Demand Controlled Ventilation System with Central Air Quality Measurement and Method Herefor
The invention describes an outlet system in which a characteristic of one of gas and/or a liquid, for example the percentage CO2 in air, is measured in a central outlet duct (2). The outlet system comprises local outlet ducts (5, 6, 7) that are in flow communication with the central outlet duct (2). The flow through the local outlet ducts is partly determined by corresponding flow regulators (25, 26, 27) By means of selective setting of these flow regulators by a control system (22) the local value of the characteristic can be calculated using measured values in the central outlet duct (2) and the positions of the flow regulators (25, 26, 27). By means of the invention costs of sensor controlled ventilation systems, in, for example, residential and utility building, are reduced.
The invention relates to a ventilation system for extracting air from a number of spaces, comprising:
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- a central exhaust duct and a number of local exhaust ducts that are in flow communication with the central exhaust duct;
- a measurement device for measuring a characteristic of the air;
- a number of flow regulators, each arranged to determine a flow rate in a local exhaust duct;
- a control system arranged to control the measurement device and the flow regulators.
A ventilation system of this type is described in the patent publication WO 02/41095. In WO 02/41095 a ventilation system is described in which the air quality in various spaces in a building is measured with the aid of one central measurement system. The measurement system is connected to a separate duct system where each duct opens into a specific space for which the air quality has to be measured. The measurement system takes samples of the air in each space and analyses the samples. If the air quality is not good, measures are taken by a conditioning system. Because with such a ventilation system the amount of air is determined on the basis of the demand for fresh air, such a ventilation system is also referred to as a demand controlled ventilation system. The duct system for the measurement system is separate from the actual ventilation system. Thus, a separate pipe system has to be installed for this measurement system. This technology is thus not very suitable for existing buildings and moreover is expensive so that it is suitable/cost-effective only for large buildings.
Patent publication U.S. Pat. No. 6,425,297 discloses a networked measurement system which comprises a network of tubes which may be installed next to a ventilation system in order to measure a characteristic of an air sample. The measurement system itself is not suitable to ventilate spaces, so it can not be regarded as a ventilation system.
In other known demand controlled ventilation systems use is made of multiple measurement systems that are installed locally in the individual occupied spaces. Each measurement system sends information to a central control system that adjusts the flow rate of air to be supplied for the various spaces on the basis of the air quality measured. Local installation of measurement systems is expensive as far as installation and maintenance costs are concerned.
One aim of the present invention is to provide an outlet system where only one central measurement device and no additional pipe system is needed for measuring the quality of the air.
Said aim is achieved with an ventilation system as claimed by claim 1. In an embodiment the control system is arranged to perform the following steps:
(a) suitable setting of the position of one or more flow regulators at a first setting time;
(b) determination of a first measured value measured at a first measurement time that is later than the first setting time;
(c) calculation of the value of the characteristic of the air in at least one of the local exhaust ducts with the aid of the first measured value.
By means of suitable setting of the position of one or more flow regulators and subsequent measurement of the characteristic of the air in the central exhaust duct the characteristic of the air in the local exhaust ducts can be deduced from the measured value and the positions of the various flow regulators in the local exhaust ducts.
Here the term ‘characteristic’ is understood to mean physical, biological and chemical characteristics or states, such as, for example, the temperature of the air, or the composition thereof. When the term ‘characteristic’ is used below this refers to all possible chemical, physical and biological characteristics and/or states of the air, or a combination thereof, that can be measured by measurement instruments.
One example of a ventilation system according to the invention is an air ventilation system in a building in which, for example, the percentage CO2 in the air in specific spaces is determined. In this case it is assumed that the percentage CO2 in an exhaust duct connected to a space to be ventilated virtually corresponds to the percentage CO2 in that space. By means of central measurement of the percentage CO2 and suitable adjustment of the flow regulators the percentage CO2 in the local ducts (read: exhaust ducts) can be determined and thus also the percentage CO2 in the associated spaces without there having to be a sensor in the various spaces.
In another embodiment the control system is arranged to perform the following steps:
(d) determination of a second measured value measured at a second measurement time that precedes the first setting time;
(e) calculation of the value of the characteristic of the air in at least one of the local exhaust ducts with the aid of the first measured value and the second measured value,
wherein the position of only one flow regulator is set at the first setting time and wherein the value of the characteristic of the air in one of the local exhaust ducts is calculated with the aid of the first and the second measured value.
In this embodiment only one flow regulator has to be changed. The ventilation in the other local exhaust ducts, read spaces, is not influenced by the measurement.
