Spheros, a German manufacturer of thermal management systems for buses and coaches, has announced its plans to unveil a new propane (R290)-based air-conditioning unit at Busworld 2025 in Brussels this October, expanding its lineup of natural refrigerant systems.
The REVO-E R290 is a fully electric emissions-free rooftop system and is the latest addition to Spheros’s REVO-E series, which has included the CO2 (R744)-based REVO-E HP R744 model since 2021. The series also features the REVO-GLOBAL, which uses R407c – a synthetic refrigerant and per- and polyfluoroalkyl substance (PFAS) with a 20-year GWP of 4,457.
“The series is designed to suit all types of buses and climate zones worldwide.,” the manufacturer has said. “With the REVO-E R290 and REVO-E HP R744, Spheros complies fully with the current F-Gas Regulation as well as upcoming PFAS restrictions, providing manufacturers and operators with maximum flexibility and long-term security.”
“With the REVO-E R290 and REVO-E HP R744, Spheros complies fully with the current F-Gas Regulation as well as upcoming PFAS restrictions.”
Spheros
Diversified functionality
Beyond cooling, the new propane system is designed as a flexible platform with multiple optional features, including a heat pump, heat recovery and integrated battery and component cooling.
Details around the unit’s architecture, capacity and refrigerant charge have not yet been shared by Spheros. However, the company has confirmed that the unit will enter series production towards the end of 2026.
Meanwhile, the REVO-E HP R744, originally developed for electric buses, has been redesigned to extend its use to coaches.
“An optimized architecture and new components enable a flat design, making the REVO-E HP R744 an ideal climate control solution not only for city buses, but now also for coaches,” the company said.
The CO2 unit delivers high heat pump capacity with low energy consumption in moderate climates and can also be equipped with integrated battery cooling. It can provide up to 38kW (10.8TR) cooling capacity in ambient temperatures of 35°C (95°F) and 26kW (7.4TR) heating capacity in temperatures down to −10°C (14°F), with a charge of roughly 3.8kg of R744.
Spheros will exhibit both the R290 and CO2 solutions at Busworld 2025, booth 317 in hall 3.
Expanding use of R290
Spheros is the latest manufacturer to move into propane-based thermal management for buses, following Eberspächer’s announcement earlier this summer that it will introduce R290 versions of its AC138 EVO and AC135 systems for buses and coaches.
Until recently, CO2 has been the dominant natural refrigerant in bus applications. However, propane is gaining traction as more manufacturers seek alternatives to f-gases.
The shift is not limited to buses. Propane is also making inroads in rail transport, with operators such as the Cologne Transport Agency, Finland’s VR Group and Munich’s suburban rail network opting for the refrigerant in their trains’ thermal management systems.
The growing role of natural refrigerants in mobile air-conditioning (MAC) applications will be examined in detail at the ATMO MAC Summit 2025 × TU Berlin, which will be held in Berlin September 23–24. The event is organized by ATMOsphere, publisher of NaturalRefrigerants.com.
