Build a performant DIY portable air conditioner (ICE POWERED)

[MisterHeadache]

The effect of the humidity of the room air cannot be minimized.  It's been a few decades since I did these calculations in MechEng thermodynamics classes, but I do remember the basics of using what's called a 'psychrometric chart'.  Look it up and how to use it.  Once you cool the room air to its dew point (meaning 100% relative humidity), a big portion of the energy required to cool it further is just consumed to condense the humidity out of the air as you cool it further.  For example: if you start with a room with 80°F air at 80% humidity, your efforts to cool it will drop the air temperature and raise the relative humidity until you hit 100% relative humidity at its dew point (73.3°F).  Cooling it further begins condensation and now a significant portion of the energy transfered is condensing water, not just cooling the air further.  So that's kind of an efficiency loss - some of the energy you'd like to use productively (reducing the room temperature) is 'lost' in just making condensed water that you don't value.

If you start with drier air at a very low relative humidity (Arizona for example), you can cool it to a much lower air temperature with the same available energy because you won't be condensing hardly any water from it.

[IanB]

The balance with humidity is the perceived air temperature and comfort levels. If the room air is dehumidified, even at the same temperature, then the occupants may feel more comfortable because skin perspiration becomes more effective. So cooling power used to dehumidify the air is not necessarily wasted.

[YouCanDoIt]

Please read again this post:

https://www.eevblog.com/forum/projects/i-need-to-connect-a-100mm-dryer-flexible-vent-hose-to-a-102mm-pipe/msg5592019/#msg5592019

Temperature is not an important factor in performance. Colder is not necessarily better.

Yes, I have done and invite you to read my response along with the posted comment from the guy that regularly build such kind of devices. He states the exact contrary and he do this in every project he publish on youtube.
I think that we agree on the two following points:

• The lower is the temperature of the water inside the cold reservoir, the longer will take heat to melt ice packs
• The lower is the temperature of the water inside the cold reservoir, the lower will be the temperature of the airflow released into the the room resulting in faster cooling times and higher chances to bring room temperature down

When you say that temperature is not an important factor in performance and colder is not necessarily better, you probably mean that a colder temperature could generate moisture issues and you're perfectly right.
However, as I already said to ebastier,  I prefer water near to 0C° plus condensation issues to fix rather than hotter water without any condensation issues.

A portable ice air cooler can never, under any circumstances, cool a room down like an electric room air conditioner.

A portable ice air cooler can never, under any circumstances, cool a room down like an electric room air conditioner.

And I told you that water can never go below 0°C or it will freeze. If it is ice, you obviously cannot pump it through a radiator. This is not a recommendation. It is a law of physics.

Well, you can add antifreeze to water but reading this thread I think the best advice is the first phrase " A portable ice air cooler can never, under any circumstances, cool a room down like an electric room air conditioner.".

Seeing this type of projects I get the feeling that the people doing them just do not understand the basic laws of physics and believe they can find   work around them.

In the summer heat it is the "put some cubes of ice from the refrigerator in front of a fan" and in the winter cold it is the "put a burning candle under an up side down clay pot to heat all your house".  Or the "ceramic electric heaters".

If this is not possible and under any circumstances, then the "guy is lying":


Or, more simply, it depends from how well the system is designed. I exclude the small room size as a mandatory requirement just because a bigger room requires a bigger system.

My main concern is about health safety. the word Propylene glycol does not feel safe at all and I am not sure on the consequences for health if it get released into the room through the cold air.

Propylene glycol is another cheapish option 40% glycol/ 60% water  gets you down to around -20C
guess what they use in the beer coolers ?and It dont  seem to affect the 100000's of beer drinkers  supping  chilled and super chilled pints,

And I told you that water can never go below 0°C or it will freeze. If it is ice, you obviously cannot pump it through a radiator. This is not a recommendation. It is a law of physics.

This is a great news! However, IanB can correct me if I'm wrong, this can't work in any way. A -20C temp drops will bring water below zero. It can only work if the water temperature is around 25C, but the ice packs alone will bring temp much down than that.
What makes me suspicious about this solution is:
why no one has ever attempted to replace ice packs with Propylene glycol? It would be much less hassle and the system would be truly portable because without relying on ice it can work literally in any place.

If I remember well, I have read that antifreeze is dangerous for health. You're probably right when you say that most people don't understand the basic law of the physics. Given that such laws can't be bypassed and that guy achieved the goal, I suppose he just designed the system to use the physics law in the right way. I don't know how compares with a regular AC, but it is not certainly at the same level. However with a 10-20C temperature decrease I would consider this more than satisfying.

[ebastler]

why no one has ever attempted to replace ice packs with Propylene glycol? It would be much less hassle and the system would be truly portable because without relying on ice it can work literally in any place.

You may be mixing up two things here? Propylene glycol does not magically get cold on its own. It is just a liquid with a lower freezing (or melting) temperature than water.

The total cooling capacity of your system (i.e how much total heat energy it can "extract" from a room) is determined by the total energy it takes to melt the ice blocks you put in. Whether the heat transfer happens through slightly warmer or colder water (or some other liquid) may impact how long it takes to melt the ice.

I think that we agree on the two following points:

• The lower is the temperature of the water inside the cold reservoir, the longer will take heat to melt ice packs
• The lower is the temperature of the water inside the cold reservoir, the lower will be the temperature of the airflow released into the the room resulting in faster cooling times and higher chances to bring room temperature down

No, we can't agree on that. Those two points are actually contradictory. If it takes longer to melt the ice packs, then heat from the room is transferred to the ice packs less efficiently. So it will take longer to cool the room down.

Edit: Typo

[Siwastaja]

The effect of the humidity of the room air cannot be minimized.  It's been a few decades since I did these calculations in MechEng thermodynamics classes, but I do remember the basics of using what's called a 'psychrometric chart'.  Look it up and how to use it.  Once you cool the room air to its dew point (meaning 100% relative humidity), a big portion of the energy required to cool it further is just consumed to condense the humidity out of the air as you cool it further.

