Patent Publication Number: US-11653600-B1

Title: Grain bin conditioning system using headspace air

Description:
BACKGROUND 
     Grain bins are commonly used in agriculture to dry and store agricultural products. It is common practice to dry agricultural products to achieve desired safe storage moisture content to avoid mold growth at high harvest moisture content. This has generally been done by introducing heated or unheated ambient air into to grain bins until the desired moisture content is achieved. 
     SUMMARY 
     At a high level, the technology described herein relates to regulating the relative humidity of air used for conditioning the moisture content of an agricultural product using an air conditioning system. The air conditioning system receives high relative humidity (RH) headspace air from a headspace of a grain bin and mixes the high RH headspace air with low RH ambient air to get optimum RH for conditioning. The air mixture comprising the headspace air and the ambient air is mixed to achieve a target relative humidity level, where the target relative humidity level better regulates the moisture content of the agricultural product to help prevent over or under drying. 
     To do so, a controller modifies a valve that controls the amount of headspace air receiving into a mixer through the headspace air through a headspace air supply line. The controller modifies a valve that controls the amount of ambient air receiving into the mixer through the ambient air through an ambient air supply line. An air mixture comprising the received high RH headspace air and the received low RH ambient air comprises a relative humidity level that is equal to a target relative humidity level that depends on the grain type. The air mixture having the target relative humidity level is provided to a grain bin plenum to permeate through the agricultural product to regulate the agricultural product&#39;s moisture content. 
     This summary is intended to introduce a selection of concepts in a simplified form that are further described below in the detailed description section of this disclosure. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be an aid in determining the scope of the claimed subject matter. 
     Additional objects, advantages, and novel features of the technology will be set forth in part in the description that follows, and in part, will become apparent to those skilled in the art upon examination of the following or learned by practice of the technology. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present technology is described in detail below with reference to the attached drawing figures, wherein: 
         FIG.  1    is an example air conditioning system for regulating moisture content of an agricultural product in a grain bin, in accordance with an embodiment described herein; 
         FIG.  2    is an example process of regulating moisture content in an agricultural product stored in a grain bin, which can be performed by the air conditioning system of  FIG.  1   , in accordance with an aspect described herein; 
         FIG.  3    is an example operating environment for a controller suitable for instructing components of the air conditioning system of  FIG.  1    to perform operations, in accordance with an embodiment described herein; 
         FIG.  4    is a computing device suitable for use as the controller of  FIG.  3   , in accordance with an embodiment described herein; and 
         FIG.  5    is a block diagram illustrating operations that can be performed by the controller of  FIG.  3   , in accordance with an embodiment described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Moving natural air into an agricultural product stored in a grain bin is a common method used to condition agricultural product. Agricultural product regulation can include processes such as drying, rehydrating, cooling, warming, and the like. A common term used for drying agricultural products in a grain bin is “in-bin natural air drying” (NAD). 
     As an example, corn is a type of agricultural product dried using in-bin NAD. Corn is harvested at a moisture content range of around 18-22% and dried to safe storage moisture of about 15%. In a typical natural air conditioning system, ambient air is pumped into a plenum of the grain bin, where ambient air then flows through the corn. The ambient air carries out moisture from the corn, and into to the headspace, where the now moist air exits via vents in the grain bin. Normally, three zones in the grain mass during NAD can be identified: a dried zone, a drying zone, and a wet zone. 
     NAD or Natural Air Hydration (NAH) typically uses ambient air for drying and rehydration, or for other condition processes. Generally, drying is done to bring high harvest moisture to safe storage moisture, which is around 65% relative humidity (RH). Rehydration is done to bring over-dried product to a marketable safe moisture. The temperature and RH of the ambient air fluctuate throughout the day and night. That is, in one day, only some hours have good conditioned air for drying, while other hours have good conditioned air for hydrating. 
     Conventionally, fans are turned on when there is good conditioned air to move it through into the agricultural product in the grain bin. One of the current problems with automatic bin management system strategies is that, once the bottom layer reaches a target moisture content, an operational time window based on air relative humidity is narrowed down to avoid over-drying of bottom layer, since systems generally require the ambient air to reach a temperature and relative humidity level that is considered good conditioned air for drying, rehydrating, and so forth. 
     As a result, some automatic bin management systems that control the air conditioning process do not operate during hydrating hours (unproductive air) for drying or during drying hours (unproductive air) for hydrating. The operational window of time is particularly narrow once a bottom layer of the agricultural product reaches a target moisture content. To minimize over-drying or over-wetting the bottom layer, the operational time in which ambient air can be used is fairly limited. This period depends on the local weather in that location. 
     The present technology offers improvements over the existing systems by mixing headspace air from the grain bin, which generally has a high relative humidity compared to the plenum air, with the ambient air to achieve a target RH or the equilibrium moisture content (EMC) level for the mixed air, which is then provided into the grain bin for conditioning the agricultural product. By mixing the headspace air in various ratios with the ambient air, the operational time in which good conditioned air can be provided to the agricultural product within the grain bin is prolonged. This ultimately allows more runtime for the system, thus reducing the time it takes to condition the agricultural product as desired, while at the same time, reducing the risk of over-drying or over-wetting parts of the agricultural product nearest the grain bin plenum where the air is introduced. 
     To achieve these benefits, an air conditioning system is provided that mixes headspace air from the grain bin or high RH air from humidifier (separate water source) with low RH ambient air. The system comprises a headspace air supply line that receives headspace air from the grain bin headspace and moves the air through the headspace air supply line into a mixer. Additionally, if the headspace air RH is low, high RH air gets from the humidifier attached to the water source. An ambient air supply line receives ambient air relative to the grain bin, e.g., from any air source external from the grain bin, such as natural air. The ambient air supply line moves the ambient air into the mixer. In one embodiment, both the headspace air and ambient air are respectively drawn through the headspace air supply line and an ambient air supply line by way of a fan. 
     The mixer provides a space where the headspace air and the ambient air are mixed. The ratio of the amount of headspace air and ambient air being mixed can be determined by a controller, which operationally controls a headspace air valve and an ambient air valve. In turn, this respectively adjusts a headspace airflow rate and an ambient airflow rate, thus controlling the ratio of headspace air and ambient air entering the mixer. The ratio can be determined so that the mixed air achieves a target RH level. The target RH level can be determined based on the type of agricultural product in the grain bin and the target moisture content of the agricultural product, which is to be achieved or maintained. Once mixed, a fan can blow the air mixture into a plenum of the grain bin so that it moves through and conditions the agricultural product. 
     It will be realized that the systems previously described are only examples that can be practiced from the description that follows, and it is provided to more easily understand the technology and recognize its benefits. Additional examples are now described with reference to the figures. 
     Turning now to  FIG.  1   ,  FIG.  1    provides an example air conditioning system  100  for use with grain bin  102  to condition agricultural product  104  stored within grain bin  102 .  FIG.  1    provides for a cross-sectional view of grain bin  102 . In general, a grain bin, such as grain bin  102 , may be any area suitable for storing an agricultural product, such as agricultural product  104 . Among other storage systems, this can include silos, elevators, storage containers, trench silos, and so forth. Agricultural products may be any product of agriculture, such as wheat, corn, soybeans, rice, legumes, nuts, barley and so forth. 
     As illustrated in  FIG.  1   , grain bin  102  comprises headspace  106 . Headspace  106  may comprise an area within grain bin  102  above agricultural product  104  stored within grain bin  102 . 
     Under some conditions, headspace air  108  within headspace has a RH level that is greater than a RH level of ambient air  110 . This is generally due to the air within grain bin  102  picking up more moisture as it permeates through agricultural product  104  and enters headspace  106 . 
     In  FIG.  1   , air conditioning system  100  comprises headspace air supply line  112 . Headspace air supply line  112  generally facilitates the movement of headspace air  108  from headspace  106  to mixer  114 . Headspace air supply line  112  can be formed, at least in part, of a series of ductwork through which air can pass. 
     Headspace air supply line  112  may comprise other components through which headspace air  108  passes en route to mixer  114 . In the example illustrated, headspace air  108  passes through humidifier  116  along headspace air supply line  112 . Other components in other arrangements are also contemplated. 
     Headspace air supply line  112  has headspace air receiving end  118 . Headspace air receiving end  118  is generally configured to engage grain bin  102 . That is headspace air receiving end  118  may comprise a flange or other connection member suitable for engaging grain bin  102 . Headspace air receiving end  118  comprises an open end that, when engaged with grain bin  102 , provides fluid access from headspace  106  of grain bin  102  to within headspace air supply line  112 , such that headspace air  108  can move from within headspace  106  into the open end of headspace air supply line  112  at headspace air receiving end  118  and through headspace air supply line  112  toward mixer  114 . In an aspect, headspace air receiving end  118  can be mounted to a roof of grain bin  102 . 
     As noted, various components may be included along headspace air supply line  112  through which headspace air  108  moves. As noted, one particular example arrangement, air conditioning system  100  comprises humidifier  116  along headspace air supply line  112 . Humidifier  116  is coupled to a water source and injects water into headspace air  108 . When in use, the water injected by humidifier  116  increases the RH level of headspace air  108  received from headspace  106 . This may be done, for instance, when the RH of headspace air  108  is lower than a target RH for drying or hydration. Humidifier  116  may be any type of humidifier, including those using evaporative cooling, ultrasonic pulses, vaporizers, and the like. The humidifier injects water into headspace air  108  in the form of vaporized air particles. Other methods of injecting water into headspace air  108  can include providing a wick into headspace air supply line  112 , over which headspace air  108  passes. Other types of humidifiers and methods for injecting water will be understood and are contemplated within the scope of this disclosure. While air conditioning system  100  comprises humidifier  116 , it will be understood that some arrangements do not include humidifier  116 . Humidifier  116  may be optionally included or operated based on the weather parameters in a particular location. 
     Headspace air supply line  112  also comprises headspace air valve  122 . Headspace air valve  122 , as illustrated, is within headspace air supply line  112  and generally regulates entry of headspace air  108  into mixer  114 . Headspace air valve  122  operates to at least partially or fully open and close headspace air supply line  112 , such that, when open, headspace air  108  passes through headspace air supply line  112  to mixer  114 .  112 . A degree to which headspace air valve  122  is open regulates the rate at which headspace air  108  passes through headspace air supply line  112 . Any valve suitable for opening or closing, or at least partially opening or partially closing, headspace air supply line  112  may be used. Some examples that may be suitable for use include gate valves, butterfly valves, ball valves, and so forth. 
     As shown in  FIG.  1   , headspace air valve  122  is positioned along headspace air supply line  112  between mixer  114  and humidifier  116 . However, it will be understood that the arrangement illustrated is only an example, and that other arrangements are contemplated. In general, headspace air valve  122  may be positioned at any location along headspace air supply line  112 . 
