Zach Elementary School (Fort Collins, Colorado) Report of Daylighting Measure Impacts

Transcription

1 ENERGY SMART SCHOOLS: Applied Research, Field Testing, And Technology Integration Zach Elementary School (Fort Collins, Colorado) Report of Daylighting Measure Impacts NOVEMBER 2004 Published by the Energy Center of Wisconsin for the United States Department of Energy and National Association of State Energy Officials (NASEO) 455 Science Drive, Suite 200 Madison, Wisconsin

2 PROJECT OVERVIEW The Association of State Energy Research and Technology Transfer Institutions, Inc. (ASERTTI) and the National Association of State Energy Officials (NASEO) with the Department of Energy (DOE) and the EnergySmart Schools Program conducted a joint project that encompassed applied research, field testing and technology integration. The following organizations worked collectively to conduct this research: Energy Center of Wisconsin Iowa Energy Center Lighting Research Center Lawrence Berkeley National Laboratory Dalhoff & Associates Fort Collins Utilities As part of the overall project there were eight distinct tasks outlined, each with its own set of goals, activities and deliverables. This document was created as part of Task 4: Advanced Daylighting Research.

3 Facility Description Zach Elementary School in Fort Collins, Colo., opened in 2002 and features classrooms designed around daylighting principles. Electric lighting is controlled by one of two sets of roof-mounted photosensors, depending on whether the classroom faces north or south. Classrooms have tinted view and clerestory windows, with overhangs providing shade on the south clerestory windows. North view windows and south clerestory windows have Venetian blinds; south view windows have perforated roller shades. Ceilings slope away from the windows to increase reflectivity into the classroom. FIGURE 1. TYPICAL NORTH CLASSROOM AT ZACH ELEMENTARY We compared electricity usage in four classrooms. Rooms 121 and 133 are second-floor classrooms on the north side of the building and are controlled by the north photosensor control. Rooms 140 and 141 are larger, ground-floor kindergarten classrooms on the south side of the building and are controlled by the south photosensor control.

4 Lighting for each classroom consists of a bank of windows on one wall and, parallel to this wall, four rows of OSI T8/841 lamps. These lamps are contained in 4' 2-lamp 277V Finelite Series 4 direct/indirect fluorescent pendant fixtures with static ballasts and perforated metal reflector "wings" that direct uplight to the ceiling. The lamps are operated by a two-stage photosensor control and two switches, allowing for bi-level control of each fixture. FIGURE 2. FINELITE SERIES 4 PENDANT FIXTURE DEMONSTRATING BI-LEVEL CONTROL FIGURE 3. ROOF-MOUNTED PHOTOSENSORS

5 The first switch operates the manual lamp rows. The second switch operates the photocontrolled lamp rows, which will activate depending on the amount of available sunlight. Specifically, the photosensors will turn off the exterior row upon sensing an adequate amount of daylight (level 1 control), and will turn off the interior row as daylight increases (level 2 control). FIGURE 4. SECTION VIEW OF CLASSROOM SHOWING LAMP PLACEMENT AND SLOPED CEILINGS FIGURE 5. TYPICAL SWITCHING DIAGRAM Lamps closest to window switch off first (level 1 control) Manual Light Fixtures Lamps furthest from window switch off second (level 2 control) Manual

6 In rooms 140 and 141, which are larger, there are two additional rows of manual lamps, and separate switches for each photo-controlled lamp row. 1 FIGURE 6. SOUTH CLASSROOM AT ZACH ELEMENTARY 1 Instead of two switches as in rooms 121 ad 133, rooms 140 and 141 have three switches one for manual lights, one for level 1 control and one for level 2 control because they are larger kindergarten classrooms, and the nature of their occupancy means that sectors of the room will be unoccupied for long periods (for instance, messy activities are always conducted on the tiled floor instead of the carpeted floor). The additional switch is not about allowing room operators to reduce the overall lighting load but about allowing them to better control which sectors of the room are lit.

