U.S. patent application number 13/761603 was filed with the patent office on 2014-08-07 for method for operating an hvac system.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to William Jerome Burke, Yicheng Wen.
Application Number | 20140216704 13/761603 |
Document ID | / |
Family ID | 51258295 |
Filed Date | 2014-08-07 |
United States Patent
Application |
20140216704 |
Kind Code |
A1 |
Wen; Yicheng ; et
al. |
August 7, 2014 |
METHOD FOR OPERATING AN HVAC SYSTEM
Abstract
A method for operating an HVAC system is provided. The method
includes providing a model for an indoor temperature, y, of a
building, providing predicted future outdoor temperatures, and
calculating an activation time or an adjustment time interval for
the HVAC system utilizing at least the model for y and the
predicted future outdoor temperatures. Operation of the HVAC system
can be improved with the activation time or the adjustment time
interval.
Inventors: |
Wen; Yicheng; (Louisville,
KY) ; Burke; William Jerome; (Louisville,
KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
51258295 |
Appl. No.: |
13/761603 |
Filed: |
February 7, 2013 |
Current U.S.
Class: |
165/201 |
Current CPC
Class: |
F24F 11/62 20180101;
F24F 11/65 20180101; F24F 11/30 20180101; F24F 11/64 20180101 |
Class at
Publication: |
165/201 |
International
Class: |
F28F 27/00 20060101
F28F027/00 |
Claims
1. A method for operating an HVAC system, the HVAC system
configured for cooling air within a building, heating air within
the building, or both, the method comprising: providing a model for
an indoor temperature, y, of the building; providing predicted
future outdoor temperatures; calculating an adjustment time
interval for the HVAC system utilizing at least the model for y and
the predicted future outdoor temperatures.
2. The method of claim 1, wherein the adjustment time interval
corresponds to a period of time required for the HVAC system to
adjust the indoor temperature of the building from an initial
temperature, T.sub.0, to a final temperature, T.sub.f, wherein
T.sub.0 and T.sub.f are unequal.
3. The method of claim 2, further comprising: determining an
initial time, t.sub.0, at which the indoor temperature of the
building is T.sub.0 and a final time, t.sub.f, at which the indoor
temperature of the building is T.sub.f, the adjustment time
interval corresponding to the difference between t.sub.0 and
t.sub.f; and activating the HVAC system at t.sub.0 such the indoor
temperature of the building is T.sub.f at t.sub.f.
4. The method of claim 1, wherein the model for y comprises a
second order linear model.
5. The method of claim 4, wherein the model for y comprises
y.sub.k=a.sub.1y.sub.k-1+a.sub.2y.sub.k-2+b.sub.1v.sub.k-1+b.sub.2u.sub.k-
-1 where y.sub.k is an indoor temperature of the building at time
k, y.sub.k-1 is an indoor temperature of the building at time k-1,
y.sub.k-2 is an indoor temperature of the building at time k-2,
v.sub.k-1 is an outdoor temperature at time k-1, u.sub.k-1 is an
operating state of the HVAC system at time k-1, and a.sub.1,
a.sub.2, b.sub.1, and b.sub.2 are constants.
6. The method of claim 1, wherein said step of calculating
comprises calculating the adjustment time interval with the
following: y f = CA k x k 0 + i = 0 N - 1 CA N - i - 1 BU i
##EQU00006## where ##EQU00006.2## C = [ 1 0 ] , A = [ a 1 a 2 1 0 ]
, B = [ b 1 b 2 1 0 ] , x k 0 = [ y k 0 y k 0 - 1 ] , U i = [ v i u
i ] , ##EQU00006.3## and N=k.sub.f-k.sub.0 where k.sub.0 is an
initial time at which the indoor temperature of the building is an
initial temperature, y.sub.k.sub.0, and k.sub.f is a final time at
which the indoor temperature of the building is a final
temperature, y.sub.k.sub.f.
7. The method of claim 1, wherein said step of calculating
comprises calculating the adjustment time interval in order to
minimize energy consumption of the HVAC system.
