When considering new construction or renovation HVAC projects, chilled beam technology is a proven, although often overlooked, alternative to Variable-Air-Volume (VAV) systems. Used extensively in Europe, chilled beam technology employs a cooling coil using chilled water and convective air motion to provide radiant cooling.
An active chilled beam relies on a remote air handler to induce the room air to flow across the chilled water coil to cool the space. As a result, the beam can use higher supply water temperatures than a conventional VAV system, which significantly reduces chiller energy use. Chilled beam technology provides savings several ways:
1. Energy savings
- Eliminates the costs of traditional air handling unit fans that consume a lot of energy to circulate a large volume of air. With active chilled beams, fan motor horsepower is reduced by 50 to 70 percent because the volume of forced air volume is minimal. As a result, annual fan/pump energy savings range from 30 to 40 percent.
- Reduces the cost of reheat for dehumidification incurred with conventional HVAC technology, which overcools air to remove water vapor, then reheats it to the required temperature setpoint. An active chilled beam's minimal airflow facilitates latent cooling and ventilation without the need for overcooling. As a result, reheat energy costs are reduced by up to 88 percent.
- Cuts chiller operating costs, because a chilled beam can use a higher return water temperature, which increases chiller efficiency by 2 to 4 percent per degree. Moreover, dedicated chillers can be used to create opportunities for using waterside economizers, depending on the region. A dedicated chiller can be 40 percent more efficient when supplying 55 to 60°F water. As a result, the operational cost of a dedicated chiller for a chilled beam application is typically 15 percent less than a central chiller for a conventional system.
2. Maintenance savings
- Eliminates filters, because air is moving at low velocity over a dry coil surface, which dramatically reduces the amount of dust and contaminants in the supplied air. Active chilled beam technology is specifically exempted from requiring filtration by the International Mechanical Code (IMC) for commercial buildings.
- Eliminates terminal blower motors within active chilled beam terminal units, which receive primary ventilation from the central air handling system fan motor. As a result, AHU fan motor life expectancy is 10 to 15 years, and there are fewer fan motors to replace, saving the replacement cost of $450 to $500 each.
- Uses fewer components to reduce maintenance and repair costs, lowering the 20-year life cycle cost by 20 to 25 percent versus more complex VAV technology.
3. Structural savings
- Reduces slab-to-slab spacing, because the low profile of chilled beams allows height reductions of up to 12 inches per floor, yielding average structural savings of $3.75 per square foot.
- Reduces the size of components and shrinks duct cross-sectional areas by 50 percent or more along with the elimination of fan-powered terminal units.
- Shrinks air handling unit size with an AHU footprint that is 30 to 40 percent smaller, increasing usable floor space.
Chilled beams bring new benefits to today's buildings
At a time when building owners and managers are facing complex building performance and budgetary challenges, chilled beams offer an attractive alternative to costlier VAV solutions. Chilled beams offer significant energy savings, reduced maintenance requirements and ease operation, which should please facility managers. Just as importantly, they contribute to tenant satisfaction thanks to quiet operation, good indoor air quality and consistent cooling. Click here to visit our website.
Jeff Scanes, director, Air Distribution Product Sales, Johnson Controls, holds a Bachelor of Science degree in electronic engineering and has over 25 years of HVAC sales engineering experience. Scanes is also a member of ASHRAE and ASHE.