Really Cool Invention Brings Teens Awards (Amazing Kids-Invented What GM Couldn't)

The Salt Lake Tribune ^ | 07/06/2005 | Jessica Ravitz

[Dinsdale]

Modern AC comperessors have electronic clutches on the the drive pully.

When they are disengaged only the pully spins.

I on the the other hand know how to build an AC for a car that runs without drive power.

Just put another heat engine between the cooling system and ambiant. Use the power output from this to turn a regular AC compressor. Viola free AC.

Of course every auto maker know how to do this also. The costs for the heat engine are prohibitive. For those of you without an engineering backgroud. Heat engine == device using a working fluid used to eather make energy from a heat differential or pump heat using energy. Basically you build a 'steam' engine to run off the radiator heat.

[Nov3]

It takes energy to move that wire through the magnetic field. The greater load on the wire the greater the force required. If an alternator is putting out say 20 amps at 14.5 Volts, it is going to require at least (20*14.5)/746 = .39 Horsepower to drive it. More with losses. If it puts out 40 amps it will need .78 horsepower input. It is unavoidable.

[Dinsdale]

480 AC costs more fuel then the regular kind of AC.

Increased drag.

[AxelPaulsenJr]

Does a convertible with the top down have the same or greater drag than a car with all four windows down?

[absolootezer0]

i know. but it still a couple of pounds of weight that can be lost, and a few less inches on the belt, which will turn the other pulleys faster.

[Old Professer]

All of physics relies on size except for nuclear devices.

There is no way that a practical A/C system can be made to cool the interior of a full size car using any sort of Peltier chip without the chip surface area approximating the dimensions of the area to be cooled that I can imagine.

I will need more information and a demonstrable device to be convinced.

[Charles Martel]

I'm suprised that after nearly 200 posts someone has not mentioned the 480 system that I have on my car. Four windows down and 80 miles an hour.

The "240" system works almost as well - and you can still hear the radio!

[Dinsdale]

I'd have to guess. But it would depend on the details of the car design (assuming you mean to compare apples to apples). Do you get better milage with the top up or down?

At highway speeds it is usually more efficent to run the AC vs opening the windows.

But top down is more fun/gallon.

[Final Authority]

I don't know if anyone replied but a Pelletier cooler is also known as a TE cooler as in thermoelectric cooler. It works on the principle of the thermoelectric effect of dissimilar materials like a thermocouple wherein a thermocouple (TC) generates a voltage proportional to the temperature gradient between the junction of the dissimilar materials and where the voltage is detected. A TE cooler operates by powering dissimilar materials with a DC current and the materials will either absorb heat (get cool) or radiate heat (from the side that is cooler). Changing the polarity of the current reverses the cooling effect.

The best non-semiconductor materials were and are bismuth and antimony for the thermoelectric materials. TE coolers rely on an amorphous semiconductor junction.

It is unlikely that such an invention would be of any benefit as a typical auto AC unit has at least a 12,000 BTU capacity which would equal about 3.5 kW or about 5 HP. Since a typical 2 inch TE cooler component uses about 35 Watts one would need about 100 pieces and figure out a way to cool the hot side and deliver cabin air to the cool sides to circulate. It ain't gonna happen.

[Dinsdale]

Other pulleys are the same speed unless you change the pulley sizes.

But I get your point about wheeling. For the the weight of my AC I could bring along another case of beer.

[Old Professer]

Too sensitive to motion.

[JAKraig]

You are so wrong!

[Old Professer]

185/746=~1/4 H.P.

[Old Professer]

The Pelteir Effect is the opposite of the Seebeck Effect.

[Old Professer]

I imagine their design uses the engine heat as a "bath;" as the electrical current flows through the chip along the one conductor that is in the bath the opposite side of the chip surface (a dissimilar metal) becomes cool proportionately to the heat of the bath and this cool surface would need to be in the airflow of the fan(s) directing the cooled air through the cabin.

My big problem has to do with the surface area of the chip(s) vs the cubic volume of space being chilled.

Condensate control would also be a factor, but perhaps they are using bonded finned-sinks within a housing.

It would be nice to see an engineering diagram.

[Nov3]

I'm suprised that after nearly 200 posts someone has not mentioned the 480 system that I have on my car. Four windows down and 80 miles an hour. The "240" system works almost as well - and you can still hear the radio!

I still remember my dad cussing the engineer who took the vent windows out of his 71 Dodge Demon. His air conditioner failed. We were driving to the lake on the expressway with all the windows down. He was muttering to himself ,"75 mph with all the windows down and you could light a MFing candle and put it on the daskboard." The backseat was windy as hell but the fronts seat was devoid of wind.

[Old Professer]

The electrical load is linear to the horsepower demand; 746 watts equals one horsepower minus frictional and resistive losses.

[Nov3]

You are right on. The other thing is an airconditioner for a car has to large enough to cool a good size house. A car is a steel and glass uninsulated greenhouse that has to be cooled from 130+ inside temps to 70 in a reasonable time.

[Old Professer]

Thermocouple.

[Final Authority]

I don't know if anyone tried to explain why an alternator becomes harder to turn with an increased electrical load but I will try.

Think of a load on the alternator as a demand for current, forget voltage. Current is the same when measured from any place in a circuit so the current going through the main fuse box is the same as the current in the stator of the alternator (if the stator is the output winding). As more current is demanded by turning on lights for example more current must surge through the alternator and that current comes from the induction caused by the rotor, which is energized by the battery/electrical system and spun by the engine. If the engine did not spin there would be no induction and no current but in an alternator there is a greater reluctance for the rotor to spin as the current increases. A simple example test would be to take a model or toy DC motor and hold in your hand and spin it, then connect the electrical leads together and give it another spin. You will find it harder to spin it when connected. Now, take a voltmeter and attach it to the leads and give it a spin. You will get a voltage generated. Now spin it faster and you will see a higher voltage. Since the circuit has a resistance a higher current (faster spinning) will cause more voltage to be generated as the equation for this is V (or E)=I*R or voltage is current times resistance. So in a car, increasing load is reducing resistance while the voltage regulator is maintaining voltage the current must go up. The load on the alternator goes up, the reluctance to turning goes up hence the power to generate the electrical power must go up.