Patent Abstract:
A water harvesting and purifying system and method for an automobile. The system automatically collects condensed water from a heat-exchanger in an air-conditioning system. the system filters the condensed water and isolates it in a reservoir. the system boils the isolated water to further purify. The water is then useful for drinking for a predetermined time period, after which the water is purged and the process restarted.

Full Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to water harvesting systems integrated in a vehicle, and more specifically to purification of the harvested water and harvesting of the water when the vehicle is keyed-off. 
       BACKGROUND 
       [0002]    Clean drinking water is not readily available in arid locations, especially for travelers. The cost of infrastructure to provide clean drinking water in arid locations by traditional underground piping may be prohibitive. One solution has been to use stationary water harvesting stations, such as a water-making billboard, to condense water from the air and make it available for drinking. 
         [0003]    The concept of harvesting water from vehicle air-conditioning systems has been disclosed in prior art references, however no automotive manufacturer has provided such a system on a vehicle to date. The prior art discloses the harvesting of water from air-conditioning systems when the vehicle is being driven and the air-conditioning is being used to cool the passenger compartment. There exists a need for a water purification system that may provide clean drinking water in a simple cost effective design. In addition, there exists a need for a vehicle based system that may harvest water while the vehicle is not being driven. 
       SUMMARY 
       [0004]    One aspect of this disclosure is directed to a system for harvesting clean drinking water in a vehicle. The system includes a heat-exchanger, a reservoir fluidly connected with the heat-exchanger and configured to collect water from the heat-exchanger, and a heating element configured to heat water within the reservoir. This system includes a controller coupled with the heating element and programmed to boil the water in the reservoir. 
         [0005]    The system may include a water level sensor disposed within the reservoir. The controller may be further programmed to boil the water in response to the water in the reservoir reaching a predetermined level. The system may also include a valve fluidly disposed between the heat-exchanger and the reservoir. The controller may be coupled with the valve and further programmed to, in response to the water in the reservoir reaching the predetermined level, actuate the valve to inhibit water flow from the heat-exchanger to the reservoir. 
         [0006]    The system may have a temperature sensor disposed in the reservoir. The controller may be coupled with the temperature sensor and further programmed to, in response to the water having a temperature indicative of boiling, maintain the temperature of the water for a predetermined period of time. The predetermined time period may be at least one minute. The controller may also be programmed to purge the water in the reservoir after a second predetermined period of time elapsing from the water having a temperature indicative of boiling. The second predetermined period of time may be at least 12 hours. 
         [0007]    The system may have a display. The controller may be programmed to send information relating to the purging of the water in the reservoir to the display. The system may have an air duct proximate the reservoir to facilitate cooling of the water after being boiled. The system may also have a temperature sensor in the reservoir. The controller may be further programmed to, in response to the water reaching a predetermined temperature below a temperature indicative of boiling, indicate that the water is ready to drink. 
         [0008]    The system may include a dispensing line and a water bottle compartment capable of holding at least one water bottle. The controller may be programmed to fill at least one water bottle. The heat-exchanger may be a condenser. 
         [0009]    The system may be part of a vehicle that has a battery capable of being recharged by plugging it in to an external electric source. The heat-exchanger may be part of an air-conditioning system of such a vehicle capable of being operated by the battery. The controller may be coupled with the battery and the air-conditioning system and further programmed, in response to the battery being recharged by the external electric source, operate the air-conditioning system to generate water from the heat-exchanger. 
         [0010]    Another aspect of this disclosure is directed toward a method of providing clean drinking water in a vehicle. The method includes a step of operating an air-conditioning system during a key-off time period. The method also includes the step of collecting the condensed water from a condenser in the air-conditioning system, and then boiling the condensed water. 
         [0011]    The step of collecting condensed water may include collecting a predetermined amount of condensed water, and isolating the collected amount of condensed water from additional waters that may condense off of the condenser. The method may include filtering the condensed water. The method may include purging the boiled water after a predetermined time period. Alternatively, the method may include re-boiling the boiled water after the predetermined time period. The time period may be at least 12 hours. 
         [0012]    The step of operating an air-conditioning system during a key-off period may include providing an external power source to the vehicle. 