This is technically correct, but maybe a bit misleading: you would not gradually cool the room towards dew point and then start drying. This would happen with infinite air flow over ideal (infinite performance) evaporator coil.

Realistically, any air conditioning solution would keep the indoor unit coil temperature significantly below target room temperature, in other words, air flow modest and not excessive, so that humidity is continuously removed from the beginning, and this cold (absolutely quite dry even if 100% RH) air mixes with the warmer room air, gradually bringing both temperature and absolute humidity down at the same time.

[Siwastaja]

Propylene glycol [...] is just a liquid with a lower freezing (or melting) temperature than water.

Yeah, and to be super clear, this is exactly what we do NOT want. We do NOT want prevent the storage medium from freezing. Solid<->liquid transition is exactly what stores a lot of energy in relatively little weight. If you prevent freezing by using antifreeze such as glycol, you would need many hundreds of liters of it to have any effect at all.

Sure, freezing is a bit of problematic transition because it physically breaks stuff due to how the volume changes quite violently (it can crack rocks), but any even remotely portable solution has to deal with this.

[Siwastaja]

It is interesting that ice-as-energy-storage does make sense in some circumstances, and is used in practice. For example, ice-based air conditioning systems for large buildings, in places where electricity is cheaper at night.

I have been playing with this idea of taking an commercial off-the-shelf ice cube maker - maybe a professional higher throughput version, something being used at McDonalds and the like, something with serious continuous power rating. They already solve all the hard engineering work of not only making the ice, but separating it from the evaporator coils without damaging anything. Run during cheap electricity (nighttime, or maybe solar panel self-use), store the cubes in large insulated styrofoam/etc. boxes. Replace box lid with a fan unit which blows air over the ice, and voila. As long as there is ice in the mix, the water surface keeps close to 0degC and thus it keeps dehumidifying. Extracted humidity ends up mixing with the melting water, but so what. Once melted, you swap boxes.

For this to become an actual product, we really would need to combine the outdoor unit of a split air conditioner, with the ice cube maker (evaporator only) working as the indoor unit, and then automate the mechanics of moving around the ice cubes.

Water could be reused a few times, but probably for sanitary reasons simpler and safer to use fresh water every time - ice cube makers already have solenoid valve controlled water input so most of the engineering is already done.

[YouCanDoIt]

Are you saying that the styrofoam box is the wrong material for the processing unit? Or that I should leave all of the parts exposed?
Well, mainly because styrofoam is cheap and good for insulation. Without a container it would be a much more complicated mechanical construction and the related parts more easily exposed to possible damages. Also, the radiator will be more subject to condensation which, from what I have been told, is something we want to avoid like pest.

What do you want to insulate there? You want cold air to be released into the room. You had shared a video (in your other thread, I believe) of a fan blowing towards a radiator simply placed in the open -- what's wrong with that from a thermal perspective? You just need to add basic mechanical protection, i.e. a wire mesh cage or such, to ensure that the radiator is not damaged and the user's fingers are not hurt by the fan.

Also, I don't see how the styrofoam box would prevent or reduce condensation on the radiator. You are blowing warm air at the radiator, which will get cooled down there and hence can't hold as much moisture, so you will get condensation.

The purpose of the carbon/Hepa filter on the air inlet is removing contaminants from the room. Contaminants get stuck into the filters and cold air is released into the room clean.
The goal here is not avoiding the introduction of new contaminants into the room, but eliminating the existing ones.

We used to run a mobile air filtration unit when our son was little and struggling with allergies. It had a HEPA filter with a much larger surface area. The small filter you plan for will clog quickly, and will make your unit noisier and/or less effective due to restricted air flow.

Well, under the thermal prospective I initially thought that would help to keep the unit colder. I suppose it should make difference between hot air penetrating through an air intake vs all the parts exposed to the room hot air.
Then, IanB pointed out what you're trying to say, but there are still many other issues other than a more complicated mechanical construction (inside there is not only the radiator to protect and the number of parts you see in the diagram can increase if the processing unit is enhanced with more features). I don't even want to think on how this reduce portability since this is not my main concern (but something that for sure plays against such design).

I think you refer to this video. This, along with many other I saw, seems to be not able to cool a room. They're more like "fans pushing gentle fresh air against a reduce area". I preferred to go with a design that has been proven to work and being free from issues I described in details with screenshots in this thread.

I think you're right when you say that styrofoam box does not prevent or reduce condensation on the radiator and I suspect styrofoam material could even be counterproductive.
IanB can correct me if I'm wrong, but instead to prevent heat introduction inside the processing unit through styrofoam we want a material that does the exact opposite.

Your observations about the air filtering are well motivated. I have no idea on how much filters can last, but given that the guy didn't mentioned anything about duration, I suppose they work for acceptable times. I have a regular AC in another floor of the home and they needs to be replaced once a year, but I really don't care if I have to replace once a week. Replacement only takes a couple of seconds, the sheets are very cheap and provides plenty of filters.
However, I'm attempting to perform a nearly full room cleaning through a two layers Carbon/Hepa combo which is different. I guess I will have to do many trials before I find the right balance (number of holes, their diameters etc). At worse I can always fallback to the same 3M filters used by the guy. These, at least, are proven to work without any interference.

[ebastler]

I think you refer to this video. This, along with many other I saw, seems to be not able to cool a room. They're more like "fans pushing gentle fresh air against a reduce area". I preferred to go with a design that has been proven to work and being free from issues I described in details with screenshots in this thread.

Maybe a quick estimate can be helpful:

A typical self-contained air conditioner based on a heat pump (those small vertical units on wheels) has a cooling power of 2.5 kW under ideal conditions. That's 9000 kJ per hour.

A kg of water takes 333 kJ to melt, and another 120 kJ to heat by 30 °C (say from -15 to +15°C). Hence the effect of heating and melting a gallon-sized ice block (4 kg) will be equivalent to running that small air conditioner for 12 minutes. Underwhelming, isn't it?

