Chilled Beams For Cooling Buildings
I read a very interesting article in the November, 2008 issue of Architectural Record. In this entry, I will provide a summary from this article of many of the points that I feel offer a substantial energy savings, as well as occupant comfort level improvement advantage to any project. The full text may be found on pages 183-190.
In Europe and Australia, the use of chilled beams for cooling has seen successful use for over a decade. This can avoid the use of separate duct work and minimize mechanical system size, as well as produce increased levels of comfort and health for the building's occupants, while saving energy, and often, first-cost expense
These beams are not actual structural beams, but rather a part of a ceiling mounted structure that can provide cooling and sometimes even heating. They often resemble fluorescent light fixtures, and carry chilled water rather than chilled air. By carrying chilled water versus air, they are more energy efficient, due to the fact that less energy is needed to circulate water, than is needed to run an air handler in a conventional ducted air conditioning system. There are also fewer moving parts to wear out, thus reducing the need for regular servicing.
There are two types - Passive Chilled Beams and Active Chilled Beams. In the passive form, no fan is used to circulate surrounding air from the area of the beam, while the active form uses a fan to move air around the beam and out into the surrounding area. The passive type will work well in a building with lower cooling load requirements, while an active system will be better suited for a larger load requirement.
In the case of the passive beams, the cooling is provided by convection, as opposed to radiation, which have been used in walls and floors. The passive system is virtually silent as no fans are used, and are made up of coil to which aluminum fins are attached to copper tubing, in which chilled water is flowing. A decorative metal perforated casing covers the system, giving it that "fluorescent light fixture" look. This process then cools the surrounding air that then drops into the space below. it should be noted that while these fixtures can stand alone, or they can be incorporated into drop ceiling systems.
One trade-off here of the passive system, is that it does not provide for ventilation. Hence a separate system is needed, but the ducts will be able to much smaller in size. Thus, the savings on the total mechanical system alone can be substantial, let alone the operational costs. Ventilation, while brought in in smaller ducts, will contain a higher volume of fresh outside air, making for healthier indoor air quality.
Humidity and the attendant problem of condensation and mold formation are a critical issue here, but this can be dealt with very well. In general, the chilled water temperature is maintained at least two degrees above the dew point of the space to be conditioned. This will often be between 57 and 60 degrees Fahrenheit. In some cases, if an adequate supply of ground water (which can be recycled back to the ground) is available, often, no added water chilling is needed, thus saving even more energy. In very humid climates, it will be necessary to dehumidify the ventilation air, in order remove excess moisture from the space.
The passive chilled beams are often placed parallel and along the building perimeter walls for optimum occupant comfort. This is due to the fact that rising warm air will come into play with the beams. by doing this, the solar gain is counteracted. It is also important not place the beams directly over a heat generating source, as the the heat will prevent the cooled air from dropping to the area below.
As mentioned above the second type of chilled beam, the Active Chilled Beam is best used in spaces with higher cooling loads. This system does use a fan, but the air is delivered at high velocity through a diffuser nozzle, and is remarkably less noisy than conventional air conditioning systems that use large duct systems with heavy air handlers. This method functions by the warm air rising into the diffuser, where it is cooled by the coils. The ventilation air brought in by the small ducted nozzles then discharges this chilled air to the space below. A major benefit here, is that space heating can also be accomplished. Another advantage here, is that as that with the continuous air flow around the coils, condensation is reduced, allowing for chilled water to be even a degree and a half lower than the area's dew point.
In the case of the active system, the air flow volume is as much as 75 percent less than that of conventional air conditioning, meaning that occupants are less likely to feel drafts. Also,the active beam system can be placed in more locations, as they bring the warmer up to the coils and then disperse the cooled air across the top of the room. In the heating mode, the air is forced down into the room by the nozzle air flow, as convection would not function here.
One estimate of energy saving runs as high as 23 percent, based on the current ASHRAE 90.1 Standard, making this valuable in the area of LEED credits, namely Optimize Energy Performance.
There is another application here that is a multi-purpose system that combines the HVAC and other building management systems, such as lighting, sensors, fire sprinklers, cabling, etc. The advantage here is less visual clutter and a more compact installation. Thus while the initial cost may be higher for the complete package, it might be cost-effective when compared with advantages gained later on, such as installation scheduling, an a more compact system that saves on valuable space.
