U.S. patent number RE33,600 [Application Number 07/427,259] was granted by the patent office on 1991-06-04 for environmental control system for poultry houses.
This patent grant is currently assigned to Cornell Research Foundation, Inc.. Invention is credited to Michael B. Timmons.
United States Patent |
RE33,600 |
Timmons |
June 4, 1991 |
Environmental control system for poultry houses
Abstract
Method and apparatus for controlling environmental conditions in
an animal house, and particularly in a poultry house, for producing
maximum economic return. The static parameters of the house are
determined, and thereafter continuous measurements are made of
current inside and outside temperatures. The operator makes
periodic assessments of litter condition in the house, and adjusts
the target 24-hour average relative humidity to produce the desired
litter condition. The system controls the heating and ventilation
system to obtain the desired 24-hour average relative humidity
while maintaining the optimum temperature conditions in the house
for maximum economic return.
Inventors: |
Timmons; Michael B. (Ithaca,
NY) |
Assignee: |
Cornell Research Foundation,
Inc. (Ithaca, NY)
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Family
ID: |
27027353 |
Appl.
No.: |
07/427,259 |
Filed: |
October 12, 1989 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
947338 |
Dec 29, 1986 |
04700887 |
Oct 20, 1987 |
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Current U.S.
Class: |
236/49.3;
119/306; 119/448; 236/44C; 236/91C; 237/3 |
Current CPC
Class: |
A01K
1/0047 (20130101); G05D 23/1931 (20130101) |
Current International
Class: |
A01K
1/00 (20060101); G05D 23/19 (20060101); F24F
007/00 (); G05D 021/00 () |
Field of
Search: |
;236/49.3,94,44R,44A,44C,44E,91A,91C,6 ;237/3 ;165/16
;119/31,32,33,34,17,21 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"Use of Low-Cost Microcomputers to Control Poultry House Heating,
Ventilation and Lighting" by T. N. Reece & B. D. Lott from
Poultry Sci. Abstracts (1983). .
"Housing, Ventilation, Temperature as They Relate to Broiler
Performance" James W. Deaton from Poultry Digest, Nov.
1983..
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Primary Examiner: Tanner; Harry B.
Attorney, Agent or Firm: Jones, Tullar & Cooper
Claims
What is claimed is:
1. A method of controlling environmental conditions in an animal
enclosure having litter material on the floor thereof, to provide a
maximum economic return from the growth of animals housed therein,
said enclosure including a plurality of controllable ventilation
fans and a plurality of controllable heaters, comprising:
determining the static parameters of the animal enclosure including
size and thermal characteristics;
determining the number and type of animals to be housed in said
enclosure;
determining current values of variable parameters, including
current weight, heat production, air infiltration, prices of fuel,
feed, electricity, and market value of animals;
assessing qualitatively the relative moisture content of the animal
enclosure litter to determine whether the litter is too dry or too
wet;
establishing a target relative humidity value in response to said
qualitative assessment;
measuring the exterior air temperature near said enclosure to
establish a dew point temperature;
measuring the interior air temperature within said enclosure;
determining, from said measured exterior temperature, dew point
temperature, and target humidity, for each of a plurality of
feasible interior temperatures, the ventilation rate VT required to
maintain that feasible interior temperature, the ventilation rate
VH required to maintain air relative humidity at a control interval
value which will achieve a 24-hour average relative humidity at
said target value; the expected animal growth feed consumption and
operating costs at that temperature; and
selecting and maintaining the one of said feasible interior
temperatures which will produce the maximum economic return for the
animals in said enclosure.
2. The method of claim 1, further including operating enclosure
ventilating fans and heaters in accordance with the values
determined for the selected interior temperature, said system
operating to select the rate VH whenever VH is equal to or greater
than VT, and selecting the rate VT whenever VT exceeds VH.
3. The method of claim 2, further including the step of activating
a sufficient number of ventilating fans in said enclosure to attain
the selected ventilation rate.
4. The method of claim 3, further including activating said
ventilating fans in sequence.
5. The method of claim 2, further including the step of activating
a sufficient number of heaters to maintain the interior temperature
of said enclosure when VH exceeds VT.
6. The method of claim 2, further including the step of determining
a 24-hour average relative humidity value for air inside said
enclosure;
periodically comparing said target relative humidity to said
24-hour average relative humidity and determining the difference
therebetween; and
establishing said ventilation rate VH at a value which will produce
a very high relative humidity within said enclosure as long as the
current 24-hour running average relative humidity is less than said
target relative humidity.
7. The method of claim 2, wherein the steps of determining the
ventilation rates VT and VH for feasible temperatures and of
selecting one of said ventilation rates are repeated at regular
short control intervals.
8. The method of claim 7, wherein the qualitative assessment of the
relative moisture content of said litter and the establishment of a
target relative humidity value are performed periodically.
9. The method of claim 7, further including determining, from the
selected ventilation rate an anticipated interior air
temperature;
comparing the anticipated interior air temperature with said
measured interior air temperature to obtain a difference
temperature;
correcting individual fan delivery rates to reduce said difference
temperature; and
providing an alarm if said difference temperature exceeds a
predetermined value. .Iadd.
10. A method of controlling environmental conditions in an animal
enclosure to provide a maximum economic return from the growth of
animals housed therein, said enclosure including at least one
controllable ventilation fan and at least one controllable heater,
comprising:
determining the configuration and thermal characteristics of the
animal enclosure;
determining the number and type of animals to be housed in said
enclosure;
determining current values of variable parameters, including
current weight, heat production and market value of animals in said
enclosure, air infiltration into said enclosure, and prices of
fuel, electricity and feed;
determining, for each of a plurality of feasible interior
temperatures, a ventilation rate VT required to maintain that
feasible interior temperature which, when combined with the said
enclosure configuration, thermal characteristics and variable
parameters, will result in the maximum economic return;
selecting and maintaining the one of said feasible interior
temperatures which will produce the maximum economic return for
animals in said enclosure by operation of at least one of said
ventilation device and said heater, to effect the ventilation rate
VT, within said enclosure which will result in the maximum economic
return. .Iaddend. .Iadd.
11. The method of claim 10, further including: assessing
qualitatively the current conditions of variable parameters
including moisture conditions in the enclosure;
determining, for each of a plurality of feasible interior relative
humidities, a moisture ventilation rate VH required to maintain
that feasible interior relative humidity which, when combined with
the said enclosure configuration, thermal characteristics and
variable parameters, will result in the desired moisture conditions
within the enclosure; and
selecting and maintaining the one of said feasible interior
relative humidities which will produce the desired relative
moisture conditions for the animals in said enclosure by operation
to at least one of said ventilation device and said heater, to
produce the required moisture ventilation rate VH. .Iaddend.