8. The method of claim 7, wherein said step of calculating
comprises calculating the adjustment time interval with the
following: T .rarw. CA N x k 0 + i = 0 N - 1 ( CA N - i - 1 B ) 1 v
i ##EQU00007## k * .rarw. k f - 1 ##EQU00007.2## while T < T f
do ##EQU00007.3## T .rarw. T + ( CA k f - k * B ) 2 ##EQU00007.4##
k * .rarw. k * - 1 ##EQU00007.5## end while ##EQU00007.6## where T
is the indoor temperature of the building and k* is a time
value.
9. The method of claim 1, wherein said step of providing predicted
future outdoor temperatures comprises determining predicted future
outdoor temperatures based upon weather forecast data.
10. The method of claim 9, wherein said step of providing predicted
future outdoor temperatures comprises providing predicted future
outdoor temperatures using the following: f ( t ) = { T max ( k ) +
T min ( k ) 2 - T max ( k ) - T min ( k ) 2 cos ( .pi. ( t - t min
( k ) ) t max ( k ) - t min ( k ) ) t .di-elect cons. [ t min ( k )
, t max ( k ) ) T max ( k ) + T min ( k + 1 ) 2 + T max ( k ) - T
min ( k + 1 ) 2 cos ( .pi. ( t - t max ( k ) ) t min ( k + 1 ) - t
max ( k ) ) t .di-elect cons. [ t max ( k ) , t min ( k + 1 ) )
##EQU00008## where T.sub.max(k) is a maximum temperature on day k,
T.sub.min(k) is a minimum temperature on day k, t.sub.max(k) is a
time of day for T.sub.max(k), and t.sub.min(k) is a time of day for
T.sub.min(k).
11. A method for operating an HVAC system, the HVAC system
configured for cooling air within a building, heating air within
the building, or both, the method comprising: providing a model for
an interior temperature, y, of the building; providing predicted
future exterior temperatures of the building; calculating an
activation time for the HVAC system utilizing at least the model
for y and the predicted future outdoor temperatures.
12. The method of claim 1, further comprising: turning on the HVAC
system at the activation time; and running the HVAC system in order
to adjust the indoor temperature of the building from an initial
temperature, T.sub.0, to a final temperature, T.sub.f, after said
step of turning on.
13. The method of claim 1, wherein the model for y comprises a
second order linear model.
14. The method of claim 13, wherein the model for y comprises
y.sub.k=a.sub.1y.sub.k-1+a.sub.2y.sub.k-2+b.sub.1v.sub.k-1+b.sub.2u.sub.k-
-1 where y.sub.k is an indoor temperature of the building at time
k, y.sub.k-1 is an indoor temperature of the building at time k-1,
y.sub.k-2 is an indoor temperature of the building at time k-2,
v.sub.k-1 is an outdoor temperature at time k-1, u.sub.k-1 is an
operating state of the HVAC system at time k-1, and a.sub.1,
a.sub.2, b.sub.1, and b.sub.2 are constants.
15. The method of claim 1, wherein said step of calculating
comprises calculating the activation time with the following: y f =
CA k x k 0 + i = 0 N - 1 CA N - i - 1 BU i ##EQU00009## where
##EQU00009.2## C = [ 1 0 ] , A = [ a 1 a 2 1 0 ] , B = [ b 1 b 2 1
0 ] , x k 0 = [ y k 0 y k 0 - 1 ] , U i = [ v i u i ] ,
##EQU00009.3## and N=k.sub.f-k.sub.0 where k.sub.0 is the
activation time at which the indoor temperature of the building is
an initial temperature, y.sub.k.sub.0, and k.sub.f is a final time
at which the indoor temperature of the building is a final
temperature, y.sub.k.sub.f.
16. The method of claim 1, wherein said step of calculating
comprises calculating the activation time in order to minimize
energy consumption of the HVAC system.
17. The method of claim 16, wherein said step of calculating
comprises calculating the activation time with the following: T
.rarw. CA N x k 0 + i = 0 N - 1 ( CA N - i - 1 B ) 1 v i
##EQU00010## k * .rarw. k f - 1 ##EQU00010.2## while T < T f do
##EQU00010.3## T .rarw. T + ( CA k f - k * B ) 2 ##EQU00010.4## k *
.rarw. k * - 1 ##EQU00010.5## end while ##EQU00010.6## where T is
the indoor temperature of the building and k* is the activation
time.
18. The method of claim 1, wherein said step of providing predicted
future outdoor temperatures comprises determining predicted future
outdoor temperatures based upon weather forecast data.
