IRSA 2023 Proceedings: Waste Energy AC Technologies in H2-Multiple Units

Abstract

The Heating Ventilation and Air Conditioning (HVAC) systems require up to 40 % of the overall energy demand in regional railway vehicles. Improving efficiency of the whole train system is especially important in non-catenary or hybrid rolling stock, such as hybrid fuel cell multiple units. One approach can be the usage of unused energy (waste energy), which can be waste heat and pressure energy between tank and fuel cell system. Currently no market ready systems for rolling stock exist to utilize this waste energy and the potential of novel systems is not investigated sufficiently. Here we show a simulative investigation of a metal hydride refrigeration system and an absorption refrigeration system in a generic thermal car body. The results are evaluated on the basis of European standards (e.g. EN 50591) and two realistic tracks in Spain. The potential annual energy savings are highly climate zone dependent and vary between 795 kWh/a and 6106 kWh/a for the absorption refrigeration system and between 1547 kWh/a and 13226 kWh/a for the Hydrogen Powered Air Conditioning (HyPAC) system. The absorption refrigeration system is more sensitive to fluctuating fuel cell loads, whereas the HyPAC shows similar improvements for both tracks. Reducing HVAC energy demand needs to be investigated further and especially further improvements in the system design (sizing, material selection) can increase the energy improvements in future.