Efficient refrigeration

[Owly055]

     We are sort of locked into the household refrigerator paradigm where a thermostat kicks the system on and off to maintain temp without regard to energy supply.   As a child, I lived briefly with "alternative refrigeration".   We used the spring house a lot for milk, eggs, etc, and had an icebox in the house.  Not convenient, but not terribly inconvenient.   An icebox doesn't rattle and rumble like modern refrigerators...........it's dead silent, and I'm fond of quiet.  I want to hear the wind and rain, the animal noises and bird noises.    I live in a remote area where there is seldom any human generated noise.   
     On a boat it makes sense to "make hay while the sun shines"  (hay in this case being ice).    The cold plate in smaller or older refrigerators is a box shaped affair and serves as the freezer.   Convection brings the cool air down into the fridge.   A superior system as far as I'm concerned.    My big GE side by side is a miserable thing, noisy, inefficient, erratic.   

     I did some calculations the other day, and discovered that the energy storage per pound of weight in ice is about the same as a lead acid battery, but that does not take into account the fact that you are only supposed to draw a battery down to 80% charge.  That makes ice 5 times as efficient pound for pound at energy storage.   I unfortunately did not document all this, but anybody can find the info online.

     My idea of a good refrigeration system for a sailboat would be an insulated ice box, made from a small fridge and running on a 12 volt compressor somewhere out of the way for making ice.   It would freeze blue ice, which would then go into the actual galley ice box.  Both would be heavily insulated of course.  The freezing unit would have additional space other than just what is within the refrigerator ice box, and no barrier between, or a removable one.   It would be generating ice while the sun was shining.    You would then transfer the blue ice to the galley ice box which would just be a big cooler.   

     The modern 12 volt compressors use R134A, which is quite cheap........... same as your car.     I work with this stuff all the time.

                                                                  H.W.

[CharlieJ]

Much simpler is to just do away with refrigeration all together. Spent three months cruising Bahamas with none. No big hardship

[ralay]

Don't you want the street cred that comes from living off warm beer and cabbage?   ;D

I'm just kidding.  We go back and forth between putting ice in our ice box and just going without.  It's doable, buy I can totally understand why folks might want a refrigerator.  Especially a single person.  It's hard to cook a healthy meal for one without wasting food.

[CharlieJ]

Don't you want the street cred that comes from living off warm beer and cabbage?   ;D

Well in the Bahamas a bottle of beer was $6 in the grocery store. $36 a six pack

GOOD Bahamian rum was $7 a liter $9 for liter and a half

You do the math. :)

That's when I found the coconut rum/pineapple juice you enjoyed at my house!!

[CharlieJ]

as to your second part, about cooking for one .That's a problem even in a house with a fridge.

I know you are vegan, but we canned our meats in small quantities, so with other stuff, it was just enough, with no waste. Hot pack canned, at anchor, in Boot Key Harbor, using a pressure cooker. Half pint jars, stowed wrapped in socks- and different meats had different color socks. Of course, now I'm single, that may be too much- don't know :)

[Phantom Jim]

The concept of freezing "blue ice" to charge another box sounds logical, especially if the galley box is smaller.

[ralay]

Looks like the blue ice type products are just 20-40% propylene glycol solutions.  You could probably make a bunch of your own "pink ice" with marine/RV antifreeze.

I'm kind of confused about how the blue ice works.  Dow' website says that the propylene glycol is added for freezing point depression, to maintain a flexible gel, and to act as a preservative.

I get that it won't freeze until much lower than 32 deg F, but propylene glycol also has a much lower specific heat and heat of fusion than regular water.  To me (definitely not a physicist) it seems like blue ice would be a worse ice "battery" in terms of storage capacity than pure water. 

But then again why would blue ice be a product if it didn't cool things better?  I assume there's just something about it I don't understand.

[Phantom Jim]

There is an article in Good Old Boat where a fellow created "blue ice" from an alcohol and water.  He was freezing this in milk jugs and charged his portable ice chest with them.  He dyed the "ice" so he knew not to drink it.

His blue ice froze at a lower temperature than water and had better cooling properties than regular ice.

[Owly055]

Looks like the blue ice type products are just 20-40% propylene glycol solutions.  You could probably make a bunch of your own "pink ice" with marine/RV antifreeze.

I'm kind of confused about how the blue ice works.  Dow' website says that the propylene glycol is added for freezing point depression, to maintain a flexible gel, and to act as a preservative.