.Iadd.12. Method of claim 11, further comprising:
assessing qualitatively a relative moisture condition of the
enclosure floor and any covering material within said animal
enclosure, to determine if said floor or covering material is too
dry or too wet;
establishing a target relative humidity value in response to said
qualitative assessment;
determining, for said target humidity, for each of a plurality of
feasible interior temperatures and for each of a plurality of
feasible interior relative humidities, the ventilation rate VT and
the moisture ventilation rate VH required to maintain that feasible
interior temperature and that feasible interior relative humidity
which, when combined with the said enclosure configuration, thermal
characteristics and variable parameters, will result in the maximum
economic return;
selecting and maintaining the one of said feasible interior
temperatures and the one of said feasible interior relative
humidities which will produce the maximum economic return for the
animals in said enclosure by operation of at least one of said
ventilation device and said heater, to effect the ventilation rate
VT and the moisture ventilation rate VH, within said enclosure
which will result in the maximum economic return. .Iadd.13. A
method of controlling environmental conditions in an animal
enclosure to provide a maximum economic return from the growth of
animals housed therein, said enclosure including at least one
controllable ventilation device, comprising:
determining the configuration and thermal characteristics of the
animal enclosure;
determining the number and type of animals to be housed in said
enclosure;
determining current values of variable parameters, including
current weight, heat production and market value of animals in said
enclosure, air infiltration into said enclosure, and prices of
electricity and feed;
determining, for each of a plurality of feasible interior
temperatures, a ventilation rate VT required to maintain that
feasible interior temperature which, when combined with the said
enclosure configuration, thermal characteristics and variable
parameters, will result in the maximum economic return;
selecting and maintaining the one of said feasible interior
temperatures which will produce the maximum economic return for
animals in said enclosure by selective operation of said
ventilation device, to effect the ventilation rate VT within said
enclosure which will result in the maximum economic return.
.Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates, in general, to control systems for
regulating the environment within animal growth houses, and in
particular to the control of humidity and temperature within
poultry houses for economic optimization of broiler chicken
production.
The production of broilers in the poultry industry involves a "grow
out" stage in which many thousands of young chicks are delivered to
a poultry house, where they are sheltered and provided with food
and water through a growth cycle of about six to eight weeks. At
present, about 5 billion birds are produced per year. The chicks
are not individually caged, but are massed in the poultry house by
the thousands. A typical poultry house is a steel-truss or wood
frame structure with seven foot high walls, a width of 40 to 50
feet, and a length of 300 to 600 feet. One or two curtain dividers,
or partitions, are usually provided along the length of the house
to divide the building into sections to restrict the access of the
birds since very young chicks do not require the entire floor
space. In addition, the building may be provided with large
openings along its length for natural ventilation, the opening
being provided with curtains to control air inflow and to maintain
heat in the winter. Alternately, the building may be totally
enclosed, and dependent on mechanical ventilation for substantially
all air exchange, in which case fans may be located at spaced
positions along the length of the house. A plurality of heaters are
normally provided for maintaining the temperature at a desired
level. The heaters may be spaced along the length of one wall,
preferably the wall opposite the fan location. Cooling is not
usually provided.
One section of the house is used as a brooder portion, and
incorporates either large brooder stoves within the house or
external heaters. Both are capable of maintaining a relatively high
temperature in the brooder section. An automatic feed system
supplies specified quantities of feed to the birds, and an
automatic watering system provides a regulated quantity of water to
the poultry house.
For the first three weeks of life, chicks are not able to control
their own body temperature, and thus are very susceptible to
changes in temperature within the poultry house. For this reason,
the brooder stoves or heaters in the brooding section are capable
of maintaining the temperature level constantly high, in the range
of 85.degree.-95.degree. F. When the chicks are small, most of the
poultry house can be closed off by the partitions, so that only a
small area, for example 25% of the total area, need be maintained
at this high temperature. However, after about 20 or 21 days, the
chicks begin to be able to regulate their own body temperature, and
the brooder section does not have to be maintained at this high
level. In many systems, the brooder stoves are simply turned off at
this time, and the temperature level within the house is maintained
by the body heat of the birds themselves. Occasionally,
supplemental heat must be added during cooler weather, and during
warmer weather the houses must be well ventilated to prevent
overheating, for chickens are susceptible to temperatures that are
too high. After about the 21st day one or both of the divider
partitions may be removed to allow access to the entire building.
The period prior to this time is usually referred to as the
brooding period; the following time is usually referred to as the
growout period.
In a poultry house, the entire floor normally is covered with a
"litter" material, usually wood shavings, which remains in place
for about a year before it is changed. During that time, the litter
accumulates a great deal of fecal matter, water, spilled feed, and
the like, so that its nature and consistency gradually changes over
that period of time. The condition of the litter directly affects
the quality of the air in the poultry house, and to a large extent
determines the air quality. Accordingly, bird health and
performance are directly related to the moisture level of the
litter in the house.
Chickens are extremely sensitive to dust, and if the litter becomes
too dry, respiratory problems such as bird air saculitis can affect
an entire flock. On the other hand, if the litter remains too
moist, it encourages the growth of harmful bacteria, incubating
diseases such as coccidiosis which is one of the most devastating
of the poultry diseases, and which can infect an entire flock. The
danger of such infection requires that medication (coccidiostats)
be added to the feed, in present poultry houses, and this
medication is very expensive. Thus, it is critical for the health
of the flock, and for the economic operation of the poultry house,
to maintain the moisture level in the litter at a healthful
level.
Since there is a continuous air flow through poultry houses, the
relative humidity level in the air is changeable, and depends to a
large extent on the temperatures inside and outside the house, but
also depends on the moisture level in the litter. An important
factor in determining the moisture level in the litter is the
relative humidity of the air, for the litter acts as a sponge to
absorb moisture from the air or to give moisture up to the air,
depending on their relative moisture conditions. Although
short-term variations in the air relative humidity may be produced
by controlling the air flow through the house, the long-term
moisture level in the poultry house litter changes relatively
slowly, so that changes in ventilation rates do not immediately
result in corresponding changes in litter condition. Instead,
litter changes occur over a several hour period.
Another factor affecting air quality in a poultry house is the
amount of ammonia produced by the litter. This varies with the
condition of the litter, and other factors, but must be taken into
account when controlling ventilation rates, for if the ammonia
level is too high, ventilation must be increased, even if it is at
the expense of desired humidity and temperature levels.
In prior control systems for poultry houses, it was recognized that
the humidity level and the air temperature were important for
maintaining the health of a flock. However, the prior art did not
fully comprehend the nature of the interaction between the heating
system, the humidity levels, and the operation of the ventilating
system and thus did not attempt to control them in such a way as to
maintain optimum conditions wherein the health of the poultry is
safeguarded, while at the same time, holding the energy and other
costs required to a minimum. For example, attempts to control the
temperature within a poultry house can adversely affect the control
of humidity, for the addition of heat to raise the air temperature
increases the moisture capacity of the air and tends to dry out the
litter. Similarly, increasing temperatures in warm weather of
unacceptable high ammonia levels can result in the operation of
ventilating fans, increasing the air flow and thereby drying out
the litter. Thus, the requirements for heating or ventilation may
conflict with the humidity level requirements within the poultry
house. These conflicting requirements make environmental control
very complex, and have precluded the effective control of litter
moisture on a continuous basis. Further, prior systems have not
provided a mechanism for obtaining environmental control in such a
way as to provide a maximum economical return from the poultry
house.
