WO2010061205A9

WO2010061205A9 - Environmental climate control for commercial buildings

Info

Publication number: WO2010061205A9
Application number: PCT/GB2009/051451
Authority: WO
Inventors: Andy Sneyd
Original assignee: Laing O'rourke Plc
Priority date: 2008-11-03
Filing date: 2009-10-28
Publication date: 2010-09-02
Also published as: GB0820094D0; GB2464984B; GB2464984A; WO2010061205A1

Abstract

An energy-efficient climate control system is designed for an enclosed indoor space which has been divided into a plurality of zones in which the heat losses and gains are similar. The system has means for heating and cooling water (106, 112, 124), means for supplying fresh air (128), and a control system (120, 120A, 120B, 50). Each zone is provided with a buffer vessel (122) connected to the water heating means. Each zone is equipped with a plurality of active air terminal devices (4), each having a single pipe element through which water from the buffer vessel is circulated. By controlling the temperature of water within the buffer vessel, the air temperature within each zone can be controlled in an energy efficient manner with temperature differentials between the target temperature within the zone and the water temperature of less than 15°C.

Description

Environmental Climate Control for Commercial Buildings Technical Field

[0001] The present invention relates to environmental temperature or climate control systems for commercial spaces within buildings, such as individual offices, open plan offices and retail environments.

Background Art

[0002] Systems for providing heating, cooling and ventilation within large spaces inside buildings typically use a plant room containing a boiler for heating water for supplying hot water to a heating system and a refrigeration system for supplying chilled water to cooling units. A building management system (BMS) will control the operation of the system and take inputs from temperature and occupancy sensors throughout the building. Large buildings will usually be zoned into areas with similar thermal characteristics. The requirements for heating and cooling within a space depend upon the heat losses and heat gains within that space. The calculation of these losses and gains must take into account external geographic factors such as latitude, altitude, typical wind directions, proximity to water bodies, urban landscape etc; internal factors such as proximity to heat sources such as server rooms and kitchens; human factors including occupancy patterns and the type of activities being undertaken in the space; as well as factors controlled by the design of the building such as the effect of a glass fagade, windows, cladding and insulation.

[0003] Programmed computer control systems are typically used to manage operation of the system.

[0004] An air terminal device is a device that provides climate controlled air within a building space.

[0005] An existing air terminal device for providing heating and cooling is known as a multiservice chilled beam. The device is usually mounted just below, or integrated into, the ceiling of a space. These devices are referred to as multiservice as they provide multiple services such as heating and cooling, fresh air supply, lighting, fire alarms and sprinkler heads within the same unit. Heating and cooling services are provided using separate systems. The heating system will typically require hot water with an initial temperature of between 80 and 70°C and the cooling system cold water at 12°C. Typically in a chilled beam system used in a heating mode the hot water will be first delivered to a plate heat exchanger so that water is delivered to the beam at 50°C referred to as T_{water in} . This stage creates a loss of efficiency in the system and an additional control requirement.

[0006] The use of chilled beams is described in more detail in REHVA - Federation of European HVAC associations. Rehva Chilled Beam Application Guidebook. Edited by VIRTA, Maija. Brussels: REHVA, 2004. p.55. the contents of which are incorporated herein by reference.

[0007] There are active and passive chilled beam devices. An active device will incorporate a fresh air supply, at a temperature designated as T_suppι_y, which passes air over the heating and cooling elements to induce airflow within the space. These elements are metal pipes containing water. The pipes may carry fins or other features to increase a heat exchange surface area between the water in the pipe elements and the surrounding air.

[0008] A chilled beam has no moving parts and is therefore quiet. The device relies on the temperature differential between the temperature of the ambient air being drawn in, designated as T_ref, and the temperature of the heat exchange surface to create convection currents in the air within the space. The flow of introduced air in an active or induction supply device also encourages heat exchange between the ambient air and the water in the heating and cooling elements.

[0009] An example of such an active chilled beam air terminal device is described in EP 1188992 A (FLAKT WOODS AB) 20.03.2002 . This device includes a cooling/heating element through which room air is drawn before being mixed with supply air.

Disclosure of Invention

[0010] The present invention provides a novel environmental climate control system and method of controlling the temperature of environmental air.

Technical Problem

[0011] The invention addresses the technical problem of energy efficiency while ensuring maximum comfort for users of the space.

[0012] Energy losses arise in existing systems due to the requirement to pump both hot and cold water over large distances to each chilled beam valve irrespective of need. Energy is wasted in pumping the water and also as a result of the heat gain or loss in the water circulating in the system outside the chilled beams. In existing systems control flaws can result in water flowing in both the heating and cooling elements of a chilled beam simultaneously. This results in a further waste of energy.

