U.S. patent application number 13/111652 was filed with the patent office on 2012-01-19 for auto cure variable fan drive control system and associated methods.
This patent application is currently assigned to JMC Enterprises, Inc.. Invention is credited to Robert Drozdowski, Bruce Johnson, Joel Micka.
Application Number | 20120012092 13/111652 |
Document ID | / |
Family ID | 45465918 |
Filed Date | 2012-01-19 |
United States Patent
Application |
20120012092 |
Kind Code |
A1 |
Micka; Joel ; et
al. |
January 19, 2012 |
AUTO CURE VARIABLE FAN DRIVE CONTROL SYSTEM AND ASSOCIATED
METHODS
Abstract
Methods and systems for controlling air characteristics for
storage facilities. A controller and temperature sensors can detect
an external temperature and compare it to a reference temperature.
Depending on the relationship between the external temperature and
the reference temperature (e.g. warmer or colder) the controller
can initiate a burner, open an air intake, and operate fans to
achieve desirable conditions within the facility efficiently.
Inventors: |
Micka; Joel; (Kennewick,
WA) ; Drozdowski; Robert; (Richland, WA) ;
Johnson; Bruce; (Kennewick, WA) |
Assignee: |
JMC Enterprises, Inc.
Kennewick
WA
|
Family ID: |
45465918 |
Appl. No.: |
13/111652 |
Filed: |
May 19, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61346105 |
May 19, 2010 |
|
|
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Current U.S.
Class: |
126/112 |
Current CPC
Class: |
A23B 7/00 20130101; F24H
9/2085 20130101 |
Class at
Publication: |
126/112 |
International
Class: |
F24H 3/02 20060101
F24H003/02 |
Claims
1. A method for controlling interior air temperature inside a crop
storage facility, wherein a fan moves heated air from a burner in
the storage facility and can draw air into the storage facility
through an air intake, the method comprising: detecting a first
temperature of air inside the storage facility; comparing the first
temperature to a second temperature; if the first temperature is
less than the second temperature, increasing an operating level of
the burner; if the first temperature is less than the second
temperature and the burner level is at a predetermined maximum
operating level, decreasing a fan output; if the first temperature
is less than the second temperature and the fan throughput is at a
predetermined minimum level and the burner is at or above a
predetermined maximum, at least partially closing the air intake;
and if the first temperature is less than the second temperature,
the burner is at the predetermined maximum operating level, and the
air intake is fully closed, recirculating the air inside the
storage facility.
2. The method of claim 1, further comprising controlling the fan
output with a variable frequency drive.
3. The method of claim 1 wherein comparing the first temperature to
the second temperature comprises comparing the first temperature to
the second temperature at predefined time intervals.
4. The method of claim 3 wherein the predefined time intervals are
between five and ten minutes.
5. The method of claim 1, further comprising if the air intake is
closed, periodically comparing temperature outside the facility to
a predefined temperature.
6. The method of claim 1, further comprising: after fully closing
the air intake, periodically comparing the temperature outside the
facility to a predefined temperature; if the temperature outside
the facility is greater than the predefined temperature, opening
the air intake and increasing the fan output at each periodic
comparison between the temperature outside the facility and the
predefined temperature; and if the air intake reaches a maximum
open status, decrementing the burner operating level.
7. A method for controlling air temperature in a crop storage
facility, the method comprising: monitoring an external
temperature; comparing the external temperature to a first
reference temperature; if the external temperature is greater than
the first reference temperature, opening an air intake door to the
facility to permit external air to enter the facility and operating
a burner at a first level; with the air intake door open,
monitoring a temperature within an air plenum of the facility; if
the temperature in the air plenum is below a second reference
temperature, closing the air intake door and turning off the
burner; and if the temperature in the air plenum is above the
second reference temperature, opening the air intake door.
8. The method of claim 7, further comprising if the temperature in
the air plenum is above the second reference temperature, reducing
the level of the burner.
9. The method of claim 7 wherein opening an air intake door
comprises operating a variable frequency drive fan.
10. The method of claim 7 wherein monitoring the external
temperature and comparing the external temperature to the first
reference temperature is performed by a controller.
11. The method of claim 7 wherein the storage facility contains
perishable goods, and wherein the first reference temperature and
the second reference temperature are dependent upon desirable
conditions for the perishable goods.
