Utah Teens Invent Better Air Conditioner 755
Carl Youngblood writes "Two recent Utah high school graduates won the first-ever Ricoh Sustainable Development Award for inventing a better car air conditioner based on the Peltier effect. The peltier chips used in the device are more energy-efficient, last between 20 and 30 years, are solid-state, and don't harm the environment with ozone-depleting freon like today's car air conditioners."
/.ed (Score:3, Funny)
Frigidaire got to them... (Score:5, Funny)
Re:Frigidaire got to them... (Score:5, Funny)
Ka-ching!
fRe:e peltier with rebate (Score:3, Funny)
*informative, stupid*
Re:/.ed (Score:5, Informative)
"Today, the young inventors say, U.S. drivers use about 7.9 billion gallons of fuel each year to run their air-conditioners, which draw power from the engine. By adopting their contraption - which taps into the electrical system, using fans to blow hot air through five Peltier chips and then releasing cold air - they say the country stands to save 3.9 billion gallons of fuel annually, or about $10 billion based on current gas prices."
Re:/.ed (Score:3, Insightful)
Re:/.ed (Score:3, Informative)
Of course it is possible that the Peltier chips are more efficient, but considering the ones found on most electric coolers are around 60watts each I doubt it, considering you'd need 10-20 of them to keep up with the heat (the summers in CA are tough).
The real advantage would be that they are simple and wouldn't need to be
Re:/.ed (Score:3, Insightful)
Obviously the laws of physics are different in Utah - elsewhere the peltier effect was understood and applied decades ago. Heat pumps do it the easy way with a lot less energy than the peltier effect, which has to do it the hard way. It doesn't take a lot of energy to move a gas and expand it, which is why you get an order of magnitude more heat moved that way than with the peltier effect. It's interesting stuff (look up thermocouples to
Re:/.ed (Score:3, Informative)
I suggest you get hold of any first year university thermodynamics textbook - refridgeration is explained well in all of them.
One old and simple example is the kerosine refridgerator. In that case the compressor is a reservior of water, ammonia is the working fluid, and kerosine is used to provide flame to get some heat input to keep it
Re:/.ed (Score:3, Informative)
Re:/.ed (Score:3, Interesting)
After looking online at a few sites I did find some interesting peltier coolers that might do a good job, but you are still talking about 500-1500 watts
Re:/.ed (Score:5, Informative)
Older cars had horribly inefficent AC systems, and larger vehicles that have the equilivant of a house sized AC system also have horribly inefficent AC systems.
One of the most efficent AC setups in current production vehicles is in the Honda Insight and Toyota Prius. using less than 72 watts of electricity to run the electric compressor and a synthetic compressor oil + newer coolant technology.
you can not get near the efficency of a phase change cooling system with peltiers.
Re:/.ed (Score:5, Informative)
Completely false. This statement is a common urban legend, and nothing more.
Using your AC taps mechanical power from the engine. This requires you to use more gas to maintain the same speed. Opening your windows adds some wind resistance, but doesn't add the same amount of loss as engaging the AC compressor. (you should watch mythbusters sometime, its a great show!)
Re:/.ed (Score:3, Informative)
Completely true. While the A/C taps power from the engine, rolling down windows taps more power from the engine to overcome drag.
I have a 2001 Chrysler Sebring sedan with the 2.7 V6 and one of those nifty trip computers. I use synthetic oil. At 75mph, I get around 31MPG. With the A/C on, that drops to 29 MPG. With the A/C off and one window down, that drops to 26 MPG. (This is with the cruise control on - so no lead foot
Re:/.ed (Score:4, Informative)
I have always had small 4-cylinder cars, and in them, when you turn on the A/C, it feels like the car just hit a construction barrel. It's pulling a much larger percentage of power from the engine than on those big SUVs. That large percentage of power would translate significantly to lost fuel efficiency.
The other aspect about the Mythbusters test that was messed up was that they were running them around a closed-in, banked racetrack. The handling limitations of the SUVs on that track forced them to keep their speed down to about 45mph. Those two factors--the low speed and the sheltered from the wind environment pretty much take the wind resistance factor out of the equation.
So, myth: The Mythbusters show proved something about the A/C vs. windows debate? BUSTED!
