Italian compressor manufacturer Dorin’s novel CO2 (R744) compression technology is “revolutionizing” mobile HVAC systems, according to Giacomo Pisano, the company’s CO2 Compressor Business Development Manager.

The new compressor design improves the performance of the system when in heat pump mode, especially in extremely low ambient temperatures, he explained. This allows transport operators to completely avoid the use of electric heaters in winter months, enhancing system efficiency.

“This novel compression technology is really revolutionizing the industry of mobile HVAC,” he said. “It is really a game changer because you are reducing the weight of the cabin and improving efficiency.”

Pisano delivered these remarks during his presentation in the Transport and Mobile Air-Conditioning (MAC) Case Studies session at the ATMOsphere (ATMO) Europe Summit 2023. The conference took place September 19–20 in Brussels and was organized by ATMOsphere, publisher of R744.com.

“This novel compression technology is really revolutionizing the industry of mobile HVAC. It is really a game changer because you are reducing the weight of the cabin and improving efficiency.”

Giacomo Pisano, Dorin

Extreme temperatures

Europe is a region of extremes, with manufacturers having to design components and systems that can withstand temperatures as low as 30°C (−22°F) in the winter in northern countries like the U.K. and Scandinavia and as high as 50°C (122°F) in the summer in southern countries like Italy and Greece.

“CO2 offers a great option for both heating and cooling across the board,” said Pisano. “However, heat pump mode at −30°C is a big challenge.”

The standard compressor design, with its internal discharge plenum, offers limited capabilities for CO2 in heat pump mode due to its very high oil and discharge temperatures, he explained. This leads to issues with heat dissipation and compressor lubrication, he added.

Dorin’s novel compressor design reconfigures the discharge plenum to dissipate compression heat into the surrounding environment, which leads to lower oil and discharge temperatures. The offers the “perfect matching” with heat pump mode and a wider application envelope, he said.

According to Pisano, this secures a 60% better lubrication and enables transcritical operation, even at extremely low ambient temperatures.

He explained that there is no HFC capable of providing comfort heating at −30°C without the help of a vehicle’s battery, which then impacts driving capability and range.

Outperforms HFCs

To assess the efficacy of Dorin’s new compressor design in mobile HVAC applications, a 12-month field test was conducted on trains in Sicily, as part of systems built by Italian manufacturer CPA Elettronica.

According to the manufacturer, the systems are running “well, reliably and efficiently.”

CPA has also conducted simulations to compare Dorin’s CO2 compressor with an R134a-based alternative. In addition to being smaller and lighter, the CO2 component also outperformed the R134a option across all of Europe’s climate zones. Efficiency improvements were most notable in northern Europe, where CO2 outperformed R134a by 39%.

While R134a can see greater efficiency on some days, CO2 is more efficient overall throughout the year, said Pisano.

“Dorin’s novel design has proven to offer safe and efficient heat pump operation down to −30°C,” he said. “This proves that CO2 can completely replace HFCs and HFOs in trains, buses and trams.”

He noted that several manufacturers are now producing rooftop mobile HVAC units.

“This proves that CO2 can completely replace HFCs and HFOs in trains, buses and trams.”

Giacomo Pisano, Dorin