Utah Teens Invent Better Air Conditioner

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."

Comments

No more freon in cars

[ToadMan8]

Cars sold in the states haven't used Freon since the late 90's. That's why A/C sucks in cars now.

Re:No more freon in cars

[jimi the hippie]

All cars with A/C still use freon. They don't use R-12!! (which is the stuff that supposidely depletes the ozone, and has been illegal since about model year 1995, NOT the late '90s)

Freon != R-12

Re:No more freon in cars

[pongo000]

This should actually have been modded as "misinformed" (don't we wish...)

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

[minus_273]

well that and the insane amounts they have to spend on workers salaries and benefits when compared to the rest of the world. There is no way they can compete. It's funny when you realize that becasue of the unions and their short sightedness, many of those jobs will disappear in the next decade or so.

Re:No more freon in cars

[Anonymous Coward]

R-134a is still considered a Freon. While it has a low ODP - ozone depletion potential, it is still considered a greenhouse gas so it is not complete innocious. Hydrocarbon blends are used for cooling systems all over the world but greatly discouraged in the US (propane, the major component, was $1.74 a gallon when I filled a tank last week) Can anybody say Profit?

Re:No more freon in cars

[JanneM]

well that and the insane amounts they have to spend on workers salaries and benefits when compared to the rest of the world.

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 with the bill for a lot of workers all by themselves.

Re:No more freon in cars

[AKAImBatman]

Errr... no. There are no cryo liquids in these coolers. They're used to make cryo liquids, although in much bigger form than you'd use in a car. A Stirling Engine is a reasonably simple device. You have two pistons, a regenerator, a hot surface, and a cold surface. Heat the hot surface, and you get energy as the heat is pumped to the cold side. Apply energy to drive the engine, and the cold side will pump all its heat to the hot side, making it that much colder. Damn efficient devices, they are.

I briefly discussed this topic recently 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

[dreadknought]

The EPA also approves about twelve refrigerants for use in automobiles. You know how many the automotive industry approves? two. R-12 and R-134a. You will never find a shop anywhere in the world that will charge your A/C with anything but R-12 or R-134a. Just because the EPA approves something for automotive use doesn't mean the industry will. Afterall, the EPA most likely aren't experts in the field of automotive airconditioning.

Re:No more freon in cars

[mrchaotica]

They proved that false on Mythbusters a while back. Of course, wind resistance increases with the square of the speed, so the faster you go the closer you come to breaking even. Seeing as how they tested at 55 MPH (I think), if you're doing 70 or 80 the AC might be more efficient.

You're right that the AC keeps you cooler, though...

Re:No more freon in cars

[forty7]

Since you're picking nits anyway... :o)

98.6 is a fairly bogus number with respect to significant digits. It is just 40C converted to Fahrenheit, but even that number is plus or minus a degree or two for normal population distribution.

It's just 37C converted to Fahrenheit. 40C is 104F.

Re:No more freon in cars

[DigiShaman]

No, A/C sucks because the major car manufacturers are too lame to figure out how to build good A/C without Freon. It's possible, they just won't do it.

American auto manufacturers especially. They fail to innovate, and are going down the tubes. Nobody to blame but themselves, really.

As long as it's American bashing going on, this WILL get moderated up.

Fact is, EnronHaliburtons post is a troll! And he knows jack shit about the auto industry or how A/C systems work in general. Had he done his homework, you would realize that the FACT is R134 is LESS efficient then R12. That's correct EnronHaliburton2004... you troll. Do your god damn homework. And no, I won't do it for you. Google it.

While were at it, AC systems have always blown less cool regardless of the auto manufacture. This isn't an American sucks issue. This is an R134 sucks "issue". I bet my Honda on that!

Re:No more freon in cars

[mboverload]

They did a special episode behind the scenes that shows they really DO do experiments over and over again. Lots of times. It would just be boring to put that in the episode.

Re:No more freon in cars

[Anonymous Coward]

IAAME (mechanical engineer)and work in the cryo field, I'll contribute my $.02. Actually, Stirling cryocoolers do cost more to mass produce than regular A/C units. The tight tolerances and high grade materials required drive up the cost. Cryogenic applications require oil-free compressors and expanders because the oil would work its way to the cold head and freeze, destroying the cooler. Oil-free compressors don't have the reliability for an automotive application.

