Package DX units are self-contained systems that enclose all components in one outdoor cabinet that sits on either the roof or to the side of a building. They use direct expansion (DX) of liquid refrigerant to produce cooling, and heating if they are heat pumps. The over 100,000 package units installed at Department of Defense (DoD) facilities have much lower energy efficiency than the best available technologies. This demonstration of next generation (NexGen) technology addresses challenging DX unit disadvantages and greatly enhances their performance. NexGen equipment provides twice the dehumidification capability at half the energy cost of conventional package equipment. Humidity control is vital for occupant comfort as well as meeting strict requirements for DoD laboratories, control centers, hardware assembly, electronic equipment, and warehouses. Additionally, next generation advanced DX equipment offers an economically viable replacement option for chilled water systems that are aging, where mission changes make a chilled water system upgrade not viable, or where elimination of cooling tower water consumption and maintenance is preferable.

Technology Description

NexGen units surpass current, future, and anticipated energy efficiency goals; meet demanding Energy Service Company cost, reliability and maintainability requirements; and meet new needs for remote automated fault detection and diagnostics. The technology is rendered via lower-cost, readily available components, which are uniquely compatible with DoD facilities design and maintenance realities. Performance optimization capabilities include independent control of cooling and dehumidification, comprehensive fault detection and diagnostics with automated performance optimization and technician alerts via text message, continuous adjustment of operating parameters to minimize energy use as load and weather vary, and secure connectivity and monitoring from anywhere.

Demonstration Results

Two representative package air conditioning units were replaced with NexGen units, at two locations in widely differing climates. At site 1, Naval Ordnance Test Unit Support Building at Cape Canaveral Space Force Station (CCSFS) on the Florida seacoast, equipment is a 15-ton cooling unit with electric heat. At site 2, Office of Staff Judge Advocate Building at Fort Irwin National Training Center in the California high desert, equipment is an 8½-ton heat pump providing cooling in summer and heating in winter. At the CCSFS building, heating ventilation air conditioning (HVAC) energy use was reduced by 48%. At the Fort Irwin building, HVAC energy use was reduced by 64%. The CCSFS unit highlights the much stronger dehumidification performance of the advanced units in a severely humid climate: monthly average space humidity was lowered to around 50%rh from the 70%rh baseline average.

Implementation Issues

The CCSFS advanced unit field-measured operational integrated energy efficiency ratio (IEER) 21.6 is 54% more efficient than a new high-efficiency model, which is over twice the efficiency level of the baseline unit’s Air Conditioning, Heating, and Refrigeration Institute (AHRI) rating. The advanced unit at Fort Irwin IEER 18.3 is 46% more energy efficient than a new high-efficiency model, and nearly twice as efficient at the baseline unit’s AHRI rating. Comfort improved measurably as well. The CCSFS comfort baseline was predicted mean vote (PMV) 1.0/predicted percent dissatisfied (PPD) 27% dissatisfied, which improved to PMV 0.39/PPD 8.8% dissatisfied with the advanced NexGen unit. The Fort Irwin baseline was PMV -0.6/PMV 13% dissatisfied, which improved to PPD 0.0/PMV 5.2% dissatisfied with the advanced NexGen unit. The NexGen units provide a more comfortable workspace while also saving considerable energy and easing maintenance tasks.