Abstract:
A method and system for controlling the environment of storage facilities, including produce and livestock storage facilities, and the like. Movement of air within the facility is accomplished by air-handling units or fans. The speed of each fan is controlled by a variable-speed drive, allowing the fans to run at speeds below full capacity. Environmental parameters, such as temperature or humidity, are monitored to determine the existing state of the environment which is then compared to a desired state. The speed of the fans or air-handling units is adjusted to alter the existing environmental state, bringing it in alignment with the desired state. The fans or air-handling units are operated continuously, typically at reduced capacity. Other various facets are included with the system and method, including the control of the admittance of external air into the storage facility.

Description:
CROSS REFERENCE OF RELATED APPLICATIONS 
     This application is a continuation-in-part (CIP) of application Ser. No. 09/621,509, filed Jul. 21, 2000, pending. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates general to environmental control of buildings suited for human occupancy. More particularly, the present invention relates to the control of such environmental parameters as temperature, humidity, particulate levels, or even specified gas levels such as carbon dioxide (CO 2 ) at increased efficiency. 
     2. State of the Art 
     Indoor air quality and environmental control is of great concern with regard to both residential and commercial buildings. Occupants of such buildings desire to utilize these buildings in comfort and in safety. In typical heating, ventilation and air conditioning (HVAC) systems, many environmental parameters, such as temperature, humidity, and other air quality parameters, may be controlled. Typically, control of these and other environmental parameters entails, among other things, movement of air within the building, which can include introduction of fresh air from outside the building or circulation of existing air within the building. In controlling a building&#39;s environment air may be passed through furnaces, across refrigerated coils, or through humidification devices prior to introduction of the air into the occupied regions of the building. Control of an HVAC system may also include the combination of more than one of the above techniques to control multiple parameters within the building&#39;s environment simultaneously. 
     A typical method of controlling the air movement and other environmental parameters within a building is through the cyclical control of fans, or blowers, which are an integral part of an HVAC component known as an air handling unit. For example, when it is desired to cool the building, or a particular space within the building, the air handling units are turned on when the temperature rises above a predetermined upper level and then shut off when the temperature of the facility reaches a predetermined lower level. A system of this type is generally described in U.S. Pat. No. 4,682,473 to Rogers, III. This type of system utilizes the fans at full power, allowing them to cool or heat the facility at a relatively quick pace within a specified temperature range. Such systems, however, possess a number of shortcomings. For example, rapid changes in temperature, or temperature spikes, may often result in some discomfort for the occupants. Similarly, rapid changes in other environmental parameters may cause occupant discomfort. Furthermore, cyclical use of air handling units at full power or full speed may result in inefficient control of such parameters 
     Other known systems have sought to utilize multi-speed or variable-speed fans in controlling an HVAC system, Such a system is described in U.S. Pat. No. 5,492,273 to Shah, which includes a variable-speed blower motor for controlling the volumetric rate of airflow within the system. This type of system allows for a more gradual and natural change of an environmental parameter within defined parameter ranges. However, because the system is still cyclical in nature, it does not provide control of the building environment at a desirable level of efficiency. For example, in controlling temperature, the fans will remain inoperative if the temperature of the facility is within a defined temperature range. The fans will the operate at a predefine speed setting once the temperature increases into a second defined range. The blower continues to operate for a time period calculated as the expected interval of operation. If at the end of the expected interval of operation the temperature is not within the desired range, the blower will increase its speed to more quickly effect the desired temperature change. Once the desired temperature has been reached, operation of the blower is terminated until the temperature falls outside of the prescribed range once again. The fans will operate at a high-speed setting if the temperature increases into a third defined range. 
     All of the above techniques, due to their cyclical nature, include defining a range of operation, such as a temperature range. However, it is difficult to narrowly define the ranges. If the ranges are defined too narrowly, the air handling unit will repeatedly start and stop as the parameter fluctuates in and out of the prescribed range. Such incessant starting and stopping is likely to cause wear and fatigue-type damage to various components of the air handling unit, such as starters, motors and mechanical transmission components. On the other hand, if the defined ranges are set too broadly, high temperatures may cause the fans to operate at the high-speed setting for extended periods of time in an attempt to bring the temperature back to an acceptable value. Such overuse of air handling units at full speed or power results in an inefficient HVAC system. Furthermore, a broad parameter range may simply not be acceptable from a comfort standpoint. 
