An innovative waste heat recovery solution for HVAC systems in railway coaches: A path to enhanced energy efficiency

The energy consumption of the transportation sector has been steadily increasing in recent years, a trend expected to persist due to rising mobility demands. While the railway sector is widely recognized as one of the most energy-efficient transportation modes, primarily due to its high degree of electrification, its overall energy footprint remains substantial, with a global annual electricity consumption of approximately 280 TWh. This demand is projected to rise further, driven by modal shift policies, increasing passenger and freight transport needs, and ongoing investments in railway infrastructure. In this context, optimizing onboard energy consumption, particularly in energy-intensive subsystems such as Heating, Ventilation, and Air Conditioning (HVAC), is crucial for reducing overall energy demand and associated emissions. In this framework, implementing waste heat recovery and efficiency-enhancing technologies could help to align railway operations with long-term decarbonization strategies and global sustainability targets. In this context, this study presents an innovative and patented waste heat recovery system aimed at enhancing the energy efficiency of HVAC systems in railway coaches The proposed solution repurposes the thermal energy dissipated by the cooling circuits of onboard electronic components, typically operating at temperatures up to 50 °C, by integrating an additional heating coil into the HVAC system. To evaluate the system’s effectiveness, a dynamic simulation model, developed in MATLAB environment, was adopted to simulate a real railway coach, assessing its performance under three different climate conditions: Almería (Spain), Naples (Italy), and Freiburg (Germany). The results show significant energy savings for space heating: 81 % in Almería (2.9 MWhel/year), 48 % in Naples (4.7 MWhel/year), and 16 % in Freiburg (4.8 MWhel/year). Corresponding reductions in CO₂ emissions range from 0.38 tCO₂/year to 2.1 tCO₂/year per coach. These findings demonstrate the potential of the proposed solution to improve HVAC system performance, reduce environmental impact, and support the railway sector’s transition toward decarbonization.