The operation of various heaters and ventilators in poultry houses
was, in the past, controlled manually by an operator who made
periodic measurements or subjective assessments of litter moisture
level and interior temperature levels, with the operator being
required to then experiment with the heating and ventilation
controls in an attempt to regulate the air quality on the basis of
those measurements or assessments. Since the relationships are
complex, and since the operator would only make periodic
measurements and adjustments, such manual systems led to wide, and
often harmful, fluctuations in temperature and humidity, and
presented an almost insurmountable problem even to experienced
operators, particularly during periods of extremely variable
weather, as often occurs in the spring and the fall. This
difficulty was compounded by the fact that accurate measurements of
litter moisture are extremely difficult to make, not only because
the conditions of the litter can vary widely over the length and
width of a poultry house, but because the measurements provided by
a limited number of available sensors will only provide an
indication of surface condition for a very small area, rather than
the actual condition of the litter as a whole. Thus, the use of
such sensors would often cause the operator to make control
determinations on the basis of inaccurate or incomplete data,
thereby causing incorrect operation of ventilating fans or heaters.
In addition, such sensors have the further disadvantage of being
quite costly.
More recently, attempts have been made to provide computerized
control of the poultry house environment, and extremely complex
control systems have been developed which attempt to take into
account all of the large number of variable conditions. However, in
reality such computerized systems essentially replicate the manual
control of a poultry environment, and for this reason have not been
satisfactory. A common feature of all such prior control systems is
that they operate on the basis of preselected criteria, such as
charts which provide specified values of air temperature and
relative humidity, and operate to those preselected values only.
Such systems cannot take into account the dynamic changes that
occur within a poultry house from day to day and are even less able
to take into account changes from hour to hour. These dynamic
changes include changes in litter type, variations in litter
conditions from the time of bird placement, changes in the birds
themselves both as to size and as to health, changes in feeding
patterns in response to air temperature, and changes in factors
such as outside air temperature and humidity. These prior art
systems do not provide for qualitative, continuous assessments of
existing inside and outside conditions, but simply operate in
accordance with preselected values.
It is essential that a poultry house be operated for maximum
economic return. The two principal factors in an economical
operation are: (1) the cost of maintaining the poultry house
environment and the associated bird performance, including the rate
of growth and feed consumption, all of which are extremely
temperature dependent; and (2) bird health. Optimal environment
control must be directed to both aspects. Systems which operate to
preselected conditions of air temperature and humidity cannot
operate economically at all times, but instead depend upon whether
the preselected values happen to be best for the particular poultry
house at the particular time, under the particular weather and
animal conditions. Sometimes the preselected values are correct;
most of the time they are wrong. Various studies have shown that
optimal economic conditions are dynamic and are house specific, and
cannot be specified by a fixed general management method. Yet the
existing systems are so complex, in attempting to incorporate all
of the various factors involved in environmental control, that an
operator can do little to correct the situation or compensate for
errors which produce an uneconomic operation.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a
simplified system for control of the environment within an animal
enclosure such as a poultry house.
It is a further object of the present invention to provide a system
for automatic control of the environment within a poultry house in
order to protect and enhance economic return.
It is a further object of the present invention to provide a
simplified system for automatic control of the environment within
an animal house and which is responsive to qualitative inputs to
adjust the system for the most economic operation under changing
conditions.
The present invention overcomes the complexities of prior art
environmental control systems and provides a system which produces
optimal economic return from the operation of a poultry house. The
invention is a simplified, dynamic system which responds not only
to fixed data such as the poultry house structural and mechanical
configuration, but to variable data such as the prices of fuel,
feed, and electricity, overhead and labor costs, and data from
temperature sensors. Most importantly, the system also responds to
dynamically changing data, which is supplied to the system by way
of a single input to allow the operator to provide a continuing,
qualitative control of the operation of the entire system.
The present system is simple to install, since it requires only a
minimum number of temperature sensors, and once fixed mechanical
data relating to static parameters of the particular poultry house
are entered into the control system, is simple to operate and is
highly responsive to control by the poultry house manager. The
system can be easily updated by the operator, or manager, for
optimum operation by entering into the control system current
economic information relating to the cost of fuel, feed and
electricity, the market value of the poultry at the end of the grow
out period (unit price per pound), the number of birds being
processed, their current weight, and the like. These variable input
data and the temperature inputs are used by the control system in
determining the temperature most to produce maximum net return for
the system. Finally, the operator can periodically inspect the
condition of the poultry house to assess the condition of the
litter, which continually changes, to provide a humidity control
input, which establishes an average daily target air relative
humidity within the house which will cause the litter to dry out,
if it is observed to be too wet, or will cause the litter to absorb
moisture, if it is too dry. The control system then operates the
various fans and heaters in the building to control the building
environment and to produce the temperature which will provide the
desired litter condition to protect bird health and obtain optimum
economic return. This operation is under the supervision and
control of the building manager or operator, thereby giving the
operator an important function in the overall success of the
poultry house management.
The present control system calculates two different ventilation
rates based on the fixed, variable, and dynamic data provided. One
rate (VH) determines the ventilation flow required to remove
moisture and thereafter to maintain a desired level of humidity in
the air within the poultry house. The other rate (VT) determines
the ventilation flow required to maintain a desired temperature.
The control system then operates to provide the maximum
ventilation, as determined by the largest of VH or VT, by turning
on the number of ventilating fans and heaters required to produce
an air temperature which will, over a period of time, produce and
maintain the desired moisture level in the litter.
The key to the present system is the fact that it does not rely on
sensors for measuring litter moisture, and does not attempt to
maintain the humidity in the atmosphere within the poultry house at
some arbitrary, preselected value. Instead, the present system is
based on the recognition that the air relative humidity directly
influences the litter condition, and that changes in litter
moisture occur relatively slowly. Because litter moisture and air
relative humidity are critical to the health and growth of the
birds, the system provides for an ongoing, active participation by
the operator, who periodically, as on a daily basis, assesses the
dynamically changing condition of the litter in the poultry house
and adjusts the operation of the system in accordance with his
judgement as to the quality of the litter. If the operator judges
the litter to be too wet, he simply adjusts the present system to
decrease the air relative humidity; similarly, if he judges the
litter to be too dry, he adjusts the system to increase the
relative humidity. This simple adjustment varies the operating
point of the automatic control system, which then functions at the
new target humidity conditions established by the operator to
balance the heating and ventilating of the poultry house for
maximum economy at this new setting. As a result, no humidity
sensors in the litter are required and a dynamic input to the
system is provided to enable the operator of the poultry house to
maximize the operation of the system for current conditions.