     As noted above, an important consideration in the environmental control of a commercial or residential building is the efficient use of power. With air handling units which are cyclically controlled, power consumption is of paramount concern to those responsible for the maintenance of the building. Occupancy of such buildings for any extended period of time requires a significant consumption of power with existing systems and methods. The cost of such power is ultimately borne by the occupant Thus, an efficient and accurate environmental control system for such buildings would be of benefit to both the owners and tenants of the buildings. 
     In view of the shortcomings in the art, it would be advantageous to provide an environmental control system for commercial and residential buildings which effectively controls specified environmental parameters while consuming a reduced amount of energy. Such a system or method should be simple to employ in existing as well as newly constructed buildings. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a method is provided for controlling the internal environment of a building intended for human occupancy, such as a commercial or residential building. The method includes the steps of providing a fan, or a plurality of fans, for circulating the internal air of the building. The fans may be operated continuously at a speed which is below their full capacity to achieve continuous parameter control at reduced power consumption. The system monitors a parameter indicative of the internal environment of the building, such as the internal temperature. Once the temperature has been monitored, the speed of the fans is altered accordingly. If the internal temperature needs to be reduced, then the fins may be operated at a higher incremental rotational speed to increase the air movement within the building. Likewise, if the air temperature needs to be increased, the fan speeds may again be incrementally altered The same method may be employed to effect changes in airflow rate in order to obtain a desired value for various target parameters. 
     Additionally, environmental parameters outside of the building may be monitored to assist in the regulation of airflow in the internal environment For example, external air temperature nay be monitored, compared to the desired building temperature, if desired, and admitted into the building via a ventilation inlet. Various restrictions may be placed on the admittance of outside air, such as preventing outside air from being introduced into the building when the outside temperature is above or below a predetermined target or range. 
     The method may also include conditioning the air which is provided to the internal environment. Such conditioning may include, for example, passing the air over heating or cooling coils, subjecting the air to a filtering process, or subjecting the air to a process of humidification or dehumidification. 
     In accordance with another aspect of the present invention, a system is provided for controlling the internal environment of a building designated for human occupancy. The system includes an air handling unit, including a fan or multiple fans that are adapted to operate continuously. The fins are configured to allow their continuous operation at speeds which are below their operational capacity. More specifically, each fan is coupled to a variable-speed drive for controlling the operational speed thereof At least one sensor is employed to monitor one or more internal environmental parameters of the building, such as temperature, humidity, gas levels, or particulate levels. The sensor is coupled to an electronic control unit which is, in turn, coupled to at least one of the variable-speed drives. The sensor provides a signal to the electronic control unit, the signal represent a measured value of an internal environmental parameter. The electronic control unit then provides a signal to the variable-speed drive based upon the sensed parameter, causing the associated fan to vary in speed accordingly. 
     Additional elements may be configured with the system to render greater control and flexibility. For example, sensors monitoring an external environment may be coupled to the electronic control unit to assist in determining fan speed. Ventilation inlets or outlets may also be coupled to the electronic control unit for controlling flow of air into and out of the building, respectively. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The foregoes and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which; 
     FIG. 1 is an elevational view of an HVAC system in accordance with certain aspects of the present invention; 
     FIG. 2 is a schematic representation of an environmental control system in accordance with certain aspects of the present invention; 
     FIG. 3 is a block diagram illustrative of the logic employed in one embodiment of the invention; and 
     FIG. 4 is a block diagram illustrative of the logic implemented according to another embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, an HVAC system  10  implementing an environmental control system according to a particular embodiment of the invention is shown. The HVAC system  10  is implemented in a building designed for human occupancy which may include exterior and interior walls  12  and  14  which define the geographical locale of the internal environment  16  and separate it from an external environment  18 . An air handling unit  20  is housed toward one end of a main air duct or plenum referred to as the supply duct  22 . The air handling unit  20  includes at least one fan or blower  24  for inducing movement of air through the supply duct  22  and into the internal environment  16 . Alternatively, the supply duct  22  may feed numerous secondary ducts (not shown) which may branch off and empty into the internal environment  16  at multiple locations. 
     In addition to the fan  24 , the air handling unit  20  may include various conditioning devices such as a filter  26 , a set of cooling coils  28 , and/or a set of heating coils  30 . Each of the conditioning devices may alter a given parameter of air as it passes by or through the device. For example, the filter  26  may remove unwanted particulates from the air. The cooling and heating coils  28  and  30  may alter the temperature of the air. Alternatively, the cooling and heating coils  28  and  30  may be operated individually or simultaneously to alter the humidity of the air Additional devices may also be used in conjunction with the air handling unit  20  to effect a change in one or more parameters of the air. Such conditioning devices  26 ,  28  and  30 , used independently or in combination, may be effective in assist with the control of the internal environment  16  in conjunction with the disclosed system and method. 