         [0013]    The above aspects of this disclosure and other aspects will be explained in greater detail below with reference to the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a diagrammatic illustration of a vehicular water harvesting and purification system. 
           [0015]      FIG. 2  is a flowchart illustrating an example of automatic water harvesting. 
           [0016]      FIG. 3  is a flowchart illustrating an example of automatic water purification. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The illustrated embodiments are disclosed with reference to the drawings. However, it is to be understood that the disclosed embodiments are intended to be merely examples that may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but as a representative basis for teaching one skilled in the art how to practice the disclosed concepts. 
         [0018]      FIG. 1  shows a vehicle  10  having a passenger compartment  12 . Vehicle  10  may be a vehicle with an engine  14 , an electric machine  16 , or both cooperating as a prime mover of the vehicle. The Engine  14  and electric machine  16  represent any machine designed to convert energy into useful mechanical motion. The engine  14  may be a gasoline engine, a diesel engine or any form of an internal combustion engine that burns fuel. The electric machine  16  may be an electric motor. As such, the vehicle may be a traditional engine only vehicle, a battery-only electric vehicle (BEV), or may be a hybrid electric vehicle (HEV). 
         [0019]    The vehicle  10  may have a battery  18 . The battery  18  may be a high voltage traction battery that coupled with the electric machine  16  may provide the energy for the electric machine to provide motion. The vehicle  10  may have a plug-in cable  20 . The plug-in cable  20  is configured to connect the battery  18  to an external power source (not shown). Thus battery  18  is capable of being recharged by plugging the plug-in cable  20  into an external power source. 
         [0020]    Vehicle  10  has an air-conditioning system  26 . The air-conditioning system  26  has a heat-exchanger  28  disposed outside of the passenger compartment  12 , a compressor  30 , and a heat-exchanger  32  disposed within the passenger compartment  12 . The heat exchanger  28  located outside of the passenger compartment  12  may be referred to as a condenser  28 . The heat exchanger  32  located within the passenger compartment  12  may be referred to as an evaporator  32 . The compressor  30  may be driven by the engine  14 , such as by the use of an auxiliary drive belt off a crankshaft (not shown), or an auxiliary drive belt off the electric machine  16 , or by having a separate compressor motor (not shown). The compressor motor may be provided energy from the high voltage traction battery  18  or from a 12 volt battery (not shown). 
         [0021]    Other components of an air-conditioning system  26  may be present in the system, such as a pressure regulator, an expansion valve, an accumulator, a receiver, a desiccant filter, or the like. The air-conditioning system  26  may also include an electronic control system (not shown) and a series of ducts  34  to route conditioned air from the evaporator  32  into the passenger compartment  12 . A fan  36  may be employed adjacent the heat-exchanger  28  to aid in improved airflow across heat-exchanger  28 . A second fan  38 , or a group of fans  38 , may be disposed within the series of ducts  34  to aid in airflow across the heat-exchanger  32 . 
         [0022]    As a vehicle air-conditioning system  26  runs, water may condense on the heat exchangers  28 ,  32 . Condensation is generally known as a change in the state of water vapor to liquid water when in contact with any surface. Generally when the air-conditioning system  26  is used to cool the passenger compartment, condensation may occur on the heat-exchanger  28  disposed outside of the passenger compartment  12 , although condensation may occur on the heat-exchanger  32  located within the passenger compartment as well. The heat-exchanger  28  located outside of the passenger compartment  12  is in fluid contact with the ambient environment (or an equivalent environment within an engine compartment adjacent the ambient environment. The water that condenses on heat-exchanger  28  is from water vapor formerly held within air surrounding the heat-exchanger  28 . 
         [0023]    Vehicle  10  has a water harvesting and purification system  44 . A collector  46  is located near the heat-exchanger  28  and is configured to collect condensed water from the heat-exchanger  28 . The collector may be located below the heat-exchanger  28  and gravity may be used to collect the water. The collector  46  may be fluidly connected to a collection valve  48  via a collector line  50 . Collection valve  48  may be a three-way valve, or a series of T-shaped valves. Collection valve  48  may also be an electric actuated valve  48 . Collection valve  48  may be used to divert water from the collector  46  to a first fluid flow path  52  allowing water to flow from the heat-exchanger  28  to a reservoir  54 . Said another way, the collection valve  48  may be fluidly disposed between the heat-exchanger  28  and the reservoir  54 . Collection valve  48  may also be used to divert water from the collector  46  to a second fluid flow path  56  allowing water to flow from the heat-exchanger  28  to a drain  58  and outside of the vehicle  10 . 