     As shown in  FIG.  1   , air conditioning system  100  further comprises ambient air supply line  124 . In general, ambient air supply line  124  facilitates moving ambient air  110  into mixer  114 . Ambient air supply line  124  can be formed, at least in part, of a series of ductwork through which ambient air  110  can pass. 
     As illustrated, ambient air supply line  124  may also comprise various components through which ambient air  110  may pass as ambient air  110  is moved into mixer  114 . In the example illustrated, ambient air supply line  124  further comprises ambient air valve  128 . Other components in other arrangements are also contemplated. 
     In general, ambient air supply line  124  may move ambient air  110  to mixer  114 . Ambient air  110  can comprise any air received from an area external to grain bin  102 . For instance, ambient air  110  may be natural air surrounding grain bin  102 ; a specific mixture of air received from an air storage container or generator, such as air comprising any one or more of nitrogen, oxygen, carbon dioxide, argon, water vapor, and the like; or another like source. 
     Ambient air supply line  124  is illustrated as comprising ambient air valve  128 , which generally regulates entry of ambient air  110  into mixer  114 . Ambient air valve  128  operates to at least partially or fully open and close ambient air supply line  124 , such that, when open, ambient air  110  passes through ambient air supply line  124  to mixer  114 . A degree to which ambient air valve  128  is open regulates the rate at which ambient air  110  passes through ambient air supply line  124 . Any valve suitable for opening or closing, or at least partially opening or partially closing, ambient air supply line  124  may be used. Some examples that may be suitable for use include gate valves, butterfly valves, ball valves, and so forth. While the ambient air valve  128  is illustrated at a particular location along ambient air supply line  124 , other arrangements are contemplated. 
     As noted, headspace air supply line  112  facilitates delivering headspace air  108  to mixer  114  and ambient air supply line  124  facilitates delivering ambient air  110  to mixer  114 . Generally, mixer  114  provides a mixing area where headspace air  108  is mixed with ambient air  110 . While illustrated as an individual component, mixer  114  is intended to be any location or mechanism by which headspace air  108  and ambient air  110  are mixed. Mixer  114  may be a standalone component, may be integrated with any other component, or may be a location where headspace air supply line  112  and ambient air supply line  124  join. At mixer  114 , headspace air  108  is mixed with ambient air  110  to form air mixture  130 . 
     Air mixture  130 , comprising a mixture of headspace air  108  and ambient air  110 , may be provided back to grain bin  102  through air mixture supply line  132 . In general, air mixture supply line  132  comprises ductwork for facilitating moving air mixture  130  from mixer  114  to grain bin  102 . Air mixture supply line  132  may comprise other components through which air mixture  130  passes when moving from mixer  114  to grain bin  102 . In the example illustrated, air conditioning system  100  comprises fan  134  and heater  136  along air mixture supply line  132 . Other components in other arrangements are also contemplated. 
     Fan  134 , as illustrated, is generally configured to receive air mixture  130  from mixer  114  and move air mixture  130  through air mixture supply line  132  toward grain bin  102 . In another arrangement, fan  134  is configured to receive headspace air  108  from headspace air supply line  112  and ambient air  110  from ambient air supply line  124 , facilitate mixing of headspace air  108  and ambient air  110 , and move air mixture  130  through air mixture supply line  132 . In general, fan  134  may comprises a fan system for moving air mixture  130 . For instance, axial, centrifugal, mixed flow, including bladed and bladeless fans, and the like fan systems can be used. In some embodiments, fan  134  receives air mixture  130  from mixer  114  and pushes it through air mixture supply line  132  toward grain bin  102 . In a specific embodiment, fan  134  receives only air mixture  130  having been mixed at mixer  114 . 
     Air conditioning system  100  is further illustrated as comprising heater  136 . Heater  136  is illustrated and described as a discrete component. However, as with other components described in relation to air conditioning system  100 , heater  136  may be combined with other components. As an example, fan  134  and heater  136  could also be illustrated and described as a single component. Moreover, while heater  136  is illustrated along air mixture supply line  132 , disposed between fan  134  and grain bin  102 , this is just one example, and other arrangements of heater  136  and fan  134 , whether provided as a single component or separate components, may be used in implementations of the disclosed technology. 
     In general, heater  136  heats air mixture  130  as it is passed through air mixture supply line  132 . By heating air mixture  130 , an RH level of air mixture  130  can be decreased or otherwise controlled to adjust the RH level to a target RH level. Heater  136  may use any type of heating element or mechanism suitable for increasing a temperature, and thereby reducing the RH level, of air mixture  130 . For instance, heaters using electric heating coils, or other resistance heating methods; gas, such as methane, propane, butane, mixtures thereof, and so forth; or other like heating methods, may be used by heater  136  to heat air mixture  130 . Air mixture  130  can be passed through a portion of air mixture supply line  132  corresponding to heater  136 , such that air mixture  130  is heated from a first temperature to a second temperature, where the second temperature corresponds to air mixture  130  having an RH level about equal to or equal to the target RH level for air mixture  130 . The target RH level may be calculated based on the equilibrium moisture content (EMC) characteristics of the particular agricultural product in grain bin  102 . 
     Air mixture supply line  132 , as illustrated, opens into grain bin plenum  138 . Grain bin plenum  138  generally comprises a location at which air mixture  130  is received from air mixture supply line  132  into grain bin  102  and is dispersed through the agricultural product  104  by passing through a perforated opening of grain bin plenum  138 , such that air mixture  130  conditions agricultural product  104  in a desired manner. 
     In the example illustrated, air mixture  130  is provided within grain bin plenum  138  at a location corresponding to base  140  of grain bin  102 . Base  140  may correspond to a lowermost portion of grain bin  102 . In example system illustrated, grain bin plenum  138  is provided within grain bin  102  at a location corresponding to base  140 . This example arrangement provides benefits in that air mixture  130  is blown into grain bin plenum  138  and is forced upward into agricultural product  104 , thereby permeating agricultural product  104 , and out of one or more grin vents, such as grain bin vent  146  located on grain bin roof  144 , which may correspond to an uppermost portion of grain bin  102  opposite that of grain bin base  140 . In doing so, the moisture content of agricultural product  104  can be increased or decreased based on the RH level of air mixture  130 . In this way, the technology described herein allows for greater control in adjusting the moisture content of agricultural product  104 , compared to existing methods, since there is greater control over the RH level of air mixture  130 . This, in turn, provides for better moisture content control of agricultural product  104 , thereby reducing over drying or over wetting during conditioning. 
     In some cases, to determine or control the RH levels of headspace air  108 , ambient air  110 , or air mixture  130 , one or more sensors may be provided as part of air conditioning system  100 . In the example illustrated, air conditioning system  100  comprises first sensor  146 , second sensor  148 , and third sensor  150 . In a specific implementation, sensors, such as first sensor  146 , second sensor  148  and third sensor  150  measure RH. It will be understood that sensors may also be used to measure other variables, such as temperature, airflow rate, air pressure, and so forth. Sensors suitable for use are generally known in the field. Some suitable examples include those utilized by the Automated Grain Bin Monitoring and Conditioning System (BinManager®) offered by AGI SureTrack®. 
     First sensor  146 , as used in the example air conditioning system  100 , is disposed within headspace air supply line  112 , such that first sensor  146  measures at least a first RH level of headspace air  108 , or any other variable associated with headspace air  108 . While shown within headspace air supply line  112 , first sensor  146  could be positioned within headspace  106  of grain bin  102  to measure the first RH level of headspace air  108 . 
     Second sensor  148 , as used in the example air conditioning system  100 , is positioned at a location outside of grain bin  102 , such that second sensor  148  measures at least a second RH level of ambient air  110 , or any other variable associated with ambient air  110 . Second sensor  148  may be positioned on or within ambient air supply line  124 , as illustrated, or at any other location outside of grain bin  102 . In another example embodiment, second RH level of ambient air  110  is received from another source, such as a third-party weather source through network communications, as will be further discussed. This may be performed in addition to or in lieu of using second sensor  148 . 
     Third sensor  150 , as used in the example air conditioning system  100 , is positioned within air mixture supply line  132 , such that third sensor  150  measures at least a third RH level of air mixture  130 , or any other variable associated with air mixture  130 . 
     As with other components, sensors may be stand-alone sensors, or may be integrated with other components. For instance, any of the sensors may be integrated with humidifier  116 , mixer  114 , fan  134 , heater  136 , or any other component. While shown within air mixture supply line  132 , disposed between heater  136  and grain bin  102 , third sensor  150  could be positioned at any location along air mixture supply line  132 . In a particular embodiment, third sensor  150  is positioned within grain bin plenum  138 . For instance, one location suitable for third sensor  150  includes a location within grain bin plenum  138  corresponding to an opening of air mixture supply line  132 , such that third sensor  150  measures RH, or other variables, of air mixture  130  as it exits air mixture supply line  132  and enters grain bin plenum  138 . 
     Among other example components, air conditioning system  100  comprises sensor cable  152 . Sensor cable  152  comprises one or more sensors suspended through agricultural product  104 . Such sensors may measure, temperature, RH, carbon dioxide, and the like. That is, each sensor of sensor cable  152  measures a variable at a different vertical location within agricultural product  104 , as it is stored within grain bin  102 . Sensor cables measuring temperature and RH levels, which can be used to determine a moisture content of an agricultural product, are known in the art. One suitable example is also provided by BinManager® offered by AGI SureTrack®. This system can be used to determine a moisture content at different vertical positions within agricultural product  104  using the temperature and RH sensors provided by the BinManager® temperature and RH sensor cables. 
     It is again noted that air conditioning system  100  is one example suitable of the technology, and one that is suitable for use in implementing methods of conditioning stored agricultural products that will be further described. Other arrangements and systems are contemplated, and the example illustrated in  FIG.  1    is not intended to limit the technology to a particular arrangement. In other embodiments, more or fewer components may be used. Components shown and illustrated in  FIG.  1   , along with other components that may be present in other embodiments, can be standalone components performing the individual functions described herein, or may be integrated within one or more of the illustrated or additional components to perform the described tasks. 
     As discussed, air conditioning system  100  may be used to condition an agricultural product for storage or sale. For example, air conditioning system  100  may condition air to have particular target temperatures or RH levels, and then moves the conditioned air across a stored agricultural product, such as stored agricultural product  104 , in an effort to bring the agricultural product to a particular moisture content, or have another desired property. 
     To do so, agricultural product  104  can be provided to and housed within grain bin  102 , as illustrated. As noted, there are generally different target moisture contents desired depending on an agricultural product type. Some moisture contents are better for long-term storage, while others are targeted prior to sale. Thus, the target moisture content may be determined based on the agricultural product type and the current stage of the agricultural product within the overall supply chain. 
     Table 1 provides some example agricultural product types, along with target moisture content for each type. Table 1 includes examples for a short-term (about 6 months) storage. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Agricultural  
                 Target Moisture 
               