(This estimate is not discussing how fast you can extract heat from the room. It just estimates how much heat you can extract until all the ice has been melted and warmed up to nearly room temperature, at which point there will be no more cooling at all. I.e. the overall effect on room temperature you can expect to get from one load of ice, compared to what you can expect from a proper heat-pump cooler.)

I think the hero of the videos you shared is kidding himself. He may get a nice refreshing feeling from blowing cold air at himself for a while; but the effect on overall room temperature will be very limited indeed. 

[IanB]

I think that we agree on the two following points:

• The lower is the temperature of the water inside the cold reservoir, the longer will take heat to melt ice packs

This is not true.

• The lower is the temperature of the water inside the cold reservoir, the lower will be the temperature of the airflow released into the the room resulting in faster cooling times and higher chances to bring room temperature down

Again, this is not really true.

When you say that temperature is not an important factor in performance and colder is not necessarily better, you probably mean that a colder temperature could generate moisture issues and you're perfectly right.

No, I simply mean that temperature is not a significant factor in any performance calculation.

However, as I already said to ebastier,  I prefer water near to 0C° plus condensation issues to fix rather than hotter water without any condensation issues.

Condensation could be good because it will dehumidify the air.

A portable ice air cooler can never, under any circumstances, cool a room down like an electric room air conditioner.

If this is not possible and under any circumstances, then the "guy is lying":

Not so much lying, just mistaken.

Let me try to give you the basics one more time.

A room air conditioner takes heat from the room and dumps it outside. Its performance is measured in how much heat it can remove per hour (e.g. kJ/h in Europe, Btu/hr in America). There is no mention of temperature here.

With an ice-based cooler, you are replacing the air conditioning unit in the window with a freezer in some other room. But the capacity is still measured in the same way. How much heat can the freezer remove from the internal contents per hour? (How much water can it freeze per hour?) The answer is a small number: much, much smaller than an air conditioner.

The electric air conditioner could freeze the equivalent of 1000 kg of water per day. If you put 1000 kg of water in your freezer, how long will it take to freeze? Can you even fit 1000 kg of water in your freezer?

You can see there is no way an ice cooler can match an air conditioner. It will not do much more than provide a cool breeze for a short while.

And once again, no mention of temperature. Temperature just doesn't come into the calculations.

I think I am over and out here. There is nothing more to say.

(Edit: corrected mistake in tons of cooling, it is per day, not per hour)

[YouCanDoIt]

5 stars for Siwastaja!! He explained perfectly well the pros and cons of colder temperatures and provided samples on how to achieve the right balance!

It makes little sense to overengineer a ghetto cooler.

You're probably right, but overengineering is so funny!!

And yes, others are right about not needing colder temperatures. Thermal capacity of ice is crap anyway, it warms up to 0degC pretty quickly, regardless if the initial temperature is -10 or -20 or -30 degC. It's the phase change from ice to water which stores (and releases) most of the energy, and this happens at 0degC pretty exactly.

Does this applies to gel ice packs too? I know there are several variants and here are discussed all the technical details. I tried to follow the discussion, but is very advanced stuff and I just preferred to buy mixed brands and see what are the ones that work better.

But this is not a problem at all, ice at 0degC is more than fine for cooling. Remember that temperature and energy are two different things. You can cool with material at 10degC, 0degC or -10degC equally well providing same cooling effect, just requiring some more surface area and/or airflow if the temperature isn't as low. Actually you don't want to cool with colder than 0degC material because then room humidity freezes and finally blocks whatever radiator type you are using. Another thing you don't want to do is to cool with >15degC water; even if you can cool with say +17degC water (using large enough radiator and air flow), it won't have drying effect which is often desirable in humidly hot conditions. If you just cool without drying, relative humidity just rises and it still feels uncomfortable. But if you run say +10degC water in your radiator, then it is already capable of drying the air down to dew point of approx. that 10degC (or a bit more), which is already very comfortable.

You said that I can cool with material at 10degC, 0degC or -10degC equally well providing same cooling effect, just requiring some more surface area and/or airflow if the temperature isn't as low.
Does this means that a colder temperature is not totally useless and still have the desirable advantage to require less surface area and/or airflow?
If I have understood well, on the other side, I don't want to cool with air which temperature is higher than 15C.
The guy from which I posted the amazing unit which cooled down a room temp by 10-20C got an output temperature of nearly 2C (its climate is dry):



Do you think that 2C is the correct balance (with the previous mentioned advantages included) ? Keep in mind that my climate is humid (around 50%). I don't know why didn't worked for the other 2 guys, there are to many variables that should be checked included dry vs humid climate. Plus my design is completely different, so I can't really compare.

The biggest problem in ghetto coolers is the capacity of typical household freezers. Even if the freezer was conveniently located in a far enough room so that its heat output doesn't ruin your cooling, you would still need to keep swapping ice packs nearly 24/7.

Fortunately the floor of my house where there is the room I want to cool is free from any household freezer.
The annoyance of swapping ice frequently is pretty much inexistent. That cooler, with a 28QT chest (3 days ice retention advertised), 2 frozen gallon jugs and a couple of ice-packs, latest 4 hours. Good for daytime, but not for nighttime.
Mine uses a 52QT chest (6 days ice retention advertised), it is nearly fully insulated and uses gel ice packs in higher quantities. I expect much longer duration and good even for nighttime.

The freezer compressor runs nearly non-stop and freezer's inside temperature rises; so you can't use it for storing foods at the same time, they get spoiled.

This is something that I have not considered at all. My freezer is pretty new technology, but apart from this I can't really imagine how this can happen. Freezer's inside temperature rises each time we introduce new food, but this is just how they are designed to work. Do you recommend to pre-cool the ice packs in the fridge?

