WO2000039506A1

WO2000039506A1 - Computer controlled method and system for controlled natural ventilation of a building

Info

Publication number: WO2000039506A1
Application number: PCT/DK1999/000732
Authority: WO
Inventors: Mads Hejrskov Pedersen
Original assignee: Vkr Holding A/S
Priority date: 1998-12-23
Filing date: 1999-12-23
Publication date: 2000-07-06
Also published as: WO2000039506A9; AU1857700A

Abstract

Controlled natural ventilation of one or more ventilation zones in a building is carried out by adjustment of passive ventilation devices, e.g. windows, according to a control strategy comprising periodically repeated estimation of a ventilation demand of a zone from a physical parameter for the zone, a desired value of the indoor temperature of the zone and the actual indoor and outdoor temperatures, correction of the estimated demand in dependence of additional indoor climate variables to determine an adjustment factor for each ventilation device, individual correction of the adjustment factors for the individual ventilation devices in dependence of additional outdoor climate variables and/or a possible user actuated adjustment of a ventilation device, and supply of the individually corrected adjustment factors for operator units for the ventilation devices for adjustment of air supply to the zone by opening and closure of said devices. To carry out the method, a computer controlled system comprises a control unit common to the ventilation devices in one zone and connected with sensors for outdoor and indoor climate variables and with an individual operating unit for user actuated control and comprising intelligent self-learning control means for processing information derived from the user controlled adjustment.

Description

computer controlled method and system for controlled natural ventilation of a building

The present invention relates to a computer con- trolled method for controlled natural ventilation of one or more ventilation zones in a building by adjustment of passive ventilation devices associated with such a zone, said device being further adjustable by individual user actuation. Computer controlled methods and systems for heating, ventilation and air conditioning in buildings are well known and conventionally based on the use of active heating, ventilation and air humidity control devices. Various designs of such systems are described e.g. in US-A-4 , 567 , 939 , US-A-4 , 931, 948 , US-A-5 , 215 , 498 , US-A-5,348,078, US-A-5 , 803 , 804 , DE-A-196 00 694 and EP- A-0 585 133.

It is well-known that such an active indoor climate adjustment does usually not function in the best possible way under variable outdoor climate conditions and furthermore is attended by a considerable energy consumption.

On this background, recent years have shown an increased interest for using controlled natural venti- lation for indoor climate adjustment. By controlled natural ventilation is in this connection meant adjustment of the indoor climate in a building by use of natural variation in outdoor and indoor climate variables and by ventilation air supply through adjustable openable parts or sections of building facades. Such openable ventilation devices are typically window sections in the building facades, however, they may also comprise other forms of openable facade parts, such as adjustable ventilation dampers, grids and similar devices. Experimental projects to illustrate the possibilities of natural indoor climate adjustment by use of intelligent computer systems are described e.g. by J. I. Kindangen in his report "Artificial neural network and naturally ventilated buildings" in Building Research and Information, Vol. 24, no. 4, 1996, and by D. Azzi, G. S. Virk, A. K. M. Azad and D. L. Loveday in a conference paper "Towards the "intelligent building"" at the 18th AIVC Conference in Greece in 1997, whereas control strategies herefor are described by A. J. Martin in "Control of Natural Ventilation", BSRIA Technical Note TN 11/95. The purpose of these experiments has essentially been to describe different parameter models for pure computer controlled adjust- ment of various forms of adjustable heating, ventilation, shading and humidity control devices.

US-A-5 , 226 , 256 discloses a method of the above type, by which passive ventilation devices in the form of windows can by means of sensors adapted for the purpose be adjusted in dependence of indoor climate variables, such as temperature, relative air humidity and C0₂ content and external parameters as for instance noise conditions in the surroundings and the airflow velocity near a window. For this adjustment each window is associated with a microprocessor which can also be controlled from a portable or stationary remote control unit just as all windows can be controlled jointly from a central control unit in a control room.

On the basis of this prior art, the object of the invention is essentially to provide a method for automatic computer controlled natural ventilation of buildings with an improved individual adjustment of the ventilation devices in a building zone such that also individual human demands to a comfortable indoor climate are considered to a larger extent. Therefore, a computer controlled method of the stated kind according to the invention is characterized by comprising following steps periodically repeated estimation of a ventilation demand of a zone from a physical parameter for the zone, a desired value of the indoor temperature of the zone and the actual indoor and outdoor temperatures, correction of said estimated demand in dependence of additional indoor climate variables to determine an adjustment factor for each ventilation device in the zone, individual correction of said adjustment factor for the individual ventilation devices in dependence of additional outdoor climate variables and/or a possible user actuated adjustment of a ventilation device, and supply of said individually corrected adjustment factors for individual operator units for the ventilation devices associated with the zone for adjustment of air supply to the zone by opening and closure of said devices.

