# Ice Maker for Air Conditioning



## jaspersk (Jun 26, 2008)

This my first post. I have a 95 Jetta and a Zilla on order in the queue. Right now, I am still driving the Jetta as an ICE and working on getting it ready for conversion. On of my first steps towards the conversion is to dream up a plan for air conditioning. The current system doesn't work so I am sweating on my way home for work. Otherwise, I'd work on something easier like manual steering or electric vacuum. Rather than fix it, I'd like to think of something that might work for an eventually EV.

Here is my idea. I am thinking about purchasing one of those counter top ice makers, and a small dc pump. I would drop a small heat exchanger or coil in the bottom of the icemaker and have antifreeze pumped from it to the coil in the air conditioning duct. The theory is that when the car is plugged in to 120V, it makes ice. Once you unplug and drive the ice is used for cooling and the DC pump circulates it to the air cond vent. Obviously, it will only work until the ice melts, but it seems like a good fit for an EV. I don't own one of these icemakers but my understanding is that once the ice melts, the water goes back into the water tank. My thinking is that I would adjust the drain so that the coil would always be soaking in ice water but at the right height the water would drain back into the water tank, thus it would be always recycling and not need to have water added.


These guys have something similar but I don't want to have to add ice everyday. Based on their claim for the amount of ice required versus the time their unit works, it would seem to me that a small icemaker would be sufficient for a 20 mile drive.

http://www.swampy.net/auto-air-conditioner.html

Thoughts?


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## TX_Dj (Jul 25, 2008)

I see a few issues with this:

1) automatic ice makers require a pressurized water supply connected so they can do their thing. Unless you've found one that makes ice from water poured into a resevoir.

2) the ice will begin to melt very quickly once the coolant loop starts passing thru the "tray", necessitating a large amount of ice depending on how hot it gets where you are

3) most ice makers that produce enough ice in 8 hours to fill the tray with enough ice to last you during a drive will be huge, heavy, and expensive. It takes a long time to make ice.

Great outside-the-box thinking.


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## jaspersk (Jun 26, 2008)

Most of the counter top ice makers do not require a water supply. They have a tank that you fill with water.

The makers of the swampy say that 20 lbs of ice is equivalent to a 5000-8000 btu air conditioner for 1 hour. Most of the portable ice makers store 2.5 lbs of ice. I suppose that means it would only be good for 10 minutes so you might have a point. I have considered a small freezer that would make a solid block of ice but I am not sure how to handle the expansion and contraction. I am sure it is possible but probably not with hobby skills. Maybe I could modify an icemaker to use a larger tank?

The portable ice makers claim them make ice in 7 minutes at a rate of 1 1/2 lbs/hour so I think it could do it.


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## O'Zeeke (Mar 9, 2008)

I made one of these http://www.instructables.com/id/Portable-12V-Air-Conditioner---Cheap-and-easy%21/ for about $50 and it works great. True, it is a pain to add ice but sure beats the heat and does not decrease my range


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## ww321q (Mar 28, 2008)

I was thinking about the same thing but using ice packs instead of ice . when you got to work just throw them in the freezer . J.W.


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## TX_Dj (Jul 25, 2008)

I wonder how much cooler it would run with salt water 

I don't think 52 degrees air output would do much but take the very edge off, climbing into a 130+ degree car in TX heat.


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## dtbaker (Jan 5, 2008)

how about just putting the coil in the back of the driver's seat and go for direct cooling of your back/seat? or, maybe stick it in the fan duct where lots of people insert the optional electric heater core?


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## xrotaryguy (Jul 26, 2007)

Do you have a link to the ice maker you are considering?

Using ice to cool an EV with a 30 mile range is an excellent idea. The specific heat of water is so stinking high that it would work very well. Also, the system does not take any energy from the battery pack other than to pump coolant through the heat exchangers and to blow air over one of them.

