News From the Hood, Volume 1, March 2002
S E P T E M B E R Issue No.2 2 0 0 2

Brought to you by The Applications Team at Lawrence Berkeley National Laboratory.

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Newsletter Feedback:

Evan Mills

Technical Questions:

Geoffrey Bell


The Berkeley Hood
Applications Team

Fumehood PictureLaboratory fume hoods are highly energy-intensive pieces of equipment found across a spectrum of industries and in educational labs. Each hood uses as much energy as a home, and we estimate that existing fume hoods use up to half a billion dollars of energy each year. The Berkeley Hood project is working towards the commercialization of an alternative that will cut energy use by 50% or more, while improving Fumehood Picture safety through improved containment of dangerous materials in the hood and reducing the size and first costs of facility HVAC systems thanks to lower overall airflow. This newsletter keeps readers abreast of new developments in research being conducted in this exciting area by the Lawrence Berkeley National Laboratory (LBNL) Applications Team.

New Patent

A second, new patent (#6,428,408) was issued for the Berkeley Hood on 6 August 2002 under the title "Low Flow Fume Hood." The new patent further defines the principal of displacement flow ventilation in a general push-pull configuration. The new hood's arrangement of supply plenums and interior modifications is called an "air divider." The first Berkeley hood patent (#6,089,970) demonstrated containment of contaminants could be achieved at exhaust airflow rates substantially lower than a conventional hood. This latest patent confirms that containment can be achieved at 70 percent less airflow.

Demonstrated Performance

We have had several opportunities to field test Berkeley Hoods:

  • one at the University of California, San Francisco, Department of pathology, Medical Radiology Center (sponsored by Pacific Gas and Electric Co., PG&E)
  • one at Montana State University's environmental health and safety laboratory facility (sponsored by the National Institute for Standards and Technology, NIST)
  • one currently underway in a biology lab at San Diego State University, (sponsored by San Diego Gas and Electric Co., SDG&E)

  • Additional demos are in the planning stage that will assess wider (six-foot) hoods (sponsored by the California Energy Commission, CEC).

A recent feature article in Engineered Systems magazine presents our test results to-date. Tests conducted according to the ASHRAE Standard 110-1995 protocol found that the prototype hood contained smoke and operated at less than 0.10 ppm tracer gas leakage, the maximum level recommended by the American National Standards Institute ANSI/AIHA Z9.5-1992 (4.0 AI 0.1). The Berkeley Hood was shown to contain test smoke and tracer gas under all conditions down to 33% of full flow. The hood is being operated at 50% of normal flow to provide the operators with an added margin of safety.

Energy Use and Savings Update

The Berkeley Hood team has developed an improved method for calculating fume hood energy use. The resulting estimates of energy use and savings are higher than previously estimated thanks to the inclusion of terminal reheat, and better modeling of system-level pressure drops. Hoods in an average U.S. climate, require over $4,300/year of energy (over three-times as much energy as an average home). Looked at on a national scale (assuming 750,000 hoods nationally), fume hoods cost $3.2 billion each year to operate (included associated cooling energy), and require the electrical output of about 20 electric power plants (at 250 megawatts each), plus nearly 200 trillion cubic feet of natural gas each year for the associated heating of outside make-up air. We have also assessed fume hood performance in hot Asian climates, where cooling loads are more significant than in the U.S.. For example, the typical hood would use $7,200/year in Taiwan and $9,500/year in Singapore. Since they run 24x7, efficient fume hoods have an extra value in today's climate of concern about electricity peak power demands. Our current national savings estimates are $2,100/hood, or $1.2 billion annually (assuming 75% ultimate market penetration of high-performance hoods).

Regulatory Update

While the Berkeley Hood performs very well in tracer-gas testing of containment, special barriers are presented by certain codes and most standards when they require 100 feet per minute average face velocity (e.g. from the California Occupational Safety and Health Administration (CAL/OSHA)). The problem is created when the focus is on maintaining absolute airflow rates, rather than on pollutant containment itself. The Berkeley Hood achieves containment at far lower airflow rates than conventional hoods that only use the face-velocity standard to determine the hood's ability to contain. Furthermore, with supply air introduced at or inside the Berkeley Hood's face, face velocities are well below 100 feet per minute (the providing technical advise within, various standards-related activities that validate the Berkeley hood push-pull configuration.