The invention also relates to a method as described in claim 16.
Further advantages and characteristics of the present invention will become clear on the basis of a description of a few embodiments, where reference is made to the appended drawings, where:
The flow rate in the local exhaust ducts 5, 6, 7 is determined by the position of the flow regulators 25, 26, 27 and by the fan 24 which may be present. The presence of a duct such as the intermediate duct 20 has no influence of the functioning of the invention. A duct is referred to as a “local exhaust duct” if this is in flow communication with the central exhaust duct 2 and the flow rate in the duct is determined by a local flow regulator. This local flow regulator does not have to be in the duct. It is conceivable that the flow regulator is positioned in the space that is in flow communication with the local exhaust duct.
The ventilation system 1 furthermore comprises a control system 22 and a measurement device 23, which according to the invention is installed in the central exhaust duct. The measurement device 23 contains, for example, a CO2 sensor or a number of different sensors for measuring several characteristics of air, such as temperature or air humidity. In the same measurement device 23 there can also be a sensor for measuring the amount of air or the flow rate. The control system 22 is arranged to control the measurement device 23 and the flow regulators 25, 26, 27. According to the invention the control system 22 is arranged to record values measured by the measurement device 23 at specific points in time. The control system 22 is arranged to set the positions of the flow regulators 25, 26, 27 and to control the fan 24 that may be present.
The control system can be a computer but can also consist of various interacting computers. The control system can also be completely or partially based on analogue and/or digital techniques. Communication of signals can take place via leads or be wireless.
The ventilation system 1 furthermore comprises a database 21 in which knowledge and experience relating to the ventilation system is stored. Algorithms that make use of such knowledge and experience are also referred to as ventilation protocols. With the aid of various ventilation protocols the control system 22 is able to measure and control the ventilation system in an optimum manner. The possible ventilation protocols are stored in the database 21. Various types of ventilation protocols are discussed in more detail in the description further below.
It will be clear that the invention can also be used in a ventilation system with mechanical outlet and natural inlet of air. In that case a local inlet duct can consist, for example, merely of an inlet grating or a window. It will be possible to use the principle of the invention even with a system which makes use solely of natural ventilation. In that case the central inlet duct 38 and the inlet fan 39 are absent. Usually a sensor that measures the volume flow will then be installed in the central exhaust duct.
An embodiment of the measurement procedure 110 for determining the local values is described in
An example of the abovementioned measurement procedure will now be described with the aid of
(2Vx+3Vy+Vz)/6=53.3
(2Vx+2Vy+Vz)/5=58
(2Vx+Vy+Vz)/4=65
In step 206 it will now be established that sufficient measurements have been carried out. The control system 22 can now calculate the three variables Vx, Vy and Vz using the three abovementioned equations. It follows: Vx=90, Vy=30 and Vz=50 degrees of contamination.
In the above example the positions of the flow regulators were changed in such a way that none of the local exhaust ducts was closed off. The measurements thus do not give rise to an interruption in the ventilation of the spaces concerned. However, it is also possible, for example, to close the flow regulator in duct Y completely at time t1 and to restore this to the original position again at time t3, whilst at that time the flow regulator for duct Z is completely closed. By now performing the same measurements as in the first example, three equations with three unknowns are also produced. The advantage of such a variant is that with a system with a relatively large number of ducts it is still possible to achieve a desired measurement resolution without a highly sensitive measurement installation being required.
In another embodiment the control system 22 sets the position of one or more flow regulators in a suitable manner at a first setting time t1. A first measured value is then determined, measured at a first measurement time t2 that comes after the first setting time t1. The value of the characteristic of the air in at least one of the local exhaust ducts is then calculated with the aid of the first measured value. One example of such an embodiment is that where the control system 22 closes all flow regulators except one at the first setting time t1. A value is then measured at measurement time t2. The measured value W(t2) is now a direct measure for the characteristic of the air to be determined in said one local exhaust duct. In a further embodiment the control system 22 determines a second measured value at a second measurement time to that precedes the first setting time t1. The value of the characteristic of the air in at least one of the local exhaust ducts is then calculated with the aid of the first measured value and the second measured value.
In a simple embodiment the position of only one flow regulator is set at the first setting time t1. The value of the characteristic of the air in one of the local exhaust ducts corresponding to the one flow regulator is now calculated with the aid of the first and the second measured value.