12. The method of claim 11 wherein the perishable goods are at
least one of onions or potatoes.
13. The method of claim 7 wherein monitoring the temperature within
the air plenum comprises operating a plurality of sensors within
the air plenum to detect temperature at a plurality of locations
within the air plenum.
14. The method of claim 13 wherein monitoring the temperature
within the air plenum comprises averaging the temperature from the
plurality of sensors.
15. The method of claim 7 wherein initiating a burner at a high
level comprises initiating the burner at a maximum level.
16. A method for operating an air control system of a facility in a
warm-to-cold operation, the air control having a burner, at least
one fan, and an air intake, wherein the air control system is
reversible between the warm-to-cold operation and a cold-to-warm
operation, the method comprising: operating the air control system
in a warm-to-cold operation; comparing an interior air temperature
of the facility to a reference temperature; if the interior air
temperature is greater than the reference temperature, reversing
the air control system from the warm-to-cold operation to the
cold-to-warm operation; if the interior air temperature is less
than the reference temperature, increasing the burner; if the
burner has reached a maximum operating state, and the interior air
temperature is greater than the reference temperature, reversing
the air control system from the warm-to-cold operation to the
cold-to-warm operation; if the burner has reached a maximum
operating state and the interior air temperature is less than the
reference temperature, reducing the fan; if the fan has reached a
minimum operating state, and the interior air temperature is
greater than the reference temperature, reversing the air control
system from the warm-to-cold operation to the warm-to-cold
operation; if the fan has reached a minimum operating state, and
the interior air temperature is less than the reference
temperature, at least partially closing the air intake; and if the
air intake is closed, entering a recirculation operation.
17. The method of claim 16, further comprising recording an
external temperature when entering the recirculation operation, and
using the recorded external temperature as the reference
temperature.
18. The method of claim 16 wherein the recirculation operation
comprises an air treatment process using a closed circuit of air
within the facility.
19. The method of claim 16, further comprising comparing the
interior air temperature to the reference temperature and
identifying a difference between the interior air temperature and
the reference number, the difference having a magnitude.
20. The method of claim 19 wherein reducing the fan comprises
reducing the fan by an amount dependent upon the magnitude of the
difference.
21. The method of claim 19 wherein increasing the burner comprises
increasing the burner by an amount dependent upon the magnitude of
the difference.
22. The method of claim 19 wherein closing the air intake comprises
closing the air intake by an amount dependent upon the magnitude of
the difference.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority to U.S. Provisional
Application No. 61/346,105, filed May 19, 2010, the disclosure of
which is incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The following disclosure relates generally to devices,
systems and methods for controlling air characteristics in crop
storage facilities.
BACKGROUND
[0003] Crops such as onions, garlic, tulip bulbs, and other,
similar goods are sensitive to their surroundings and must be cured
between harvesting and consumption. Controlling the air quality,
temperature, humidity, and other parameters in facilities where
these crops are stored requires energy. Accordingly, efficient
methods for preserving crops without sacrificing revenue are
important to farmers and companies. Daily temperature variation can
limit the efficiency of many conventional crop storage systems,
particularly in dry, desert areas such as the southwestern United
States where the temperature variation is extreme. One approach has
been to heat air as it enters a storage facility. Doing so is
expensive and without proper controls can be inefficient and can
even harm the stored crop. Also, despite the increasing size of
burners used at such facilities, frequently the temperature drop is
too great for even the largest and most sophisticated burners to
handle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a partially schematic illustration of a storage
facility and a system for controlling the interior air
characteristics within the storage facility in accordance with some
embodiments of the present disclosure.
[0005] FIG. 2 is a block diagram illustrating a method for
controlling the internal air characteristics of a storage facility
in accordance with several embodiments of the present
disclosure.
[0006] FIG. 3 is a block diagram illustrating a method for
controlling the internal air characteristics of a storage facility
in accordance with selected embodiments of the present
disclosure.
[0007] FIG. 4 is a block diagram illustrating a method for
controlling the internal air characteristics of a storage facility
in accordance with several embodiments of the present
disclosure.
[0008] FIG. 5 is a block diagram illustrating a method for
controlling the internal air characteristics of a storage facility
in accordance with several embodiments of the present
disclosure.
