Danfoss has published a whitepaper reporting that its Multi Ejector High Pressure technology, used in conjunction with parallel compression, achieves up to 21% total energy savings in transcritical CO2 booster systems compared to traditional booster configurations — with field tests conducted in two US supermarkets in different climate zones.
The test methodology: Danfoss engineers installed the Multi Ejector HP in a Hussmann transcritical CO2 booster system using parallel compression. A Danfoss pack controller managed variable receiver pressures and controlled rack operation, valve logic, and ejector staging. The system was tested in both a mild Midwest climate and a warmer southern climate, with the ejector tested both on and off under controlled conditions.
The results: At ambient roof temperatures exceeding 95 degrees Fahrenheit, the Multi Ejector provided an additional 13.4% energy savings on top of parallel compression alone. The total savings versus a traditional CO2 booster system without ejector or parallel compression reached 21%. The technology works by exploiting the Venturi effect to generate free compression, recovering energy that traditional systems waste as pressurised CO2 fluid is expanded.
Why this matters for the US market: Transcritical CO2 refrigeration has been widely adopted in Northern Europe for more than a decade, but its adoption in the United States has been slower partly due to efficiency concerns in warm climates. The warm-climate test results are significant because they directly address the primary objection to CO2 refrigeration in the Sun Belt and Southeast markets where US food retail and cold storage operators face the highest ambient temperatures.
The refrigerant transition context: As the US HVACR industry continues phasing down high-GWP HFC refrigerants under the AIM Act, CO2 as a refrigerant alternative is gaining commercial relevance in food retail and industrial cold storage. The 21% efficiency number makes the economic case alongside the regulatory case — operators who switch to transcritical CO2 and install ejector technology can realise both compliance benefit and meaningful operating cost reduction.
For commercial refrigeration contractors: The Danfoss Multi Ejector HP represents a product category that requires specialised commissioning and controls expertise. Contractors building commercial refrigeration competency in CO2 systems are entering a technically differentiated market where the skills premium is real and growing.
