ATMO America: Energy Recovery’s PX G1300 Could Improve the COP of Transcritical CO₂ Refrigeration Systems by up to 15% at 95°F, Says Hillphoenix

Incorporating Energy Recovery’s PX G1300 pressure exchanger into transcritical CO₂ (R744) racks could improve COP by up to 15% in 95°F (35°C) ambient temperatures, according to Ousama Sabra, Senior Product Manager at U.S. OEM Hillphoenix.

Fardis Najafifard, Refrigeration Application Engineer at Energy Recovery, joined Sabra in a presentation at ATMO America 2025 to outline the energy consumption and performance data of two case studies. The event was organized by ATMOsphere, publisher of NaturalRefrigerants.com, and held June 11‒12 in Atlanta.

To test the technology, Hillphoenix installed a PX pressure exchanger on the CO₂ rack of a Canadian supermarket with a cooling capacity of 334MBH (27.8TR/98kW) and a Vallarta Supermarkets store in Salinas, California, with a cooling capacity of 740MBH (61.7TR/217kW). In 65°F (18.3°C) ambient conditions, the unit improved the COP by up to 7.9%.

“To compare the COPs, we took power measurements every three minutes, with the PX device rotating off one week and on the next,” Sabra said. “When we extrapolate the data curve line, we anticipate the pressure exchanger to provide a potential COP lift of 15% at 95°F ambient.”

Energy Recovery was awarded the ATMO America 2023 Innovation of the Year award for the PX G1300 pressure exchanger’s ability to improve the energy efficiency of transcritical CO₂ systems. “We have the PX pressure exchanger running in 10 sites total in the U.S. and Canada and 40 in Europe, with more coming,” Najafifard said, adding that units are also operating in Japan.

The testing: The PX unit, which replaces the high-pressure expansion valve in the CO₂ system, recovers energy and subcools the gas cooler outlet, Najafifard explained.

• Hillphoenix built a skid to enable the device to operate as part of the rack. “We tried two design architectures,” Sabra said. “The subcooling architecture provides better COP improvements than the parallel compression one.”
• Given that both test sites are in “milder climates,” Sabra indicated that Hillphoenix may install the unit in another location. “We will continue to take power measurements at high ambient temperatures to validate the 15% COP lift,” he added.

Managing resources: With the pressure exchanger aligned to subcool the CO₂ refrigerant, it also saves water.

• “While saving energy, the device allowed Vallarta to slash the water consumption of the store’s adiabatic gas cooler using recycled water technology by 98%,” Najafifard said.

Standard addition: Several OEMs, including Epta, Fieuw Koeltechnik and Kysor Warren, are in the process of integrating the PX device directly into their CO₂ racks Ricardo Freitas, Vice President and General Manager of CO₂ at Energy Recovery, told NaturalRefrigerants.com at Chillventa 2024. The event was held October 8‒10 in Nuremberg, Germany.

• Initially, the PX G1300 was added to systems after rack production via Energy Recovery’s Energy Optimizer Module, which is still available for existing CO₂ system retrofits.

Quotable: “We were skeptical about CO₂ with our first store in 2021 in Indio [California], but since then we partnered with Energy Recovery and installed the first PX system in the United States,” said Sandie Nunez, Store Development Manager at Vallarta Supermarkets, in a video recording shown at ATMO America. “Compared to stores with other refrigerants, we noticed the Indio store had zero issues. Now we operate four to five CO₂ stores with no problems.”

“When we extrapolate the data curve line, we anticipate the pressure exchanger to provide a potential COP lift of 15% at 95°F ambient.”

Ousama Sabra, Senior Product Manager at Hillphoenix