DETAILED DESCRIPTION
[0009] The present disclosure is directed generally to apparatuses,
devices and associated methods for controlling interior air
characteristics of a storage facility.
[0010] Several details describing structures and processes that are
well-known and often associated with storage facilities and air
handling equipment are not set forth in the following description
to avoid unnecessarily obscuring embodiments of the disclosure.
Moreover, although the following disclosure sets forth several
embodiments of the invention, other embodiments can have different
configurations, arrangements, and/or components than those
described herein without departing from the spirit or scope of the
present disclosure. For example, other embodiments may have
additional elements, or they may lack one or more of the elements
described below with reference to FIGS. 1-5.
[0011] Throughout this discussion, reference will be made to onions
as a crop to be cured and treated by the disclosed systems and
methods for conciseness and clarity. It will be appreciated,
however, that any other crop can be cured and treated by the
disclosed systems and methods. Garlic, tulip bulbs, and other bulb
crops, for example, are generally similar to onions, but the
disclosed methods and systems can be used with any other crop.
[0012] FIG. 1 is a partially schematic illustration of a storage
facility 100 according to several embodiments of the disclosure.
The storage facility 100 can contain goods 110, such as onions,
potatoes, and/or other types of crops or other products. The
storage facility 100 can be part of a series of similar storages,
or can be a stand-alone unit. The storage facility 100 can have
virtually any suitable size to meet the needs of a particular
farmer or storage company. The goods 110 can be loosely stored in
the storage facility 100 or can be in individual packaging or
crates.
[0013] After harvesting or collecting the goods 110, the goods 110
may require a period of time for curing during which environmental
conditions in the storage facility 100 can be controlled. In one
aspect of this embodiment, the storage facility 100 can include an
air control system 105 that uses air from outside the storage
facility 100 to achieve a desired temperature and humidity within
the storage facility 100. The air control system 105 can include an
air intake 120, a fan 130, and a burner 140. In some embodiments,
the fan 130 includes a 10-30 horsepower propeller-type ventilation
fan, and the burner 140 includes a vane-axial combustion heater.
Other types of fans and burners can be used as well. Air flows
through the intake 120, the fan 130, and the burner 140 from
outside the storage facility 100 until it reaches the goods 110.
The air can travel along a plenum 150 which can include several
pipes, ducts, and other passageways. The plenum 150 generally
describes mechanisms through which the air travels, and as such the
plenum 150 can have virtually any suitable layout and
configuration. Intake 120 can include one or more intake ports
placed around the storage facility 100. A corresponding air outlet
152 can be operated analogously to the intake 120 to ensure the
conditioned air is distributed throughout the storage facility 100.
Similarly, the intake 120, fans 130, and burner 140 can include
multiple units arranged advantageously around the storage facility
100. For purposes of illustration and ease of reference, however,
FIG. 1 depicts a simplified, schematic view of these
components.
[0014] In some embodiments, a controller 160 is connected to the
intake 120, the fans 130, and the burner 140. The controller 160
can be local to the storage facility 100 or it can be located
remotely and can communicate with the storage facility 100 (or with
several, distributed storages 100). The controller 160 can be
controlled through a remote management system as discloses in U.S.
Provisional Patent Application No. 61/235,663, entitled Remote
Management of Storage Facilities, which is hereby incorporated by
reference. A series of sensors 170 can be disposed throughout the
storage facility 100 and outside of the storage facility 100 to
gather data such as temperature, humidity, time, and other
parameters. The sensors 170 can communicate with the controller 160
to provide the controller 160 with data to operate the storage
facility 100.
[0015] The storage facility 100 can operate to cure the goods 110
by maintaining a desired air temperature and air intake to the
storage facility 100. Some curing and/or storage operations are
more favorably achieved by a high air throughput and relatively
warm temperatures. For example, a storage facility 100 used to cure
and dry onions, garlic, tulips, or other bulb crops benefit from a
relatively large amount of air throughput and at comparatively high
temperatures. Other storage facilities 100 used for other types of
goods 110 may thrive in different conditions. Accordingly,
depending on the needs and character of the goods 110, a preferred
interior temperature is reached and the intake 120 is fully open to
admit the maximum amount of exterior air to the storage facility
100. The intake 120 can be opened and closed in degrees to change
the amount of air admitted to the storage facility 100, and the
burner 130 can be used at different levels to increase the
temperature within the storage facility 100 when the outside air is
warmer or colder than a desired interior temperature. In some
embodiments, the fans 130 comprise variable frequency drives (VFD)
that can alter the throughput of the fans 130 with great accuracy
and reliability. The controller 160 can manage these variables in
this instance.