     A second fan or blower  32  is located in a return duct  34  and draws air from the internal environment  16  for either exhaust or recirculation, as further discussed below. The supply fan  24  and the return fan  32  are coupled to variable-speed drives  36  and  38 , respectively. The variable-speed drives  36  and  38  control the operating speed of the fans, thus allowing for a varied flow rate of air passing through the ducts  22  and  34 . The return duct  34  and supply duct  22  have a connecting duct  40  which includes a set of louvers or adjustable vents  42 . Similar louvers  44  may also be located near the exhaust region  46  of the return duct  34  with another set of louvers  48  optimally being located near the entrance  50  of the supply duct  22 . Each set of louvers  42 ,  44  and  48  is operably coupled to an independent actuator  52 ,  54  and  56  respectively. The actuators may be controlled by various known mechanisms such as by pneumatic, hydraulic or electromechanical devices to adjust the louvers  42 ,  44  and  48  between an open and closed position. By altering the position of the louvers, the flow path of the air within the ducts is also altered. This further assists in controlling the quality of the air entering into the internal environment  16  For example, air flowing through the supply duct  22  into the internal environment  16  may be supplied as fresh external air from the external environment  18  as shown by flow indicators  58 . The air supply may alternatively consist of return air directed through the connecting duct  40 , as shown by flow indicators  60 . The supply air may also comprise fresh air and return air which is combined in the mixing plenum  62  prior to entering the air handling unit  20 . Return air may be exhausted to the vernal environment  18  depending on various external and internal conditions. The louvers  42 ,  44  and  48  help to determine the composition of the air flowing through the supply duct  22 . 
     Various sensors can be positioned throughout the HVAC system for determining environmental parameters. For example, a first sensor  64  can be included to determine a parameter of the internal environment  16 , a second sensor  66  can be included for determining an environmental parameter of the air in the return duct  34 , and another sensor  68  (located in the external environment  18 ) can be included for determining a parameter of the external air. Such parameters may include, for example, the temperature or the humidity of the air at the respective locations of the sensors  64 ,  66  and  68 . Additionally, other environmental parameters such as specified gas levels (such as CO 2 ) or particulate levels may be monitored using the sensors. It is also contemplated that additional sensors may be utilized or alternative locations may be selected to customize the HVAC system  10  to a specific building in which it is installed. 
     Referring now to FIG. 2, a schematic of a control system  70  for the HVAC system  10  of FIG. 1 is presented. The supply fan  24  and return fan  32  are each connected to their respective variable-speed drives  36  and  38 . There are numerous types of variable-speed drives commercially available, each having various benefits and features. It is contemplated that the present system and method may be practiced utilizing different types of variable-speed drives for varying the rotational speed of the fans  24  and  32 . For example, a variable-speed drive of the type employing a magnetic clutch may be used in the present technique. Such a drive varies the current supplied to the clutch, causing the magnetic force to vary between the clutch and the shaft. This allows a certain amount of slipage to occur between the shaft and the clutch, resulting in variation in the rotational speed of fans  24  and  32 . While such a drive, and numerous others, may be suitable for use in practicing the present technique, the preferred drives utilized in the presently disclosed embodiment are variable-frequency drives, sometimes referred to as inverter drives. 
     As known by those skilled in the art, a variable-frequency drive (VFD) is an electronic controller that adjusts the speed of an electric motor by modulating the power being delivered. More specifically, the speed of the electric motor is controlled by modulating the frequency of the power being supplied. The standard frequency of AC power in the United States is 60 Hz. A standard electric motor constructed for use in the United States is designed to be operated with a 60 Hz power supply. A decrease in the frequency of the power supply will result in a corresponding decrease in motor speed For example, an electric motor that rotates at 100 rpm with a 60 Hz power supply would run at 50 rpm when the power supply is reduced to 30 Hz. 