         [0024]    The first fluid flow path  52  may include a filter  60 . The filter  60  may be a mesh screen which is used for the separation of solids from fluids by interposing a medium through which the fluid can pass but not solids larger than the mesh sizing. The filter  60  may also be a chemical or ultraviolet filtration device which may be used to filter out undesirable bacteria, organic carbons, or the like. The filter  60  may be a number of filters  60 . The first fluid flow path  52  may also include a pump  62 . The filter  60  may be located before or after the pump  62 . The filter  60  may also be located before the collection valve  48 . Likewise, the pump  62  may also be located before the collection valve  48 . The system may also operate without a filter  60  or pump  62 , or provide more than one filter  60  or pump  62  at any location within the harvesting and purification system  44  to provide desired filtration, to move water, or to provide pressure where desired. Thus the filter  60 , if used, may be fluidly disposed between the heat-exchanger  28  and the reservoir  54 . 
         [0025]    The reservoir  54  is fluidly connected with the heat-exchanger  28  such that the reservoir  54  is configured to collect water from the heat-exchanger  28 . The reservoir  54  may be located inside or outside of the passenger compartment  12 . The reservoir  54  may have a water level sensor  66 . The water level sensor  66  may be a float  66  disposed within the reservoir  54  which floats on accumulated water  68  within the reservoir  54 . The reservoir  54  may have a heating element  70  configured to heat the accumulated water  68 . The heating element  70  may be disposed within the water  68 , or may be disposed in a wall of the reservoir  54 . The accumulated water  68  may also be pre-heated by having the collector line  50  or first fluid flow path  52  warmed by other heat generating sources. For example, the collector line  50  may pass through or near the engine  14 . 
         [0026]    The reservoir  54  has a temperature sensor  72  configured to provide a temperature of the accumulated water  68 . The temperature sensor  72  may be submerged in the water  68 , may be in a wall of the reservoir  54 , or may be part of the heating element  70 . The heating element  70  may be used to heat the accumulated water  68 . The heating element  70  may be used to boil the accumulated water  68 . The boiling of the water  68  may be done to remove additional impurities. The air-conditioning system  26  may be used to add heat to the water  68 . After heating of the water  68 , ducts  34  from the air-conditioning system  26  may be used to cool the water  68 . A duct  34  of the multiple ducts  34  may be located proximate the reservoir  54  configured to facilitate cooling of the water  68 . Additional cooling devices (not shown) may be used to cool the water  68  after being boiled. 
         [0027]    The reservoir  54  may have an outlet valve  73 . The outlet valve  73  may be a three way valve similar to the collection valve  48 . The outlet valve  73  may be actuated to allow the water  68  to flow out of the reservoir  54 . A first dispensing line  74  may extend from the outlet valve  73  to a first spout  76  in the passenger compartment  12 . A second dispensing line  78  may extend from the outlet valve  73  to a second spout  80  outside of the passenger compartment  12 . The reservoir  54  may be disposed within or outside of the passenger compartment  12 . The first spout may be opened and closed by a first dispensing valve  82 . The second spout  80  may be opened and closed by a second dispensing valve  84 . The first and second valves  82 ,  84  may be manual valves or electric actuated valves. 
         [0028]    The first spout  76  may be configured to fill at least one water bottle  86 . The water bottle  86  may be located within a water bottle compartment  88 . The water bottle  86  may be a 12 ounce water bottle and the water bottle compartment  88  may be able to hold six water bottles  86 . The water bottle compartment  88  may be sized to fit six water bottles  86 , three wide and two deep. The first spout  76  may be moveable via a first spout motor (not shown) to fill each water bottle  86 . Alternatively, the water bottles  86  may be on a rotatable tray or conveyor tray and each moveable to the first spout  76 . The water bottle compartment  88  may be cooled by a duct  34  from the number of ducts  34  of the air-conditioning system  26 . The water bottle compartment  88  may also be heated by a duct  34  from the number of ducts  34  of the air-conditioning system  26 . The water bottle compartment  88  may be cooled by a separate refrigeration unit (not shown). The water bottle compartment  88  may be disposed in a dash panel or instrument panel adjacent, or in place of, a glove compartment. The system  44  provides a removable bottle  86  with purified water within reach of a driver of the vehicle  10 . 
