How can I make a perpetual iceberg in the shallow end of my friend's swimming pool for the summer?

March 5, 2009 12:10 PM

How can I make a perpetual iceberg in the shallow end of my friend's swimming pool for the summer?

I have a friend who likes to indulge my artistic conceits. Last summer he let me carve this round bush he has in his backyard into the shape of a cat's head. It didn't turn out so good, but he let me do it anyway.

This year, I suggested to him that we create a perpetual iceberg in the shallow end of his swimming pool. Ideally, it would stay icy on the hottest summer days. It doesn't have to all be made out of ice. It would be nice if it just looked that way.

I've been thinking about hockey rinks, and how they lay out pipes in concrete then run freon through them. I don't want to have to start mixing concrete to create this faux-iceberg, but I can't think of anything else.

I wonder if anyone out there can suggest a way to make this happen? We think it would be crazy hilarious. We do understand that there is a risk that we might make the pool too cool to actually swim in. My friend doesn't mind having parties just to have people over to just admire the thing.

Engineering-wise, how could we do this? We thought about actually carting in hunks of ice and carving them into an iceberg, like the way they have ice sculptures at some weddings, but the trick would be to keep it unmelted and still roughly iceberg-shaped through the summer, despite exposure to the sun.

Ultimately, this might be one of those insane ideas that you have when you're having a drink with a buddy that should never come to fruition, but I thought I'd ask the hive-mind all the same.

Thanks.

posted by Sully to sports, hobbies, & recreation (30 comments total)

Ultimately, this might be one of those insane ideas that you have when you're having a drink with a buddy that should never come to fruition, but I thought I'd ask the hive-mind all the same.

Let's say you had enough power, freon, etc to keep this thing cold enough not to melt - even with warm water all around it.... That water would therefore eventually have to get cold... freezing cold... otherwise your iceberg would simply have to melt. In fact, unless that water becomes ICE, it would have to melt. It's got direct contact with stuff above the melting point.

The power consumption alone would likely be far too expensive for this to be worth it.

Now, if you fashioned something cool out of glass, plastic, or something like that - that'd be really neat! I think the idea of having actual ice, however, is somewhere closer to impossible than it is to impractical.
posted by twiggy at 12:19 PM on March 5 [3 favorites has favorites]

You're going to have to expend a lot of energy to keep it cold. The only way I can imagine doing this is to get a big refrigeration unit, and pump the cold refrigerant into pipes embedded in the block of ice.

Since it sounds like you're willing to have it not be all ice, why not build a center core of styrofoam or some kind of plastic, wrap these cooling pipes around it, and then freeze an inch or two of ice onto it?

I'm betting it will be expensive to do and you will be putting a lot of the energy you're using to chill the ice into cooling the pool, but it's doable if not necessarily practical. If you're willing to take it out of the pool when you don't have guests over and store it in a walk-in freezer or something, it gets a lot simpler.
posted by pombe at 12:22 PM on March 5

Maybe a big plastic iceberg that you could fill with ice & freezing cold water?
posted by gnutron at 12:24 PM on March 5

With regards to the thermodynamics and energy consumption angle, you'll need the heat you remove from the iceberg via chilling to balance the heat transfer to the iceberg from the pool and from solar heating.

Working out the power required as a function of insolation, pool temperature, ice thickness around cooling pipes, and the thermal conductivity of ice is left as an exercise for the reader.
posted by pombe at 12:26 PM on March 5

It's not exactly ice, but you want to use pykrete - 14% sawdust, 86% ice. During WWII, the British built a prototype boat (!) out of it, which ultimately took 3 summers to entirely melt when the project completed. Granted, this was about 1,000 tons of the stuff, but still - 3 summers. I can't help but think a smaller version could last for a least a few months.
posted by niles at 12:33 PM on March 5 [19 favorites has favorites]

I have noted that chunks of dry ice over a kilogram or so, when submerged, quickly form a shell of ice around themselves. The "fog" production drops dramatically at that point. Dry ice wants to sink, however, so you'd have to have a mechanism to keep it aloft.

Certainly, you could put it on a small flotation item, like a blue raft, but that would be impractical for two reasons: 1) the dry ice would make the plastic surface brittle, 2) the dry ice would cause the air inside the flotation item to become cool and shrink up, thus lessening its ability to keep the dry ice from submerging.

That means that you would want big slabs of sturdy styrofoam to distribute the dry ice over, then surround it with regular ice. This isn't perpetual, but it might last the length of a party.

A true perpetual iceberg would be energy intensive. Remember those guys who cooled their PC with liquid nitrogen, using it to cool down this sluggish blue liquid (to almost a gel), pumped through their machines? You'd need something like that, something that extended off to the side via a pair of insulated hoses, quickly pulling heat off of the iceberg back to a central unit attached to a truly hellacious compressor of some sort. The excess heat might be circulated back to the other end pool.

