U.S. patent application number 11/318047 was filed with the patent office on 2007-06-28 for occupancy based ventilation system.
Invention is credited to Barrett E. Cole, Yuandong Gu.
Application Number | 20070149109 11/318047 |
Document ID | / |
Family ID | 38069241 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070149109 |
Kind Code |
A1 |
Gu; Yuandong ; et
al. |
June 28, 2007 |
Occupancy based ventilation system
Abstract
An occupancy based ventilation system for indoor air quality
that uses a counter to count the number of persons in a specific
indoor room or other area, wherein the number of persons determines
the degree of ventilation from the room's ventilation system. The
counter would keep track of both the number of persons and the
length of time each is present in the room. A feedback control
algorithm between the counting device and the ventilation
management controls provides for automatic control of the amount of
ventilation needed to insure a comfortable and efficient
environment.
Inventors: |
Gu; Yuandong; (Plymouth,
MN) ; Cole; Barrett E.; (Bloomington, MN) |
Correspondence
Address: |
Kris T. Fredrick, Esq.;Patent Services
Honeywell International Inc.
101 Columbia Road
Morristown
NJ
07962
US
|
Family ID: |
38069241 |
Appl. No.: |
11/318047 |
Filed: |
December 23, 2005 |
Current U.S.
Class: |
454/256 |
Current CPC
Class: |
F24F 11/30 20180101;
F24F 2120/10 20180101 |
Class at
Publication: |
454/256 |
International
Class: |
F24F 11/00 20060101
F24F011/00 |
Claims
1. An occupancy based ventilation system for indoor air quality of
a predetermined area, comprising: a room ventilation system for
providing outdoor air to said predetermined area; a counter for
counting the number of persons in said area and the amount of time
each person remains in said area, said counter producing a signal
representing the sum of the number of persons times the amount of
time for each person; and a processor for adjusting said
ventilation system for said area based on the signal produced, said
processor being adapted to determine the amount of ventilation
needed to maintain the CO.sub.2 concentration in the room air at a
predetermined level.
2. The system of claim 1, wherein said CO.sub.2 concentration is
500 ppm or less.
3. The system of claim 1, wherein said counter is positioned by the
entrance to said area.
4. The system of claim 1, wherein said counter includes a sensor
selected from photo cells, IR detectors, RF detectors, pressure
plates and a turnstile.
5. The system of claim 1, wherein said processor is further adapted
to adjust the amount of ventilation based on the outside air
temperature.
6. The system of claim 5, wherein first detector further includes a
first filter that passes only said first IR band and said second
detector further includes a second filter that passes only said
second IR band.
7. The system of claim 1, wherein said processor uses the
algorithm: d P CO .times. .times. 2 d t = j CO .times. .times. 2 *
N .function. ( t ) - v CO .times. .times. 2 .function. ( t ) Vol
##EQU2## where dP.sub.CO2/dt is the rate of CO.sub.2 partial
pressure change in the room, V.sub.CO2 (t) is the rate of 300 ppm
CO.sub.2/air ventilation into the room, N(t) is the number of
people in the room as a function of time, and j.sub.CO2 is the
average CO.sub.2 respiration rate of a person.
8. An occupancy based ventilation system for indoor air quality of
a predetermined area, comprising: room ventilation system means for
providing outdoor air to said predetermined area; counter means for
counting the number of persons in said area and the amount of time
each person remains in said area, said counter producing a signal
representing the sum of the number of persons times the amount of
time for each person; and processor means for adjusting said
ventilation system for said area based on the signal produced, said
processor being adapted to determine the amount of ventilation
needed to maintain the CO.sub.2 concentration in the room air at a
predetermined level.
9. The system of claim 8, wherein said CO.sub.2 concentration is
500 ppm or less.
10. The system of claim 8, wherein said counter means is positioned
by the entrance to said area.
11. The system of claim 8, wherein said counter means includes a
sensor selected from photo cells, IR detectors, RF detectors,
pressure plates and a turnstile.
