40 LaboratoryDesign|NOV|DEC 2014
grid, plus low airflow (such as 130 ACH), 10,000
cfm/k W can be achieved.
MAKE-UP AIR CHANGE RATE (ACH)
MAHUs are often designed for 20 to 45
ACH, whereas actual operation tends to fall in
the 15 to 25 ACH range. In the case of Harvard
LISE, the facility managers turned down the
exhaust airflow and added pressure-differ-
ential sensors to the cleanroom envelope to
allow the make-up airflow to turn down,
while maintaining a positively pressurized
environment. The latest trend in cleanroom
energy efficiency is true variable-air-volume
operation, relying on specialty-coated venturi
air valves for corrosive exhaust air streams.
Most cleanroom specialists would agree the
Case studies in selecting a differentiated ultra-low
standard cleanroom target dewpoint is 46 to 48 F
(particularly for programs such as photolithog-
raphy). But, based on our survey, designs range
from 40 to 51 F, and actual operation is even
broader. One cleanroom has essentially no oper-
ating dewpoint control. Given the high energy
consumption associated with strict dewpoint
control, further investigation is warranted.
This research bears-out the theory that
cleanrooms vary significantly. But it also
illustrates some key parameters for designing
an energy-efficient cleanroom. A philosophy
of “right-sizing + scalability” is informing the
next generation of efficient cleanroom designs.
Jacob Werner specializes in the planning, design
and construction of lab buildings. He’s the leader of
Wilson Architects’ sustainability initiative, for which
he conducts research on energy-efficiency strate-
gies for labs. As Director of Sustainable Design at
BR+A Consulting Engineers, Jacob Knowles heads
the NET+ sustainability consulting team. Over the
past decade, he has championed the sustainability
agenda for over 20 million sf of healthcare, research,
commercial and institutional projects.
cleanrooms: Lessons learned
from Harvard LISE and other
continued from page 39
By: Neil Lane, CEO, Stirling Ultracold, Global
All mechanically refrigerated ultra-low temperature (ULT) freezers using cascade refrigeration systems are commoditized
and rely upon the same cooling technology
with little difference in performance from one
brand to another. Freezers of this type are typically sold through multiple competing channels
either singly or in volume on a relationship
basis with significant discounts offered.
In 2013, a full-size, 27-cu-ft ULT freezer
cooled by a Stirling engine was introduced to
the market. Based on independent studies by
the U.S. Dept. of Energy, the Stirling engine
freezer is the most energy-efficient ULT
freezer of those tested among market leaders.
It uses a 100% natural refrigerant cooling
system. As a result, large facility managers
are now evaluating ULT freezers not on initial purchase price, but benefits that extend
throughout the organization, such as total
cost savings, environmental sustainability and
quality of cold.
Historically, purchasing decisions have been
made by a combination of end users and procurement. The criteria for purchase have been
the users’ comfort with the brand, freezer features and procurements’ ability to extract the
largest possible discount.
This presentation illustrates new purchasing approaches based on case studies where
Stirling Ultracold Model SU780UE, shown with optional inventory racks and additional shelves.
organizations are adopting the Stirling engine
freezers. Cases include a large biotech com-
pany, an internationally recognized cancer
research center and a top U.S. research univer-
sity. Each case offers a unique combination of
factors that justify the adoption of the Stirling
engine freezers, including total cost of own-
ership, utility rebates, internal rebates, insti-
tutional environmental compliance require-
ments, institutional sustainability goals and
freezer performance requirements.
For each case study, the combination of
factors and engagement points within each
institution are illustrated.
Neil Lane is president and CEO of Stirling
Ultracold, a division of Global Cooling Inc.,