The air target humidity value set by the operator is a 24-hour
average value, so it only needs to be adjusted once a day, if at
all. Since the litter acts as a damper to any changes in relative
humidity in the air within the poultry house, the litter condition
will lag behind changes in the air relative humidity. Thus, if the
average air humidity for the immediately previous 24 hours is lower
than the air target value established by the operator, then air
flow through the poultry house is controlled by the ventilating
fans to increase the air relative humidity, while if the 24-hour
average is higher than the target value, the ventilation is
controlled to reduce the air relative humidity. The ventilation
rate is continuously adjusted to maintain the air relative humidity
at the target value, thereby gradually changing the litter moisture
level. As noted above, the ventilation rate is controlled by the
largest of VH or VT.
When the running average air relative humidity (RH) is below the
target air RH, the ventilation rate for moisture VH is calculated
using an air relative humidity value of 90 or 95% as the basis for
control. When the ventilation requirements for humidity VH exceed
the ventilation requirements for temperature VT, then VH controls,
and the running average air relative humidity will increase, since
the control relative humidity will be near saturation (90-95% RH).
However, high air relative humidity increases the likelihood that
VT will exceed VH, and as long as the ventilation required for
temperature control (VT) exceeds the ventilation required for
humidity control (VH), the running average for the air relative
humidity will decline. When the air temperature in the house drops,
as would normally occur at night, the ventilation required for
temperature control will be reduced, usually to a level where VH
exceeds VT. Then the VH requirements will control, and the 24-hour
running average air relative humidity will increase. VH
requirements will be based on a 90 or 95% relative humidity until
the 24-hour average RH reaches the operator selected target value.
At this point, VH requirements are calculated on the basis of the
target RH, instead of a saturation value, and since the target RH
and the 24-hour running RH are the same, the desired value will be
maintained. This operation is the key to maintaining a high quality
air environment in the poultry house. After determining the
required ventilation rate for either temperature or humidity
control, the system of the present invention activates a sufficient
number of the ventilating fans to obtain the desired air flow.
A feature of the present system is that the measurement of the
exterior temperature, together with an estimate of the dew point
temperature, makes it possible to predict with considerable
accuracy what the ventilation rate should be in order to maintain a
selected temperature within the poultry house over a selected
control period of time. This temperature may be optimized or
operator selected. By monitoring the actual change in interior
temperature during operation of the system and comparing it to the
temperature change that is predicted for a given ventilation rate,
the system is able to determine whether the selected fans should be
adjusted to compensate for changes in ambient conditions such as
changes in wind direction or velocity. Further, such a deviation
from predicted temperature can indicate mechanical deterioration in
the fans. In addition alarm indicators can be provided to indicate
problems such as broken or slipping drive belts in individual
fans.
It should be noted that the infiltration of air into the poultry
house is considered to be the first "ventilation fan", and the air
flow caused by such infiltration can be determined without wind
sensors, simply by measuring the interior and exterior
temperatures, as described above. Infiltration, which may be
controlled by shutter or curtain positions, is unpredictable,
because it depends upon wind direction as well as wind velocity.
Prior systems required complex measurements to determine
infiltration rates, as opposed to the present invention which
simply uses the differences between predicted and actual interior
temperatures to determine this value. This infiltration flow rate
is then used in the calculations required for determining the total
ventilation flow rates, thereby providing a more accurate and less
complicated system than was previously available.
In summary, the present invention provides a method and apparatus
for controlling environmental conditions in a poultry house to
provide maximum economic return. The method includes determining
the static parameters of the poultry house, including house
dimensions, thermal characteristics and other parameters relating
to the economics of operating the building. A determination is then
made of the number of birds to be placed in the poultry house and
the portion of the poultry house which is to be used. Continuous
measurements are made of the current outside and inside
temperatures, and periodic assessments are made of the relative
litter moisture, as to whether it is too dry or too wet. This
qualitative assessment is made by an operator, who then decides
whether the relative humidity of the atmosphere within the poultry
house should be increased or decreased, and adjusts the target
24-hour running average for relative humidity of the air,
accordingly. The system then makes a quantitative determination of
the ventilation and heating requirements at all feasible inside
temperatures. For example, if the temperature outside the house is
90.degree., an inside temperature of 80.degree. is not feasible,
since there is no cooling provided in the poultry house.
Furthermore, since the brooding temperature is selected for the
first 21 days of a grow out period, the temperature selected by the
operator is the only feasible temperature during this time. The
system determines the ventilation and heating requirements for the
target relative humidity established by the operator at each
feasible, or achievable, temperature, for example in one degree
increments, and further determines a predicted bird growth rate and
feed requirement at each feasible temperature. After completion of
these calculations, the system then selects from the feasible
temperature values the value which is predicted to produce a
maximum net return to the operator for the next control interval.
This maximum net return is the value of the meat produced, less
feed costs, and less fuel and other operating costs. The system
then operates the heaters and the ventilating fans in such a way as
to obtain the selected optimum economic temperature at the target
humidity established by the operator. This will produce a relative
humidity in the building which will regulate the litter moisture
and will, at the same time, maximize the economic return from the
operation of the building, taking into account not only the health
and growth of the birds, but the use of fuel, feed, and the like.
Thus, the present system operates to optimize economic return while
at the same time providing an environment which will protect and
enhance bird health.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and additional objects, features and advantages of
the present invention will become apparent from the following
detailed description thereof, taken in conjunction with the
accompanying drawings in which:
FIG. 1 is a diagrammatic outline of a conventional poultry house
showing the control unit of the present invention;
FIG. 2 is a perspective front view of a controller constructed in
accordance with the present invention;
FIG. 3 is a perspective rear view of the controller of FIG. 2;
FIG. 4 is a schematic diagram of the system of the invention;
FIGS. 5 and 5B are charts showing variations of ventilation rates
over a typical 24-hour period for conventional control systems and
for the present invention, respectively, and FIG. 5C shows
variations in relative humidity over a 24-hour period; and
FIGS. 6-9 are flow diagrams for the control system of the
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Turning now to a consideration of FIG. 1, there is illustrated in
top plan view the floor plan of a poultry house 10 of conventional
type. As previously discussed, such a poultry house may be of any
desired construction, but typically includes side walls 12 which
may be about seven feet high, with appropriate insulation in the
walls and roof. A plurality of windows or ventilation openings (not
shown) may be provided around the perimeter of the building 10, the
windows preferably being located high on the side walls and
protected by overhanging eaves. The ventilation openings are either
manually or automatically controlled, using shutters or curtains to
control the flow of air into and out of the building.
Preferably, the building is divided into two sections by means of a
moveable partition generally indicated at 14, enabling the building
to be divided into sections generally indicated at 16 and 18, one
of which may be designated as a brooder area such as that generally
indicated at 18. The brooder area 18 is utilized during the first
20 or 21 days of the grow out period of chicks placed in the
poultry house 10, and includes one or more brooder stoves 20 or
other suitable heaters which are designed to maintain the
temperature. Such brooder stoves are necessary only in the brooding
area, which usually will be between about 25% and 50% of the floor
area of the house. A conventional feed system, diagrammatically
illustrated at 22, automatically controls the supply of feed to the
building 10, while a watering system, diagrammatically illustrated
at 24, provides water to the building in conventional manner.