Re:/.ed (Score:4, Informative)
1- When they tested the car at 55MPH using the computer it showed that using the AC was more efficient. Jamie wrote this off as "Yeah but the computer was measuring airflow and not fuel consumption." Modern engines use O2 sensors and closed feedback to maintain stoichiometry. As a result if you use less air the engine will inject less fuel to maintain stoichiometry or the appropriate air-fuel balance.
2- When they did the objective testing they drove at 45MPH and not the 70-80 commonly done on American highways (Don't claim people don't drive this fast- get on any highway in New Jersey, New York, Mass, or Maryland where I drive). Drag increases exponentially so this can make a _huge_ difference.
3- Instead of draining the fuel tank they siphoned it out instead. They could have missed the fuel in the sump on one car and gotten it on the other. As the difference in economy was only about 15 miles (less than a gallon of gas) it could have made the difference on it's own.
4- They used two different vehicles for the test- as the difference was so small then it could simply have been a result of engine differences, tire pressure differences, air cleaner performance differences, transmission slippage, etc.
-sirket
Re:/.ed (Score:4, Informative)
Change the speed to typical highway speeds (70MPH here in Michigan) and I bet the story would change quite a bit. I know that my car (a standard smallish sedan) drags quite a bit when you open the windows at highway speeds. Windows up and AC on, the throttle doesn't have to be depressed nearly as far in order to maintain higher speeds.
I'd agree that at 45MPH and below the AC is less efficient, but start getting up to faster speeds where the turbulance caused by open windows creates a *lot* of drag and I think the difference will be pretty obvious.
Re:/.ed (Score:3, Informative)
Didn't the Mythbusters prove this one false (albeit in a somewaht flawed test)? The car with the open window ran significantly longer on the same amount of fuel.
Re:Mythbusters (Score:3, Informative)
The next test was to be a 55MPH run around the race track to determine which of the test vehicles would run out a full tank of fuel first. Safety officials did not allow t
Re:/.ed (Score:4, Interesting)
"Invent" is a pretty strong word when you can go and find those mini in-car
If one determines that it takes 5kw to cool a space then that's what it takes. At that point, it dosen't matter except for efficiency and other factors (i.e. environmental concerns) what you use to move the heat, but that's the power you'll need to provide... Unless you're using magic or mutant powers or something.
In this car, we obey the laws of thermodynamics!
Re:/.ed (Score:5, Insightful)
The reason why the Peltier effect isn't used everywhere a heat pump is needed - and it's a really neat effect, mind you, as it has no moving parts, little to get corroded, is small and lightweight, etc - is that it's inefficient. We're talking god-awful inefficient until recently (~5%), and even now we're trying to stretch it to ~20% in the lab (no easy task).
As another poster mentioned, conventional refrigeration systems are quite efficient - at least, by themselves. Now, for a home refrigerator, it doesn't work out so nicely, because your power is being generated at 50% efficiency, transformed multiple times at a loss, suffers transmission losses on the way to your house, etc (that's why propane and even solar refrigeration systems are more efficient). But for a system like in a car, where the motor is directly running the compressor, it's going to be very efficient.
The Peltier chips - inefficient on their own - suffer from the inverse problem that the refrigerator suffers from! They need DC electrical power, but what the car engine produces is mechanical power! The car's alternator produces AC at a loss, which is rectified to DC, which then goes to the lossy Peltier chips. Assuming "ebay chips" are, say, 5% efficiency, we're looking at an overall system efficiency of 1-2%. Yeah, great way to save gas.
Re:/.ed (Score:5, Informative)
Domestic fridges are the most reliable applicances in the home because they are built as a completely sealed unit.
Re:/.ed (Score:3, Insightful)
1. equilibrium of the Halides in the upper atmosphere in destroying ozone, about 1:35 a BadThing(tm),
2. the tendency of the halides to concentrate over the poles, a GoodThing(tm),
3. the large number of balloons send up to study the "problem"
wouldn't it make more sense to just say, we don't know if it will help or not, but if your package doesn't have a chemical pack to sequeste
Re:/.ed (Score:4, Informative)
Re. Whatever ... (Score:3, Informative)
The chips are semiconductor chips that when current is applied exhibit the peltier effect. One side gets warm, the other cooler. Essentially a solid state heat pump. No compressor, no liquid refrigerant needed. Instead just blow air over the device and its "cold sink" (same essentially as the expansion side air handler for a liquid refrigerant system in principle). So fewer moving parts. Especially the blasted compressor clutch assembly which in some cases makes it cheaper to replace
Re:/.ed (Score:3, Informative)
No more freon in cars (Score:2, Informative)
No ozone depletion from hfc134a either (Score:5, Informative)
The current refrigerant, hfc134a contains no chlorine (the ozone damaging part of R12) and has an ozone depletion potential of zero.
