Energy efficiency and indoor thermal comfort of railway coaches: innovative heat recovery solution for HVAC systems

Passenger thermal comfort in railway coaches during the cooling season is often compromised due to the need for dehumidification and the absence of a re-heating (post-conditioning) stage, leading to suboptimal thermal sensation. This paper addresses this challenge by presenting a patented HVAC system designed to recover heat from the cooling loops of electric and electronic components, heat that is conventionally wasted by being discharged into the environment. While the primary aim of the proposed system is to enhance energy efficiency through heat recovery (investigated in a previous work), this study focuses on its application in improving indoor thermal comfort during the cooling season. By enabling re-heating as part of the cooling process, the system provides a practical solution to the discomfort typically experienced by passengers in such conditions. The effectiveness of the system is evaluated using a dynamic simulation tool developed in the MATLAB environment, tailored to analyse innovative HVAC system technologies, operational strategies, and control logics. A case study relative to a modern inter-regional train implementing the proposed system layout is presented, focusing on its impact on passenger thermal sensation compared to a conventional train configuration. The findings demonstrate a substantial improvement in indoor thermal comfort during the cooling season, showcasing the potential of the proposed system to significantly enhance passenger experience while maintaining sustainable HVAC system operations in railway environments.