In accordance with the present invention, a plurality of
ventilation fans, indicated at 30, 31 and 32 are mounted in one or
more side walls 12 of the building, and a plurality of heater units
34, 35 and 36 are mounted in an opposite side wall so that upon
operation of the fans, any heat provided by the heaters is drawn
across the width of the building to provide more uniform heating.
Although only three heaters and three ventilating fans are shown,
it will be understood that this is for purposes of illustrations
only, and that additional heaters and fans may be provided, as
required.
A control unit 40 is provided for the building, and incorporates a
suitable controller, such as a microprocessor 41 (FIG. 4) which
regulates the operation of the ventilating fans 30, 31 and 32 and
the heater units 34, 35 and 36 by way of control cables 42 and 44,
respectively. The control unit receives its operating power from a
suitable power supply 46, and also receives inputs from a plurality
of interior temperature sensors 47, 48 and 49 by way of cable 50
and from exterior temperature sensors 52 and 53 by way of cable 54.
Preferably, the interior temperature sensors are located in
corresponding partitioned segments of the building 10, while the
exterior temperature sensors are located at various locations
around the exterior of the building 10. Although three interior
sensors and two exterior sensors are shown, it will be understood
that additional sensors, or fewer sensors, may be used as required
to obtain accurate average readings of interior and exterior
temperature.
The control unit microprocessor 41 is adapted to regulate the
operation of the fans and heaters in response not only to the
interior and exterior temperature sensors, but in accordance with
specific data relating to the physical characteristics of the
poultry house 10, diagrammatically illustrated as static data 60,
and in accordance with economic data relating to the cost of fuel,
the market sale price of broiler chickens, and the like,
diagrammatically illustrated at block 62 as variable data.
One of the keys to the present invention, however, is the data
input to the control unit 40 provided by the input indicated at 64
as the target humidity. This data is provided by the operator or
manager of the poultry house on the basis of his subjective
assessment of the air quality in the house, and the condition of
the litter which covers the floor of the poultry house. This
litter, which is generally indicated at 70 in FIG. 1, consists of a
layer of wood shavings or other similar material placed on the
floor of the poultry house to protect the poultry and to absorb
moisture. Typically, the litter material is replaced once a year,
and during that year's time, its nature and consistency changes as
spilled feed, water, fecal droppings and the like accumulate. This
litter material initially may be quite dry and light, but it
gradually becomes matted and saturated with other material. The
quality of this litter material significantly affects the health
and thus the growth of chicks in the poultry house, and accordingly
its condition is a significant factor in the economic return
realized from the grow out of the chicks.
The economic return is the value of the meat produced from a flock
raised in the poultry house, less the associated costs of producing
the meat. These costs primarily include feed and fuel, as well as
electricity used for mechanical ventilation, lighting, and the
like. At warmer interior temperatures, the rate of growth is lower
because the birds do not eat as much, and less feed per unit of
growth is required because of a lower metabolic maintenance
requirement. However, more fuel is required to maintain the higher
temperatures. The opposite is true at cooler interior temperatures.
Thus, it is impossible to produce the biggest bird, use the least
amount of feed, and use the least amount of fuel, all concurrently.
The maximum economic return is a function of current costs, current
meat value, the thermal characteristics of the poultry house, the
current outside temperature, and the like. Whenever any of these
variables changes, the optimal inside temperature for maximum
economic return may also change, and the control unit 40 calculates
this optimal inside temperature from the data provided by inputs 60
and 62, as well as the data from input 64.
The control unit 40 is illustrated in FIGS. 2 and 3 as including a
housing 72 which may enclose a dedicated microprocessor or which
may simply provide connections to a conventional personal computer
such as an IBM PC-XT. The housing 72 includes on its front panel 74
an alphanumeric display panel 76 which may be used, for example,
for displaying data being supplied to the unit. Panel 74 also may
include a display 78 for showing the temperature inside the
building, and a display 80 for showing the temperature outside the
building 10. These temperature displays may represent an average
for the inside sensors 47, 48 and 49 and for the outside
temperature sensors 52 and 53, respectively, or, if desired,
selector switches may be provided to permit a display of each
sensor output individually. The temperature sensors are connected
by way of cables 50 and 54 to individual transducer inputs S1-S16
diagrammatically illustrated on the rear panel 82 of the control
unit housing 74 (FIG. 3) for connection to corresponding inputs to
the microprocessor 41 (FIG. 4). In similar manner, the heaters 34,
35 and 36 are connected by way of cable 44 to individual heater
control outputs H1-H16, also diagrammatically illustrated on the
rear panel 82. Finally, the ventilation fans 30, 31 and 32 are
connected by way of cable 42 to the control output connections
F1-F16, also on the rear panel 82. Again, the heater and
ventilation control output terminals are connected to appropriate
outputs on the microprocessor, whereby control signals to the
heaters and fans are provided to operate these units as required,
as illustrated in FIG. 4.
The control unit 40 includes an input connector 84 which permits
connection of a conventional computer input keyboard, generally
indicated at 85 in FIG. 4, to the microprocessor for entry of data.
If desired, two different keyboards may be provided, one for the
installer of the unit, who supplies static data relating to the
physical characteristics of the poultry house to a static data
house, who supplies to a variable data memory 87 the variable data
which relates to changeable conditions, such as the economic value
of the meat being produced, the cost of feed, and the like. In this
way, the microprocessor 41 can be provided, upon installation, with
static data which cannot be later changed by the operator or
manager of the poultry house, while the variable data which must be
periodically updated can be easily supplied by the operator as
needed.
The static data relating to the physical characteristics of the
house and the variable data relating to economic considerations may
alternately be entered by means of a keyboard provided on the front
panel 74 of the control unit 40; however, it is preferred that
separate keyboards of separate levels of access be provided for
security reasons. It will be noted that the alphanumeric read-out
on display 76 provides prompts to indicate what data is being
requested and will display the information entered for the user to
verify. Suitable identification codes and passwords may also be
provided for use in the entry of data.
An output terminal 88 may be provided for connection of a suitable
recorder 89 for permanent storage of statistical information or
other data, as may be required.
Apart from the variable data which may be supplied to the control
unit periodically, the control unit 40 includes only three
operator-adjustable inputs so that on a day-to-day basis, the
operation of the system is extremely simple. First, target
temperature data input 90, which is adjustable by a temperature
selector dial 91 is provided to permit the operator to establish a
fixed temperature selector is normally used to set a fixed
temperature only during the first 20 or 21 days of the grow out
period, when the birds are unable to maintain their own body
temperature. During that time, the operator may adjust the interior
temperature by means of the dial 91. However, at about the 20th or
21st day, the dial 91 normally is shifted to the "optimum"
position, which enables the microprocessor control unit to
automatically regulate the temperature in the poultry house in
accordance with the requirements established by a humidity selector
dial 92. This dial enables the operator to qualitatively assess the
condition of the litter within the poultry house and to establish
an increased or decreased target humidity level as required to
return the litter to the proper condition for the health and safety
of the poultry. Thus, the dial 92 permits establishment of the
target humidity data provided by input 64 (FIG. 1).
