Half a croissant, on a plate, with a sign in front of it saying '50c'
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Absorptive refrigeration AC

Use exhaust heat to cool the car
  [vote for,

Almost a century ago, absorption refrigerators using just a heat source, with no moving parts were invented.

Why not use the method to cool the car from the exhaust's high temperature and heat discharge?
It will save fuel normally used to spin the AC compressor. Specially on slow, hot summer crowded traffic. It would be cheaper and more reliable.

It could also freeze water in an insulated container, for cold storage - e.g. have cooling running for long after engine was stopped, or start cooling instantly, before engine starts.

blimpyway, Jun 17 2006

http://en.wikipedia...rption_refrigerator Wikipedia page on absorption refrigerator [blimpyway, Jun 17 2006]

icyball http://en.wikipedia.org/wiki/Icyball
Icy ball refrigerator [blimpyway, Jun 17 2006]

Gas Saving Automotive Air Conditioner http://www.teenink....Past/1995/5880.html
In this study they used heat from the catalitic converter. [blimpyway, Jun 17 2006]


       The next generation of cars will shut down their engines at stop lights. So this will not work in city traffic. Sorry, great idea, ten years too late.
Galbinus_Caeli, Jun 17 2006

       Have you reach reading the cold storage paragraph? The one mentioning freezing water. Even without it, still doesnt need extra fuel for spinning an AC pump.   

       An idling engine with AC on wastes much more fuel than an idling one with AC off. So unless you suggest another solution, on a hot day people will either turn the engine on just for the cool or cook themselves inside.
blimpyway, Jun 17 2006

       Sounds like it would be a good thing.
BJS, Jun 17 2006

       Sorry, I did miss the ice thing.   

       But as far as starting the engines, in next gen cars that is not going to be an option. The engine will shut down automatically rather than idle. Then restart when power is requested.   

       Even the "hybrids" that GM is offering do this.   

       So you need another source for your AC. The prius uses a dedicated electric compressor powered by the traction battery.
Galbinus_Caeli, Jun 18 2006

       //The next generation of cars will shut down their engines at stop lights// Didn't Fiat FIRE's do this about fifteen years ago?
AbsintheWithoutLeave, Jun 18 2006

       I wouldn't be surprised.   

       So did golf carts. Step on the gas to start the engine and go. Let off to roll to a stop and cut off the engine.   

       Now it is becoming mainstream. I suspect that within a few years hybrid drive trains of one sort or another will be as common as automatic transmissions were fifteen years ago.
Galbinus_Caeli, Jun 18 2006

       Since the IC engine in a hybrid runs intermitently, at possibly long intervals, the Prius had no choice but to use an inneficient electric-powered air conditioning.   

       It uses at least the same if not more primary fuel than an standard, engine driven aircon - there are extra inefficiencies in converting engine power in electricity, puting that in baterry, then extracting electricity from batt to put it into compressor.   

       An absorbtive refrigeration aircon would work like this in a hybrid:
- As long as the IC engine is running use its heat to freeze a couple of gallons of water in a box.
- cool the car's interior by venting air through pipes passing through the ice box.
- The couple gallons of ice would suffice to keep passengers cool for at least half an hour. Since the engine is so innefiecient there is a lot of heat available to provide excess ice to keep the car's interior cool for much longer time than the IC engine is actually spinning.
- when the engine starts later to recharge batteries, it will also recharge the freezer.
- no suplementary fuel is burned for AC, either indirectly or directly.
- when the car is parked the ice remains in the insulated box for several hours. When the driver gets in, it has cooling by turning icebox ventilator on.
One could imagine the same, ice storing for normal, compressive aircon, but it has an important drawback: the higher the temperature difference it makes, the more engine power it needs. Cooling air only 10-20 degrees is significantly more fuel-efficient than freezing water.

       Absorptive refrigeration, might not have the same drawback - it cools down to freezing temperature by default, with no extra effort.
blimpyway, Jun 18 2006

       You might be able to control the temp of the cold ball by throttling the flow of refrigerant to it - just put in a valve.
neelandan, Jun 19 2006

       Yes Neelandan but:
1. A great advantage of the absorption cooling system is that can be completely sealed and it has no moving parts. Coolant is not leaking and the refrigerator works, without interruption, breaking nor maintenance even for decades. A valve would be a weak point.
2. Temperature in the car still can be regulated by ventilating more or less air through the ice reservoir box.
blimpyway, Jun 19 2006


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