Unitary DX split-system and package air conditioners and heat pumps are ubiquitous in the Department of Defense (DoD) facilities and most of them do not perform to their designed efficiency due to incorrect sizing, lack of maintenance and/or age of the equipment. The energy efficiency of current unitary HVAC systems is much lower than that of distributed chilled water systems and few cost-effective choices exist for increasing their energy efficiency. The large potential for improvement makes unitary systems an outstanding target for DoD facility energy efficiency upgrades.
The objective of this demonstration is to increase energy efficiency and reduce energy consumption of the target unitary DoD air-conditioning equipment using the Energy Efficiency Ratio (EER) metering and feedback control technology. The performance metric EER is defined as the quantity of cooling provided per unit of electric power consumed, Btuh per Watt. EER varies greatly with cooling load, refrigerant level, maintenance condition and airflow, age and wear and tear, among other factors. The on-board technology monitors and maximizes EER by continuously adjusting fan speeds, refrigerant level and flow, and any/all other operating parameters in an operating unit, as cooling load and operating conditions vary.
The major objectives included:
• Establish the cost effectiveness of the technology in both onboard and portable versions.
• Document the reliable operation of onboard EER Optimizer technology.
• Document practicality, usefulness, and simplicity of diagnostics.
Three demonstration sites provided a full range of conditions for the EER Optimizer technology to evaluate the flexibility and efficacy needed for the widely varying climates of U.S. Department of Defense (DoD) installations. The demonstrations included onboard controls installed on operating package air conditioners at sites in South Carolina, Florida, and California, as well as use of handheld EER Optimizer technology to demonstrate effectiveness when used as an Operations and Maintenance (O&M) tool by Heating, Ventilation, and Air Conditioning(HVAC) technicians.
The EER Optimizer® minimizes direct expansion (DX) air conditioner energy use by measuring real-time operational efficiency. It is a versatile diagnostic and control technology that measures the EER of operating direct expansion air-conditioner and heat pump systems. The EER Optimizer provides easy web access for monitoring and reporting EER, Integrated EER (IEER), and Tons Capacity, and detects faults such as low refrigerant, stuck Thermostatic Expansion Valve (TXV), restricted airflow, broken economizer and fouled coil, all viewable at EERoptimizer.com The portable version is web connected for remote technical assistance, storing readings on a cloud server for later retrieval and analysis, and to support evaluation of historical trends, reporting, and documentation.
Incorporating the results of this demonstration into policy, training, and Heating, Ventilation and Air Conditioning (HVAC) management, design and procurement standards would contribute significantly to addressing the potential for efficiency improvement in unitary HVAC equipment. Implementation of the technology is straightforward and the cost is low enough to meet payback period and return on investment thresholds for Energy Saving Performance Contract (ESPC) and Utility Energy Saving Contract (UESC)-funded projects.
The reduction in normalized air-conditioner energy usage averaged 28% among the three demonstration sites. Reduction at Fort Irwin was 30%, reduction at Marine Corps Air Station Beaufort (MCASB) was 24%, and reduction at Cape Canaveral Air Force Station (CCAFS) was 30%. All three units exhibited a significant increase in IEER and commensurate decrease in weather normalized energy use for a cooling season, relative to baseline IEER measurements. The average improvement in measured energy efficiency as IEER was 19.7%.
There was a wide variation in cost effectiveness across the three demonstration sites, and the payback period ranged from 3.2 to 5.8 years. Larger air conditioners in warmer climates using more energy will provide shorter payback period. The portable EER Optimizer’s fault detection and diagnostics provided energy savings averaging 22% over groups of 10 package air conditioners at each site.
The equipment service needs indicated by the portable unit produced payback periods ranging from 0.4 to 1.1 years, with savings-to-investment ratio (SIR) ranging from 1.0 to 2.4 for the thirty-packaged air-conditioners.
Overall, indoor air quality and thermal comfort were unchanged or improved, and temperature and humidity were more tightly controlled. There was reduction in the level and severity of unplanned and/or emergency repairs. The EER Optimizer system allowed project engineers to identify performance issues sooner and prevent more severe failures. Technicians using EER Optimizer stated that the remote fault detection and diagnostics feature is a key benefit for them. Overall, the occupant comfort perception survey responses were more positive for the test period than they were for the baseline period.
A key lesson learned centers around the condition of the air conditioner units selected for field retrofit. It is critical that equipment be well-maintained and in good operating condition. The applicable capacity range of DX Air conditioners for this technology is 10 to 100 tons (120,000 to 1,200,000 Btuh). Units that do not have the original factory compressors are not good candidates for retrofit. For units that are in poor operating condition, the cost of refurbishing or repairs to the equipment should be included in the project economic evaluation. In addition, EER Optimizer-enhanced Rooftop Units (RTUs) may be a viable and cost-effective replacement for aging chilled water cooling systems, especially if the reduction of water consumption is desired. Project buy-in from the installation HVAC maintenance shop and/or base maintenance contractor as well as the contracting officer is essential to successful implementation.
Project and procurement justification can be based on one or more of the following benefits:
• Continuously optimizes operational parameters to minimize energy costs while improving occupant comfort and productivity.
• Slows performance deterioration and potentially adds years of service life before replacement is needed.
• Provides a realistic and objective assessment of in-situ equipment operating condition to guide the repair vs. replace decision process.
• Detects and diagnoses faults for performing targeted preventive maintenance or supporting Performance-based Maintenance (PBM) to maximize cost effectiveness.
• Provides remote connection to identify issues before they become problematic, for faster response to an occupant complaint, and to enhance technician productivity.
Factory installations typically provide more attractive project economics than field retrofits. Specified DX package unit(s) are shipped to ClimaTek HVAC LLC from the Original Equipment Manufacturer (OEM) and then to the project site. Allow 8 weeks in the project schedule for installation, testing and shipping. For full functionality an internet connection will be needed. This can be provided by, in order of preference, (a) facilities Local Area Network (LAN), (b) installation VLAN, (c) Virtual Private Network (VPN) over dedicated Wide Area Network-Internet Service Provider (WAN-ISP), or (d) self-contained cellular. Cybersecurity features of the system include data encryption, layered credentials, two-factor authentication, and intrusion detection.