Note: Descriptions are shown in the official language in which they were submitted.
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PREDICTIVE FREE COOLING
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Application No. 15/405;249
filed
January 12, 2017. This application is related to Provisional Patent
Application Serial No.
62/277;883 filed January 12, 2016; U.S. Patent Application Serial No.
14/524,103, U.S.
Patent Application Serial No. 12/874,607 filed September 2, 2010; and U.S.
Provisional
Patent Application Serial No. 61/234,199 filed September 2, 2009; the
foregoing applications
are hereby incorporated by reference in their entireties as if fully set forth
herein.
BACKGROUND
[0002] Controlling the energy consumption of a building, and in particular the
energy
consumption of an HVAC system, has been achieved through a building automation
system
(BAS) having software executable algorithms that incorporate munerical
constant values
corresponding to equipment operating characteristics. FIG. 1 shows a BAS
interacting with
an HVAC system in which real-time operating conditions within the HVAC system
are sent
to the BAS while control settings are received.
[0003] The equipment of the HVAC system may include, but is not limited to,
chillers, pumps, condensers, boilers, air handlers, heaters, terminal units,
etc. The values
utilized by the BAS are typically programmed during installation of the HVAC
system and
set according to the local climate and ambient conditions. These values may be
changed
periodically by manually evaluating and re-programming the BAS for anticipated
changes in
the local climate and tenant comfort complaints.
[0004] HVAC systems in the past had been designed and installed without energy
efficiency in mind. With rising energy costs and more emphasis on protecting
the
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environment, customers are now looking to reduce energy consumption. Other
inventions
that deal with energy efficiency within HVAC systems take a long time to
implement, require
large upfront costs, require a large amount of hardware modifications to the
original BAS or
HVAC system, and require expertise for installation, maintenance, updates, and
even
customer usage. These conventional systems may require frequent updates and
repairs.
Customers often need extensive training to perform such updates and repairs
themselves.
Typically, these systems may also require unique modifications for each
different HVAC
system, which adds to the cost and complexity of each installation. Further,
conventional
BASs are generally resource limited in their ability with respect to
processing, exchanging
and computing data.
[0005] Free cooling is an economic method of using low external air
temperatures to
assist in chilling water, which can then be used for industrial process, or
air conditioning
systems in green data centers. When the ambient air temperature drops to a set
temperature, a
modulating valve allows all or part of the chilled water to by-pass an
existing chiller and run
through the free-cooling system, which uses less power and uses the lower
ambient air
temperature to cool the water in the system without compromising cooling
requirements.
[0006] Free cooling (water-side economizing) is an effective tool for reducing
overall
energy consumption in complex cooling systems. In practice, however, it can be
difficult to
implement effectively, and often involves guesswork in determining when to
turn on and off.
[0007] Due to lack of precise information, operators tend to avoid using free
cooling
to minimize the possibility of expending the extra energy consumed by suddenly
restarting
chillers. When free cooling is used, it is often inefficiently implemented and
fans are overrun
¨ again, due to lack of precise data.
DESCRIPTION OF THE DRAWING FIGURES
[0008] Preferred and alternative embodiments of the present invention are
described
in detail below with reference to the following drawings:
[0009] FIG. 1 is a schematic diagram of a building automation system
interacting
with an HVAC system without an external application according to a
conventional
environmental control system;
[0010] FIG. 2 is a schematic diagram of an environmental control system having
an
external application in communication with a building automation system to
control energy
consumption of an HVAC system according to an embodiment of the present
invention;
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[00111 FIG. 3 is a block logic diagram of the communications and operation of
the
environment control system of FIG. 2 according to an embodiment of the present
invention;
and
[0012] FIG. 4 is a block logic diagram of the communications and operation of
free-
cooling functionality in connection with the environment control system of
FIG. 3 according
to an embodiment of the present invention.
DETAILED DESCRIPTION
[0013] This patent application is intended to describe one or more embodiments
of
the present invention. It is to be understood that the use of absolute terms,
such as -must,"
"will," and the like, as well as specific quantities, is to be construed as
being applicable to
one or more of such embodiments, but not necessarily to all such embodiments.
As such,
embodiments of the invention may omit, or include a modification of, one or
more features or
functionalities described in the context of such absolute terms.
