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Office of Finance and Treasurer News


Understanding Building Use and Occupancy to Conserve Energy

By Josey Schwartz and Ravi Raman

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Earlier this year, Energy & Engineering re-organized strategically to establish a full-time Energy Conservation Team. The goal was to allow dedicated staff to “dive deeper” into our systems and the data we collect to develop new strategies that would conserve energy, provide good financial return to the university, and increase occupant comfort and utilities reliability.

When looking for places to conserve energy, the energy conservation team usually looks first to the building automation system (BAS). The BAS is essential to any energy conservation strategy because it provides a platform to control major energy-using systems in a building. For example, the BAS has the ability to put the Heating, Ventilation, Air Conditioning (HVAC) equipment, found in most buildings on the AU campus, on a schedule. HVAC systems account for the largest amount of energy use in buildings.

Recently, the AU Energy and Engineering (E&E) staff completed the first part of its in-house energy waste reduction program by reviewing equipment operating schedules for all buildings controlled by the BAS. The goal was simple: stop and prevent wasted energy used to heat, cool, and/or ventilate spaces when they are unoccupied. The program consists of three parts.

First, E&E staff created a consolidated list of campus building occupancy schedules, the HVAC equipment inside each building, and the equipment run times as they were scheduled currently. The team then used its powerful energy management tools and dashboard to analyze occupancy patterns in the building. By looking at the energy use intensity, E&E’s energy analysts were able to develop a comprehensive understanding of when people are in the building. From there the energy managers worked with their E&E colleagues who manage the BAS to set HVAC equipment to run in accordance with actual building occupant use patterns.

Next in the in-house effort to reduce energy waste, energy managers worked with BAS programmers to divide areas of each building into logical zones based on space use and occupancy. For example, there were air-handling units in residence halls that ran continuously to serve both students who occupy the building throughout the day and the offices on the ground floor that only worked during business hours. The units did not need to run overnight on the ground floor when staff members are not present. E&E’s BAS programmers grouped the equipment that serves the offices into a zone and set it to shut off during unoccupied times. Shutting off equipment when it’s not needed prevents energy waste, increases the life of the equipment, and reduces maintenance costs.

Juan Allen, Chief Engineer and technical lead for E&E’s Energy Team, noted, “Some buildings present themselves as obvious candidates for equipment operating schedule changes that should be made, while others may remain unchanged. There are some places, because of system complexity, age, or both, that require the use of new technology or more advanced programming to address the energy usage issues, and we review these on a case-by-case basis to ensure customer comfort while achieving energy savings.”

This is where the third part of the program comes into play. In places with air-handling units that are “constant volume,” meaning they provide maximum ventilation whenever they’re running, the E&E plans to install variable speed technologies that enable a range of outputs from the HVAC equipment to match the occupancy level’s ventilation and air-conditioning needs. Office spaces typically have a consistent schedule and energy load, but classrooms and other assembly spaces with variable occupancy uses are much trickier. However, using variable speed technology alone won’t reduce waste and optimize energy usage.

In cases where setting a static schedule is not possible, the E&E seeks to implement demand-driven strategies that are practical for many variable-occupancy situations. The space is fed a constant minimal amount of conditioned and/or outside air during occupied hours. Temperature, humidity, and CO2 thresholds are programmed into sensors that monitor a space constantly. Once a threshold is crossed – for example, if too much CO2 is detected, an indicator of a lot of people in the space – more conditioned air is brought into the space until the readings drop back to acceptable levels.

In addition to helping keep our community comfortable, energy reduction strategies divert carbon from entering the atmosphere, save money on electricity, extend the life of equipment, and lessen the frequency that operations staff must perform planned maintenance. Preventing energy waste and optimizing HVAC systems to support the university’s mission and programs are a delicate balance and very challenging. To reach the university’s goal of carbon neutrality by 2020, the E&E staff continues to seek creative solutions.