               
                   
                 Product 
                 Content (Storage) 
               
               
                   
                   
               
             
            
               
                   
                 Wheat 
                 14.0% 
               
               
                   
                 Corn 
                 15.0% 
               
               
                   
                 Soybean 
                 13.0% 
               
               
                   
                 Popcorn 
                 13.5% 
               
               
                   
                 Rice 
                 13.0% 
               
               
                   
                 Barley 
                 14.0% 
               
               
                   
                 Oats 
                 14.0% 
               
               
                   
                 Sorghum 
                 15.0% 
               
               
                   
                 Sunflower 
                   10% 
               
               
                   
                 Edible beans 
                   16% 
               
               
                   
                   
               
            
           
         
       
     
     To bring agricultural product  104  to a target moisture content, a current moisture content can be determined for various vertical levels of agricultural product  104  using sensor cable  152 . In general, when relatively dryer air is blown into grain bin plenum  138 , lower levels of agricultural product  104 , such as a portion of agricultural product  104  within lower one-half region  154  of grain bin  102 , tend to dry faster than a portion of agricultural product  104  within the upper one-half region  156  of grain bin  102 . 
     To better control the condition of agricultural product  104  during conditioning (such as drying or wetting), a target RH level, which can be based on the target moisture content or the current moisture content of agricultural product  104 , for air mixture  130  can be achieved, and air mixture  130  is blown into and permeated through agricultural product  104 . 
     As an example, some target RH levels for air mixture  130  that may be used based on the target moisture content of agricultural product  104  comprise a target mixed air RH level in a range from about 60% to about 70%. In a specific case, the target mixed RH level is equal to or between 60% and 70% RH. Target agricultural product temperature may comprise a range from about 40.0° F. (4.4° C.) to about 60.0° F. (16.6° C.). In a specific case, the target agricultural product temperature may comprise a range from equal to or between 40.0° F. (4.4° C.) and 60.0° F. (16.6° C.). It will be understood that hybrids of some the various agricultural types may have different optimal moisture contents for storage, and therefore, these values are intended to be a representative example. 
     In operation, the target RH level for air mixture  130  may be determined using an equation for equilibrium moisture content (EMC) characteristics. To achieve the determined target RH level, headspace air  108  from headspace  106  may be drawn into headspace air supply line  112 . As noted, headspace air  108  will typically have an RH level greater than the RH level of ambient air  110  as moisture is released into headspace air  108  from agricultural product  104 . Headspace air  108  is moved through headspace air supply line  112  to mixer  114 . Specific values for ranges provided in target air mixture ranges, including target relative humidity, can be calculated using the following: 
     