[0013] REHVA have established exacting comfort standards for chilled beam systems which recommend summer and winter values for factors such as the air velocity and vertical air temperature difference which are critical to user comfort within the space. See page 21 of the publication referred to in paragraph [0006].

Technical Solution

[0014] The present invention provides a climate control system for an enclosed indoor space which has been divided into a plurality of zones in which the thermal characteristics are similar, comprising: means for heating and cooling water, means for supplying ventilation air, and a control system; each zone being provided with a buffer vessel for storing temperature controlled water; a plurality of air terminal devices, each having a pipe element with an inlet and an outlet for carrying temperature controlled water from the buffer vessel through the device, and an inlet connection for ventilation air, which flows over the pipe element and induces air flow into the device from an adjacent space; a flow and return pipe system for connecting the buffer vessel to the inlet and outlet of each air terminal device; and a pump for pumping temperature controlled water through the pipe system.

[0015] The invention also provides a method of controlling the temperature of environmental air within a zone of an enclosed indoor space by circulating temperature controlled water from a single source through a single heat exchange pipe element with an inlet and an outlet in each chilled beam device within the zone, where the temperature differential between the target temperature within a zone and the water temperature is less than 15°C.

[0016] It has been found that controlling the temperature of the water in the buffer vessel (designated as T_waterjn), in combination with a single pipe element within the air terminal devices, enables heating to be achieved with a water temperature as low as 30°C and cooling with a water temperature as high as 14°C. A temperature differential between the temperature controlled water and the target temperature within the space (designated as T _room) of 15°C or less, preferably between 8 and 10°C, is employed.

[0017] Preferably the means for heating and cooling water comprises a heat pump connected to the buffer vessel for each zone. This heat pump is preferably a reverse cycle refrigeration unit. Preferably an externally mounted dry air cooler (DAC) is also used to maximise energy efficient heat rejection when conditions permit.

[0018] The system is preferably a variable volume system and to achieve this, a zonal bypass can be provided in the pipe system to permit a minimum flow and return to the buffer vessel when the system is in a neutral condition where neither heating nor cooling is required in the space.

[0019] It is no longer necessary to have heating and cooling valves for controlling the flow of both hot and cold water to each air terminal device.

[0020] Preferably both the temperature controlled water system and the air supply system are variable volume to improve energy efficiency.

[0021] Other features of the invention are set out in the claims.

Advantageous Effects

[0022] Energy savings are delivered by the reduced operating temperatures, improved control and the use of variable volume water and air circulation systems.

[0023] By providing only a single water circuit to each chilled beam, installation and maintenance requirements for the system are reduced. Fewer pipes are needed to connect the system thereby almost halving the amount of materials and labour used in installation. Maintenance costs are also reduced as there are fewer valves and components to fail.

[0024] The reduced temperature differential between the heat exchange element and the ambient air results in improved supply air and ambient air mixing compared to prior art systems, thereby considerably improving comfort levels within the heated space. In winter, where heating is required, the present system can easily achieve the challenging REHVA standards using less energy than existing systems. The comfort levels in summer are comparable with existing operating methods.

[0025] The system also eliminates abrupt changes in mode from cooling to heating and vice versa. Changes in a target temperature within the space will be more gradual when compared with prior art systems. This gradual change helps individuals in that space to acclimatise more readily.

[0026] The system is particularly advantageous in climates where both heating and cooling may be required at different times of the day rather than simply at different seasons.

Brief Description of Drawings

[0027] In order that the invention can be well understood, an embodiment thereof will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:

[0028] Figure 1 shows a diagrammatic representation of an environmental climate control system;

[0029] Figure 2 shows a perspective view of an air terminal device for use in the system of Figure 1 ;

[0030] Figure 3 shows a section through the air terminal device of Figure 2; and

[0031] Figure 4 is a plan view of a test room showing the position of sensors and chilled beams.

Mode(s) for Carrying Out the Invention

[0032] An environmental climate control system is described for a building which has been divided into two zones. Only two zones A and B have been shown for simplicity. It will be appreciated that the number and size of each zone will have been calculated by predicting heat losses and gains within the building so that room spaces with similar thermal characteristics are grouped together into zones. Room spaces within each zone are provided with air terminal devices 4 such as chilled beams. In the illustrated embodiment, each zone has been shown with two distinct room spaces each supplied with four chilled beams 4 and its own control module 50. Control module 50 is connected to a room valve 60 which controls the water flow to the chilled beams in each room space.