The idea of using Peltier devices is interesting, because there'd be no mechanical parts to wear out, or refrigerants to leak out, so the system should be much more reliable, but I thought Peltiers would require a huge amount of current to do as much cooling as a car A/C system delivers.
Re:No ozone depletion from hfc134a either (Score:5, Informative)
The car's electrical system is not suited to supplying significant amounts of power. A typical alternator tops out at about a kilowatt of power (80A or so). Due to the low voltage, ridiculously large currents are necessary.
Of course, a peltier is much less efficient than a compressor system. A compressor typically has a coefficient of performance (COP) of around 3, meaning that it removes 3 units of heat for every unit of supplied work. For peltiers, this value is around 0.4, which is a huge difference. Thus, the peltier would consume about 7x more energy to supply the same cooling capacity. This is the main reason cars don't use peltier A/Cs.
Re:No ozone depletion from hfc134a either (Score:3, Informative)
Pelters aren't very efficient.
Furthermore, if they were a good means of cooling things, we would use them for everything, but they don't thus why some kids build it, and corporations don't. If would be massively cheaper for them to use and have nothing but benefits. But they suck for the job, thats why they don't use them.
But people seam to be missing that part of this thing. I'm guessing all the articles are gone cause someone pointed out how bad a st
Re:No more freon in cars (Score:3, Informative)
Freon != R-12
Re:No more freon in cars (Score:5, Informative)
R134a A/C systems have evolved over the years. Granted, the early systems left a lot to be desired, but the output of the recent systems rival that of old R12 systems. R134a systems are very pressure-dependent, far more than R12, and must be precisely charged for maximum effectiveness.
It's hot here in Texas, at or above 100F in the summer, and both of my Chevy trucks (an '02 and an '03) blow frigid air.
Re:No more freon in cars (Score:5, Funny)
I have been proven wrong by slashdot once again.
Re:No more freon in cars (Score:5, Interesting)
Re:No more freon in cars (Score:3, Informative)
Re:No more freon in cars (Score:4, Informative)
I briefly discussed this topic recently [slashdot.org] when we were talking about keeping computers cool. The heat problem is becoming so critical that Intel is actually designing a Pulse Tube cooler for their microprocessors!
Re:No more freon in cars (Score:3, Informative)
You're right that the AC keeps you cooler, though...
Re:scientific method? (Score:3, Insightful)
King Bedevere does a better job of establishing a woman's witch-hood than those guys do "explaining" everyday occurrences.
[Addendum] (Score:5, Insightful)
On a related note, remember when MTV involved music?
And the Republican party was conservative?
Re: (Score:3, Informative)
Re:No more freon in cars (Score:3, Informative)
Other companies around the world do pay for pensions and health care as well. Not by setting up their own insurance funds, but by paying higher salaries (to compensate for the higher income taxes on those salaries) and by paying sometimes quite high employer fees. The difference is really that in state-run system everybody shares the cost, while for the US carmakers they are stuck wi
Insurance scales horizontally (Score:3, Insightful)
Specifically, the more healhty people you have in the system, the less the overall cost is per capita.
This is why the US system fails, because we only worry about insurance if you aren't healthy.
Re:No more freon in cars (Score:4, Insightful)
Try again.
Re:No more freon in cars (Score:5, Insightful)
You mean compared to countries like Germany and France ? (Well known everywhere as bastions of conservative capitalism and mercifully free of the unionised workplace).
Re:No more freon in cars (Score:3, Insightful)
Re:No more freon in cars (Score:3, Informative)
The overall 12.5% jobless rate is clearly not a result of unionization or social programs as you imply, but from re-unification problems. I dare say that if Mexico were added to the US overnight
Re:No more freon in cars (Score:3, Interesting)
According to my company, the non-cash benefits I receive cost them (and our customers ultimately) more than half my cash salary in addition (I do have an excellent benefit package though)
>> And Japan has alot of socialized services, such as National Health Care. As a result, the Japanese corporations are able to remain much, much more competitive
having company-run unions help the japanese corps *just* a little bit
freon? (Score:2, Informative)
Ahem. "Today's" cars use R134a refrigerant, not ozone-depleting freon. This has been the standard for a little less than ten years now.