I have considered a few systems that would use a portable refrigerator or electric ice chest type unit to freeze water. The freezer that I've been looking at is this one. The thing is a bit spendy, but look at how well it cools! It can cool the inside temperature to 10 deg F in only 1 hour. It can get the temps down to 2 deg F in only 2 hours. Killer. 

Other less-expensive electric-ice-chest-type devices only claim to cool down to perhaps 40 or 50 degrees below ambient, so when the outside temperature is 140 degrees F inside your car, the ice chest will only cool to 90 degrees F. That's not going to do anyone any good.


I don't really think that salt water is necessary. The important thing is to get the water into the solid phase so that it will remain at 32 deg F until all the ice is gone. If you've got a bunch of water in the cooler, then that water is going to be constantly changing temperature. You can cool solid water to what ever temperature you want, so there is really no advantage to adding salt to the mixture.

52 degrees F is very good for an AC system. My house puts out about 55 deg F and we can run at 75 deg F inside the house when it's 115 F outside. I don't like to do that because it's expensive and irresponsible, but it can be done.

More Ideas:

Use an electric ice chest that has several rectangular blue ice packs inside it and simply blow air through the ice chest. This is not as neat as using a heat exchanger, but it would work. Also, you can buy a fan that is specifically designed to fit the top of an ice chest from this site, so that makes things easier. Heck, you could simply set something like this in your back seat and have it plugged in / paralleled into your charger's 110v supply.

Another idea is to use an electric ice chest with blue ice packs in it and have those packs submerged in antifreeze and water. The system would also have a heat exchanger submerged in it. I'm sure you can figure out how the rest of the system works. The benefit here is that you do not have to worry about the antifreeze turning solid, so you don't have expansion and contraction problems.


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## aeroscott (Jan 5, 2008)

ice is heavier then batteries / ac .


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## xrotaryguy (Jul 26, 2007)

Do you mean that water has a poorer energy/mass density or that it has a lesser energy/volume density...? On what do you base this statement?


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## chamilun (Jun 17, 2008)

http://www.swampy.net/wb.html

this one requires ice?


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## TX_Dj (Jul 25, 2008)

xrotaryguy - You obviously know a lot about this, but dismiss my suggestion of salt water.

I don't know a whole lot about this, but base my suggestion of salt water from the Mythbusters episode where they are trying to get a cooler full of warm beer coldest fastest, and ice in salt water provided the fastest cooling with the lowest temperature. 

Fact of the matter is, if you put something that's room temp in a freezer, it will take about 20-30 minutes to bring it near freezing temps. If you put it in a bucket of ice, it will take about 10-15 minutes, if you put it in a bucket of ice water, it will take about 5-8 minutes. But if you put it in a bucket of ice filled with salt water, it will take about 2 minutes.

One thing I do know- your car's AC is putting out near-freezing air, as this is what's required to effectively chill an airspace such as the cabin or your home. Salt water is a little heavier than regular water (depending on it's SG of course) and if the correct amount of salt in the water will increase the efficiencies of the cooling apparatus, then why not.

Of course... because once you add ice to the salt water, and that ice melts, the SG of the solution changes, and one would have to muck about with the salinity to maintain efficiency. 

Hrm.


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## jaspersk (Jun 26, 2008)

xrotaryguy said:


> Do you have a link to the ice maker you are considering?
> 
> The freezer that I've been looking at is this one. The thing is a bit spendy, but look at how well it cools! It can cool the inside temperature to 10 deg F in only 1 hour. It can get the temps down to 2 deg F in only 2 hours. Killer.
> 
> ...


I really like the small freezer that you posted. I have been googling around and the best I could come up with was a small medical freezer but it was upright. Having something very small in a chest configuration would be PERFECT! And the freezing capability looks impressive. I wish there was a way to get something with lower cost. I feel like it should be possible to make something like this with leftover parts of a small chest freezer but I am not sure how ambitious I am willing to be.

