Refrigerated container manufacturer Thermo King ‒ a brand of Trane Technologies ‒ is set to test a direct expansion propane (R290) prototype of a maritime shipping container (reefer), according to Laboratory Manager and Core Refrigeration Lead Santiago Martinez.
The prototype is the result of a collaboration with the GIZ (German Society for International Cooperation) to develop a proof of concept for R290 reefers as commissioned by the International Climate Initiative and the German Federal Ministry of the Environment, Nature Conservation, Nuclear Safety and Consumer Protection. Other project factors include safety standards, operator training, performance modeling and validation testing.
Martinez, joined by Kirsten Orschulok, Lead of Greener Reefers Project at GIZ, outlined the modeling and technical status of the R290 proof of concept in a presentation at the ATMO MAC Summit 2025 × TU Berlin. The event was hosted by ATMOsphere, publisher of NaturalRefrigerants.com, in partnership with Technische Universität (TU) Berlin’s Department of Heat Transfer and Heat Conversion. It took place September 23–24 on the university’s campus.
“To meet the efficiency target, we’ve gone with a direct expansion architecture using a variable speed compressor with vapor injection through an economizer,” Martinez said. “Simulations of the expected performance conducted by the Universitat Politècnica de València [UPV] are quite promising.”
Performance objects of the R290 proof of concept use Thermo King’s R134a Container Fresh and Frozen (CFF) reefer as a baseline. With a maximum 2kg charge of propane, the unit must provide 6.4kW (1.8TR) cooling capacity at −18°C (−0.4°F) in an ambient temperature of 38°C (100.4°F) and a refrigerated range from −30 to 30°C (−22 to 86°F) in outside temperatures between −30 and 50°C (−22 and 122°F). The temperature control must be within CFF’s 0.25°C (0.45°F) in chiller mode and 1°C (1.8°F) in frozen mode.
Targets/modeling: The energy efficiency objective of the proof of concept requires the R290 unit to outperform the R134a CFF by 10%.
- “UPV modeling shows that, at 30Hz operation, the R290 design cuts power consumption by 7% compared to our R134a CFF reefer,” Martinez said.
- Based on extrapolating the data, it may cut energy use by 24% when operating at the compressor’s lowest frequency of 15Hz, he noted.
Addressing concerns: The operational mode risk assessment, led by the GIZ and U.K. consultant Re-Phridge, applies the existing safety standard for thermal containers with flammable refrigerants ISO (International Organization for Standardization) Standard 20854:2019.
- “Their ambitious assessment includes engaging with numerous industry operators, including technicians, terminal staff and ship crews,” Martinez said.
- “So many people can touch these global containers that we have to address the risks,” Orschulok said. “I approach it like an airplane passenger. Yes, there are risks, but, if we proactively address them, we can make an f-gas-free reefer that is as safe as possible.”
The finish line: Thermo King expected to start initial testing on an R290 converted CFF reefer at the Trane Technologies laboratory in the Czech Republic in October, according to Martinez.
- The company also plans to conduct leakage tests to quantify potential losses and generate data to support the risk assessment.
- By December Thermo King will finalize its component selection ‒ including the R290 compressor. The project’s timeline limits it to off-the-shelf components, and only one company manufactures an R290 compressor with vapor injection, Martinez explained. “We are now working with three manufacturers to get the right compressor,” he added.
- A Costa Rican fruit producer will validate the proof of concept in June 2026, according to Orschulok.
Quotable: “With what we have learned, when the market is ready for a propane reefer, Thermo King will be ready,” Martinez said. “The risk assessment and safety protocols developed by GIZ and Re-Phridge will help convince the different stakeholders that this is safe.”
“UPV modeling shows that, at 30Hz operation, the R290 design cuts power consumption by 7% compared to our R134a CFF reefer.”
Santiago Martinez, Laboratory Manager and Core Refrigeration Lead at Thermo King