Re:freon? (Score:5, Insightful)
The peltier chips used in the device are more energy-efficient, last between 20 and 30 years,
I have a solid state ice chest. I don't believe the expected life rating when applied to a solution where condensation is present. It does not apply when they are used in high humidity. Corrosion from condensation kills these in a very short time. The module in my fridge died long ago from condensation caused corrosion. I would not want these in any application that runs below the dew point. Since my AC in my car is designed to run below the dew point to defog windows, there is no way I want a cooling solution that dies when it gets wet. Speaking of more energy-effecient; More effecient than what? Older modules, compressor driven? I have not seen any peltier chips ready to replace the compressor driven freezers and window AC compressors. They simply don't remove enough heat.
An advantage a working fluid AC has over a solid state solution is the hot side can be far removed from the cold side. The radiator for most car AC units is in front of the engine in cool air. A solid state AC would have the hot side behind the engine next to the passanger compartment. Just where were they planning on putting their waste heat? A typical car AC unit is over 20,000 BTU's. How many BTU is their system?
sweet! (Score:2, Funny)
great. (Score:2)
Re:great. (Score:2)
Now I can overclock my car's OBD-II computer.
Don't bother. It's time to upgrade to the CAN interface.
Google Cache (Score:5, Informative)
Re:Google Cache (Score:3)
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Freon isn't used in new cars! (Score:4, Informative)
Newer car air conditioners use refrigerant R-134a. This is *not* an ozone destroyer, but it is still a greenhouse gas.
Peltier coolers use electricity, which is generated by the horribly inefficient internal combustion engine which produces greenhouse gasses and other toxins by the boatload.
It's all bad.
Re:Freon isn't used in new cars! (Score:5, Informative)
Not to nitpick, but the compression cycle of regular car AC is also powered by the motor...
Plus, if your alternator can handle it, the peltier is probably much lighter, and certainly much smaller, further improving your engine efficiency.
m
this is not a sig
Re:Freon isn't used in new cars! (Score:4, Interesting)
These kids won against others because they did something others with knowlege knew was no big deal, and those that judged only looked at it superficially and thought it was a big deal.
It reminds me of a famous artist that developed an apparent way of dramaticly inproving fuel efficiency in internal combustion engines. By putting a spacer under the carby he optimised the motor to run while idling, dramaticly reducing the amount of fuel it used on a test bed - because the motor had been optimised to run at a specific load. He completely missed the point (that you want the motor to do something) and the press didn't realise either. The judges in this competition have also missed the point and gone for drama over utility.
Re:Freon isn't used in new cars! (Score:5, Informative)
The parent poster is absolutely correct, R134a is a greenhouse gas. However, that statement should be qualified: it is only a greenhouse gas when it is released into the atmosphere. Modern technicians use recovery equipment to remove refrigerants from cooling systems (everything from your freezer to your central A/C). The refrigerant is either recycled, or disposed of properly.
As long as we are all conscious about our environment (and we all should be, lest anyone turn us in to the EPA, causing us to have to fill out the reams of paperwork!) there is no problem. Oh, and there is always that pesky thing about preserving the planet for generations to come
I, for one, am quite sick of people blowing things out of proportion when there is no real problem. Having said that, kudos to the two teens for their inventive spirit. Maybe with some refining, the invention will prove more efficient and ultimately prove commercially useful!
Re:Freon isn't used in new cars! (Score:5, Funny)
Syntax error.
Re:Freon isn't used in new cars! (Score:3, Insightful)
Re:Freon isn't used in new cars! (Score:3, Interesting)
Another theory of mine (and it is strictly a theory, absolutely *zero* research has been applied to proving or disproving this theory) is that as we develop more and more enclosed space, we are heating the planet more and more. Here's how it goes:
Air conditioners remove heat from the air
Re:Freon isn't used in new cars! (Score:4, Informative)
The seemingly trivial change of having a light colour roof can substantially reduce air conditioning requirements (although it can also increase heating requirements).
