Manufacturers aren't utilizing all options for efficiency IMO

[93JC]

Yours as in yours Mazda3 doesn't?

Sorry, the old Dodge doesn't. I have no idea what the Mazda does. I think a lot of new cars do it automatically simply because they're tailored to markets where it's used as a defogger. Here it's pretty much useless, because the air is very dry to begin with.

[MX793]

Piezos also work in reverse - deform them and they produce a current - this is how click-style push-button ignitors work on grills and camping stoves.

Piezoelectrics are also the magic behind quartz watch movements.

[Laconian]

Piezoelectrics are also the magic behind quartz watch movements.

Don't forget ear-splitting buzzers. My parents rued the day I discovered how to use the piezo buzzer on my 60-In-One.

[the Teuton]

I just learned about this stuff at SAE, and here you guys are ahead of the game!

[sportyaccordy]

Market studies I'm sure state that the 1-2 mpg savings isn't worth the moderate cost ($2,000+ I'd bet) for such motor systems.

The efficiency gains of running A/C compressor off of an electric motor will be minuscule as the normal course of operation the typical A/C compressor has a clutch that will cut out when need be.

Some efficiency gains can be found in oil pumps, PS pumps, water pumps, etc., but only because those systems either must run all the time, or do not have a clutch like an A/C compressor.

No way it would cost that much. You have a compressor w/o a clutch, and you'd add a motor and *maybe* a DC-AC rectifier. I use A/C 6 months out of a year... and it definitely impacts my gas mileage. The premium for the added efficiency would be worth the extra $500 or so

[BimmerM3]

Depends on the car. Some automatically kick on the A/C compressor, some don't. Mine doesn't. And obviously the cars out there without A/C still have defrost...

My Accord does, but you can just hit the AC button to turn it off again, and keep blowing through the defrost vents.

[BimmerM3]

A bigger, more powerful alternator that is still belt driven and will now take more mechanical power to be turned.  And unlike the AC compressor, that saps the bulk of the mechanical power only when operating, the beefier alternator will be sapping more power 100% of the time the engine is running regardless of whether the AC is on or not.

Yeah, that too.

[giant_mtb]

I worked on microelectromechanical systems (MEMS - google-image that shit) at school this past year that used piezoelectric materials to move.  It was neat.

[GoCougs]

I worked on microelectromechanical systems (MEMS - google-image that shit) at school this past year that used piezoelectric materials to move.  It was neat.

They're also used in industry, too, for small, precision positioning products like this.

[giant_mtb]

They're also used in industry, too, for small, precision positioning products like this.

And what does that thing do, anyways?

[the Teuton]

I knew we had an intelligent group of people here, but who knew you'd all be up on Piezo electronics?

[GoCougs]

No way it would cost that much. You have a compressor w/o a clutch, and you'd add a motor and *maybe* a DC-AC rectifier. I use A/C 6 months out of a year... and it definitely impacts my gas mileage. The premium for the added efficiency would be worth the extra $500 or so

Then why don't automakers do it?

Your mileage I bet isn't impacted more than what you could reliably measure - 5 hp drag simply isn't going to be that much of a MPG killer.

Byteme's hunch is correct IMO - a 3-6 hp DC motor rated for continuous use would be expensive and relatively large - much more so than a starter motor for example.

[GoCougs]

And what does that thing do, anyways?

Those are small x-y and rotary positioners that use programming to position to a predefined coordinate position. I've used them in the past in labs and clean rooms for ultra-precise positioning of things such as lasers and sensors.

[MX793]

And what does that thing do, anyways?

It's an actuator. You'd use something like that for precision component positioning in automated assembly lines.

[giant_mtb]

Mmmm.  Neat-o.

[sportyaccordy]

Then why don't automakers do it?

Your mileage I bet isn't impacted more than what you could reliably measure - 5 hp drag simply isn't going to be that much of a MPG killer.

Byteme's hunch is correct IMO - a 3-6 hp DC motor rated for continuous use would be expensive and relatively large - much more so than a starter motor for example.

5hp is a huge drag in stop/go traffic, and the compressor is hardly ever working at its most efficient speed.

And an A/C to cool a 350 sq ft room barely consumes 1hp, compressor + evap fan included. I don't see where this 3-6 HP figure is coming from. If anything, because the compressor is belt driven it may very well use all that power for 1-2HP of effective cooling.

Obviously there are reasons why manfuacturers aren't doing it... prob retooling + redesigning costs... but I still think it's viable. I wish I was still in school, I'd be able to prove this in the lab. Would have made a good senior project.

[GoCougs]

5hp is a huge drag in stop/go traffic, and the compressor is hardly ever working at its most efficient speed.