[0014] According to one or more embodiments, the combination of software or
computer-executable instructions with a computer-readable medium results in
the creation of
a machine or apparatus. Similarly, the execution of software or computer-
executable
instructions by a processing device results in the creation of a machine or
apparatus, which
may be distinguishable from the processing device, itself, according to an
embodiment.
[0015] Correspondingly, it is to be understood that a computer-readable medium
is
transformed by storing software or computer-executable instructions thereon.
Likewise, a
processing device is transformed in the course of executing software or
computer-executable
instructions. Additionally, it is to be understood that a first set of data
input to a processing
device during, or otherwise in association with, the execution of software or
computer-
executable instructions by the processing device is transformed into a second
set of data as a
consequence of such execution. This second data set may subsequently be
stored, displayed,
or otherwise communicated. Such transformation, alluded to in each of the
above examples,
may be a consequence of, or otherwise involve, the physical alteration of
portions of a
computer-readable medium. Such transformation, alluded to in each of the above
examples,
may also be a consequence of, or otherwise involve, the physical alteration
of, for example,
the states of registers and/or counters associated with a processing device
during execution of
software or computer-executable instructions by the processing device.
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[0016] As used herein, a process that is performed "automatically" may mean
that the
process is performed as a result of machine-executed instructions and does
not, other than the
establishment of user preferences, require manual effort.
[0017] In the following description, certain specific details are set forth in
order to
provide a thorough understanding of various embodiments of the invention.
However, one
skilled in the art will understand that the invention may be practiced without
these details. In
other instances, well-known structures associated with HVAC systems and
individual HVAC
components, building climate or environmental control systems, building
automation systems
(BASs) and various climate control or environmental control processes,
parameters, and
operations thereof have not necessarily been shown or described in detail to
avoid
unnecessarily obscuring descriptions of the embodiments of the invention.
[0018] An embodiment separates energy optimization computation from equipment
control functions by externally interacting with the BAS of an HVAC system. In
one
embodiment, an optimization module, such as an external application, is
located in a global
control device, but could be housed in another hardware device that includes
an internal
microprocessor. The external application communications with the BAS, which in
turn
communicates with the HVAC system. The external application runs software
subroutines or
modules that process real-time HVAC system data and then provides that data to
be read by
the BAS, which in turn provides instructions to direct various HVAC system
components to
new or desired set points (e.g., a new temperature setting for a region of the
building, a new
flow rate for a pump or fan, etc.). One particular embodiment of the external
application
includes a method for optimizing or at attempting to optimize the overall
energy efficiency of
the HVAC system by reading, processing and revising various parameters, data,
and set
points.
[0019] In one embodiment, the HVAC system may include chiller plant equipment
that is under the control of the BAS. Some of the BAS' responsibilities
include equipment
control functions: lead/lag changeover, equipment failure monitoring,
equipment startup,
equipment shutdown, alarms recognition and announcement, and failure
changeover
sequences of the chiller plant.
[0020] Free cooling can be used to save energy whenever the wet bulb
temperature on
the exterior of the chiller plant drops below the required chilled water set
point. Such energy
savings can be realized due to, for example, reduced dehumidification load for
ventilation air
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and increased efficiency of cooling towers. An embodiment provides predictive
free-cooling
functionality. Predictive free cooling allows the use of a weather forecast
(e.g., data received
over a network and/or manually input, describing predicted ambient air
temperatures over a
predetermined and/or selectable time interval and external to a structure to
be cooled) as an
input to determine if free cooling should be requested or automatically
implemented.
[0021] An embodiment incorporates weather forecast data that accurately
predicts
free-cooling availability based on outside air wet bulb threshold. When the
ambient outside
temperature is below the threshold for the minimum free-cooling window period,
and current
plant conditions permit free-cooling operation, an embodiment can inform an
operator that
free cooling is available. This process can also occur automatically, with an
embodiment
enabling and/or disabling free-cooling mode without operator intervention.
Predictive free
cooling is configurable, allowing for both the outside air wet bulb threshold
and the minimum
free-cooling window period to be adjusted based on a site's specific
requirements. An
embodiment may generate monthly reports that give insight into the free-
cooling hours
available, free-cooling hours activated, and free-cooling hours missed when
otherwise
available.