In one embodiment the control system 22 is arranged to control the positions of one or more flow regulators depending on the calculated value(s) of the characteristic of the air in one of the local exhaust ducts and depending on a process parameter. The process parameter is, for example, a threshold value for the characteristic to be measured. If the measured value exceeds an upper threshold value or is below a specific lower threshold value, the control system will start to control the flow regulators. With this arrangement the flow regulators are set in an optimum manner so that the local values in the ventilation system again fall within the desired limits. It is pointed out that the flow regulators are thus controlled by the control system 22 both in the measurement procedure and in the control procedure.
The abovementioned process parameter can also be a specific measurement trend. In this case the measured values are stored and compared over time. If a value of a specific characteristic rises to a relatively large extent, for example, it can then be the case that a specific action has to be taken even before a specific threshold value has been exceeded. For example, if a rapid rise in the air humidity and at the same time a rapid rise in the temperature is measured in a dwelling with a ventilation system according to the invention and no change in the percentage CO2 is measured, it can then be decided with the aid of knowledge of the ventilation system (such as: duct 7 ventilates a bathroom 10) to measure duct 7 first. If it is found by a single measurement of the local value in the duct 7 that the rise in the air humidity and the rise in temperature are mainly caused by activity in the bathroom, the control system will then be able to make adjustments immediately. The other rooms now do not have to be measured. This major advantage is the consequence of the knowledge of the ventilation system and more general knowledge of air quality. This knowledge can be stored in the database 21 in the form of measurement algorithms and/or ventilation protocols. Use can also be made of knowledge of the ventilation system and general knowledge when controlling the flow regulators (thus during the control procedure). Two possible control situations that are possible with the ventilation system according to the invention will be described below.
If the temperature of the outside air in the summer is lower than the temperature of the inside air, ventilation will then be augmented, the temperature in bedrooms being lowered first (down to, for example, 16 degrees or a number of degrees higher than the outside air) and then ventilation in a living room will be augmented. This control is called night cooling. It is also possible that if the temperature of the outside air is at least 2° C. lower than the temperature of the inside air, and the temperature of the inside air is higher than 23° C., ventilation will then be augmented. This control is also called summer cooling.
Measures that have to be carried out by the control system 22 are incorporated in a so-called ventilation protocol in one embodiment. This ventilation protocol can also include, inter alia, the following parameters in addition to the knowledge already mentioned:
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- threshold values for the characteristics to be measured;
- minimum ventilation values per local exhaust duct;
- step sizes for control of the flow regulators.
The threshold values can be dependent on time. One example is the seasonal control where the temperature in a building in the summer may be higher than in the winter. A ventilation protocol can also specify how frequently measurements have to be carried out. Furthermore, it is possible that the protocol contains knowledge on the average number of people in a specific area.
In a further embodiment of the ventilation system according to the invention the control system 22 is arranged to determine the position of one or more flow regulators with the aid of measurements from the past. By storing measurements and controls from the past and performing analyses on these, a control system is able to control increasingly intelligently (that is to say in a more optimum and/or more efficient manner).
It will be understood that variants will be immediately apparent to those skilled in the art on reading the above. Instead of measuring the percentage CO2 in air the air humidity or any other characteristic of air or a combination of characteristics as disclosed in patent publication WO 02/41095 can be measured. It is also conceivable that not all exhaust ducts require a flow regulator. The invention can also be used in systems where one local exhaust duct does not have a flow regulator. Such variants are considered to fall within the scope of the application as described in appended claims.
Claims
1-15. (canceled)
16. Ventilation system (1) for extracting air from a number of spaces (10, 13, 14, 15, 16), comprising: characterised in that the measurement device (23) is installed in the central exhaust duct (2) and that the control system (22) is arranged to determine a sequence for the setting of the position of one or more of said flow regulators (25, 26, 27) and to calculate a value of the characteristic of the air in at least one of the local exhaust ducts (5, 6, 7) with the aid of measured values of said characteristic measured in the central exhaust duct (2) during said sequence.
- a central exhaust duct (2) and a number of local exhaust ducts (5, 6, 7) that are in flow communication with the central exhaust duct (2);
- a measurement device (23) for measuring a characteristic of the air;
- a number of flow regulators (25, 26, 27), each arranged to determine a flow rate in a local exhaust duct (5, 6, 7);
- a control system (22) arranged to control the measurement device (23) and the flow regulators (25, 26, 27),
17. Ventilation system according to claim 16, wherein the control system (22) is arranged to perform the following steps: (a) suitable setting of the position of one or more of said flow regulators (25, 26, 27) at a first setting time (t1);
- (b) determination of a first measured value measured at a first measurement time (t2) that is later than the first setting time (t1);
- (c) calculation of the value of the characteristic of the air in at least one of the local exhaust ducts (5, 6, 7) with the aid of the first measured value.