A third dial 94 provides an input to the control system to indicate
the percentage floor area of the poultry house currently in use,
and is adjusted by the operator as the birds grow and require
additional room.
Although the several selector inputs are shown as adjustable dials
or potentiometers, this is for purposes of illustration only. Such
inputs may be supplied to the microprocessor in any convenient way,
and in particular may be supplied by means of the keyboard 85 in
one preferred form of the invention.
The temperature sensors 47, 48, 49, 52 and 53 may be thermisters,
thermocouples or resistive-temperature detectors. They monitor the
temperature inside and outside the house 10 and are connected to
the microprocessor through appropriate signal conditioning circuits
(not shown) provided within the control unit 40 to produce input
voltages consistent with the requirements of the microprocessor.
Each temperature location preferably is monitored by two or more
sensors to provide system reliability.
The dials 91 and 92 provide the operator of the poultry house with
the ability to manually establish the desired inside temperature,
or, in the optimizing mode, to allow the microprocessor to
establish it, and further allow the operator to establish the
desired (target) average relative humidity for a 24-hour period.
The processor program utilizes these inputs in determining the
optimal operation of the ventilators and heaters.
The outputs provided by the control unit 40 may include digital
outputs on cable 95 which indicate when equipment is not operating
as desired and which activate an alarm 96, and statistical data by
way of output 88 on environmental conditions during the previous
24-hour period. The microprocessor may provide data on the average,
maximum and minimum temperatures inside and outside the house,
relative humidity, and the like, and may provide computed estimates
of fuel usage. The on/off control of the heating and ventilating
equipment is provided by digital outputs from the processor, with
16 outputs for each being provided, as shown on rear panel 82, to
permit control of up to 16 separate pieces of heating and 16 pieces
of ventilating equipment. These outputs control electromechanical
or solid state relays at the heaters and ventilators to turn the
equipment on or off for all or part of each control interval, such
relays being conventional and not shown in the drawings. Each
heater and ventilator is monitored on the basis of expected
performance. If it is determined that the operation of the poultry
house is not as expected, then error lights such as the alarm light
96 may be illuminated to indicate that a problem exists. If
desired, a plurality of alarm lamps may be provided, one for each
piece of equipment, with the appropriate lamp being illuminated to
indicate the anticipated source of the problem.
The microprocessor is programmed also to provide statistical data
on inside and outside temperature, average relative humidity, fuel
usage, and other environmental and economic parameters upon
request. Current data for the past 24 hours is available through
the alphanumeric display 76 and is accessed through the keyboard.
Daily statistical information as well as other performance data may
be stored for an entire growing period or may be transferred
periodically from the processor memory 86 to an external recording
device 88 by way of terminal 87.
The control unit is battery operated to insure continuous and
reliable operation, and is protected from the environment, which is
dusty, moist, and contains corrosive gas. Manual overrides are
provided for each heater and ventilator fan to permit manual
override of the control unit.
The selection of optimum inside environmental conditions for
maximizing economic return from the production of an animal such as
broiler chickens in a poultry house is affected by the market value
of the meat produced, the feed, fuel and electrical costs, the
production costs such as labor, capital equipment, and the like,
current outside weather conditions, the thermal characteristics of
the building, and the age of the birds. The relationship between
these factors may be expressed as follows: ##EQU1## where: net=net
return per bird, or $/bird
T=temperature dependent variable
t=time dependent variable
time=interval over which net is optimized; may be day, minute, or
hour
growth=rate of body weight gain, kg/day
$/kg of meat=unit price of meat (live weight basis)
feed=rate of feed consumption to support growth rate, kg/day
$/kg of feed=unit price of feed
fuel=rate of fuel use necessary to maintain house at specific
temperature, liters/day
$/liter of fuel=unit cost of fuel
electric=rate of electric use for fans and lights, kwh/day
$/kwh=unit cost of electricity
K=amount of fixed costs per unit time and bird associated with
production, including labor cost, capital cost for building and
equipment, in day.
Each of the products in this equation have units of dollars per
unit time per bird, and are time and temperature dependent; that
is, are dependent upon the specific day, or bird age, for a
specific inside air temperature. If this equation is divided by the
rate of growth per bird over the time increment being used (such as
the control interval of the microprocessor control) the units on
each variable will be expressed as dollars per kilogram, with no
time units, to thereby provide a common unit for purposes of
comparison.
Utilization of these relationships in simulations utilizing various
house types, a wide range of outside temperatures, and different
management schemes, clearly established that optimal conditions are
dynamic and cannot be specified by any fixed management method.
However, because the operation of a poultry house is extremely
temperature dependent, it has been the practice in the prior art to
establish rigid temperature schedules, based on operator experience
to be followed during the grow out period for the birds.
Accordingly, all prior systems have attempted to maintain a target
average temperature for a poultry house. However, the prior systems
provide no information as to how that target temperature should
change with economic factors that affect economic return. As a
result ventilation and heating requirements do not respond to
changing conditions, with the results illustrated in FIG. 5A. As
there shown, the ventilation requirements for humidity control
remain relatively constant, as indicated by curve VH, instead of
changing with variations in environmental conditions. As a result,
excessive heating is required, as indicated in the cross-hatched
areas between curves VH and VT, for heating is always required when
VH exceeds VT. Furthermore, in such systems the relative humidity
of the air within the poultry house can vary widely, causing
serious problems if the relative humidity allows the litter to
become either too wet or too dry over successive 24-hour
period.
Some attempts to overcome this latter problem have led to the
incorporation of humidity sensors in the poultry house in order to
monitor air relative humidity or to measure the moisture content of
the litter, in order to regulate the condition of the litter.
However, these measurements present a serious problem, for relative
humidity sensors are very expensive, and are adversely affected by
the atmosphere in a poultry house, while the effective moisture
level in a litter is very difficult to measure. Furthermore, if
changes are made in the type of litter used, or the type of feed
used, variations will occur in the litter, because different birds
respond to different feeds in a different way, and thus produce
different droppings, and all of these factors affect the condition
of the litter. The entire problem is further affected by the
ammonia content of the droppings for if the ammonia level is too
high, the operator may consider it necessary to provide additional
ventilation in the poultry house, even if it means reducing the
moisture content of the litter. Furthermore, the overall health of
the flock will also dictate the ventilation required, for if the
birds have lung problems, the operator may accept a higher ammonia
level in order to avoid drying out the litter and creating dust,
which might adversely affect the lung problem. Thus, the arbitrary
determination of temperature and humidity in prior art systems
cannot provide a proper environmental control for a poultry
house.