Tests with pilot systems according to the invention have proved that by a computer controlled adjustment of the ventilation through openable, operator- driven window sections, it is possible to obtain a surprisingly good indoor climate comfort with considerable options for individual variations.

As will appear from the following description, the hardware demands to a system according to the invention are relatively modest, as electrically driven window operators for continuous variable adjustment of the air flow area of openable window sections are well known components which can be produced with a high degree of adjustment accuracy and reliability, and furthermore, the system requires merely computer hardware and outdoor and indoor climate sensors known per se . Advantageous embodiments of the method according to the invention are stated in the dependent claims 2- 7.

To carry out the method, the invention further relates to a computer controlled system for controlled natural ventilation of a building, in the facades of which a number of adjustable passive ventilation devices with associated operators are installed for natural ventilation, the system comprising, for one or more ventilation zones in the building, control means for said operators for adjustment of the associated ventilation devices in dependence on both outdoor and indoor climate variables and for user controlled adjustment of one or more ventilation devices in the zone by local operation of the operators associated with said devices.

According to the invention, this system is characterized in that said control means comprise a control unit common to the ventilation devices in one zone and containing stored adjustment data for the ventilation devices associated with the zone and connected partly to sensors for outdoor temperature, wind velocity and wind direction together with indoor climate sensors in the relevant zone, partly to an individual operating unit for said user controlled adjustment, the control unit comprising intelligent, self-learning control means for processing information derived from said local operation for update of said stored adjustment data . In a preferred embodiment of the system, the intelligent, self-learning control means comprises a neural network; however, it may also be of the type fuzzy logic control or generic algorithm control.

Further advantageous features of the system are indicated in dependent claims 10-13. In the following, the invention is explained in more detail with reference to the schematic drawing where

Fig. 1 shows in connection with a cross section of a building an embodiment of a computer controlled system according to the invention for controlled natural ventilation of one single zone in a building,

Fig. 2 illustrates an example of a software based control strategy to carry out the method according to the invention,

Fig. 3 is a simplified schematic block diagram for a control unit in the system in Fig. 1,

Fig. 4 shows graphic displays of representative combinations of indoor climate variables when imple- menting the control strategy illustrated in Fig. 2,

Fig. 5 shows an example of the adjustment ability of an indoor climate variable in dependence on the outdoor temperature,

Fig. 6 shows an embodiment of controlled natural ventilation of more zones in a major zone-divided building with a central monitoring and control unit, and

Fig. 7 is a modification of the system in Fig. 6 for ventilation of closed individual rooms in a major building.

In the cross section of a building 1 shown in Fig. 1, the weather shield of which is shown by a dashed outline, a ventilation zone 2 is provided with a number of adjustable, passive ventilation devices in the form of openable facade windows 3 and a likewise openable roof window 4.

Opening and closure of the openable frame sections of the windows 3 and 4 are effected by electrically driven window operators 5 which can be of a conven- tional design, e.g. in the form of chain operators. The operators 5 are individually actuated by control via an appropriate interface from a control unit 6 in the form of a climate computer which can be designed as a conventional PC. The control is carried out on basis of information on outdoor climate variables transmitted to the control unit 6 from a weather station 7, and indoor climate variables transmitted to the control unit 6 from an indoor climate station 8. The outdoor climate variables transmitted to the control unit 6 from the weather station 7 may, in addition to the outdoor temperature which is mandatory and e.g. used for finding a seasonal adjustment of the influence from other outdoor and/or indoor climate variables, typically comprise wind velocity and wind direction and perhaps data on relative air humidity, atmospheric pollution, pollen count, noise conditions in the surroundings of the building, e.g. high onesided nuisance of traffic noise etc. The indoor climate variables transmitted to the control unit 6 from the indoor climate station 8 may, in addition to the actual indoor temperature which is mandatory, comprise other indoor climate data, e.g. air quality data, typically in the form of content of C0₂, internal air current velocity as an expression for draught, and relative air humidity.

According to the invention, the automatically effected indoor climate control based on regularly repeated measurements of the said indoor and outdoor climate variables in order to obtain an optimal user comfort can be superposed or overrided by an individual user actuated impact of the individual operators 5.