Therefore these ghetto coolers tend to be good only for short demonstrations; you freeze a few liters of water and you can feel how it really works. Except that after 3-4 hours you are out of cold. Even if you did put more water bottles into the freezer, they are not frozen yet. The capacity isn't there: compressor power is some 200W and COP pretty crappy like 1.5-2 at most. Real air conditioners have higher evaporator temperature (remember: it does not try to cool anything to -20degC like a freezer does) and lower condenser temperature (it has a decent fan-cooled coil, not some tiny convection cooled grille on the back like freezer) so much smaller differential and therefore COP like 3-5, and still you would like to have at least 500W of input power for serious cooling.

Maybe with two-three typical household freezers, located on a balcony or something so that they don't heat up the house, only dedicated for ghetto cooling, you could do this continuously, sure. But if you don't have even a single dedicated freezer, it's only going to work for short demonstrations, and as such is not worth investing a lot of time and design into. But, because it's an interesting experiment, I don't want to shoot it down either: therefore, duct tape!

I have several ice packs, so while my cooler is cooling, at the same time the freezer is freezing the ice packs for the next cycle. Yes, with a cycle that lasts 3-4 hours, the next ice packs supply is not ready yet, buy given how I designed the cooler, I expect much longer duration, even more than the time needed to freeze a one cycle supply.

Now, given that all my estimations are right (and there's no guarantee), I'm correct to deduce that the only concern could be the power consumption of the freezer (which should not make much difference anyway because I'm using one freezer only with the highest energy saving rate) ?

It would be very interesting to hear the opinions of that guy about such statements especially. The results he achieved are in contrast with what stated here from several users. I'll invite him to join the discussion, I'm sure this thread will become more interesting if there are people with different opinions (which unfortunately seem to lack).

[ebastler]

but given how I designed the cooler, I expect much longer duration

You are not getting it, are you? You can add as many complications, bells and whistles to your cooler as you like. Ultimately, the amount of heat that one load of ice can extract from the room is equal to the energy it takes to heat and melt that load of ice. Which is, unfortunately, a rather small amount. You can't beat physics there.

You don't have a formal education in thermodynamics, which is alright. You also don't have a good intuitive feel how heat capacity, heat transfer and insulation work, which is a pity. And you seem either unwilling or incapable of extracting the relevant information from many posts where various forum members have tried to explain some of this stuff, which is annoying.

Why don't you just go ahead and build something. Either you will like the result, or you will learn something. In the meantime, I will resist the urge to make a pun about your username, but I will be out of here.

[YouCanDoIt]

Think of it this way, at least in the US we have a somewhat backwards (as is traditional) old way of specifying cooling capacity for buildings, in tons of ice. E.G. a 2 ton AC (typical of a small 3 bed house or medium size car) running flat out cools as well as 2 tons (1815kg) of ice melting over 24 hours.

You'd have to be shoveling in ice to such a device (nevermind the source) to keep up, even a little half ton window unit works out to 18 kg/hr. There's a reason we abandoned using ice blocks for any general cooling needs as soon as refrigeration tech allowed, it just isn't that great unless you've got nothing better than cutting up frozen lakes over the winter and storing it in big insulated buildings through the warm months, and that mostly just kept food cold.

https://en.m.wikipedia.org/wiki/Ton_of_refrigeration

Think of it this way, at least in the US we have a somewhat backwards (as is traditional) old way of specifying cooling capacity for buildings, in tons of ice.

This is, however, a very practical and comprehensible way of describing things, since as we have seen the concept of energy balances is not easily digested.

If we understand that a 1 ton air conditioner can freeze 1 ton of water (1000 kg) per hour, and if we then we think about replacing that with a domestic freezer, we see how absurd the situation is. We would need our freezer to freeze 1000 kg of water every hour to be equivalent to a small room air conditioner. It would need a whole warehouse full of freezers to do that.

What you say guys is highly demoralizing, but it is science and the truth of science can't be modified as our liking. I would have preferred to be aware of such truth right from the beginning.

At this point I'm wondering if my project could be nice to cool a small area of the room as IanB originally suggested. It would be a nice result anyway for me, even more if I can get longer operating times (which has always been one my main targets). If I have to move in another area I can just change direction of the airflow and this would be perfectly acceptable.

[YouCanDoIt]

The effect of the humidity of the room air cannot be minimized.  It's been a few decades since I did these calculations in MechEng thermodynamics classes, but I do remember the basics of using what's called a 'psychrometric chart'.  Look it up and how to use it.  Once you cool the room air to its dew point (meaning 100% relative humidity), a big portion of the energy required to cool it further is just consumed to condense the humidity out of the air as you cool it further.  For example: if you start with a room with 80°F air at 80% humidity, your efforts to cool it will drop the air temperature and raise the relative humidity until you hit 100% relative humidity at its dew point (73.3°F).  Cooling it further begins condensation and now a significant portion of the energy transfered is condensing water, not just cooling the air further.  So that's kind of an efficiency loss - some of the energy you'd like to use productively (reducing the room temperature) is 'lost' in just making condensed water that you don't value.

If you start with drier air at a very low relative humidity (Arizona for example), you can cool it to a much lower air temperature with the same available energy because you won't be condensing hardly any water from it.

The balance with humidity is the perceived air temperature and comfort levels. If the room air is dehumidified, even at the same temperature, then the occupants may feel more comfortable because skin perspiration becomes more effective. So cooling power used to dehumidify the air is not necessarily wasted.

The effect of the humidity of the room air cannot be minimized.  It's been a few decades since I did these calculations in MechEng thermodynamics classes, but I do remember the basics of using what's called a 'psychrometric chart'.  Look it up and how to use it.  Once you cool the room air to its dew point (meaning 100% relative humidity), a big portion of the energy required to cool it further is just consumed to condense the humidity out of the air as you cool it further.

This is technically correct, but maybe a bit misleading: you would not gradually cool the room towards dew point and then start drying. This would happen with infinite air flow over ideal (infinite performance) evaporator coil.

Realistically, any air conditioning solution would keep the indoor unit coil temperature significantly below target room temperature, in other words, air flow modest and not excessive, so that humidity is continuously removed from the beginning, and this cold (absolutely quite dry even if 100% RH) air mixes with the warmer room air, gradually bringing both temperature and absolute humidity down at the same time.

