third as much outside air as when using an all-air system. So designing
chilled beams in labs not only reduces fan energy, but cooling energy as
CASE STUDY ANALYSIS
Now let’s look at a cost analysis completed for a lab project in which
chilled beams were compared to a conventional all-air VAV system. This
particular analysis was done for a pharmaceutical company lab in the
Midwest. The facility contained 54,000 sf of lab space which required
100% outside air (94DB/75WB) at all times. Its average sensible load
was roughly 72 Btu/hr/sf and had a minimum ventilation requirement
of 8 ACH. Table 1 illustrates what was required to condition this space
when using a conventional VAV system versus a chilled beam system.
The first thing to notice is that the chilled beam system required 60%
less air than the VAV system. This isn’t a surprise as the chilled beams
are handling 60% of the load. In this case they would have needed 20
air changes to satisfy the load using all air, but were able to get down
to their ventilation requirement of eight air changes by using chilled
beams. What stands out is that because this is 100% outside air and
using chilled beams enabled them to cool 60% less outside air, the
cooling load required to condition that air dropped by 60% as well. The
internal load doesn’t change; and they needed another 200 tons of cooling for the chilled beams. But at the end of the day, it was less than 800
tons of total cooling compared to nearly 1,500 tons of cooling.
It’s worth noting, as well, that the boiler capacity could also be
reduced by as much as 60% during winter because they were bringing
in 60% less outside air. It’s also worth noting that the number of control
points didn’t change between systems. The only difference is in a VAV
system the thermostat is tied to a VAV box that serves a zone, while in a
chilled beam system the thermostat is tied to a chilled-water valve that
serves a zone of beams. The number of zones and, therefore, the number
of control points should not change.
ENERGY AND COST SAVINGS
The analysis showed that in this type of application, the owner
could reduce the transport energy (fans and pumps) by 32%; cooling
energy by 46% and overall HVAC energy by 35%, all by using chilled
beams instead of an all-air VAV system. Generally speaking, a typical
heat-driven lab is able to achieve HVAC energy savings between 30%
and 50% when compared to VAVs, so even this case study is on the low
side of what’s attainable.
Now let’s take a look at the first costs. In Table 2, the cost of the air
handlers, chillers and boilers dedicated to conditioning all the outside
air—which was reduced by 60% by using chilled beams—was also
reduced by roughly 60%. Of course there are additional costs for the
chilled beam system—the chilled beams themselves plus inherent
piping and chiller—but when added to the reduced airside costs, they
found they were actually installing a more efficient system for less
Chilled beams are no longer just some new technology used sporadically in the U.S., but are quickly becoming the design method of choice
for many engineers who strive to give their customers a more energy-efficient (and almost maintenance-free) HVAC system, whether it’s office
buildings, patient rooms or labs. In some cases, energy-efficient chilled
beam systems can come at a slight premium, but due to their ability to
reduce load as well as energy, chilled beams will not only allow labs to
save operational dollars, but first-cost dollars as well.
Drew Elsberry, LEED AP, is Regional Sales Manager, TROX USA Inc.
LaboratoryDesign|NOV|DEC 2013 9
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