Neurogen is involved in research and early stage development of drugs, and the Phase IV building houses 18 laboratory workstations (each with 10' exhaust fume hoods) used for basic research. While the company is independent, it occasionally forms collaborations with pharmaceutical manufacturers, setting up joint ventures for both production and marketing of the drugs it helps to develop.

Conditioned Makeup Air Increases Energy Costs

Although many of its capabilities are unique, the company shares a characteristic common to many pharmaceutical firms and research laboratories: spending a substantial portion of its budget on energy costs for heating and cooling. In fact, many laboratory facilities are burdened with perhaps the most expensive energy costs in the country, mainly because they require conditioned 100 percent makeup air for workstation environments. This makeup air must be filtered, heated, cooled, humidified, or dehumidified (or some combination) depending upon circumstances.

Providing comfortable and safe work places for scientists and technicians requires efficient--and expensive--heating and cooling of makeup air; workstation fume hoods require sophisticated controls and management; and other equipment and systems in the research environment also consume energy. These are some of the factors that contribute to extremely high energy costs in these industries. When you add fume hood exhaust systems on the roof--which must operate whenever a workstation is being used--it's obvious that energy costs can mount up quickly. At Neurogen, for example, about 30,000 cf of makeup air per minute has to be moved in and out of the new 20,000-sf Phase IV research building.

High Energy Costs Impact Campus Facilities

The laboratories at Dartmouth College, in Hanover, N.H., are similar to Neurogen's. Dartmouth operates the 44,000-sf Steele Building for its chemistry students, containing 85 laboratory workstations and associated fume hoods. The facility--one of two chemistry buildings on campus--was recently renovated, with only the original exterior walls remaining.

Bo Petersson, P.E., is a mechanical engineer who works in Dartmouth's facilities operations and management section in the engineering office, with Bruce Dunn assisting him. In designing its new laboratory building, Dartmouth was concerned with issues of fume hood exhaust re-entrainment, pollution abatement, odor control, and energy costs. Dartmouth's laboratories also require 100 percent conditioned makeup air, thus high energy costs for heating and cooling were also key considerations.

At Neurogen, however, Waldron's laboratory workstation fume hood exhaust is being handled by a mixed flow impeller roof exhaust system. These fans operate on a unique principle of diluting exhaust air with outside air above the roof (by as much as 170 percent), sending a vertical jet plume of exhaust up to 350' high to eliminate re-entrainment possibilities and pollution problems, while also preventing odors from entering the building or neighboring facilities. These types of mixed flow impeller fans are designed to replace centrifugal belt driven fans which generally are required for each fume hood and are connected to dedicated, tall exhaust stacks on the roof. They use direct drive maintenance-free motors and provide substantially lower profiles on the roof for aesthetic considerations.

Heat Exchanger Coils Recover Exhaust Heat

The mixed flow impeller system at Neurogen was designed to accommodate accessory heat recovery modules consisting of glycol/water filled coils that extract heat from the workstation fume hood exhaust before it is discharged above the roofline. The warm air from the heat exchanger is transferred to the supply side air handler to preheat the conditioned air entering the building. This technique reduces the amount of natural gas needed to preheat makeup substantially.

Neurogen Cuts Energy Costs

As a typical example, Waldron said that in winter "there were days when we were putting about 10° F into the makeup air simply by capturing heat from the exhaust stream." He added that 10° F was the temperature difference between the incoming air (at the outside air temperature) and the air entering the intake system after it was passed through the glycol loop coils. "For every degree you add, you reduce your energy costs about three percent," Waldron said, "so that a 10° F rise in intake air means that about 30 percent of energy savings can be realized."

At Dartmouth, Petersson and Dunn have seen similar results with their fans. Since both facilities are located in the Northeast, they experience varying temperatures during the year, and conditioned makeup air must either be cooled with workstation fume hood exhaust during the cooling season or warmed during the heating season. Systems like these are only usable when the outside air temperatures are below 40° F or above 80° F typically. "You need a big enough difference between outside and inside air to make it practical," Petersson said. For example, with regard to cooling the building in warmer temperatures, if the outside air temperature is 90° F and this air is sent through the heat recovery system, the air temperature drop is typically 4° to 5° F. These figures also equate to an approximate three percent drop in energy consumption for each 1° F drop in air temperature.

De-Regulation Hasn't Reduced Energy Costs

After salaries, energy is the second largest expense at most pharmaceutical research organizations. It is not unusual in a facility such as Neurogen's to use 15 percent or more of an entire operating budget for energy, which is not out of line for the entire industry. While Dartmouth's energy costs are not quite as high, its energy savings are proportional. Both Petersson and Dunn also feel strongly about energy costs, consumption, and savings, pointing out that recent energy de-regulation policies in California have not resulted in reducing costs as anticipated.

As Waldron points out, "You can tell where the rest of the county is going to be in a year or two by looking at California. The early results of de-regulation there have not been good--in terms of costs and also in the reliability of service." He suggests that organizations that are sensitive to energy costs not "depend on de-regulation to cut energy bills; you have to work on the demand side."

With regard to overall costs--for system hardware as well as energy charges--Waldron believes that a payback cycle of three years or less has made this solution economically sound for Neurogen. (Some users have experienced actual payback in two years or less depending upon system configuration, climate, and other variables.) With energy costs rising dramatically (and no relief in sight) Waldron believes that Neurogen has gone in the right direction with its heat recovery systems on its laboratory fume hood exhaust fans.

The Benefits of Technology and Heat Recovery

Both Neurogen's and Dartmouth's workstation fume hood exhaust fans--in combination with heat recovery coils--provide substantial advantages that include inherently lower energy consumption over comparable centrifugal-type exhaust systems, reduced maintenance, elimination of re-entrainment possibilities, odor control, and elimination of tall exhaust stacks with their associated negative implications in the neighborhood. With the ability to pre-heat and pre-cool makeup air prior to its introduction into the laboratory workstation areas, the systems also provide unprecedented efficiency and energy savings.

By Paul A. Tetley

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