[0016] The controller 160 can comprise a programmable logic
controller (PLC) or other microprocessor-based industrial control
system that communicates with components of the storage facility
100 through data and/or signal links to control switching tasks,
machine timing, process controls, data manipulation, etc. In this
regard, the controller 160 can include one or more processors that
operate in accordance with computer-executable instructions stored
or distributed on computer-readable media. The computer-readable
media can include magnetic and optically readable and removable
computer discs, firmware such as chips (e.g., EEPROM chips),
magnetic cassettes, tape drives, RAMs, ROMs, etc. Indeed, any
medium for storing or transmitting computer-readable instructions
and data may be employed. The controller 160 and embodiments
thereof can be embodied in a special purpose computer or data
processor that is specifically programmed, configured or
constructed to perform one or more of the machine operations
explained in detail below. Those of ordinary skill in the relevant
art will appreciate, however, that the storage facility 100 and
components such as the intake 120, the fans 130, and the burner 140
can be controlled with other types of processing devices including,
for example, multi-processor systems, microprocessor-based or
programmable consumer electronics, network computers, and the like.
Data structures and transmission of data and/or signals particular
to various aspects of the controller 160 are also encompassed
within the scope of the present disclosure.
[0017] FIG. 2 is a block diagram illustrating a method 200 for
controlling air characteristics within a storage facility 100
according to several embodiments of the present disclosure in which
the general trend in temperature is from high to low (e.g., at
nightfall). The method 200 can be carried out by the system 105,
defined generally as the components of the storage facility 100
that control the conditions (e.g., the air and temperature
conditions) within the storage facility 100.
[0018] An initial condition 210 according to some embodiments is
defined by an outside air temperature that is above a desired
interior air temperature, such that the intake 120 is fully open
and the maximum amount of air is entering the storage facility 100.
As noted above, a storage facility 100 used for bulb products
generally uses a large amount of air at a high temperature to cure
and store the bulb products. Other stored goods 110 have different
desirable conditions, and parameters of this disclose can be
adjusted accordingly. In the initial condition 210, the fan 130
operates at a high or maximum level, and the burner 130 is not in
use. The temperature in the air plenum 150 is periodically measured
220. (The temperature can be measured at various locations within
the storage facility 100, including the plenum 150.) If the
temperature is at or above a threshold temperature, T, the method
includes waiting a predetermined period of time before checking the
temperature again 220. In an example, T can be 70.degree.
Fahrenheit. If the temperature is below T, the system 105
determines 230 whether the burner 140 is operating at the high or
maximum level. If the burner 140 is not operating at all, or is
operating at a level below the high or maximum level, the burner
140 can be turned up 240. Control then passes to measuring the
temperature 220 until the temperature in the plenum 150 drops below
T again.
[0019] If the burner 140 is operating at the maximum available
level, the system 205 determines 250 whether the fans 130 are
operating at their minimum level. The minimum level for the fans
130 can be where the fans are operating at a low level, or can be
where the fans 130 are not operating at all. If the fans 130 are
not at their lowest level, the fans 130 can be reduced 260. Because
the volume of air passing through the fans 130 is generally
directly proportional to the energy required to heat the air by a
specific amount, reducing the air can have the effect of increasing
the temperature in the plenum 150 and in the storage facility 100.
This allows for curing the goods 110 more efficiently despite
colder, less favorable outside conditions. If the fans 130 have
reached their minimum level, the intake 120 position can be
determined 270.
[0020] If the intake 120 is open, the intake 120 can be stepped 280
toward a closed position. In some embodiments, the intake 120 is a
door or set of doors that can move between several positions
between open and closed to vary the size of the air passage and
hence the air throughput. The doors can be operated by actuators
such as pneumatic, hydraulic, or mechanical means. Closing the
intake 120 can further reduce the throughput of air in the storage
facility 100, which in turn increases the temperature in the
plenum. Similarly to slowing the fans 130, this allows for
effective curing despite unfavorable conditions outside the storage
facility 100. Once the doors are closed completely, the system 105
enters a recirculation phase 190 in which the air within the
storage facility 100 is recirculated throughout the storage
facility to continue curing to a reduced extent while the
conditions outside the storage facility 100 are undesirable. This
helps to maintain the temperature within the storage facility 100
at a level at which the goods 110 can continue to cure until
conditions outside improve.
