Some of the newer hybrid cars have Electric AC on them. could it be possible to retro a Fiero to use one of these compressors? it could fit in front of the car removing some of the complexity.
Has anyone any experience with those new fangled electric AC compressors for the new hybrids?
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05:33 PM
PFF
System Bot
3.8 SC Member
Posts: 577 From: On the Great Lakes-Ohio Registered: Dec 2003
What does it look like if you pulled the clutch off a normal AC compressor? I would assume you are left with a simple shat that you could directly connect to an electric motor. If anywhere, I'd put it in front since its going to be a rather large system.
Also keep in mind that you will definitely need a bigger alternator.
the toyota prius from 2005 on have electric AC compressors. GM also has a dual-mode air conditioning compressor. As part of the ParadiGM system, the compressor is mounted on and driven by the transaxle but also can run electrically.
The GM one is interesting as it runs from the belt or electric and would probably be cheaper than the toyota parts.
also the 2004 and newer Honda hybrids have an electric AC compressor.
[This message has been edited by timgray (edited 08-13-2007).]
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06:12 PM
Riceburner98 Member
Posts: 2179 From: Natick, Ma, USA Registered: Apr 2002
one of the questions on the auction brought up a good point, i think most of these hybrids dont run 12volt systems for anything other than interior stuff. i would think that compressor wont work on a 12 volt system.
[This message has been edited by Jrgicehc (edited 08-13-2007).]
Those wires look pretty thick. I wonder what the rated voltage/amps are for it. If it was a simple 'wire it up' installation, it would be great for all the guys with engine swaps. Just mount the compressor up front and not need those long lines going to the engine compartment. Someone please do this and let us cheaply copy your hard work
Wow, cool article! Wouldn't have guessed it ran that much AC voltage! "Special oil is needed to help insulate against the voltage"... Damn... I guess even getting it installed in a Fiero would also introduce the risk of electrifying anything it touches if not done 100% correct.
The problem is that the energy to run that compressor has to come from somewhere. On the hybrids, it's electric because the gas motor shuts down when the car stops and you don't want the AC to shut off.
In the Fiero, you would have to add an alternator the size of the compressor and a lot of batteries to store that energy needed to run the electric AC. In the end it would be a waste of energy, because every one of those power conversions have losses. There would be no advantage to a belt driven AC.
The problem is that the energy to run that compressor has to come from somewhere. On the hybrids, it's electric because the gas motor shuts down when the car stops and you don't want the AC to shut off.
In the Fiero, you would have to add an alternator the size of the compressor and a lot of batteries to store that energy needed to run the electric AC. In the end it would be a waste of energy, because every one of those power conversions have losses. There would be no advantage to a belt driven AC.
Unless you need to replace your compressor with a supercharger and really wanted to keep your AC.
The problem is that the energy to run that compressor has to come from somewhere. On the hybrids, it's electric because the gas motor shuts down when the car stops and you don't want the AC to shut off.
In the Fiero, you would have to add an alternator the size of the compressor and a lot of batteries to store that energy needed to run the electric AC. In the end it would be a waste of energy, because every one of those power conversions have losses. There would be no advantage to a belt driven AC.
I have to disagree. Everyone can benefit from a more efficient compressor.
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09:29 PM
frankenfiero1 Member
Posts: 441 From: maryville TN USA Registered: Oct 2006
How about this, a small R-22 compressor out of a dorm size fridge, coupled to our existing system using an inverter. A 1500W surge, 700W should handle this no problem. This only equals about a 12A drawDC (roughly calculated). kinda seems feasable.
the R22 systems are not designed to handle the extreme temperature changes that take place in a car. and i dont know how R22 would react in that large of a system. plus R22 systems dont use an accumulator or filter dryers (some might use them i dont know). and..... i dont know if those compressors could handle the vibration.
Edit.... i also think R22 opperates at higher pressures than automotive refrigerants. this does not matter in a beer fridge because they do not use servicable lines, everthing is brazed/welded together. but in a system that uses o-rings and high pressure blow-off valves this could pose a problem.
[This message has been edited by Jrgicehc (edited 08-14-2007).]