[0022] Predictive free cooling adds the ability to ensure that a window of
weather
availability is present; without it, only current conditions may be used. By
providing this
precise weather-condition data ahead of time, the possibility of inefficiently
expending
energy by shutting down and restarting chillers is minimized. In other words,
chillers may be
only shut down if ambient air-temperature conditions will, according to the
weather forecast,
persist long enough to create free-cooling energy savings exceeding the energy
required to
restart the chillers. This latter determination can typically be a function of
the specific
tonnage, flow rate, and/or current wet-bulb temperature set point
(collectively "free-cooling
window data") associated with the chillers in question.
[0023] The result is reduced overall energy consumption through increased use
of
free cooling and improved efficiency in system operations. By leveraging the
real-time
operating data in an embodiment, the system learns and improves over time,
allowing
operators to use free cooling more often, and at optimal efficiency.
100241 FIG. 1 is provided for purposes of clarity to illustrate an
environmental control
system 100 that includes interaction between a building automation system
(BAS) 102 and an
HVAC system 104. The system 100 does not include an external application, so
it is therefore
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consistent with existing or conventional environmental control systems. In
operation, real-
time operating conditions 106 within the HVAC system 104 are transmitted to
the BAS 102
and then control settings 108, also called set points, are controllably
transmitted from the
BAS 102 to the HVAC system 104. In this system, equipment control functions
and
optimization functions must be co-mingled in the BAS.
[0025] FIG. 2 shows an environmental control system 200 that includes
interaction
between a BAS 202 and an HVAC system 204 in which real-time operating data 206
within
the HVAC system 204 are transmitted to the BAS 202 as described above. The
real-time
operating data 206 may include equipment operating conditions such as, but not
limited to,
voltages, speeds, temperatures and pressures, hereinafter referred to as "real-
time operating
data". In addition, the environmental control system 200 includes an external
application 210
configured to communicate with the BAS 202 through a data communication
network (not
shown). In one embodiment, the interaction between the external application
210 and the
BAS 202 is accomplished with a logical interface that allows the external
application 210 to
interact remotely from the BAS 202 and optionally interact with other BASs.
The external
application 210 provides application data 214 to the BAS 202. The application
data 214 may
include operating parameters for the HVAC system 204, for example the
application data 214
may indicate which HVAC components should be currently running, at what
speeds, etc.
Direct (e.g., hardware level) control of HVAC equipment is provided by the BAS
202. The
application data 214 provided to the BAS 202 from the external application 210
may
preferably include data to vary equipment speeds and define new equipment set
points, but
additional data may also be provided.
[0026] The BAS 202 reads the real-time operating data 206 from the HVAC system
204. The external application 210 interacts with the BAS 202 to achieve energy
savings for
the HVAC system 204 by receiving equipment data 212 from the BAS 202 and then
processing the equipment data 212 using software algorithms that calculate or
otherwise
determine desired operating settings for the HVAC system 204. To achieve the
desired
operating settings, the application data 214 is sent from the external
application 210 to the
BAS 202, which in turn permits the BAS 202 to operate the HVAC system 204 in
accordance
with the application data 214 provided from the external application 210. By
way of example,
the BAS 202 operates the HVAC system 204 with controlling instructions 208. In
one
embodiment, the external application 210 includes a programmable
microprocessor unit.
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[0027] The external application 210 uses three types of data, the equipment
data 212,
the application data 214, and status data 215 when interacting with the BAS
202. The
equipment data 212 includes the real-time operating data 206 as originally
provided by the
HVAC system 204 and interpretively modified by the BAS 202. The equipment data
212
may take the form of data related to power consumption, equipment speed,
supply
temperatures, equipment set points, equipment faults, running statuses, etc.
The BAS 202
writes the equipment data 212 to the external application 210. The application
data 214
includes operating parameters processed by the external application 210 and
read by the BAS
202. The application data 214 may then be acted upon within desired
operational and/or
safety limits defined by the HVAC system 204. The application data 214 may
include
optimized set points, optimized speed set points, temperature set points, etc.
In a preferred
embodiment, the equipment data 212 is sent to the external application 210
while the
application data 214 is provided by the external application 210. The status
data 215 is
exchanged between the BAS 202 and the external application 210 so that each
has access to
the current status of the other. Existing BASs do not have the necessary
control logic or
computing power to perform like the external application 210, which includes
more complex
control logic and may require more computing power.
[0028] FIG. 3 shows a logic diagram of an environmental control system 300 for
a
building or other structure 400 (FIG. 4). The control system 300 includes a
BAS 302, and
HVAC system 304 and an external application 306.
