AS I struggled to drive a hired SUV up a particularly steep dirt track, my passenger offered some sage advice: 鈥淭urn the aircon off.鈥� I did 鈥� and the car practically took off, showing just how much power it takes to run a car鈥檚 air conditioner.
And if aircon is a strain even for a standard car, it鈥檚 a challenge to the very raison d鈥櫭猼re of petrol-electric hybrids, says Tom Robinson of Ricardo, an automotive engineering firm in Shoreham-by-Sea, West Sussex, UK.
The problem is that when a hybrid is set to 鈥渆conomy鈥� mode 鈥� in which the combustion engine turns itself off when the car is creeping along in traffic or stationary 鈥� the aircon stops whenever the car does. That can leave the driver and passengers sweltering at every traffic light. As a result, many drivers of hybrids are turning off economy mode in order to keep the aircon working, Ricardo says. So, many of these 鈥済reen鈥� cars may in fact be running like conventional gas-guzzlers. To prevent this, Robinson and his colleagues have developed a smart, location-sensing solution.
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鈥淢any of these 鈥榞reen鈥� hybrids may in fact be running like conventional gas-guzzlers鈥�
Aircons work by compressing a refrigerant gas and then allowing it to expand again, cooling as it does so. But compressors need a lot of power and so have to be driven by a hybrid鈥檚 engine, rather than from the battery.
Ricardo鈥檚 system uses GPS to plot the car鈥檚 position on a digital map that includes the location of traffic lights and junctions to anticipate when the engine, and the aircon, is likely to switch itself off. It then produces extra cool air to reduce the cabin temperature by a further 1.5 掳C 鈥� not enough to make the passengers shiver, but enough to tide the vehicle over while it is stationary.
Using the system slashed fuel consumption during typical urban driving by up to 9 per cent in climate-controlled tests carried out by Ricardo engineers working with the Transport Research Laboratory in Wokingham, UK, and the car manufacturer Jaguar Land Rover.
There鈥檚 a catch, however. They found the system delivers the best fuel savings at an outside temperature of around 22 掳C. So it鈥檚 fine for British weather, but won鈥檛 save quite so much gas for heavy aircon users in places like Florida.
