Swarthmore College
IN-26: Innovation C

A Building Management System, or an Energy Management System, allows for an operator at a head station to monitor and schedule Heating/Ventilation/Air Conditioning (HVAC) and lighting loads. Swarthmore's Siemens BMS is a critical part of our infrastructure as it allows us to reduce our energy loads to an absolute minimum as well as providing valuable feedback for trouble shooting equipment in the field. Currently we monitor 24,000 points with more points being added every year. With the system we are able to pull up individual room conditions, machine status, outside air conditions and a variety of other sensors that give us a very detailed picture of what is happening in individual buildings. The extensive integration of BMS systems and scheduling of spaces has helped to significantly reduce the HVAC load. One of the unchallenged truths of energy conservation is if lights and systems are off you are saving energy. We tested this at Swarthmore in the library compact shelving stacks where it was observed there was a lot of light over book shelves that rarely had foot traffic. Placement of motion detectors was impractical given the height of the stacks so we elected to place individual circuits on timed push buttons connected to our energy management system to track the on/off cycles. The results were surprising: in a little over a year where we would have seen the lights “on” 10,600 hours according to the Library schedule, the push buttons were actuated only 510 hours out of that time period saving 33,000 kWh. It was such a successful project that we carried the concept to the rest of the library stacks on four floors netting an annual reduction of 242,000 kwh annually. We reasoned the same principle could be applied to scheduling HVAC in rooms that have individual room controls. We ordinarily apply strict control of HVAC in spaces according to the classroom occupancy schedule provided by the Provost. If it is not in the schedule, it does not go on. The weak point in that strategy is our energy manager has no indication if the space is actually occupied. This was especially apparent with summer programs where large blocks of time were requested but visual spot checks indicated the rooms were often empty. Again, taking advantage of our Energy Management System we were able to schedule a time period a room could be “on” but the system would not actually turn on the heat or AC unless a push button on the thermostat was pressed. This was also helpful after hours where an impromptu gathering could meet in a room and actuate the HVAC system for a fixed period of time. We did not want to go the route of an occupancy sensor as we did not want to provide HVAC if a single student walked in to find a quiet space to study. As in the library example, we were able to track how often the push button was pressed and were surprised again by how infrequently the button was pushed. We have no solid figures as to how much energy might have been saved, mainly since occupancy was highly variable.