Guys, can you give me at least one good news every 5 bad news? 

Although I'm not even close to your knowledge in this materia, I was aware from the beginning of the bad things when the cooler continue to aggressively output cold air after the target temperature is reached.
For this reason it was on my purchase list a temperature controller which regulates fan speed and water pump power based on the detected temperature. Just like does a regular AC, once the target temperature is reached it slow down with some sort of "maintenance mode".
However, from your opinions seemed to be very hard to cool down a whole room at least at a minimum comfortable temperature and this means that the cooler need to run at max power for all of the time. So, a temperature controller does not help at all. May be it could be helpful if I want to cool only a small area and the required cooling power for such area is less than the maximum that the system can provide.

Today Arizona humidity is 32%. I previously posted a screenshot from a guy that live in Las Vegas. He got the same 32% humidity and said it was enough for some condensation. Right now in Las Vegas is 21%. Shouldn't Las Vegas climate be more humid than Arizona?
With 31C and 50% I would say that I'm in the middle. What I can expect?

So, decreasing humidity (even in a small room) is not possible in any way. What's the real purpose of dehumidifiers available in the market (or even the DIY one I've previously posted a video) if the achievement they are designed for can't is not reachable in any way?

[YouCanDoIt]

why no one has ever attempted to replace ice packs with Propylene glycol? It would be much less hassle and the system would be truly portable because without relying on ice it can work literally in any place.

You may be mixing up two things here? Propylene glycol does not magically get cold on its own. It is just a liquid with a lower freezing (or melting) temperature than water.

Ops! You're right! I missed out the most obvious thing: a cold source is still needed, then the additive regulates temperature. Do you see any helpful usage of this additive in my scenario?

The total cooling capacity of your system (i.e how much total heat energy it can "extract" from a room) is determined by the total energy it takes to melt the ice blocks you put in. Whether the heat transfer happens through slightly warmer or colder water (or some other liquid) may impact how long it takes to melt the ice.

I think that we agree on the two following points:

• The lower is the temperature of the water inside the cold reservoir, the longer will take heat to melt ice packs
• The lower is the temperature of the water inside the cold reservoir, the lower will be the temperature of the airflow released into the the room resulting in faster cooling times and higher chances to bring room temperature down

No, we can't agree on that. Those two points are actually contradictory. If it takes longer to melt the ice packs, then heat from the room is transferred to the ice packs less efficiently. So it will take longer to cool the room down.

I understand and this make sense. However, based on such principle, it should be even more efficient if we leave ice and cold water exposed to the open air. If I have to take this principle into account, I would say that insulated ice chest used in such projects are only to release the cold air in a controlled manner allowing in this way a longer ice retention. This when the main goal is to decrease the room temperature and such goal can be achieved (at this point the released cold is reduced just to the minimum to maintain the temperature allowing in this way longer ice retention). If this achievement is not possible (which seems to be very likely), then an ice chest should be useless because at this point would become more efficient to release immediately all the available cold without any insulating layer. Is my deduction correct?

[Someone]

However, from your opinions seemed to be very hard to cool down a whole room at least at a minimum comfortable temperature and this means that the cooler need to run at max power for all of the time. So, a temperature controller does not help at all. May be it could be helpful if I want to cool only a small area and the required cooling power for such area is less than the maximum that the system can provide.

You're adding layers of complexity for very little value. Want to feel cold? Put cold object in contact with your body (in the areas with high blood flow like the neck).
https://www.safepak.com.au/brands/body-cooler-cobber/cnt-neck-tie.html

The sort of system you are suggesting is approaching the cost and complexity of just getting a portable air conditioner, and piping it via the window.

[Someone]

This when the main goal is to decrease the room temperature and such goal can be achieved (at this point the released cold is reduced just to the minimum to maintain the temperature allowing in this way longer ice retention). If this achievement is not possible (which seems to be very likely), then an ice chest should be useless because at this point would become more efficient to release immediately all the available cold without any insulating layer. Is my deduction correct?

These are not yes/no questions, they have nuance (complications).

There is a thought/calculate/measure experiment at high school level, roughly "does adding milk to a coffee now or just before 10 min keep the coffee warmer at the 10min point?". You need to walk back and start with understanding that sort of problem before taking it to a larger and more complex system. But even then its not actually that complex and electronic tools can readily "solve" the equations:
https://doi.org/10.3390/en13112899
"Simplified Building Thermal Model Development and Parameters Evaluation Using a Stochastic Approach"

[YouCanDoIt]

Propylene glycol [...] is just a liquid with a lower freezing (or melting) temperature than water.

Yeah, and to be super clear, this is exactly what we do NOT want. We do NOT want prevent the storage medium from freezing. Solid<->liquid transition is exactly what stores a lot of energy in relatively little weight. If you prevent freezing by using antifreeze such as glycol, you would need many hundreds of liters of it to have any effect at all.

Sure, freezing is a bit of problematic transition because it physically breaks stuff due to how the volume changes quite violently (it can crack rocks), but any even remotely portable solution has to deal with this.

Thanks for making this clear!
So...ON ICE + WATER COMBO, NO ADDITIVES AT ALL!

It is interesting that ice-as-energy-storage does make sense in some circumstances, and is used in practice. For example, ice-based air conditioning systems for large buildings, in places where electricity is cheaper at night.

I have been playing with this idea of taking an commercial off-the-shelf ice cube maker - maybe a professional higher throughput version, something being used at McDonalds and the like, something with serious continuous power rating. They already solve all the hard engineering work of not only making the ice, but separating it from the evaporator coils without damaging anything. Run during cheap electricity (nighttime, or maybe solar panel self-use), store the cubes in large insulated styrofoam/etc. boxes. Replace box lid with a fan unit which blows air over the ice, and voila. As long as there is ice in the mix, the water surface keeps close to 0degC and thus it keeps dehumidifying. Extracted humidity ends up mixing with the melting water, but so what. Once melted, you swap boxes.

