Eberspächer Sütrak, a German manufacturer of thermal management systems for buses and coaches, is set to produce its CO2 (R744)-based HVAC unit for electric vehicles at a new production facility in Przylesie, Poland.
The AC138 EVO, a roof-mounted unit, will enter series production this month for an unnamed international bus manufacturer, with the first vehicles equipped with the technology expected on European roads by the end of 2025, a company representative told NaturalRefrigerants.com. Eberspächer said that the unit will also be produced for other busmakers.
The manufacturer first announced the AC138 EVO at Busworld Europe 2023.
While the unit is currently optimized for R744, Eberspächer has indicated plans to develop the system for other refrigerants such as propane (R290). Further updates are expected at Busworld Europe 2025, scheduled for October 4–9 in Brussels.
The new facility will expand Eberspächer’s manufacturing capacity by roughly one-third, adding 12,500m2 (134,549ft2) of production space and enabling an annual output of up to 20,000 units across multiple production lines.
“The increasing demand for electric buses requires us to expand our capacities for bus air-conditioning systems,” explained Jörg Steins, CEO of parent company Eberspächer Group.
Innovative design
Designed specifically for hybrid and battery-electric buses, the AC138 EVO prioritizes energy efficiency and system simplicity, ensuring a longer driving range.
“Efficiency and reliability in bus units is really important due to the amount of energy required for climate control and the high number of operational hours,” explained Sebastian de la Coba, Team Leader of Bus HVAC Development at Eberspächer Sütrak, during his presentation at the ATMOsphere (ATMO) MAC Summit 2024 × TU Berlin. The conference was co-organized by ATMOsphere, publisher of NaturalRefrigerants.com.
“Efficiency and reliability in bus units is really important due to the amount of energy required for climate control and the high number of operational hours.”
Sebastian de la Coba, Team Leader of Bus HVAC Development at Eberspächer Sütrak
The system uses an air reversal concept rather than refrigerant reversal, simplifying the refrigerant circuit, which in turn reduces the unit’s weight and increases efficiency, he said.
“In our units, the heat exchangers always work in the same way,” he noted. “The condenser is always the gas cooler, and the evaporator is always the evaporator; we just reroute the air to one or the other, depending on the mode.”
The AC138 EVO’s intelligent software regulates air flaps for optimal temperature control while also recovering energy from exhaust air. The unit can operate in cooling mode by expelling heat outside while cooling the passenger area and in heating mode by extracting energy from outside air to warm the interior.
Testing has confirmed high efficiency even in extreme conditions, with cooling capacity maintained at ambient temperatures up to 50°C (122°F), de la Coba added.
The AC138 EVO comes in two models: a low-profile (250mm/9.8in) aerodynamic version for coaches and a shorter (2.8m/9.2ft) but taller (415mm/16.3in) version for city buses, both weighing 325kg (694.5lb). Each unit delivers 24kW (6.8TR) of heating capacity and 35kW (10TR) of cooling capacity.
The system is also suitable for vehicles with combustion engines.
‘Game-changing’ compressor
Eberspächer’s AC138 EVO integrates Dorin’s BOXÉR compressor, described as a “game-changer” in CO2 technology by Giacomo Pisano, Dorin’s CO2 Compressors Business Development Manager, at the ATMO MAC Summit 2024 × TU Berlin.
The compressor provides exceptional thermal insulation, separating high-temperature chambers from the oil sump for efficient heat dissipation. This innovation enables heat pump operation in extremely cold climates, with transcritical performance at evaporating temperatures as low as −30°C (−22°F) without requiring a booster or two-stage compressor.
According to Pisano, the flat four-cylinder design minimizes unit height and vibration levels, crucial for bus HVAC applications. Additionally, air-to-air and air-to-water heat pumps using this compressor can operate in transcritical mode at ambient temperatures as low as −25°C (−13°F) without supplemental electric heating.
New Eberspächer facility
The Przylesie site will host two new production lines, including the AC138 EVO, alongside relocated lines from Eberspächer’s existing Polish facility in Oława, which will continue producing heaters for all vehicle drive types. The site will also serve as the company’s central spare parts warehouse.
Eberspächer has incorporated sustainability-focused solutions into its new facility, significantly reducing its environmental impact. A photovoltaic system and heat pumps for HVAC have cut primary energy consumption by 70% and operational CO2 emissions by at least 50%, compared to standard buildings in Poland.