I don't have a specific ice maker in mind. Seems like there are a lot of them out there like this one. 

http://www.homedepot.com/webapp/wcs...d=10053&productId=100597200&categoryID=501898

Trouble is I can't tell if they only make ice or if they store it too. I think your idea of being able to make one solid block would be most efficient in terms of volume versus capacity.

I agree that salt water would not be necessary. Regardless of freezing point, I think it would be important to go through the freezing process since that takes a lot of energy (more than just taking the temperature down) and would allow you to store more cooling capacity for the same volume. That said, salt wouldn't hurt as long as it didn't take the freezing point below the capability of your freezer to make a solid. Our local liquor store has a bucket for flash cooling bottles of wine. I think it is the same concept as mythbusters but rather than lower the freezing point by adding salt, they keep the water continuously moving so it can't freeze.

I am guessing that blowing over cooling packs wouldn't work. On the swampy site they talk about why blowing air over ice doesn't work so I wouldn't think this would be much better.

These are great ideas. I really appreciate everyone's help.


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## jaspersk (Jun 26, 2008)

I am going to take back what I said about salt not being a lot of help.

I have been researching holdover or holding plates. These are devices which are designed to do just exactly what we have talked about. They freeze a material while plugged in so that cooling is present for a long period of time after being unplugged. They are targeted for delivery trucks but even more so for boats. The following link talks about how they use a "salt brine solution" to store cooling energy as a "big ice cube."

http://refrigeratedtrans.com/mag/transportation_power_plates/
http://www.marinespecialists.com/marineairsystems/manuals/grunert_holdover_plate/index.htm

Unfortunately, holdover plates look even more expensive then buying $300 freezer but it validates the concept.


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## TX_Dj (Jul 25, 2008)

jasper,

I did some more research on the salt-water/ice combo myself, and what I came up with falls in line with the statements that others made in this thread.

The salt water has a lower specific heat than pure water, thus it will not "retain" the cool temperature as long as pure water, but what it does do is reduce the freezing point of the mixture. When this happens, the ice starts to melt faster, but this is due to the lower freezing point. It seems a little counter intuitive, but the freezing point of salt water is about 1.9C less than water (so -1.9C) and because of this, it causes the ice to melt... but as a process of this melting, the cooling ability is slightly increased. Like I said, seems a little counter intuitive... but that's more or less how it works.

So, if you cool salt water or heat salt water, it will take less energy to do so (less specific heat) but at the same time it will not keep cool or hot as long as pure water.

Since most of us have a limited range in our EVs, the more rapid cooling of the salt water may increase the immediate efficiency of the cooler, but will also decrease the "run time".

As with anything, I guess, there's always a trade off. Now, if the difference is 10 minutes to freezing temps vs. 5 minutes to freezing temps and 45 minutes of cooling vs. 30 minutes of cooling, I'll take the salt... but those are numbers I just pulled out of thin air...

I'm definitely intrigued by the thought of the ice-water cooler, especially since we have a high-volume icemaker in the office and I don't use much of the ice that my freezer at home makes... But still wonder if it would be sufficient to cool my conversion for the duration of its maximum charge. And also wonder how one could economically maintain the optimum salinity (too much salt != better performance) unless the saltwater were physically separated from the ice, in which case it probably would not be nearly as efficient. 

I guess it's time to go buy a cheap cooler and some parts and see what I can come up with. If this design will yield adequate cooling in my ICE truck (har, no pun intended) on our hottest days and my longest trips, then I'm sold for ice cooling the EV.


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## piotrsko (Dec 9, 2007)

another moldy oldy from the past:

195X series Beechcraft Bonanza's ( A or B models) had a plenum on the celiing bulkhead that had a pan for filling with ice cubes. prop blast or forward airspeed powered it until the ice melted or you were at altitude. Maybe 20 minutes? If it was 100 outside, the cabin was probably 80 ish with a evaporation cooling effect out here in the west. Pan size was approx the size of a cube tray from a modern 'fridge icemaker.