In Europe and Australia, the use of chilled beams for cooling has seen successful use for over a decade. This can avoid the use of separate duct work and minimize mechanical system size, as well as produce increased levels of comfort and health for the building's occupants, while saving energy, and often, first-cost expense
These beams are not actual structural beams, but rather a part of a ceiling mounted structure that can provide cooling and sometimes even heating. They often resemble fluorescent light fixtures, and carry chilled water rather than chilled air. By carrying chilled water versus air, they are more energy efficient, due to the fact that less energy is needed to circulate water, than is needed to run an air handler in a conventional ducted air conditioning system. There are also fewer moving parts to wear out, thus reducing the need for regular servicing.
There are two types - Passive Chilled Beams and Active Chilled Beams. In the passive form, no fan is used to circulate surrounding air from the area of the beam, while the active form uses a fan to move air around the beam and out into the surrounding area. The passive type will work well in a building with lower cooling load requirements, while an active system will be better suited for a larger load requirement.
In the case of the passive beams, the cooling is provided by convection, as opposed to radiation, which have been used in walls and floors. The passive system is virtually silent as no fans are used, and are made up of coil to which aluminum fins are attached to copper tubing, in which chilled water is flowing. A decorative metal perforated casing covers the system, giving it that "fluorescent light fixture" look. This process then cools the surrounding air that then drops into the space below. it should be noted that while these fixtures can stand alone, or they can be incorporated into drop ceiling systems.
One trade-off here of the passive system, is that it does not provide for ventilation. Hence a separate system is needed, but the ducts will be able to much smaller in size. Thus, the savings on the total mechanical system alone can be substantial, let alone the operational costs. Ventilation, while brought in in smaller ducts, will contain a higher volume of fresh outside air, making for healthier indoor air quality.
Humidity and the attendant problem of condensation and mold formation are a critical issue here, but this can be dealt with very well. In general, the chilled water temperature is maintained at least two degrees above the dew point of the space to be conditioned. This will often be between 57 and 60 degrees Fahrenheit. In some cases, if an adequate supply of ground water (which can be recycled back to the ground) is available, often, no added water chilling is needed, thus saving even more energy. In very humid climates, it will be necessary to dehumidify the ventilation air, in order remove excess moisture from the space.
The passive chilled beams are often placed parallel and along the building perimeter walls for optimum occupant comfort. This is due to the fact that rising warm air will come into play with the beams. by doing this, the solar gain is counteracted. It is also important not place the beams directly over a heat generating source, as the the heat will prevent the cooled air from dropping to the area below.
As mentioned above the second type of chilled beam, the Active Chilled Beam is best used in spaces with higher cooling loads. This system does use a fan, but the air is delivered at high velocity through a diffuser nozzle, and is remarkably less noisy than conventional air conditioning systems that use large duct systems with heavy air handlers. This method functions by the warm air rising into the diffuser, where it is cooled by the coils. The ventilation air brought in by the small ducted nozzles then discharges this chilled air to the space below. A major benefit here, is that space heating can also be accomplished. Another advantage here, is that as that with the continuous air flow around the coils, condensation is reduced, allowing for chilled water to be even a degree and a half lower than the area's dew point.
In the case of the active system, the air flow volume is as much as 75 percent less than that of conventional air conditioning, meaning that occupants are less likely to feel drafts. Also,the active beam system can be placed in more locations, as they bring the warmer up to the coils and then disperse the cooled air across the top of the room. In the heating mode, the air is forced down into the room by the nozzle air flow, as convection would not function here.
One estimate of energy saving runs as high as 23 percent, based on the current ASHRAE 90.1 Standard, making this valuable in the area of LEED credits, namely Optimize Energy Performance.
There is another application here that is a multi-purpose system that combines the HVAC and other building management systems, such as lighting, sensors, fire sprinklers, cabling, etc. The advantage here is less visual clutter and a more compact installation. Thus while the initial cost may be higher for the complete package, it might be cost-effective when compared with advantages gained later on, such as installation scheduling, an a more compact system that saves on valuable space.
Posted by Alan L. Englander at 12/30/2008 4:26 PM 
Categories: Optimizing Energy Use,Air Conditioning,Chilled Beams,HVAC,Interior Environmental Quality
Categories: Optimizing Energy Use,Air Conditioning,Chilled Beams,HVAC,Interior Environmental Quality
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