In a relatively simple installation as shown in Fig. 1, this individual user actuation can be effected from an operating unit, e.g. a keyboard in direct connection with the control unit 6 if this is accessible for the individual users.

As an often more convenient alternative, one or more individual operating units, e.g. in the form of a fixed operating keyboard 9 or a remote control unit 10, can be provided in association with the control unit 6 in order, perhaps with associated user identification, partly to affect the individual operators 5 in an addressable manner, partly to update information in the control unit. For the data communication between the units 5-9, bus connections can be used in configurations known per se which may also be used for other data communication purposes in the building 1 or the zone 2. As shown in the flow diagram in Fig. 2, the indoor climate control by the system according to the invention is based on a control strategy where an estimated ventilation demand is first calculated from a fixed physical parameter for the ventilation zone 2, e.g. its cubic content, a prestored desired value for the indoor temperature, and measured values of the indoor and outdoor temperature .

The estimated ventilation demand Q_v in m³/s can e.g. be calculated according to the algorithm

Q_v = C V_zone(T_i/ref - i) ( _U - T_i<ref),

where V_zone is the cubic content of the zone in m³ , T_j_ _ref the adjusted desired value of the indoor tempera- ture, T± and T_u the measured values of the indoor and outdoor temperatures, respectively, and C a constant with the dimension s"¹.

The estimated ventilation demand is then corrected in dependence of variable indoor climate parameters as for instance draught stemming from open doors, and/or inferior air quality in the form of e.g. high C0₂ content to determine a corrected ventilation demand and on this basis an adjustment factor for the operators 5 for the windows 3 and 4 in the zone 2. This adjustment factor is then corrected separately for the individual operators 5 by combining additional indoor climate variables, in particular those related to wind, typically wind velocity and wind direction, having different effects on the windows 3 and 4 depending on their location in facade and/or roof and orientation in relation to the wind direction, and registration of an individual user actuated adjustment of one or more operators made since the latest automatic adjustment. In this way, the automatic indoor climate control is constantly adjusted to an optimum according to the users' individual needs.

To ensure functional stability so that frequent fluctuations in the adjustment are avoided, the adjust- ment factors are corrected for the individual operators 5 as shown in the schematic block diagram of the control unit 6 in Fig. 3 by processing possible user identified information on individual user actuation in an intelligent self-learning control means, here exemplified by a neural network 11 in the control unit 6 even though other forms of intelligent control means as e.g a fuzzy logic control or a genetic algorithm control may also be used.

Such intelligent control means are described in the literature, e.g. in an inaugural lecture by professor Gurvinder S. Virk, "Control; The enabling Technology", University of Portmouth, 22 May 1997, and concerning neural networks also in aforesaid report by J. Kindangen. The correlation made in the neural network 11 assures that by calculation of adjustment factors for the individual operators 5 as a consequence of self- learning abilities of the neural network, the automati- cally calculated, estimated and herefrom derived corrected ventilation demand is continuously adapted to the verified needs of the users, and at the same time a satisfactory functional stability is obtained, so that frequent readjustments by the users are avoided. As the individual adjustment factors for the operators 5 determine data for opening the individual window to the air flow area which is to be adjusted to meet the user-adapted ventilation demand, the control unit 6 contains, as shown in Fig. 3, a memory 12 with stored data for the individual windows 3 and 4 and the associated operators 5 such that on the basis of the individual adjustment factors in a command unit 13 operator control signals can be determined to effect a corresponding actuation of the linkage mechan- ism of each operator, e.g. the chain in a chain operator.

As appears from Fig. 3, the registered measured values of outdoor climate variables comprising outdoor temperature, wind velocity, wind direction and perhaps air humidity, noise and pollution data such as pollen count from the weather station 7 are transmitted to an interface unit 14 in the control unit 6, to which also registered measured values of indoor climate variables comprising indoor temperature, draught and C0₂-content are transmitted from the indoor climate stations 8, whereas a desired value for the indoor temperature is added as a reference value, e.g. from a keyboard in direct connection with the control unit 6. From the interface unit 14, the various data and information are transmitted to a processor unit 16 which furthermore via the neural network 11 receives the adjustment data stored in the memory 12 for the ventilation devices of the zone, in this case the facade windows 3 and the roof window 4 with the associated operators 5. In addition to the fixed data for the individual windows which may comprise the dimensions of the window and the air flow area in various opening positions to be occupied by the window, the stored data comprise exact logging information on the position of the window both at the latest adjustment ordered by the control unit 6 and in the immediate position which e.g. can be modified as a conse- quence of a local user actuation of a certain window.