That depends on what was done when changing the roofing materials. For a couple summers when I was in college, I had a job as commercial roofer. We would rip off the layers of tar and rocks that had built up over the years. In its place, polyurethane foam insulation would be sprayed down and then coated with a thick rubbery paint. We would normally see a big difference in how much the A/C units were running before we were even 1/2 way done. The cost savings due to using less energy all year round usually paid for the roofing in a couple years.Re:Freon isn't used in new cars! (Score:5, Informative)
#13120684: Normal peltiers have an efficiencies of less than 30% Modern air conditioners have an efficiencies approaching 400%.
#13120746: Modern aircon works by using matter phase change and using pump to move the fluids. It transfers more heat than the energy consumed in moving the fluids.
So while I don't have one of these, I'm really really sceptical that the CO2 and other greenhouse emissions per unit of cooling by a peltier can get anywhere near a modern air conditioner.
Re:Freon isn't used in new cars! (Score:3, Insightful)
Fatter alternator due to the giant amount of power consumed by a 40% efficient peltier. (Move 1 unit of heat with 2.5 units of power in)
VS
A/C compressor with a COP of 3 (move 3 units of heat for 1 unit of power in)
All that energy's got to come from somewhere. A typical car A/C is around 3-4kW. Or about 2kW of power to drive an A/C compressor. So, for a peltier equivalent, that's 10kW of electrical power from the alternator, driven from the engine, for the peltier array to get the same
Re:Freon isn't used in new cars! (Score:3, Insightful)
Ammonia might not be a good idea for Joe Lugnut the backyard mechanic. One good whiff of ammonia can actually kill you. Granted, its properties are a dream for refrigeration cycles, but there's a reason why it isn't used in consumer products.
Theoretically, one could stick reverse Peltiers all over the catalytic converter too, and use the thermoelectric generated power to run the cooling Peltiers. It would be grossly inefficient
Re:Freon isn't used in new cars! (Score:3, Insightful)
But your grammar-deficient tirade was fun anyway.
Since the article seems to be AWOL now... (Score:4, Interesting)
RSDA Press release (Score:2, Informative)
(PDF)
The problem is the power supply from the Altenator (Score:5, Informative)
No one notices a few Kilowatts disappearing. Except ricers.
Peltier devices come from the Altenator with an output capacity of around 1Kw or less, And most of that is used by Lights, Engine management etc... And for charging the battery
There's not a lot of electricity spare to run a Peltier based cooling device.
I've built something similar myself for a car once, but it only provides piped air - and didn't have to cool the whole cabin.
A 12 amp peltier device consumes a LOT of power... About 150 watts Not all cars can spare that much. And it doesn't cool much either.
I'm sorry I can't get the article up though. I really wanted to read it
Good on them though for experimenting
GrpA.
Re:The problem is the power supply from the Altena (Score:3, Informative)
Not necessarily. The Toyota Prius, for example, uses an electric (144V AC) A/C compressor. Of course, it's the exception, not the rule. The Prius has a high-voltage battery system and a powerful inverter.
"A 12 amp peltier device consumes a LOT of power... About 150 watts Not all cars can spare that much. And it doesn't cool much either."
True. 150W is a lot to ask of a typ
Re:The problem is the power supply from the Altena (Score:3, Interesting)
If you push the pedal to the floor with the A/C on you'll get your performance, at the cost of warmer air until you are done.
"can't tell"? (Score:5, Interesting)
I'm sorry, but you're completely full of shit. Every time my A/C compressor clicks on while I'm driving, I can tell; I drive a manual, and if I'm paying enough attention, I can tell especially if revs are low (ie 2k).
Vapour phase airconditioning uses direct power from the engine, which often has an output of 100+ Kilowatts.
You are making the assumption that the engine produces its power evenly across the band, which is outright garbage. Most engines make much more horsepower at high engine speed; better engines tend to keep making that power the closer they approach redline (at high engine speeds, resistance in exhaust and intake paths kills horsepower because volumetric efficiency drops).
The engine will not make NEARLY as much power down at ranges people typically use; ie 2000 to 3000 RPMs. Example- the current Ford Mustang engine (no, I don't drive one- just the first chart I could find) makes 250HP at 5,000RPM+. At 2,500 RPM, it makes 100HP. The chart started at 2,500; numbers probably drop to 50HP at 2000. Suddenly, an AC compressor that uses several HP becomes a two-digit percentage of total engine output. While humans suck at absolute measurements, we can be -really- good at picking up on the finest relative differences.
