ESTCP researchers developed and validated advanced air conditioner units that improve building occupancy comfort and energy efficiency at DoD installations.
By Dana Fahey
Air conditioning units could reduce their own repair time and energy costs, thanks to an ESTCP technology that incorporates Artificial Intelligence (AI) software, more efficient components, and advanced controls.
Most Department of Defense (DoD) facilities rely heavily upon temperature and humidity regulation to sustain proper conditions for workers and sensitive equipment. However, maintaining the ideal temperature and relative humidity can be energy-intensive and expensive with standard air conditioning units. Critical facilities, such as laboratories, weapons storage and assembly places, and data centers, have more stringent requirements for indoor air quality that are difficult for standard air conditioning systems to satisfy. At these locations, failure of heating, ventilation, and air conditioning (HVAC) equipment can lead to very expensive interventions to repair or replace parts. Dr. Mike West and his ESTCP project team at Advantek Consulting developed and patented an HVAC system, the NexGen Packaged AC unit, that increases the efficiency and precision of climate control and complies with Federal mandates to work towards decarbonization.
As an engineering consultant, Dr. West has assessed hundreds of HVAC system issues. This experience, combined with his background in research and development, inspired his design to improve air conditioning unit efficiency and system reliability. In standard units, a typical response to a fault happens only when the performance of a unit degrades to the extent that occupants report discomfort. Dr. West and his team observed the lack of commercially available solutions that would detect malfunctioning and quickly resolve issues without customer intervention.
Figure 1: New 15-ton ClimaTek DX package installed at Cape Canaveral SFS.
Cutting-edge fault detection and diagnostics capabilities distinguish the NexGen packaged Air Conditioning (AC) units from standard units.
The team developed preemptive solutions by modifying the controls of existing packaged AC units to communicate with AI software, which detects when the system is not operating optimally and diagnoses the issue. When the system does malfunction, the software immediately alerts the technician via email or text and makes corrective adjustments. The fault detection in Dr. West’s technology eliminates this lag time between the beginning of a system failure, until maintenance is called, thereby reducing occupancy discomfort or a breach of desired condition set points while improving unit energy efficiency.
“Most of the packaged air conditioning equipment that DoD operates uses about twice the energy that new advanced technology does,” said West. “We sought to demonstrate [the capabilities of our] advanced package-unit technology and show that it could produce a 50% savings and improve comfort, and do so cost-effectively.”
To demonstrate the versatility and efficacy of their technology, the team tested it at two extremes of the environmental spectrum: Cape Canaveral, Florida and Fort Irwin, California. Cape Canaveral is in a wet, humid, and hot climate, with a mild winter. Fort Irwin resides on the other extreme: located in California’s Mojave Desert, this installation is in a very dry climate, which gets both extremely hot during the summer and cold in the winter. After establishing a baseline of traditional AC unit energy efficiency at both sites, they installed a NexGen packaged AC unit at Cape Canaveral and a NexGen heat pump version at Fort Irwin and compared the results to their baseline. Then, they analyzed data between the two different sites for the second year of NexGen platform performance.
The NexGen packaged units improved efficiency at both sites compared to their existing traditional units, yet the performance between the hot humid and hot dry climate differed significantly. At Cape Canaveral, the advanced unit was 54% more energy efficient than a new high-efficiency existing unit. A 46% efficiency improvement was observed at Fort Irwin. At Cape Canaveral, weather-normalized cooling energy use was reduced by 51%, and at Fort Irwin, weather-normalized cooling and heating energy use was reduced by 61%. This difference in efficiency and energy use reduction between Cape Canaveral and Fort Irwin was caused by their varied levels of humidity. Dehumidification requires a great deal of energy, which was needed at the Cape Canaveral site, but not at Fort Irwin, where cool dry outdoor air was utilized to supplement cooling.
“We were able to get more overall efficiency improvement at Cape Canaveral, but the energy use was less at Fort Irwin. The lesson learned there is that it depends on climate, how much savings [you’ll] get,” Dr. West explained. “This is because the efficiency is measured as the unit operates, like a car’s miles per gallon number, and the amount of energy used is more like amount of gallons a car would use over a long period of time… so even though [the unit] operates more efficiently [in Florida], it had to run longer to dehumidify.”
Figure 2: NexGen DX package unit touch screen panel and control electronics
Technically speaking, this heightened efficiency in humid climates is made possible by the precise control over the temperature of the cooling coil itself. In a standard unit, the cooling coils run at a constant temperature of 45-50 °F. This only allows for temperature adjustment by turning on/off the compressors via a thermostat. Standard units are thus unable to efficiently meet highly specific temperature and humidity requirements. The NexGen patented ClimaStat cooling coil can be adjusted from 32-52 °F. This wide operating range allows for a control system that is highly precise and variable. Additionally, the NexGen packaged AC units have a wall mount touchscreen control panel that has temperature, humidity, and carbon dioxide set points, to simultaneously monitor these three factors. These controls enable maintenance of a highly specific temperature and humidity climate that is critical for spaces that require precise and constant conditions, like laboratories or cleanrooms.
The project team made a few other fundamental changes to the unit that distinguish it from traditional models. While traditional units must stop and restart to adjust temperature of the space, the team’s unit maximizes efficiency with “inverter driven compressors and variable speed drives on the blower and fan, which lets the unit speed up and slow down to only deliver the amount of cooling needed to achieve the desired temperature.” Twisted airfoil fan blades also replaced standard flat blades for improved airflow.
The NexGen Packaged AC unit improves energy resilience on multiple fronts. It uses less energy by functioning more efficiently and provides users increased security in maintaining building conditions, with greater reliability of precise climate control made possible through advanced technology and fault detection capabilities. The project team is currently working to commercialize the product, so that it is more readily available to improve occupancy comfort and energy efficiency at a range of facilities.
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About SERDP & ESTCP
The Strategic Environmental Research and Development Program (SERDP) and the Environmental Security Technology Certification Program (ESTCP) harness the latest science and technology to improve the Department of Defense’s environmental performance, reduce costs, and enhance and sustain mission capabilities. The programs respond to energy and environmental technology requirements across the military services. SERDP and ESTCP are independent DoD programs managed jointly to coordinate the full spectrum of research and development efforts, from the laboratory to field demonstration and validation. For more information, visit https://www.serdp-estcp.org. Follow us on Twitter, Facebook, and LinkedIn.