For this to become an actual product, we really would need to combine the outdoor unit of a split air conditioner, with the ice cube maker (evaporator only) working as the indoor unit, and then automate the mechanics of moving around the ice cubes.

Water could be reused a few times, but probably for sanitary reasons simpler and safer to use fresh water every time - ice cube makers already have solenoid valve controlled water input so most of the engineering is already done.

Siwastaja, from what you described your project and the results you got I would consider this much more than a success.
At this point you're only left with the annoyance to swap boxes. In my case I believe I should be free from this (I hope) or at least I will not have to do it frequently.

If I have understood well, the cooler was designed with an integrated freezer, right? Once cubes are ready you open some sort of lid, release them to the water and start the cooling process.

I initially thought to something like that. Vevor, the same brand of my ice chest, produce a 30L portable refrigerator (price is twice!). My idea was to avoid ice blocks, just an air intake and a blower motor to push the cold air outside, but when things seems too much easier they usually don't work. I had to realize how many things can go wrong with a refrigerator like that with two big holes and a constant flux of hot air inside of it. It would have been useful only for ice preparation and given that most of the times I need to use the cooler at home, it would have been a waste of money with an already existing freezer that does the same job.

[YouCanDoIt]

I think you refer to this video. This, along with many other I saw, seems to be not able to cool a room. They're more like "fans pushing gentle fresh air against a reduce area". I preferred to go with a design that has been proven to work and being free from issues I described in details with screenshots in this thread.

Maybe a quick estimate can be helpful:

A typical self-contained air conditioner based on a heat pump (those small vertical units on wheels) has a cooling power of 2.5 kW under ideal conditions. That's 9000 kJ per hour.

A kg of water takes 333 kJ to melt, and another 120 kJ to heat by 30 °C (say from -15 to +15°C). Hence the effect of heating and melting a gallon-sized ice block (4 kg) will be equivalent to running that small air conditioner for 12 minutes. Underwhelming, isn't it?

(This estimate is not discussing how fast you can extract heat from the room. It just estimates how much heat you can extract until all the ice has been melted and warmed up to nearly room temperature, at which point there will be no more cooling at all. I.e. the overall effect on room temperature you can expect to get from one load of ice, compared to what you can expect from a proper heat-pump cooler.)

I think the hero of the videos you shared is kidding himself. He may get a nice refreshing feeling from blowing cold air at himself for a while; but the effect on overall room temperature will be very limited indeed.

Many thanks, ebastler! Your calculations are very useful to get an idea although I'm not sure I got it in full, mostly because it's hard for me the energetic point of view.

if I have understood well, a 1 kg Ice pack will take 333 kJ to convert the underline water to around -15 (the related energy or what else), but the process does not end here. There are additional 120 kJ to convert the water from below zero to a suitable temperature for the system (15C or less, but still above zero).
So, an AC, with 9000 kJ can keep the room cool for 1 hour. With the ice cooler and 4 kg of ice only for 12 minutes which means 20 Kg of ice is needed to get 1 hour like the AC.
If this is correct, then you're right, it's incredible and very hard to believe.

IanB posted similar calculations here.
Around 10Kg to drop by 5C and for a short while (may be 1 hour like your calculations?).

So, if I'm not wrong, cooling down a room in an acceptable way can work, but depends from many conditions: room size, how many degrees we have to drop, how many kilograms of ice we can supply to each cycle, whether is a dry or humid climate and the list continue...
What I don't understand is how that guy was able to drop by 10-20C with just, maybe, a couple of kilos and for around 4 hours.
Let see once I have all the stuff ready what I can achieve! Very hard to estimate now (and to be honest, I would prefer to not know in advance). 50% humidity is not a good starting point, but I think is not even too much.

[IanB]

What I don't understand is how that guy was able to drop by 10-20C with just, maybe, a couple of kilos and for around 4 hours.

Remember, getting a stream of air to come out of a nozzle at 5°C is easy. That is not the same as cooling a whole room down to 5°C (which is basically impossible). Even a proper A/C unit would fail to do that, or even get anywhere close.

[YouCanDoIt]

I think that we agree on the two following points:

• The lower is the temperature of the water inside the cold reservoir, the longer will take heat to melt ice packs

This is not true.

• The lower is the temperature of the water inside the cold reservoir, the lower will be the temperature of the airflow released into the the room resulting in faster cooling times and higher chances to bring room temperature down

Again, this is not really true.

When you say that temperature is not an important factor in performance and colder is not necessarily better, you probably mean that a colder temperature could generate moisture issues and you're perfectly right.

No, I simply mean that temperature is not a significant factor in any performance calculation.

You're right and ebastler explained the reasons in an excellent way. There are still advantages, but not the ones we all want!

I think that we agree on the
However, as I already said to ebastier,  I prefer water near to 0C° plus condensation issues to fix rather than hotter water without any condensation issues.

Condensation could be good because it will dehumidify the air.

This is what I wrote when I published the DIY dehumidifier video here.
Design is very similar to mine, only difference is that condensation occurs in the radiator rather then in the copper coils. So, if I manage to keep water a couple of degrees above zero, my system will become also a dehumidifier.

A portable ice air cooler can never, under any circumstances, cool a room down like an electric room air conditioner.

If this is not possible and under any circumstances, then the "guy is lying":

Not so much lying, just mistaken.

Yes, the lie was just an ironical hypothesis. I have just responded to ebastler about its own calculations which basically seems to match the ones you previously posted.
Now that I understand your calculations, a mistaken is the only thing I can think of. A 2-3 degree drop as I originally suspected seems to be more reasonable, but 4 hours seems too much. However, as you see in the screenshot I posted he was firm on stating it was 10-20 degrees and even more. And the question he responded was clear.
I invited him to join the discussion because I'm very curious to solve this mistery and also because he have experience on the field while here many people tend to write their own conclusions based on what says science. This is for sure the first point to check, but science can't calculate all the variables and parameters that there are in the real world.

