Page 28 - Occupational Health & Safety, February 2018

INDUSTRIAL HYGIENE
Controlling Ventilation Rates at University Research Laboratories
Laboratories’ ventilation systems make up the majority of Northwestern University’s electricity demand.
BY MARKUS SCHAUFELE
aboratory buildings consume more than half of the total Northwestern University (NU) electricity demand, and a large part of this is for laboratory building ventilation systems.
exchange rate for laboratories is 6.2 per hour. The cur- rently designed air exchange rate for a vivarium is 15 per hour. Since spill incidents and unsafe releases oc- cur only rarely, laboratories are over-ventilated about 99 percent of the time. In the rare case of a spill or release, no extra clearance ventilation is provided.
New Technologies Implemented
In 2010, NU installed its first ventilation optimiza- tion system supplied by Massachusetts-based Air- cuity Inc. to monitor air quality related to use of a heat wheel—an energy recovery heat exchanger po- sitioned within the supply and exhaust air streams of the air-handling system.
In 2011, NU committed more than $40 million as a part of the Northwestern Energy Retrofit Fund (NERF) to pay for gas and energy conservation proj- ects across its two campuses. This commitment to en- ergy efficiency has decreased the amount of electricity purchased from the grid by almost 5 percent, even as the square footage of occupied space has increased.
Then in 2012, a large national energy services company implemented an energy conservation proj- ect for the Chicago campus research buildings, and a demand control optimization system was imple- mented on various lab floor remodels. In 2013, the NU Facilities Department began coordinating instal- lations of the system at several Evanston campus sci- ence buildings, completing the installations in 2015 and 2016.
The ventilation optimization system monitors lab- oratory air quality parameters of total volatile organic compounds (TVOC) and particulates. Other labora- tory and building control systems monitor occupancy via ceiling-mounted occupancy sensors. The informa- tion collected dynamically controls ventilation rates. The intelligent system adjusts the volume of labora- tory air exhausted and respectively supplied within a specified range, usually between 2-12 air changes per hour. This dynamically controlled system provides the least amount of ventilation in an unoccupied lab (2 air changes). It can provide about twice the tradi- tional ventilation rate in a detected release event (12 air changes).
As of spring 2017, the Aircuity system had been in- stalled in 130 laboratory rooms on the Evanston cam- pus and 370 laboratory rooms on the Chicago campus.
Over the past decade, NU has been installing a ven- tilation optimization system in laboratory rooms that dynamically controls ventilation rates to reduce energy use, provide a better indoor environment for occupants, and monitor space conditions along with occupant behavior.
The university has 15 science research build- ings on two campuses. This space allows about $650 million in sponsored research activities. Approxi- mately 5,000 NU researchers were registered to do wet bench research in NU laboratories in 2017, and a large number of undergraduate students rotated through the undergraduate teaching labs on the Evanston, Ill., campus.
In 2016, the laboratory spaces consumed almost 118 million kilowatt-hours (kWh) of electricity, which, at a cost of $0.08/kWh, amounts to close to $10 million. This is about half of the total Northwest- ern University electricity demand. A large part of this electricity demand is made up of the laboratory build- ing ventilation systems’ electrical power needs.
Ventilation in the science laboratories and vivaria serves four main objectives: safe breathing air for oc- cupants; suitable temperature and humidity for re- search activities; dilution and transport of equipment heat loads; and spot exhaust for vented enclosures, including cage racks for animals and fume hoods or snorkels for chemistry.
Whereas a ventilation system designed for an of- fice building may recirculate most of its air and only supply a small percentage of fresh air, architectural and building codes require that laboratory rooms and vivaria use only fresh outside air for ventilation. This design difference explains why laboratories require so much more energy to operate. A large amount of en- ergy is required to supply, heat, cool, condition, filter, distribute, and exhaust this air in laboratory buildings.
The traditional laboratory design approach is to proactively ventilate all the time in anticipation of a chemical spill or release. This approach means ex- hausting the entire internal air volume of a typical laboratory into the atmosphere every 10 minutes. The Northwestern University traditionally prescribed air
22 Occupational Health & Safety | FEBRUARY 2018
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