U.S. patent application number 11/801143 was filed with the patent office on 2008-11-13 for hvac control system and method.
This patent application is currently assigned to Johnson Controls Technology Company. Invention is credited to Anderlyne M. Canada, John E. Seem.
Application Number | 20080277486 11/801143 |
Document ID | / |
Family ID | 39968636 |
Filed Date | 2008-11-13 |
United States Patent
Application |
20080277486 |
Kind Code |
A1 |
Seem; John E. ; et
al. |
November 13, 2008 |
HVAC control system and method
Abstract
An HVAC control system configured to control the environment of
a building zone includes a means for determining a number of people
occupying the building zone and a means for determining properties
of other heat transferring objects located within the building
zone. The HVAC control system may also include a controller, the
controller being configured to compute a projected heat gain in a
building zone based on the determined number of people occupying
the building zone and the determined properties of the other heat
transferring objects located within the building zone. The
controller may use the computed projected heat gain to determine a
zone ventilation setpoint for the building zone.
Inventors: |
Seem; John E.; (Glendale,
WI) ; Canada; Anderlyne M.; (Milwaukee, WI) |
Correspondence
Address: |
FOLEY & LARDNER LLP
777 EAST WISCONSIN AVENUE
MILWAUKEE
WI
53202-5306
US
|
Assignee: |
Johnson Controls Technology
Company
|
Family ID: |
39968636 |
Appl. No.: |
11/801143 |
Filed: |
May 9, 2007 |
Current U.S.
Class: |
236/49.3 |
Current CPC
Class: |
F24F 2120/10 20180101;
F24F 11/30 20180101; G05D 23/1905 20130101; H04L 67/125 20130101;
H04L 67/12 20130101 |
Class at
Publication: |
236/49.3 |
International
Class: |
F24F 7/00 20060101
F24F007/00 |
Claims
1. An HVAC control system configured to control the environment of
a building zone, comprising: means for determining a number of
people occupying the building zone; means for determining
properties of other heat transferring objects located within the
building zone; and a controller, the controller being configured to
compute a projected heat gain in a building zone based on the
determined number of people occupying the building zone and the
determined properties of the other heat transferring objects
located within the building zone; wherein the controller uses the
computed projected heat gain to determine a zone ventilation
setpoint for the building zone.
2. The system of claim 1, wherein the zone ventilation setpoint is
a volumetric flow rate of air, and wherein the zone ventilation
setpoint is used to adjust at least one zone ventilation device
capable of affecting the volumetric flow rate of air provided to a
building zone.
3. The system of claim 1, wherein the controller includes a
feedforward control having inputs of the determined number of
people and the determined properties of other heat transferring
objects.
4. The system of claim 1, wherein the projected heat gain is a
projected convective heat gain to the building zone.
5. The system of claim 1, wherein the means for determining the
number of people occupying the building zone includes a radio
frequency receiver.
6. The system of claim 1, wherein the means for determining
properties of other heat transferring objects located within the
building zone includes a wireless sensor.
7. The system of claim 1, wherein the other heat transferring
objects of the building zone include heat transferring lights of
the building zone.
8. The system of claim 7, wherein the means for determining
properties of other heat transferring objects located within the
building zone includes a circuit configured to determine a lighting
property of the zone.
9. The system of claim 1, wherein the controller is further
configured to learn the heating characteristics of the zone; and
wherein the HVAC control system uses the learned heating
characteristics of the zone and the determined number of people to
compute the projected heat gain to the zone based on people and
objects.
10. The system of claim 1, wherein the controller is configured to
compute the projected heat gains of a zone based on determined
properties of people, computers, and lights of the zone.
11. The system of claim 1, wherein the controller is configured to
identify at least one person within the zone, and wherein the
controller determines a preferred temperature for the identified at
least one person within the zone.
12. The system of claim 11, wherein the controller is further
configured to identify at least two people located within the
building zone in order to determine the zone ventilation setpoint
for the building zone using the preferred temperature of the at
least two people.
13. The system of claim 12, wherein the ventilation setpoint is
determined by averaging the determined preferred temperature of the
at least two people in the zone.
14. The system of claim 12, wherein the means for determining a
number of people occupying the building zone includes an RFID
sensor configured to identify RFID devices carried by people.
15. The system of claim 14, wherein the controller retrieves an
identified person's preferred temperature from a database of
preferred temperatures communicably coupled to the controller, and
wherein the person's preferred temperature may be set via a
web-based interface.
16. A method of providing HVAC control to a zone using an HVAC
control system, comprising: determining a desired volumetric flow
rate, comprising: computing a projected convective heat gain to the
zone from people and other heat transferring objects located within
the building zone, and considering at least one air property;
selecting a volumetric flow rate setpoint; sending the selected
volumetric flow rate setpoint to a zone ventilation device.
17. The method of claim 16, further comprising determining the
number of people occupying the zone; and determining a lower limit
of supply airflow based on the number of people occupying the
zone.
18. The method of claim 16, further comprising: identifying at
least one person occupying the zone; determining a preferred
temperature for the identified at least one person occupying the
zone; and using the determined preferred temperature of the at
least one person occupying the zone to partially determine the zone
ventilation setpoint for the building zone.
19. The method of claim 16, further comprising: identifying at
least two people occupying the building zone using RFID sensors
configured to identify RFID devices carried by people; determining
the preferred temperature for the at least two identified people
occupying the building zone and using a database of preferred
temperatures associated with people; averaging the determined
preferred temperatures of the at least two people; and using the
average to compute a zone ventilation setpoint.
20. The method of claim 16, further comprising determining the
number of people occupying the zone using a wireless RFID sensor
configured to identify RFID devices carried by people.
21. The method of claim 20, further comprising determining the
activity level of the people occupying the zone using the wireless
RFID sensor; and using the determined activity level to compute the
projected convective heat gain to the zone from people.
22. The method of claim 16, further comprising: predicting the
convective heat gain to the zone from people and other heat
transferring objects located within the building zone based upon
schedule information of a scheduling database; and adjusting a
volumetric flow rate setpoint prior to a scheduled meeting
time.
23. A controller configured to control the environment of a
building zone, comprising: a data processor; a zone ventilation
device interface communicably coupled to the data processor, the
zone ventilation device interface being configured to route a
control signal to a zone ventilation device; and a sensor interface
communicably coupled to the data processor, the sensor interface
being configured to accept a signal from at least one sensor
located within the building zone; wherein the data processor is
configured to compute a projected convective heat gain to the
building zone from people and other heat transferring objects
located within the building zone based on a signal received from
the sensor interface; and wherein the data processor is configured
to send a control signal to the zone ventilation devices via the
zone ventilation device interface based at least partially on the
computed projected convective heat gain.
24. The controller of claim 23, further comprising a means for
determining a preferred temperature based on the people occupying
the building zone, wherein the determined preferred temperature is
considered by the processing means to determine the environment
setpoint.
25. The controller of claim 23, further comprising a communications
device configured to receive scheduling information from a
scheduling database, wherein the data processor is configured to
predict convective heat gain to the building zone based upon the
received scheduling information and to send a control signal to the
zone ventilation devices via the zone ventilation device interface
based on the predicted convective heat gain to the building
zone.
26. The controller of claim 25, wherein the controller causes the
zone ventilation devices to provide an increased level of
ventilation to the zone prior to a scheduled time of the scheduling
database.
27. The controller of claim 25, wherein the scheduling database is
the primary scheduling database used by the occupants of the
building zone and wherein the scheduling information is meeting
information.
Description
BACKGROUND
[0001] The present application relates generally to the field of
heating, ventilation, and air conditioning systems. More
specifically, the present application relates to control systems
and methods for heating, ventilation, and air conditioning
systems.