       
         
           
             ERH 
             = 
             
               exp 
               [ 
               
                 
                   - 
                   
                     A 
                     
                       T 
                       + 
                       C 
                     
                   
                 
                 ⁢ 
                 
                   exp 
                   ⁡ 
                   ( 
                   
                     
                       - 
                       B 
                     
                     × 
                     
                       MC 
                       D 
                     
                   
                   ) 
                 
               
               ] 
             
           
         
       
       
         
           
             
               MC 
               D 
             
             = 
             
               
                 1 
                 B 
               
               × 
               
                 ln 
                 [ 
                 
                   - 
                   
                     A 
                     
                       
                         ( 
                         
                           T 
                           + 
                           C 
                         
                         ) 
                       
                       × 
                       
                         ln 
                         ⁡ 
                         ( 
                         ERH 
                         ) 
                       
                     
                   
                 
                 ] 
               
             
           
         
       
       
         
           
             RH 
             ⁢ 
                 
             is 
             ⁢ 
                 
             relative 
             ⁢ 
                 
             humidty 
           
         
       
       
         
           
             T 
             ⁢ 
                 
             is 
             ⁢ 
                 
             temperature 
           
         
       
       
         
           
             
               MC 
               D 
             
             ⁢ 
                 
             is 
             ⁢ 
                 
             dry 
             ‐ 
             basis 
             ⁢ 
                 
             moisture 
             ⁢ 
                 
             content 
           
         
       
       
         
           
             A 
             , 
             B 
             , 
             
               C 
               ⁢ 
                   
               are 
               ⁢ 
                   
               constants 
             
           
         
       
     