[0033] The system has a central plant room 100 and a plant room 102, 104 for each zone. The central plant room contains a boiler 106 connected by means of a low loss header 108 to a hot water vessel 110. A solar collector 112 is mounted externally of the building and water from the hot water vessel 110 is circulated through the solar collector 112. In this embodiment, the combination of the boiler and solar collector provides a central means for heating water.

[0034] A building management system 120 controls the operation of the boiler

106 and solar collector 112 to produce the required temperature controlled water in the most energy efficient manner. The building management system 120 also controls operation of the pumps P which move water around a pipe system which connects the plant room 100 to the zone plant rooms. The building management system and control modules in each room space together constitute a control system.

[0035] Each zone plant room, 102, 104 houses a buffer vessel 122 which is connected by a low loss header 108 to the central boiler 106 and hot water vessel 110. A zonal pump 114 pumps water from the buffer vessel 122 into a flow and return pipe system for that zone. The pump is a variable speed pump. A pressure sensor 116 senses the pressure in the pipe system and is connected to the pump in order to control its speed of operation. Each zone also has a programmable zonal building management system 120A, 120B. The zonal building management system is programmed to control the temperature of the water in the buffer vessel 122 in accordance with the system requirements for that zone and operates in cooperation with control modules 50 in the room spaces within the zone and provides feedback to the central building management system 120. [0036] A heat pump 124 is connected to the buffer vessel and controlled by the zonal building management system 120B. This heat pump is a reverse cycle refrigeration unit. The unit may be of any conventional design. It is mounted externally and under the control of the zonal building management system 120B can be used for heating or cooling water circulating through it. The water passing through the unit can be cooled by simple heat exchange or when greater cooling effects are needed passed through a motor driven compressor. Such units have a high coefficient of performance, though that does depend on the external conditions where the unit is installed. The unit 124 is used as the means of cooling water in the buffer vessel. In addition a dry air cooler (DAC) unit 123 is connected to the buffer vessel 122 under the control of the zonal building management system 120B. Such a unit can be used to provide cooling in appropriate circumstances and is a more efficient method of maximising heat rejection. For heating, the heat pump 24 is used in preference to the supply of hot water from the plant room. Therefore heat recovered from the atmosphere is used first, then solar heating and only if more heat energy is required is it necessary to resort to the boiler. This control improves energy efficiency and minimises the use of purchased energy.

[0037] The buffer vessel 122 is connected by pipework 125 to a water inlet of every chilled beam 4 in its associated zone. A return path 126 from the water outlet of each air terminal device is also provided to allow the water to return to the buffer vessel 122. This pipework 125, 126 provides the flow and return pipe system for the zone. As shown, the pipe leaving the zonal plant room is 76 mm in diameter and connects via a 42 mm pipe to two 32 mm diameter pipes, which branch off to feed the water inlets of the chilled beams 4 in each of the room spaces. The return path pipe work 126 follows a similar configuration. A by-pass connection 127 allows the flow and return paths to be connected and together with the room valves creates a variable volume system. The by-pass is used to allow a minimum water flow through the system when it is in a neutral condition between heating and cooling when the room valves 60 are closed. As the pump is variable speed, the change in pressure created when water is being fed through the by-pass instead of through the chilled beams is detected by the pressure sensor 116 and used to slow the pump and conserve energy. A filter and commissioning or balancing valves are provided in the pipework in accordance with standard practice.

[0038] The zone plant room also houses an air handling unit 128 for supplying ventilation air to the air terminal devices in that zone by means of ducting 130 which connects to an inlet connection of each air terminal device in the zone. The operation of the air handling unit is also controlled by the building management system as for existing chilled beam systems. The ventilation air supplied by the air handling units 128 will be pre-conditioned to be within a temperature range of, for example, 18 to 20°C. The air supply system is variable volume in order to save energy. Damper valves 132 are provided in the ducting 130 for each room space to cut off the air supply to chilled beams which are not operating. The damper valves 132 are controlled by the respective control modules 50. In addition volume control dampers can be provided at various points in the ducting in accordance with standard practice.

[0039] A distribution board 133 provides electrical power to control modules 50 in each room.

[0040] An external weather sensor 134 provides data on the external temperature to the zonal building management system 120B.

[0041] In the illustrated embodiment, the computers, which provide the building management systems and control modules are wirelessly interconnected. The system may use BACnet - A data communication protocol for building automation and control networks, which is an ISO global standard. The zone modules 50 and building management systems are provided with aerials 140 to allow them to communicate with the network. Additional wireless routers 142 are provided throughout the building.