IAASAEM (Society of Automotive Engineers Member), I don't work in the automotive field, but I'm a geek interested in cars. From their magazine: The automotive industry calculates cost to the penny, and if there was some technology that was cheaper, improved mileage, or help cut emmisions (by not working the engine as hard), they would probably use it. There are numerous technologies in the works, but changing the A/C involves changing a massive infrastructure from manufacturing to maintanence.

Re:No more freon in cars

[instarx]

Your statistics are misleading and mis-applied. The German unemployment rate for June 2005 was a whopping 20.5% in the former East German sections of Germany, while the country's overall unemployment rate was 12.5%. Therefore the western, industrialized, parts of Germany have a rate roughly comparable to the US.

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 our unemployment rate would skyrocket too.

freon?

[schematix]

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."

Ahem. "Today's" cars use R134a refrigerant, not ozone-depleting freon. This has been the standard for a little less than ten years now.

Google Cache

[j00bar]

If you're having trouble seeing the article, try this: Google Cache

Freon isn't used in new cars!

[DarkHelmet433]

Freon (R-12) hasn't been used in new cars for something like a decade now. R-12 is an ozone depleter. It hasn't been manufactured in the US since the mid 90's or so

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!

[Muerte23]

Peltier coolers use electricity, which is generated by the horribly inefficient internal combustion engine which produces greenhouse gasses and other toxins by the boatload.

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!

[DarkHelmet433]

To refer to posts above, the peltier coolers have a severe disadvantage.

#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!

[ErichTheWebGuy]

OK, allow me to put some things into perspective. In addition to being a MCSE, A+, etc. certified geek, I also hold EPA certification to handle refrigerants and to service and install refrigeration systems in commercial, residential, and automotive applications.

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!

[turbod]

Are you nuts? You need to take some heat pump theory, or just plain old thermodynamics.

Heat pumps are cheaper to run because they don't _create_ or _take_ any more energy than necessary to compress and move the fluid through the system. The temperature difference between the hot and cold side, combined with phase change properties in the fluid is what makes air conditioners so efficient.

You have to power the pump, but no more.

Compare a 20,000 BTU strip heater's power consumption with a 20,000 BTU heat pump.

Simply put, you need to check your facts before you post cheeky stupid comments.

Furthermore, the people who gave this award to these kids are most definitely graduates of the New Math way of thinking, ie., no point in obeying proven facts when we can make up what we want along the way to make older proven and better technology look bad by putting kids faces on it.

The educated know what New Math was really about --- but it has been corrupted into what we see here in this article, which is just plain stupidity and laziness about checking facts.

A Peltier Junction emits more heat than it moves, and fails the test for good technology at the scales where a compressor is not too much of a burden on the rest of a design. In addition, running a current drain system like a peltier junction off of 12Vs at the size required for a car (20,000 BTU or more), would require a alternator that would be so inefficient at out of rpm conditions, that twice the amount power wasted at the peltier, at least, would need to be wasted just to keep the stupid alternator rotating against the humongo bearings and cooling fan necessary to cool the damned thing.

Geez people, read the physic manuals before you make stupid assessments.

TurboD

Re:Freon isn't used in new cars!

[ksheff]

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!

[grgyle]

"...I welcome any contrary evidence..."

There are some basic physics nits to pick, I'd recommend reading up on guys like Carnot, Boyle, etc. When A/C coils pass heat to the outside surroundings, they are *not* creating a net increase in overall heat, they are simply moving existing heat from one place to another. The heat you feel coming off the back of your fridge is simply the heat that was contained in the interior of the unit. Once cool, the A/C only has to work to maintain a temperature difference, pushing already existing energy back to the outside--it doesn't continually pump heat willy-nilly into the atmosphere or create it from nowhere.

If left at rest, your fridge or office building would gradually warm as the energy migrates back in through conduction and convection, until everything is at equilibrium. Using your argument, if everyone turned off their A/C at once, we would risk global cooling as all of that outside heat gets sucked back into the buildings!