In operating the system of the present invention, the target
humidity is established by a qualitative assessment of the
condition of the litter and the dial 92 is adjusted to either
increase or decrease its moisture level. This establishes a target
relative humidity for the house. The system operates on a
predetermined control cycle, or interval of, for example, five or
ten minutes. At the beginning of each control interval the program
calculates a rate of ventilation VT which is required to maintain
the interior temperature at each of a plurality of temperature
increments between the maximum and minimum values which are safe
for the birds being grown out. The program also calculates for each
temperature increment the ventilation rate VH needed to control the
moisture level of the interior air so as to produce the 24-hour
average air relative humidity selected by input 64. The calculation
of VH is dependent on the outside air dew point, which is selected
for this purpose as being 2.degree. F. below the minimum measured
exterior temperature over the immediately preceding 24-hour period.
The microprocessor then determines which of the ventilation rates
VT or VH is the larger, and operates one or more of the fans 30, 31
and 32 to provide the required ventilation of the house. This
calculation is repeated at each control interval.
When the ventilation required for humidity control is greater than
that required for temperature control (VH is greater than VT) then
heat is required, as illustrated by the cross-hatched portions
between curves VH and VT in FIG. 5B. If the ventilation required
for temperature control (VT grater than VH), then supplemental
heating is not required, since more air is flowing through the
house to control temperature than is required to control
humidity.
The control unit processor 41 maintains a running average of
relative humidity, as shown in FIG. 5C, based upon the immediately
preceding 24-hour period. This 24-hour average is calculated on a
continual basis, and is used as the base for comparison with the
target value established by the operator. If the target is set at
70% RH, and the current 24-hour running average is 70%, the system
will maintain that relative air humidity, as long as the
ventilation rate is controlled by the value VH. Thus, for example,
in FIG. 5C the running average RH is shown to be 70% during the
time period of 6:00 A.M. to noon, during which period VH is greater
than VT (see FIG. 5B). After noon, however, the ventilation
requirements for temperature control (VT) exceed VH, as is
typically the case during daylight hours. When VT controls the
ventilation, the actual air relative humidity within the house
begins to decline (see FIG. 5C, house humidity), and as shown in
FIG. 5C, the 24-hour average falls below 70%. As soon as this
happens, the control target RH is set to exceed the 24-hour average
by the controller establishing a high control RH of 90-95%, which
will then control the calculation of VH. By using a high value for
the control RH, a minimum value for VH is established, and this
lengthens the time that VT remains greater than VH, as illustrated
by a comparison of FIGS. 5A and 5B. By extending the time of
control by VT from, for example 6:00 P.M. to about 9:00 P.M.,
heating is not required during that period, and heating
requirements are reduced from 9:00 P.M. till 3:00 A.M. compared to
those of prior art systems shown in FIG. 5A. This results in
significant fuel savings, as illustrated by the reduced
cross-hatched area in FIG. 5B.
As soon as ventilation control returns to the value VH; e.g. at
about 9:00 P.M. in the example illustrated in FIG. 5B, the heaters
are turned on, and the control relative humidity value remains at
95% until the house running average is brought back to the 24-hour
average target value, e.g. 70% at about 3:00 A.M.; then the control
interval target is reduced from 95% to 70% so that the 24-hour
average will remain at 70% (see FIG. 5C). This not only saves fuel,
but more importantly allows the litter to more quickly return to
the target moisture level, and makes it more likely that the
poultry house air quality will be maintained in a healthy
condition. This is only made possible through the use of the
optimizing control system of the present invention.
During minimal ventilation periods, as when outside temperatures
are cool, infiltration of air into the poultry house can provide a
significant part of the required air exchange rate. If infiltration
rates are not known, or are incorrect, the result can be over or
under ventilation, resulting in poor litter conditions and/or
excessive fuel usage. The present invention adjusts for this by
treating infiltration as a first stage of controlled ventilation.
Since the infiltration rate can change due to changes in the speed
or direction of the wind, this fact must be taken into account in
calculating ventilation rates. Similarly, the mechanical
ventilating fans deliver air flow against a pressure difference
which can change as the direction and velocity of the wind changes,
and this must also be taken into account by the system of the
present invention. Once the required ventilation rate is
established by the temperature or humidity parameters, the system
of the present invention calculates how many fans are necessary and
the length of time they should be on during the next control
interval to provide the required flow rate. The system also
determines the sequence in which the fans are selected so as to
extend the life of individual fans. When a group of fans is
activated, the temperature of the poultry house can quickly change,
resulting in a change in the number of fans operating and producing
cycling of fans on and off over successive control intervals. This
is not untypical in the control of poultry houses, and can cause
excessive wear in some fans. Accordingly, in the present system the
fans are sequenced si that all of them go through at least one on
cycle before the operation of a given fan is repeated.
The program carried out by the control unit 40 is generally
indicated in FIG. 6, with subroutines being illustrated in FIGS. 7,
8 and 9. As indicated in FIG. 6, when the program is started, an
indication must be made at block 100 whether the start up is for a
new flock, or for an existing flock being grown out. If it is not a
new flock, then as indicated in block 102, the data concerning the
flock will already be in the computer memory, so the program simply
recovers that data and goes on to block 104 of the program.
However, if this is the start up for a new flock of birds, then it
is necessary to initialize the data in the processor memory, as
indicated at block 106, by establishing the number of birds in the
flock, the strain, their age, and similar data. This is part of the
variable data 62 which is supplied to the system. When this is
done, the program then goes on to block 104, where it is determined
whether the birds are 21 days old or not. If they are less than 21
days, the program goes to the grow loop illustrated in FIG. 9, as
indicated at block 108.
The program loop of FIG. 9 maintains the house at specified
conditions, collects data on inside and outside temperature, and
keeps a 24-hour running average of selected variables. The loop
also monitors fan and sensor performance, and adjusts fan rates
based on feedback information. The loop starts by determining the
time of day, and if it is the beginning of a new day, the system
goes through a computation of statistics for the preceding data, as
illustrated in blocks 110 and 112. The program then reads the
current time, at block 114, and if the time indicates that it is
not the end of a predetermined control interval, such as a
10-minute interval, or any other arbitrary time period, the system
continues to monitor inside and outside temperatures for
determining running averages over the control interval, as
indicated at blocks 116 and 118. When the end of the control
interval is reached, the system proceeds to block 120, where it is
determined whether the current inside temperature is at the desired
value. When the chicks are less than 21 days old, the desired
temperature is that which has been set, for example, by dial 91 on
the control panel 74 of FIG. 2. If the temperature is not at the
desired value, then the system adjusts the operation of the fans
and/or heaters so as to reach the desired temperature, as indicated
at block 122.
When the temperature is near the desired value, or after adjustment
of the ventilating rate, the fans and heaters are tested, at block
124, against expected performance. This is done by comparing the
target inside temperature with the actual inside temperature to
determine whether the inside temperature is at the expected value.
The target temperature is based upon the known ventilating rates
for individual fans operating during the control interval, plus the
expected infiltration rate, on the measured outside temperature and
on the net heat balance of the house. If there has been any
significant deviation from the expected performance, this is
determined at block 126, and an alarm signal is established, at
block 128. If there is no malfunction, or after the warning has
been sent, the loop of FIG. 9 is complete, and the system returns
to the program illustrated in FIG. 6, where the next step is to
proceed to the grow out loop illustrated in FIG. 8, as shown at
block 130 in FIG. 6.