Air Terminal Device

[0042] The air terminal devices used in the described system are modified versions of standard active chilled beams intended for use in a conventional manner with means for supplying ventilation air. For use in the system of the present invention, the air terminal device requires only a single pipe element for heat exchange purposes. If the system is being retrofitted to an existing system, or standard chilled beams with both heating and cooling pipe element are being used, then the longer cooling pipe element will be used and the shorter heating pipe element will become redundant.

[0043] Each device 4, as shown in Figure 2, has a metal housing 6 with mounting brackets 8. An air inlet connection 10 allows ventilation air supplied via ducting 130 into the housing. The housing, as shown in Figure 3, contains a pipe-element 20 which has a water inlet 22 and a water outlet 24. The pipe element may be in the shape of a coil or a meander. The housing has a bottom plate 26 containing an array of openings 28 through which air can be drawn from the room space up through the pipe element 20. Air outlets 30 are provided in the lower part of the housing to allow air to flow out of the air terminal device. The outlet may be segmented using fins to provide a direction to the out-flowing air. The ventilation air from the inlet connection 10 flows over the pipe element 20 and induces airflow into the device through openings 28 from an adjacent space so that heat exchange can take place between the air and the temperature controlled water in the pipe element. The system can be adapted for various designs of chilled beam, other than the one illustrated, including those where the pipe element is arranged in two regions on either side of a central in-flow path to provide two way air distribution through the device.

[0044] A valve 32 is provided at the connection between the flow pipework 125, and the water inlet 22. A valve 34 is connected between the water outlet 24 and the return pipework 126.

[0045] The air terminal devices used in implementing the system of the invention may employ any of the air flow control features of conventional chilled beams. The design of the pipe element is such as to maximise the heat exchange surface. Because only one pipe element is required there is more space within the housing for fins and other devices for improving heat exchange. The housing, pipework and pipe elements are preferably made of copper. Fins for enhancing the heat exchange surface area may be made of aluminium. [0046] An occupancy sensor is 136 is provided in each room space and is connected via the control module 50 to the valve 60 in the pipework supplying that room space in order to prevent water and air flow to air terminal devices in unoccupied spaces within the zone. Similarly the module 50 will close the damper valve 132 in the ducting to prevent air flow to air terminal devices in the unoccupied space.

[0047] A room temperature sensor 150 for sensing the ambient air temperature within the zone is connected to the control module 50. The control module 50 is connected wirelessly to the zonal building management system 120B and provides feedback on the air temperature within the zone.

Operation of the System

[0048] The control of the system requires control of the temperature of the water within the buffer vessel to achieve the programmed target ambient temperatures within the zone.

[0049] Typically, the target temperature within a zone that is occupied by people will be in the range 20 to 24°C. Heating or cooling may be required to maintain that temperature. At times the system will be in a neutral condition where neither heating nor cooling is required. The control of the present system uses a temperature differential of between 8 and 10°C between the temperature of the water supplied by the buffer vessel and the target temperature to achieve heating or cooling, thereby saving significant amounts of energy without any loss of comfort when suitably programmed. Rather, the gradual changes that are imposed by the lower temperature differential result in improved supply air/ambient air mixing within the environmental space, and therefore improve comfort levels.

[0050] The temperature of the water within the buffer vessel is controlled by the use of the heat pump and the supply of heated water from the plant room 100. The system is either in a heating mode providing water with a positive temperature differential, a neutral mode when there is preferably no water flow through the air terminal devices and a cooling mode where there is a negative temperature differential. Temperature changes within the buffer vessel are managed during the neutral mode. The heat pump unit 124 is used to cool the water and smaller heat losses can be achieved by circulating the water from the buffer vessel through the pipework without allowing it to enter the air terminal devices. This requires the control means to close control valves 60 so that the water will pass directly from the flow to the return paths by the bypass connection 127. The dry air cooler/free cooling element 123 may also be used to assist with the temperature change.

[0051] The parameters which the programmer of the control system for a zone has under his control in order to achieve the desired target temperature at a specified time include the temperature of the water in the buffer vessel, and the time during which water is pumped into the chilled beams and the water flow rate. The airflow rate is usually constant but also affects the capacity. Because changes will be more gradual, the BMS controls 120, 120A and120B include "optimum start" and "optimum stop" functions that determine the optimum start and stop times for the anticipated occupancy period. The efficiency of the system will also depend on accumulating data on external conditions and the heat gains and losses within each room space so that demands can be predicted in advance.

[0052] For heating, the temperature of the water in the buffer vessel is controlled by replacing water in the buffer vessel with water from the hot water vessel 110 at an appropriate rate depending on the temperature required in the buffer vessel and the temperature of the water in hot water vessel. The heat pump unit 124 controls and maintains the required water temperature in the buffer vessel, in the same way as in the cooling mode of operation.