My guess is that your wattage on this puppy would be high.
posted by adipocere at 12:35 PM on March 5

It doesn't answer your question, but wouldn't it be more awesome to just create a large, floating iceberg for the party (that could float around the pool like a big ice-cube) and then see how long it lasts? Rather than trying to build something semipermanent, that is probably just going to wind up looking like a frosted-over seafood bin? In either case, it would make sense to experiment with a scale model first (a la Mythbusters)
posted by bonobothegreat at 12:46 PM on March 5 [2 favorites has favorites]

Damn. Now I want an iceberg in my pool. But I'd settle for something made of plastic that looked like an iceberg as long as it has a beer cooler inside.

I don't have any experience with thermodynamic theory, but it seems like a long shot to me. The pykrete mentioned by niles is a good bet, but it looks more like wood than ice.

Good luck. I'd love to hear how this turns out.
posted by mattybonez at 12:53 PM on March 5

I'm fascinated by niles' answer and so far that seems like the most feasible. Provided you had access to an industrial freezer you could construct molds to form an iceberg in sections then fill with the pykrete mixture, freeze, then assemble with some sort of connector rods on-site. My main concern with this would be the amount of foreign particulate you would be introducing into the pool's circulation/filtration system. I used to work as an aquatic-recreation-technician (I was a pool boy) and I can tell you that pool pumps and filters are easier to ruin than you might think and are costly to repair or replace. At the very least you would be looking at a very time-consuming clean-up that would probably require professional supervision or intervention.
posted by Bango Skank at 12:59 PM on March 5

I salute your crazy idea but it seems too crazy. I think it would be easier just to buy blocks of ice, carve them into a cone shape, and plunk them in for parties. You could easily add beer can caddy shapes at that time and have more than one iceberg. As bonuses, they would properly float around the pool instead of being anchored and won't foul the filters.
posted by chairface at 1:22 PM on March 5 [1 favorite has favorites]

I don't think pykrete would work long-term when it comes to resisting melting. 1,000 tons of it stayed frosty for a long time for the same reason that icebergs exist for a long time — they have enormous thermal inertia. Icebergs survive years in the wild. However, structurally, pykrete is a good start.

You'd still need some kind of cooling system as suggested above by myself and others. However, you could make your version of pykrete using light blue yarn or anything long, fibrous, and the right color, to provide some structure to the 'berg. Maybe fishing line. This way, you wouldn't have to worry about particulates escaping into the pool.

It sounds like you're looking at engineering a hunk of ice with yarn (or whatever pleases you) to hold the ice together) with some bulky hoses thrown into the mix to keep running a cold liquid through it to absorb the heat. It'd need to be tuned so that it would keep a few inches of ice between the hoses and the water.

Alternatively, you just disable the checks on a cryo-arithmetic engine and drop the thing in the pool.

Damn, now I want to see if this can be done at under 5 kilowatts.
posted by adipocere at 1:22 PM on March 5

My main concern with this would be the amount of foreign particulate you would be introducing into the pool's circulation/filtration system

I was wondering about that. From what I've read (you can spend hours reading about this via Google), the wood pulp functions as an insulator, but according to this MonkeyFilter post, you can just as easily use paper towel. I wonder if you could make a relatively solid "iceberg" out of cardboard, soak it, and then freeze it? I imagine that sloppy, wet cardboard in the pool is a few orders of magnitude less messy than sawdust all over the water...
posted by niles at 1:23 PM on March 5

Buy a big sheet of translucent plastic and melt/bend it into an amorphous shape with a heat gun. Experiment with a small piece first. You could fill it with other plastic balls or shapes to simulate bubbles or imperfections.
posted by weapons-grade pandemonium at 1:25 PM on March 5 [1 favorite has favorites]

From the Wikipedia article on pykrete:

"Pykrete can be easily formed using water and some form of wood pulp, even newspaper or paper towels; other fibrous materials may also be suitable."

So - it doesn't have to look like brown wood if you don't want it to. Using white paper or paper towels should keep it white, right? Bango had a point when he mentioned care for the filtration system. Maybe some sort of mesh in front of the filters to block large particles? Does that defeat the purpose? Do I not understand pool filtration?
posted by Brettus at 1:27 PM on March 5

Just an observation for the casual iceberg builder. 90% or so of the iceberg is usually below the surface of the water, so you maybe want to change that by embedding some sort of flotation device into your iceberg contraption, otherwise you'll have a huge structure that is mostly underwater.
posted by Grither at 1:36 PM on March 5

Maybe I'm missing something, but I don't think that protecting the filtration system is the only reason you don't want sawdust or paper towel remnants floating around in your swimming pool.
posted by weapons-grade pandemonium at 1:47 PM on March 5

I'm against pykrete - you're sticking that in a pool where ideally people will swim and it will melt, muck up the water and clog the filters. Gross. Same with any kind of paper mache sort of thing.