     Referring still to FIG. 2, one or more of the VFD&#39;s  36  and  38 , the actuators  52 ,  54  and  56 , and the sensors  64 ,  66  and  68  are connected to a control unit  72  by way of electrical wring  74  such as a dedicated harness. Alternatively, the electrical wiring may be a common bus such as in a controller area network. In a particular embodiment of the invention, the control unit receives signals from the various sensors  64 ,  66  and  68 , processes the information it receives, and then sends out command signals to the VFD&#39;s  36  and  38  and/or the actuators  52 ,  54  and  56 . The VFD&#39;s  36  and  38  then interpret the command signals and send corresponding drive signals to the fans  24  and  32 , respectively. In the above-described embodiment, a drive signal may include a signal from a power supply having an appropriately modulated frequency, 
     Through proper programing of either the control unit  72 , the VFD&#39;s  36  and  38 , or both, maximum speed settings may be established for the fans  24  and  32 . Likewise, minimum speed settings may be set for the fans  24  and  32 . Furthermore, parameter setpoints may be established for the overall operation and logic of the system For example, a temperature value at which the building, or a specific region of the building, is to be maintained may be defined. Having a defined temperature value and sensing air temperature at various points in the stream of airflow, the system will operate to adjust fan speed and/or adjust the mix of airflow to alter an existing environmental parameter. It is noted that, with such a system, greater flexibility is realized through the use of variable-speed drives. By using VFD&#39;s or some other variable-speed drive, more gradual changes to the environment may be achieved. 
     The system of the present invention also provides reduced power consumption as a result of the nonlinear relationship between power consumption and fan speed. For example, a twenty percent reduction in fan speed can result in a fifty percent reduction in power consumption. Knowing that the rate of airflow varies linearly with fan speed, a simple calculation may be performed to compare airflow and power consumption for a system operating at full speed with a system operating at a reduced fan speed of eighty percent. A system operating at full power may circulate air, for example, at 100,000 cfm (cubic feet per minute). This system will circulate 6,000,000 cubic feet of air in a given hour. The reduced-speed system, however, will circulate air at a rate of 80,000 cfm, requiring an hour and fifteen minutes to circulate 6,000,000 cubic feet of air. However, even with the additional fifteen minutes of operating time, the reduced-speed system only consumes sixty-two and a half percent of the power used by the full-speed system. Indeed, operating the fan at even slower speeds can net even larger savings in power. In view of the energy savings, a fan may be operated continuously to maintain the building&#39;s environment within a tightly defined parameter range. 
     It is noted that while the schematic of FIG. 2 shows a single control unit  72 , multiple controllers may be employed in operation of the HVAC system  10 . For example, the control system  70  could be divided into subsystems wherein the supply fan  24  and drive  36  are designed as an individual subsystem. Similarly, the control of the return fan  32  and drive  38  may be combined to form a subsystem. Alternatively, one subsystem might include both fans  24  &amp;  32  with their respective drives  36  and  38 , while a second subsystem might include operation of the louvers  42 ,  44  and  48  by control of their associated actuators  52 ,  54 and  56 , respectively. Additionally, conditioning devices such as the cooling or heating coils  28  and  30  may be included in the control system  70 . 
     Turning now to FIG. 3, and with reference to FIGS. 1 and 2, the logic employed according to one aspect of the present technique is discussed. First, a parameter setpoint  142  is defined. The parameter setpoint is the value at which the storage facility environment should be maintained, which setpoints, for example, correlate to one or more values relating to temperature, humidity, particulate levels or some other environmental parameter For sake of clarity and not by way of limitation, the maintenance of internal temperature will be used as an example of controlling a specific environmental parameter throughout the following discussion. The example will be discussed in terms of cooling the building; however, the same logic may be applied in heating the building or maintaining some other parameter. 
     Maximum and minimum fan speeds are defined, as shown at step  144 , and are programed into either the control unit  72  or the VFD  36 . Alternatively, maximum and minimum power consumption rates may be defined for the fans. An environmental parameter is then sensed  146  and an appropriate data signal is communicated to the control unit  72 . The control unit  72  then determines if the sensed temperature is greater than the defined setpoint as indicated at  148 . If the result is affirmative, then the control unit  72  determines whether the current speed of the supply fan  24  is less than the defined maximum, as shown at step  150 . If this inquiry is affirmative, then the control unit  72  will increase the speed of the fan  24  as indicated at step  152 . Following the increase of fan speed, the temperature is again sensed, as shown at step  146 , with the process ready to repeat itself. If the inquiry at step  154  is answered negatively, then the speed of the supply fan  24  is maintained at the maximum speed and the process returns to step  146 . 