Test Results

[0053] A test was carried out using a test room space as illustrated in Figure 4 of dimensions 6 x 4.5 x 2.7m with two chilled beams 4 mounted 1200 mm from the walls of the room. The chilled beams were used with the water flow connected at all times to the longer element usually used for cooling. The test room was in a laboratory so that the floor and a fagade wall 151 could be heated to simulate different conditions. Three 150W heat sources 152 were spaced within the room space at floor level to represent occupied workstations.

[0054] All temperatures were measured with Pt-100 sensors. Measured temperatures are:

[0055] T_{water ιn} the water temperature into the element of the chilled beam [0056] T_{water, out} the water temperature leaving the element of the chilled beam [0057] T_room the mean room temperature, which was taken as the mean value of three temperature sensors 154 at a height of 1.1 m. [0058] T_SUppi_y the temperature of the ventilation air [0059] Vertical temperature gradients were measured using 6 sensors 156 placed at heights of 0.10m, 0.6m, 1.1 m 1.8m, 2.3m and 2.5m. [0060] T_ref the reference temperature of the air below the chilled beam that is drawn up from the space. This was measured by an average value of three temperature sensors 158. [0061] The air velocity/flow pattern within the room was tested using the DANTEC

^®54N10 system. 18 probes were mounted on 6 sticks 160 at three heights of 0.1 , 1.1 and 1.8m. The sticks were moved manually around the room to different positions as shown in Figure 4.

Test Settings

Case 1 : Heating mode

[0062] In this test the fagade wall of the room was set to cool down the room using lOOOWatt. [0063]

Case 1 Results

[0064]

Case 2 : Cooling mode

[0065] In this test the fagade wall of the room was heated at 766W and about

1000W was used to heat the floor. Six 56W light sources were also included in the test room. [0066]

Case 2 Results

[0067]

[0068] The results obtained demonstrate that it is possible to achieve much better than the REHVA standard using less energy in heating mode using the system of the present invention. The results for cooling are comparable with the standard performance of the beam as the same element is used. Therefore these results demonstrate the feasibility of this novel approach.

Claims

1. A climate control system for an enclosed indoor space which has been divided into a plurality of zones in which the thermal characteristics are similar, comprising: means for heating and cooling water (106,112, 124), means for supplying ventilation air (128, 130), and a control system (120, 120A, 120B, 50); each zone being provided with a buffer vessel (122) for storing temperature controlled water; a plurality of air terminal devices (4), each having a pipe element (20) with an inlet (22) and an outlet (24) for carrying temperature controlled water from the buffer vessel through the device, and an inlet connection (10) for ventilation air, which flows over the pipe element and induces air flow into the device from an adjacent space; a flow and return pipe system (125, 126) for connecting the buffer vessel to the inlet and outlet of each air terminal device (4); and a pump (114) for pumping temperature controlled water through the pipe system.

2. A system as claimed in claim 1, wherein the temperature of the water in the buffer vessel is maintained within a range of 14 to 30° C.

3. A system as claimed in claim l or 2, wherein heating means (106,112) available to all zones are provided in a central plant room (100) and each zone also has a plant room (102,104) housing the buffer vessel for that zone.

4. A system as claimed in any one of the preceding claims, wherein the means for heating and cooling water comprises a heat pump (124) connected to the buffer vessel for each zone.

5. A system as claim in claim in any one of the preceding claims, wherein the means for cooling comprise a free cooling element and/or dry air cooler (123) connected to the buffer vessel for each zone.

6. A system as claimed in claim 4, wherein the heat pump is a reverse cycle refrigeration unit.

7. A system as claimed in any one of the preceding claims, wherein a bypass (127) is provided in the pipe system to allow water to return to the buffer vessel in a neutral condition when flow through the air terminal devices is not required.

8. A system as claimed in any one of the preceding claims, further comprising a pressure sensor in the pipe system for controlling operation of the pump.

9. A method of controlling the temperature of environmental air within a zone of an enclosed indoor space by circulating temperature controlled water from a single source (122) through a single heat exchange pipe element (20) with an inlet (22) and an outlet (24) in each chilled beam device within the zone, where the temperature differential between the target temperature within a zone and the water temperature is less than 15°C.

10. Use of an air terminal device (4) in a system as claimed in any one of claims 1 to 8, the device comprising a housing and a single pipe element (20) with an inlet and an outlet for carrying temperature controlled water from a buffer vessel through the device, and an inlet connection (10) for ventilation air, which flows over the pipe element and induces air flow into the device from an adjacent space.