I would think that building something out of styrofoam as a core (for the white floaty part) would be a good start, and then if you want something clear (to look like ice) you could try gently melting some plexiglass - experiment with how you heat it, you don't want black scorch marks) to make the bigger part. If you want to make it cold, then most practically I think having some flat shelf-like spaces around the structure would be neat, and you can pile those up with ice cubes/shaved ice. Shelves around the base would function as somewhere to put your drink while you're swimming.

The problem with using real ice is that in water, it will melt faster, despite your best efforts. Using huge blocks of ice, you would be best advised to haul the structure out of the water when not in use, and pack it in insulating material (whatever you have) to keep it from melting. Then you could keep it for a few days, but a few weeks in the middle of summer is doubtful. So you're better off creating a structure which you can pile ice up on each time you want to use it. If you had a shaved ice machine this would be the neatest thing you could have at your disposal - looks like snow.

The best thing I could think of to actually make a self-cooling unit would be to look into some cold-water baths for chemical use, which could circulate the cooling fluid... pricey, but gives you a place to start. If you made an iceberg out of styrofoam, you could use that as the core to attach some metal tubing to which hooks up to the heat sink unit, and then after you get that going you could just hose it down with water until it gets all iced up. In this case, I'd recommend you anchor this iceberg to an edge or corner of the pool, so it stays put and doesn't end in a line break with all the cooling fluid everywhere in some drunken accident. You probably shouldn't try to incorporate the unit inside the iceberg, IANAE (i am not an electrician) but mixing AC/DC power and water is not a great idea.

Good luck!
posted by lizbunny at 1:54 PM on March 5

I like the idea of a floating iceberg using shaved ice. Get a good thick chunk of styrofoam, ideally a round piece 4 feet in diameter and 6 inches thick. Wrap it in plastic so little bits don't crumble off into the water. Now heap as much shaved ice on their as possible. Bury a piece of dry ice in the middle if you want extra longevity. The trick is to have the top of the styro just barely above the water surface, so that the pool water doesn't actually touch the ice mountain and undermine it. (You can experiment with small pieces to figure out the right thickness, and hollow out the underside if necessary to get just the right flotation.) It will look like a floating iceberg, last for hours, cost way less than any freon-based system, and allow snowball fights and the like.

This will work also if you want solid ice rather than shaved. You can get big chunks of ice like chefs carve for sculptures and chisel out a nice iceberg to float around the pool. The styro will insulate it underneath, and if you throw something insulating over the top at night, it should last for quite a few days. (They used to keep blocks of ice in ice houses for many months.)
posted by beagle at 3:02 PM on March 5

I love the idea of a self-standing, solar-powered iceberg so much that I am tempted to do some calculations to see if it could be done.

One design area that specialises in making things appear icy is the design of beer dispense fonts like this - they basically pump glycol through them to create the formation of ice on the outside.
posted by rongorongo at 3:17 PM on March 5

Maybe some sort of mesh in front of the filters to block large particles? Does that defeat the purpose?

Yes this defeats the purpose and is a really bad idea.

The problem with an excess amount of particulate in the water is that it will eventually block the proper flow of water and pressure within the system will start to rise until the blockage is cleared or something breaks.

Where this blockage will develop will depend on the size of the particles and what breaks will depend on where the blockage develops. Most likely several things will beak in series. If the particles are large enough to be caught by the strainer basket in the pump (like yarn or shredded paper towel) that will be the first thing to break letting all the debris through to the filter. As the filter becomes clogged the filter elements will most likely crush in on themselves. Pressure will begin to build and then some part of the closed loop will fail, either a seal on the pump or filter or a pipe joint. Once you have a break in the closed system the pool will begin to drain, resulting in water damage and a costly refill. If all the seals and joints are strong enough to not break, the pump will eventually burn out its own motor from straining against the blockage.

So if you do decide to go with any form of pykrete you're going to need to monitor the filter pressure on an hourly basis. Whenever the pressure rises from its start value by 8-10psi the pump will need to be shutdown, all intake and return valves closed and the blockage cleared. You will also need to make sure that a routine disassembly, inspection, and cleaning is done on the pump and filter daily. We're talking about (depending on the type of filter and your skill level) a half-hour to hour+ long maintenance service every day. Also although you said you didn't really care about being able to swim in the pool weapons-grade is right in that it will be pretty unappealing water.

On preview beagle has a solution that avoids all of this.
posted by Bango Skank at 3:36 PM on March 5

To the commentors who mentioned icebergs surviving in the wild, don't forget this is at the extreme southern / northern latitudes, where the water temperature is very close to 0. The moment the iceberg goes on an excursion closer to the equator, they disappear in a matter of weeks.

