Mobile air conditioning in rail vehicles

modern high speed train in the city in winterClick to enlarge
The air-conditioning systems in the ICE 3 class 403 train use ambient air for cooling.
Source: Deutsche Bahn AG

Rail vehicles include local and long-distance trains, suburban fast trains, underground trains and trams. The energy for heating is provided electrically or with diesel fuel. Mobile air conditioning systems in rail vehicles are usually charged with HFC refrigerants. HFCs, or hydrofluorocarbons, are very potent greenhouse gases.

Rail vehicle heating and cooling systems both produce greenhouse gas emissions. In 2012 some 106 tonnes of the refrigerant R134a leaked from rail vehicle air conditioning systems, which is equivalent to the greenhouse effect of 152,000 tonnes of CO2. The European Union intends to gradually reduce the production and use of HFCs and replace them with less harmful substances in a phase down approach regulated by the EU F-gas Regulation Nr. 517/2014.In some systems the combination of cooling with a heat pump function is possible which can reduce the energy needed for heating and therefore reduce CO2 emissions as well.

Alternatives to HFC air conditioning in the rail sector are refrigerant cycles with CO2 or systems based on air cycle technology. For CO2-based cycles, there were only a few tests in rail vehicles, whereas systems based on air cycles have been already in regular service for a number of years in one class of the ICE high-speed train. Solid data on the economic efficiency of these techniques are not yet available. A current research project is testing an optimised air conditioning system based on air-cycle technology in a train in regular service. The project is expected to generate knowledge on the performance and efficiency of air-cycle-based air conditioning systems over the whole life cycle.