Jan. 5, 2015

About These Projects

Please note that any CO2 avoidance figures or other savings mentioned in these project profiles are Princeton Facilities engineers' estimates made prior to undertaking the projects. The estimates are conservative and the actual figures may vary. Princeton's carbon emissions reduction goal, as stated in the Sustainability Plan, is to reduce emissions to 1990 levels by 2020.

Campus Energy Controls Center

Campus Central Control System
Campus Energy Controls Center
 
Another key component to Princeton's energy management program are building controls, specifically, replacing older pneumatic controls with direct-digital-control (DDC) technology. The University uses full direct digital control (DDC) in 125 buildings on Campus. All of the heaviest energy-use buildings are included. There are over 80,000 control points in the system.

DDC allows Princeton's energy engineers to take control of equipment that, in the past, was controlled at the building level. Part of having a campus-wide building automation system is being able to schedule equipment to run when it is needed it and cycle it off when it is not.

Controls System Optimization

Frick Chemistry Laboratory
Frick Chemistry Laborartory

Traditionally, building energy control systems are optimized (or tuned) as part of the building commissioning process. After a period of time, the controls are allowed to run unmonitored until there is a significant or obvios problem. But what if data acquisition, analysis, and optimization process continues after the building is commissioned? By tuning dynamically, or continuously, University engineers can evaluate energy saving strategies and modify them for best results on an ongoing basis. The data collected also provides an important tool for the diagnosis and repair of problems. The resulting energy savings has significant positive impact on the University's long-term greenhouse gas emissions.

Temperature Control

thermostat
A Typical Thermostatic Sensor on Campus 

Thermostatic sensors have been installed throughout the campus to collect temperature data. Some thermostatic sensors do not display the temperature, they merely sense it, while others not only sense the temperature but display it as well. The data collected by these sensors determines whether the system needs to increase or decrease the amount of heating or cooling sent to a particular area.

There are many types of thermostatic sensors located throughout the various spaces on campus. Some sensors which display temperature can be set to a temperature determined by the occupant within the standards set by the University Energy Policy. For occupied spaces, unless special circumstances warrant some change from the norm, the set point for heating should be 68 degrees. The set point for cooling should be 78 degrees. Detailed information about the University Energy Conservation Initiatives can be found here.

Energy Metering

touchscreen in Frick Chemistry
Frick Chemistry Laboratory Energy Kiosk

Princeton's energy management program is moving ahead with many energy metering projects on campus. While the overall steam, chilled water, and electricity production/usage can be monitored at the central utility plant, until recently, usage information for individual buildings was not available. 

Many buildings on campus are being fitted with usage meters for those utilities. That information can be tremendously valuable for planning purposes. The new Frick Chemistry Lab meters steam, chilled water, and electricity usage/production. (Frick has a solar panel array on it's roof so it is an energy producer as well as a consumer.) A touch-screen kiosk in the building's atrium makes the information available to visitors as well as engineers.

Lighting Sensors

The University uses a vast array of lighting technologies in a wide variety of settings. A good example are the newer systems in the office areas of Frick Chemistry Laboratory, Sherred Hall. The lighting control system is comprised of microprocessors and environmental sensors. These components combine to provide energy savings, increased comfort, and reduced maintenance.

Most of the system is invisible to the building’s occupants. While the energy savings can be dramatic, the effect of the system in offices or work areas is subtle. One can still turn the lights on and off manually, but the system will automatically turn off lights in unoccupied areas. Also, using the daylight sensor, the system will read the amount of light coming through the windows and adjust the brightness of the lights in the room to compensate.

This is not simply dimming all the lights in the room. One may notice that the lights nearer a bright window will dim more as they are not really needed, the lights further from the window will dim less, the goal being to have even lighting throughout the room. This is where much of the energy savings come from—a technique known as “daylight harvesting.” At night, or on very dark days, the lighting automatically goes to the preset “fully bright” setting.

Lighting - Daylight Harvesting

A Control Unit, Occupancy Sensor, and Daylight Sensor in Sherred Hall

LED Lighting

The University uses a vast array of lighting technologies in a wide variety of settings. Compact florescent lights have been in general use for many years and by 1990 they had supplanted much of the University’s incandescent lighting. The next generation of lighting technology, using LED’s or light emitting diodes, is being deployed in several areas. LED technology has found its way into many academic settings, outdoors, and display lighting. Plans are well underway for the conversion of Dillon Gymnasium to LED lighting. The University is also studying Jadwin Gymnasium for possible conversion.

LED-based lighting technologies compare favorably with CFL’s for several reasons. Properly designed and implemented, LED type lamps have the potential to last nearly twice as long as their CFL counterparts. Also, unlike most CFL’s, LED’s contain no mercury or phosphors so at the end of their service life, their disposal is less problematic. LED lamps are very tough with regards to vibration or impact and are more easily made to be completely recyclable and sustainable.