Why are active chilled beams "Green"?
Fan Energy Savings
In general the design intent is for the central system to circulate only the amount of air
needed for ventilation and latent load purposes, with the active chilled beams providing the
additional air movement and sensible cooling and/or heating required through the induced room air and
secondary water coil. In this manner the amount of primary air circulated by the
central system is dramatically reduced (often 75-85% less than conventional
"all air" systems).
Essentially active chilled beams transfer a large portion of the cooling and heating loads from
the less efficient air distribution system (fans and ductwork) to the more efficient water
distribution system (pumps and piping).
The net result of this shift in loads with active chilled beam systems is lower energy
consumption and operating costs. Studies have shown that fans are the largest consumer
of energy in most commercail buildings in North America.
With active chilled beam systems the fan energy is dramatically reduced due to the relatively small
amount and low pressure of the primary air being circulated by the central system.
Chiller Energy Savings
While the size of the chiller in an active chilled beam system would normally
be the same as that needed in a conventional "all air" system, its
effective hours of operation (or loading) could be significantly less if the
system employs a water-side economizer to serve the Active Chilled Beams.
This is due to the relatively warmer secondary water temperatures (typically
56 — 58 °F) used by the Active Chilled Beams which allows the cooling load
to be satisfied for more hours using the water-side economizer.
Also, if separate chillers are serving the central air handlers and the active
chilled beams, the COP of the chiller serving the Active Chilled Beams would
also be much higher due to the relatively warmer water temperatures used by
the Active Chilled Beams.
Heating Energy Savings
As the Active Chilled Beams normally provide sufficient heating capacities at
relatively moderate hot water temperatures (110 – 130 °F) there is also an
opportunity to maximize the efficiency of condensing boilers through the relatively
low water temperatures being returned to the boilers. With the relatively low water
temperatures required, using geothermal heat pumps to satisfy the heating loads is