         [0029]    The water harvesting and purification system  44  may also have a display  94  for relating information about the water harvesting and purification system  44  to a user. Information may include such data as amount or temperature of the accumulated water  68  in the reservoir  54 , whether the accumulated water  68  has been purified, time elapsed since the accumulated water  68  has been purified, or the like. The display  94  may be located in a location visible to a user in the passenger compartment  12 . The display  94  may be an existing display in an infotainment system (not shown). The display  94  may be located in a location visible to a user outside of the passenger compartment  12 . An exterior display  94  may be within the passenger compartment  12  visible through a window, may be a projector that projects the data onto a window, or may be a series of lights in the exterior surface of the vehicle  10 . 
         [0030]    An ignition  96  may be connected to the vehicle  10 . The ignition  96  may be controlled by a user to key-on and start the vehicle  10 . When the vehicle  10  is key-on and started, either the engine  14 , motor  16 , or both may be used to propel the vehicle  10 . As well, in the key-on state, the air-conditioning system  26  may be used to cool the vehicle and provide condensed water for the water harvesting and purification system  44 . The user may also use the ignition  96  to key-off and stop the vehicle  10 . The engine  14  and motor  16  may not propel the vehicle in a key-off state. A traditional key  98  is shown that may be inserted into the ignition  96  and used to key-on and key-off the vehicle  10 , however the ignition may not need an inserted key  98 , as it may be a button or have a proximity key, or the like. 
         [0031]    The water harvesting and purification system  44  may operate the air-conditioning system  26  to generate condensed water even when the vehicle  10  is in a key-off state. The water harvesting and purification system  44  may operate the air-conditioning system  26  to generate condensed water even when the vehicle  10  has the plug-in cable  20  plugged into an external power source to recharge the battery  18 . The water harvesting and purification system  44  may utilize the external power source to provide the energy necessary to operate the air-conditioning system  26  while the vehicle  10  is key-off. 
         [0032]    A controller  100  may automate the water harvesting and purification system  44 . The controller  100  may be coupled with the engine  14 , if one is in the vehicle  10 , as indicated by communication line  114 . The controller  100  may be coupled with the motor  16 , if one is in the vehicle  10 , as indicated by communication line  116 . The communication lines  114 ,  116  may communicate data to the controller  100  such as current use of the engine and/or motor  14 ,  16 , among others. 
         [0033]    The controller  100  may be coupled with the battery  18 , as indicated by communication line  118 . The communication line  118  may communicate data such as current state of charge, battery charge level, or whether the battery  18  is being recharged by an external power source (via plug-in cable  20 ), among others. The controller  100  may be coupled with the compressor  30 , as indicated by communication line  130 . Communication line  130  may include data about the operation of the air-conditioning system  26 , as well as provide a conduit for the controller  100  to control the operation of the compressor  30 . The communication line  130  may also convey electrical current from the battery  18  to operate the compressor  30  when the engine  14  or motor  16  are not in use. The controller  100  may be coupled with the air-conditioning system  26 , via the compressor  30 , and programmed to, in response to the battery  18  being charged by an external electric source, operate the air-conditioning system  26  to generate water from the heat-exchanger  28 . 
         [0034]    The controller  100  may be coupled with the collection valve  48 , as indicated by communication line  148 . The controller  100  may be programmed to actuate the control valve  48  to switch from the first fluid flow path  52  to the reservoir  54  or the second fluid flow path  56  to the drain  58 . The controller  100  may be programmed to, in response to the water  68  in the reservoir  54  reaching a predetermined level, actuate the control valve  48  to inhibit water flow from the heat-exchanger  28  to the reservoir  54 . The controller  100  may be programmed to, in response to the water  68  in the reservoir  54  reaching a predetermined level, switch the collection valve  48  from the first fluid flow path  52  to the second fluid flow path  56 . The controller  100  may be programmed to, in response to the water  68  in the reservoir  54  reaching a predetermined level, turn off the air-conditioning system  26  if being run during key-off/plug-in state. 
