The heating and air conditioning systems used in vehicles to control the cabin temperature are complex systems. In fact, the systems used to heat and cool require a significant amount of design, and also consume a lot of energy. So much energy, that the driving distance of electric vehicles is frequently reduced when either heating or air conditioning is used in the cabin while driving. A study done by AAA showed that using heating or cooling systems in vehicles while driving can reduce the range of electric vehicles by as much as 41 percent. This significant reduction in range is largely unacceptable to automakers, who have been working to improve the efficiencies of such systems in a multitude of ways. The company Mahle is working on some solutions to this particular issue by adjusting the level of outside air to recirculated air used in heating and cooling processes. Outside air temperatures in the summer time are very high, compared to the air inside the cabin, and cooling the cabin air takes a lot of energy. If the cabin air is recirculated, it takes less energy because the same air is recirculated over and over. Mahle set up a test to determine if the level of recirculation of cabin air in a test Chevrolet Bolt electric vehicle could properly condition the cabin air to a comfortable level. The results of the test suggest that a 30 percent level of recirculation to outside air provided enough outside air to keep the cabin air humidity level at an acceptable level, as well as conditioning the cabin air to a comfortable level while minimizing the reduction in vehicle range. Improvements to airflow, including a combination of recirculated air to outside air, was shown to provide the best results, and at the lowest cost system to produce.
-article taken from www.sae.org