18. Ventilation system according to claim 16, wherein the control system (22) is arranged to perform the following steps:
- (d) determination of a second measured value measured at a second measurement time (t0) that precedes the first setting time (t1);
- (e) calculation of the value of the characteristic of the air in at least one of the local exhaust ducts (5, 6, 7) with the aid of the first measured value and the second measured value.
19. Ventilation system (1) according to claim 18, wherein the position of only one flow regulator (25, 26, 27) is set at the first setting time (t1) and wherein the value of the characteristic of the air in one of the local exhaust ducts (5, 6, 7) is calculated with the aid of the first and the second measured value.
20. Ventilation system (1) according to claim 18, wherein the control system (22) is arranged to perform:
- N repetitions of steps (a) and (b) so that N measured values are determined, where N is the number of local exhaust ducts, and
- calculation of the value of the characteristic of the air in N local exhaust ducts (5, 6, 7) with the aid of the N measured values.
21. Ventilation system (1) according to claim 16, wherein the positions of the flow regulators are changed in such a way that none of the local exhaust ducts are closed off.
22. Ventilation system (1) according to claim 16, wherein the control system (22) is arranged to determine said sequence for the setting of the position of one or more of said flow regulators (25, 26, 27) with the aid of a measurement algorithm and knowledge of the ventilation system (1).
23. Ventilation system (1) according to claim 16, wherein the control system (22) is arranged to control the positions of one or more of said flow regulators (25, 26, 27) depending on the calculated value(s) of the characteristic of the air in one of the local exhaust ducts (5, 6, 7) and depending on a process parameter.
24. Ventilation system according to claim 23, wherein the process parameter is a threshold value for the characteristic to be measured.
25. Ventilation system (1) according to claim 23, wherein the process parameter is a measurement trend.
26. Ventilation system according to claim 23, comprising an inlet system comprising: wherein the control system (22) is arranged to control the inlet flow regulators (34, 35, 36, 37).
- a number of local inlet ducts (30, 31, 32, 33) for feeding air to a space;
- a number of inlet flow regulators (34, 35, 36, 37), each arranged to determine a flow rate in a local inlet duct (30, 31, 32, 33),
27. Ventilation system (1) according to claim 26, wherein the inlet system comprises a central inlet duct (38) and a fan (39) arranged in the central inlet duct (38).
28. Ventilation system (1) according to claim 23, wherein the control system (22) is arranged to control the positions of the flow regulators (25, 26, 27) with the aid of a ventilation protocol, wherein the ventilation protocol comprises at least one of the following parameters:
- threshold values for the characteristics to be measured;
- minimum ventilation values per local exhaust duct (5, 6, 7);
- step sizes for controlling the flow regulators (25, 26, 27).
29. Ventilation system (1) according to claim 24, wherein the threshold values are dependent on time.
30. Ventilation system (1) according to claim 23, wherein the control system (22) is arranged to determine the position of one or more flow regulators (25, 26, 27) with the aid of measurements from the past.
31. Method for determining a characteristic of air flowing, at least in use, in a ventilation system (1), wherein the ventilation system (1) comprises a central exhaust duct (2) and a number of local exhaust ducts (5, 6, 7) that are in flow communication with the central exhaust duct (2), and a number of flow regulators (25, 26, 27) each corresponding to a local exhaust duct (5, 6, 7), characterised by:
- determining a sequence for the setting of the position of one or more of said flow regulators;
- measurement of a characteristic of air in the central exhaust duct (2);
- calculating a value of the characteristic of the air in at least one of the local exhaust ducts (5, 6, 7) with the aid of measured values of said characteristic measured in the central exhaust duct (2) during said sequence.
32. Method according to claim 31, wherein said method comprises the following steps:
- suitable setting of the position of one or more of said flow regulators (25, 26, 27) at a first setting time (t1);
- measurement of the characteristic of the air in the central exhaust duct (2) at a first measurement time (t2) that is later than the first setting time (t1);
- calculation of a value of the characteristic of the air in at least one of the local exhaust ducts (5, 6, 7) with the aid of a value measured in the central exhaust duct (2).
Type: Application
Filed: May 19, 2005
Publication Date: Aug 14, 2008
Applicant: ITHO B. V. (Schiedam)
Inventor: Arie Boxhoorn (Delfgauw)
Application Number: 11/597,051
International Classification: F24F 11/04 (20060101); F24F 13/08 (20060101);