And an A/C to cool a 350 sq ft room barely consumes 1hp, compressor + evap fan included. I don't see where this 3-6 HP figure is coming from. If anything, because the compressor is belt driven it may very well use all that power for 1-2HP of effective cooling.

Obviously there are reasons why manfuacturers aren't doing it... prob retooling + redesigning costs... but I still think it's viable. I wish I was still in school, I'd be able to prove this in the lab. Would have made a good senior project.

If your A/C is affecting your power and/or MPG that drastically to me it sounds like there is something wrong. Further, compressor load won't be the same all the time; it'll vary on the amount of cooling.

Belt drive trains are very efficient - well above 90%. I imagine the valving and the like in the system to get it to work well over a wide RPM range does hurt efficiency however.

You don't need a lab to prove out the economics of it, however. Further, your average automaker has scores to hundreds of engineers on staff that do nothing other than tinkering with new ways to improve product.

[Raza]

They're also used in industry, too, for small, precision positioning products like this.

Is it the same thing that creates the spark on a butane lighter?

[Byteme]

No way it would cost that much. You have a compressor w/o a clutch, and you'd add a motor and *maybe* a DC-AC rectifier. I use A/C 6 months out of a year... and it definitely impacts my gas mileage. The premium for the added efficiency would be worth the extra $500 or so

In engineering there is no free lunch.  The electricity to power that electric motor has to come from somewhere and it ciomes from the engine.   For argument's sake lets say the AC compressor take 5 HP.  Assuming no effeciency loses that equates to about 3,725 watts.  Again with no efficnency loses you are looking at 310 amps.  Automobile alternators are typically 50-62% efficient so you would actually need a 500-620 amp alternator. That's one big ass alternator and a 500 amp alternator takes about 8 hp to generate those 500 watts.  So you have a power deficit of 3 HP. And we still haven't address the extra weight and cost penalty.

[VTEC_Inside]

5hp is a huge drag in stop/go traffic, and the compressor is hardly ever working at its most efficient speed.

And an A/C to cool a 350 sq ft room barely consumes 1hp, compressor + evap fan included. I don't see where this 3-6 HP figure is coming from. If anything, because the compressor is belt driven it may very well use all that power for 1-2HP of effective cooling.

Obviously there are reasons why manfuacturers aren't doing it... prob retooling + redesigning costs... but I still think it's viable. I wish I was still in school, I'd be able to prove this in the lab. Would have made a good senior project.

Here is the proof that you are looking for, on an RSX-S anyway...



As you can see from that, its actually greater than 3-6hp. That's with a fair sized pulley advantage (ie the A/C in the RSX does sweet bugger all at idle)

[MrH]

I knew we had an intelligent group of people here, but who knew you'd all be up on Piezo electronics?

Enginerds learn how things work.  That's what we do.

The coolest, newest use of piezo electrics?  Piezo electric haptic feedback on the new Blackberry Storm 2.  There are 4 under the touch screen at the corners, and they can vary how much they vibrate.  Combine those all together, and you get a small vibration right where you press, and the phone makes a "click" noise.  It's supposed to be ridiculous how it feels like you just pressed a button.

[Eye of the Tiger]

Enginerds learn how things work.  That's what we do.

The coolest, newest use of piezo electrics?  Piezo electric haptic feedback on the new Blackberry Storm 2.  There are 4 under the touch screen at the corners, and they can vary how much they vibrate.  Combine those all together, and you get a small vibration right where you press, and the phone makes a "click" noise.  It's supposed to be ridiculous how it feels like you just pressed a button.

WHY DUZINT MY IFONE DO THAT

[2o6]

Enginerds learn how things work.  That's what we do.

The coolest, newest use of piezo electrics?  Piezo electric haptic feedback on the new Blackberry Storm 2.  There are 4 under the touch screen at the corners, and they can vary how much they vibrate.  Combine those all together, and you get a small vibration right where you press, and the phone makes a "click" noise.  It's supposed to be ridiculous how it feels like you just pressed a button.

WOW. That's how that works?

I thought the screen actually depressed like a button.

[MrH]

WOW. That's how that works?

I thought the screen actually depressed like a button.

The old one did.  The new one doesn't.

[GoCougs]

Is it the same thing that creates the spark on a butane lighter?

Actually, I'm not sure. I wouldn't down that at least some do - the candle lighters I'm pretty sure have piezo ignitors.

[GoCougs]

I knew we had an intelligent group of people here, but who knew you'd all be up on Piezo electronics?

Now check this out.

The piezo electric in this precision positioner actually acts as a motor, and is controlled (via current and voltage) with electronics typically used to control electric rotary (or linear) motors.