[0002] Building services systems are often employed in office
buildings, schools, manufacturing facilities, and the like, for
controlling the internal environment of the facility. Building
services systems may be employed to control temperature, air flow,
humidity, lighting, energy, boilers, chillers, power, security,
fluid flow, and similar building systems relating to the
environment of the building. Some building services systems are
specifically heating, ventilation, and/or air conditioning ("HVAC")
systems. HVAC systems commonly seek to provide thermal comfort,
acceptable air quality, ventilation, and controlled pressure
relationships to building zones. HVAC systems typically include an
HVAC control system and one or more ventilation devices such as air
handling units, variable air volume boxes.
[0003] An air handling unit is a device typically at the root of
commercial, industrial, and institutional HVAC systems. Air
handling units typically include a blower, one or more heating
and/or cooling elements, air filters, sound attenuators, and
dampers. Air handling units typically connect to ductwork that
distributes or supplies air throughout the building and returns the
air back to the air handling unit. An air handling unit may be
entirely enclosed by a single housing or frame, or it may be
located in a dispersed fashion include a variety of components in
contact with airflow. For example, an air handling unit may be
considered a primary unit having a blower as well as a remote unit
including a zone air handling unit and the unit's accompanying
circuitry (e.g., fan, flow sensor, etc.). Air handling units may
use one hundred percent outside air, one hundred percent
recirculated air, or some mix of outside air and recirculated air.
The blower of an air handling unit may operate at a single speed or
operate at a variety of speeds to allow or control a variety of air
flow rates. If an air handling unit is used to supply heat, the air
handler may contain or be used with a fuel-burning heater,
electrical heater, coils that are heated using circulated water or
steam with the heat provided by a boiler, or any other heat
creating apparatus. If an air handling unit is used for cooling,
the unit may contain or be used with a refrigeration evaporator,
water evaporator, coils cooled by chilled water provided by a
chiller, or any other air cooling apparatus. Air handling units may
include a variety of structures that may be used to filter the air,
including pleated media, electrostatic filters, high efficiency
particulate air filters, gas-phase units, ultraviolet air treatment
units, or any other air filtering structure. Humidification of the
air may be provided via the air handling unit and/or coupled
humidifier units.
[0004] HVAC systems using air handling devices may also include any
number of additional devices to supply controlled air flows to a
building or building zone. While air flow may be varied using a
single air handling unit capable of being controllably operated at
variable speeds, variable air volume terminal units (i.e., variable
air volume boxes, variable air volume units, etc.) are often used
to control air flow rate at a building zone or building room level.
Variable air volume units are typically connected to central HVAC
control systems and/or local HVAC control systems. In many HVAC
systems, the air flow rate is varied not only to control the
distribution of air, but also to control temperature. For example,
some systems use supply air of a relatively constant temperature,
or cooled to a relatively constant temperature, (e.g., 50-60
degrees, etc.) and modify air flow rates provided to building zones
to meet desired temperature setpoints. Variable air volume units
may include a damper for regulating the amount of air flow provided
to the building zone the variable air volume serves. A variable air
volume unit damper may be coupled to an actuator which may position
the damper so that appropriate air flow is provided to the building
zone.
[0005] In modem systems, an HVAC control system may provide a
variety of inputs to and accept a variety of outputs from variable
air volume unit components (e.g., dampers, actuators, local VAV
control circuits, flow sensors, temperature sensors, etc.). Using
these inputs and outputs, an HVAC control system may control the
heating, ventilation, and air conditioning provided to specific
building zones. For example, an HVAC control system may receive
inputs from sensors related to an air flow rate and temperature of
a building zone and use a damper and its accompanying actuator to
appropriately position the damper such that a desired air flow rate
is provided to the building zone.
[0006] Typical HVAC control systems use a plurality of sensors to
monitor HVAC variables to be controlled, such as temperature,
humidity, or air flow rate. An HVAC control system may typically
regulate these controlled variables by considering a feedback
signal generated by a sensor disposed to monitor the controlled
variable. For example, an HVAC control system may allow or generate
more air flow into a building zone based on a sensed temperature
level. If a sensed temperature level is at 85 degrees Fahrenheit,
the HVAC control system may allow or generate more supply air flow
into a building to reach a desired lower temperature target or
setpoint. If a temperature setpoint is 72 degrees Fahrenheit, for
example, the HVAC control system may determine that supply air flow
rate should be near maximum to rapidly make up the thirteen degree
difference. In a feedback-based system, the resulting changed
temperature is periodically looped back into the HVAC control
system via inputs from temperature sensors, and further adjustments
may be made based on the changed data. This sort of process may be
looped or repeated in a near infinite manner whereby the HVAC
control system may constantly be adjusting variables of operation
based on feedback from sensors.
[0007] HVAC systems have conventionally been primarily
feedback-based systems. The majority of the HVAC setpoints are
often rather static, often set manually, and typical HVAC control
systems use feedback loops to maintain building zone variables such
as temperature near the static setpoints of the system. These
typical HVAC control systems may suffer from a number of challenges
and lead to a number of building management issues such as
inefficient HVAC operation, uncomfortable building zones, higher
maintenance or operation costs, and shorter equipment lifespans.
For example, some typical feedback-dominated systems may suffer
from a condition known as "hunting" wherein an HVAC system may
oscillate an output around a setpoint. This oscillation may happen
when, for example, a number of people enter a building zone and
have been in the room long enough to heat the room above the
setpoint temperature range. In a feedback-dominated HVAC system,
the HVAC controller will not command additional air flow to the
building zone until the people have already heated the room beyond
a certain setpoint range. Once the HVAC system senses this
temperature change, it may begin providing a greater cool air flow
rate to the building zone than the system was previously providing.
In some cases, if the building zone has heated relatively rapidly
from the people, equipment, and lighting of the zone, the HVAC
system may have to substantially increase the air flow rate. It is
undesirable to substantially increase air flow rate and/or
otherwise attempt to substantially change temperature of a building
zone because these substantial changes may result in "overshoots"
wherein the HVAC system misses a setpoint target and cools or heats
the building zone too much, for example. When an overshoot occurs,
an HVAC system may attempt to correct for the overshoot, which may
result in a repeat effect, causing the condition of hunting or
oscillation. During this process, the system may expend more energy
than is desirable and may result in periods of discomfort for room
occupants.
[0008] In addition to temperature control, HVAC control systems are
used for building ventilation. Ventilation may be described as the
movement of air to the inside of a building from the outside of a
building. Ventilation air is important for providing acceptable
indoor air quality to people. Ventilation air may dilute and/or
remove airborne pollutants such as volatile organic compounds
(VOCs) and respirable suspended particles (RSPs). The rate of
ventilation air required is often expressed by volumetric flow rate
of supply air (e.g., outside air) being introduced into a building
zone.
[0009] It would be desirable to provide an HVAC control system and
method that takes into account heat gains from people and/or
electrical equipment. It would further be desirable to improve air
quality by ensuring proper ventilation. It would further be
desirable to enable users to reduce energy consumption by varying
the minimum ventilation given the number of occupants in a zone. It
would further be desirable to improve occupant comfort by reducing
the size and number of temperature errors throughout the day. It
would further be desirable to reduce occupant discomfort by
calculating a setpoint temperature for a zone based on occupants'
preferences. It would further be desirable to improve temperature
control for a room because heat gains from people, equipment, and
lights are compensated for at the time convective heat gains enter
the zone.
[0010] It would be desirable to provide a system and/or method that
satisfies one or more of these needs or provides other advantageous
features. Other features and advantages will be made apparent from
the present specification. The teachings disclosed extend to those
embodiments that fall within the scope of the claims, regardless of
whether they accomplish one or more of the aforementioned
needs.
SUMMARY
[0011] One embodiment of the application relates to an HVAC control
system configured to control the environment of a building zone.
