Using measured equipment load profiles to 'right-size' HVACsystems and reduce energy use in laboratory buildings (Pt. 2) Page: 2 of 14
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Laboratory facilities present a significant opportunity and a unique challenge for energy efficient
and sustainable design, with their inherent complexity of systems, health and safety
requirements, long-term flexibility and adaptability needs, energy use intensity, and
environmental impacts. The CBECS database indicates that laboratories are among the three most
energy intensive building types [EIA 1999]. A single fume hood in a laboratory can consume as
much energy as three average U.S. homes. Laboratories often require a minimum of 6 to 12 air
changes per hour of outside air. In many areas of the U.S with evolving economies, the high tech
industry is an important area of economic growth, making it one of the fastest growing energy-
use sectors. However, laboratory facilities have historically been overlooked by the efficiency
community, which tended to focus on larger segments of the energy pie, such as offices and retail
facilities. Also, laboratories were seen as too specialized and complex to deal with. Energy
efficiency has typically been limited to lighting and minor HVAC measures, leaving out the more
energy intensive opportunities.
Recent experience has shown that there are significant energy efficiency opportunities in
laboratory buildings [Wirdzek et al. 2004]. Some of these measures are common to commercial
buildings in general, with no special considerations for laboratories (e.g. variable speed drives,
efficient lighting, etc.). Others opportunities require special considerations for laboratories (e.g.
energy recovery). Finally, some opportunities are very specific to laboratories (e.g. high-
performance fume hoods). The applicability and potential for each of these opportunities will
vary based on the type and location of the laboratory.
This paper focuses the use of measured equipment load data to "right-size" and minimize
simultaneous heating and cooling energy use in laboratory HVAC systems. "Equipment load" in
the context refers to the heat gain due to equipment such as autoclaves, glass washers,
refrigerators, computers, etc. There is a general paucity of measured equipment load data for
laboratories and other complex buildings and designers often use estimates based on
"nameplate" rated data or design assumptions from prior projects. Consequently, equipment
loads are frequently overestimated, and load variation across laboratory modules within a
building is typically underestimated. This results in two design flaws:
" Oversizing: Overestimation of equipment loads results in over-sized HVAC systems,
increasing initial construction costs as well as energy use due to inefficiencies at low part-
" Simultaneous heating and cooling: HVAC systems that are designed without accurately
accounting for equipment load variation across zones can significantly increase reheat
energy use, particularly for systems that use zone reheat for temperature control.
Thus, when designing a laboratory HVAC system, the use of measured equipment load data
from a comparable laboratory will support right-sizing HVAC systems and optimizing their
configuration to minimize simultaneous heating and cooling, saving initial construction costs as
well as life-cycle energy costs.
Section 2 addresses the right-sizing issue, by contrasting measured equipment load data with
design values that were used for sizing the HVAC systems in several laboratories. Section 3
addresses the second issue i.e. simultaneous heating and cooling, by examining the load variation
in time series measurements and analyzing its impact on energy use. This section also briefly
discusses HVAC design solutions that minimize simultaneous heating and cooling. Finally,
section 4 provides some conclusions.
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Mathew, Paul; Greenberg, Steve; Frenze, David; Morehead, Michael; Sartor, Dale & Starr, William. Using measured equipment load profiles to 'right-size' HVACsystems and reduce energy use in laboratory buildings (Pt. 2), article, June 29, 2005; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc901308/m1/2/: accessed April 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.