[0021] In some embodiments, the changing conditions outside of the
storage facility 100 are caused by nightfall. During a typical day
the temperature will drop at sunset and rise at dawn. The sensors
170 can detect this temperature drop and communicate with the
controller 160 to initiate the method 200 described above. In some
embodiments, this process depends upon temperature and not upon
time of day. This allows the central system 105 to be sensitive to
temperature fluctuations caused by weather. A delay between
temperature readings can help to make the system 105 immune to
"noise." For example, if a short-lived rain or wind causes the
temperature to drop for less time than the duration of the delay
(e.g., five minutes, ten minutes, etc.), the storage facility 100
can ignore these changes and continue operation. However, if a
storm lasts long enough to affect the interior temperature, such as
the temperature in the plenum 150, the controller 160 can react and
execute the method 200 described above. This creates more efficient
use of ambient temperature for curing or storage of goods 110.
[0022] FIG. 3 is a block diagram depicting a method 300 for
controlling interior air characteristics of a storage facility 100
in accordance with another embodiment of the present disclosure.
Similar to the method 200 discussed above and shown in FIG. 2, the
method 300 is for use generally when the temperature trend is high
to low. An initial condition 305 can be generally similar to the
initial condition 210 described above with reference to FIG. 2. In
particular, the intake 120 is fully open, the fans 130 are
operating at their maximum capacity, and the burner 140 is not in
use. Next, the sensors 170 can measure the temperature in the
plenum 150 and in other locations within the storage facility 100,
and determine 310 whether the temperature is below a threshold
temperature, T. If so, the burner condition can be determined 315
and increased 320 if not operating at maximum capacity. After a
predetermined period of time, (e.g., five minutes, ten minutes,
etc.) the temperature can be determined 310 again. After increasing
the burner 140 the temperature will likely rise or at least
maintain a steady level for a period of time.
[0023] If the temperature is not less than the predetermined
threshold temperature, T, a second temperature inquiry can
determine 325 whether the temperature has risen by more than a
predetermined temperature difference, A, above the temperature T.
In some embodiments, this predetermined temperature difference A is
5.degree. Fahrenheit, or about 5.degree. F. If not, the system 105
can wait 330 and then return to compare 310 the temperature in the
storage facility 100 to the threshold temperature, T. If, however,
the temperature in the storage facility 100 has increased by more
than A, the system 105 can reverse 335. Specific examples of the
reverse operation will be given below with reference to FIG. 4.
[0024] The method 300 continues when the burner 130 is operating at
a maximum level by determining 340 whether the fans 130 are
operating at their lowest setting. If not, the speed of the fans
130 can be decremented 345. As discussed above, reducing the speed
of the fans 130 can increase the temperature in the storage
facility 100 to continue curing or treating the goods 110 even when
the outside temperature is not ideal. After decrementing the speed
of the fans 130, the temperature is again compared 350 to the
threshold temperature, T. If the temperature is not below T, the
temperature can be measured 355 for an increase of greater than A.
If the temperature has risen greater than A, the method 300 will
reverse 335; otherwise, the system 105 waits 360 for a
predetermined period before comparing the temperature in the
storage facility 100 to the threshold temperature, T.
[0025] Once the fans 130 reach the minimum operating level, the
intake 120 condition is assessed 365. If the intake 120 is open,
the intake 120 can be stepped toward the closed position 370. After
at least partially closing the intake 120, the temperature in the
storage facility 100 can again be compared against the threshold
temperature, T. If the temperature is still below T the intake 120
can be assessed 365 and stepped toward the closed position 370
again. If the temperature in the storage facility 100 is not below
T, the system 105 can determine 380 whether the temperature has
risen by more than a predetermined amount, A. If so, the system 105
can reverse 335; otherwise, the system 105 waits before returning
to measuring the temperature in the storage facility 100 again.