The HVAC control system includes a means for determining a number
of people occupying the building zone and a means for determining
properties of other heat transferring objects located within the
building zone. The HVAC control system may also include a
controller, the controller being configured to compute a projected
heat gain in a building zone based on the determined number of
people occupying the building zone and the determined properties of
the other heat transferring objects located within the building
zone. The controller may use the computed projected heat gain to
determine a zone ventilation setpoint for the building zone.
[0012] Another embodiment of the application relates to a method of
providing HVAC control to a zone using an HVAC control system,
including determining a desired volumetric flow rate, selecting a
volumetric flow rate setpoint, and sending the selected volumetric
flow rate setpoint to a zone ventilation device. Determining a
desired volumetric flow rate includes computing a projected
convective heat gain to the zone from people and other heat
transferring objects located within the building zone and
considering at least one air property.
[0013] Yet another embodiment relates to a controller configured to
control the environment of a building zone. The controller may
include a data processor. The controller may also include a zone
ventilation device interface communicably coupled to the data
processor, the zone ventilation device interface being configured
to route a control signal to a zone ventilation device. The
controller may also include a sensor interface communicably coupled
to the data processor, the sensor interface being configured to
accept a signal from at least one sensor located within the
building zone. The data processor may be configured to compute a
projected convective heat gain to the building zone from people and
other heat transferring objects located within the building zone
based on a signal received from the sensor interface. The data
processor may also be configured to send a control signal to the
zone ventilation devices via the zone ventilation device interface
based at least partially on the computed projected convective heat
gain.
[0014] Alternative exemplary embodiments relate to other features
and combinations of features as may be generally recited in the
claims.
BRIEF DESCRIPTION OF THE FIGURES
[0015] The application will become more fully understood from the
following detailed description, taken in conjunction with the
accompanying drawings, wherein like reference numerals refer to
like elements, in which:
[0016] FIG. 1 is a perspective view of an exemplary building that
may include an HVAC control system;
[0017] FIG. 2 is a perspective view of a building zone that may be
controlled by an HVAC control system of an exemplary
embodiment;
[0018] FIG. 3 is a block diagram of an HVAC control system
configured to sense preferred temperatures of people located within
building zones, according to an exemplary embodiment;
[0019] FIG. 4 is a block diagram of an HVAC control system,
according to an exemplary embodiment;
[0020] FIG. 5 is a logical block diagram of an HVAC control system,
according to an exemplary embodiment;
[0021] FIG. 6A is a diagram of a zone, the diagram illustrating
various heat gain components from people, equipment, and
lights;
[0022] FIG. 6B is a block diagram that illustrates a relationship
between instantaneous convection, radiated heat, delayed
convection, and the cooling load of the room or zone due to people,
equipment, and lights;
[0023] FIG. 7 is a flow chart of a method of providing HVAC control
to a zone using an HVAC control system, according to an exemplary
embodiment;
[0024] FIG. 8 is a detailed flow chart of a method of providing
HVAC control to a zone using an HVAC control system, according to
an exemplary embodiment.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0025] Before turning to the figures which illustrate the exemplary
embodiments in detail, it should be understood that the application
is not limited to the details or methodology set forth in the
following description or illustrated in the figures. It should also
be understood that the phraseology and terminology employed herein
is for the purpose of description only and should not be regarded
as limiting.
[0026] In general, and referring generally to the FIGURES, an HVAC
control system of any preferred embodiment may include at least one
people sensor, at least one object sensor, a controller, and
outputs to zone ventilation devices such as variable air volume
units. The people and object sensors may be able to sense, via any
number of different methods, the number and/or properties of people
and other heat transferring objects, such as lights and equipment,
located within a building zone. The controller, which may include a
feedforward control, may be configured to compute a projected heat
gain to the building zone based on the sensed heat transferring
people and objects. The HVAC control system may then determine a
desired volumetric flow rate of air into the building zone, based
at least partially on the computed projected heat gain. The HVAC
control system may then use the desired volumetric flow rate to
determine dynamic setpoints and adaptively control the environment
of the building zone with reduced reliance on temperature feedback
and static setpoints.
[0027] Referring to FIG. 1, a perspective view of an exemplary
building 100 that may include an HVAC control system is
illustrated. Building 100 may be a commercial building, an
industrial building, an institutional building, a healthcare
facility, a school, a manufacturing plant, an office building, a
residential building, or any other building that makes use of HVAC
systems. Building 100 may include one or more air handling units
102, shown in FIG. 1 as a rooftop air handling unit, and one or
more building zones 104. As illustrated, building 100 may include
more than one floor, more than one room, and may house any number
of people, lights, and other equipment.
[0028] Building 100 and its HVAC system may include any type or
number of air handling units (e.g., a makeup air unit, a rooftop
air unit, a fan coil unit, a constant air volume air handling unit,
a variable air volume air handling unit, etc.). Building 100 may
also include any type or number of HVAC subsystems and/or HVAC
zones. For example, building zone 104 may be an HVAC zone
comprising a single room or multiple rooms. In other buildings or
systems, each floor of a building may be a separate building zone
or HVAC zone controlled by a separate HVAC system or HVAC
subsystem. Any number of individual heating, cooling, or air
control devices may be disposed around the building and/or each
building zone. For example, variable air volume units may be
installed throughout building 100. The variable air volume unit or
set of variable air volume units may be used by an HVAC control
system to regulate the air flow rate and other variables (e.g.,
heat, humidity, outside air, etc.) provided to the building zone by
the HVAC system. Each variable air volume unit may be of any type
or design and may include a damper, an actuator, and an actuator
control circuit. Variable air volume units may generally be
referred to as a type of zone ventilation device. A zone
ventilation device may be considered any device or devices
configured to provide controlled ventilation (heated, cooled,
filtered, or otherwise) to a building zone. For example, a zone
ventilation device may be a terminal variable air volume unit, an
intermediate variable air volume unit, a fan, an air conditioner,
an evaporative -cooler, an zone-specific air handling unit,
etc.
[0029] Referring to FIG. 2, a close-up perspective view of a
building zone 104 is shown, according to an exemplary embodiment.
Building zone 104 may include an HVAC vent 108 coupled to ductwork
106. Supply air flow or ventilation may be provided to zone 104 via
vent 108. Building zone 104 may also include lights 110, equipment
112 (shown as a computer workstation), laptops 114, people 116,
118, and one or more sensors 120. Building zone 104 may include any
number of additional or alternative objects, equipment, structures,
surfaces, people, and/or lights.
[0030] Sensors 120 may be disposed within and/or around building
zone 104 and may be configured to sense HVAC-related conditions or
variables of building zone 104. For example, sensors 120 may be
temperature sensors, humidity sensors, air quality sensors,
equipment sensors, person sensors, lighting sensors, heat
transferring object sensors, infrared sensors, RFID transceivers,
and/or any other type of sensor that may be configured to sense an
HVAC related condition, property, number of people, property of
other heat transferring objects located within the building zone,
or any other related variable of building zone 104. Sensors 120 are
shown disposed on the walls of building zone 104, but may be
located, positioned, or disposed in any manner or location within
building zone 104. Sensors 120 may also have any number of user
interface and/or communications features configured to facilitate
their operation with an HVAC control system. Sensors 120 may be
wireless or wired sensors configured to operate on a mesh network
or to operate on or with any other network topology.
[0031] Objects 112 through 118 are examples of heat transferring
people or objects that may transfer (via radiation and/or
convection) heat to building zone 104. For example, heat may be
transferred from people 116, 118, equipment 112, 114, and lighting
110 to building zone 104. One or more sensors 120 may be configured
to determine the number and properties of people located within
building zone 104. One or more sensors 120 may also be configured
to determine the number, type, and/or properties of other heat
transferring objects located within building zone 104.