12. The system of claim 8, wherein said processor means is further
adapted to adjust the amount of ventilation based on the outside
air temperature.
13. The system of claim 8, wherein said processor means is further
adapted to adjust the amount of ventilation based on the air
temperature in the room.
14. The system of claim 8, wherein said processor means uses the
algorithm: d P CO .times. .times. 2 d t = j CO .times. .times. 2 *
N .function. ( t ) - v CO .times. .times. 2 .function. ( t ) Vol
##EQU3## where dP.sub.CO2/dt is the rate of CO.sub.2 partial
pressure change in the room, V.sub.CO2 (t) is the rate of 300 ppm
CO.sub.2/air ventilation into the room, N(t) is the number of
people in the room as a function of time, and j.sub.CO2 is the
average CO.sub.2 respiration rate of a person.
15. A method for controlling indoor air quality of a predetermined
area having a room ventilation system for providing outdoor air to
said predetermined area, comprising the steps of: positioning a
counter for counting the number of persons in said area and the
amount of time each person remains in said area, and producing a
signal representing the sum of the number of persons times the
amount of time for each person; and adjusting said ventilation
system for said area based on the signal produced using a
processor, said processor being adapted to determine the amount of
ventilation needed to maintain the CO.sub.2 concentration in the
room air at a predetermined level.
16. The method of claim 15, wherein said CO.sub.2 concentration is
500 ppm or less.
17. The method of claim 15, wherein said counter is positioned by
the entrance to said area.
18. The method of claim 15, wherein said counter includes a sensor
selected from photo cells, IR detectors, RF detectors, pressure
plates and a turnstile.
19. The method of claim 15, wherein said processor adjusts the
amount of ventilation based on the outside air temperature.
20. The method of claim 15, wherein said processor adjusts the
amount of ventilation based on the air temperature in the room.
21. The method of claim 15, wherein said processor uses the
algorithm: d P CO .times. .times. 2 d t = j CO .times. .times. 2 *
N .function. ( t ) - v CO .times. .times. 2 .function. ( t ) Vol
##EQU4## where dP.sub.CO2/dt is the rate of CO.sub.2 partial
pressure change in the room, V.sub.CO2 (t) is the rate of 300 ppm
CO.sub.2/air ventilation into the room, N(t) is the number of
people in the room as a function of time, and j.sub.CO2 is the
average CO.sub.2 respiration rate of a person.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to room ventilation systems.
More particularly, the invention relates to an occupancy based
system in which the amount of ventilation is determined by the
number of persons in the area under consideration, such as a
meeting room and the like.
BACKGROUND OF THE INVENTION
[0002] With the energy crisis looming and with expectations that
energy costs will be increasing, efficient indoor air quality
control is highly desired. A well controlled room allows the
occupants to be comfortable and thus more efficient. In a meeting
room, for example, as the meeting proceeds, the temperature,
CO.sub.2 concentration, humidity, and body odor all increase with
time. Working efficiency in this environment can be low as
discomfort increases.
[0003] One possible solution to this concern would be to assemble
an array of sensors that would provide data as to each parameter,
and have a controller adjust ventilation and heat or cooling as
needed. This would involve a large expense, of course, since each
sensor would have to be installed in the room and a microprocessor
or other controller would then adjust the flow of air and the
temperature as indicated by the sensors.
[0004] Another factor in room air quality is the number of people
in the room at any one time. More persons means more CO.sub.2 being
produced as the people breathe. Typical sensor based solutions do
not take into account the number of persons in the room.
[0005] It would be a great advantage in the art if a simpler, more
economic solution to the concerns over room quality could be
provided.
[0006] Yet another advantage would be if an energy efficient indoor
air quality control solution could be provided that uses a sensor
that adjusts the amount of ventilation based on a simple
measurement such as the number of persons in the room.
[0007] A particular advantage in room ventilation control would be
a system that takes into account the number of persons entering and
leaving a room as well as the degree of activity in the room.
[0008] Other advantages will appear hereinafter.