19. The method of claim 18, wherein said step of providing
predicted future outdoor temperatures comprises providing predicted
future outdoor temperatures using the following: f ( t ) = { T max
( k ) + T min ( k ) 2 - T max ( k ) - T min ( k ) 2 cos ( .pi. ( t
- t min ( k ) ) t max ( k ) - t min ( k ) ) t .di-elect cons. [ t
min ( k ) , t max ( k ) ) T max ( k ) + T min ( k + 1 ) 2 + T max (
k ) - T min ( k + 1 ) 2 cos ( .pi. ( t - t max ( k ) ) t min ( k +
1 ) - t max ( k ) ) t .di-elect cons. [ t max ( k ) , t min ( k + 1
) ) ##EQU00011## where T.sub.max(k) is a maximum temperature on day
k, T.sub.min(k) is a minimum temperature on day k, t.sub.max(k) is
a time of day for T.sub.max(k), and t.sub.min(k) is a time of day
for T.sub.min(k).
Description
FIELD OF THE INVENTION
[0001] The present subject matter relates generally to HVAC
systems, such as residential or commercial HVAC systems, and
methods for operating the same.
BACKGROUND OF THE INVENTION
[0002] Commercial and residential buildings or structures are
commonly equipped with systems for regulating the temperature of
air within the building for purposes of e.g., comfort, protection
of temperature sensitive contents, etc. Sometimes referred to as
heating, ventilating, and air conditioning or HVAC systems, such
systems typically include one or more components for changing the
temperature of air (i.e. air treatment components as used herein)
along with one or more components for causing movement of air (i.e.
blowers as used herein). For example, a refrigerant based heat pump
may be provided for heating or cooling air. Alternatively, or in
addition thereto, electrically resistant heat strips and/or gas
burners may be provided for heating air. One or more blowers or
fans may be provided for causing the heated or cooled air to
circulate within the building in an effort to treat all or some
controlled portion of air in the building. Ducting and vents may be
used to help distribute and return air from different rooms or
zones within the building.
[0003] During heating and/or cooling of air, HVAC systems consume
energy. In particular, HVAC systems' energy consumption can account
for more than fifty percent of a building's total energy
consumption. Despite consuming large amounts of energy, HVAC
systems are generally set to a specific operating temperature, and
the HVAC systems operate to maintain an associated building at the
specific operating temperature.
[0004] Certain HVAC systems also include features for switching the
specific operating temperature between a high set temperature and a
low set temperature to conserve energy. In particular, such HVAC
systems can be programmed to switch between the high set
temperature and the low set temperature at specific times. However,
switching between the high and low set temperatures can create
certain problems. In particular, HVAC systems require a certain
amount of time to heat and or cool the building. Thus, the
associated building's temperature can lag behind the specific
operating temperature of the HVAC system, and such temperature lag
can be uncomfortable or unpleasant to occupants of the associated
building.
[0005] Accordingly, methods for operating HVAC systems that can
account for temperature lags between various operating temperatures
of the HVAC system would be useful. In particular, methods for
operating HVAC systems that that can preheat and/or precool an
associated building in order to account for temperature lags
between various operating temperatures of the HVAC system would be
useful.
BRIEF DESCRIPTION OF THE INVENTION
[0006] The present subject matter provides a method for operating
an HVAC system. The method includes providing a model for an indoor
temperature, y, of a building, providing predicted future outdoor
temperatures, and calculating an activation time or an adjustment
time interval for the HVAC system utilizing at least the model for
y and the predicted future outdoor temperatures. Operation of the
HVAC system can be improved with the activation time or the
adjustment time interval. Additional aspects and advantages of the
invention will be set forth in part in the following description,
or may be apparent from the description, or may be learned through
practice of the invention.
[0007] In a first exemplary embodiment, a method for operating an
HVAC system is provided. The HVAC system is configured for cooling
air within a building, heating air within the building, or both.
The method includes providing a model for an indoor temperature, y,
of the building, providing predicted future outdoor temperatures,
and calculating an adjustment time interval for the HVAC system
utilizing at least the model for y and the predicted future outdoor
temperatures.
[0008] In a second exemplary embodiment, a method for operating an
HVAC system is provided. The HVAC system is configured for cooling
air within a building, heating air within the building, or both.
