Patent application #20120222429 claims:

  1. A vehicle air conditioner for a passenger compartment of a vehicle, comprising:

    • a power source for driving the vehicle; a radiator provided outside the passenger compartment;
    • a heat medium passage through which heat medium is circulated between the power source and the radiator;
    • a first pettier module having a first pettier device and a first heat exchanger, the first pettier device having a first surface and a second surface, one of the first surface and the second surface serving to release heat, the other of the first surface and the second surface serving to absorb heat, the first heat exchanger being thermally coupled to the first surface;
    • and a second pettier module having a second pettier device and a second heat exchanger, the second pettier device having a first surface and a second surface, one of the first surface and the second surface serving to release heat, the other of the first surface and the second surface serving to absorb heat, the second heat exchanger being thermally coupled to the first surface, wherein the heat medium passage is thermally coupled to the second surface of the first pettier device and the second surface of the second pettier device.

How is this fundamentally different from the way other AC systems in cars are made? Are there prior examples of something similar?

  • 2
    Ouch! OCR or typist fail: this should be a Peltier module. Commented Sep 18, 2012 at 21:22
  • Maybe it would be a reason to reject the patent :-) Commented Sep 18, 2012 at 22:29
  • Probably not, I think such corrections would be admissible even after acceptance. I've seen worse translations. Commented Sep 18, 2012 at 22:40
  • 1
    If the application does include the mis-spelling I see it as grounds for dismissal because it fundamentally misleads the prior art check. Imagine you didn't know about peltier plates... How could you check the novelty of this patent?
    – Ben D
    Commented Sep 20, 2012 at 16:25

5 Answers 5


I don't know the technical area, so I cannot speak to whether claim 1 identifies anything "fundamentally different" for pre-existing AC systems. It is not necessary that the patent disclose a fundamental difference with prior art - the novelty may be small, even very small.

Furthermore, claim 1 is not the be-all and end-all of the patent. This application has three dependent claims, each of which is a separate invention.

I have given other similar answers to similar questions. Taken together, they give a more complete overall answer to this question.

Prior art for using a camera in self-driving cars

Microsoft have submitted a patent for a whack to silence a phone ringer. How similar does prior art have to be?

Can the non-obviousness of an invention be challenged if the difference to prior art is only the mathematical-statistical approach?


Prior art for wear-focusing of non-volatile memories.

  • 3
    Please don't spam every prior art question with this. While the point is valid, you have to start somewhere. It's perfectly normal to start by looking for prior art for claim 1: as long as none is found, the patent is presumably valid. If prior art is found that covers claim 1 but (say) not claim 2, then a new question might ask for prior art for claim 2. This answer should really have been posted as a comment — but posting a comment like this on every prior art question on the site will get old fast. Commented Sep 20, 2012 at 16:00

I assume that the term submission should have been "Peltier" instead. Most automotive systems today don't use Peltier cooling. Still, to substitute a conventional compressor with a Peltier system seems rather "obvious" to someone of "ordinary skill in the art."

  • Yeah, it's a bit like deciding to use titanium bolts instead of iron ones to save weight, or maybe an electric engine instead of a gas one: it does the same job, just in a different way.
    – pjz
    Commented Sep 20, 2012 at 15:25
  • 1
    @pjz - I disagree. While this application doesn't seem that revolutionary considering the number of systems using peltier cooling, it is a fundamentally different technology than compressor cooling... it's like using a gas stove vs an electric stove... they get the same job done but by very different mechanisms
    – Ben D
    Commented Sep 20, 2012 at 16:22

Typical air conditioning systems use an evaporative cooling system with a mechanical compressor acting as the heat pump moving heat away from the passenger compartment to the exterior of the vehicle.

This patent appears to replace the evaporative cooling heat pump with a peltier module heat pump. A peltier device is a semiconductor heat pump frequently used for small refrigerators and drink coolers. It is notable for its inefficiency (energy in vs heat pumping ability) and for its low cooling capacity(requires many modules to provide cooling for spaces larger than a small cooler). Advantages include small size, no moving parts, and electrically powered.

It would surprise me if a patent didn't already exist for this. I know vehicle manufacturers have been looking at this for many years, especially in connection with electric vehicles. They find, however, that to meet cooling capacity, efficiency, and low cost requirements they are better off with a motor running a typical compressor in an evaporative cooling system.

Doing a search for vehicle patents using peltier devices should bring up patents that precede this one which are substantially similar.


As far as I can tell in this cryptically worded application, the request is for a patent which uses a peltier thermocouple to salvage heat energy from the car engine and then relays that electricity to a second thermocouple where the process is reversed and the cool side of the second thermocouple is used for AC.

Both these steps have occurred to car enthusiasts for decades (5 seconds on Google yielded this for using a Peltier plate engine heat to generate electricity and here and this for building a Peltier air conditioner (2003)). Wikipedia even has a page just for vehicle thermocouple generators, which have been used as far back as 1963 (Porche) as well as Nissan test vehicles. And hop on utube and you'll see lots of home-made versions of both steps. The main reason why there is less interest in the air conditioning abilities of peltier plates is that they are terribly inefficient.

I'm no expert, but I'm not sure that coupling these two processes together (generating electricity and then using the electricity) should pass the "must be useful" patent test. Both ideas have been done plenty of times and there is no value added by patenting them together. It would be like the following: Imagine that both pencils and paper have been invented but are so expensive that they are not in in widespread use, and I come along and say "I know that I can't patent paper, because someone already made that, and I know and I can't patent pencils, because someone already made that, but I'm going to patent 'the process of using a pencil to write on paper'"... and then hope that the price of pencils and paper comes down. Obviously pencils are used to write, and obviously paper is used to write on, and just because people aren't doing it today due to cost/efficiency reasons doesn't mean it's not perfectly obvious.

Also, to answer your question "How is this fundamentally different from the way other AC systems in cars are made?" - AC in cars today use a compressor (generally running directly off the rotational motion of the engine, but also possibly off of the current generated by the generator) to compress a large volume of gas into a small space. Applying the combined gas law, this means that the compressed gas is much hotter that the uncompressed gas (same amount of energy in a smaller space). This hot compressed gas is then run over a radiator (generally lots of plates of thin metal) which vent the heat into the outside air. The compressed gas is then decompressed (let into a wider pipe) but now it has much less heat energy that when it was first compressed, so it's comparatively cold. The Peltier plates, by contrast, cool via the Thermoelectric effect which causes a temperature differential to occur between two substances (generally metals) if a current was run betweeen them (one plate will heat up and the other will cool down)


A Peltier device is a type of heat pump. Traditionally, automobiles have used heat exchangers, which are a more passive way to move heat from one place to another (from inside the vehicle to outside), but in situations where the driver/operator wishes to cool the interior air but the outside air is extremely warm, the use of an active heat pump rather than a passive heat exchanger to improve the effectiveness of the system strikes me as an obvious step forward.

The specific usage of a Peltier cooler rather than any other type of powered heat pump strikes me as irrelevant; if there are examples of prior art in which any type of heat pump is used, I think those would apply here as well.

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