Once the intake 120 is fully closed, the system 105 can enter a
recirculation phase 390 similar to the recirculation phase 290
described above with reference to FIG. 2.
[0026] The method 300 includes three generally analogous stages in
which the temperature is compared to a reference temperature, T,
and an action is taken to maintain a given temperature in the
storage facility 100. In several embodiments, the stages are 1)
increasing the burner 140, 2) decreasing the fans 130, and 3)
closing the doors. Between each step the temperature is measured
and further incremental steps are performed. If the temperature
increases beyond a set range, the operation can reverse to lower
the temperature. Although the method 300 depicted in FIG. 3 shows
these three stages occurring sequentially, other embodiments can
include performing two or more of these stages simultaneously, or
performing these stages in other sequences, and/or omitting one of
these stages. For example, if the temperature is determined to be
below the threshold temperature, T, the burner 140 can be increased
and the fans 130 can be decremented before measuring the
temperature again. Alternatively, the fans 130 and the intake 120
can be decremented jointly without necessarily measuring the
temperature between increments.
[0027] FIG. 4 illustrates a method 400 for controlling interior air
characteristics of a storage facility 100 in accordance with
another embodiment of the present disclosure. The method 400 is
generally for use when the temperature trend is from low to high
(e.g., at dawn). When moving from cold to warm temperatures, an
initial condition 405 can include a recirculation phase described
above with reference to FIGS. 2 and 3, where the intake 120 (and
corresponding outlet) is closed and air is moved throughout the
storage facility 100 to a limited degree. The central system 105
can measure 410 the external temperature periodically and compare
it to a temperature at which the initial condition 405 was reached.
For example, the external temperature can be measured when the
intake 120 is fully closed and the storage facility 100 enters a
recirculation phase. If the temperature outside the storage
facility 100 has risen by more than a threshold amount (e.g.,
5.degree. or 10.degree. after a predetermined amount of time 415
(e.g., five or ten minutes), the method 400 can begin 420. (In some
embodiments, the method 400 can begin when the system 105 reverses
according to the method 300 described above with reference to FIG.
3.) At this point, the burner 140 can be turned on and operated at
a high or maximum level. The temperature in the plenum 150 or
elsewhere within the storage facility 100 can be measured and
compared 425 to a reference temperature, T. If the temperature is
less than or equal to T, the system 105 can wait 430 a set amount
of time. If the reference temperature, T, is exceeded, the system
105 can step open 435 the intake 120 and increase 440 the fan 130.
While the fan 130 is operating below a maximum level and while the
intake 120 is partially closed, the system 105 can continue the
loop. Once the fan 130 reaches the maximum level and the intake is
fully open, any further increase in exterior air temperature will
be reflected in an increase in interior air temperature.
[0028] With the burner 140 and fans 130 operating at maximum and
the intake 120 fully open, the temperature in the plenum 150 can be
measured and compared to a desired reference temperature. Until
this temperature is exceeded, the system 105 can wait 455 between
measurements. If the temperature is above the desired reference
temperature, the operational status of the burner 140 can be
assessed 460, and if the burner 140 is still running, it can be
turned down 465. Once the burner is off, the system 105 can stop
470. In this state, the intake air is warm enough that the desired
curing/storage temperature is reached within the storage facility
100 without using the burner, with the intake 120 fully open, and
with the fans 130 operating at maximum. This condition is similar
to the initial conditions 210, 305 described with reference to
FIGS. 2 and 3. Accordingly, the system 105 is ready to perform the
methods 200, 300 described for when the temperature trend is
generally from high to low.
[0029] The method 400 described here includes incrementing 435 the
intake 120 and incrementing the fan 130 simultaneously between
measurements. It is to be appreciated that any incrementing or
decrementing step described in any of FIGS. 2-4 can be performed
sequentially or serially with other incrementing or decrementing
steps. Temperature measurements can be taken at any point during
the methods 200, 300, 400, and can also be taken substantially
continuously throughout the methods.
