Water recovery in desiccant enhanced evaporative cooling systems

Abstract

Disclosed are systems and methods for conditioning air for an enclosed space using a liquid to air membrane energy exchanger (LAMEE) as a pre-dryer for removing moisture from an air stream with a desiccant flowing through the LAMEE. The LAMEE can be arranged inside a plenum configured to receive and condition an air stream. The LAMEE can be used in combination with a regeneration system to recover water from the dilute desiccant exiting the LAMEE for use as make up water for one or more evaporative coolers in the conditioning system. This can reduce or eliminate an external water supply for operation of the one or more evaporative coolers. The conditioning system can operate effectively with only a portion of the dilute desiccant being regenerated. In an example, a mixing tank can be used to mix the dilute desiccant (exiting the LAMEE) with a concentrated desiccant stream from

1 . A system for conditioning air for an enclosed space, the system comprising:
 a plenum having a plenum inlet and outlet, the plenum configured to direct an air flow path from the plenum inlet to the plenum outlet;   a liquid-to-air membrane energy exchanger (LAMEE) arranged inside the plenum, the LAMEE comprising a desiccant flow path separated from the air flow path by a membrane, the LAMEE configured to circulate a desiccant through the desiccant flow path and remove water from air in the air flow path, wherein an energy reduction of the air in the air flow path between a LAMEE inlet and outlet is about equal to an energy gain of the desiccant in the desiccant flow path between the LAMEE inlet and outlet, and essentially all of the energy removed from the air is transferred to the desiccant;   a regeneration system in fluid connection with the LAMEE and having a regeneration inlet configured to receive a dilute desiccant stream, the regeneration system configured to separate water from desiccant in the dilute desiccant stream, the regeneration system having a first outlet for discharging a concentrated desiccant stream and a second outlet for discharging a water stream; and   one or more cooling components arranged inside the plenum, wherein at least a portion of the water stream from the regeneration system is used by the one or more cooling components as make up water for operation of the one or more cooling components.   
     
     
         2 . The system of  claim 1  wherein the regeneration system comprises a regeneration unit that thermally separates the water and the desiccant in the dilute desiccant stream. 
     
     
         3 . The system of  claim 2  wherein the regeneration system comprises a heat exchanger arranged upstream of the regeneration unit and configured to increase a temperature of the dilute desiccant stream before the dilute desiccant stream enters the regeneration unit. 
     
     
         4 - 6 . (canceled) 
     
     
         7 . The system of  claim 1  wherein the regeneration system comprises a regeneration unit that utilizes non-thermal energy to separate the water and the desiccant in the dilute desiccant stream. 
     
     
         8 . The system of  claim 1  wherein the concentrated desiccant stream is transported to a desiccant tank configured to receive the concentrated desiccant stream and a dilute desiccant stream exiting the LAMEE. 
     
     
         9 . The system of  claim 8  wherein an output stream from the desiccant tank is at a concentration higher than a concentration of the desiccant in the dilute desiccant stream and lower than a concentration of the desiccant in the concentrated desiccant stream. 
     
     
         10 . The system of  claim 9  wherein the output stream from the desiccant tank is transported to at least one of the regeneration system and to the LAMEE for recirculation. 
     
     
         11 . The system of  claim 10  further comprising a modulating valve configured to control a distribution of the output stream from the desiccant tank to the regeneration system and to the LAMEE. 
     
     
         12 - 14 . (canceled) 
     
     
         15 . The system of  claim 8  wherein a first portion of the dilute desiccant stream exiting the LAMEE is transported to the desiccant tank and a second portion of the dilute desiccant stream exiting the LAMEE is transported to the regeneration system. 
     
     
         16 . The system of  claim 15  wherein the first and second portions are variable during operation of the system. 
     
     
         17 - 18 . (canceled) 
     
     
         19 . The system of  claim 1  wherein the LAMEE is a two-fluid. LAMEE having a first fluid and a second fluid, and wherein the first fluid is the air in the air flow path and the second fluid is the desiccant in the desiccant flow path. 
     
     
         20 . The system of  claim 1  wherein the one or more cooling components comprises an evaporative cooler arranged downstream of the LAMEE. 
     
     
         21 . The system of  claim 20  wherein a quantity of water from the regeneration system is sufficient as the make up water for operation of the evaporative cooler such that the evaporative cooler operates without an external water supply. 
     
     
         22 . The system of  claim 20  wherein the LAMEE arranged inside the plenum is a first LAMEE, and the evaporative cooler arranged downstream is a second LAMEE. 
     