[0029] The BAS 302 reads real-time operating data 322 from the HVAC system 304
and converts the data 322 into BAS input database 324. The BAS input database
324 is
directed to both a normal BAS control sequence 320 and equipment data 316,
which may
take the form of the equipment data described above.
[00301 The default BAS control sequence 320 is used to directly control the
HVAC
system 304 without the external application 306 or when the external
application 306 is in a
non-operational or non-communicative mode. The sequence 320 is the original
control logic
sequence that controlled the HVAC system 304 prior to integration of the
external application
306 with the BAS 302. Although the sequence 320 may operate the HVAC system
304 in a
stable manner, which may include, but is not limited to, a steady state
operating
configuration, it is appreciated that the sequence 320 may not optimize the
efficiency of the
HVAC system 304.
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[0031] The equipment data 316 is utilized by an equipment application control
sequence 318 of the external application 306 to process the equipment data 316
and
determine desired application settings 319. The desired application settings
319 are formatted
by the application formatting module 310 to become application data 314. The
application
formatting module 310 is triggered based on a signal or data received from an
external
application ready 312.
[0032] By way of example, the external application ready 312 (hereinafter the
ready
312) informs the application formatting module 310 whether the external
application 306
meets certain criteria such that the ready 312 may then allow the application
formatting
module 310 to format the desired application settings 319 to the application
data 314. The go-
ahead criteria for the ready may require that each of the following are met,
specifically that
(1) the external application is in an operational mode; (2) the external
application is in a
communications mode with the BAS 302; (3) the BAS is operational; and (4) the
BAS 302
expects to receive instructions from the external application 306 to operate.
[0033] If the ready 312 determines that the external application 306 is not
operational,
there is no communication with the BAS 302, or that the BAS 302 does not
require the
external application 306 to operate, then the ready 312 informs the
application formatting
module 310 to format the initialization data 311 to application data 314.
Thus, the ready 312
determines whether the external application 306 is operational through
internal status checks.
The ready 312 determines communication with the BAS 302 via the status data
315 and
rechecks this status periodically. The ready 312 determines that the BAS 302
requires the
external application 306 to operate via the status data 315, which includes a
signal from the
external application enable 308.
[00341 The initialization data 311 may include application settings for
operating the
HVAC system at a minimum stable level if the application data 314 is utilized
by the BAS.
The initialization data 311 may be utilized until the external application 306
is ready, until
communications between the external application 306 and the BAS 302 are
restored, until the
BAS 302 expects to receive the application data 314 from the external
application 306 to
operate, or any combination of the foregoing.
[00351 The BAS 302 receives the application data 314 from the external
application
306. A sequence selector 326 then determines which of the data sequences (the
application
data 314 or the normal BAS control sequence 320) to send to a BAS output data
structure
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328. The sequence selector 326 determines which of the data signals to send,
via the external
application enable 308. In one embodiment, the external application enable 308
includes an
operator defined enable point that permits the operator to manually trigger
the control system
300 to indicate that the BAS 302 will be using the external application 306 to
operate the
HVAC system 304.
[0036] If the external application enable 308 informs the sequence selector
326 that
the operator defined enable point is enabled, the communication with the
external application
306 is operational, and the external application 306 is ready to operate, then
the enable 308 it
will allow the sequence selector 326 to send the application data 314 to the
BAS output data
structure 328.
[0037.1 If the external application enable 308 determines that the operator
defined
enable point is disabled, the external application 306 is not operational,
there is no
communication with the external application 306, or some combination thereof,
then the
enable 308 informs the sequence selector 326 to send the normal BAS control
sequence 320
to the BAS output data structure 328 as contrasted to sending the application
data 314. The
BAS output data structure 328 may then convert the received data to control
instructions 330,
which are then received by the HVAC system 304.
[0038] Still referring to FIG. 3, one example of an environment control system
includes the external application 306 interacting with the BAS 302 to control
a chiller plant
(e.g., HVAC system 304). In the BAS 302, an external application enable value
within the
BAS 302 directs the external application enable 308 that there is a demand for
optimized
cooling within a building, therefore the enable value is set to TRUE. Next,
the external
application 306 is instructed that the application data 314 is needed from the
external
application 306 as processed by the application control sequence 318. The
application data
314 may then be processed by the sequence selector 326 and converted to data
received by
the BAS output data structure 328, which may then be transmitted to the
chiller plant 304 as
controlling instructions 330 intended to provide an improved optimization
sequence to
increase an overall operating efficiency of the chiller plant.