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## morvolts (Jun 19, 2008)

TX_Dj said:


> jasper,
> 
> I did some more research on the salt-water/ice combo myself, and what I came up with falls in line with the statements that others made in this thread.
> 
> ...


 BTUs is BTUs
Brine solutions wont change the BTU content.Ice may melt quicker because its giving off BTUs at a higher rate.


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## jaspersk (Jun 26, 2008)

morvolts said:


> BTUs is BTUs
> Brine solutions wont change the BTU content.Ice may melt quicker because its giving off BTUs at a higher rate.


You are correct. There is some pretty good information on the web about why holdover plates need a true Eutectic solution. It is my understanding that the brine is used to set the temperature that you would like the setup to work at. For instance, if you want to operate a freezer, they suggest a holdover plate that freezes at 0 deg F. If you want a refrigerator, they suggest a plate that freezes at 26 deg F. 

This link has a pretty good explanation.

http://www.setsail.com/products/oce/refrigeration.html


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## Astronomer (Aug 7, 2008)

Dj's research is spot on, but the fact that salt water melts at a lower temperature than plain water is not really an indication that it is melting faster. The only reason to use salt water is if you want to maintain a temperature at a point below freezing, such as when making ice cream, or transporting fudgecicles to the beach in a cooler. A lot of people think salt makes ice colder, but it doesn't. It just lowers the melting point of water. So there's no reason to use salt in an A/C application for human comfort, since it won't absorb more heat than water. 

The reason for using ice ice as a heat reservoir in the first place is to take advantage of the latent heat exchange during phase change. Heat is manifested in more ways than just temperature. Once the ice reaches 32 degrees (F), adding more heat causes it to melt, but not raise its temperature. So as the ice absorbe heat, it liquifies, but it doesn't get any hotter as measured by a thermometer. So as the ice melts, it stays at a constant temperature, even though it's absorbing heat. How cool is that? (Yeah, I know: About 32 degrees. ) 

This is a good thing, because it means that during the entire phase change period -- which can last as long as your ice bucket is big -- you maintain a constant temperature of the reservoir, so the air blowing across the water is as cold when that very last bit of ice melts as it was in the morning when it was a solid block of ice. 

But once the water liquifies, the dumping more heat into it will quickly raise its temperature, and the air blowing out your A/C vent will become increasingly warmer. 

There are materials with higher heat capacities, but that won't work as well. For instance, if you were to use a cold block of iron, you could dump far more total heat into it than into the same size block of ice at the same temperature. But the temperature of the iron would begin to rise immediately, making heat exchange increasingly difficult. Your A/C will blow noticeably warmer air almost immediately. You'll be able to dump more heat into the iron, but it will be at a (mostly) higher temperature. 

The only problem I see with using ice for A/C is for commuting. A block of ice will keep me cool an my way to wor just fine. But while I'm in my little cubicle, my car is sitting in the hot Texas sun for at least nine hours. Will there be any ice left to get me home in comfort at the end of the day? 

It sounds like it's time for an experiment!


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## TX_Dj (Jul 25, 2008)

Exactly, Astronomer!  I loves me some experiments.

More or less, the only reason I was considering salt/brine solution was because I had read that it can drop a temp faster, and any of us who climb into a real hot car and turn on the AC want the temp to drop as fast as possible.

I expected the trade off to be a shorter "run time" for cooling, but if it's significantly shorter, and/or if the cool-down time of pure ice-water vs ice-salt-water is insignificant, then it surely does not make sense to run the salt. Especially once you consider the ice will change the overall salinity of the whole once it has melted into the salt water, requiring some crafty equalization to get that SG back to "optimal"...

As for the ice during hte heat, I'd expect my ice to be melted by the time I got to the office... but the office has a large ice maker.

As such, I'd expect I could draing the "AC" cooler once arriving at the office, and have another equivalent sized container I can bring into the office and create a fresh ice-water load for the drive home.

Things that make you go HMMMM!


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