The objective of this Statement of Need was to identify, develop and test lower-global warming potential (GWP) alternatives to refrigerants in use by the Department of Defense. Of primary concern is development of an alternative to hydrofluorocarbon-134 (HFC-134), a refrigerant used in air- conditioning systems in various military systems. An alternative to HFC23 for use in very-low temperature operations is also of interest.

Alternative solutions should show the potential to provide cooling performance and efficiency equivalent to or better than current refrigerants to not only enhance the military mission, but to also reduce greenhouse gas emissions. Proposals may focus on any number of potential lower-GWP alternative solutions such as:

• Secondary loop systems that use hydrofluoroolefin (HFO) HFO-1234yf (or another low- GWP refrigerant) in the primary loop and a non-flammable fluid in a secondary loop that enters the crew/passenger compartment, including optimization to provide equivalent or better energy efficiency and potential operational benefits over legacy HFC-134a systems.
• Other commercially-available non-flammable refrigerants for use in equipment originally designed for use with HFC-134a and/or HFO-1234yf.
• Novel refrigerants or refrigerant blends that are nonflammable under battlefield conditions.
• Non-vapor compression technologies (thermoelastic, magnetocaloric, etc.).
• HFO-1234yf combined with other equipment/technologies to inhibit explosion and burning of the refrigerant and lubricant resulting from military-style threats.
• HFC-23 alternatives for very low temperature operations (-60 or -80°C that use HFC23, with a GWP of 12,400)

Proposals using alternative refrigerants or refrigerant blends classified as “non-flammable” under industry standards must include plans to demonstrate non-flammability against a military-style threat. Army Research Laboratory is currently developing a laboratory-scale test method to characterize the flammability of refrigerants facing military-style threats, so this may offer one method to demonstrate non-flammability. In addition, any refrigerant alternatives proposed must have a GWP of less than 750 to be considered, but refrigerant alternatives with GWPs of less than 150 are desired. The toxicity and potential health hazards of alternatives in the neat agent, blend, mixture or pyrolytic form should be considered for occupational exposure and in the event of system leaks or catastrophic failure that may expose personnel to the refrigerant.

Funded projects will appear below as project overviews are posted to the website.