     If, however, the inquiry at  148  yields a negative response, the control unit  72  will then inquire whether the sensed temperature is less than the defined setpoint, as shown at  156 , If the result is affirmative, a second inquiry is made as to whether the fan speed is greater than the minimum setting, as indicated at step  158 . If the result to this inquiry is affirmative, then the fan speed is reduced, as shown at  160 , and the process returns to step  146 . If the inquiry at step  158  yields a negative response, then the fan speed is maintained at the minimum speed  162  and the process returns to step  146 . Finally, if the inquiry at step  156  yields a negative result, the process likewise returns to step  146 . 
     Thus, using the logic described above, the fan is operated continuously and, if the maximum setting is less than full power, it is operated continuously at a reduced speed. In the example above, the present technique allows for the continuous control of fan speed to maintain the building&#39;s environment at a defined temperature. It is noted that the chosen parameter need not be temperature. It is also noted that the above logic is discussed in reference to the speed of the supply fan  24  and that the control unit  72  may contemporaneously control the ventilation louvers  42 ;  44  and  48  as well as the speed of the return fan  32  to influence the building&#39;s environment. 
     Referring to FIG. 4, the operational logic according to an alternative embodiment is presented. First, parameter setpoints are defined as shown at step  172 . Both, an internal setpoint and an external setpoint are defined. The internal setpoint is a parameter value at which the building&#39;s environment should be maintained. For example, it may be a value concerning temperature, humidity, particulate levels or some other environmental parameter. For sake of clarity, the following example will again focus on the control of temperature as the internal parameter to be maintained. The external setpoint is a parameter value which is used to override the system in specific instances. For this discussion, the external setpoint is also defined in terms of temperature. The example will be discussed in terms of cooling the building; however, the same logic may be applied in heating the building or maintaining one or more other parameter(s). 
     While not shown specifically in FIG. 4, maximum and minimum fan speeds may be defined according to the above description in reference to FIG.  3 . An internal environmental parameter is then sensed, as shown at step  174 , and an appropriate data signal is communicated to the control unit  72 . An external parameter is also sensed as shown at  176 . AS noted above, the external parameter in this example is the ambient temperature outside the building. The control unit  72  then determines if the sensed temperature is less than the defined setpoint as indicated at  178 . If the result is affirmative, then the control unit  72  will decrease the speed of one or more fans  24  and  32  as indicated at  180 . Following the decrease in fan speed, the process returns to step  174 . If the inquiry at step  178  is answered negatively, then the control unit  72  determines whether the sensed temperature is greater than the defined level as indicated at  182 . If the result is negative, then the fan speed is maintained, as shown at  184 , and the process returns to step  176 . If, however, the result is affirmative, the control unit  72  further determines if the external temperature is less than the external setpoint, as seen at step  186 . If the result to the inquiry at  186  is affirmative, then fan speed is increased as shown at step  188  and the process returns to step  176 . If the result to the inquiry at  186  is negative, the control unit  72  determines whether the sensed vernal temperature is greater than the external setpoint, as shown at step  190 . Again, if the result to this inquiry is negative, then the fan speed is maintained, as shown at step  184 , and the process returns to step  176 . If, however, the result to the inquiry at step  190  is affirmative, then the mixture of the supply air is altered as shown at step  192  and the process returns to step  176 . Altering of the supply mixture may include various actions including opening and closing the ventilation louvers  42 ,  44  and  48  as required to recycle return air and exclude external air. Alternatively, or in combination with adjusting the louvers  42 ,  44  and  48 , the speed of the fans  24  and  32  may be adjusted to effect an alteration of the mixture. This may include decreasing the speed of the supply fan  24  while increasing the speed of the return fan  32 . Varying the speed of the fans inversely in conjunction with adjusting the louvers assists in recirculating the air in the building and avoids drawing in external air having a temperature above that which is acceptable. Thus, the inquiries shown at steps  186  and  190  work as a check on the external environment. This allows an ovetide function to be in place such that the admittance of external air having an undesirable parameter does not interfere with the maintenance of one or more internal environmental values. 
     As noted above, such logic may also be employed to control environmental parameters different than those attributed in the above example with similar results being achieved. It is further noted that variations in the logic described may be employed in controlling the fans  24  and  32  in either a synchronous or independent fashion. Additionally, it should be understood that while the logic discussed in connection with FIGS. 3 and 4 are related to a particular system, the logic may be applied to other systems, or subsystems, as disclosed herein. For example, the logic described in FIGS. 3 and 4 may be farther adapted for use with the conditioning systems and devices discussed herein. 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed herein. Rater, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims. For example, it is contemplated that while the embodiments and techniques described above have been shown to be combined into a single system, they may operate as individual system or as subsystems.