[0030] FIG. 5 illustrates yet another method 500 according to
several embodiments of the present disclosure in which a storage
facility can recirculate air while outside ambient temperatures
remain cold, but can detect when the outside air has warmed and
then use the warm outside air within the facility. In an
embodiment, the method 500 can be appended to the block diagram of
FIG. 3. In particular, the method 500 can be a continuation of a
recirculation operation 390 shown and described in FIG. 3. The
method 500 can also be used in other conditions that begin with a
recirculation operation 510. Recirculating air within a storage
facility can be performed when ambient temperatures are below a
predetermined threshold at which equipment at the storage facility,
such as a burner, a VFD, etc., cannot achieve desired minimum
temperature within the facility using ambient air as an input. The
temperature outside the facility will inevitably change, however,
and eventually the air will warm to a degree that the air can be
used within the facility. For example, overnight temperatures may
be too low, but at dawn the temperature may rise above acceptable
levels. When the recirculation operation 510 begins, the ambient
temperature can be recorded in memory as "R temp." Periodically,
this temperature can be compared 520 to the current ambient
temperature, and if the ambient temperature has risen above R temp
by a predetermined amount (e.g., 5.degree. F.), certain steps can
be executed 530 to intake this air.
[0031] Before determining that the outside temperature has reached
a sufficiently high temperature, the method 500 can require that a
predetermined time period elapses during which the outside
temperature is higher than R temp. For example, the method 500 can
include comparing the two temperatures and marking a first time at
which the temperature threshold is reached and waiting a
predetermined time (e.g., 999 seconds) before comparing the
temperatures again. If the outside temperature is still above the
threshold temperature the method 500 can include proceeding with
further steps. If the temperature rises above the threshold for
less than the predetermined time period, the period can reset and
continue to monitor the temperature difference. Comparing the
temperatures 520 can include taking many measurements during the
time period and if a sufficient number or percentage of the
measurements are above the threshold, the method 500 can
proceed.
[0032] In some embodiments, a VFD can be turned on to a minimum fan
speed, the doors can be opened, and a burner can be turned on. In
some instances, the burner can be turned on to a maximum level at
this stage because the outside air may be expected to be relatively
cold. After another period elapses, the temperature in the plenum
can be measured 540 to determine whether the situation is stable by
measuring the temperature in the plenum. If not (e.g., if the
ambient air is still too cold to maintain desired conditions within
the facility), the method 500 can include several operations to
verify that the temperature in the plenum cannot be maintained, and
that no transient effects are causing the low temperature. For
example, the method 500 can include checking whether the burner is
operating at a maximum level 550. If not, the burner can be
incremented 530 and the temperature in the plenum can be measured
again 540. If the burner is operating at a maximum temperature, a
timer 560 can start. The timer 560 can be set to any suitable
duration depending on the application and circumstances. Where
transient conditions are expected, the timer can be longer to allow
the transient effects to subside without affecting the method 500.
In contrast, where interruptions and other transient effects are
not expected, the timer can be shorter. In some embodiments, the
timer can be set to between two and sixteen minutes. When the timer
expires, the recirculation operation 510 can resume. If the plenum
temperature is maintained 540, the VFD can be incremented or
decremented, the door opened or shut, and the burner can be
decremented or incremented 580. These variables can each be
adjusted bi-directionally depending on the temperature of the air
in the plenum. For instance, if the air is too cold the VFD can be
decremented, the door can be shut, and the burner incremented; if
the air is too warm the VFD can be incremented, the door opened,
and the burner decremented. After each incremental adjustment to
the VFD, the doors, and the burner, the method can include
determining 590 whether the VFD is at a maximum speed, the door is
fully open, or the burner is off. Once all these variables reach a
maximum state the method 500 can terminate 600 and/or pass control
to another routine.
[0033] The incrementing and decrementing actions described with
reference to FIGS. 2-5 can include steps of equal or unequal
distance as measured by time spacing between actions, temperature
interval, or flow volume change per step. In some embodiments, for
example, the size of the steps is proportional to a temperature
difference between the interior temperature and the predetermined
threshold temperature. The system 105 can operate in a variety of
conditions and is sensitive to temperature variation caused by
daily temperature changes and by other events such as a rainstorm
or wind, etc.
[0034] From the foregoing, it will be appreciated that specific
embodiments of the invention have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the spirit and scope of the various
embodiments of the invention. Further, while various advantages
associated with certain embodiments of the invention have been
described above in the context of those embodiments, other
embodiments may also exhibit such advantages, and not all
embodiments need necessarily exhibit such advantages to fall within
the scope of the invention. The following examples are directed to
additional embodiments of the disclosure.
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