Doing this practically (as a real iceberg) in a pool would be a challenge. There is about... 5-6kWh/day/m2 from the sun (depending on your location etc. etc.) So say you have a 16x32ft pool, that's about 50m2. So, in one day, you are getting 250kWh of heat. in your pool. You now have to remove that heat! Some of it's done for you (evaporation of the water will move a lot of that heat out for you), etc. but you're still trying to keep a block of ice from melting at 25°C+ ambient temps, without insulation. Be prepared for a large power bill! (Refrigerant coolers move more than a kW of heat per kW of input power, but they can't work miracles. Your iceberg would cost a fortune to cool, even after you've engineered the cooling system to keep it looking like an iceberg!)
In addition, the system is attempting to reach equilibrium, as long as the pool water is above 0°C. Which it will be for the aforementioned reasons. So it will be melting from the bottom as well as the top, unless you can cool your water down to 0 and keep it there.

I'm not saying this is impossible. I'm just saying it's going to cost you a lot of money.
posted by defcom1 at 4:01 PM on March 5

I would just buy a large block of ice and sculpt it into a passable iceberg form. Then use your artistic energy to affix toy boats and figurines to the side and top to create a floating diorama. A creative 3D vision of the events surrounding the Titanic floating in a pool during a party would leave me more amused and impressed than a floating Styrofoam and plastic refrigerator. Especially if the life boats coming in had beer. But maybe that's just me.
posted by dness2 at 4:50 PM on March 5

It would be less impossible if you covered your faux-iceberg with an insulating box, which you would remove when you want to admire the 'berg and/or hold a party. Also, definitely insulate the 'berg from the water, by floating it atop several inches of styrofoam, to avoid heat loss there.
posted by exphysicist345 at 4:53 PM on March 5

If the pool is big enough, there's this. Girls not included. (Perfectly SFW).
posted by beagle at 5:49 PM on March 5

This site has a faux iceberg pool floatie.I knew I'd seen these. Crazy idea but here goes. Rent a boom truck... drive to flash freeze plant or drive in cold storage with freezer facility. Fill iceberg floatie 7/8 full with water. Allow floatie to freeze. Move to pool using boom truck. Cut away pool floatie. Alternatively since it is such a large investment, have waterproof zipper custom installed in floatie by sailmaker, etc. to allow for reuse. Fantastic scheme: no easy, cheap solution. There are also small ice production plants you could could buy and install onsite that generate three hundred pound blocks of ice or you can buy these big blocks blocks from the nearest ice plant. They are used by ice carvers, fisherman etc. about 100 dollars each in Hawaii. 40 or 50 or more of them dumped humble-jumble in the pool should make a pretty convincing iceberg especially when it starts to melt.
posted by Muirwylde at 5:50 PM on March 5

beagle has the right idea, I think, and that's how I would go about it. Create a white floating base, be it out of styrofoam, or something else. Build a lightweight iceberg-shaped frame on it, and run flexible tubing filled with coolant throughout the entire frame. The tube of coolant can be run directly to an actual refrigeration unit standing on the edge of the pool. Make sure to insulate the section of tubing running through the water, and use non-toxic coolant that won't poison the swimmers or the environment if (when?) it spills after someone destroys the iceberg in a drunken frenzy. Turn on the refrigeration unit and gradually build up a layer of ice over the frame by using crushed ice and water.

The ice doesn't touch the water, and the base insulates the ice from the water to some degree. The only requirement is to maintain the iceberg frame at 0 or below.
posted by Krrrlson at 5:53 PM on March 5

Thanks everyone for your responses!
Reading them reminded me of something
I read a logn time ago, that may have
unconsciously inspired the idea.

"President Niyazov of Turkmenistan has ordered the construction of a palace made of ice in the heart of his desert country, one of the hottest on earth."
http://news.bbc.co.uk/1/hi/world/asia-pacific/3554626.stm

I agree that it would cost me too much
money to do. But I appreciate you all
collectively brainstorming the solution.
posted by Sully at 8:02 PM on March 5

How about making a HUGE amount of plastic/enamel/resin icecubes and filling the pool with them?
I'm talking about like the standard freezer sized one, just make a monkey-load of them.
It would be a cool effect of no-one wanting to get into the pool because it was filled with Ice cubes, and then when they do, its normal temperature.
posted by JonnyRotten at 12:17 AM on March 6

JonnyRotten - that IS a good idea.
I might suggest that to my friend as an alternate idea.
We might make the ice cubes larger than normal, though.
Just to stay out of the filters.
Thanks!
posted by Sully at 10:19 AM on March 6

Someone mentioned dry ice, but I believe it is poisonous. Someone should check into that. You don't want people breathing in those vapors, I don't think.
posted by Piscean at 1:16 PM on March 6