[0039] When the external application enable value is FALSE, this indicates to
the
external application 306 that the chiller plant 304 is set to be operated
under manual or BAS
control, which does not require the processed application data 314 from the
external
application 306. In such a configuration, the initialization data 311 or other
default data
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accessible by the sequence selector 326 may be processed and transmitted to
the BAS output
data structure 328, which in turn provides the controlling instructions 330 to
the chiller plant
304.
[0040] Once the chiller plant is operating at desired efficiency, which may be
checked
or otherwise verified using the external application, the external application
306 may analyze
and determine a required chiller operating parameter within the application
control sequence
318 and then transmit processed application data 314 to the BAS 302, which in
turn provides
controlling instructions 330 to operate the chiller to the desired efficiency
or another
efficiency as determined by the external application 306. Similarly, after
receiving the real-
time operating data 322 and converting the same to the equipment data 316, the
external
application 306 may determine a new chilled water temperature set point. The
external
application 306 sends the new chilled water temperature set point to the BAS
302 via the
application data 314. It is appreciated that the aforementioned data flow may
be utilized to
provide controlling instructions 330 to other components besides a chiller,
for example a
boiler, a fan, air handling units, variable air volume units, or any other
component of the
HVAC system.
[0041] In the event there is a loss of communication between the external
application
306 and the BAS 302, the BAS 302 may retain the last supplied application data
314 for a
desired period of time. After this desired period of time, the BAS 302 may
return to the
normal BAS control sequence 320 until communication is restored. After
communication has
been restored and after some additional period of time, the external
application 306 may
again be brought online to generate new application data 314. The BAS 302 may
be
configured to smoothly make the transition from the normal BAS control
sequence 320 to
utilizing the application data 314 in a gradual and efficient manner.
[0042] Referring now to FIG. 4, an embodiment includes a predictive free
cooling
module 402. The module 402 receives free-cooling window data and the location
of building
400 from the external application 306. Module 402 passes the location of
building 400 to a
weather forecast engine 404. Forecast engine 404 may be provided by a third-
party weather
service such as, for example, the NOAA. Forecast engine 404 returns a weather
forecast over
a predetermined period of time for the location of building 400.
Alternatively, the weather
forecast is provided by module 402, itself using weather sensors to which the
module is
interfaced.
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100431 Module 402 determines free-cooling window availability data based on
the
weather forecast received from engine 404 and the free-cooling window data. In
an
embodiment, the weather forecast form engine 404 provides a prediction of
drybulb
temperature (regular temperature), relative humidity, barometric pressure, and
wetbulb
temperature for a period into the future (e.g., between 24 hours to 72 hrs).
[0044] The free-cooling weather data may consist of, wetbulb temperature
threshold
(may be configurable by installation, typically between 32 F and 50 F),
drybulb
temperature threshold (may be configurable by installation, typically between
32 F and 50
F), free-cooling window (may be configurable by installation, typically
between 1-24 hrs).
[0045] Module 402 applies the free-cooling data such as wetbulb threshold (or
drybulb threshold; either or both may be used) and free-cooling window to the
predicted
weather data, determines if the predicted wetbulb temperature (or drybulb
threshold; either
one or both may be used in parallel) is below the associated threshold
temperature for a
period of consecutive time, if this amount of consecutive time meets or
exceeds the free-
cooling window period, then a "free-cooling window" is determined to be
available, if the
amount of consecutive time does not equal or exceed the free-cooling window
period, then a
"free-cooling window" is not determined to be available.
[0046] For example: wetbulb temperature threshold = 35 F, drybulb temperature
threshold = 40 F, free-cooling window period = 4hrs. if the predicted weather
data shows that
at 1:00am the wetbulb temperature will be 35.2 F and the drybulb temperature
will be 40.1 F
a "free-cooling window" is determined NOT to be available. Until, at 2:00am
the wetbulb
temperature will be 34.8 F and the drybulb temperature will be 38 F, the
wetbulb temperature
and the drybulb temperature remain below their respective thresholds till
7:32am, when the
wetbulb temperature will be 35.4 F and the drybulb temperature will be 40.3 F,
this period
exceeds the free-cooling window period of 4hrs, so a "free-cooling window" is
determined to
be available starting at 2:00am, ending at 7:32am.
