Shanghai Blog

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Some old pictures (14/3) from the hike in the mountains east of Taiyuan.


Posted: 28 Apr 2009

A common problem in China – the taxi driver refuses to turn on the air conditioner. They say it consumes too much fuel so they cannot afford to turn it on. But just how expensive is it to turn on that AC in reality?

Some webpages stated that the AC will increase the fuel use by up to 10% (a lot of factors to consider: air temp, a modern AC might be more efficient than an old one and so on. The cost of the AC should be more or less constant for different speeds so a 10% estimate seems a bit off). But anyway for driving in city traffic it will actually save you a bit of money turning off the AC and opening the windows. However, if the speed of the car is above a certain speed (for example 65 km/h) it will be more cost effective to turn on the AC and close the windows. This is because the increased wind resistance (proportional to the square of the speed) will increase the fuel use more than using the AC. But it will of course vary with different car models and how much you open the windows as well.
Mythbusters tried this as well, see http://kwc.org/mythbusters/2004/11/mythbusters_boom_lift_catapult.html but it seems their test was a bit unfair (not too unusual).

The best way to save fuel is anyway to turn off the AC and close the windows and only blow air through the car fans. So maybe the taxi drivers will refuse to open the windows as well in the future?


Posted: 28 Apr 2009

Lite bilder från förra helgen då jag var till Yangzhou och Nanjing.


Posted: 13 Apr 2009