In addition to using HPCDC waste
heat to temper outside ventilation
air, the high bay laboratories use
evaporative cooling and optimized
laboratory HVAC systems. The laboratory HVAC systems are variable air
volume (VAV), minimizing the amount
of exhaust and ventilation air required
to maintain environmental conditions.
as printers, copiers, fax machines,
microwaves, refrigerators, and coffee
pots) is not allowed in the building.
This eliminated unneeded equipment
and favored the use of shared multi-function printers and other “best in
The laboratory ventilation rate varies
depending on occupancy and use.
Wind tunnel testing was used to
optimize exhaust stack heights and
discharge velocities. These values
were then calibrated to a weather station on the building, allowing for a
reduction of exhaust stack discharge
velocity and exhaust fan energy based
on wind speed and direction.
Extensive daylighting combined
with sophisticated lighting monitoring and controls allows for additional
reductions in lighting energy.
The low wall height of workstations in the
ESIF office space helps facilitate daylighting.
Active chilled beams can be seen above the
windows to the right.
Heat Recovery. The HPCDC design intent
was for liquid cooling to remove 90% of
computer rack heat directly from chips
before it escaped into room air. Air coils
with fan walls would provide space cooling
for the remaining 10%. Recovered data
center heat is used to warm the building
supplemented by 160°F campus district
hot water in cold weather (if needed).
Careful attention must be paid to hydronic
piping. In the ESIF, the rack cooling coils
and air coils are currently piped in parallel,
providing both with the coldest water.
Once the system was operational it was
observed that cooler return water from
air coils was diluting warmer water from
racks. This was caused by more computer
rack heat being removed by air coils than
expected. Air coil temperatures needed to
be lower than intended to adequately cool
computer equipment. Also, return air temperatures are lower than expected.
The result is that while the computer
racks are adequately cooled, the combined
return water temperature is lower than
anticipated due to mixing of warm and
cool streams. The data center can heat
the rest of the building only when outside
air temperature is above 48°F. Much more
supplemental campus district heat has
been necessary than planned.
The remedy is to re-pipe the computer
cooling hydronic system so that air cooling
coils can be operated in series with rack
cooling. Air coil leaving water temperature
will be low enough to send to racks, where
it will be warmed to 105°F. This will be suf-
ficient to provide base-load heating for the
building much of the year with only minimal
supplemental hot water from the district
An additional 500 k W of new computer
racks is planned in the near term. The new
liquid cooled racks will be specified to emit
less heat to room air. More heat at higher
water temperature is expected to reduce
the need for supplemental campus hot
water to only the coldest times of the year.
It is important to plan for low-temp heat
recovery systems to need fine tuning and
ongoing commissioning. The waste heat
recovery system in the ESIF is innovative and
new, with performance risks. The potential
energy savings are significant so it was impor-
tant for a national lab to demonstrate leader-
ship in this first of its kind low-temp heat
recovery technology. The energy efficiency
strategies in the ESIF garnered utility rebates
that will be used to make sure that the neces-
sary commissioning, performance verification,
and system improvements happen.
Daylighting in Laboratories. Early in the project, the integrated design team worked together to ensure that ductwork was designed
around windows and skylights. In operation,
this has effectively reduced the lighting energy consumption in the laboratories.
RECOVERED AND DISTRICT
Actual District Heat Input
Actual Data Center to Building Heat
Model District Heating
Model Data Center to Building Heat