Sensing energy conservation

Dec 11th, 2008 | By | Category: Campus News, December 11, 2008

Hardin Hall opts for sensor control of lights, HVAC systems

The School of Natural Resources is practicing what it teaches.

With a focus on environmental sustainability, Natural Resources has volunteered to become UNL’s first building with individual occupancy sensors controlling lights and HVAC systems. The sensors – which are being installed in individual offices, meeting rooms, restrooms and vending areas – use infrared technology to detect heat, turning lights off and placing thermostats in standby when rooms are empty.

The choice to install the sensors comes as UNL administrators are crafting a plan for utility savings across the university.

“We are trying to position Natural Resources as the campus leader in environmental sustainability,” said Don Wilhite, director of Natural Resources. “We are looking for as many opportunities as possible to save energy in this building. And, when we learned about these sensors, we saw it as an opportunity to save resources and reinforce what we teach in the classroom.”

sensor installation
SENSOR INSTALL – Ed Banks, a control systems technician with Facilities Management and Planning, hooks an occupancy sensor (top, center) to a thermostat in a third floor office of Hardin Hall. The sensors are being installed to trim energy consumption by turning off lights and HVAC systems when rooms are not occupied.

The sensor technology has been used for 10 to 15 years, primarily by the private sector for controlling lights. While they do curtail energy bills when linked to light systems, the sensors become economical when HVAC systems are involved said Kirk Conger, energy projects manager for Building Systems Maintenance.

“We started analyzing possible savings and it really wasn’t enough with lights alone,” said Conger. “When we applied them to ventilation systems, the energy savings was a happy discovery.”

The cost to purchase and install an individual sensor is about $250. In an academic building like Hardin Hall, each sensor will save about $80 per year in utility costs.

“We expect the sensors will pay for themselves within three years,” said Conger.

Building Systems Maintenance uses the sensors in a limited capacity in Avery and Oldfather halls. The only other University of Nebraska building to be entirely wired with sensors is Varner Hall – which has measured a vast improvement in energy savings.

“This is one of those times you can give a lot of credit to Central Administration,” said Ted Weidner, assistant vice chancellor of Facilities Management and Planning. “We told them about the occupancy sensors and the potential savings. They thought the project looked good and the payback would be worth it.

“Boy oh boy, was it ever.”

Instead of a three-year return on the investment, the Varner Hall project paid for itself in a little over 12 months.

“With Varner being a high-use building, staying on all the time, we saw the maximum amount of savings possible,” said Conger. “It really got us excited and thinking about using these sensors across campus.”

The Hardin Hall project grew out of discussions of increasing the efficiency of fume hoods in Natural Resources lab space. Wilhite said Jim Hines, director of Building Systems Maintenance, presented fume hood options with Natural Resources’ sustainability committee – which in turn wanted to do more.

“We started to discuss other options and Jim was pleasantly surprised,” said Wilhite. “That brought us to the occupancy sensors.”

Building Systems Maintenance procured funding for the project, and the installation of the 173 Hardin Hall sensors began Dec. 1.

“It really was great to have Natural Resources step up and volunteer to use these sensors,” said Conger. “Typically, we feel like we have to really go in and sell what these things can do for UNL departments. But, in the case of Hardin Hall and Natural Resources, energy conservation fits into their culture.”

As the university moves toward an energy savings initiative and with an uncertain national economy, Wilhite expects the sensors to become more accepted.

“It’s going to cost some money up front, which is going to take some serious dedication in the current economic climate,” said Wilhite. “But, it comes down to where the rubber meets the road – these sensors are going to save money and natural resources. That just makes sense for the future of the university.”

— Story and photos by Troy Fedderson, University Communications

How do the sensors work?

• Sensors turn lights and HVAC systems on and off by detecting temperature changes. When a sensor detects a warm body, lights and HVAC systems operate as normal.

• After 10 minutes of no detectable motion, lights are turned off and the thermostat is placed in standby mode. The thermostat standby mode allows the room temperature to float a couple of degrees high and low of the set temperature. Extra ventilation is also curtailed. The HVAC control saves more energy than turning off the lights.

• Lights and HVAC systems reactivate when the sensor detects the return of a warm body.

• The sensors do not emit ultrasonic waves or other sensing media. A red LED inside the sensor dome (pictured above) blinks when motion is detected.

• Light switches linked to sensors continue to operate as normal. When the switch is on, the sensor will turn the lights on and off automatically. When the switch is off, the sensor can activate the thermostat standby mode but does not adjust lights.

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