         [0035]    The controller  100  may be coupled with the water level sensor  66 , as indicated by communication line  166 . The communication line  166  may convey data relating to the level of water  68  in the reservoir  54 . The communication line  166  may convey the water  68  in the reservoir  54  reaching a predetermined level. The predetermined level may be different for each programmed operation. The predetermined level may be at least 12 ounces. The predetermined level may be greater than 72 ounces (enough to fill six 12 ounce bottles). The controller  100  may be coupled with the pump  62  via communication line  162 . The controller  100  may be programmed to actuate pump  62  to move water or provide pressure within the water harvesting and purification system  44 . The controller  100  may utilize the pump  62  to provide the pressure needed for the water  68  to reach the predetermined level. 
         [0036]    The controller  100  may be coupled with the heating element  70  via communication line  170 . The controller  100  may utilize the heating element  70  to heat the water  68 . The controller  100  may utilize the heating element  70  to boil the water  68 . The controller  100  may be programmed to, in response to the water  68  in the reservoir  54  reaching a predetermined level, boil the water  68 . The controller  100  may be coupled with a temperature sensor  72  via communication line  172 . The controller  100  may be programmed to, in response to the water  68  having a temperature indicative of boiling, maintain the temperature of the water for a predetermined period of time. The predetermined time period may be at least one minute. The controller  100  may be further programmed to, in response to the water reaching a predetermined temperature below a temperature indicative of boiling, indicate that the water  68  is ready to drink. 
         [0037]    The controller  100  may be coupled with the outlet valve  73  via communication line  173 . The controller  100  may actuate the outlet valve  73  to provide water to the first or second fluid flow paths  74 ,  78 , or to maintain water  68  in the reservoir  54  until purified or until at a desired temperature. The controller  100  may be coupled with the first dispensing valve  82  via communication line  182 . the controller  100  may be programmed to open the first dispensing valve  82  to automatically fill a water bottle  86 . Alternatively, a user may initiate the opening and closing of the first dispensing valve  82  by a touch sensitive button, or the like (not shown). 
         [0038]    The controller  100  may be coupled with the second dispensing valve  84  via communication line  184 . the controller  100  may be programmed to open the second dispensing valve  84  to automatically purge water from the reservoir. Alternatively, a user may initiate the opening and closing of the second dispensing valve  84  by a touch sensitive button, or the like (not shown). The second dispensing valve  84  in conjunction with the second spout  80  provide an option of filling up any container outside of the vehicle  10 . 
         [0039]    The controller  100  may be further programmed to purge the water  68  in the reservoir after a second predetermined period of time elapsing from the water having a temperature indicative of boiling. The second predetermined period of time may be at least 12 hours. The controller may be coupled with the display  94  via communication line  194 . The controller  100  may be programmed to display information on the display  94 . The display  94  may display information relating to the purging of the water  68 , such as a countdown until the next purge. The display  94  may also show information relating the amount or temperature of the accumulated water  68  in the reservoir  54 , whether the accumulated water  68  has been purified, time elapsed since the accumulated water  68  has been purified, number of water bottles  86  filled, different operating parameters of the system, or the like. 
         [0040]      FIG. 2  shows an example of control logic, utilizing the above disclosed components, for the harvesting of water. Decision diamond  200  determines whether a water harvest mode has been selected by a user. If no water harvest mode has been selected, the logic flow moves to end block  202 . Decision diamond  200  allows the automatic harvesting of water to be turned off. If the water harvest mode has been selected, the flow moves to decision diamond  204 . 
         [0041]    Decision diamond  204  determines whether water in a reservoir has reached a predetermined level. The predetermined level may be a full line. If the reservoir is full, the logic flow moves to action block  206 , then to action block  208 , and then to end block  202 . Action block  206  actuates a collection valve to send any water condensed off a heat-exchanger to a drain. Action block  208  discontinues the water harvest mode. Action block  208  will turn off any and all other action blocks in this strategy flow diagram. If the reservoir is not full, the logic flow moves to action block  210 . 