SUMMARY OF THE INVENTION
[0009] It has now been discovered that the above and other
advantages of the present invention may be obtained in the
following manner. Specifically, instead of sensing a plurality of
variables, it has been discovered that a correlation between the
number of people in a room and the length of time they are present
provides an accurate picture of the ventilation requirements of the
room.
[0010] This discovery is based on the knowledge that the metabolism
of an average person is more or less the same as any other average
person. Thus, it has been discovered that the number of people
correlates closely to the CO.sub.2 that they generate. A feedback
control algorithm between the counting device and the ventilation
management device allows the system to tune ventilation of the room
to the number of people present at any given time.
[0011] The occupancy based ventilation system for indoor air
quality of a predetermined area adjusts the room ventilation system
for providing outdoor air to the predetermined area as needed and
as determined by the CO.sub.2 concentration in the room as it is
used by the number of people in the room.
[0012] The system includes a counter for counting the number of
persons in the area and the amount of time each person remains in
the area. The counter produces a signal representing the sum of the
number of persons times the amount of time for each person. The
counter is positioned by the entrance to the area. The counter may
use any sensor that is capable of identifying the entrance or
egress of a person. Preferred sensors are selected from photo
cells, IR detectors, RF detectors, pressure plates and a
turnstile.
[0013] The system also includes a processor that adjusts the
ventilation system for the area based on the signal produced. The
processor determines the amount of ventilation needed to maintain
the CO.sub.2 concentration in the room air at a predetermined
level. The preferred CO.sub.2 concentration is 500 ppm or less. In
a preferred embodiment, the processor is further adapted to adjust
the amount of ventilation based on the outside air temperature or
based on the air temperature in the room.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0014] The present invention operates as a system in which the
amount of CO.sub.2 present in the room is determined as a function
of the number of people in the room and the length of time each is
present. The sum of person-time is directly proportional to the
increase in CO.sub.2 that the persons produce simply by exhaling.
Presented below in Table I, the amount of CO.sub.2 produced per
individual is shown for an enclosed area or room depending on the
activity of the person. More work produces more CO.sub.2.
TABLE-US-00001 TABLE I Activity Metabolic Rate (W) CO.sub.2
Sedentary work 100 0.004 Light work 100-300 0.006 Moderate work
300-500 0.012 Heavy work 500-650 0.020 Very heavy work 650-800
0.026
[0015] The present invention regulates the amount of outside air
that the ventilation management system brings into the room.
Ventilation air or outside air has a CO.sub.2 concentration
normally of about 300 ppm. The maximum desirable concentration in
the room should be 500 ppm or lower a counter for counting the
number of persons in said area and the amount of time each person
remains in said area, said counter producing a signal representing
the sum of the number of persons times the amount of time spent in
the room for each person. The processor adjusts the ventilation
system controls based on the signal produced according to an
algorithm, such as: d P CO .times. .times. 2 d t = j CO .times.
.times. 2 * N .function. ( t ) - v CO .times. .times. 2 .function.
( t ) Vol ##EQU1## where dP.sub.CO2/dt is the rate of CO.sub.2
partial pressure change in the room, V.sub.CO2 (t) is the rate of
300 ppm CO.sub.2/air ventilation into the room, N(t) is the number
of people in the room as a function of time, and j.sub.CO2 is the
average CO.sub.2 respiration rate of a person (assumed to be
constant and independent of specific individuals).
[0016] The particular processor will be programmed to make the
appropriate calculations and send a signal to the ventilation
system for the room. Using the present invention allows the
elimination of many sensors that would otherwise be needed to sense
temperature, CO.sub.2 concentration, humidity, body odor and the
like. By simply counting each and every time a person goes into and
out of the room, and since the metabolism of an average person is
more or less the same, the summed number of person/time units is
correlated to the CO.sub.2 generation rate and the room can be
maintained at an efficient and comfortable atmosphere.
[0017] While particular embodiments of the present invention have
been illustrated and described, it is not intended to limit the
invention, except as defined by the following claims.
* * * * *