Texas district drastically reduces energy use through BAS and a hard look at sequences
February 26, 2007
The Crosby Independent School District (ISD) serves nearly 4,500 students in Harris County, TX, part of the Houston metropolitan area. The district includes six campuses: a kindergarten plus primary, elementary, intermediate, middle, and high school. It also includes both administrative and operational facilities among its assets. The district had Automated Logic DDC systems installed in their facilities beginning in 1998.
Recently the district upgraded to WebCTRL, Automated Logic’s Web-based BAS and began adding onsite utility metering hardware at the campuses. The district wanted to accomplish two goals: to reduce their energy consumption and improve the learning environment.
Both of these goals needed to be accomplished with a minimal investment. In May 2006, Crosby ISD contracted Automated Logic - United Environmental Services (ALC-UES) to evaluate its energy consumption and propose conservation strategies.
“ALC-UES saw an opportunity to capture energy and maintain an environmentally friendly atmosphere,” said Jerry Blizzard, Crosby ISD director of buildings and maintenance. “We had the potential to make a significant difference.”
Rolling up 1,800 pointsThe first challenge was how to identify the opportunities that offered the greatest potential for improvement both in energy consumption and in comfort. To obtain this information, Automated Logic’s M-Power product, a reporting tool that extracts granular data from existing BAS and formats it into energy and comfort-focused solutions, was implemented.
In Crosby’s case, M-Power extracted real-time data, including energy consumption, the space temperature deviation from setpoint, the space humidity deviation from setpoint, facility occupancy, and central plant runtime. It “rolled up” over 1,800 points of data to summarize the overall comfort and efficiency of each facility. As a result, staff could compare the efficiency of all facilities on a usage/sq ft/occupied hr basis and see which facilities had the greatest opportunity for improvement through energy conservation measures. “M-Power not only allowed us to troubleshoot our energy use, it provided information - simple, useable information - that we could take back to the school board,” Blizzard explained.
Optimized routinesThe changes were simple, yet effective. After reviewing building occupancy and central plant run-time, the team tightened occupancy schedules and the fine-tuned optimum start routines to reduce the actual HVAC runtime. Adjusting unoccupied setpoints on numerous zones stopped unnecessary activation of the HVAC equipment, and improving several control sequences boosted energy efficiency as well.
The facilities’ occupied setpoints returned to a standardized setting. The group identified zones that were not maintaining their comfort levels and made corrections. Engineered Air Balance performed air balance work for one wing of the middle school, which has fan-powered VAV boxes, and the classrooms are now able to maintain their setpoints throughout the day.
Another tactic involved modifying the district’s strategies for operating their facilities during the summer break. Crosby ISD is located near the Gulf Coast, and consequently, the facilities’ HVAC systems cannot be turned off for extended periods of time, even when unoccupied. Without some sort of dehumidification, mold growth would occur. To prevent this, other school districts in the area continue to operate their buildings during the summer break as if they were occupied.
Staff implemented a summer energy saving strategy for the buildings during the unoccupied summer break. The new scheduling runs the facilities for four hours during the weekdays while the outside air induction and exhaust fans remain off. Also, all of the single zone units could now cycle their supply fans off if they reached setpoint. This allowed for maximum dehumidification while the HVAC systems were operating. The hot water heaters were also shut down during the summer. This strategy produced significant energy reductions and prevented mold from forming within the facilities.
A measurable impactDuring the six-month period of May-October 2006, the district reduced energy consumption by more than 1.6 million kWh compared to May-October 2005, saving over $131,000 (calculated according to 2006 rates).
M-Power has been scoring the facilities from the inception of the project. All facilities are scored based on an Environmental Index, which represents how well a facility can maintain zone temperature, humidity, and CO2 at assigned setpoints during the occupied periods.
While reducing the energy consumption of the facilities, their comfort, as measured by the Environmental Index, improved. The facilities show an aggregate improvement of over 11 points on the Environmental Index’s 100-point scale. “We made an immediate, measurable impact not based on opinion, but on real-time data,” said Blizzard.