     A, B, C are isotherm equation constants for agricultural products, which are based on the specific agricultural product. Such values will be known and accessible to those of ordinary skill in the art. As an example, some can be found in “Moisture Relationships of Plant-based Agricultural Products,” ASAE D245.5, October 1995, which is incorporated by reference herein in its entirety. 
     If RH levels for headspace air  108  are lower than the target RH level, then the RH level of headspace air  108  can be increased to any level using humidifier  116 . In the example illustrated, humidifier  116  is located along headspace air supply line  112 . While other arrangements are possible, this arrangement has benefits because humidifier  116  can be more efficient when increasing RH levels of headspace air  108 , since there is already a relatively greater amount of water vapor in headspace air  108 , and since RH levels of headspace air  108  are generally greater than that of ambient air  110 . This can conserve water resources and increase the working life of humidifier  116 . 
     Further, ambient air  110  can be drawn into ambient air supply line  124 . Ambient air  110  is moved through ambient air supply line  124  and into mixer  114 , where it is mixed with headspace air  108  to form air mixture  130 . Air mixture  130  can be formed such that air mixture  130  comprises the target RH level. 
     Headspace air  108  and ambient air  110  can be mixed at a specific ratio to form air mixture  130  comprising the target RH level. The amount of headspace air  108  is adjusted by adjusting the headspace airflow rate by modifying the degree to which headspace air valve  122  is open. Likewise, the amount of ambient air  110  is modified by adjusting an ambient airflow rate by modifying the degree to which ambient air valve  128  is open. The flow rates can be adjusted to achieve a ratio of headspace air  108  to ambient air  110 , such that, when mixed, air mixture  130  comprises the target flow rate. 
     One method of determining the ratio comprises measuring, using first sensor  146 , a first RH level of headspace air  108 , and measuring, using second sensor  148 , a second RH level of ambient air  110 . The current RH level of air mixture  130 , as measured by third sensor  150 , is adjusted to achieve the target RH level. For instance, if the current RH level is less than the target RH level, the headspace airflow rate is increased relative to the ambient airflow rate until the target RH level of air mixture  130  is achieved. Conversely, if the current RH level is greater than the target RH level, the headspace airflow rate is decreased relative to the ambient airflow rate until the target RH level of air mixture  130  is achieved. 
     If the RH of ambient air  110  is greater than the target RH, heater  136  is operated to bring the RH of ambient air  110  down to the target RH. If the RH of headspace air  108  is lower than the target RH, then humidifier  116  can be operated to include the RH of headspace air  108  to the target RH. 
     Target RH may be determined by taking into account the heat of compression (fan warm) at the plenum. For example, as a rule of thumb 1 in. (inch) of water (249.09 Pascal) static pressure developed in the plenum develop 1° F. temperature rise. The target RH can be determined using a psychrometric equation. In the beginning, plenum RH is calculated based on predicted temperature value and is observed whether it is achieved or not within 30 min of fan running and re-adjust the calculation based on measured temperature rise. For conversion purposes, 1 in. of water column pressure=249.09 Pascal pressure. Moreover, C=5/9×(F−32). However, more specific measurements can be determined using PV=nRT, where P is the pressure at the grain plenum, V is the volume plenum, n=number of mol of gas in the plenum, R is the gas constant equal to 8.31 J/K·mol, and T is the temperature of the gas in the plenum. 
     If the target RH level is greater than the first RH level of headspace air  108  and the second RH level of ambient air  110 , then air conditioning system  100  may only receive headspace air  108  from headspace  106 . Humidifier  116  can be used to increase the first RH level to the target level by injecting water into headspace air  108  as it flows through headspace air supply line  112 . The target RH level can be achieved by measuring, using third sensor  150 , the current RH level of air mixture  130 , and increasing the amount of water injected into headspace air  108  until the current RH level increases to equal the target RH level. 
     If the target RH level is lower than headspace air  108  and ambient air  110 , then air conditioning system  100  may only receive ambient air  110 . Heater  136  can be used to decrease the current RH level of air mixture  130 . Heater  136  can be used to increase the temperature of air mixture  130  until the current RH level, as measured by third sensor  150 , decreases to equal the target RH level. It may also take into account the heat of compression. 
     As noted, the target RH level of air mixture  130  can be determined by a target moisture content of agricultural product  104  and a current moisture content of agricultural product  104 . Thus, the target RH level is based on the target moisture content or the current moisture content of agricultural product  104 . Further, this target RH level may be based on a specific portion of the agricultural product, such as a portion of the agricultural product within lower one-half region  154  of grain bin  102 . 
     While the target RH level may be based on the moisture content of agricultural product  104 , one particular example suitable for some uses of the technology comprises a target RH level, of air mixture  130 , in a range from about 55% to about 65% RH. In a specific case, the target RH level, of air mixture  130 , is in a range from 55% to 65%. In another specific case, the target RH level of air mixture  130  is about 65% or is 65% 
     Once air mixture  130  comprises the target RH level, air mixture  130  can be provided to grain bin  102 . For instance, air mixture  130  can be provided to grain bin plenum  138  using fan  134 . The location where air mixture  130  is provided within grain bin  102  may be within lower one-half region  154  of grain bin  102 . 
     With reference now to  FIG.  2   ,  FIG.  2    provides example process  200  of regulating moisture content in an agricultural product stored in a grain bin. Air conditioning system  100  of  FIG.  1    is one suitable system for performing process  200 . 
     Process  200  begins at start  202  and proceeds to step  204 . At step  204 , a determination is made whether each of the vertical layers of the agricultural product within the grain bin have a moisture content that is equal to the target moisture content, within a predetermined threshold, for the agricultural product. As an example, the system may determine using a cable sensor, such as cable sensor  152 , whether the agricultural product has a moisture content equal to within ±0.5% moisture of the target moisture content. If the target moisture content for each of the vertical layers is within the threshold moisture, then process  200  proceeds to step  206 , “Fan Off”. This shows that drying/hydration is completed. Here, at step  206 , the air conditioning system, such as air conditioning system  100 , does not blow an air mixture into the grain bin. However, if the target moisture content for each of the vertical layers is not within the threshold moisture, then process  200  proceeds to step  208 . This shows that drying/hydration is not completed. 
     At step  208 , it is determined whether a bottom layer of agricultural product has achieved the target moisture content within a predetermined threshold. For instance, it may be determined whether the moisture content is equal to within ±0.5% moisture of the target moisture content. The bottom layer may comprise a vertical layer of agricultural product corresponding to a lowermost sensor on the sensor cable. In some cases, the bottom layer comprises a portion of the agricultural product within a lower one-half region of the grain bin. In an example, a bottle layer comprises a layer of agricultural product corresponding to a location of a lowermost sensor measuring vertical conditions of the agricultural product. If the bottom layer comprises a moisture content within the threshold of the target moisture content, then process  200  proceeds to step  210 . 
     At step  210 , a determination is made whether EMC of air in the grain bin plenum is less or greater than a maximum moisture content of the agricultural product in the layers. As noted, the EMC can be determined based on the heat of compression temperature prediction. If YES, process  200  proceeds to step  212  where the fan is turned on to blow ambient air into the grain bin plenum to permeate through the agricultural product. If NO, process  200  proceeds to step  214  wherein the heater of the air conditioning system is engaged to achieve target air EMC less than the maximum moisture content of the agricultural product in the layers. Process  200  then proceeds to step  212  where the air conditioning system fan is turned on to blow ambient air into the grain bin plenum to permeate through the agricultural product. 
     With reference back to step  208 , if the bottom layer comprises a moisture content less than the threshold of the target moisture content, then process  200  proceeds to step  216 . At step  216 , a determination is made whether the EMC of air minus 2% in the grain bin plenumis less than a target moisture content of the agricultural product. If not, then process  200  proceeds to step  212  where the air conditioning system fan is turned on to blow ambient air into the grain bin plenum to permeate through the agricultural product. However, if the EMC of air minus 2% in the grain bin plenum is less than the target moisture content, then the air conditioning system mixes the headspace air with the ambient air to achieve the target RH level at step  218 . If the RH of the headspace air is lower than the target RH level, then the RH level of the air mixture is increased using the humidifier at step  220  The process then proceeds to step  212  where the fan is turned on, which blows the air mixture into the grain bin plenum where it permeates through the agricultural product. 
     In many cases, an air conditioning system, such as air conditioning system  100  of  FIG.  1   , performs operations under the direction of computer-executable instructions. That is, one or more of the components of air conditioning systems describe herein may be operated under the guidance of a controller. For instance, air conditioning systems, such as air conditioning system  100 , may autonomously or semi-autonomously operate to condition air for an agricultural product based on computer instructions being executed by a computing device, such as the controller. 
       FIG.  3    provides an example operating environment for an example controller  302  suitable for use with air conditioning systems described herein, such as air conditioning system  100  of  FIG.  1   . Thus, some components described with respect to  FIG.  3    may correspond to, and are illustrative examples of, those components described in conjunction with air conditioning system  100  of  FIG.  1   . 
     In general, controller  302  is a computing device configured to operationally control one or more components of an air conditioning system. With brief reference to  FIG.  4   ,  FIG.  4    illustrates an example computing device suitable for use as controller  302 . 
     Computing device  400  of  FIG.  4    is one example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the technology. Neither should computing device  400  be interpreted as having any dependency or requirement relating to any one or combination of components illustrated. 