The only net heat increase happening is due to mechanical and electrical inefficiencies in the motor and compression cycle. All mechanical systems do this.

Re:Peltiers

[USSJoin]

400% efficiency?

This seems unlikely to me, simply from a conservation-of-energy perspective. Every first-semester Physics course teaches that even 100% efficiency is unattainable in the real world; there will always be losses due to friction or whatever.

But if you've seen an air conditioner with 400% efficiency-- then why are we working for better energy sources? This would be the magical Infinite Energy Box! Let us all dance and celebrate!

Re:Peltiers

[HermanAB]

An aircon using vapour change effects is a heat pump. Therefore, it can move more heat, than the amount of energy consumed to move the heat.

RSDA Press release

[mabinogi]

Here's the press release from the awards themselves, since TFA is dead.
(PDF)

The problem is the power supply from the Altenator

[GrpA]

Vapour phase airconditioning uses direct power from the engine, which often has an output of 100+ Kilowatts. More in a recent design.

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:Peltiers

[matt21811]

I could have made it more clear but your understanding and explanation are correct.

It is entirely possible to move 4 watts of heat energy out of the car with only 1 watt of electricity energy.

Bad Link - better one

[WindBourne]

For the naysayers, it does say that it saves some 4 MPG over current ACs. IOW, it is more efficient.

No ozone depletion from hfc134a either

[name_already_taken]

Freon is trademark used for a variety of nonflammable gaseous or liquid fluorinated hydrocarbons which are no longer used as motor vehicle refrigerants.

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

[alienw]

I thought Peltiers would require a huge amount of current to do as much cooling as a car A/C system delivers.

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

[UniverseIsADoughnut]

Yeah, I think people are missing simple facts here.

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 story it was.

Re:What an ironic twist.

[B4L1STA]

1) It's spelled "Mormons"
2) The trib moves the URL after it's no longer in the day's news
3) The trib isn't a Mormon paper. The Mormon paper is Deseret News (www.desnews.com)

But I have to admit, the poor Trib probably isn't used to getting slashdotted :)

Re:Peltiers

[arch_avaj]

Hmm, just reading my physics textbook a few hours ago about this topic, so I can clarify the obvious mistakes.

AC's have a Coefficient of Performance (COP) around 4-5 (or 400%-500%)
This is similar to effiency, but obviously not the same.

COP of a cooling device is measured as:
(Energy Removed from Cold Reservoir) / (Work Done on the device)

AC's don't cool, they just move the heat, and moving the heat doesn't require a lot more energy.

If this new device has higher efficience, it will have a similarily higher COP.

Re:/.ed

[pcmanjon]

Ahh, I "read the fucking article" and now I understand. The main article makes you think a couple of chips save the day, and makes A/C's last longer. They do, in a way, but the article on ./ here should have quoted the real article, instead of trying to paraphrase.

"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

[HeroreV]

It doesn't say 20 to 30 years longer, it just says that the peltier chips "last between 20 and 30 years". I have no idea why you just randomly inserted a word, but that's exactly what you've done.

Re:The problem is the power supply from the Altena

[RzUpAnmsCwrds]

"Vapour phase airconditioning uses direct power from the engine, which often has an output of 100+ Kilowatts. More in a recent design."

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 typical car. But a hybrid vehicle, like the Prius, can put out 5+ KW continuously without breaking a sweat.

"Good on them though for experimenting :)"

Well, if they have developed a peltier system that rivals an electric-powered vapor-phase system in efficency, their technology could very well find its way into future hybrid vehicles.

Bad pics at wilki

[bxbaser]

Certainly isnt what i was expecting

Re:Peltiers

[Trogre]

If your goal is to generate heat, then yes you're right. But that's not what we're talking about.

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 started, the useful energy that is transferred is much greater than the energy you're expending to drive the pump. Therefore you're getting more energy out than you're consuming.

By consuming I of course mean converting energy from one form to another. And no this does not violate principles of thermodynamics since we're not converting the heat into another form.

Re:/.ed

[Anonymous Coward]

WHY ON GOD'S GREEN EARTH IS THE PARENT MODDED INSIGHTFUL?