Such position data concerning local user actuation can be transmitted to the control unit 6 directly from the individual operating unit or units or may alternatively be generated by the operators for the individual windows because position data for the openable part of the window can relatively easy be derived from the immediate position of the linkage mechanism, e.g. the chain in a chain operator, and transmitted to the memory 12 in the control unit 6 via an interface unit 15.

The information processed in the neural network 11 is transmitted together with the measured values for the outdoor and indoor climate variables to the processor unit 16 which calculates estimated ventila- tion demands and corrections hereof together with individual adjustment factors for the ventilation devices of the zone in accordance with the control strategy chosen for the system as e.g. illustrated in Fig. 2. In order to avoid unnecessary frequent adjustments, the control strategy can be implemented through selected combinations of the added outdoor and indoor climate variables which are representative situations common in practice. An example hereof is illustrated in Fig. 4.

By a) is shown a temperature diagram for the indoor temperature with four temperature bands A, B, C and D separated by the desired value T_ref indicated to the control unit 6 and an upper and a lower limit T_max and T_min, respectively, for an acceptable indoor climate temperature. The temperature values T_ref, T_max and ^τmin ^can vary, e.g. depending on the season.

By b) is shown a corresponding diagram for the air quality represented by the C0₂ content of the indoor air with indication of an upper limit value C0_2/max, whereas c) shows a corresponding diagram for movement in the indoor air expressed as draught with un upper limit value D_max. The level of the individual threshold values will typically be depending on the season, as e.g. movement in the indoor air is usually considered to be positive at high summer outdoor temperatures, whereas at low outdoor temperatures during winter term, it is as a rule felt as unpleasant draught. The levels applying at any time of the individual threshold and limit values may therefore typically be adjusted in dependence of the outdoor temperature. As an example there is in Fig. 5 shown the draught threshold value D_max, depending on the outdoor temperature. The adjustment situations illustrated in Fig. 4 can by appropriately chosen combinations cause various forms of adjustment of opening and closure of the windows. At indoor temperatures in the bands A and D, all windows will thus typically be closed, if they are already open, and opened, if they are already closed, respectively. In the acceptable indoor temperature interval, an adjustment, e.g. at low outdoor temperature, will typically depend on the air quality determined by the C0₂ content such that e.g. when exceeding the limit value C0_2/max in the temperature interval, closed windows will be opened with a predetermined duration for the opening corresponding to accomplishment of a desired air change until reclosure of the window. If the draught threshold value D_max is exceeded, a partial closure of open window may be effected even in the temperature interval D. Vice versa in the summer period depending on the actual outdoor temperature, the windows may be opened in the temperature interval B to increase the inner air movement . The examples illustrated in Figs. 4 and 5 are merely representative possibilities of use when implementing the control strategy illustrated in Fig. 2. The natural ventilation according to the method provided by the invention may thus e.g. for office buildings and alike also comprise an automically effected 24-hour operation, by which one or more windows or other ventilation devices in a ventilation zone are opened with a predetermined duration in a period of time where there are generally no people in the zone in question. For a building zone as shown in Fig. 1 with windows in both sides of the building, the control strategy can furthermore be implemented either by opening of the windows only in one side, e.g. with considerable noise or wind problems, by opening of windows in the other side or by opening of windows in both sides. In the first case, the adjustment situations requiring opening of the windows will typically result in an opening for larger air flow area than in the last case . In the embodiment shown in Fig. 6, a major office building 17 comprises a number of ventilation zones 18, 19 and 20, each of which can be designed as shown in Fig. 1 such that each zone is provided with a local control unit 21 and an indoor climate station 22 and a number of window operators 23. However, in this case, a weather station 24 is connected to a central common control unit 25 which through a network transmits outdoor climate information to the control units 21 of the individual zones. In the central control unit 25, the wind related data might be processed under consideration of the architecture of the building and its influence on the individual ventilation zones. The central control unit 25 can in this connection be associated with a common overall energy monitoring and control system of the type BEMS (Building Energy Management System) which also monitors control of the power consumption and perhaps artificial venti- lation (mechanical ventilation and/or air conditioning) in parts of the building. The control strategy of the system according to the invention may thus be provided with power consumption related limit values which in certain cases limit or prevent the adjustment of openable windows.

