting subsystem duct  32  so that air that has been cooled via the evaporator  30  to yield moisture will cool the condenser  52  and, hence, the refrigerant contained within it. (Depending on system configuration and/or ambient conditions, combining a portion of the air that has been cooled by the evaporator  30  with the cooled-air output from the air conditioning subsystem  12 , as alluded to above, may—i.e., not necessarily will—reduce the condenser-cooling capability of the airflow through the water-harvesting subsystem to such an extent that so “shunting” the cooled air becomes undesirable.) Because the cooling air flowing across the condenser  52  will be heated significantly by the condenser  52 , it is exhausted to an outside location instead of to an interior environment. 
         [0017]    As illustrated schematically, refrigerant flows from the high-pressure discharge side  54  of the compressor  50  to the condenser  52  and then, from the condenser discharge, to a node or junction point  56 . From the junction point  56 , liquid-phase refrigerant is able to flow to both the air conditioning evaporator  16  and the water-harvesting evaporator  30 . On/off (i.e., binary) solenoid valves  58  and  60  are provided to permit or prevent refrigerant from flowing to the evaporators  16  and  30 , respectively. 
         [0018]    Furthermore, an expansion valve  62  is located just upstream of the air conditioning evaporator  16 , and an evaporator pressure regulator  66  is provided in the refrigerant line  68  downstream of the air conditioner evaporator  16 . Together, the pressure regulator  66  and the expansion valve  62  provide fairly close or precise regulation or control over the degree of cooling provided by the air conditioning evaporator  16 ; this is desirable because over-cooling of the air-conditioned air can make it too cold and/or too dry for people within the air-conditioned space to be comfortable. 
         [0019]    Similarly, an expansion valve  64  is located just upstream of the water-harvesting evaporator  30 . However, in contrast to the air conditioning subsystem  12 , no evaporator pressure regulator is provided in the disclosed embodiment to assist in regulating the behavior of refrigerant within the water-harvesting evaporator  30 . This is because the air must be cooled to a significantly lower temperature in order to extract meaningful amounts of drinking water. (Air conditioning systems tend to produce air around 55 degrees Fahrenheit, which has a saturated humidity ratio of 64.6 grains/lb, whereas water-harvesting treats the air to closer to 38 degrees, which is saturated at 33.7 grains/lb, the difference in humidity representing a greater amount of water being collected by the water harvesting system.) Therefore, the water-harvesting evaporator can be operated “wide-open” to achieve maximum possible cooling of the air that flows over it. 
         [0020]    By way of quantifying the configurations of the air conditioning and water-harvesting subsystems in term of their different operating points, the suction temperature for the air conditioning subsystem—i.e., the temperature of the refrigerant in the air conditioning evaporator at its saturation point—will be approximately 50° F. to 60° F., while the suction temperature for the water-harvesting subsystem will be closer to approximately 32° F. to 40° F.; these temperatures dictate or determine the respective evaporator surface temperatures, which will be similar to the refrigerant temperatures. Thus, with the overall system running optimally, the respective expansion valves will be set/configured to throttle to maintain these temperature rises from saturation temperature to the outlet of each respective evaporator. (As for refrigerant pressures within the evaporators, on the other hand, exact values will vary depending on the specific refrigerant that is used.) 
         [0021]    Finally (in terms of the overall refrigeration cycle of the system  10 ), gaseous refrigerant from the air conditioning evaporator  16  combines with gaseous refrigerant from the water-harvesting evaporator  30  at junction or node-point  70 . From there, the refrigerant returns to the suction side  72  of the compressor  50  to begin the cycle once again. 
         [0022]    Furthermore, a number of refrigerant temperature and pressure sensors are located at various points within the system, and data from these sensors are used to regulate overall operation of the system  10 . For example, as noted above, the system can be configured to operate selectively in one of two different modes—a first mode that is configured to produce a maximum amount of water per unit of time, and a second mode that is configured to maximize efficiency in terms of water produced per unit of electricity used—with the operating mode being either manually or, suitably, automatically selected by a controller. Thus, as further illustrated in  FIG. 1 , suction pressure sensor  74  is provided at, or just upstream of, the suction side  72  of the compressor  50 ; and high-side pressure sensor  76 , used in connection with operating in the second, maximum-efficiency mode, is provided at, or just downstream of, the high-pressure discharge side  54  of the compressor  50 . Pressure and temperature sensors  78  measure refrigerant pressure and temperature at the outlet of the water-harvesting evaporator  30 , and these two values are used to regulate/control refrigerant flow through the evaporator  30  with a fairly high degree of precision as noted above. 
         [0023]    On the other hand, corresponding pressure and temperature sensors are not illustrated in association with the air conditioning evaporator  16  since many common air conditioning systems (including, in particular, residential air conditioning systems) use a thermal expansion valve to regulate refrigerant flow through the evaporator. Such thermal expansion valves are fairly simple and are mechanically controlled via a refrigerant-temperature-sensing bulb, which provides a suitable degree of control for air conditioning purposes. 
         [0024]    As illustrated in  FIG. 2 , the variable-speed compressor  50  is the plant that is controlled via the control system (programmable logic controller)  80  using the various parameter values measured by these sensors. Furthermore, as noted above, switch  82  by means of which the operating mode (maximum efficiency or maximum water production) is selected can be controlled by the logic controller  80  or, if desired, by a user-accessible manual override. 
         [0025]    The foregoing disclosure is only intended to be exemplary. Departures from and modifications to the disclosed embodiments may occur to those having skill in the art. The scope of the invention is set forth in the following claims.