Ok, get this straight... from the article and what I know of the peltier effect (yes, I'd like a better primary source concerning the structure of the students' system given GM's naysaying), this is only a modification of an air conditioner system in the sense that it still has an internal loop for conditioned air cooled by a heat exchanger/evaporator (for lack of a better description of the peltier equipped analogue) -- the system no longer has a compressor, condenser, and coolant loop.

Instead, the peltier drives one side of the heat exchanger/evaporator to cool the conditioned air loop, and SIMULTANEOUSLY pumps the absorbed thermal energy and the peltier waste energy to the other side of the heat exchanger to dump the heat into a waste air stream.

I.E. - no coolant liquid (water, ammonia, R12, or R134a) and no inherent moving parts in the core cooling system (compressor), at the price of significantly higher electrical energy demands (the A/C system is mechanically driven and does not require a mechanical/electrical conversion step).

THIS IS NOT A CASE OF "PLUG IN THE MAGIC CHIP". It's the difference between installing a peltier CPU cooler and one of those phase changing multi hundred dollar monstrosities.

Re:New car electrical system

[Technician]

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?

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 things. They didn't bother to stop at 48 volts.

Re. Whatever ...

[Tjp($)pjT]

The new stuff is r-134.
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 the whole compressor with a rebuilt one than separate the clutch from it. The clutch causes the pulley to spin freely and not drive the compressor when cold is not demanded by the air temp controls, hopefully thermostats, but n ot always in cars.

in your disk drive analogy, it would be like coming up with a cheap flash drive that beat the specs for lifetime and cost to those spinning magnets you mentioned. It makes it last longer by eliminating wearing spinning parts that rub against each other roatating and moving up and down and up and down ... Not sure how the parent was maked "insightful" but there is no "lacks relevant technology background". Seriously though it is fascinating technology and along with heat pipes makes overclocking much less of a mess.

Re:Bad Link - better one No Just Bad Science

[truckaxle]

The students' research estimates their system would cut millions of pounds of hydrocarbons and nitrous oxides, and billions of pounds of carbon monoxide found in vehicle emissions. It also would increase gas mileage by four miles per gallon and hike horsepower by as much as 4 percent -- saving American drivers billions of dollars in annual gasoline costs.

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 .3 and a typical R134a vapor compression AC has a COP of about 4. In other words, the existing AC systems are an order of magnitude more efficient. Now how are they going to increase the mileage by 4 and add more horsepower?

They would have to increase the size of the alternator several times to power this a peltier effect heat pump and you would have the unavoidable inefficiencies of converting mechanical energy into electrical to boot.

Why didn't they just mention that this thing runs off of cold fusion - and maybe they could get the University of Utah to endorse it ;(

Re:New car electrical system

[Anonymous Coward]

Wouldn't an electrical AC unit be less efficient? You need to convert energy from the motor to electricity and then back into motion all of which is not 100% efficient.

It's Actually 42v

[mrdrivel]

The new standard calls for 42v not 48.

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.

Re:Peltiers

[gerardrj]

I think what's being referred to is the heat the unit moves vs the heat it generates. Refrigerant based units rely on phase change of matter (gas to liquid to gas...) which requires the absorption and release of tremendous amounts of energy. The poster was not trying to say that the compressor was not wasting any energy as heat/noise/vibration.
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 amount of energy will then increase that same gram of water from 32F to 176F.

Re:Peltiers

[Anonymous Coward]

Different news paper same type of content.
Deseret News Article

Re:"can't tell"?

[GrpA]

>>No one notices a few Kilowatts disappearing. >>Except ricers. >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). That's because you're a ricer - I can tell from your response ;) (Tongue in cheek) Heh. Don't take that seriously. I'm not trying to start a flame war. And I apologise if you took exception to my generalisation. I'm quite familiar with HP and power ratings. AFAIK, the compressors are most efficient at low RPM, when there is plenty of torque available, so the effect would be even less.... However, for the sake of a quick post to an audience in which probably only about 1% of readers understand the relationship between torque, power and rpm, I thought I'd simplify. As for my experience and background with cars? Have a close look at my alias. GrpA.