The method includes providing a model for an interior temperature,
y, of the building, providing predicted future exterior
temperatures of the building, calculating an activation time for
the HVAC system utilizing at least the model for y and the
predicted future outdoor temperatures.
[0009] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following description and appended claims. The accompanying
drawings, which are incorporated in and constitute a part of this
specification, illustrate embodiments of the invention and,
together with the description, serve to explain the principles of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A full and enabling disclosure of the present invention,
including the best mode thereof, directed to one of ordinary skill
in the art, is set forth in the specification, which makes
reference to the appended figures.
[0011] FIG. 1 provides a schematic representation of an exemplary
building as may be used with the present subject matter.
[0012] FIG. 2 illustrates a method for operating an HVAC system
according to an exemplary embodiment of the present subject
matter.
[0013] FIG. 3 illustrates a method for operating an HVAC system
according to an additional exemplary embodiment of the present
subject matter.
DETAILED DESCRIPTION
[0014] Reference now will be made in detail to embodiments of the
invention, one or more examples of which are illustrated in the
drawings. Each example is provided by way of explanation of the
invention, not limitation of the invention. In fact, it will be
apparent to those skilled in the art that various modifications and
variations can be made in the present invention without departing
from the scope or spirit of the invention. For instance, features
illustrated or described as part of one embodiment can be used with
another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
[0015] FIG. 1 provides a schematic representation of an exemplary
building 100 as may be used with the present subject matter.
Building 100 includes an HVAC system 110. HVAC system 110 is
configured for providing heated air to building 100, providing
cooled air to building 100, or both. In particular, building 100
defines an inside or interior 102. Interior 102 of building 100 is
separated or segregated from an exterior or outside 104. HVAC
system 110 can heat and/or cool interior 102 of building 100.
[0016] As will be understood by those skilled in the art, HVAC
system 110 can be any suitable mechanism for heating and/or cooling
interior 102 of building 100. In the exemplary embodiment shown in
FIG. 1, HVAC system 110 includes an air treatment component 118 for
heating and/or cooling air and at least one blower 119 for
directing heated and/or cooled air into interior 102 of building
100, e.g., via a duct system within building 100. As an example,
air treatment component 118 can be a heat pump that provides for
both heating and cooling of the air circulated by blower 119 of
HVAC system 110. Alternatively, air treatment component 118 of HVAC
system 110 can be a heater based on e.g., one or more gas burners
or electric strips.
[0017] HVAC system 110 also includes a thermostat 112 for
controlling HVAC system 110 and measuring a temperature of interior
102. A user can set an operating temperature of HVAC system 110
with thermostat 112, and HVAC system 110 can operate to maintain
interior 102 of building 100 at the operating temperature. Further,
HVAC system 110 includes a temperature sensor 116, such as a
thermocouple or thermistor, for measuring a temperature of exterior
104 of building 100.
[0018] HVAC system 110 also includes a processing device or
controller 114, e.g., positioned within thermostat 112. Various
operational processes or methods for operating HVAC system 110 can
be programmed into controller 114. As used herein, "controller" may
include a memory and one or more microprocessors, CPUs or the like,
such as general or special purpose microprocessors operable to
execute programming instructions or micro-control code associated
with operation of HVAC system 110. The memory may represent random
access memory such as DRAM, or read only memory such as ROM or
FLASH. In one embodiment, the processor executes programming
instructions stored in memory. The memory may be a separate
component from the processor or may be included onboard within the
processor.
[0019] It should be understood that the shape and configuration of
building 100 shown in FIG. 1 is provided by way of example only.
Buildings having different shapes, configurations, different
numbers of rooms, hallways, etc.--both residential and
commercial--may be used with the present subject matter. Further,
the location of HVAC system 110 relative to building 100 is also
provided by way of example only.
[0020] As will be understood by those skilled in the art, HVAC
system 110 can operate to maintain building 100 at a first
operating temperature when building 100 is unoccupied. Conversely,
HVAC system 110 can operate to maintain building 100 at a second
operating temperature when building 100 is occupied. Controller 114
can adjust HVAC system 110 between the first and second operating
temperatures, e.g., in order to conserve energy and/or reduce
operating costs of HVAC system 110. However, the first operating
temperature can be uncomfortable, e.g., too hot or too cold, to
occupants of building 100 relative to the second operating
temperature.
