May 11, 2009

Project saving energy, money on lab fume hoods

Open fume hoods in labs across campus account for thousands of dollars in wasted energy each year.

Luci Keazer, senior lab engineer in Physical Facilities, is working to save those dollars, one fume hood at a time.

Fume hoods serve as safe places to perform chemical experiments by exhausting fumes out of the building. Room air is continuously pulled into the hood, the hood's fan uses energy to pull that air up and out of the unit, and more outside air must be conditioned for the lab space to replace the exhausted air.

Keazer was calculating the energy use by all 1,500 fume hoods on campus, when she decided to inform users of the potential energy savings they could attain by closing hoods.

Unlike constant air volume (CAV) fume hoods, which exhaust air at the same rate whether open or closed, variable air volume (VAV) hoods are designed to decrease the amount of exhaust, and therefore energy consumed, when they are closed. About half of the University's 1,500 fume hoods are VAV units.

During a recent visit to the labs in one building, Keazer found that about one-third of the facility's VAV fume hoods were left open to some extent while not in use.

"The problem is not confined to just one building," Keazer says. "I see similar ratios in many labs."

To combat this energy-wasting practice, Keazer and Physical Facilities intern Samantha King, a first-year engineering student, designed a campaign to ask faculty and students to be more conscious of closing sashes. They created a 4 x 6" sticker that is placed above each hood sash, and bears the reminder, "Close the sash when not in use."

To demonstrate the difference users can make by changing their habits, the sticker shows users the dollar value of the energy wasted by an open hood, how much money could be saved by keeping the hood closed when not in use, and the potential carbon footprint reduction in tons.

Each sticker's data is custom-calculated for that fume hood. King is working to complete a database of fume hood engineering data, which will help Physical Facilities to identify the largest energy users. 

"I want to go back in a few months and see if the stickers have had any impact on the amount of energy used," Keazer says.

The stickers eventually will be placed on all VAV fume hoods on the West Lafayette campus.

The sticker campaign is part of a larger initiative to look at energy use by all fume hoods and to find ways to reduce energy consumption. Other possibilities include converting some CAV hoods to VAV hoods, installing newer, more energy efficient fume hoods when departments replace older units, and automatic sash closers.

A ballpark estimate of the annual energy cost of the 1,500 campus fume hoods is $3 million to $4 million. Energy efficiency strategies could reduce this cost by 30 percent or more.