Re:Peltiers

[InvalidError]

Cooling efficiency is expressed with the "Coefficient of Performance" (COP), and is the ratio of displaced energy and input energy.

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 these optimal constraints, their COP quickly drops under five. So, to produce a highly efficient TEC AC able to handle 1000W, one would need a 1kW TEC bank operated at ~80W. Considering that a TEC costs about $0.25 per rated watt, this efficient solution would cost over $250, roughly twice the price of an average room AC... and it gets worse: 1kW is barely enough to cool one square meter worth of solar heating, car and house windows have a much larger surface area total than that.

Note: a TEC's 100% rating is where the TEC barely manages to pump its own heat away from the cold side. TECs used for thermal regulation usually operate in the 30-50% range. The high-efficiency range is usually somewhere around 5% with COPs sometimes reaching over 15. For comparison, the theoretical limit for freon (and many substitutes) is around 16 but the best practical implementations only reach around 12.

Now, a typical room AC pumps from 5kW to 12kW with a temperature delta around 20C with a COP around 10. So, to beat the phase-change system's efficiency, the TEC solution would have to be beefed up by about 20X (10X the load, 2X the delta), bringing the cost around $5k, which is 20X as expensive as good classic AC.

Until they find materials that offer both better electrical conductivity and better thermal insulation to improve their overall performance (widen their sweet spot and move it up the power curve), TECs will remain a somewhat marginal cooling solution.

Re:/.ed

[Charcharodon]

Don't see how it is going to "save" fuel since taping into the electrical system puts a load all the same on the engine. Instead of the AC/pump getting the load the Alternator does.

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 connected directly to the engine. So if 1-5 broke you might not even notice.

Re:/.ed

[AaronLawrence]

Except for one tiny details: they are not. They are an order of magnitude LESS efficient at moving heat.

Let's not let facts get in the way of a good story though.

Re:/.ed

[Hadlock]

I don't know if you've ever worked on a car, but if you know what you're doing, you can change an alternator in about 20 minutes, or get it replaced at the dealership for $150. It costs that much to have someone look at your A/C system, let alone work on it. The A/C system truly has no user serviceable parts.

Re:/.ed

[rogerzilla]

Except that car alternators are surprisingly efficient - up to 90%. In fact, if it wasn't for the power supply difficulties (a typical 4kW unit would draw 333A at 12V), electrically-powered car a/c would have a huge advantage - it doesn't need expensive servicing every 2 years because there are no shaft seals open to the outside, hence no refrigerant leakage.

Domestic fridges are the most reliable applicances in the home because they are built as a completely sealed unit.

Re:Peltiers

[Abm0raz]

I'm sure you meant C(oeffecient) O(f) P(erformance) and NOT efficency.

COP is defined as HEAT_RATE_REMOVED_FROM_COLD_RESEVIOR/WORK_RATE_REQ 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 level of the high heat resevoir. This value can exceed unity (1) and generally ranges from 2-5.

Efficiency of the heat pump or refridgerator is defined as USEFUL_WORK_PRODUCED/ENERGY_REQUIRED. For a refridgerator, this is written as Q(L)/W(in). Since Q(L) for a no-loss system is defined as Q(L)==Q(H)-W(in)** Through some equation manipulations shown on page 7-24 of the referenced book(see end of post) it's shown that Q(L)/Q(H) = T(L)/T(H) and that the efficency is defined as 1-T(L)/T(H) and that this value is always less than one as by definition of T(H) > T(L).

Appendices:
Source: Thermal-Fluid Sciences: An Integrated Approach 3rd ed, Dr. Stephen R. Turns Ph.D., 2003, Published by the Pennsylvania State Universit Department of Mechanical & Nuclear Engineering.

A heat pump/refridgerator is defined as a high temp resevior and a low temp resevior sufficently large that any instantanious heat added or subtracted by the system will not significantly affect their temperature. Between these reseviors is a pump that moves heat from the low temp to the high temp by performing work on the system. It receives the energy to perform the work from outside the system. The second law of thermodynamics*** says that because the natural entropy of the system would be an equalized temperature between the reseviors, the energy required to move heat the other direction must be greater than the actual energy moved (thus the efficency can never be greater than 1).