[0021] HVAC system 110 requires time to heat and/or cool interior
102 of building 100 and adjust a temperature of interior 102. As
discussed in greater detail below, the present subject matter
provides methods for operating an HVAC system, such as HVAC system
110. Such methods can assist with improving performance of HVAC
system 110, e.g., during heating and/or cooling of interior 102 of
building 100 between the first and second operating
temperatures.
[0022] FIG. 2 illustrates a method 200 for operating an HVAC system
according to an exemplary embodiment of the present subject matter.
Method 200 can be used to operate any suitable HVAC system, such as
HVAC system 110 (FIG. 1). As an example, controller 114 of HVAC
system 110 can be programmed to implement method 200. Utilizing
method 200, an adjustment time interval for HVAC can be calculated.
The adjustment time interval can assist with improving operation of
HVAC system 110 as discussed in greater detail below.
[0023] At step 210, a model for an indoor temperature, y, of
building 100 is provided. The model for y can be programmed into
controller 114 such that controller 114 can calculate a predicted
future indoor temperature of building 100, e.g., a predicted future
temperature of interior 102. The model for y can utilize any
suitable input to calculate y. For example, y can be calculated
based at least in part upon a previous indoor temperature of
building 100, a previous outdoor temperature of building 100,
and/or a previous operational state of HVAC system 110, e.g.,
whether HVAC system 110 is on or off.
[0024] The model for y can be any suitable model for simulating or
modeling the heat dynamics of building 100. As an example, the
model for y can be a second order linear model, e.g., such that the
model for y is given as
y.sub.k=a.sub.1y.sub.k-1+a.sub.2y.sub.k-2+b.sub.1v.sub.k-1+b.sub.2u.sub.-
k-1
[0025] where [0026] y.sub.k is an indoor temperature of building
100 at time k, [0027] y.sub.k-1 is an indoor temperature of
building 100 at time k-1, [0028] y.sub.k-2 is an indoor temperature
of building 100 at time k-2, [0029] v.sub.k-1 is an outdoor
temperature at time k-1, [0030] u.sub.k-1 is an operating state of
HVAC system 110 at time k-1, and [0031] a.sub.1, a.sub.2, b.sub.1,
and b.sub.2 are constants. As will be understood by those skilled
in the art, the model for y provided above is a discrete-time
auto-regressive model with exogenous inputs, and constants a.sub.1,
a.sub.2, b.sub.1, and b.sub.2 can be determined utilizing recursive
least-square techniques or any other suitable technique. As an
example, controller 114 can receive indoor temperature measurements
from thermostat 112, outdoor temperature measurements from
temperature sensor 116, and operating states from HVAC system 110
over time and calculate constants a.sub.1, a.sub.2, b.sub.1, and
b.sub.2 in order to identify the model for y.
[0032] The model for y provided above can also be provided as a
state space model. Thus, the model for y can be given as
X.sub.k+1=AX.sub.k+BU.sub.k
[0033] where
X.sub.k=[y.sub.ky.sub.k-1].sup.T,
and
U.sub.k=[v.sub.ku.sub.k].sup.T.
As discussed above, the model for y can be any suitable model in
alternative exemplary embodiments. Thus, the model provided above
is not intended to limit the present subject matter in any aspect
and is provided by way of example only.
[0034] At step 220, predicted future outdoor temperatures are
provided. As an example, controller 114 can receive the predicted
future outdoor temperatures, e.g., predicted future temperatures of
exterior 104 of building 100, at step 220. The predicted future
outdoor temperatures can come from any suitable source. For
example, the predicted future outdoor temperatures can be based on
weather forecast data or historical weather data.
