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Siemens working to reduce the energy use of air conditioning systems in trams as part of Ecotram project

In extreme cases, heating, ventilation, and air conditioning (HVAC) can account for between 30 and 40% of a tram’s energy use. As part of the Ecotram research project in Austria, Siemens is now looking for measures that deliver cost savings without requiring any sacrifices in terms of comfort.

According to the partners participating in the project, it should be possible to reduce energy consumption for HVAC systems by at least 10%. The objective is to develop a simulation model for the optimization of a tram’s climate control systems.

Climate and ventilation systems for a modern tram consume around 100,000 kWh of electricity per year. There are numerous possibilities for cutting costs, in areas ranging from insulation to intelligent control systems. Extreme climatic conditions, for example, occur on only few days in the course of a year, but the systems are designed for such conditions and thus are oversized, which results in excessive weight. Using carbon dioxide sensors, it would be possible to adjust ventilation to the number of passengers in a tram. Another conceivable measure would be to shut off the heating or air conditioning accordingly before coming to a tram stop or tunnel.

In evaluating these savings ideas, the Ecotram researchers first measure the current power consumption of all the HVAC components. This involved subjecting a test tram to all the weather conditions encountered in a typical year by means of simulated operation in the climatic lab. The tram is currently in everyday service in Vienna, yielding field measurements to supplement the lab data. The data set should reveal which situations and system components account for the most energy use. Savings measures will then be assessed with regard to efficiency and the effects on passenger comfort.

The measurement data also flows into a simulation software that shows the thermal behavior of a tram on a range of different routes. This will enable Siemens to optimize the climate systems, in terms of efficiency and energy use, for trams and for any operation location.

Ecotram was launched in March 2010 and has a duration of 18 months; it is funded by Austria’s Climate and Energy Fund. In addition to Siemens, the project participants include the Vienna University of Technology, Vienna’s Wiener Linien public transport company, the Rail Tec Arsenal climatic testing lab, the climate control system manufacturer Vossloh-Kiepe, and the “Schieneninfrastrukturgesellschaft” (rail infrastructure company). The savings measures identified by the project are to be incorporated in a savings-tram prototype.


Henry Gibson

It is not mentioned if the trams are heated by electric resistance heating or by heat pumps. The use of flywheels or small batteries for regeneration at stops will, likely, save more energy than efforts to improve the air space climate. Free piston compressors now made by LG of Korea and operating with propane or other hydrocarbon can immediatly improve the efficiency of heat pumps for heating or cooling. Electronically modulated expansion valves can do the same. Ice storage can create a better balance between peak cooling demand and average demand. It can also average the heating demands as highly heated water or as a source of heat for the heat pump. ECOCUTE machines are also very interesting. ..HG..

Henry Gibson

The use of ZEBRA batteries in trams or, the equivalent Durathon batteries from GE, could bring benefits besides regeneration and quick heating of the vehicles interior. ..HG..

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