Efficacy of Utilizing Wind-Sensitive Exhaust System Controls to Save Energy

Chet Wisner, Ambient Air Technologies, LLC

Although laboratory exhaust systems have traditionally been designed to use constant-velocity fans to accommodate a worst-case wind condition for the site, there is increasing interest in the energy savings that may be achieved by automatically adjusting the exhaust stack flow in response to local wind conditions. Considering that some design teams are projecting an annual cost of electric power for a single 40 horse power motor to be about $40,000, there may also be significant economic incentive in regulating the exhaust stack flow to more closely reflect that actually needed by the current local wind conditions to ensure safe plume dispersion. Designing an exhaust system which adjusts to reflect the current local winds requires additional effort for the mechanical engineer and more extensive wind tunnel studies than required for a traditional constant-velocity exhaust system. Whether this additional effort and expense are warranted depends on the potential energy savings which, in turn, depends on the wind climatology and anticipated dispersion characteristics of the site and of certain limiting parameters of mechanical design. This presentation will describe an effective method for estimating the potential annual energy saving prior to initiating extensive wind tunnel and mechanical design efforts. Examples of implementing the system will be presented for the mechanical renovation of a laboratory and for the exhaust system design of a new laboratory facility.

Biography:

Chet Wisner is the President of Ambient Air Technologies, LLC, a Colorado based firm specializing in wind-tunnel modeling of laboratory and healthcare facilities. He has played an active role in the air quality portion of the environmental industry for over 35 years. Applying his experience and expertise in meteorology, engineering, and physics to physical modeling using scale models in a boundary-layer wind tunnel, he has personally managed or directed many wind tunnel studies. Chet coauthored an EPA-recommended protocol for the use of environmental wind tunnel studies to determine plume downwash characteristics for input to EPA's own regulatory dispersion models. He was responsible for some of the largest air quality monitoring networks in the U.S., and has conducted numerous field studies of atmospheric dispersion. His educational background includes a Bachelor of Science in Engineering Physics from UC Berkeley, a Master of Science in Meteorology from the South Dakota School of Mines and Technology, and a Master of Business Administration from UCLA. He is an active member of several professional organizations including ASHRAE, the Air & Waste Management Association, and the American Meteorological Society and has been a speaker at Labs21 for the past several years.

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