Isn't a typical auto AC system something like 50,000 BTU to keep up with the heat from the sun / etc..? That would take a pretty serious sized "fridge" compressor... We usually have like .5-.75" lines in the car, the home stuff is running .25" lines or so..
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10:59 PM
Aug 15th, 2007
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
When it comes to electricity everyone seems to think it magically appears out of this air. Even Theogre doesn't seem to get it when I try to explain it to him.
To run an electric device in a car requires energy. That energy comes from the mechanical rotation of the engine, which comes from the gasoline. If you want to turn an electric compressor it's going to take MORE energy than if you just bolted it up to the flywheel and be less efficient.
Why you ask? Because no system on planet Earth is 100% efficient, so every time energy is converted from one form to another some is lost, usually in the form of heat. So I'm going to need to generate more energy than what is needed to run that AC compressor to account for the losses in the convertion from Mechanical to electrical, and the conversion from DC to AC, and the upconversion in voltage from 12 volts to 201.6 volts
So unless there is some compelling reason to do that, (like having A/C running when the gas motor is stopped) you are not going to want that system. It certainly is NOT more efficient than running the compressor off the flywheel.
Not convinced? Let's crunch some numbers...
Frankenfiero1's numbers ignore a simple rule, If you increase the voltage by a factor of 10 (from 12V to 120V) the current is reduced by a factor of 10.
To make up for that, the DC current has to be increased by a factor of 10. In other words, to power a 700W inverter at 120V is 5.8 amps AC this is 58 amps at 12V DC, and that's at 100% efficiency. In the real world it might only be 90% efficient, so you need about 65 amps going into that inverter (steady state) or about 140 amps (peak)
Okay so let's see if you can use the "excess" energy generater by your alternator to run this compressor...
What does a standard Fiero alternator put out? 80 amps? You just barely have enough power at steady state to run that inverter, let alone the peak loads, oh and all the other loads of the car. If you upgraded to a 200 amp alternator you MIGHT be able to do it, but then again it would be more effiicient to run that compressor right off the flywheel...Q.E.D.
also, think of it this way.. even if we did put a 200 amp alternator on our car, you are taking mechanical energy, converting it into electrical via the alternator, then converting that electrical energy back into mechanical energy via the compressor motor. at every conversion you will have energy loss. so if we dont have any real reason to convert to electrical AC like the hybrids do, why bother?
also if you think your engine bogs alot when your compressor clutch engages, wait until you try and draw 200amps off an alternator, it will bog more.
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01:33 PM
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
How about this, a small R-22 compressor out of a dorm size fridge, coupled to our existing system using an inverter. A 1500W surge, 700W should handle this no problem. This only equals about a 12A drawDC (roughly calculated). kinda seems feasable.
Except the interior of a Fiero is much larger than the interior of a dorm size fridge.
Car AC systems are much higher capacity than most people realize because of the lack of insulation. Your house doesn't get up to 140° if you turn the AC off for a few hours on a hot day, but your car will. A car's AC system not only has to cool the volume of air in the car, but has to make up for the continuous flow of radiant heat into the car through the windows.
Which is why I point out that it is most likely much more efficient than our 20 year old compressors. Another advantage is your belt or clutch wont ever wear out.
If those two reasons are compelling enough to convert over to AC AC, then you have some justification. This isnt like putting stickers on a car and expecting it to go faster.
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02:08 PM
Dennis LaGrua Member
Posts: 15722 From: Hillsborough, NJ U.S.A. Registered: May 2000
Open up the alternator and tap off of directly from the windings into an AC voltage regulator.
Quite a few years back, I powered 120 VAC/DC electric drills and saws from the old style alternators that used external regulators so this approach might work, assuming that the amperage requirement of the compressor is within the output amps of the alternator. However, I don't know if you can get as high 201 VDC from an alternator. I really don't see any advantage of using an electric compressor though as they are probably power hogs.
------------------ 87GT 3.4 Turbo- 0-60 5.2 seconds 2006 3800SC Series III swap in progress Engine Controls, PCM goodies, re-programming & odd electronics stuff " I'M ON THE LOOSE WITHOUT THE JUICE "
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04:57 PM
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
also if you think your engine bogs alot when your compressor clutch engages, wait until you try and draw 200amps off an alternator, it will bog more.
