INDIA: Tata Motors, India’s largest car manufacturer, and German automotive supplier Mahle are to develop and test R1234yf and R152a in a secondary loop mobile air conditioning system.
The Secondary Loop Mobile Air Conditioning System (SL-MAC) project is backed by the United Nations Environment Programme and coordinated by the US-based Institute for Governance and Sustainable Development (IGSD). It is also receiving funding from the Climate and Clean Air Coalition.
In global moves to switch from higher GWP refrigerant R134a in car air conditioning systems, most manufacturers have opted for the mildly flammable A2L refrigerant HFO R1234yf. Although being widely adopted, the flammability of 1234yf is a concern in Germany where Daimler is looking to introduce models using CO2.
R152a has previously been considered due to its efficiency and greater capacity but its A2 flammability has hampered development. Its GWP of 124 is within the 150 maximum limit for car ac systems but cannot compare with 1234yf’s GWP of around 1.
Front and rear systems
A Tata vehicle based on a new generation platform for utility vehicles, consisting of a more complex architecture with front and rear air conditioning system, has been selected for this joint development programme.
In the SL-MAC system, the alternative refrigerants first cool a secondary fluid/coolant, which in turn cools the air to comfortable temperatures inside the vehicle cabin. According to the developers, this process would allows the safe use of slightly flammable refrigerants.
“As a part of our R&D efforts, we are committed to pioneering and inventing solutions to a greener future in the auto industry and this initiative is a step in that direction,” said Dr Tim Leverton, Tata Motors’ chief technology officer.
The new SL-MAC system, which is testing the low-GWP refrigerants, is expected to increase vehicle energy efficiency through engineering. This system will turn off the compressor during acceleration and will retain coolness when the compressor is inactive or the engine is turned off for a short duration, allowing rapid cool-down at re-start. In addition to the expected energy efficiency benefits (fuel saving of up to 3%), the SL-MAC system allows the use of refrigerants that should avoid flow into the vehicle cabin. The refrigerant never enters the passenger compartment and instead stays in the engine area. Only the coolant circulates through the interior air conditioning unit.
“We will be comparing the life-cycle carbon footprint of HFC-152a – with a higher GWP offset by higher energy efficiency – to the carbon footprint of HFO-1234yf, and we will be estimating the cost of manufacture and ownership for each system,” revealed IGSD director of research Dr Stephen O Andersen.