Let me try to give you the basics one more time.

A room air conditioner takes heat from the room and dumps it outside. Its performance is measured in how much heat it can remove per hour (e.g. kJ/h in Europe, Btu/hr in America). There is no mention of temperature here.

With an ice-based cooler, you are replacing the air conditioning unit in the window with a freezer in some other room. But the capacity is still measured in the same way. How much heat can the freezer remove from the internal contents per hour? (How much water can it freeze per hour?) The answer is a small number: much, much smaller than an air conditioner.

The electric air conditioner could freeze the equivalent of 1000 kg of water per day. If you put 1000 kg of water in your freezer, how long will it take to freeze? Can you even fit 1000 kg of water in your freezer?

You can see there is no way an ice cooler can match an air conditioner. It will not do much more than provide a cool breeze for a short while.

And once again, no mention of temperature. Temperature just doesn't come into the calculations.

I think I am over and out here. There is nothing more to say.

(Edit: corrected mistake in tons of cooling, it is per day, not per hour)

Thanks Ian, thanks to this explanation, your and ebastler calculations things are much more clear. From what I have understood, cooling down a whole room is not impossible at all, but there are so many favorable conditions required (I just mentioned a couple ones) that it makes the achievement nearly impossible.
After all, if I manage to cool down a small area (ex: the desk area) for an acceptable time I could consider myself more than satisfied.

What I don't understand is how that guy was able to drop by 10-20C with just, maybe, a couple of kilos and for around 4 hours.

Remember, getting a stream of air to come out of a nozzle at 5°C is easy. That is not the same as cooling a whole room down to 5°C (which is basically impossible). Even a proper A/C unit would fail to do that, or even get anywhere close.

This is a very good point to always keep in mind. I saw that most people (me included) do the mistake to think that if they manage to get 20C from the nozzle, it will be just a matter of time before the whole room drops to 20C. It is easy to fall into such mistake because seems obvious.

I think I am over and out here. There is nothing more to say.

I totally agree and I was going to ask people to slow down discussion. There is really nothing more to say and could be frustrating for people to read the whole discussion. The best thing to do is to put the discussion in stand-by or at least slow it down (it has become very hard for me to respond all) and continue as soon as I have a prototype up and running. This will be the most interesting and exciting part! I think it should be a matter of a week or more before I have all the parts in my hands.

[YouCanDoIt]

but given how I designed the cooler, I expect much longer duration

You are not getting it, are you? You can add as many complications, bells and whistles to your cooler as you like. Ultimately, the amount of heat that one load of ice can extract from the room is equal to the energy it takes to heat and melt that load of ice. Which is, unfortunately, a rather small amount. You can't beat physics there.

It has taken time, but I think I got it now! And there is no way to reduce the required energy whatever mechanism I invent.

You don't have a formal education in thermodynamics, which is alright.

I totally agree! Problem is that life is short and there are too many things to learn. Understanding thermodynamics is not exactly on my priority list. Since the day I was born, this is the first time where understanding thermodynamics would have been useful (and I strongly suspect the last time for the rest of my life).

You also don't have a good intuitive feel how heat capacity, heat transfer and insulation work, which is a pity.

I am surprised about this. I always believed to have at least some minimum intuition, but if an expert in this matter says I don't, then I really must take this seriously and find a way to correct my lacks.

And you seem either unwilling or incapable of extracting the relevant information from many posts where various forum members have tried to explain some of this stuff, which is annoying.

The incapability to extract the relevant information from the posts is something serious and unlike the understanding of thermodynamics, the correction of this behaviour is on top of my priority list. If you can gently tell me where I exhibited this behavior I would really appreciate. In this way I can work to improve my behavior and create less annoyances to people.
I would not call mine reluctance. It is more of the need to debate when I feel I have arguments and, most of all, such arguments are not faced by the interlocutor, but when this happens and I have no more arguments, I'm the first one to close the discussion. You can see a concrete sample on the response I got from Siwastaja for which I have given 5 stars. With just a couple of rows he demonstrated why some of my ideas does not work.

Why don't you just go ahead and build something. Either you will like the result, or you will learn something.

Ironically this is exactly what I'm trying to do. Just look at my previous message. I asked people to slow down the discussions and wait that I come back with something up and running. I have done this before I had chance to read your recommendation, but if people continue to write I have to respond. You've probably noticed that I'm not a person who ignores messages. You will have hard times trying to find unanswered questions from my side while I can find plenty ones from the other sides and this certainly contribute to what you call "reluctance and/or incapability to extract the relevant information from posts".

In the meantime, I will resist the urge to make a pun about your username, but I will be out of here.

Feel free to make a pun about my username, it can't be certainly worse than being considered like a poor unintuitive person unable to extract even the most basic relevant information from posts. And irony is always a good thing!

[YouCanDoIt]

However, from your opinions seemed to be very hard to cool down a whole room at least at a minimum comfortable temperature and this means that the cooler need to run at max power for all of the time. So, a temperature controller does not help at all. May be it could be helpful if I want to cool only a small area and the required cooling power for such area is less than the maximum that the system can provide.

You're adding layers of complexity for very little value. Want to feel cold? Put cold object in contact with your body (in the areas with high blood flow like the neck).
https://www.safepak.com.au/brands/body-cooler-cobber/cnt-neck-tie.html

The sort of system you are suggesting is approaching the cost and complexity of just getting a portable air conditioner, and piping it via the window.

A temperature controller is probably the easiest and faster implementation of the whole project. It only takes a couple of minutes to prepare the connectors needed by the board. I don't see any complexity in this.
Commercial portable air conditioners has been the main reason that forced me to do my own. There are so many things that are wrong with them.
Portable air conditioners designed like that does not pipe heat through the window. I mentioned this feature when i was evaluating a peltier module integration (idea aborted long time ago I've been told why was a bad idea).
Thanks for the link, I will take your suggestion in consideration if my project ends up to be unsatisfying.