[0032] According to an exemplary embodiment, a variety of sets or
different types of sensors 120 may exist within building zone 104.
For example, a first set of sensors 120 may be configured to sense
ambient temperature of the zone, a second set of sensors 120 may be
configured to determine heat transferring properties (e.g., number
of people, average heat generation per person, preferred
temperature settings, etc.) of people in the building zone, and a
third set of sensors may be configured to determine heat
transferring properties of non-human objects within the zone (e.g.,
number of lights, number of computers, heat of the lights, power
used by the lights, efficiency of the equipment and lights,
etc.).
[0033] According to an exemplary embodiment, some sensors 120 may
be thermographic imaging sensors capable of using a thermal imager
to detect, display and record thermal patterns and temperatures
across the surface of an object. For example, a sensor 120
configured to use infrared thermography to detect heat transferring
objects within a building zone may be able to compare the ambient
or average temperature of objects within the zone to areas of the
zone that exceed some threshold. Using this information, for
example, a thermographic sensor may be able to determine that there
are six heat radiating lights within building zone 104 by
determining that the surface temperatures of the lights are greater
than thirty degrees hotter than the average temperature of the
building zone. Using thermographic sensors, an HVAC control system
may be able to detect different heat signatures, (e.g., for people,
equipment, and lights, etc.) and count the number of each located
in the building zone. Some thermographic sensors or a sets of
thermographic sensors may be able to calculate a projected heat
gain to the space without specifically identifying the objects
located within the building zone based on the difference between
the known ambient air temperature and the thermographically sensed
surfaces of heat transferring objects and/or people dispersed in
the zone.
[0034] According to another exemplary embodiment, various circuits
such as a resistor-capacitor circuit may be used as sensors to
determine heat transferring properties of the lights or other
power-using objects located within the building zone. Heat
transferring properties of lights may be the number of activated
lights located within a building zone, the power used by the lights
located within the building zone, the current flow through a
lighting circuit, or any other property of lights that may be used
to estimate heat transfer to a building zone. These properties may
be determined and reported to the HVAC control system for further
processing.
[0035] According to another exemplary embodiment, some properties
of heat transferring people and objects located within a building
zone may be obtained by a database and accompanying processing
components. For example, a database of network connections and/or
login information for a building zone may be maintained and this
information provided to the HVAC control system. Using this network
connection or login information, an HVAC control system may be able
to both determine the number of active workstations (and
accompanying equipment such as lights and computers) and/or the
number of active people located within the zone. In a building zone
having a number of single-user cubicles, each cubicle having a
similar desktop computer and lighting configuration, information
regarding the number of people located within the building zone,
the number of active lights located within the zone, and the number
of active desktop computers located within the zone may be
estimated relatively accurately using login information of a
building zone. Similarly, people, equipment and lights may be
estimated using schedule and meeting information related to a
building zone. For example, if a meeting zone such as a conference
room is reserved and/or otherwise scheduled, a database system may
access attendee information to estimate the number of people
located within the zone at any given time. Additionally, the system
may be programmed to assume that the lights of the building zone
may be turned on prior to the meeting and that the lights will
begin transferring heat to the building zone at that time.
According to various other exemplary embodiments, information
regarding schedules and/or network connection information may be
used to activate certain wireless sensors located within the
building zone in an attempt to conserve energy of those wireless
sensors. For example, an HVAC control system may be able to predict
people, equipment, and lighting heat loads based on scheduled or
occupancy information from the building occupants' primary or
office-wide scheduling systems such as LOTUS NOTES.RTM., LOTUS
CALENDAR.RTM., MICROSOFT OUTLOOK CALENDAR.RTM., MICROSOFT
EXCHANGE.RTM., phone system vacation settings, vacation schedules
of human resources software, and/or any other software that may be
available that the HVAC control system may draw upon to predict
occupancy and/or activity information.
[0036] Referring to FIG. 3, according to an exemplary embodiment,
sensors 120 configured to determine the number of people in a
building zone may be radio frequency identification ("RFID")
sensors. Each person 116, 118 in a building zone may normally carry
an RFID tag or transponder 306. RFID tag or transponder 306 may be
embedded or included with a person's identification badge, nametag,
cell-phone, PDA, uniform, key fob, or any other object a person may
frequently carry with him or her. Each person may be able to login
or access a personal setting interface 302 via an employee
intranet, internet, or standalone application. Interface 302 may
allow an employee to specify a number of personal comfort settings,
such as preferred temperature, that may be associated with each
worker's RFID transponder 306. Interface 302 may access information
from and store information to database 304. Database 304 may be
communicably coupled to HVAC control system 300 (e.g., METASYS.RTM.
building control system sold by Johnson Controls, Inc. or other
available building control systems, etc.). Database 304 may be
external HVAC control system 300 or may be integral or embedded
into HVAC control system 300. Whenever a person enters a building
zone having RFID-capable sensors configured to sense and/or read
RFID transponders, the sensors may communicate with database 304
and/or HVAC control system 300 to lookup information associated
with the sensed ID badge. The HVAC control system may then used
this looked-up information (e.g., preferred temperature, etc.) as
an input when determining a desired flow rate or setpoint of
various HVAC components relating to the building zone. Using such a
system, for example, a person who is more comfortable in a cooler
room might be able to automatically cause an increase in room
ventilation when he or she enters the room. When more than one
person is located in the same room or building zone, the HVAC
control system 300 may be configured to use the preferred
temperatures of a plurality of people in the building zone to
arrive at an average preferred temperature, median preferred
temperature, or some other group temperature or comfort-related
determination.
[0037] In addition to using RFID technology to identify people
within a building zone, other technologies and/or methods may be
used to identify the numbers of people in a zone and/or the
preferences of people in the zone. For example, wireless data
communication technologies or protocols such as 802.xx protocols
may be used, BLUETOOTH protocols, or any other wireless protocol
may be used to identify devices or tags 306 workers may normally
carry. Workplaces where PDA or Smartphone use is popular might, for
example, use sensed Bluetooth-enabled PDA's, Smartphones, and/or
mobile phones located within a building zone to provide identifying
information to a receiver or sensor 120 and eventually to a HVAC
control system.
[0038] According to one alternative embodiment, a sensor system may
be configured to determine or estimate the number of people in a
zone based on a sensed carbon dioxide generation rate. One such
possible sensor system configured to determine the number of people
in a building zone based on carbon dioxide is described in U.S.
Pat. No. 5,550,752, to Federspiel et al.
[0039] According to other various exemplary embodiments, the HVAC
control system is further configured to learn the heating
characteristics of the zone. The HVAC control system may use the
learned heating characteristics of the zone and the sensed people
to compute the projected heat gain to the zone based on people and
objects. For example, HVAC control system may learn that when a
building zone is occupied by a person, the person, lights, and
equipment of the zone will experience a certain average convective
heat gain relative to an unoccupied zone.
[0040] Sensors 120 may have various communications hardware and/or
software for communicating with components of an HVAC control
system. For example, sensors 120 may be of any wired or wireless
technology capable of communicating sensed information back to an
HVAC control system. According to one exemplary embodiment, sensors
120 are wireless-capable sensors configured to operate with IEEE
802.15 standards and protocols (e.g., ZigBee compatible
wireless-capable sensors, etc.).