Exactly. I don't know why people think electricity is free energy. In most cases the conversions make it less efficient. The only reason Hybrids are able to eek out some efficiency gains is that they recover energy that is normally wasted, (with regnerative brakes), they shut down the gas motor when it's not needed, (at idle) and they use the electric motor for acceleration (where it's more efficient to do so).
There is no magic that makes electricity a more efficient source of energy, especially when the source of electricity is the fuel to run the gas engine.
Yikes! I did not know they were insane high voltage and power. That rules that out. I was hoping they were using some of the newer higher efficiency systems like in window air conditioners. I can get a 15,000btu window air conditioner that draws 5 amps from 110V ac outlet It's at a point that it would be cheaper for me to shut down the whole house AC and buy and install 5 of these little ones as 15 amps is far less than the 40 amps my huge unit in back draws.
The engine isnt going to bog down any more when you throw on the electric AC compressor than it would when the clutch engages assuming the same BTUs.
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There is no magic that makes electricity a more efficient source of energy, especially when the source of electricity is the fuel to run the gas engine.
By that logic we should be doing our work by tapping off a flywheel powered by a driveshaft from the electric company.
As an electrical engineer, I guarantee you that converting to electricity to carry energy over long distances is always more efficient.
[This message has been edited by AP2k (edited 08-15-2007).]
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10:24 PM
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
By that logic we should be doing our work by tapping off a flywheel powered by a driveshaft from the electric company.
As an electrical engineer, I guarantee you that converting to electricity to carry energy over long distances is always more efficient.
C'mon now, let's be reasonable... There is a big difference between a belt driven automotive accessory and transmitting power over great distance.
But what are the losses over those high tension wires? How much losses are in the turbines and generators? I'm not an electrical engineer, but I'm guessing that less than half the fuel burned at the power plant ends up being used in people homes and businesses.
The rest is lost forever into the ether. I guarantee that it would be more efficient if we burned the coal or oil in our own homes versus the power plant.
If it weren't for Tesla we would be pushing DC though those wires and everyone would have to live a few miles from the power plant because the losses would be so high.
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11:35 PM
Aug 16th, 2007
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
Okay the transmission losses are relatively small (~ 7.2%), but that is only part of the equation.
The power plant itself is only about 45% efficient, and the conversion losses at each end are significant but economically acceptable.
The fact that it costs the power plant about $0.005 per kilowatt hour to make the electricity and I pay something on the order of $0.127 the losses are bearable when you have 2500% markup.
In a car I don't think you would be happy if only 1% of the gasoline you burned was turned into electricity and the rest wasted.
The engine isnt going to bog down any more when you throw on the electric AC compressor than it would when the clutch engages assuming the same BTUs.
I disagree, lets say you have 2 compressors. lets just say both compressors are GM V5 compressors one belt driven, one driven by an electric motor. both compressors opperate with the same efficiency. the efficiency of the belt driven drive system is alot higher than electricity via an automotive alternator that is around 60% efficient. now for the loss of energy in the alternator, you need to make that up to spin the compressor up so your going to need 40% more torque to run that alternator to build up enough energy to run that compressor via the electrical system vs. that belt. and thats just 1 loss, there is loss in the motor, wires, and the loss for the belt which i am assuming is the same (it wont be the same but would be close).
C'mon now, let's be reasonable... There is a big difference between a belt driven automotive accessory and transmitting power over great distance.
But what are the losses over those high tension wires? How much losses are in the turbines and generators? I'm not an electrical engineer, but I'm guessing that less than half the fuel burned at the power plant ends up being used in people homes and businesses.
The rest is lost forever into the ether. I guarantee that it would be more efficient if we burned the coal or oil in our own homes versus the power plant.
If it weren't for Tesla we would be pushing DC though those wires and everyone would have to live a few miles from the power plant because the losses would be so high.