7 Monitoring Plan The operation of these lamps was monitored from February 27 to May 28, The only data considered were those collected during regular school hours and any other periods of substantial occupation (approximately 54 days). Four classrooms were monitored two on the north and two on the south. To determine the operation of lighting in these classrooms, Hobo data loggers were used in the classrooms and lighting control panels In each of the classrooms, a single multi-channel Hobo logger recorded the output from current transformers (CTs) connected to the manual lamps and each of the two banks of photo-controlled lamps (three CTs total). Approximately five loops of the power wire were made through the transducer donuts to increase the detected current of the 20 amp CT in order to give clear on/off status of the lights. In the control panel another multi-channel logger recorded photosensor output (0-10 VDC) and status of each of the two relays (0-24 VDC) controlling the automatic light rows in the classrooms. Voltage dividers were used to scale the device voltage ranges to be within range of the VDC Hobo input cables. The photosensor data represent input into the PLC Multipoint controller and the relay status represents controller output. All Hobo loggers were set up to record every four minutes. A delayed start was used so they would all record the same four-minute intervals (as opposed to being staggered). Each north classroom has one wall switch for manual lighting and one to enable/disable the two photo-controlled lighting circuits (two total). Each south classroom has a manual wall switch and one each for the two photo-controlled circuits (three total). With the monitored data one could determine the status of switches in the classroom, with the exception of one case, as shown in the following table. However, this case is not significant, since the lights would be off regardless of the switch position. TABLE 1. CLASSROOM SWITCH STATUS CURRENT TO MANUAL LIGHTS (CLASSROOM LOGGER) CURRENT TO AUTOMATIC LIGHTS (CLASSROOM LOGGER) RELAY STATUS (CONTROLLER LOGGER) STATUS OF SWITCH FOR MANUAL LIGHTS STATUS OF SWITCH FOR AUTOMATIC LIGHTS Yes No Off On Unknown No Yes On Off On No No On Off Off

8 Results The following table and figure show the performance of these lighting schemes in each classroom. As explained on page 3, level 1 control refers to the exterior photo-controlled lamps being deactivated because of adequate daylight, and level 2 control refers to the interior photo-controlled lamps being deactivated because of adequate daylight. TABLE 2. HOURS OF OPERATION PER WEEK CONTROL STRATEGY MANUAL LEVEL 1 LEVEL 2 SAVINGS RELATIVE TO SAVINGS RELATIVE TO ROOM NO. HOURS HOURS MANUAL HOURS MANUAL % 26 34% % 33 28% % 20 58% % 44 2% Mean % 31 30% Adjusted mean (w/out rooms 140 & 141)* % 30 31% * The reason for this adjustment is discussed above. FIGURE 7. WEEKDAY LIGHTING PROFILES Fraction of time on ROOM 121 ROOM 133 ROOM 140 ROOM Hour of day Manual Level 2 Level 1

9 The profile shapes conform to expectation both switches are activated in the morning, and as the sun rises, the level 1 photo-controlled lamps turn themselves off, to be followed by the level 2 photo-controlled lamps. Over the noon hour, the lights are sometimes manually deactivated, as demonstrated by the dip in the manual profiles. In the afternoon, the photo-controlled lamps often reactivate, and are manually turned off at the end of the day. (The tail after hour 18 can be attributed to custodial staff.) Because rooms 121 and 133 share the same photosensor, you might expect the weekday profiles of their photo-controlled lamps to better correspond, and the same could be expected of rooms 140 and 141. That they are not identical shows the importance of individual operator control. Rooms 121 and 133 show the effects of small differences in operator control the operators of those rooms seemed to keep both switches activated more or less all the time, with the photo-controls doing their job to reduce overhead lighting when necessary. 2 Rooms 140 and 141, on the other hand, show significant differences in control. The lighting control system for rooms 140 and 141 was miscalibrated in such a way that the photo-controlled lamps would activate even when daylight was greater than the design threshold. These classrooms have adjacent locations and comparable occupancy periods, meaning that operator behavior is the most important variable. Specifically: The operator of room 140 usually kept the photo-controlled lights switched off, as if the room lights and daylighting provided enough light. 3 The operator of room 141 usually kept the switches activated more or less all the time, even though the photo-controls did not make significant reductions in overhead lighting levels. In room 140, the interior photo-controlled lamps were off 56 percent more frequently than in room 141, and the exterior photo-controlled lamps were off 47 percent more frequently. A comparison to table 2 shows that these are significant reductions, and confirm that operator behavior will always be an extremely significant factor in just how great the savings will be from an energy-efficiency measure. Each set of photosensors is hooked up to a PLC-Multipoint lighting control system, which switches lamps in the daylit portions of classrooms, as well as the gymnasium, stairwells and the media center. According to the school s energy manager, the miscalibration of the south photosensor is related to the installation of this system. While the performance of the north sensor and control system seems reasonable, the south sensor and control system have not worked properly since installation, including the entirety of the monitoring period. 2 During those periods when the photosensor would tell the lamps to turn off, we cannot distinguish between the photo-controlled lamps being deactivated by the lighting control system or being manually switched off. 3 Another possible reason for keeping the photo-controlled lamps switched off is that, according to the school s energy manager, some room operators disliked the lamps cycling between on and off as daylight levels change.