Light has a profound impact on people. Beyond basic visual needs, light also influences the health and wellness of building occupants. Lighting directly consumes about 30% of the energy in typical office buildings and up to 60% in typical non-refrigerated warehouse buildings (2016, Business Energy Advisor [BEA-2016]). As many buildings in the Department of Defense (DoD) portfolio start to age, lighting retrofit projects become cost effective, but not all solutions offer the same savings. The objectives of this project were to demonstrate energy reductions from integrating lighting, heating ventilation and air conditioning (HVAC), and plug-load management and enable occupancy-based control. The demonstration was performed at Tinker Air Force Base in Oklahoma City, OK, in both an office area (5,000 ft2) and a high-bay area (21,000 ft2). The technology is a commercially available advanced lighting control system with a dense network of sensors that is integrated with the pre-existing Building Management System.
This project demonstrated the deep energy savings possible by going beyond simple lamp replacements and instead incorporating advanced lighting controls enabled by a fine-grained sensor network with light-emitting diode (LED) luminaires. The project developed a holistic method to lighting retrofits, applicable to both high-bay and office environments on military installations. This holistic method integrated sensed occupancy needed for the advanced lighting controls into the building automation system and optimized the HVAC control and plug-loads accordingly. Other lighting retrofits incorporate ambient light sensors and occupancy sensors, but at a much coarser level. While those attempts need to control a zone of lighting around each sensor, this innovative approach to combine the sensor with the luminaire allows for a finer level of control which translates into deeper energy savings.
The cost effectiveness of this demo system was compared to a lower-cost tubular light-emitting diode lighting retrofit using the Building Life Cycle Cost tool. Assuming Oklahoma energy prices ($0.0524/kilowatt hour for electricity, $1.81/one million British thermal units for natural gas), this demo system achieves simple payback in 17 years, with a Savings-to-Investment Ratio (SIR) of 0.93. Lighting: The demonstrated lighting system achieved an energy savings of 69% compared to the baseline in the high-bay area. In the office area, the pendant fixtures achieved an energy savings of 71%, and the troffer fixtures achieved an energy savings of 67% relative to baseline usage. Plug-loads: The energy savings achieved by plug-loads over the demo period was 4% of the baseline plug-load energy consumption. HVAC: The HVAC energy savings in the high-bay area was 30% of baseline consumption. This significantly exceeded the performance objective of 20% savings. The HVAC energy savings in the office area was 12% of baseline. The energy savings of the total system (office + high-bay areas) was 26% of the total baseline, which met the performance objective. The cost effectiveness of this technology is highly dependent on the electric utility rate, and while the economic performance at Tinker AFG was not attractive this solution should be considered in areas with electric rates at or above the prevailing U.S. average energy prices.
These integrated solutions offer potential for significant energy savings as shown by the results from this demonstration. Compared to basic lighting retrofit solutions, this system requires more time and effort to commission in order to ensure the devices are tuned properly and communicating as intended. Even with the additional cost of design and commissioning for these integrated systems, the increased energy savings are more than enough to make the investment cost-effective in areas with average or above electric utility rates.