The grow out loop of FIG. 8 provides a program for growing birds at
either the selected or the optimized inside temperature, as
determined by dial 91, and if VT is greater than VH, at or below a
control target relative humidity, which may be at or above the
target 24-hour running average humidity, and which is set by dial
92. The program computes (or predicts) rate of growth, feed
consumed, electrical usage and fuel usage at the target inside
temperature and selected RH, and this data is transferred to the
memory for use by the main program. During the control interval,
the loop first determines solar radiation, conduction, and heat
loads for the ventilating system, as indicated at block 132, and
provides an estimate of both dew point and current bird weight, as
indicated at block 134, this estimate being based upon the age of
the flock, the feed consumed, and other historical parameters. From
these data, the sensible and latent heat load of the flock can be
calculated, at block 136, this value providing an indication of the
amount of moisture and sensible heat being given off by the birds.
Thereafter, at block 138, the ventilation rates for humidity (VH)
and temperature (VT) control are both calculated on the basis of
the heat and moisture loads. If the sensible heat load is such that
it is not possible to obtain the desired inside temperature, even
if all of the ventilating fans were operated, a warning alarm is
provided and maximum ventilation is employed.
At block 140, a determination is made as to whether the ventilation
rate VH for obtaining the desired humidity level is greater than
the ventilation rate VT required to obtain the desired temperature
level. If this is the case, then it will be necessary to provide
supplemental heat from the heaters, in order to maintain the
desired temperature level in the poultry house and a computation is
made at block 142 of the amount of supplemental heat required.
Thereafter, at block 144, a further computation is made of the
weight gain, feed use, fuel use, electricity use, and other flock
parameters required for determining the operation of the poultry
house, at an operator selected temperature. Upon completion of
these calculations, the grow out loop of FIG. 6 is complete, and
the system returns to the program of FIG. 6, block 104, which again
determines whether the current age of the flock is less than or
equal to 21 days. If it is still less, then the grow loop of FIG. 9
and the grow out loop of FIG. 8 are repeated until 21 days have
lapsed. Thereafter, the program proceeds to block 146 where a
determination is made as to whether the grow out of the flock has
been completed. This normally requires between 45 and 55 days,
depending on the desired market weight and on the house
temperatures over that period. If it has not finished, then the
program proceeds to block 148, where calculations are made to
optimize the operation of the system so as to find conditions that
will maximize the economic return. After the birds are 21 days old,
the temperature control dial is set at the "optimize" setting,
rather than at an operator selected temperature value.
The program loop of FIG. 7 is used to obtain optimal inside
conditions during the balance of the grow out period after the
first 21 days. This is done through a repetitive simulation at each
control interval of house and flock performance over an acceptable
range of temperatures which is established by the operator; for
example, 50.degree. F. to 80.degree. F. The simulations are based
on the current target relative humidity established by dial 92. The
program selects from the simulations the optimal inside
temperature, according to Eq. 1, as above, and then activates the
heating and ventilating equipment needed to achieve the optimal
temperature during the next following control interval. To
accomplish this, the program first determines the minimum allowed
(or feasible) inside temperature ti (e.g. 50.degree. F.) for the
poultry house, which is established by the data initially entered
into the control system. The program then proceeds to block 152,
where the grow out loop of FIG. 8 is followed, as explained above,
to provide computations for the ventilation rates required for
humidity and temperature control at the initial value of ti. The
program then determines whether the equipment is capable of
maintaining the house at this minimum initial temperature, and if
not, determines the lowest minimum temperature achievable (block
154) by the equipment. This becomes the lowest feasible
temperature, and is stored, with the resulting ventilation rates,
flock growth rates, feed consumption and operating costs, at block
156. The temperature ti is then incremented up by 1.degree. F., as
indicated at block 158. If the incremented interior temperature ti
is less than the predetermined maximum allowed temperature for the
poultry house (e.g. 80.degree. F.), the calculations from the grow
out loop of FIG. 8 are redone at block 152, and the cycle is
repeated. This is done through the entire permissible range of
temperatures, and all the ventilation conditions that are feasible
are stored with their resulting growth rates, feed consumption and
operating costs (all predicted values). At the completion of this
simulation for the entire temperature range, the program goes to
block 162, where the single set of conditions which produces a
maximum economic return is selected (see Eq. 1) and the
corresponding ventilation and heating rates are established for the
next control interval.
Based on the selected optimal temperature and associated
conditions, a new running average relative humidity is computed, as
affected by the actual RH which will occur during the next control
interval, and which may be at or below the control interval target
RH. This new running value is then used to determine an appropriate
RH control interval target for future control interval
calculations.
Upon completion of the foregoing calculations, the program loop of
FIG. 7 terminates, and the system goes to block 164 in FIG. 6,
which maintains the newly calculated conditions and collects data
from the various sensors for the next cycle. This collection of
data is carried out in accordance with the grow loop of FIG. 9,
discussed above. The monitoring of the inside and outside
temperature and comparison of measured temperature with calculated
temperature, in accordance with FIG. 9, is repeated at preselected
time intervals, and at each interval the operation of the system is
optimized for conditions that will maximize the economic return
from the poultry house. This continues until the grow out period
for the flock is complete, at which time the program of FIG. 6 goes
to block 166, causing the system to compute the results of the grow
out period, and thereafter the program terminates.
In accordance with the foregoing program, it is not necessary to
actively monitor the various fans and heaters, the conditions
within the poultry house being determined indirectly by measuring
the actual interior temperature and comparing it with the
calculated temperature under the fan and heater conditions
established by the controller. If the interior temperature does not
meet control system predictions, then it will be apparent to the
operator that there may be something wrong with one or more fans or
heaters.
The humidity level established by dial 92 affects the calculation
of the ventilation rate required for moisture control of the
litter, even though the humidity during any control interval may be
greatly different from the selected 24-hour target value. Both
relative humidity and temperature directly affect litter condition,
either to cause it to become more moist, or to cause it to dry out.
The control system constantly calculates the actual 24-hour average
relative humidity and then uses ventilation rates which will
maintain the 24-hour average at a value established by the house
manager on the basis of his qualitative assessment of the condition
of the litter, thereby allowing the operator to have a direct input
to the operation of the poultry house and to enable the system to
function in a much more effective way to protect the health of the
poultry. The ventilation rate which is established for purposes of
humidity control will dominate the operation of the system until
the ventilation rate required for actual temperature control is
larger. Thus, the method of the present invention provides a safer
and healthier environment for the poultry house, than was possible
with prior systems which operated from set temperature points and
used fixed minimum ventilation rates for moisture control.
Although the present invention has been set forth in terms of
preferred embodiments, it will be apparent to those of skill in the
art that variations and modifications may be made without departing
from the true spirit and scope thereof as set forth in the
following claims:
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