[0041] Referring to FIG. 4, a block diagram of an HVAC control
system 300 is shown, according to an exemplary embodiment. An HVAC
control system 300 may include a controller 400, a plurality of
sensors, a graphical user interface display 438, and a control
array 436. HVAC control system 300 may be an HVAC control system
capable of controlling a plurality of building zones, an entire
building, or a single zone. While the various components of HVAC
control system 300 and controller 400 are shown integrated into a
single unit, it should be appreciated that distributed HVAC
systems, such as the METASYS.RTM. building control system sold by
Johnson Controls, Inc., may include one or more network automation
engines, one or more application data servers, one or more
communications networks, one or more field controllers connected to
the network automation engines or application data server via the
communications network, the field controller being capable of
driving any number of other field controllers or devices. According
to other alternative embodiments, controller 400 may have fewer
components and may be integrated into an actuator for a single
damper that controls ventilation to a relatively small (e.g.,
single room) zone. According to yet other alternative embodiments,
controller 400 may be installed in the residential context in a
home air handler, air conditioner, fan unit, or furnace.
[0042] Controller 400 may include a primary data processor 402, a
secondary microcontroller 404, a memory 406, a sensor interface and
controller 412, a zone ventilation device interface and controller
414, a network communications device 416, a wireless communications
device 418, a display output controller, and a control input
controller 422. The components of controller 400 may be contained
in a single housing or distributed around the various spaces or
building zones of a building.
[0043] Primary data processor 402 may be communicably coupled to
the various other components of the HVAC control system and is
generally configured to control each function of controller 400.
Primary data processor 402 may include digital or analog processing
components and/or be of any past, present, or future design that
facilitates control or features of HVAC control system 300. Primary
data processor 402 may be a single data processing device or
multiple data processing devices. Primary data processor 402 may
include any combination of program software and hardware capable of
providing control, display, communications, input and output
features to an HVAC control system. For example, primary data
processor 402 may include any number of additional hardware
modules, software modules, or processing devices (e.g., additional
graphics processors, communications processors, etc.). Primary data
processor 402 and/or secondary microcontroller 404 may coordinate
the various devices, components and features of the HVAC control
system (e.g., memory 406, sensor interface and controller 412, zone
ventilation interface and controller 414, etc).
[0044] Memory 406 is configured to store data accessed by HVAC
control system 300 or controller 400. For example, memory 406 may
store data input from zone sensors and actuators, data created by
primary data processor 402 that may be used later, intermediate
data of use in a current calculation or process, or any other data
of use by HVAC control system 300. Memory 406 may include both a
volatile memory 410 and a non-volatile memory 408. Volatile memory
410 may be configured so that the contents stored therein may be
erased during each power cycle of the controller 400. Non-volatile
memory 408 may be configured so that the contents stored therein
may be retained across power cycles, such that upon controller 400
power-up or reset, data from previous system use remains available
to the controller or user. According to an exemplary embodiments
non-volatile memory 410 may store any number of databases, tables,
or profiles for use with the various zones or functions of the HVAC
control system 300. According to other various exemplary
embodiments, controller 400 may access remote data stores or
servers via wired or wireless networks.
[0045] Sensor interface and controller 412 may be a device or set
of devices configured to facilitate signal connections between a
set of building zone sensors 432 and controller 400. Sensor
interface 412 may use any number of hardware technologies and/or
software protocols to accomplish necessary connections and or
communications with sensors such as environment sensors 424, people
sensors 426, RFID sensors 428, lighting sensors 430, zone
temperature sensors 434, and any number of additional sensors or
devices (e.g., security devices, smoke alarms, etc.). Sensor
interface and controller 412 may also be wired or connected to
wireless receivers distributed around a building zone. For example,
sensor interface and controller 412 may be coupled to a wireless
RFID transceiver or receiver configured to identify people
occupying a building zone.
[0046] Zone ventilation device interface and controller 414 may be
a device or set of devices configured to facilitate signal
connections between a set of zone ventilation devices (e.g., wired
zone ventilation devices 415, wireless zone ventilation devices
452, etc.) and controller 400. Zone ventilation device interface
and controller 414 may use any number of hardware technologies
and/or software protocols to accomplish necessary connections and
or communications with zone ventilation devices. Zone ventilation
device interface 414 may also use wireless technology and/or may be
communicably connected to wireless communications device 418 to
accomplish communications with wireless zone ventilation devices
452. It is important to note that zone ventilation devices 452, 415
may include any number of local control circuits, sensors, and/or
actuators that may be used to facilitate local or device level
control of the various zone ventilation devices of the HVAC control
system.
[0047] Wireless communications device 418 is generally configured
to establish communication links with wireless sensors and
actuators of HVAC control system 300. Wireless communications
device 418 may be configured to use any variety of wireless
communications technologies or topologies (e.g., mesh topology,
star, etc.). According to an exemplary embodiment, building zones
may be partially wireless and partially wired. Wireless
communications device 418 may connect to any number of various
zones sensor sets 448 that may include sensors such as wireless
environment sensors 440, wireless people sensors 442, wireless RFID
sensors 444, wireless lighting sensors 446. Wireless communications
device 418 may also connect to any other wireless sensor such as
wireless zone temperature sensors 450, wireless zone ventilation
devices 452, and/or any other type of wireless device including
intermediate wireless access points, coordinators, routers, and/or
gateways.
[0048] Network communications device 416 is generally configured to
provide a connection to a data communications network such as an
Ethernet-based LAN or WAN. According to other various embodiments,
network communications device 416 is a wireless network
communications device. Users of the HVAC control system 300 may use
network communications device 416 to perform remote control
functions and/or to connect distributed components of controller
400 or HVAC control system 300. Network communications device 416
and/or wireless communications device 418 may also be connected to
a building-wide or multiple-zone HVAC system, network, network
automation engine, and/or application data server. These components
may be a part of the METASYS.RTM. building control system sold by
Johnson Controls, Inc. or other available building control systems,
etc.
[0049] Controller 400 may also include any number of secondary
microcontrollers 404 that may be configured to compute or process
various functions of the HVAC control system 300. Controller 400
may also include control input controllers 422 and display output
controllers 420 that may be communicably connected to control
arrays 436 and/or graphical user interface displays 438. Using
these devices, controller 400 may be able to serve as a standalone
device, not requiring the use of a separate networked workstation
or browser to control various features of controller 400.
[0050] Referring to FIG. 5, a logical block diagram of an HVAC
control system with a control strategy for zone ventilation devices
is illustrated, according to an exemplary embodiment. Sensors 120,
and any accompanying processing components, wireless receivers, and
other devices used with sensors, may be installed within a building
zone and configured to provide a variety of inputs to HVAC control
system 300. Sensors 120 may provide input in the form of the number
of people, power use by lighting, power use by equipment, RFID
numbers sensed, and any other information or properties of people,
lighting, and equipment of the building zone that may be used by
feedforward control 508 to determine convective heat gain to a
building zone from people, equipment, and lights.
[0051] Preferred temperature setpoint calculator 504 takes input
from sensors 120. The input provided to preferred setpoint
calculator 504 from sensors 120 may be in the form of a number of
people, people identifiers, and/or a preferred temperature for each
person occupying the zone. According to an exemplary embodiment,
preferred setpoint calculator 504 may use person identification
information obtained by sensors 120 to poll preferred temperature
database 505 for a preferred temperature of each person occupying
the relevant building zone. Preferred temperature setpoint
calculator 504 may use any number of different calculations to
calculate a room temperature setpoint from the preferred
temperature for each person in the room. According to one exemplary
embodiment, preferred temperature setpoint calculator 504 may use
the following equation to determine the preferred temperature
setpoint:
T set = T set , 1 + T set , 2 + + T set , n n ##EQU00001##
T.sub.set,n is the preferred temperature for the nth person in a
building zone and n is the number of people currently located in
the building zone. Preferred temperature setpoint calculator 504
may provide an input to preferred temperature setpoint feedback
control 506. It is important to note that preferred temperature
setpoint calculator 504 may make any additional calculations or
substitute calculations to arrive at a preferred temperature
setpoint (T.sub.set). For example, preferred temperature setpoint
calculator 504 may perform various weighing calculations to assign
a higher priority to a first person compared to a second person.