I get that it won't freeze until much lower than 32 deg F, but propylene glycol also has a much lower specific heat and heat of fusion than regular water.  To me (definitely not a physicist) it seems like blue ice would be a worse ice "battery" in terms of storage capacity than pure water. 

But then again why would blue ice be a product if it didn't cool things better?  I assume there's just something about it I don't understand.

     The percentage of glycol would be very small, so the specific heat reduction would be pretty minimal.  The only real value to "blue ice" is it's reduction in freezing temp.   when an ideal refrigeration temp is about 35F, with the high end at 40, if you are maintaining that temp with ice at 32, you will likely have a refrigeration temp of around 40 most of the time.
     The argument for using plain ice for this on a sailboat is strong however........ It's drinkable.   Good potable water in gallon milk jugs makes sense.  Perhaps "yellow ice" might be the better choice...... 6 packs of canned beer.    Towards the end of a long passage when you were running out of fresh stuff anyway, you could consume your "yellow ice", and replace it with ordinary water.  http://sailfar.net/forum/Smileys/default/wink.gif
     I just now did some googling on this subject and found an interesting article where someone did exactly this.   The results were very good, but you cannot do it with light beer or the cans will break.   The cooler with the frozen beer remained about 4 deg f cooler.   The beer was not fit to drink after this until allowed to normalize for a few days.   Here's the link:   http://www.livingoverland.com/2011/08/freezing-beer-for-your-cooler.html

     I understand those who feel refrigeration is not necessary on a boat.   To each his or her own.     Sailing for a few days or weeks is one thing.  Sailing long term, much of it in the tropics, and living "on the hook" rather than sailing from marina to marina, bar and restaurant to bar and restaurant, the comfort and convenience of having some sort of refrigeration is significant.   When the hot tropical sun is beating down on your boat, it had just as well also beat down on your solar panels, keeping your food cold and making ice for your drinks.  Some folks may find "piss warm" water refreshing........ I find it merely hydrating.   You can exist just fine on canned and dried goods, but  many foods are much more satisfying cold...........  With solar panels down to about a dollar a watt, why waste sun?

                                                                                                 H.W.

[ralay]

I read that GOB article too.  I think he used an isopropanol mix. 

I've been stuck on the boat for 3 days, so I've probably thinking about this WAY too much in the absence of other stimuli.  We also have an ice box and are interested in the idea of better ice.

Thinking way back to chemistry, I remember that two relevant cooling properties are specific heat (the amount of energy required to raise one unit of a substance one degree in temp) and the heat of fusion (energy required to make the phase transition from solid to liquid). 

Liquid water has a great specific heat.  It takes roughly 4.19kJ to raise 1kg of water 1 degree C.  What I didn't realize is that ice has a pretty lackluster specific heat of 2.11 kJ/kg/C.  It's​ kind of counterintuitive, but water is about twice as resistant to temperature change as ice. 

The propylene glycol and isopropanol that folks add to water to make blue ice have worse specific heat than liquid water.  Solutions made with then have worse cooling properties than liquid water, but are still better than ice.

Specific heat of:
Water (liquid): 4.19 kJ/kgC
Ice: 2.108 kJ/kgC
Anhydrous propylene glycol: 2.51 kJ/kgC
40% propylene glycol solution: 3.57 kJ/kgC
Isopropanol (liquid): 2.68 kJ/kgC

So strangely enough, ice sucks at cooling and over the temperature ranges where pure water is ice (below 32F), we're better off  taking a small hit on specific heat and heat of fusion in order to depress the freezing​ point of water and maintain a liquid solution over a wide temperature range.  At least that's how I assume it works.

The contribution of the phase change at melting plays a much larger role than the specific heat.  1kg of water absorbs 59 kJ warming from a -18F household freezer to 32F and 30kJ warming from 32F to 45F but it takes 333kJ to melt at 32F without changing temperature at all. 

So an ideal solution would have a melting point just above the temp you can achieve in your ice maker.  And more additive and you'll lose the phase change.  And less and you'll lose efficiency by having ice rather than water.

Anyone who wanted to make homemade ice mixes has a lot of choices as all sorts of other liquids and solutes will depress the freezing point of water.

The choice of additive an concentration depend a lot on the temperature of your ice maker.  I've never had a boat freezer, so I'm not sure if they get as cold as household freezers.  Blue ice makes more and more sense the lower your starting temp is, because the advantages reverse at 32F. 

Assuming boat ice makers can get far enough below 32F to make using blue ice sensible, I'd make a series of dilutions of RV antifreeze in plastic bottles and put them in the freezer.  The highest concentration that still froze would be my formula. 