In the embodiment in Fig. 7, natural ventilation in a number of separate individual rooms 26, 27 and 28 in a major building 29, e.g. class rooms in a school or individual offices in an office building, is pro- vided by means of a common control unit 30 with associated weather station 31 for a number of such individual rooms, however, with an indoor climate station 32 and one or more individual control units 33 in each of the rooms. Whereas the natural ventilation according to the invention mainly aims at the adjustment of the supply of fresh air to the ventilated zone or zones, the air may be evacuated from these zones by means of conventional vent installations, including natural ones, just as the natural ventilation according to the invention can be combined with mechanical ventilation systems and various forms of air conditioning systems in hybrid ventilation systems.

Claims

P A T E N T C L A I M S

1. A computer controlled method for controlled natural ventilation of one or more ventilation zones in a building by adjustment of passive ventilation devices associated with such a zone, said device being further adjustable by individual user actuation, c h a r a c t e r i z e d by following steps periodically repeated estimation of a ventilation demand of a zone from a physical parameter for the zone, a desired value of the indoor temperature of the zone and the actual indoor and outdoor temperatures, correction of said estimated demand in dependence of additional indoor climate variables to determine an adjustment factor for each ventilation device in the zone, individual correction of said adjustment factor for the individual ventilation devices in dependence of additional outdoor climate variables and/or a possible user actuated adjustment of a ventilation device, and supply of said individually corrected adjustment factors to individual operator units for the ventilation devices for adjustment of air supply to the zone by opening and closure of said devices.

2. A method according to claim 1, c h a r a c - t e r i z e d in that individual correction of said adjustment factors in dependence of user actuated adjustment of a ventilation device associated with the zone is effected by intelligent self-learning control comprising update of stored adjustment data for the ventilation devices of the zone in a control unit for the zone.

3. A method according to claim 1 or 2 , c h a r a c t e r i z e d in that the corrected adjustment factor for the operating unit of a ventilation device comprises data for opening the ventilation device for a desired air flow area.

4. A method according to claim 1, 2 or 3, c h a r a c t e r i z e d in that the corrected adjustment factor for the operating unit of a ventilation device comprises data for desired duration of the opening until reclosure of the ventilation device.

5. A method according to claim 2, 3 or 4, c h a r a c t e r i z e d in that calculation and correction of said ventilation demand and/or adjustment factor are carried out within intervals limited by adjustable threshold values for indoor and outdoor temperatures and said additional indoor climate variables.

6. A method according to any of the claims 2-4, c h a r a c t e r i z e d in that it comprises a 24- hour control with night ventilation.

7. A method according to any of the preceding claims, c h a r a c t e r i z e d in that said additional indoor climate variables comprise draught and C0₂ content .

8. A method according to any of the preceding claims, c h a r a c t e r i z e d in that said additional outdoor climate variables comprise wind velocity and wind direction.

9. A computer controlled system for carrying out the method according to any of the preceding claims by controlled natural ventilation of a building (1, 17, 29) , in the facades of which a number of adjustable passive ventilation devices (3, 4) with associated operators (5, 23) are installed for natural ventilation, the system comprising, for one or more ventila- tion zones (2; 18-20; 26-28) in the building, control means (6, 21, 30) for said operators for adjustment of the associated ventilation devices in dependence on both outdoor and indoor climate variables and for user controlled adjustment of one or more ventilation devices in the zone by local operation of the operators associated with said devices, c h a r a c t e r i z e d in that said control means comprise a control unit common to the ventilation devices in one zone and containing stored adjustment data for the ventilation devices associated with the zone and connected partly to sensors (7, 24, 31) for outdoor temperature, wind velocity and wind direction together with indoor climate sensors (8, 22, 32) in the relevant zone (2,

18-20, 26-28), partly to an individual operating unit

(9, 10; 33) for said user-controlled adjustment, the control unit (6, 21, 30) comprising intelligent, self- learning control means (11) for processing information derived from said local operation for update of said stored adjustment data.

10. A system according to claim 9, c h a r a c t e r i z e d in that said control means (11) com- prises a neural network.

11. A system according to claim 9 or 10, c h a r a c t e r i z e d in that said individual operating unit comprises an operating keyboard (9, 10) in communication connection with the control unit (6) .

12. A system according to any of the claims 9, 10 or 11, c h a r a c t e r i z e d in that said control unit (30) is common to a number of separate individual rooms (26, 27, 28) in a building (29) .

13. A system according to any of the claims 9-12, c h a r a c t e r i z e d in that said control unit

(21) is connected to a central monitoring and control unit (25) for the building (17)

14. A system according to any of the claims 9-13, c h a r a c t e r i z e d in that the ventilation devices (3, 4) comprise openable windows with associated window operators .