[0035] As an example, weather forecast data generally includes a
daily maximum temperature and a daily minimum temperature. Further,
outdoor temperatures generally have a sinusoidal shape between the
daily maximum temperature and the daily minimum temperature. Thus,
the predicted future outdoor temperatures can be provided using the
following:
f ( t ) = { T max ( k ) + T min ( k ) 2 - T max ( k ) - T min ( k )
2 cos ( .pi. ( t - t min ( k ) ) t max ( k ) - t min ( k ) ) t
.di-elect cons. [ t min ( k ) , t max ( k ) ) T max ( k ) + T min (
k + 1 ) 2 + T max ( k ) - T min ( k + 1 ) 2 cos ( .pi. ( t - t max
( k ) ) t min ( k + 1 ) - t max ( k ) ) t .di-elect cons. [ t max (
k ) , t min ( k + 1 ) ) ##EQU00001##
[0036] where [0037] T.sub.max(k) is a maximum temperature on day k,
[0038] T.sub.min(k) is a minimum temperature on day k, [0039]
t.sub.max(k) is a time of day for T.sub.max(k), and [0040]
t.sub.min(k) is a time of day for T.sub.min(k). Utilizing the above
formula, the predicted future outdoor temperatures can be provided
throughout the day despite only having the daily maximum
temperature and the daily minimum temperature from the weather
forecast data. As discussed above, the predicted future outdoor
temperatures can be determined in any suitable manner. Thus, the
formula provided above is provided by way of example only and is
not intended to limit the present subject matter.
[0041] At step 230, the adjustment time interval for HVAC system
110 is calculated. The adjustment time interval can correspond to a
period of time required for HVAC system 110 to adjust an indoor
temperature of building 100 from an initial temperature, T.sub.0,
to a final temperature, T.sub.f, where T.sub.0 and T.sub.f are
unequal. Thus, HVAC system 110 can heat and/or cool interior 102 of
building 100 between T.sub.0 and T.sub.f within the adjustment time
interval.
[0042] As an example, controller 114 can calculate the adjustment
time interval at step 230 utilizing at least the model for y of
step 210 and the predicted future outdoor temperatures of step 220.
In particular, controller 114 can calculate the adjustment time
interval with the following:
y f = CA k x k 0 + i = 0 N - 1 CA N - i - 1 BU i ##EQU00002## where
##EQU00002.2## C = [ 1 0 ] , A = [ a 1 a 2 1 0 ] , B = [ b 1 b 2 1
0 ] , x k 0 = [ y k 0 y k 0 - 1 ] , U i = [ v i u i ] ,
##EQU00002.3##
[0043] and
[0044] N=k.sub.f-k.sub.0 where k.sub.0 is an initial time at which
the indoor temperature of building 100 is an initial temperature,
y.sub.k.sub.0, and k.sub.f is a final time at which the indoor
temperature of building 100 is a final temperature,
y.sub.k.sub.f.
Further, utilizing the above process, the adjustment time interval
can be calculated in order to minimize energy consumption of HVAC
system 110. For example, the adjustment time interval can be
calculated with the following:
T .rarw. CA N x k 0 + i = 0 N - 1 ( CA N - i - 1 B ) 1 v i
##EQU00003## k * .rarw. k f - 1 ##EQU00003.2## while T < T f do
##EQU00003.3## T .rarw. T + ( CA k f - k * B ) 2 ##EQU00003.4## k *
.rarw. k * - 1 ##EQU00003.5## end while ##EQU00003.6##
[0045] where [0046] T is the indoor temperature of building 100 and
[0047] k* is a time value. With the adjustment time interval
calculated at step 230, operation of HVAC system 110 can be
improved. For example, controller 114 can determine an initial
time, k* or t.sub.0, at which the indoor temperature of building
100 is T.sub.0 and a final time, t.sub.f, at which the indoor
temperature of building 100 is T.sub.f. The adjustment time
interval can correspond to the difference between t.sub.0 and
t.sub.f. Controller 114 can also activate HVAC system 110 at
t.sub.0 such the indoor temperature of building 100 is T.sub.f at
t.sub.f. In such a manner, method 200 can assist with preheating
and/or precooling interior 102 of building 100.
[0048] As will be understood by those skilled in the art,
controller 114 can be programmed to adjust the operating
temperature of HVAC system 110 between T.sub.0 and T.sub.f. As an
example, HVAC system 110 can operate to maintain building 100 at
one of T.sub.0 or T.sub.f when building 100 is unoccupied.
Conversely, HVAC system 110 can operate to maintain building 100
the other of T.sub.0 and T.sub.f when building 100 is occupied.
Controller 114 can adjust HVAC system 110 between T.sub.0 and
T.sub.f, e.g., in order to conserve energy and/or reduce operating
costs of HVAC system 110.