That's​ all assuming power isn't​ unlimited.  It's going to take more power/time to make blue ice than regular ice.  You'd have to be sure you had enough sun/wind/whatever to freeze it solid or the penalty for losing the phase change would more than negate any advantage gained through freezing point depression.

Lastly, there's some advantage to regular ice in that it's drinkable.  The advantages of having a special ice might be negated by the advntages of having reserve drinking water.  The balance would depend heavily on how cold the freezer got, the energy generation/storage capacity of the boat, the water tankage, etc.

Either way it's pretty interesting.  I think I'm going to add a petcock to our icebox to retain the melt water.  I may also make some jugs of DIY blue ice to stick in friendly household freezers.  Even unfrozen, they'd probably help make our enormous ice box more efficient by taking up space.

[ralay]

Owly posted while I was typing that ridiculous wall of text.  What can I say?  I'm really bored waiting for the wind to die down enough that I can row in it.

Sounds like you had a lot of the same thoughts.  We have some sugar/electrolyte drink mixes that might also work instead of beer. You could always make a concentrate and dilute them further for drinking.

For the record, I can definitely see why folks might want refrigeration.  It's a big upfront cost, but we wind up spending money on ice, prepared foods, small containers, restaurant meals, wasted left overs, etc.  It's anybody's guess what works out to be more expensive over many years.  I could probably install refrigeration for less labor than the extra time I need to spend cooking when I can't cook in large batches.

[Cyric30]

Ok,
Im going to throw this out there for ppl with better knowledge than me to look into and figure out if it can be done feasibly for a boat. but i remember the grand parents talk about a deal they had once upon a time called an Ice Ball, and having investigated it a bit long ago i determined it was a Crosly Ice Ball or some derivative. anyone who want to look up more about the particulars can, but they can be made and i seen a video of a fellow heating the end with a parabolic mirror.  feasible for a boat i dont know, but still a pretty interesting deal nonetheless.

[Phantom Jim]

The Good Old Boat issue is #96 and he was using 1/4 isopropyl alcohol and 3/4 water.  This had a freezing temperature of 0 F (rather than 32 for plain water).  He had a home freezer dedicated to freezing ice for his 2 day boat adventures.  He reported that it took a long time to freeze his bottles.  A good read.  Whether one could get an onboard freezer to freeze enough ice to charge a galley ice box is the question.  Whether a "blue ice" system would enhance that is another question.  This should be fun to experiment with.

His buddy was going to use vodka so the liquid would be drinkable.

[Norman]

 :) The use of vodka is a good one.  A friend added 5% pure drinking alcohol to his jugs of frozen water from home to get the phase change at a lower temperature, and still have "Good drinkable water" when it melted.  He added a small amount of red dye to identify that it was different from his pure drinking water.  It would be quite a waste if you used the 10 proof water for cooking, and boiled off all the alcohol!

Using drinkable alcohol is desire able, as should you run out of water, it is safe.  The antifreeze version would leave you with a dangerous delimma.  Die of thirst, or drink it and die?

My memory on the exact percentage of alcohol is not certain, but it was modest.

[Owly055]

     We're getting some good useful thoughts here.  I personally like the beer solution because of the convenient packaging / handling, and the fact that the aluminum cans will transmit heat / cold efficiently.   Lacking on boat refrigeration, you could freeze your beer prior to a sailing trip, storing it in a large heavily insulated cooler, pulling out a sixpack at a time for your "refrigerator".   After it had melted, you would presumably have more space due to consumption of fresh foods, and the beer could return to a nomalized drinkable state as more "yellow ice" was added.  Managed properly, you should have a steady supply of beer to drink as well as fresh foods, possibly for a trip of a couple of weeks with really high quality coolers, and refraining from opening them frequently.   Something like Guiness, and your beer is a meal in a glass  ;-)    Dublin's Breakfast Beer.

     As far as adding drinkable alcohol to water......... Everclear is very cheap pure grain alcohol.  It is also fairly highly refined so it lacks many of the higher and lower alcohols and related compounds that cause bad reactions (hang over).   Alcohol itself will produce a hang over, but these higher and lower alcohols are responsible for a far worse hang over, and any beer, whiskey, or wine may have more or less of them.   In home brewing beer, I manage fermentation temps according to the yeast I'm using to minimize these undesirable products.   When running a still making whiskey (I've never owned one personally but built one for a friend once), we monitor the vapor temperature very closely, discarding the "heads", which contain a lot of methanol and other low boil alcohols and other undesirable compounds, and cutting off the "tails" for the same reason.