Q(dot)[L] => Rate heat is removed from low temp resevior
Q(dot)[H} => Rate heat is added to high temp resevior
W(dot)[pump] => Rate work is used by the pump
Q(L} => Heat removed low temp resevior
Q(H) => Heat added to high temp resevior
T(L) => Absolute temperature of the low temp resevior
T(H) => Absolute temperature of the high temp resevior
W(in) => Work required by the pump

* Absolute scale can be either Kelvin, Rankine, or any other linear proprietary temperature scale where there is no negative temp and that sets its lowest temperature at the temperature at which all molecular movbement stops (absolute zero)

** There is no such thing as a no-loss engine in real life. There will always be friction, drag, and/or head loss (for turbine/pump/fan driven air conditioners) or electrical resistance (for things such as peltier coolers). So the real equations is: Q(L)==Q(H)-W(in)-W(loss) where W(loss) is the total work lost overcoming internal forces such as drag, resitances, etc..) That W(loss) makes the maximum heat removed from the low temp resevior even less, thereby reducing the efficiency.

*** Among other things, it says: "Work can be converted entirely into heat. Heat cannot be converted entirely into work."

-Ab

ps. "Lisa, in this house, we obey the laws of thermodynamics!" -Homer Simpson

Re:/.ed

[Lumpy]

Those numbers are skewed. Today's cars use more gas at highway speeds if only one window is down compared to the air conditioning. Hell the econobox I bought to beat gas prices loses only 1mpg when the AC is on (based on using a tankfull of gas. Comparing a month of commuting in cooler weather with only fan and vents open compared to the tankfull used when the AC was on full blast non stop.)

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

[crath]

But Google's cache does have a copy.

A few points

[Muad'Dave]

• As has been mentioned, this isn't exactly a new invention or particularly innovative. As we've all seen from the patent office's behavior, something can be seen as innovative and blindingly obvious at the same time.
• Many posters have commented on the amount of power needed to run Peltier's - remember that in the not-too-distant future cars will have 48-52V electrical systems with alternators capable of much higher power output. Car's electrical systems are already taxed given the recent proliferation of nav systems, DVD players, laptop power outlets, etc., so the move to more powerful electrical systems is underway.

  Here are a few of the things that become possible with that kind of available power:

  1. Engines with electrically-actuated valve trains - no more camshaft, timing belt, rocker arms, pushrods, etc.
  2. Electrically powered power steering (as is done on my Mini Cooper S), eliminating that belt.
  3. Electrically powered A/C system
  4. The alternator either integrated in the block, or bolted directly to the crank. Imagine that - an engine with no belts!

• Wouldn't it be interesting to develop a cooling element that combined the Peltier effect and the Piezoelectric effect? Anchor one end and let the other flap, apply pulsed DC to it and you get cooling and a fan!

Re:/.ed

[BillyZ]

Those numbers are skewed. Today's cars use more gas at highway speeds if only one window is down compared to the air conditioning.

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

[Digital Vomit]

Today's cars use more gas at highway speeds if only one window is down compared to the air conditioning.

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.

Mythbusters

[Steve_Jobs_HNIC]

Today's cars use more gas at highway speeds if only one window is down compared to the air conditioning.

Yeap, Mythbusters did prove this theory wrong. 2 SUV's were loaded up with 5 Gallons of gas and driven around the track. One had the AC on and windows rolled up, the other had the AC off and windows rolled down. If I'm not mistaken, The first test was inconclusive. However, the next test I believe proved this theory wrong. They decided to fully gas up the SUV's instead of trying to accurately measure and fill up only 5 Gallons. The test showed (and I'm not sure on these numbers) somewhere around a 5% to 10% loss of MPG on the AC SUV. While the AC SUV had to pull over, the windowed SUV kept on trucking!! So yeah, they busted that myth.

Re:Mythbusters

[Suidae]

The initial test was done by reading the output of one of SUVs on-board computers to determine how much air the engine was using. This test was done at 55MPH with windows up and AC on, and with windows down and AC off. The data indicated that the vehicle used slighly less air, and therefore less fuel, with the windows up and the AC on.