Temperature setpoint calculator 504 may also access database 505 to
read or write preferred temperature information.
[0052] Feedback control 506 also accepts an input from one or more
temperature sensors 502 located in the building zone. Using the
sensed temperature, feedback control 506 determines a volumetric
flow setpoint (V.sub.FB) necessary to maintain the preferred
temperature setpoint (T.sub.set) determined by preferred
temperature setpoint calculator 504.
[0053] Feedforward control 508 may determine a desired volumetric
flow rate (V.sub.FF). HVAC control system 300 may use the desired
volumetric flow rate to improve HVAC performance and building zone
comfort by adjusting the supply airflow provided to the building
zone to balance heat gains from people, equipment, and lights. This
determination may allow HVAC control system 300 to maintain a
building zone temperature or ventilation level closer to desired
setpoints than would be possible with conventional control
strategies. Feedforward control 508 may compute a projected or
predicted convective heat gain (Q.sub.CONV) to a building zone
based on properties of people, equipment, and lights. According to
one exemplary embodiment, feedforward control 508 may use the
following equation to determine a desired volumetric flow rate
(V.sub.FF), where (.rho.) is the density of air, ( .sub.p) is the
specific heat of supply air, (T.sub.ZONE) is the building zone
temperature, and (T.sub.SUPPLY) is the supply air temperature:
V FF = Q CONV .rho. c P ( T ZONE - T SUPPLY ) ##EQU00002##
[0054] Q.sub.CONV may be computed in a variety of ways. For
example, among other ways Q.sub.CONV may be computed, Q.sub.CONV
may be computed using the instantaneous convection of the people,
lighting and equipment sensed in the zone, or the sum of
instantaneous convection and delayed convection. Instantaneous
convection refers to heat transferred to the zone air via
convection from people, equipment, lights and other objects.
Delayed convection refers to convection from the interior surfaces
(e.g., walls, furnishings, etc.) of the room to the zone air that
exists because radiated heat from people, equipment, lights and
other objects are absorbed by those interior surfaces and
transferred back to the room air via convection.
[0055] Referring to FIG. 6A, a block diagram of a zone is shown
that illustrates sensible heat gain components from people,
equipment, and lights. Heat gains from people, equipment, and
lights may be split into two components: radiation heat that is
absorbed by other surfaces in the room; and convection heat that is
transferred to the air of the room. For example, people create some
amount of instantaneous convective heat gain in the zone
(Q.sub.CONV,PEOPLE); equipment create instantaneous convective heat
gain (Q.sub.CONV,EQUIP); and lights create instantaneous convective
heat gain (Q.sub.CONV,LIGHTS) People may also radiate some amount
of radiated heat (Q.sub.RAD,PEOPLE) to the interior surfaces of the
zone; equipment radiate (Q.sub.RAD,EQUIP); and lights 68 radiate
Q.sub.RAD,LIGHTS. Some radiated heat may be absorbed by the
interior surfaces (e.g., furnishings, walls, ceilings, floors,
etc.) of the room or zone and the temperatures of those surfaces
will increase because of the absorbed radiation. If a surface
temperature is greater than the room temperature, then some or all
of the radiation absorbed by the surface will be transferred back
to the air of the room or zone from the surfaces
(Q.sub.CONV,SURFACE). FIG. 6B is a block diagram that further
illustrates the relationship between instantaneous convection
(Q.sub.CONV,INST), radiated heat, delayed convection
(Q.sub.CONV,DELAY), and the cooling load of the room or zone due to
people, equipment, and lights.
[0056] Instantaneous convection may be determined using the
following equation:
Q.sub.CONV,INST=.SIGMA.(Q.sub.CONV,PEOPLE+Q.sub.CONV,LIGHTS+Q.sub.CONV,E-
QUIP)
The delayed convection equals the energy that is absorbed by
interior surfaces and then transferred back to the room at a later
time by convection. In other words, Q.sub.CONV,DELAY may be set to
equal Q.sub.CONV,SURFACE.
[0057] Depending on the processing power available to the HVAC
control system or the zone controller, convective heat gain
(Q.sub.CONV) computed or input to feedforward control 508 of FIG. 5
may be computed or predicted using detail beyond raw counts of
occupants, preferred temperatures, lights, and computers. For
example, tables provided by the handbook "2005 ASHRAE Handbook
Fundamentals, SI Edition" may be used to determine the heat created
by person located within the zone and the percentage of that heat
that is convective. Two exemplary entries of such a table may
include the following:
TABLE-US-00001 Heat that is Heat that is Convective Convective (Low
Air (High Air Degree of Activity Application Heat Velocity)
Velocity) Seated, light work Office 70 40% 73% Moderately Active
Office 75 42% 62%
To determine the convective heat gain per person based on the
table, for example, heat for a certain activity may be multiplied
by the percentage of heat for that activity level that is
convective. The convective heat gain of each person in the zone may
be added to provide Q.sub.CONV,PEOPLE.
[0058] According to an exemplary embodiment, RFID tag or
transponder 306 and RFID compatible sensors 120 of FIG. 3 and other
various FIGS. of this application may use RFID data to determine
the degree of activity of the people in a zone in addition to the
number of people in the zone. For example, in a room where people
are frequently coming and going, the average number of people in
the zone may be relatively low, but it may be determined that the
activity level of the room is high because of the short amount of
time each RFID tag stays within the zone. According to another
exemplary embodiment, a zone with a relatively large number of low
power RFID sensors may be used to sense activity by determining how
often an RFID tag moves from sensor to sensor in a zone. According
to yet further exemplary embodiments, RFID tags 306 (or a database
drawing upon the tags) may store vital statistics for the people in
the zone such that heat may be more accurately predicted for any
given person (e.g., a 2501b man may generally do more work to stand
up and move and may therefore create more heat than a 1501b man
standing and moving the same distance).
[0059] Referring still to FIGS. 5-6B, Q.sub.CONV,LIGHTS may be
obtained by based on the heat gain from electric lighting used in
the room. While the heat gain from electrical lighting may be
provided by a variety of methods and/or equations, one such
equation provided by the handbook "2005 ASHRAE Handbook
Fundamentals, SI Edition" is: Q.sub.light=WF.sub.ulF.sub.sa; where
W is the total light wattage, F.sub.ul is a lighting use factor
that equals the ratio of wattage in use to total installed or
potential wattage, and F.sub.sa is the lighting special allowance
factor that accounts for different fixture or lighting types (e.g.,
fluorescent, high-pressure sodium, metal halide, mercury vapor,
etc.) and/or fixtures that are ventilated or installed so that only
part of the heat gain enters the room. Tables of use factors and
special allowance factors may be found in the handbook "2005 ASHRAE
Handbook Fundamentals, SI Edition". The instantaneous convective
heat gain from lights (Q.sub.CONV,LIGHT) may be determined by
multiplying the total heat gain from lights (Q.sub.light) by the
fraction of energy that is convective. According to various sources
such as "Heating, Ventilating, and Air Conditioning Analysis and
Design," by McQuiston, et al., 2005, the heat gain for fluorescent
fixtures used in office zones is often assumed to be around 59
percent radiative and 41 percent convective. The same source
estimates that incandescent fixtures provide a heat gain mixture of
approximately 80 percent radiative heat and 20 percent convective
heat.
[0060] Convective heat gain from equipment (Q.sub.CONV,EQUIP) may
include heat from electric motors, appliances, laboratory
equipment, medical equipment, office equipment, amplifiers, power
supplies, commercial cooking appliances, medical equipment,
computer equipment, laser printers and copiers, vending machines,
mail-processing equipment, and any number of other different types
of equipment. Sources such as the handbook "2005 ASHRAE Handbook
Fundamentals, SI Edition" may contain tables of heat gains and
summaries of radiant/convective heat percentages for many various
types of equipment. The convective portion for many types of office
equipment, for example, is typically between about 60 and 90
percent.