         [0042]    Action block  210  actuates the collection valve to direct water from the heat-exchanger to the reservoir. The logic flow then moves to decision diamond  212  where it is determined whether an air-conditioning system is operating. If an air-conditioning system is operating, then the flow returns to decision diamond  200 . This allows for a do-loop until the reservoir is filled or the water harvest mode is turned off by a user. If the air-conditioning system is not operating, the logic flow moves to decision diamond  214 . 
         [0043]    Decision diamond  214  determines whether the vehicle is running. If the vehicle is key-on and running, then the logic flow moves to action block  216 . Action block  216  turns on the air-conditioning system and the flow returns to decision diamond  200 . This allows for a do-loop in the logic flow until the reservoir is filled, the harvest mode turned off, or the vehicle turned off. If the vehicle is key-off, then the logic flow moves to decision diamond  218 . 
         [0044]    Decision diamond  218  determines whether the vehicle is plugged in to an external power source. If the vehicle is plugged in, then the logic flow moves to action block  220  and turns on the air-conditioning system to harvest water from the ambient air. The external power source provides the energy needed to run the air-conditioning system without draining a battery or gas tank. After action block  220 , the logic flow returns to decision diamond  200 . This allows for a do-loop in the logic flow until the reservoir is filled, the harvest mode turned off, the vehicle is unplugged, or the vehicle is keyed back on. If the vehicle is not plugged in, then the logic flow returns to decision diamond  200 . This allows for a do-loop in the logic flow until the reservoir is filled, the harvest mode turned off, the vehicle is keyed back on, or the vehicle is plugged in. 
         [0045]      FIG. 3  shows an example of control logic, utilizing the above disclosed components, for the purification of water. Decision diamond  300  determines whether water in a reservoir has reached a predetermined level. The predetermined level may be a full line. If the reservoir is not yet full, the logic flow moves to action block  302 . Action block  302  actuates a collection valve to send any water condensed off a heat-exchanger to the reservoir and then returns the logic flow to decision diamond  300 . This provides a do-loop in the logic flow until the reservoir fills. If the reservoir is full, the logic flow moves to action blocks  304 ,  306 ,  308 . 
         [0046]    Action block  302  activates the collection valve to send water condensing off an evaporator to the drain and not to the reservoir. This allows for the water accumulated in the reservoir to be isolated. Action block  306  provides for the water in the reservoir to be brought to a boil. This allows for the water to be purified by the heat. Action block  306  may have a duration of at least one minute. Action block  308  starts a purge counter on the boiled water. after action blocks  304 ,  306 ,  308 , the logic flow moves to decision diamond  310 . 
         [0047]    Decision diamond  310  determines whether the water in the reservoir has been emptied. If the water has been emptied, then the logic flow moves to action block  302  and back to decision diamond  300 . This provides for a do-loop in the logic flow to allow the system to automatically fill itself and purify the accumulated water and refill itself and re-purify newly accumulated water so long as the older purified water has been discarded or used. If the reservoir still has some water remaining in it, then the logic flow moves to decision diamond  312 . 
         [0048]    Decision diamond  312  determines whether the purge counter has reached a predetermined time. In other words, it determines how much time has elapsed since the water was purified. The predetermined time may be at least 12 hours. If the predetermined time has not elapsed, then the logic flow returns to decision diamond  310 . This allows for a do-loop in the logic flow until all of the water in the reservoir is discarded or used, or until the purge counter has reached its limit. If the purge counter has reached its limit, then the logic flow moves to action block  314 . Action block  314  purges all of the water from the reservoir. This provides for the discarding of unused water and the prevention of the water in the reservoir from becoming un-purified. After action block  314 , the logic flow returns to action block  302  and decision diamond  300 . this allows for a do-loop in the logic flow to refill the reservoir and re-purify the water. 
         [0049]    This logic flow chart may also include an action block of filtering the water (not shown) before or after action block  306  of boiling the water. The filtering of the water may include a mesh screen or other filtering techniques such as ultraviolet light or the like. 
         [0050]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the disclosed apparatus and method. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure as claimed. The features of various implementing embodiments may be combined to form further embodiments of the disclosed concepts.

Technology Classification (CPC): 8