Turbines are ballpark %50 efficient. Transformers are >99%. Transmission line losses between here and the power station are small due to high voltage transmission. (lost energy = I^2 * R, where I is relatively small, as is R)
Distributing the power from one source is far more efficient than home-made burning, especially considering that upgrading one turbine can raise the efficiency of all the customer's power demands as opposed to literally billions of generators. Consider things like overhead of parts.
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The power plant itself is only about 45% efficient, and the conversion losses at each end are significant but economically acceptable.
Not hardly. Transformers at both ends are almost %100 efficient.
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I disagree, lets say you have 2 compressors. lets just say both compressors are GM V5 compressors one belt driven, one driven by an electric motor. both compressors opperate with the same efficiency. the efficiency of the belt driven drive system is alot higher than electricity via an automotive alternator that is around 60% efficient. now for the loss of energy in the alternator, you need to make that up to spin the compressor up so your going to need 40% more torque to run that alternator to build up enough energy to run that compressor via the electrical system vs. that belt. and thats just 1 loss, there is loss in the motor, wires, and the loss for the belt which i am assuming is the same (it wont be the same but would be close).
One thing at a time:
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the efficiency of the belt driven drive system is alot higher than electricity via an automotive alternator that is around 60% efficient.
Sure, if you use a 20 year old alternator. I'm sure that the design process over at Honda was like "Hey guys, I got this really cool idea that will make Fiero owners argue over the internet: lets power the AC compressors with electricity!"
Quality and modern BIG alternators wont be that bad. (Besides, where did yu pull that number from, anyway?) The efficiency of the alternator decreases with load ratio against its maximum rating.
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now for the loss of energy in the alternator, you need to make that up to spin the compressor up so your going to need 40% more torque to run that alternator to build up enough energy to run that compressor via the electrical system vs. that belt.
No, you meant %40 more minus belt losses. (which exist, otherwise they wouldnt wear out) This is, of course, assuming that the alternator is %60 efficient.
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and thats just 1 loss, there is loss in the motor, wires, and the loss for the belt which i am assuming is the same (it wont be the same but would be close).
The serpentine belt is losing energy whether or not its connected to an AC compressor or an alternator, thereofre that point is moot. Wires are also a non-issue as something that pulls ~1kW will obviously have big wires. Hell, if you are that paranoid why not just wire up a transformer between the alternator tap-out and the AC compressor? No more big and lossy wires to worry about.
The motor is also lossy regardless of its power source, so that point is also moot.
The motor is also lossy regardless of its power source, so that point is also moot.
see thats the thing, that point isnt moot, that is my whole point. my whole argument that a belt driven compressor system is more efficient than one that is electricaly driven. i am talking about the system as a whole. what i am saying is that an alternator and a motor to transmit the energy 1 foot to the compressor is less efficient than using belt power.
see thats the thing, that point isnt moot, that is my whole point. my whole argument that a belt driven compressor system is more efficient than one that is electricaly driven. i am talking about the system as a whole. what i am saying is that an alternator and a motor to transmit the energy 1 foot to the compressor is less efficient than using belt power.
But you make the assumption that the electric compressor is less than, or just as efficient as the ones we have now, and I have absolutely zero reason to believe such.
An automotive compressor takes around 10 horsepower to operate. 10 horsepower=7457 watts, or 37 amps at 201 volts. That is a lot to ask of an alternator, especially if you tried to do it at 12 volts (620 amps!!!!) A gas powered generator capable of that kind of power is going to take more than 10 horsepower to run because with any conversion there will be loss of effeciency. The powerplant down the road burns natural gas to make steam, to spin a turbine, to send electricity, to a step up transformer, to a high tension line, to a step down transformer, to my house, to run my heat-pump, to heat the house in the winter. If each conversion lost 1%, by the time the heat comes out my vents, it is down 10+% than if I just had a natural gas furnace and burned the fuel myself to make the heat. In a 12 volt car system, you would have to step the voltage up and have that loss, use the voltage/current to spin an electric motor and have that loss too. No matter how much voltage you use, it is still going to take 7457 watts and that will take more than the 10 horsepower to make than to run the compressor off the engine.