[0061] While delayed convection (Q.sub.CONV,DELAY) may be computed
by the controller and accounted for using feedforward control 508
if adequate processing power is available, using only instantaneous
convection as the convective heat gain (e.g.,
Q.sub.CONV=Q.sub.CONV,INST) may result in a less processor
intensive control strategy. Remaining load disturbances caused by
convection delay may largely and eventually be removed by room
temperature feedback control 506 of FIG. 5. Feedback control 506
may also remove disturbances caused by sensor and modeling errors
used to compute the instantaneous convective gains, solar gain, and
other heat gains throughout the exterior walls, floors, and
ceilings.
[0062] Referring again to FIG. 5, feedforward control 508 may be
communicably coupled to database 509 that may contain various
lookup tables relating to computing variables or components such as
Q.sub.CONV, Q.sub.CONV,INST, Q.sub.CONV,DELAY, Q.sub.CONV,PEOPLE,
Q.sub.CONV,LIGHTS, Q.sub.CONV,EQUIP, etc. For example, database 509
may be a relational database capable of relating a zone's
characteristics, expected people activity levels, lights, and
equipment to table entries such as the tables of the sources
mentioned above that provide estimated total heat amounts and
convective heat/radiant heat percentages. Feedforward control 508
may use the results of queries drawing upon database 509 to compute
Q.sub.CONV for use in the equation used by feedforward control 508
to determine a desired volumetric flow rate. According to various
alternative embodiments, feedforward control 508 or other
components of the controller or HVAC control system may use any
number of lookup tables, databases, memories, and/or analog or
digital circuits to determine Q.sub.CONV.
[0063] Referring still to FIG. 5, summer 510 receives input from
feedforward control 508 and feedback control 506 to provide a
control signal to limit determinations block 514. Summer 510 may
help control system 300 account for both the preferred temperature
setpoints of people located within the building zone and for
projected changes in room temperature due to the sensed or
determined people, lights, and equipment of the zone.
[0064] Ventilation requirement block 512 may determine or adjust a
lower limit of supply airflow. Using the sensed number of people
located within a building zone, ventilation requirement block 512
may lower energy consumption and improve the comfort and health of
occupants by adjusting a lower limit of supply airflow. Ventilation
requirement block may use any number of lookup tables and/or
equations to determine a lower limit of supply airflow based on a
sensed number of people located within a building zone. For
example, ventilation requirement block 512 may use any number of
equations recommended, suggested, and/or required by standards or
building codes such as the standards published by the American
Society of Heating, Refrigerating and Air Conditioning Engineers
(ASHRAE) or the American National Standards Institute (ANSI). For
example, ventilation requirement block 512 may use equations based
on ANSI/ASHRAE Standard 62.1-2004 "Ventilation for Acceptable Air
Quality" to determine the building zone outdoor airflow rate
(V.sub.OT). One possible example is:
V OT = R P n + R A A Z E Z ##EQU00003##
(R.sub.P) is the desired outdoor airflow rate required per person
as determined from a lookup table (e.g., Table 6-1 of ANSI/ASHRAE
Standard 62.1-2004) or equation. (n) is the number of sensed people
in a building zone. (R.sub.A) is the outdoor airflow rate required
per unit area as determined from a lookup table (e.g., Table 6-1 of
ANSI/ASHRAE Standard 62.1-2004) or equation. (A.sub.Z) is the net
occupiable floor area of the room. (E.sub.Z) is the building zone
distribution effectiveness as determined from a lookup table (e.g.,
Table 6-1 of ANSI/ASHRAE Standard 62.1-2004, etc.) or equation.
Ventilation requirement block 512 may access database 513 to
retrieve information from a variety of lookup tables. A determined
lower limit of the supply airflow setpoint (V.sub.min) may be
determined based on any number of lookup tables and/or equations.
For example, a determined lower limit of the supply airflow
setpoint (V.sub.min)may be determined from equation:
V MIN = V OT f OA ##EQU00004##
where (f.sub.OA) is the fraction of outdoor air in the supply
air.
[0065] Limit determinations block 514 may determine the final
volumetric flow rate setpoint, according to an exemplary
embodiment. Limit determinations block 514, may, for example,
determine whether to use a setpoint based on (V.sub.MAX), the
maximum flow rate for the building zone based on design and/or
equipment conditions, or to use a setpoint based on the desired
volumetric flow rate (V.sub.FF). Limit determinations block 514,
may also, for example, determine whether to use the minimum
volumetric flow rate (V.sub.min), based on the number of sensed
people in the zone, instead of the desired volumetric flow rate
(V.sub.FF) and feedback-based volumetric flow setpoint (V.sub.FB).
According to one exemplary embodiment, the setpoint for volumetric
flow rate (V.sub.SET) may be determined from:
V.sub.SET=min{V.sub.max, max [V.sub.min, (V.sub.FF+V.sub.FB)]}
where the maximum of (V.sub.min) and (V.sub.FF+V.sub.FB) is first
determined to ensure a setpoint that accounts at least for current
ventilation flow and the ventilation flow setpoint or some
predetermined minimum flow rate. The system then selects the
minimum of that predetermined number and the maximum flow rate
(V.sub.MAX).
[0066] According to various other exemplary embodiments, any number
of limit or filter computations or determinations may be made by
limit determination block 514. For example, limit determination
block 514 may consult a database or lookup table 515 to determine a
minimum volumetric airflow based on the size of the building zone
in addition to the number of people, ensuring that even if the
sensed number of people is incorrect, some minimum airflow for the
zone will be met. According to various other exemplary embodiments,
limit determination block 514 only checks to ensure that a
threshold maximum volumetric flow rate is not exceeded. In some
systems, limit determination block 514 may not exist at all or may
exist embedded within other calculations or blocks of HVAC control
system 300. Limit determinations block may access database 515 to
lookup data related to any number of relevant variables.
[0067] Once a volumetric flow point setpoint has been determined by
one or more of the various components or blocks of HVAC control
system 300, the setpoint may be output from a controller to a zone
ventilation device 521. Zone ventilation device 521 may include a
local feedback controller 516 that modulates a flow-affecting
actuator 518 of a damper. Feedback controller 516 may obtain input
from one or more flow sensors that assist in accurately achieving
the volumetric flow rate setpoint.
[0068] It is important to note that while FIG. 5 displays an HVAC
control system controlling a zone ventilation device including a
damper, the HVAC control system illustrated in FIG. 5 may be
adapted for use with a variety of different zone ventilation
devices. For example, flow rate to various building zones may be
controlled using a HVAC control system having variable frequency
blowers or a combination of variable frequency blowers and other
zone ventilation devices. According to other various embodiments,
zone ventilation devices or heating or cooling devices may
experience "on/off" control cycles and/or other variable control
based on input received from a controller having people, lighting,
and equipment sensing features described herein. For example, a
flow rate of chilled or heated water in chilled ceiling or floor
tiles or zones could be controlled using a modified version of the
logical block diagram shown in FIG. 5.
[0069] The components or blocks of FIG. 5 may be configured to
refresh, re-sense, or update on any variety of intervals. For
example, feedback control 516 may update or refresh at a faster
rate than feedforward control 508 and/or feedback control 506. By
way of further example, some low-power wireless sensors 120 may
refresh relatively infrequently so that sensors 120 do not
frequently interfere with other RF-based devices located around the
building zone or building. According to other exemplary
embodiments, people sensors or other blocks of HVAC control system
300 update or refresh at a relatively much faster rate than other
components in an attempt to begin adjusting system variables as
soon as the sensed properties of people, equipment, or lighting
within the room change.