     Aspects of the present disclosure may be described in the general context of computer code or machine-useable instructions, including computer-executable instructions such as program modules, being executed by a computer or other machine, such as a personal data assistant or other handheld device. Generally, program modules including routines, programs, objects, components, data structures, etc. refer to code that perform particular tasks or implement particular abstract data types. The technology may be practiced in a variety of system configurations, including hand-held devices, consumer electronics, general-purpose computers, more specialty computing devices, etc. The technology may also be practiced in distributed computing environments where tasks are performed by remote-processing devices that are linked through a communications network. 
     With continued reference to  FIG.  4   , computing device  400  includes bus  402  that directly or indirectly couples the following devices: memory  404 , one or more processors  406 , one or more presentation components  408 , input/output ports  410 , input/output components  412 , and power supply  414 . 
     Bus  402  represents what may be one or more busses (such as an address bus, data bus, or combination thereof). Although the various blocks of  FIG.  4    are shown with lines for the sake of clarity, in reality, delineating various components is not so clear, and metaphorically, the lines would more accurately be grey and fuzzy. For example, one may consider a presentation component, such as a display device, to be an I/O component. As another example, processors may also have memory. Such is the nature of the art, and it is again reiterated that the diagram of  FIG.  4    merely illustrates an example computing device that can be used in connection with one or more embodiments of air conditioning systems. Distinction is not made between such categories as “workstation,” “server,” “laptop,” “hand-held device,” etc., as all are contemplated within the scope of  FIG.  4    and reference to “computing device.” 
     Computing device  400  typically includes a variety of computer-readable media. Computer-readable media can be any available media that can be accessed by computing device  400  and includes both volatile and nonvolatile media, and removable and non-removable media. By way of example, and not limitation, computer-readable media may comprise computer storage media and communication media. 
     Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computing device  400 . Computer storage media excludes signals per se. 
     Communication media typically embodies computer-readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, and other wireless media. Combinations of any of the above should also be included within the scope of computer-readable media. 
     Memory  404  includes computer storage media in the form of volatile or nonvolatile memory. The memory may be removable, non-removable, or a combination thereof. Example hardware devices include solid-state memory, hard drives, optical-disc drives, etc. Computing device  400  includes one or more processors  406  that read data from various entities such as memory  404  or I/O components  412 . Presentation component(s)  408  present data indications to a user or other device. Examples of presentation components include a display device, speaker, printing component, vibrating component, etc. 
     I/O ports  410  allow computing device  400  to be logically coupled to other devices including I/O components  412 , some of which may be built in. Illustrative components include a microphone, joystick, game pad, satellite dish, scanner, printer, wireless device, and so forth. 
     Power supply  414  illustrates any power supply terminal or power source sufficient for providing power to one or more components of computing device  400 . 
     Having described an example system suitable for use as controller  302 , reference is again made back to operating environment  300 . As illustrated, controller  302  is coupled to various components. While some components are illustrated as directly coupled to controller  302  and other are illustrated as coupled via network  304 , it will be understood that this arrangement is just one example. Other arrangements are contemplated, and it should generally be understood that controller  302  may be communicatively coupled to any component indirectly via a network, such as network  304  or through a hardwire communication bus. Further, as noted, embodiments of the technology may comprise additional or fewer components. Some components may be combined with other components, and may be in any local or distributed arrangement. 
     As illustrated, controller  302  communicates via network  304  to a network of third-party servers  306 . Such third-party servers  306  represent any server to which controller  302  communicates or from which controller  302  receives information. The Internet provides an example of connected servers that can exchange information with controller  302 . 
     In one particular example, a third-party weather server, such as one accessed via the Internet, provides RH levels of ambient air that may be used by component of an air conditioning system to mix the ambient air with headspace air to achieve an air mixture having a target RH level. In another example, a third-party server represents a remote weather monitoring station. 
     Controller  302  is also illustrated as communicatively coupled to client computing device  308  via network  304 . In general, client computing device  308  may be any computing device from which controller  302  receives information or communicates information regarding the air conditioning system. Computing device  400  of  FIG.  4    is an example computing device that is suitable for use as client computing device  308 . As an example, client computing device  308  may provide controller  302  with information related to the agricultural product within a grain bin. For instance, client computing device  308  may provide an indication of a type of agricultural product within a grain bin, a harvest date, a harvest location, a distribution date, a target moisture content, a target RH level, and the like. 
     In some embodiments, a client computing device may provide a schedule of activities associated with the agricultural product, such as when the agricultural product is placed within the grain bin and when the agricultural product will be distributed. From such information, controller  302  may determine the moisture contents, using the charts above as an example, and automatically adjusting target RH levels of air mixtures to achieve the target moisture content for the scheduled activities. 
     Network  304  may include one or more networks (e.g., public network or virtual private network “VPN”) as shown with network  304 . Network  304  may include, without limitation, one or more local area networks (LANs) wide area networks (WANs), or any other wired or wireless communication network or method. 
     Controller  302  is further illustrated coupled to datastore  310 . Datastore  310  generally stores information including data, computer instructions (e.g., software program instructions, routines, or services), or models used in embodiments of the described technologies, or other information or instructions usable by controller  302  or other components of air conditioning system, such as those in operating environment  300 . Although depicted as a single database component, datastore  310  may be embodied as one or more data stores or may be in the cloud. 
     Operating environment  300  comprises other components communicatively coupled to controller  302 , including first sensor  312 , second sensor  314 , third sensor  316 , headspace air valve  322 , ambient air valve  324 , humidifier  326 , heater  328 , sensor cable  330 , and fan  332 . 
     In general, controller  302  receives RH level information from sensors including first sensor  312 , second sensor  314 , and third sensor  316 . First sensor  312  may be positioned within an air conditioning system or grain bin to measure a first RH level, among other variables, associated with headspace air. Second sensor  314  may be positioned such that it measures a second RH level, among other variables, associated with ambient air located outside of the grain bin. Third sensor  316  may be positioned within an air conditioning system or grain bin to measure a third RH level, among other variables, associated with an air mixture comprising the headspace air and ambient air. Each respective sensor may communicate values of measured variables, such as RH levels, to controller  302 . 
     Headspace air valve  322  and ambient air valve  324  are generally coupled to controller  302  such that controller  302  operationally controls headspace air valve  322  and ambient air valve  324 . Headspace air valve  322  and ambient air valve  324  may be controlled by controller  302  using one or more drivers stored in datastore  310 . As an example, controller  302  may provide a signals causing actuation of actuators that respectively position the valves of headspace air valve  322  and ambient air valve  324 . Such actuation can be binary, in the sense the controller  302  sends a data signal causing headspace air valve  322  and ambient air valve  324  to actuate between a closed position and an open position. The closed position of headspace air valve  322  may prevent headspace airflow through a headspace air supply line, whereas the open position of headspace air valve  322  may permit headspace airflow through the headspace air supply line. The closed position of ambient air valve  324  may prevent ambient airflow through an ambient air supply line, whereas the open position of ambient air valve  322  may permit ambient airflow through the ambient air supply line. 
     In another embodiment, headspace air valve  322  and ambient air valve  324  may be adjusted to a partially open position that respectively reduces headspace airflow and ambient airflow based on the partially open position. In an example embodiment, controller  302  further controls the headspace airflow rate and the ambient airflow rate respectively adjusting a degree of openness for headspace air valve  322  and ambient air valve  324 . In one particular example, controller  302  turns on headspace air valve  322  and ambient air valve  324 , and controls the headspace airflow rate and the ambient airflow rate using the degree of openness of headspace air valve  322  and ambient air valve  324 . Controller  302  may independently control the operation of each headspace air valve  322  and ambient air valve  324 , thereby controller a relative proportion of the amount of headspace air and ambient air, respectively, that is passed through the system. 
     Any combination of control of headspace air valve  322 , and ambient air valve  324  by controller  302  to modify the headspace airflow rate and the ambient airflow rate to achieve any ratio is contemplated and is intended to be within the scope of the present disclosure. 
     Operating environment  300  further comprises humidifier  326 . Humidifier  326  is coupled to controller  302  such that controller  302  operationally controls an amount of water humidifier  326  injects into the air, such as headspace air along the headspace air supply line, for example. Controller  302  may control humidifier  326  using one or more drivers stored on datastore  310 . 
     In an example, controller  302  modifies the amount of water injected into the air by humidifier  326  based on RH level information received from the RH sensors, such as first RH sensor  312 , second RH sensor  314 , and third RH sensor  316 . In a specific implementation, controller  302  receives a first RH level associated with headspace air from first RH sensor  312 . Controller  302  accesses a target RH level. Controller  302  compares the first RH level with the target RH level and determines the target RH level is greater than the first RH level of the headspace air. Based on this determination, controller  302  modifies the amount of water injected into received headspace air until the headspace air is about equal to or equal to the target RH level. 