This when the main goal is to decrease the room temperature and such goal can be achieved (at this point the released cold is reduced just to the minimum to maintain the temperature allowing in this way longer ice retention). If this achievement is not possible (which seems to be very likely), then an ice chest should be useless because at this point would become more efficient to release immediately all the available cold without any insulating layer. Is my deduction correct?

These are not yes/no questions, they have nuance (complications).

There is a thought/calculate/measure experiment at high school level, roughly "does adding milk to a coffee now or just before 10 min keep the coffee warmer at the 10min point?". You need to walk back and start with understanding that sort of problem before taking it to a larger and more complex system. But even then its not actually that complex and electronic tools can readily "solve" the equations:
https://doi.org/10.3390/en13112899
"Simplified Building Thermal Model Development and Parameters Evaluation Using a Stochastic Approach"

You're right, there aren't yes/no questions in such scenarios. Too many variables and complication that may occur. That's why I have ordered just the essential parts to get something up and running. Then, I can see what does not work as expected and possible solutions. As of now I'm just speculating although, as stated from several users, some limitations or issues cannot be worked around in any case.

[Siwastaja]

Does this applies to gel ice packs too?

Yes, there is no way around it. Water is very special medium in this energy storage property, but to utilize it, phase change between solid and liquid is needed. It happening at 0degC is luckily a very good temperature for cooling purposes.

You said that I can cool with material at 10degC, 0degC or -10degC equally well providing same cooling effect, just requiring some more surface area and/or airflow if the temperature isn't as low.
Does this means that a colder temperature is not totally useless and still have the desirable advantage to require less surface area and/or airflow?

Well yeah, but the usable temperature range is pretty limited anyway. If you run the cooling medium below 0 degC, the condensing moisture from room air freezes and blocks your system. And as I said above, going much above 10degC stops your system from being a dryer, which is pretty necessary in many conditions (unless you live in Sahara desert). So cooling systems generally run their "cool parts" (those that interface with air) between say 5 .. 10 degC. Sure 5deg instead of 10deg allows using somewhat smaller coil / less airflow / less noisy fan.

The annoyance of swapping ice frequently is pretty much inexistent. That cooler, with a 28QT chest (3 days ice retention advertised), 2 frozen gallon jugs and a couple of ice-packs, latest 4 hours. Good for daytime, but not for nighttime.
Mine uses a 52QT chest (6 days ice retention advertised), it is nearly fully insulated and uses gel ice packs in higher quantities. I expect much longer duration and good even for nighttime.

Freezer size or quality of its insulation ("ice retention") is pretty much irrelevant. Cooling power matters. Freezer's compressor is doing your actual cooling work, you are just using the ice packs as thermal energy storage / transport medium.

By all means check the input power rating of your freezer, and I bet it's between 100-300W. Assuming COP of 2, cooling power is thus in range of 200-600W, while usual room air conditioners range between 1500-4000W in cooling power, or so.

Because ice works as storage medium, you will be able to exceed that cooling power, but only temporarily: you can freeze a lot of water over 10 days, and then consume it during 1 day, giving you 10x boost in cooling power; that would equal to a real air conditioner! But then you are out of ice for the next 10 days.

Or you can find the balance of making the amount of ice the freezer is truly capable of, and keep using it at the same rate. But then the cooling capacity is underwhelming, you can't drop the room temperature/humidity by much. But a little bit yes, and maybe that is enough. And the cooling effect of the cold air hitting the skin is very real of course.

This is something that I have not considered at all. My freezer is pretty new technology, but apart from this I can't really imagine how this can happen. Freezer's inside temperature rises each time we introduce new food, but this is just how they are designed to work. Do you recommend to pre-cool the ice packs in the fridge?

This is exactly why freezer manual would state the maximum amount of food/liquids you are supposed to freeze per day, it's some quite low value like 0.5 .. 1 kg per 24hrs. The freezer is capable of freezing more, but then other food stuff is in larger risk of spoiling. For your cooling purposes you would significantly exceed this, causing the temperature to rise closer to 0degC.

Pre-cooling of course helps, but not that much. As shown above by others, temperature change stores only small part of energy, most is in the phase change. Even if you pre-cool to +1degC, you ease the work of the freezer only a bit; it still has to do most of the work, pushing energy to turn the liquid into solid. But by all means, do pre-cool if possible.

[tooki]

The effect of the humidity of the room air cannot be minimized.  It's been a few decades since I did these calculations in MechEng thermodynamics classes, but I do remember the basics of using what's called a 'psychrometric chart'.  Look it up and how to use it.  Once you cool the room air to its dew point (meaning 100% relative humidity), a big portion of the energy required to cool it further is just consumed to condense the humidity out of the air as you cool it further.  For example: if you start with a room with 80°F air at 80% humidity, your efforts to cool it will drop the air temperature and raise the relative humidity until you hit 100% relative humidity at its dew point (73.3°F).  Cooling it further begins condensation and now a significant portion of the energy transfered is condensing water, not just cooling the air further.  So that's kind of an efficiency loss - some of the energy you'd like to use productively (reducing the room temperature) is 'lost' in just making condensed water that you don't value.

If you start with drier air at a very low relative humidity (Arizona for example), you can cool it to a much lower air temperature with the same available energy because you won't be condensing hardly any water from it.

I’ve only had the most glancing of thermodynamics education in school, but I think that the really unintuitive part of it for people is the amount of energy required for a phase change, and that the temperature is not changed during the phase change. (I think that intuitively, people think that the (static) temperature alone determines the phase. They don’t consider pressure or energy.) That is, it isn’t intuitive at all that a huge amount of energy is required to change 0°C ice to 0°C liquid water, or that a huge amount of energy is needed to change 100°C liquid water to 100°C steam.

When I got to the energy for the phase changes of water in school, I already knew that the phase changes required energy, but what surprised me is just how much energy they take. Intuitively, I figured it maybe just needed a little nudge, when in reality, the phase changes require tons more energy than even fairly large changes in temperature (without a phase change).