[0070] It is also important to note that the logical block diagram
of the HVAC control system shown in FIG. 5 may be implemented in
hardware and/or software in a variety of ways. For example, the
HVAC control system may be implemented in a largely computer
software-based system having a variety of sensing inputs and
actuator control outputs. According to other various embodiments,
the HVAC control system may be implemented using a mix of hardware
and/or software modules.
[0071] Referring to FIG. 7, a process 700 of providing HVAC control
to a zone using an HVAC control system is illustrated, according to
an exemplary embodiment. The number of heat transferring people or
objects located within a zone and/or any number of other properties
of heat transferring objects occupying a building zone may be
determined (step 702). Once heat transferring objects (and any
relevant properties) within a building zone have been determined,
an HVAC control system may compute a theoretical or projected heat
gain (step 704) to a building zone from the determined heat
transferring people or objects located within the zone. Using the
heat gain projected in step 704, the HVAC control system may then
determine a desired flow rate (step 706). The HVAC control system
may consider certain flow rate limits (step 708) when considering
the various system computations or variables. An HVAC control
system may use any number of further steps or processes to
determine a flow rate setpoint (step 710) and may eventually send
the determined flow rate setpoint to a zone ventilation device
(step 712) such as a damper (and/or a damper's corresponding local
control system).
[0072] Referring further to FIG. 7, the step of determining heat
transferring objects within a building zone (step 702) may make any
number of determinations related to heat transferring objects. For
example, the step of determining heat transferring objects within a
building zone may include collecting a variety of variables such as
the number of heat transferring objects sensed, the rate of heat
transferred to a volume of air per unit time, a preferred
temperature setpoint, a unit of power used, and/or any other
property or variable that may allow the HVAC control system to make
decisions based on the heat transferring objects located within a
building zone. These determinations may also include a number of
sub-steps and/or sub-calculations to derive variables to be used in
computing a theoretical heat gain to a building zone.
[0073] Referring now to FIG. 8, a detailed flow chart of a process
800 of optimizing a volumetric flow rate setpoint using an HVAC
control system is illustrated, according to an exemplary
embodiment. Any number of devices or processes may be utilized by
an HVAC control system to sense properties of people located within
the building zone (step 802). Any number of devices or processes
may also be utilized by an HVAC control system to sense properties
of lighting (step 804) and equipment (step 806) located within a
building zone. An HVAC control system may then calculate a
projected heat gain from the people located within the building
zone (step 812), lighting located within the building zone (step
814), and equipment located within the building zone (step 816). An
HVAC control system may then compute a total theoretical heat gain
to a building zone (step 820) using the sensed properties and/or
the calculated projected heat gains for the people, lighting, and
equipment located within the building zone. In addition to
considering the theoretical heat gain, an HVAC control system may
determine preferred temperature setpoints for the people located
within the building zone (step 822). Using the determined preferred
temperature setpoints, the HVAC control system may calculate an
average preferred temperature setpoint (step 824) for the people
located within the building zone. Summing or otherwise considering
both the preferred temperature(s) and the total projected
theoretical heat gain, the HVAC control system may determine a
desired volumetric flow rate (step 826). Before using the desired
volumetric flow rate determined in step 826, an HVAC control system
may determine a minimum flow rate setting based on the number of
people located within the building zone (step 828). An HVAC control
system may make any number of limit determinations during process
800. For example, an HVAC control system may select a maximum (step
830) of the minimum flow rate setting determined in step 828 and
the desired volumetric flow rate determined in step 826. Step 830
may also check to ensure that the selected or desired flow rate is
not higher than the maximum flow rate for the building zone or HVAC
equipment. An HVAC control system may make any number of setpoint
adjustments based on limits or other minimum/maximum checks. Once
calculations, limits, and other checks have been completed, an HVAC
control system may send the determined volumetric flow rate
setpoint to a zone ventilation device (e.g., a damper and/or the
damper's local control systems, an air flow control device, etc.)
(step 832). The zone ventilation device and/or the HVAC control
system may further adjust the components of the zone ventilation
device to the determined setpoint based on flow-sensing feedback
(step 834). At any point during process 800, process 800 may
refresh or loop back to start (or other step) to begin further
sensing and calculating operations and/or to determine whether
building conditions have changed.
[0074] While the exemplary embodiments illustrated in the figures
and described above are presently preferred, it should be
understood that these embodiments are offered by way of example
only. Accordingly, the present invention is not limited to a
particular embodiment, but extends to various modifications that
nevertheless fall within the scope of the appended claims. The
order or sequence of any processes or method steps may be varied or
re-sequenced according to alternative embodiments.
[0075] The present invention contemplates methods, systems and
program products on any machine-readable media for accomplishing
its operations. The embodiments may be implemented using an
existing computer processors, or by a special purpose computer
processor for an appropriate HVAC system, incorporated for this or
another purpose or by a hardwired system.
[0076] It is important to note that the construction and
arrangement of the HVAC control system as shown in the various
exemplary embodiments is illustrative only. Although only a few
embodiments have been described in detail in this disclosure, those
skilled in the art who review this disclosure will readily
appreciate that many modifications are possible (e.g., variations
in sizes, dimensions, structures, shapes and proportions of the
various elements, values of parameters, mounting arrangements, use
of materials, colors, orientations, etc.) without materially
departing from the novel teachings and advantages of the subject
matter recited in the claims. For example, elements shown as
integrally formed may be constructed of multiple parts or elements
(e.g., multiple processors, circuits, controllers, control
interfaces, sensors, etc.), the position of elements may be
reversed or otherwise varied (e.g., feedforward control, summer,
temperature setpoint calculation, limit determinations, ventilation
requirements, etc.), and the nature or number of discrete elements
or positions may be altered or varied (e.g., sensors,
communications devices, microcontrollers, etc.). Accordingly, all
such modifications are intended to be included within the scope of
the present invention as defined in the appended claims. The order
or sequence of any process or method steps may be varied or
re-sequenced according to alternative embodiments. In the claims,
any means-plus-function clause is intended to cover the structures
described herein as performing the recited function and not only
structural equivalents but also equivalent structures. Other
substitutions, modifications, changes and omissions may be made in
the design, operating conditions and arrangement of the exemplary
embodiments without departing from the scope of the present
inventions as expressed in the appended claims.
[0077] As noted above, embodiments within the scope of the present
invention include program products comprising machine-readable
media for carrying or having machine-executable instructions or
data structures stored thereon. Such machine-readable media can be
any available media which can be accessed by a general purpose or
special purpose computer or other machine with a processor. By way
of example, such machine-readable media can comprise RAM, ROM,
EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk
storage or other magnetic storage devices, or any other medium
which can be used to carry or store desired program code in the
form of machine-executable instructions or data structures and
which can be accessed by a general purpose or special purpose
computer or other machine with a processor. When information is
transferred or provided over a network or another communications
connection (either hardwired, wireless, or a combination of
hardwired or wireless) to a machine, the machine properly views the
connection as a machine-readable medium. Thus, any such connection
is properly termed a machine-readable medium. Combinations of the
above are also included within the scope of machine-readable media.
Machine-executable instructions comprise, for example, instructions
and data which cause a general purpose computer, special purpose
computer, or special purpose processing machines to perform a
certain function or group of functions.
[0078] It should be noted that although the diagrams herein may
show a specific order of method steps, it is understood that the
order of these steps may differ from what is depicted. Also two or
more steps may be performed concurrently or with partial
concurrence. Such variation will depend on the software and
hardware systems chosen and on designer choice. It is understood
that all such variations are within the scope of the invention.
Likewise, software implementations of the present invention could
be accomplished with standard programming techniques with rule
based logic and other logic to accomplish the various connection
steps, processing steps, comparison steps and decision steps.
* * * * *