Also, maximum claimed horsepower is often under ideal circumstances; ie cool air temps, engine cold/warm not at full operating temp, lightweight oil, and at sea level. It's also always on a perfectly functioning engine; ie fresh air cleaner, ignition bits are all new, perfect compression in all cylinders, etc.
Re:"can't tell"? (Score:3, Informative)
troll (Score:3, Insightful)
Of course you can tell when it clicks on. However, in 99% of the cars out there, the A/C does not effect driveability a noticeable amount.
This was the grandparent's point. So the air conditioner takes up, say, 5% of your engine power while you're cruising at a low RPMs. Big deal. Maybe the c
Re:"can't tell"? (Score:3, Interesting)
Turn off your headlights and your foglights (driving with them on makes people look like a dorks anyways) and you will have more than enough power restored for the AC.
My econobox that get's 42mpg went up to an average of 43mpg when I disabled the Daytime Running lights that was simply a diode that was turning on the headlamps when the car was running.
granted i drive highway speeds 909% of the time, but ther are many more power
Re:"can't tell"? (Score:3, Insightful)
Um, dude, you're wrong. Ford claims that the air conditioning compressor alone will use 25 HP on a hot day.
Your headlights, OTOH might use 10 or 20 amps. At 13.5 volts, thats 270 watts max. Or about 1/3 of one horsepower.
Bad Link - better one (Score:5, Informative)
Re:Bad Link - better one No Just Bad Science (Score:3, Informative)
Since when do they hand out awards for bad research at best or out-and-out lying. A peltier effect heat pump has a COP of around
New car electrical system (Score:3, Interesting)
Wasn't there supposed to be a new 48v electrical system standard for all cars by now?
It would allow people to hook up better electronics to their vehicle, plus it would make the car more energy efficient. The example I heard was that instead of a belt driven AC unit, it would be electical.
The article I had read at the time stated that the standard would be implemented in 2005. Does anyone know about this?
Re:New car electrical system (Score:3, Informative)
The article I had read at the time stated that the standard would be implemented in 2005. Does anyone know about this?
The only car I know of with an electric sealed compressor instead of a belt driven compressor is the 2005 Prius. It runs off the 400 volt hybrid battery, not the low voltage side of thi
It's Actually 42v (Score:3, Informative)
It looks like there is the Toyota Crown Royal which uses 42v and a "new SUV from GM" that will use 42v as well. Source. [66.102.7.104]
In today's society... (Score:4, Insightful)
Last longer?
Better for the environment?
It'll never catch on.
Comment removed (Score:4, Interesting)
not as efficient... (Score:3, Insightful)
This is just total bunk. The only way it saves energy is by not cooling as much.
Honestly, I think that the only threat to phase-change systems in small systems is sonic cooling. It could be more efficient, require less maintenance and have less environmental impact than a phrase-change system.
Evaporative systems are nice too, especially for large installations, but don't work for getting much below ambient.
cool things about this idea (Score:4, Interesting)
2. unit can be in passenger area and not in engine compartment
3. you could have several small units instead of one big one
4. flip the peltiers and you have a heater
5. no pulley being spun even when not in use
6. should be much lighter (although alternator would get bigger)
The Official R-12/R-134a/Freon Thread (Score:5, Insightful)
The noun "Freon" has a double meaning. Strictly speaking, it is the trademark name of refrigerant R-12, a single product of a specific formulation.
Due to its popularity it has become a sort of catch-all term used to describe an entire family of products. Much the same way that all couches can be called Chesterfields or all tissues can be called Kleenex, Freon can be used to describe a family of refrigerants.
As well all know, the actual Freon refrigerant, R-12, has been banned for a decade now. In this way, it is proper to say that no air conditioning unit in the US, Canada, etc., made since 1995 uses Freon.
The currently widespread refrigerant is R-134a, trademark name "Suva". It's chemically different from "Freon", but can be described as being part of the Freon family. This can make casual discussions a bit muddled as everyone argues whether or not Suva is Freon... Well, maybe I'm the only one having that type of casual discussion...
So, to make a short story long:
Freon is a Freon, Suva is a Freon, but Suva is not Freon. Got it?
Been there, done that (Score:3, Insightful)
There is nothing novel or innovative about this.
