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Cool Controls for the Energy Efficient Lab

Thu, 06/09/2011 - 6:31am
Lindsay Hock

The high energy demands of laboratories can be tamed with control systems for airflow and lighting, as well as a cool answer from above.

Lab Energy Efficiency 1

TROX chilled beams installed at Tahoe Center for Environmental Sciences (TCES), Lake Tahoe, Nev. Photo: TROX USA, Inc.

In the search for energy and financial savings, consumers have adjusted the thermostat, sealed cracks around doors and windows, and installed compact fluorescent light bulbs. Laboratory owners also can take advantage of technology options to reduce energy use and operating costs through renovations or retrofits to existing systems.

According to Laboratories for the 21st Century (Labs21), a joint effort of the U.S. Environmental Protection Agency (EPA) and U.S. Department of Energy (DOE), a typical laboratory building consumes five to ten times more energy per square foot than a typical office building. HVAC systems consume about 70% of the energy; electrical and lighting make up the rest of the load.

Ventilation control
About 44% of the energy consumed by HVAC equipment is for ventilation loads that help a laboratory function safely; fume hoods are the largest driver of laboratory exhaust. To protect laboratory technicians from exposure to hazardous chemicals, many areas in a laboratory require fresh air that is conditioned, used once, and exhausted. Described in dollars per unit of exhausted air per year, "U.S. laboratory energy usage is seeing costs range from $3 to $7 per cfm per year," says Paul Fuson, business development manager, life science, Siemens Industry Inc., Buffalo Grove, Ill. Fume hood controls offer one solution to reduce energy use and costs.

"Laboratories are often able to finance new fume hood controls with payback periods less than three years," states Fuson.

Often integrated into a facility’s building automation system (BAS), the fume hood control regulates the face velocity at the fume hood’s sash opening. When air leaves the hood, it is exhausted through the laboratory ductwork, where air movement is regulated by a damper or venturi valve. The fume hood controller instructs the valve to open or close to maintain proper air flow within the hood based on input from a velocity sensor located on the inside wall of the fume hood, from a sash position sensor, or both.

However, a sash position sensor cannot account for an operator standing in front of the fume hood or other factors that affect the actual face velocity at the sash opening. An incorrect calculation can restrict the air movement into the fume hood, potentially exposing workers to fumes emanating from the sash opening.

"Whereas most other vendors only rely on sash height to control the face velocity of a hood, we have elected to use a second sensor, located on the side wall of the fume hood to measure the actual face velocity at the sash opening in real time," says John Taylor, principal engineering at Triatek, Norcross, Ga. The second sensor fine-tunes the exhaust valve position derived from the controller monitoring of the sash height.

Lab Energy Efficiency 2

The Radio Powr Savr Daylight Sensor. Photo: Lutron Electronics

Water-driven comfort
Used in Europe for many years, active chilled beams gained traction in the United States starting in 2005. The market for the technology in laboratories has grown and “promises to continue to grow due to their significant energy reduction potential,” says Ken Loudermilk, vice president, technology and development, TROX USA, Inc., Cumming, Ga., a manufacturer of active and passive chilled beam solutions.

Active chilled beams are ceiling-mounted diffusers—typically implemented above benches—that incorporate cooling coils, which use tempered (56 to 60 F) chilled water to remove the space sensible heat gains in the laboratory without causing condensation on the lab’s surfaces. The induced room air is cooled by the coil above the ceiling tile to provide local cooling in the laboratory.

Instruments and equipment create high heat gains. Laboratories having a moderate ventilation air requirement (less than 10 air changes per hour) "may require as much as three times this ventilation air volume to satisfy its cooling requirement when conditioned by an all-air HVAC system," says Loudermilk.

All-air HVAC systems rely on 100% outside air, which must be cooled and dehumidified, delivered to the space, and then directed into the lab. Water has a heat capacity about four times that of air and nearly a 900 times greater density, making it a more efficient heat transfer medium than air. Active chilled beams remove about two-thirds of the space sensible heat, reducing the space airflow delivery to its minimum ventilation rate. "This results in laboratory heating and cooling energy reductions of 25% to 40% versus conventional all-air systems," says Loudermilk.

With chilled beams, cooling energy is transported in smaller pipes compared to conventional systems, reducing air handling unit and ductwork capacities. "The installation costs for chilled beam systems in laboratories have proven to be less than that of installing conventional all-air systems," says Loudermilk.

Illuminating energy savings
To illuminate the large space of a laboratory, lighting designers and electrical engineers specify between 70 to 80 footcandles of light, about twice the specified amount for an office building. Designers use a three-phase approach to provide the necessary light and energy efficiency.

Lab Energy Efficiency 3

Active chilled beams are installed directly over the lab benches at the Unviersity of Washington to capture the heat plume from the bench-mounted equipment. Photo: TROX USA, Inc.

First, daylight sensor technology at the building perimeter reads the ambient light contributions from windows and dims the lights in response to the natural sunlight entering the building. This can result in a one to one ratio on energy savings. "So if you dim the lights 50%, you save 50% energy," says Joe Parks, senior sales supervisor at Lutron Electronics, Coopersburg, Pa., a manufacturer of light control systems for laboratories and commercial buildings.

Ceiling-mounted occupancy sensors use both passive infrared and ultrasonic sensors to turn off the lights when the laboratory is unoccupied. The infrared sensor component of the technology is highly sensitive, "so it senses body heat and when a technician moves," says Parks. The ultrasonic sensor works more like sonar; "it will sense minor motion. So if a lab technician is looking through a microscope and they are moving their fingers to adjust the scope, the ultrasonic portion will pick up that subtle movement," Parks continues. These sensors provide an overall energy savings of 10 to 20%.

When zoned in open laboratory spaces to control multiple 2,500 to 10,000 square foot spaces, these sensors must be coordinated with laboratory casework and supply air diffusers in order operate properly.

The third element is a digitally addressable ballast implemented in each ceiling fixture—commonly a T8/T5 linear fluorescent system. Using information relayed by the daylight and occupancy sensors, the ballast controls the lights for overall energy efficiency.

Due to the energy savings offered, occupancy and daylight sensors, along with digitally addressable ballast, provide a relatively quick ROI and hold much promise for lighting and electrical energy savings.

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