     Operating environment  300  further comprises heater  328 . Heater  328  is coupled to controller  302  such that controller  302  operationally controls heater  328  by adjusting a heat level at which heater  328  heats air within the air conditioning system, such as a heat level at which heater  328  heats an air mixture, for example. Controller  302  may control heater  328  using one or more drivers stored in datastore  310 . 
     By way of an example, controller  302  may modify a heat level of heater  328  based on information received from sensors, such as levels received from first sensor  312 , second sensor  314 , and third sensor  316 . For instance, controller  302  receives a second RH level associated with ambient air from second RH sensor  314 . In another case, controller  302  receives the second RH level from a third-party server, such as a weather server associated with third-party servers  306 , via network  304 . Controller  302  accesses a target RH level. Controller  302  compares the second RH level with the target RH level and determines the target RH level is less than the first RH level of the ambient air. Based on the determination, controller modifies the heat level of heater  328  to increase an air temperature until the RH level of the air, such as an air mixture comprising the ambient air, decreases and is about equal to or equal to the target RH level. 
     Operating environment  300  further comprises sensor cable  330 . Sensor cable  330  is communicatively coupled to controller  302  such that controller  302  receives data from sensor cable  330  associated with variables measured by sensor cable  330 , such as temperature and RH levels. For instance, controller  302  may receive a RH level from sensor cable  330 , which can be used to determine a moisture content for an agricultural product. Controller  302  may adjust any of the components of operating environment  300  based on the data received from sensor cable  330 . 
     Operating environment  300  further comprises fan  332 . Fan  332  is coupled to controller  302  such that controller  302  operationally controls fan  332 . Controller  302  may control fan  332  using one or more drivers stored on datastore  310 . In some cases, controller  302  has binary control over fan  332 , meaning the controller  302  can modify an on off state of fan  332 , where fan  332  facilitates air movement through the air conditioning system when in the on state, and does not facilitate air movement through the air conditioning system in the off state. In other embodiments, controller  302  modifies a fan speed associated with fan  332  to adjust the volume of air moved through the air conditioning system by fan  332 . As an example, when operationally mixing headspace air and ambient air, or otherwise operationally using humidifier  326  or heater  328 , or other components of operating environment  300 , controller  302  may turn on fan  332 , or modify a fan speed of fan  332 , to facilitate air movement, such as an air mixture, through the air conditioning system and into a grain bin. 
     With reference to  FIG.  5   , a block diagram is provided to illustrate a method for conditioning air using an air conditioning system. The method may be performed using an air conditioning system, such as air conditioning system  100  of  FIG.  1    under the guidance of a controller, such as controller  302  of  FIG.  3   , having operational control of one or more components of operating environment  300 . In embodiments, one or more computer storage media having computer-executable instructions embodied thereon that, when executed, by one or more processors, cause the one or more processors to perform the methods of regulating moisture content of an agricultural product within a grain bin. The methods may further be embodied or performed by a system comprising at least one processor executing the instructions embodied on the computer storage media. 
     At block  502 , a first RH level is received from a first sensor. The first RH level is associated with headspace air from a headspace of a grain bin. The first RH level may be measured by the first sensor and communicated from the first sensor to a controller, where the controller receives the data from the first sensor indicating the first RH level. 
     At block  504 , a second RH level is received from a second sensor. The second RH level is associated with ambient air. In some cases, the second RH level is received from a third-party weather server via a network or from a remote weather monitoring station. The second RH level may be measured by the second sensor and communicated from the second sensor to the controller, where the controller receives the data from the second sensor indicating the second RH level. 
     At block  506 , a headspace air valve is adjusted. The headspace air valve may facilitate moving headspace air from within the headspace of the grain bin, along a headspace air supply line, and to a mixer of the air conditioning system. Adjustment of the headspace air valve causes a modification of a headspace airflow rate of the headspace air through the headspace air supply line. The controller may adjust the headspace air valve. In some cases, a degree to which the headspace air value is open (a percentage of an opening modified by headspace air value) is adjusted to modify the headspace airflow rate. 
     The headspace air valve may be modified based on receiving RH levels from first sensor, the second sensor, or the third sensor, and based on a target RH level of an air mixture comprising the headspace air. 
     The target RH level can be determined by the controller based on accessing stored data, such as a type of agricultural product within the grain bin; an activity associated with the agricultural product, such as storage or distribution; a moisture content of the agricultural product in the grain bin, as determined, for example, by a cable sensor measuring variables such as temperature and RH levels; or any combination thereof. In a specific example, the moisture content of the agricultural product located in a lower one-half region of the grain bin is determined based on temperature or RH measurements from the sensor cable, and the headspace air valve is adjusted based on the moisture content of the agricultural product located in a lower one-half region of the grain bin. 
     At block  508 , an ambient air valve is adjusted. The ambient air valve may facilitate moving ambient air along an ambient air supply line to a mixer of the air conditioning system. Adjustment of the ambient air valve causes a modification of an ambient airflow rate of the ambient air through the ambient air supply line. The controller may adjust the ambient air valve. In some cases, a degree to which the ambient air value is open (a percentage of an opening modified by ambient air valve) is adjusted to modify the ambient airflow rate. 
     The ambient air valve may be modified based on receiving RH levels from the first sensor, the second sensor, or the third sensor, and based on a target RH level of an air mixture comprising the ambient air. 
     In a specific implementation, the controller determines that the first RH level of the headspace air is greater than the second RH level of the ambient air. Based on this, the headspace air valve and the ambient air valve are adjusted such that the air mixture comprising the headspace air and the ambient air has a RH level that is equal to or about equal to the target RH level. 
     In a specific example, the moisture content of the agricultural product located in a lower one-half region of the grain bin is determined based on temperature and RH measurements from the sensor cable, and the ambient air receiving valve is adjusted based on the moisture content of the agricultural product comprised within in a lower one-half region of the grain bin. Specifically, the agricultural product located within a vertical layer corresponding to a lowermost sensor of the sensor cable is determined. In implementations, both the headspace air valve and the ambient air valve, in combination with any other components of the air conditioning system, are adjusted based on the moisture content of the agricultural product located in a lower one-half region of the grain bin. Specifically, the air conditioning system may be operated, e.g., a determination may be made whether to hydrate or dehydrate the agricultural product based on the moisture content of the agricultural product measured by the sensors, such as the lowermost sensor of the sensor cable. In operation, air conditioning system can be operational until the target moisture content is achieved. The target RH can be selected or calculated as indicated previously, and mixed air comprising this target RH may be blown into the grain bin plenum until the target moisture contents is achieved. 
     Each of the headspace airflow rate and the ambient airflow rate may be modified such that an air mixture, mixed by the mixer, comprising the headspace air and the ambient air has a RH level equal to or about equal to the target RH level. In a particular example, the target RH level is measured in RH and is from about 55% to about 65%, whereas in some cases the RH of the target RH level is from 55% to 65%. One method of determining the percentage opening of the headspace air valve and the ambient air valve to modify the values to achieve a target RH level uses the following equation: (Ambient Air RH)(1−x)+(Headspace Air RH)(x)=Target Humidity Level. “x” is the percentage opening of the headspace air valve and can be solved for using the preceding equation. The percentage opening of the ambient air valve is then 1−x. The headspace air valve and the ambient air valve can be modified accordingly to achieve the determined ratio of respective openings and generate an air mixture with the target RH level. 
     In implementations of the technology, the headspace airflow rate is controlled by a headspace air valve. The controller may adjust the headspace air valve to achieve an air mixture of the target RH level. In some cases, the ambient airflow rate is controlled by an ambient air valve. The controller may adjust the ambient air valve to achieve the air mixture of the target RH level. 
     Where the air mixture, as measured by the third sensor, comprises a RH level that is less than the target RH level, the controller may further activate a humidifier to inject additional water into the air. The humidifier may inject the water to into a headspace air supply line, an ambient air supply line, or an air mixture supply line, based on the location of the humidifier within the air conditioning system. In a specific example, the controller causes the humidifier to inject additional water into headspace air along headspace air supply line. The humidifier injects water in an amount such that the air mixture has a RH level about equal to or equal to the target RH level. 
     Where the air mixture, as measured by the third sensor, comprises a RH level that is more than the target RH level, the controller may further activate a heater to increase the temperature of air within the air conditioning system. The heater may increase the temperature of headspace air, ambient air, or an air mixture respectively flowing along the headspace air supply line, the ambient air supply line, or the air mixture supply line, based on the location of the heater within the air conditioning system. In a specific example, the controller causes the heater to increase the temperature of the air mixture along the air mixture supply line. The heater heats the air to a temperature such that the air mixture has a RH level about equal to or equal to the target RH level. 
     Examples 
