ASHRAE Journal - May 2014 - 83

2014 ASHRAE TEcHnology AwARd cASE STudiES
nology

Above Science lab with fume hood.
Left Student lounge.

This insulated thermal mass was leveraged in the
design of the HVAC system, enabling the interior to
absorb peak heating and cooling loads in a manner that
"time shifted" the peak loads by several hours.
This strategy also allowed a reduction in the peak load
seen by the central plant-the capacity of the central heat
pump is nominally 60 tons (211 kW) or equivalent to 700
ft2/ton (18.5 m2/kW)-again extremely low for this type of
building.
The design of the HVAC system commenced in parallel
to the architectural design process. A central geothermal heat pump system (a 60 ton [211 kW] magneticbearing chiller that can produce up to 90 tons [317 kW]
under certain conditions) providing chilled water and
hot water was selected as it allowed for an innovative
method of coupling sensible cooling devices directly to
the geothermal earth heat exchanger (GHX). This would
not have been possible with traditional distributed unitary water-to-air geothermal heat pumps. The central
geothermal energy plant simultaneously makes hot
(95°F [35°C]) and chilled (45°F [7°C]) water for heating
and cooling, feeding the outdoor air system as well as
the chilled beams, reheat coils and thermally massive
radiant heating/cooling system.
A hybrid wet/dry closed-circuit cooling tower (nominal
30 ton [105 kW] capacity) was selected to provide both
daily and seasonal preconditioning of the GHX. Three
hydraulically separated geothermal earth heat exchangers using vertical HDPE loops were sized, and are controlled, to provide different fluid temperatures and to
provide direct sensible cooling via radiant cooling and
active chilled beams. When the building cooling load
exceeds the heating load the control system determines
whether to direct the surplus thermal energy into the
GHX for later use/later rejection or to reject it to the
closed-circuit cooling tower if that process consumes

less energy or costs less. If the heating load exceeds the
cooling load, the heat deficit to the central heat pump is
taken from the GHX.
An 18,000 cfm (8495 L/s) variable volume dedicated
outdoor air system (DOAS) using dual energy recovery
wheel technology (one total energy wheel, one sensible
energy only wheel) supplies conditioned outside air to
the active chilled beams and hot water reheat coils for
each space. This system recovers energy and moisture,
heats, cools and dehumidifies the ventilation air as
required.
Thermally massive radiant heating and cooling using
embedded PEX tubing in the concrete floors and the
active chilled beams can use fluid directly from the
geothermal loops for sensible cooling without engaging chiller operation. A seven zone geothermal variable
refrigerant flow system was used for stairwell and vestibule conditioning.
An air quality monitoring system tracking VOCs,
CO2, particle counts and wet-bulb air temperature to
ensure that the air quality within the spaces is being
maintained. The air quality monitoring system takes air
samples from each space on a rotating basis and conveys
the samples to a central air quality testing station where
the air is analyzed for CO2, volatile organic compounds
(VOC), and wet-bulb temperature. Should one of the
monitored items exceed a setpoint, the ventilation rate
in the space is automatically increased. In the event of a
solvent spill in a lab area, the system automatically initiates a high air volume flush mode to rapidly remove the
contaminants.
The zone-level wet-bulb temperature sensing
allows monitoring and control of the dew-point
temperature to ensure that the radiant cooling
and active chilled beams do not enter into a mode
where unwanted condensation might occur as well
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