[0049] With the activation time interval calculated at step 230,
controller 114 can operate HVAC system 110 to pre-heat and/or
pre-cool interior 102 of building 100 between T.sub.0 and T.sub.f.
Such pre-heating or pre-cooling can increase comfort of occupants
within building 100 and improve satisfaction of such occupants with
HVAC system 110. For example, before such occupants enter or return
to building 100, controller 114 can operate to adjust interior 102
of building 100 from T.sub.0 to T.sub.f such the building 100 is
pre-heated or pre-cooled and comfortable for such occupants.
[0050] FIG. 3 illustrates a method 300 for operating an HVAC system
according to an additional exemplary embodiment of the present
subject matter. Method 300 can be used to operate any suitable HVAC
system, such as HVAC system 110 (FIG. 1). As an example, controller
114 of HVAC system 110 can be programmed to implement method 300.
Utilizing method 300, an activation time for HVAC system 110 can be
calculated. The activation time can assist with improving operation
of HVAC system 110 as discussed in greater detail below.
[0051] Like in step 210 of method 200 (FIG. 2), a model for an
indoor temperature, y, of building 100 is provided at step 310. The
model for y provided in step 310 can be any suitable model for y,
such as the model for y discussed above in method 200. The model
for y can be programmed into controller 114 such that controller
114 can calculate a predicted future indoor temperature of building
100, e.g., a predicted future temperature of interior 102.
[0052] Like in step 220 of method 200 (FIG. 2), predicted future
outdoor temperatures are provided at step 320. The predicted future
outdoor temperatures can come from any suitable source, such as
described above in method 200. As an example, controller 114 can
receive the predicted future outdoor temperatures, e.g., predicted
future temperatures of exterior 104 of building 100, at step
320.
[0053] At step 330, the activation time for HVAC system 110 is
calculated. The activation time can correspond to a time at which
HVAC system 110 is activated in order to adjust an indoor
temperature of building 100 from an initial temperature, T.sub.0,
to a final temperature, T.sub.f, where T.sub.0 and T.sub.f are
unequal. Thus, HVAC system 110 can heat and/or cool interior 102 of
building 100 between T.sub.0 and T.sub.f by activating HVAC system
110 at the activation time.
[0054] As an example, controller 114 can calculate the activation
time at step 330 utilizing at least the model for y of step 310 and
the predicted future outdoor temperatures of step 320. In
particular, controller 114 can calculate the activation time with
the following:
y f = CA k x k 0 + i = 0 N - 1 CA N - i - 1 BU i ##EQU00004## where
##EQU00004.2## C = [ 1 0 ] , A = [ a 1 a 2 1 0 ] , B = [ b 1 b 2 1
0 ] , x k 0 = [ y k 0 y k 0 - 1 ] , U i = [ v i u i ] ,
##EQU00004.3##
[0055] and
[0056] N=k.sub.f-k.sub.0 where k.sub.0 is the activation time at
which the indoor temperature of building 100 is an initial
temperature, y.sub.k.sub.0, and k.sub.f is a final time at which
the indoor temperature of building 100 is a final temperature,
y.sub.k.sub.f.
Further, utilizing the above process, the activation time can be
calculated in order to minimize energy consumption of HVAC system
110. For example, the activation time can be calculated with the
following:
T .rarw. CA N x k 0 + i = 0 N - 1 ( CA N - i - 1 B ) 1 v i
##EQU00005## k * .rarw. k f - 1 ##EQU00005.2## while T < T f do
##EQU00005.3## T .rarw. T + ( CA k f - k * B ) 2 ##EQU00005.4## k *
.rarw. k * - 1 ##EQU00005.5## end while ##EQU00005.6##
[0057] where [0058] T is the indoor temperature of building 100 and
[0059] k* is the activation time. With the activation time
calculated at step 330, operation of HVAC system 110 can be
improved. For example, controller 114 can activate or turn on HVAC
system 110 at the activation time such the indoor temperature of
building 100 is T.sub.f at a final time, t.sub.f. In such a manner,
method 300 can assist with preheating and/or precooling interior
102 of building 100, e.g., in a similar manner as described above
for method 200.
[0060] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they include structural elements that do not
differ from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
* * * * *