The objective of this project is to demonstrate the emerging technology of Flow Environmental Systems (Flow) air-to-water heat pump (AWHP) as a drop-in replacement for legacy heating and cooling systems at Department of Defense (DoD) facilities and to validate its cold regions performance. This design has potential to improve the heating and cooling efficiency of central heating and cooling systems along with simultaneous water heating, to lower operating costs, and to increase energy efficiency and security. 

The Flow AWHP uses a reciprocating compressor and a transcritical carbon dioxide (CO₂) refrigerant cycle to transfer high-grade heat to and from the existing hydronic heating or chilled water infrastructure in the building. This design provides high-temperature hydronic heating up to 180°F, medium-temperature heating up to 140°F for domestic hot water, and chilled water below 38°F for cooling. Unlike other state-of-the-art AWHPs, the Flow AWHP can deliver supply temperatures up to 180°F, thus enabling it to be a direct replacement for legacy hydronic systems. The AWHP can operate in cold region applications below -15°F and has a proprietary design to avoid defrost derating. Depending on operating conditions, CO₂ heat pumps can achieve efficiencies over three coefficients of performance exceeding the performance of conventional heat pumps. The AWHP will reduce summer peak electric demand compared to state-of-the-art chillers minimizing the need for electrical service upgrades. It can be installed in a split system or packaged configuration. The exterior footprint (gas cooler) is comparable to an existing cooling tower, and the interior footprint is slightly larger than an equivalent gas-fired boiler. 

A cold regions field site was selected for this demonstration at Naval Station Great Lakes. The AWHP will be installed at a Bachelor Enlisted Quarters in parallel with the existing gas-fired tankless water heaters and boiler/chiller hydronic systems to deliver water heating and space conditioning. The baseline equipment will remain in place to reduce any risks of outages and to supplement the AWHP capacity during peak loads. This demonstration will characterize the AWHP installed performance and validate the cold regions heating capacity of the system. This study will compare the AWHP measured energy use and the economics with conventional hydronic systems commonly used at DoD facilities to determine the economic and environmental benefits of the technology. The performance objectives and success criteria for the Flow AWHP demonstration include: 1) Deliver specified heating and cooling capacity across the range of ambient conditions, 2) Reduce summer electric demand, and 3) Reduce annual operation and maintenance costs. 

This Flow AWHP design offers a robust scalable solution to increase the energy efficiency and cost savings of space and water heating at DoD facilities across the U.S. The AWHP is expected to increase the space conditioning efficiency and reduce operation and maintenance costs while replacing multiple systems with a single heat pump. The project team will develop AWHP performance models based on measured performance data from this study to determine the most cost-effective applications from the existing 10,000 DoD facilities served by legacy hydronic systems and to promote the broader adoption of heat pump technology in both DoD facilities and commercial markets.