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Waste Heat Recycling A/C For Cars

Use exhaust heat to power an ammonia cycle air conditioner.
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I remember my grandmother telling me about a fridge she used to have that burned kerosene to cool down. I’ve researched the topic, and now sort of understand how it works, and it still blows me away.

For anyone out there with a deep understanding of the topic of ammonia / hydrogen / water refrigeration, perhaps you could shoot down my idea.

Would it be possible to use the exhaust heat from an internal combustion engine to provide the energy for an air conditioner based on the same principal as granny’s fridge? If so, we could have plentiful air conditioning at no additional energy cost.

TIB, Sep 07 2003

experiment http://www.metrans....ort/99-19_Final.htm
<URL fixed by admin> "A sorption compression system can utilize the exhaust heat or the heat absorbed by the cooling water." [Fussass, Oct 17 2004]

Already posted this idea. Szil_e1rd_20Air_20Conditioning
Exactly as described. [WcW, Feb 17 2011]

[link]






       This one is over my head, from a practical view. It seems to me that, in theory, a heat exchanger placed around, say, the lower exhaust manifolds should be able to harvest otherwise wasted energy. How that gets used to drive an AC unit, I don't know. Steam turbine?
bristolz, Sep 07 2003
  

       This is a fabulous idea - the ammonia crystals left over from when then engine last stopped could be used for a quick a/c startup. No more hot air blowing out of the vents on startup.   

       The only problems are:   

       (1) the minimum economic size of these systems is quite large   

       (2) you might need supplemental firing to boost the cooling power at certain times   

       (3) as [UB] said, other than the heat source, there are few synergies with the existing car systems   

       Any proposed solution [TIB]?
FloridaManatee, Sep 07 2003
  

       [UnaBubba] Yeah, sorry about the free energy reference. I should have said something more along the lines of energy recovery like you suggest. Amazing idea – the supercharger!! When you’re not using the AC to it’s full capacity, use the remaining heat extracting potential to cool the incoming air. Maybe this idea could be applied to the power station problem too! Use the power station exhaust heat to cool incoming air?   

       [FloridaManatee] I wonder, with today’s technology, would it be possible to engineer one of these units to be much smaller and more efficient than it’s predecessors? Do you know of any company that has a modern version of this old idea? If heat is needed when the engine is still cold, electricity could be used to heat the refrigerant solution until the engine warms up. I agree, there are few synergies with existing cars systems. I chose exhaust heat because of the temperature differential, but perhaps the engine coolant would suffice. In that case, the AC could be integrated with the radiator, simplifying things a little.
TIB, Sep 07 2003
  

       Small propane powered ones are used in campers, so they can be miniaturized. Big ones have been used with geothermal heat the same temperature as radiator coolant. There is also a lithium bromide and water cycle that would fix any toxicity issue. After the sad fate of all the other waste heat ideas this one might stand.
Here is a link to some people trying to do it with carbon adsorption. I think they proved that they could make it too big and expensive and ran out of funds.
Fussass, Sep 08 2003
  

       Fussass, that link ain't never gonna work like that.
waugsqueke, Sep 08 2003
  

       Link fixed and it's a good read. The "Introduction" and "Principles of Adsorption" sections explain a lot that I didn't know about.
bristolz, Sep 08 2003
  

       I like. A car's compressor is an expensive, leaky, noisy, fuel-hogging piece of crap that has to live in a terrible environment and be happy about it, no matter how well it's designed. Most of your coolant that permeates out of the system goes through the dynamic compressor seal, and so a system that abandons the whole thing would be a great advantage in terms of extending the useful life of the car. However, I doubt very highly that there will be enough capacity to cool the entire passenger compartment effectively. Nice as a hybrid system though.
RayfordSteele, Sep 08 2003
  

       Great, and whenever you really need the A/C, you have a lot of heat hitting the car, so why not trap it as well and add it to the heat from the exhaust?
oxen crossing, Sep 08 2003
  

       [TIB, Sep7, 2003] i am working in captive power plant & in advanced stage of designing comprehensive waste heat recovery systems to run CHP (Combined Heat & Power) systems. it would mean Kalina cycle/ ORC based power generator coupled with a_sorption chillers. there would be utilization of all possible heat sources, to name just one - heat recovery from large capacity step down transformer cooling oil. as far as application to car or any automobile is concerned, just think about the significant increase in weight to be carried (the systems are bulky) which would increase fuel consumption.
vedarshi, May 25 2004
  

       Here's why it won't work: There has to be a minimum temperature difference between the condenser and the absorber or the system will stall. I had one of these fridges in my van, running on LPG, and if I parked in the sun, the fridge would quit after an hour or so. Nothing would coax it back into operation except allowing the whole thing to cool down for a couple of hours. Even without this problem, you have to wait an hour or so after starting the system before you get any significant cooling from it. By then, you're probably already where you were going.
(o)-(o), Aug 10 2004
  

       OK, so it won't really be practical for car use, but plumbing exhaust heat through the "generator" portion of the sorbtion (sp) cycle cooling system of an RV might be useful to keep the 'fridge cold while on the road. (+)
Freefall, Aug 10 2004
  

       Idea was already posted by me, only better. Take down your offensive duplicate.
WcW, Feb 17 2011
  

       [WcW] I do believe your idea was posted second...and should therefore be "MFD"d
senatorjam, Feb 17 2011
  

       [WcW] You do realise this idea was posted 5 years before yours, right? And are being ironic, right?   

       This has been baked on a larger scale in the form of combined heat and cooling and power stations.   

       These devices might not work so well in the somewhat jolty conditions of a moving car.   

       Also, off topic but mentioned by TIB above, I didn't realise it was useful to cool the inlet air in power stations. In fact, systems have been looked at where the incoming fuel and air are heated by counter-current exchange with the exhaust, to increase the combustion temperature and thereby increase the thermodynamic efficiency, especially when low-grade fuels are used. (Source: a book called (I think) Biological Paths to Energy Self Reliance).
spidermother, Feb 17 2011
  

       //Idea was already posted by me, only better. Take down your offensive duplicate.//   

       At last proof that time travel is possible. TIB must have built/borrowed one for the sole purpose of posting the idea first...I have the same happen to me all the time, so maybe they are just sharing the same time machine?
not_morrison_rm, Feb 23 2011
  

       ouch. I still think that my idea is better. I'll take it down of the author wants.
WcW, Feb 23 2011
  
      
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