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 this because of concern over tire failure (and possible subsequent vehicle rollover) and possible driver fatigue (maintaining the concentration required to handle the vehicle for the 6-8 hours required for the test would be difficult). Instead the test was run at 45MPH with 5 gallons of fuel.

The power required by the AC on full is constant regardless of the engine speed. The effect of drag on the vehicle is dependent on the speed, and the nearly 20% reduction in speed may have eliminated the slight difference seen in the first test.

Also, the fuel was removed from the vehicles using a hand pump, and it was not shown that any effort was made to clear the fuel from the in-tank pump all the way to the fuel rail in the engine. It is possible that the two vehicles did not have the same amount of fuel.

They did not show that other conditions where checked, such as identical engine parameters (the computers in modern vehicles tune themselves depending on how they are driven, if the two SUVs were driven before the test they might have had different computer parameters, resulting in different fuel consumption rates).

In short, the experiment was very rough, and had little in the way of controls. It is likely that at low speeds it is better to have the windows down, and at high speeds it is better to have them up. Also, it is unlikely that the AC would be run at MAX the entire time, so there would be fuel savings there as well.

The episode was entertaining, and did mostly answer the question "Would a big SUV use more fuel driving at 45mph with the windows open and AC off, or with windows closed and driver shivering under continious MAX AC?"

To test more accurately would have required several trials of the same vehicle at several different speeds with an accurate flow meter on the fuel lines (both delivery and return lines). Throttle position at all times would have to be carefully controlled to avoid any serious variations in computer tuning. Trials would ideally be run in two opposite directions, similar to how land speed records are controlled.

Re:/.ed

[nuxx]

Did you note that the also ran the vehicles at 45MPH?

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

[ebh]

That's not too bad of a mechanical problem, but the real danger of higher voltages in the engine compartment is sparks.

Because of the huge demand for current in modern cars (when's the last time you saw a window crank?), the automakers are trying to move to a 42V electrical system, but they're having a hard time bringing down the costs of all those gas-tight connectors, not to mention devising safe procedures for jump-starts etc.

Re:/.ed

[jazzkat]

Completely false. This statement is a common urban legend, and nothing more.

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 to take into account.)

Care to back up your assertion with some facts?

Re:/.ed

[silicon not in the v]

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!)

I watched that episode of Mythbusters about the A/C vs. open windows debate, and their conclusion was that it was pretty close to even. Their test results could barely find a difference, but their testing methods were so horrible(as in not real life) that I found any conclusion they would come to worthless. The biggest aspect that screwed up their results was that the identical vehicles they were using were both huge SUVs with V-8 engines. Of course an A/C compressor isn't going to be much of a load(proportionally) on that powerful of an engine.

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

[sirket]

That was one of the less intelligent bits of testing they have done on that show and some of their test rigs have been doozies. Let's list some of the problems:

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

New AC

[Trtle_Nuts]

What's funny is that people actually believe that the auto industry in the United States will allow such a deep cut in the amount that Americans pay for gas. They want us to be as dependent on "gas" as is humanly possible. They went so far as to ignore the PHEV,(http://www.energine.com/eng/engine/engine2.h tm), developed by a South Korean company because it would have eliminated the need for gas.(They,U.S. automakers, asked if it could be modified to be a "dual" system using both air and petrolium) It just goes to show that when it comes to saving the environment, the automakers are not interested if it affects the amount of revenue they get from selling gas. Anyone who believes that the automakers will allow the use of anything in a vehicle that lowers our consumption of gas, (in this lifetime), is delusional, at best.

Re:/.ed

[dbIII]

I don't know where you get the idea that it doesn't take a lot of energy to compress the gas down in the first place (which you have to do to get it to release the heat)

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 all moving before the expansion nozzle.

compressing the air you want cooled, running it through cooling fins, then expanding the air and releasing it.

It's a lot easier to compress the working fluid/gas, run it through a cooling system (for example the exposed copper piping with a big surface area on the back of old refridgerators), then expand it. Gasses that we can do this to easily are the ones that are used as the working fluid - with air it's a lot of hard work to get the CO2 out so you don't get solids and then compress the nitrogen down to a liquid. It's far easier to cool something else and blow the air past it than to compress and expand nitrogen.