Using On-Site Meteorological Data to Minimize Fan
Energy Costs
Ronald L. Petersen, Ph.D., CPP,
Inc.
The purpose of a lab exhaust fan is to ensure that the toxic vapors
used inside a laboratory do not reenter the building or impact surrounding
building occupants or surrounding neighborhoods. To meet this goal,
building designers frequently use high flow and velocity fans, which
in turn may consume excess energy. Theoretically, it is know that
the concentration of any chemical in the exhaust stream at given
receptor locations (i.e., intakes and neighborhoods) is functionally
related to the ratio of exhaust velocity to wind speed. This ratio
is often defined as "R". If the relation between R and
concentration can be defined at all receptors of interest, then
the fan flow (and velocity) can be varied depending upon the local
wind conditions.
This paper will first describe how the relation between R and concentration
is defined using wind tunnel modeling at receptor locations of interest
for a research laboratory that has an on-site weather tower. Next,
the paper will show how the local weather data is used in conjunction
with the wind tunnel modeling results to set the fan volume flow
on a real-time basis. Finally, the paper will discuss the annual
energy savings that can be expecting using this approach.
Findings:
This paper shows that significant dollars can be saved in energy
costs by designing exhaust systems where the volume flow is controlled
using an on-site weather station.
Data that gathered as part of this study included hourly wind speed
and direction as well as predicted hourly concentrations at sensitive
receptor locations.
Labs21 Connection:
Reduced operating costs: By using the appropriate described,
exhaust systems can be designed that will lower energy costs.
Improved environmental quality: Again, using the described
approach will help ensure that concentration levels due to laboratory
pollutants will not exceed health and odor limits at intakes and
other sensitive locations (entrances, plazas, windows, etc.)
Increased health, safety, and productivity: An described
approach will help ensure toxic or odorous fumes do reenter the
building through air intakes, windows or doors.
Enhanced community relations: When neighbors see an exhaust
stack, they wonder what is coming out. Am I safe? A knowledge of
the air quality impacts can be used to educate the community and
tell them they are not at risk (if true).
Superior recruitment and retention of scientists: Buildings
that have health or odor problems due to fume reentry will not promote
recruitment and retention.
Biography:
Ron Petersen has a Ph.D. in Civil Engineering from Colorado
State University (Specialty in Wind Engineering), an M.S. in Atmospheric
Science from the South Dakota School of Mines and Technology and
a B.S. in Mathematics from the South Dakota School of Mines and
Technology. Dr. Petersen is a Vice President and Principal at CPP,
a firm that specializes in providing design information to account
for the effect of wind on man and his environment. One of the areas
that Dr. Petersen specializes in is providing design information
for new and existing laboratories or hospitals so that the air quality
impact of building exhausts can be minimized at nearby air intakes
and other sensitive locations (i.e., operable windows, entrances,
plazas, walkways, etc.). Some of the projects he has worked on include
NREL's new Science and Technology Facility, Lawrence Berkeley's
new Molecular Foundry, CDC Building 110, Cornell's Duffield Hall,
National Institutes of Health Clinical Research Center, the UCLA
Westwood Replacement Hospital, M.D. Anderson Cancer Research Center
in Houston and the Fred Hutchinson Cancer Research Center in Seattle.
He also was the principal investigator on two past ASHRAE research
projects and one ongoing project. The first project developed general
exhaust stack guidelines to account for the effect of architectural
screens. The second project looked at the benefit of hidden versus
visible air intakes. The ongoing project's goal is to provide information
regarding stack ganging.
Dr. Petersen is also actively involved in several professional
organizations to include AMS, ASHRAE, A&WMA, ISPE and AIHA.
In 1996, Dr. Petersen was the program chairman for the Ninth Joint
Conference on Air Pollution Meteorology and in 2000 helped coordinate
and provide comments on behalf of the Air & Waste Management
Association's meteorology committee for presentation at the 7th
EPA Modeling Conference regarding revisions to EPA's "Guideline
on Air Quality Modeling." He has also served or is serving
on committees related to pollutant dispersion and fume reentry for
ASHRAE, AMS and A&WMA. Dr. Petersen has also presented a short
course on fume reentry for the AIHA and has presented at several
past Labs21 Conferences. In January of 2004 he gave an ASHRAE short
course on exhaust and intake design. He has authored or coauthored
more than 300 papers and technical reports including technical papers
regarding minimizing pollutant reentry into buildings. Much of this
work was summarized in a 2002 ASHRAE Journal article.
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