[0047] Module 402 passes the free-cooling window availability data to the
external
application 306 and, if free-cooling conditions are met, can instruct the
external application to
switch chiller plant 304 to free-cooling mode in which the chillers are
disabled or brought to
a low-power state, and the cooling fluid (e.g., water) routed to conduits
exposed to ambient
temperatures. Upon the free-cooling window's closing, module 402 can further
instruct the
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external application 306 to switch chiller plant 304 out of free-cooling mode,
thereby
restarting the chillers.
[0048] The free-cooling window availability data may be displayed to a user
via a
webpage 406. This displayed data provided by module 402 may further include
information
describing the extent to which the chiller plant 304 has historically operated
in free-cooling
mode during identified free-cooling windows, as well as other performance
indicators, such
as time spent by the chiller plant in free-cooling mode, munber of available
free-cooling
windows in a predetermined historical time range, and average length of free-
cooling
windows.
[0049] This data is also displayed to the operator or customer through an
intuitive
dashboard view. The Dashboard displays:
100501 Free cooling Window availability status
100511 if Free Cooling Window is available, display "Free Cooling Available"
in
green
[0052] If Free Cooling Window is not available, display" Free Cooling Not
Available" in grey
100531 State weather data status
[0054] If file is stale (no forecast data for 24 hours. display "Free cooling
not
available, Weather forecast our of date"
[0055] If file is not state, display nothing.
[0056] Free cooling status
[0057] If Free Cooling Available = YES and Free Cooling Status = ON; display
"Free
cooling is on" in grey
[0058] If Free Cooling Available = YES and Free Cooling Status = OFF; display
"Free cooling is off' in red
[0059] If Free Cooling Available = NO and Free Cooling Status = OFF; display
"Free
cooling is off' in grey
[0060] If Free Cooling Available = NO and Free Cooling Status = YES; display
"Free
cooling is off' in red
[0061] Wet Bulb Temperature
[0062] Display wet bulb threshold (this will be a trended point)
[0063] Display current OAWB
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[0064] Free Cooling Window Duration
[0065] Required window is the minimum amount of time the forecast wet bulb
must
be below the threshold to have free cooling available
[0066] Display Required Minimum Window (this will be a trended point)
[0067] Display time remaining
[0068] If there is a current window, display the time remaining in the window
[0069] If there is not a current window, display "no current window"
[0070] If the weather data is stale, display "unknown"
[0071] if the current free cooling window is more than 72 in the future,
display "more
than 72 hours"
[0072] Free Cooling Window Availability
[0073] Current Window Began:
[0074] If there is an active free cooling window (irrespective of stale
weather data
status), display the window start date and time
[0075] If there not a current window (irrespective of stale weather data
status), display "no current window"
[0076] Next Window Available:
[0077] If weather data is stale, display "unknown"
[0078] If there is a free cooling window available in the next 72 hours (that
is not the
current window), display window start date and time
[0079] If the current free cooling window is more than 72 in the future,
display "more
than 72 hours"
[0080] In an embodiment, the external application 306 continually or
periodically
provides updated free-cooling window data to module 402. This information
provided by
external application 306 enables module 402 to calculate updated free-cooling
windows as
such information (e.g., required load) changes over time.
[0081] Additionally, and in an embodiment, the external application 306
continually
or periodically informs module 402 of whether chiller plant 304 is operating
in free-cooling
mode. This information provided by external application 306 enables module 402
to calculate
the extent to which chiller plant 304 effectively exploited all portions of
available free-
cooling windows.
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CA 03049884 2019-07-10
WO 2018/132770
PCT/US2018/013667
[0082] The various embodiments described above can be combined to provide
further
embodiments. All of the above U.S. patents, patent applications and
publications referred to
in this specification, as well as U.S. Patent No. 6,185,946, are incorporated
herein by
reference in their entireties. Aspects can be modified, if necessary, to
employ devices,
features, methods and concepts of the various patents, applications and
publications to
provide yet further embodiments.
[0083] While the preferred embodiment of the invention has been illustrated
and
described, as noted above, many changes can be made without departing from the
spirit and
scope of the invention. Accordingly, the scope of the invention is not limited
by the
disclosure of the preferred embodiment. Instead, the invention should be
determined entirely
by reference to the claims that follow.
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