Exploring waste heat recovery in hydrogen internal combustion engine buses for absorption air conditioning

Abstract This paper presents the recovery of waste heat in hydrogen internal combustion engine (ICE) buses for absorption air conditioning, specifically through the integration of a double-effect lithium bromide absorption cooling system. The study reveals significant potential for effectively harnessing waste heat to meet cabin cooling demands. An energy balance analysis indicates that the waste heat generated by hydrogen ICE buses can adequately satisfy cooling load requirements when ambient temperatures are below 34°C, and remains capable of addressing over 80% of the cooling demand as temperatures rise between 35°C and 40°C, with a decrease in system coverage of approximately 4% for each 1°C increase in ambient temperature. Additionally, large buses exhibit superior energy efficiency compared to their medium-sized buses. To address onboard space limitations, a split lithium bromide absorption cooling system is proposed, featuring a rooftop cooling tower and compact integration of essential components within the bus. This configuration minimizes disruption to passenger space while maintaining system efficacy. The case study further demonstrates that the system can be implemented in large buses without compromising spatial efficiency, achieving a well-balanced combination of operational performance and passenger comfort while remaining compatible with urban transport and operational constraints.