     
         23 . (canceled) 
     
     
         24 . The system of  claim 20  wherein the one or more cooling components comprises an evaporative cooler configured to cool the desiccant prior to circulating the desiccant through the LAMEE. 
     
     
         25 . (canceled) 
     
     
         26 . The system of  claim 20  further comprising a liquid to air heat exchanger (LAHX) arranged between the LAMEE and the evaporative cooler, the LAHX configured to pre-cool the air prior to passing the air through the evaporative cooler. 
     
     
         27 - 28 . (canceled) 
     
     
         29 . A system for conditioning air for an enclosed space, the system comprising:
 a plenum configured to direct air from an inlet to an outlet thereof;   a desiccant dryer liquid-to-air membrane energy exchanger (LAMEE) arranged inside the plenum and configured for the air to pass there through, the desiccant dryer LAMEE configured to use a desiccant flowing there through to remove water from the air, the desiccant and air being separated in the LAMEE by a membrane, wherein the LAMEE facilitates an energy exchange between the air and the desiccant, and the desiccant collects essentially all of the energy removed from the air;   an evaporative cooler arranged inside the plenum downstream of the desiccant dryer LAMEE and configured for the air to pass there through, the evaporative cooler configured to cool at least one of the air and water circulating through the evaporative cooler; and   a fluid circuit coupled to the desiccant dryer LAMEE and the evaporative cooler, the fluid circuit comprising a regenerator configured to separate water and desiccant in a desiccant stream, wherein the fluid circuit is configured to transport at least a portion of the water removed from the air by the desiccant dryer LAMEE and separated in the regenerator to the evaporative cooler for use as make up water for operation of the evaporative cooler.   
     
     
         30 . The system of  claim 29  wherein the fluid circuit receives an output desiccant stream from a desiccant tank in fluid connection with an outlet of the LAMEE. 
     
     
         31 . The system of  claim 30  wherein the desiccant tank is in fluid connection with an outlet of the regenerator such that the desiccant tank receives a concentrated input desiccant stream discharged from the regenerator and a dilute input desiccant stream exiting the LAMEE. 
     
     
         32 . The system of  claim 31  wherein the fluid circuit is a first desiccant circuit and the system further comprises a second desiccant circuit, the LAMEE being contained within the second desiccant circuit, and wherein the output desiccant stream from the desiccant tank is directed to a modulating valve configured to distribute the output desiccant stream to the first desiccant circuit and the second desiccant circuit. 
     
     
         33 . (canceled) 
     
     
         34 . The system of  claim 29  wherein the regenerator comprises a thermal. separation unit. 
     
     
         35 . The system of  claim 34  wherein the regenerator comprises one or more heat sources to increase a temperature of the desiccant stream prior to passing the desiccant stream into the thermal separation unit. 
     
     
         36 - 39 . (canceled) 
     
     
         40 . The system of  claim 29  wherein the fluid circuit comprises a concentrated desiccant storage tank configured to receive a concentrated desiccant stream output from the regenerator. 
     
     
         41 - 42 . (canceled) 
     
     
         43 . The system of  claim 29  wherein the fluid circuit comprises a distilled water storage tank configured to receive a distilled water output stream from the regenerator and store the distilled water for delivery to the evaporative cooler as needed for make up water. 
     
     
         44 - 45 . (canceled) 
     
     
         46 . A method of conditioning air for an enclosed space, the method comprising:
 directing air through a process plenum having a plenum inlet and outlet;   directing the air through a liquid-to-air energy exchanger (LAMEE) arranged inside the plenum;   directing a desiccant through the LAMEE, the desiccant and air separated by a membrane of the LAMEE;   transferring energy in the LAMEE from the desiccant to the air, an energy reduction of the air between a LAMEE inlet and outlet being about equal to an energy gain of the desiccant between the LAMEE inlet and outlet, and transferring energy in the LAMEE includes removing water from the air using the desiccant, a first concentration of water in the desiccant being lower at a LAMEE inlet compared to a second concentration of water in the desiccant at a LAMEE outlet, the desiccant at the LAMEE outlet being a dilute desiccant;   regenerating a portion of the dilute desiccant in a regenerator to separate the water from the desiccant;   directing a concentrated desiccant exiting the regenerator to a fluid circuit for the desiccant dryer LAMEE; and   directing distilled water from the regenerator to one or more evaporative coolers in the conditioning system.   
     
     
         47 - 69 . (canceled)