     Example 1: Soybeans are placed into a grain bin of size 36 ft. (foot) (10.97 m) diameter and 25 ft. (7.62 m) eave height and filled to the eave for storage and condition. The bin is equipped with a 30 hp (horsepower) (22.4 kW) (kilo watt) speed 1750 rpm (rotations per minute) centrifugal fan, which gives around 1.07 cfm/bu (cubit feet per minute of air per bushel) or 1.177 m 3 /min·t (cubic meter per min per ton) and develop 5.5 in. (14 cm) of water static pressure (SP). As a rule of thumb, 5.5 in. of SP develop a 5.5° F. temperature rise in the plenum, which could reduce 8-10% RH, corresponding to 1.5-2% moisture based on EMC characteristics. The soybeans have an initial moisture content of 16%. For storage, the target moisture content is 13±0.5%. A fan pulling from an ambient air source is turned on, and ambient air is introduced to the soybean to begin the drying process. When soybeans within the bottom 3 ft. depth of grain mass achieved a moisture content of 13±1%, the air conditioning system is activated. When the ambient air EMC is about 12%, plenum air EMC would be about 10% based on heat of compression, also called fan warm. The air conditioning system is activated and pulls headspace air from the headspace of the grain bin to increase the plenum air from 10% to 12.5-13.5% RH. Using a sensor, the relative RH of the headspace air was determined to be 80% (16% EMC). Using another sensor, the relative RH of the ambient air was determined to be 12% and calculated plenum EMC is 10% based on heat of compression. A target RH level the air conditioning system was determined to be 13%. The heat of compression of 5.5° F. reduced the plenum air EMC to 2% lower than ambient air. To find the opening percentage for headspace air valve and ambient air valve, the following formula was used: 50% (X1)+80% (X2)=65%. By changing the X1 and X2 values by iteration, the correct values of X1=55% and X2=45% were determined. By opening headspace air valve 55% and ambient air valve 45%, 65.75% RH at the plenum was achieved. The mixed air was provided into the grain bin for drying the soybeans. For conversion purposes, 1 cfm/bu=1.1 m 3 /(min·t) 
     Example 2: Similar to Example 1, however, bottom layer moisture was 13% and ambient air EMC was 16%. In this example, headspace valve was closed and only ambient air valve was opened. The heater was operated to bring down 16% EMC to 13% EMC (85% RH to 65% RH). 
     Example 3: Similar to Example 1, however, hydration of soybean was performed, as all the layers including bottom layer were over-dried to 10% from the field. The hydration was performed to 13% moisture. In this Example, ambient air RH is 95% (18% EMC) became 85% (16% EMC) at the plenum and headspace air of 50% RH (10% EMC). Headspace valve was opened at 55% and ambient air valve opened at 45%. This resulted in a mixed air having 65% RH (13% EMC). 
     The subject matter of the present technology is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this disclosure. Rather, the inventors have contemplated that the claimed or disclosed subject matter might also be embodied in other ways, to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the terms “step” or “block” might be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly stated. 
     Embodiments described above may be combined with one or more of the specifically described alternatives. In particular, an embodiment that is claimed may contain a reference, in the alternative, to more than one other embodiment. The embodiment that is claimed may specify a further limitation of the subject matter claimed. 
     In addition, words such as “a” and “an,” unless otherwise indicated to the contrary, include the plural as well as the singular. Thus, for example, the constraint of “a feature” is satisfied where one or more features are present. Furthermore, the term “or” includes the conjunctive, the disjunctive, and both (a or b thus includes either a or b, as well as a and b). 
     For purposes of this disclosure, the word “including” or “having,” or derivatives thereof, has the same broad meaning as the word “comprising,” and the word “accessing,” or derivatives thereof, comprises “receiving,” “referencing,” or “retrieving.” Further, the word “communicating,” or derivatives thereof, has the same broad meaning as the word “receiving,” or “transmitting” facilitated by software or hardware-based buses, receivers, or transmitters using communication media. 
     From the foregoing, it will be seen that this technology is one well adapted to attain all the ends and objects described above, including other advantages which are obvious or inherent to the structure. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments of the described technology may be made without departing from the scope, it is to be understood that all matter described herein or illustrated the accompanying drawings is to be interpreted as illustrative and not in a limiting sense. 
     Some example aspects that can be practiced from the forgoing description include: 
     Aspect 1: A computerized method, computer storage media, or a controller comprising at least one processor; and computer storage media storing computer-readable instructions that, when executed by the at least one processor, cause the processor perform operations for regulating moisture content of an agricultural product within a grain bin. The method, media, or controller comprises, instructs, or performs operations comprising: receiving, from a first sensor, a first RH level of headspace air from a headspace of a grain bin; receiving, from a second sensor, a second RH level of ambient air; adjusting a headspace air valve to modify a headspace airflow rate of the headspace air; and adjusting an ambient air valve to modify an ambient airflow rate of the ambient air, wherein the headspace airflow rate and the ambient airflow rate are such that an air mixture formed from the headspace air and the ambient air comprises a target RH level. 
     Aspect 2: Aspect 1, wherein the target RH level comprises a relative RH in a range from about 55% to about 65%. 
     Aspect 3: Any of Aspects 1-2, further comprising injecting, via a humidifier, water into the headspace air based on the first RH level of the headspace air. 
     Aspect 4: Any of Aspects 1-3, further comprising accessing a target moisture content of an agricultural product stored within the grain bin, and determining the target RH level based on the target moisture content. 
     Aspect 5: Any of Aspects 1-4, further comprising receiving, from a RH sensor located within 3′ of the bottom layer grain mass an indication that an agricultural product comprises a target moisture content, wherein the headspace air receiving valve and the ambient air receiving valve openings are adjusted in response to the indication of the target moisture content of the agricultural product. 
     Aspect 6: Any of Aspects 1-5, further comprising determining that the first RH level of the headspace air is greater than the second RH level of the ambient air, wherein the headspace air receiving valve and the ambient air receiving valve openings are adjusted in response to determining the first RH level of the headspace air is greater than the second RH level of the ambient air. 
     Aspect 7: Any of Aspects 1-6, further comprising opening a headspace air valve based on first RH level of headspace air, and opening an ambient air valve based on the second RH level of the ambient air value, wherein the headspace air valve permits headspace air to enter a mixer and the ambient air valve permits ambient air to enter the mixer. 
     Aspect 8: An air conditioning system for regulating moisture content of an agricultural product in a grain bin, the system comprising: a headspace air supply line having a headspace air receiving end configured to receive headspace air from a grain bin; an ambient air supply line having an ambient air receiving end configured to receive ambient air; a mixer comprising a mixing area that receives headspace air from the headspace air supply line and the ambient air from the ambient air supply line; and a mixed air supply line that receives an air mixture from the mixer and provides the air mixture to a location within the grain bin. 
     Aspect 9: Aspect 8, further comprising a first RH sensor located within the headspace air supply line, the first RH sensor measuring a first RH level of the headspace air. 
     Aspect 10: Any of Aspects 7-9, further comprising a second RH sensor located outside of the grain bin, the second RH sensor measuring a second RH level of the ambient air. 
     Aspect 11: Any of Aspects 7-10, further comprising a third RH sensor located within the mixed air supply line, the third RH sensor measuring a third RH level of the air mixture. 
     Aspect 12: Any of Aspects 7-11, further comprising a humidifier coupled to a water source, wherein the humidifier injects water into the headspace air supply line. 
     Aspect 13: Any of Aspects 7-12, further comprising an air heater along the air mixture supply line. 
     Aspect 14: Any of Aspects 7-13, further comprising: a headspace air value along the headspace air supply line, the headspace air valve regulating entry of the headspace air into the mixer; and an ambient air valve along the ambient air supply line, the ambient air valve regulating entry of the ambient air into the mixer. 
     Aspect 15: A method of regulating moisture content in an agricultural product stored in a grain bin, the method comprising: receiving headspace air from a headspace of a grain bin comprising an agricultural product; receiving ambient air; mixing the headspace air with the ambient air to form an air mixture; and providing the air mixture to a location within the grain bin. 
     Aspect 16: Aspect 15, wherein the received headspace air has a first RH level and the received ambient air has a second RH level, the first RH level of the headspace air being greater than the second RH level of the ambient air. 
     Aspect 17: Any of Aspects 15-16, wherein the headspace air and the ambient air are mixed in a ratio, the ratio of headspace air to ambient air being determined by a target moisture content for an agricultural product within the grain bin. 
     Aspect 18: Any of Aspects 15-17, further comprising: determining a moisture content of an agricultural product in the grain bin; and providing the air mixture based on the moisture content of the agricultural product. 
     Aspect 19: Aspect 18, wherein the moisture content is determined for a portion of the agricultural product located within a lower one-half region of the grain bin. 
     Aspect 20: Any of Aspects 15-19, further comprising injecting water, using a humidifier, into the received headspace air based on a first RH level of the headspace air. 
     Aspect 21: Any of Aspects 15-20, further comprising: adjusting a headspace air valve to modify a headspace airflow rate; and adjusting an ambient air valve to modify an ambient airflow rate, wherein the headspace air valve and the ambient air valve are adjusted such that an air mixture of the headspace air and the ambient air is formed based on a moisture content of an agricultural product within the grain bin. 
     Aspect 22: Any of Aspects 15-21, wherein the air mixture has a target RH level comprising a relative RH in a range from about 55% to about 65%. 
     Aspect 23: A method of controlling RH for regulating a moisture content of an agricultural product, the method comprising: measuring, using a first RH sensor, a first RH level of headspace air received from a headspace of a grain bin; measuring, using a second RH sensor, a second RH level of ambient air; mixing the headspace air and the ambient air into an air mixture having a target RH level, wherein the headspace air and the ambient air are mixed based on the first RH level and the second RH level; and providing the air mixture to a location within the grain bin. 
     Aspect 24: Aspect 23, further comprising: adjusting a headspace airflow rate; and adjusting an ambient airflow rate, wherein the headspace airflow rate and the ambient airflow rate are adjusted such that the air mixture comprises the target RH level. 
     Aspect 25: Any of Aspects 23-24, wherein the target RH level is determined based on a target moisture content of an agricultural product within the grain bin. 
     Aspect 26: Any of Aspects 23-25, wherein the air mixture having the target RH level is provided to the location within the grain bin in response to a portion of agricultural product, located in a lower one-half region of the grain bin, reaching a target moisture content. 
     Aspect 27: Any of Aspects 23-26, further comprising injecting water, using a humidifier, into the received headspace air based on the first RH level of the headspace air.