     Using pure grain alcohol like everclear, one might in fact use the water for drinking, or for cooking if you don't want to drink the alcohol, which is probably better if you are short of and rationing water.   Any alcohol consumption requires more water to metabolize the alcohol.   Hopefully none of us ends up in a situation where we have a drinking water shortage.

                                                                             H.W.

[Bob J (ex-misfits)]

Everclear, now that brings back memories. Never used it for ice but used I as the alcohol for homemade Kahlua. Good times in the mile high city:)

[ralay]

I think the real question for us would be where the heck to put an ice maker and how much power it would take us to run it.  If we couldn't do it with our current electrical system (200ah house bank, 175W solar), I think we'd just stick with cabbage and warm beer.

[Owly055]

    I just had a refrigerator crisis..........The door on my GE side by side doesn't always close by itself as it should.   I left for the afternoon with the door not completely closed, and indoor temps hit 95.  I don't have AC here, really don't need it.   I got home and "oh my god"!!   Opened the door and the temp was 70F in the fridge.  Not a big deal really, I closed the door to allow it to drop back to where it should be............  The auto defrost kicked in a few minutes later, and nothing I could do would start the fridge before it was through!!    I like auto defrost.  It's a real asset.  I remember the days of having to chip ice!!   A friend of mine just discarded a fridge because he was chipping ice and heard a hissing noise, and then it would never work.   How can you live to be 55 years old and not know that the freezer compartment is the evaporator and you should not hammer at it with a knife???    I knew that as a child!!

    The most ingenious refrigeration system I ever saw was in a homestead called The Mitchell Place, way back in the hills.   The house had long ago fallen in, but I was able to piece together their system, something most folks would have missed.   This system dated back to the 40's.   A cellar under the kitchen was heavily insulated with whatever was available, mostly wool trimmings called "tags" by sheepmen.   (I have a lifetime history working with sheep and other livestock).   Round bottom troughs outside the house were designed to be inverted to dump out large chunks of ice.  A chute like you would use to load coal into a house allowed these big chunks of ice to be slid down into the cellar.   They were stacked and covered in sawdust as in a typical ice house.    The well and hand pump made the function obviousThe big differences were that this ice house was below the kitchen, and the kitchen contained a dumb waiter (small elevator for lifting and lowering things other than people).   The dumb waiter lowered milk, eggs, and whatever else, right down into the ice house, rather than breaking off chunks of ice and carrying them into the house as was usual in those days.   Hooks were still in place for hanging carcasses of butchered animals, and shelving along one wall allowed for things to be kept long term under "refrigeration".    The Mitchell family was long gone when I got here, and the two men I knew who knew them are now dead.  This was only the tip of the proverbial iceberg of innovation on that homestead, now part of a huge ranch of about 50,000 acres.  I've been friends with 3 generations on that ranch, and only the oldest had any idea about what Mr Mitchell did.. I've seen it with my own eyes, wandered that old homestead, and admired his thinking for many years.  I've many times wished that I had been able to know the man, but I know him only by his work.  I admire true innovators beyond all other humans, and Mr. Mitchell was an innovator par excellance for his time and what he had to work with.  I could write a book about the things I've seen that these early pioneers did to address their problems and make life easier.   It's rapidly disappearing in crumbling shacks that once were typical houses of their day, dozed under and farmed over, their legacy is forgotten by almost everybody.  Lost in our modern technology, the children of today or tomorrow will likely be faced with similar challenges and only primitive technology.  All things ultimately move in a circle.  Don't forget  how to use your sextant!!!

     My refrigerator is now past it's defrost cycle and the temp is rapidly dropping.

                                                   H.W.


                   

[Bob J (ex-misfits)]

Not sure if this would be worth the trouble. Couldn't drink it, that's for sure.
Back in the 80's when we tuna fished we would go out early June & catch a couple hundred mackerel.  We'd clean them & brine them for a couple of days. The brine solution was seawater, ice & kosher salt.  It lowered the freezing temperature of the water, it was crazy cold & would keep in a 55 gallon drum for two days. I wonder if one was to freeze half gallon jugs of brine if it would last longer than conventional ice in a jug?

Bob

[Bob J (ex-misfits)]

1/2 a gallon of seawater mixed with kosher salt. Sat in the freezer for two days, slush puppy.  So much for that suggestion....