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The German high-speed train ICE has made the headlines last week due to air-conditioning failures and passengers discomfort. The trains' air-conditioning systems are simply not laid out for long heat waves. The German environmental NGO Deutsche Umwelthilfe suggests to choose in this case CO₂ technology for train air conditioners.

Temperatures reached up to 50 degrees Celsius on an ICE train from Berlin to Cologne on July 10 after the cooling system broke down. Several passengers and nine students on a class field trip were subsequently hospitalised when they got off the train in Bielefeld.

The rail company Deutsche Bahn claims that the trains' failing air-conditioning systems showed neither manufacturing defects nor negligent maintenance. They are simply not conceived for the kind of intense heat that Germany was exposed to in the last weeks.

“An A/C system only functions in the predefined temperature range”, says Markus Hecht, Professor for air-conditioning technology at the University of Berlin. “The currently installed air-conditioning systems in the ICEs have not been designed to withstand weeks long hot periods such as we had this summer.”

This is bad news for German train travelers considering that climate change is on our doorstep. Scientists from Hamburg's Max-Planck Institute for Climate Research estimate that due to global warming Germany's summer will generally get a lot hotter with degrees above 30°C becoming the norm in July-August. It thus becomes all the more important to have efficient and reliable air-conditioning in the trains that transport around 1.9 billion passengers every year, according to the Deutsche Bahn.

Consequently, the rail company will have to revamp their under-performing air-conditioning systems. Stronger compressors or higher capacity heat exchangers would increase the cooling performance. They would, however, also need more space which in the current layout of the wagons where the A/C units are fitted just above the entry doors, is not available.

But the problems do not stop there. Besides being too small to keep up with the higher ambient temperatures, the current air-conditioning units are also contributing themselves to climate change. The refrigerant in use is R134a (Tetrafluorethan) which is classified as super greenhouse gas, having a global warming potential (GWP) 1,400 times higher than CO₂.

According to the German Environment Agency UBA, the average leakage rate from A/C units is 15% which translates into 2,300 tonnes of R134a leaking from cars and 14,000 tones of R134a leaking from train wagons and venting into the atmosphere. This corresponds to emissions from 1.7 million passenger cars in one year.

“A conversion to a more climate friendly refrigerant in trains would also be an important step to bring down emission”, says Wolfgang Plehn from the UBA.

And reliable alternatives exist: air-conditioning systems using CO₂ as refrigerant. CO₂ shows a high cooling performance, is safe for use and widely available.

“Tests with cars A/C systems have demonstrated that well designed CO₂ systems outperform R134a in hot ambient temperatures”, says Eva Lauer from the German environmental group DUH. They say that the new Intercity-fleet to be introduced from 2014 on, should be R134a-free. A suggestion that BeyondHFCs wholeheartedly supports.  

Since the train heat debacle the last weeks, the Deutsche Bahn has put the need for a better refrigerant at the top of their agenda. Let's hope that technological performance and environmental concern will guide them to choose CO₂ for future air-conditioning systems.