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01:31 PM
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
These electricity discussions seem to be more contentious than the 4.9 versus 3800SC
AP2K, you make a lot of valid points...electricity transformers are very efficient, (I'll give you upper 90s but not 100%), the I^2 R losses are low due to the high voltage used in the lines (about 7%)...all true.
But you can't blow by the 50% turbine efficiency. If I took the oil that was used to heat up the water to make steam and spin up that turbine and burned it in my oil furnace instead, I would get WAY more energy out of it than using it to make electricity send it to my home, through several conversions and then convert it to heat in my space heater.
The bottom line as any first year physics student can tell you is that it's always less efficient to transform energy from one for to another than to simply use it in the original form.
There may be compelling reasons to transform it...I doubt anyone wants a coal powered toaster...but there are unrecoverable energy losses every time energy is transformed.
I personally would like to have my own whole house electric generator, and get off the grid altogther. Before Natural gas shot up in price I thought we might see commercial fuel cells developed for the home. But we are probably decades away from that. I probably won't live to see it, but I promise you that generating the electricity in the plant is less efficient than if we did it ourselves where it was needed in the home, and eventually that's the way it will go.
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01:35 PM
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
The powerplant down the road burns natural gas to make steam, to spin a turbine, to send electricity, to a step up transformer, to a high tension line, to a step down transformer, to my house, to run my heat-pump, to heat the house in the winter. If each conversion lost 1%, by the time the heat comes out my vents, it is down 10+% than if I just had a natural gas furnace and burned the fuel myself to make the heat.
Cooter was typing the exact same message as I was typing mine.
The only reason it's economically viable is that the power company marks up the cost of electricity by a factor of 25 over the raw energy costs.
[This message has been edited by jscott1 (edited 08-16-2007).]
Ohh but I can! The reason is that it is irrelevant, especially to this discussion. It is a fact of life that they are %50 efficient, just as it is a fact of life that your engine is ~%33 efficient.
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The bottom line as any first year physics student can tell you is that it's always less efficient to transform energy from one for to another than to simply use it in the original form.
Which is why this physics student isnt an engineer. It is a general rule: it is never meant to be absolute. I have given you a specific example already of just such an occasion.
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I probably won't live to see it, but I promise you that generating the electricity in the plant is less efficient than if we did it ourselves where it was needed in the home, and eventually that's the way it will go.
Allow me to make an anecdote:
Which is more powerful, the Iron Duke or SD4? I can power two cars with a single SD4 or I can buy two Iron Dukes to do it. The SD4 weights 25 pounds more than the Duke. Both engines take X amount of energy to operate (frictional losses should be roughly equal since they are mechanically very similar). Which is more efficient both mechanically and economically?
Dirt cheap solar cells are within a decade of being economical. Just wait a little while longer.
[This message has been edited by AP2k (edited 08-16-2007).]
i am assuming the two compressors are equal as in my example both were GM V5's.
as far as compressor efficiency? the electric compressor that toyota uses is less efficient by design because it uses a variable displacement system that robs efficiency so the electric motor is not stopping and starting every time the evaporator temperature is too low.
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04:32 PM
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
Dirt cheap solar cells are within a decade of being economical. Just wait a little while longer.
Are you really an Electrical Engineer? I'm beginning to think you are just yanking my chain, You can't possibly believe this?
It wouldn't matter if Solar Cells rained free from the heavens, the solar flux is too low to be of any economic advantage. At a 40 degree latitude on a summer day you get about 600 watts per square meter. Even if you had 100% efficient solar cells and they were dirt cheap you couldn't compete with that natural gas fired turbine.
Have you see the International Space Station?
The arrays are bathed in pure sunlight with an area the size of a football field, do you know what the power generation is? About 75kW and you need TONs of batteries, (literally) to store the energy during the night passes, which even with only a 45 minute night, it's a struggle to keep the depth of discharge reasonable.
Here on Earth it would be even more difficult to store energy with a night much longer.
As for losing energy during a transformation...that's not generally true, it's always true... It's called the Second Law of Thermodynamics.
[This message has been edited by jscott1 (edited 08-16-2007).]
Looks like it uses standard AC hoses, would be easy to have new ones made to adapt it. 