Many, Many, Many things wrong with the article! (Score:4, Insightful)
- Peltiers are efficient-- NOT! They have an EER of way less than 1.0. A window air conditioner is above 10. End of discussion.
- There's no way to make them more efficient-- think-- they have their cold side right next to their hot side-- there's a lot of thermal conductivity there, effectively undoing a big percentage of the cooling.
- It's NOT more efficient to draw electrical power than to draw engine power. Somehow the kids think the alternator turns for free. Nope, it draws engine power just like the old AC, and as all defvices are less than 100% efficient, it has to be LESS efficient to use the power downstream from the alternator. { Minor caveat-- the alternator has the advantage of being able to put out more constant power-- direct drive from the engine to the compressor results in less AC (but not necessarily lower efficiency AC) available at slow engine speeds.)
- A typical auto AC puts out 30,000 to 50,000 BTUS/hr of cooling. A 1x1 inch peltier chip does about 150 BTU/hr at a cost of $9.95 on the surplus market. To duplicate a regular car AC would require 200 to 350 chips, $2000 to $3500. Plus a bunch more alternators, they'd need 1400 amps, about 20 alternators. Hard to fit them all under the hood.
- Peltiers do not last forever. They're prone to breakage due to cyclic stresses and degradation from humidity.
A REALLY bad aricle. The laws of thermodynamics rule.Clueless kids (Score:4, Interesting)
These kids didn't really test their system - as in, make measurements of fuel economy with the old system and with the new system in real conditions and see what the difference was. They just assumed that "If we get rid of the load from the compressor, we will save 10 HP that will save X amount of fuel" (ignoring the load from the alternator).
Now, if they had wanted to REALLY do something that would cool the vehicle without costing more gas, they would have mated an adsorption cooler [lpappliances.com] to the exhaust manifold, and recovered the energy to run the cooling system from the waste heat discarded to the atmosphere.
A few points (Score:3, Informative)
Here are a few of the things that become possible with that kind of available power:
Re:Peltiers (Score:4, Funny)
Re:Peltiers (Score:2)
Re:Peltiers (Score:2, Insightful)
Theoretically.
Re:Peltiers (Score:3, Informative)
Efficiency is a measure of how much useful energy you get out of a system compared with what you expend in doing so (contrast that with efficiacy).
Going by this a bar heater is 100% efficient, since any energy lost in the cable, etc is radiated as heat, which is useful energy for the purpose of heating a room.
Now heat pumps usually consume electricity to move heat from one sink to another. Once the cycle is
Re:Peltiers (Score:5, Insightful)
Ummmm, I believe the term you want to use is "coefficient of performance" - which is how many watts of heat are transferred per watt of electrical power used. Also called an energy efficiency ratio.
Having said that, your point about the relative efficiencies of mechanical refrigeration units vs Peltier effect devices is correct. I have a ~18 cu ft fridge in my garage that uses less energy than a 1 cu ft Peltier cooler. Another point, the main focus for the development of Gadolinium refrigeration was to replace Peltier effect devices for small scale refrigeration needs.
Re:Peltiers (Score:3, Informative)
COP is defined as HEAT_RATE_REMOVED_FROM_COLD_RESEVIOR/WORK_RATE_RE Q UIRED_TO_RUN_THE_PUMP
(also written as Q(dot)[L)/W(dot)[pump]). A simple thermodynamics course in Mechanical Engineering will tell you that THE maximum efficiency an refrigderator (reverse heat-pump, such as an air conditioner) can reach is T(L)/(T(H)-T(L)) where T(L) is the absolute* scale temperature of the low heat resevoir and T(H) is the absolute scale temperature
Re:Peltiers (Score:5, Informative)
Re:Peltiers (Score:3, Informative)
If I recall my physics even somewhat correctly, the amount of energy it takes to convert a gram of water at 32F from solid to liquid state is 80 calories. That same
Re:Peltiers (Score:3, Informative)
If you need 1kW (or 1kJ/s) to displace 10kW (10kJ/s), the COP is 10. This means the displaced energy is ten times as much as the energy used to move it.
Now, the catch with Peltier elements is that they have high COP only at very low power and small temperature difference, usually around 5-10% of the power rating and 10C temperature difference. Unless they are operated under th
Re:New AC (Score:3, Insightful)