Roger Priddle

re: icebox

I agree - it won't retrofit into a 32" space in a row of cabinets but I think it can be put into other (perhaps less convenient) spaces. I have a mudroom off the kitchen that will work nicely, I think. But I'm not sure the weight is an issue - don't conventional refrigerators have almost the same mass/square foot? Certainly, I would think a piano would... As for the cost, I didn't look closely enough at the website, I guess. I can't imagine how it would cost $1,000 even in today's money. Reclaimed lumber, reclaimed insulation, some old racks, some copper pipe - the only thing that seems to me to be likely to be expensive is the "refrigerant". Since i don't want to use anything Freon based (and since I haven't a clue what else one might use) it's hard to estimate a cost but it seems to me that it must be possible to do it cheaper than that.

We have a 22ft/bottom freezer, rated at 425KwHr/year but since we have all that free cold outside, I'd love to park that unit from October to July, especially since the winter months are when I get the least power from my PV.

I'm not sure what you mean by an "aftermarket temperature controller". Can you post a name or link that I can see what you're talking about?

Anyway, it's an interesting discussion and I thank you for your ideas. I'd love to be able to reduce my power consumption during the winter.

Roger

PS - and the silly attempt to force a normal font size may be unnecessary but everything looks really wrong on my screen right now!

Mark - I accept your assessment of butane and ammonia as coolants but...

I have lots of cool - well, it's outdoors, but you get my point. I just want to use that cool to freeze water inside. There must be someway - if only because I want there to be! Sub-freezing is no problem. Since the "ice box" will sit in an insulated "mud room" that can itself be the fridge for the winter months, I just want to cool the water/ice as much as possible so I can use it when the outdoor temp rises.

I feel like I'm getting bogged down in a pre-conceived idea of what it should be. My goals are these: 1)it should be passive. I have lots of cold right outside the wall so that's what I want to use. 2) It should be safe, ie non-toxic and non-explosive.

Other than that, it doesn't need to be particularly efficient making the ice, just efficient at keeping the cold in. It doesn't need to be particularly "automatic" - I can open and shut louvres or move insulation. It doesn't need to be particularly compact - the mud room is 200 sq ft and, while I do have uses for some parts of it, a 4x6 footprint is not a problem.

Our ancestors used evaporation to cool food in the summer, ice to preserve it in the winter. My only concession to "modern technology" is that I want to make the ice in the mud room, not bring it in from outside, and I would like the process to be (relatively) automatic. My brain tells me "air" should be able to work as the "refrigerant" if I can make it move.

Ok, I've tried reduce it to a minimum. I know count on you and the other smart, practical people to tell me how to do it.

Roger

Peter - am I wrong in thinking that ether, ethanol, etc. are all very flammable? This might pose a bit of a problem for the insurance company... I know that phase change makes a very effective heat transfer rate but I want to be very cautious about the materials I use. Aside from efficiency, is phase change an important function in cooling/freezing water? (maybe I could just use rum...?)

The idea of moving blocks of ice could work but I'm looking for something that will store more cold and last longer. The plan from Four Mile Island freezes a single block more than a cubic metre. Carrying that in from outside might be a challenge, whereas using a passive circulation system allows for a bigger, more permanent solution.

As for wool bales, I think I must be imagining something different than what you used. Maybe I have an image of a cotton bale - several cubic metres and immensely heavy BEFORE it's soaked in water.

But please keep the ideas coming - it's got my brain working, at least!

Roger.

Peter - We have the advantage here of several months of below-freezing temps. (Today the high is -16c.) It seems to me that I should be able to use some minimal technology to freeze a large block of water that can provide a source of cold for months. (Up here, people used to cut blocks of ice out of the lake and store it for use all summer buried in sawdust.)

I liked the idea of a renewable refrigerant (like ammonia) that could be used to cool, then freeze the block of water. Since ammonia is so corrosive, something else would be better, but I'd rather avoid something that requires a highly pressurized system. If plain air would work, that would be great but the heat carrying capacity is fairly low nor, I suspect, will it move easily unassisted.

I wonder if the slope of the various components could be optimized to encourage flow. I suppose the diameter and materials composition would make a difference too, but my degree in music has not provided me with the necessary background... <grin>. (For example, I need copper to transfer heat (water/air, air/air) and 1/2 inch or 3/4 inch is lots for that, but I wonder if PVC lines (size?) joining the copper components would increase the airflow. I would think vertical differential would be significant but I really don't know...)

Anyway, I'm throwing out all the imaginary ideas that I've played with - I fully expect to be told that there are essential flaws in my understanding, but that's why I'm here, to be corrected.

Many thanks for any help you can give.

Roger.

Hi Ken - thanks for the post.

I'm fairly lucky in this area - we've got a couple of master masons who live and work around here. Further, there's a number of "pre-fab" heaters available, one of which is the "kit" I bought.

The components are all formed from refactory cement and shipped to the site. Then the home-owner (if s\he's orders of magnitude more competent than I <grin>) can assemble it or hire a mason, which is what I did.

This is not DIY, which is fine by me, and, fully assembled, cost about as much as a forced-air furnace and ducting. Not cheap but it has the advantage of not requiring fossil fuels to fire. Instead, I use about 1.5 bush cords of hardwood for a winter (which, as I type, is about -16c with a light wind from the NW.) The house is 1200 sq ft, open plan, and stays nicely warm with about 1.5 fires a day.

The heater is described as a "contraflow heater" - I have no idea whether this is a common term or not - but 10,000 lbs of masonry make a great radiator! Mine still needs a "decorative facing" (oh well, function over form <grin>) If I hadn't wanted the water coil, there would be no electricity involved at all but the advantage of heating water for the in-floor radiant in the lower level outweighs the cost of power. My electricity budget was designed with this use in mind.

Anyway, in short, I wanted (and got) a heat source that is independent of all grid connections, that will work even "when all about me have lost their's and would like to join me". (Ok, horrible mis-quote, but I couldn't resist.) My heat costs me $300/year, a fact I mention regularly to my neighbours. They still seem to like me....

Roger.

Walter - sounds like a great stove - and you're a braver man than I am, building your own!

I like the hot water coil in the back - the pump uses 75w for about 3 hours/day. From that I get about 40kcal of heat into the water.

But, yeah, they're incredibly efficient and easy to run.

Roger.

Ok, I'm way out of my depth with some of the science here. Not that I'm complaining - I'm a highly motivated student!

I hadn't known about ammonia being so corrosive - that's a problem. If dry ice will work, I gather the only way it stays solid is under great pressure. Otherwise, one will constantly have to replace the dry ice? (not sure I understood that...)

Straw bales are great insulators but for now, how about using the insulation that gets landfilled every time a house is taken down? That's what I did here - R46 walls, R80 vertically with virtually no new insulation. If we can stop throwing valuable assets away all the time, maybe we can reduce the amount of energy we need to generate and the resources we need to use up.

Peter - I don't understand the reference to "74 bar pressure" nor do I know what a "DaS valve" is. Also (to no-one's surprise I imagine), I find "Freezers with no moving parts are far easier to build than fridges with no moving parts. " to be counter-intuitive. Surely, if I can built a freezer, it's just a matter of adjustable insulation to create a fridge attached to it....

Sorry to be dense - and maybe it will take a while, but I really am interested in understanding. So don your teacher robes and type on!

Roger.

Pam and Mark - thanks both for replies.

I'm really looking for something that will be perfect - IOW, not possible. I want it to be passive and not involve any petroleum products.

Is there an alternative to ammonia with a lower boiling point even when not pressurized? I designed my house with a "mud room" (unheated but insulated) porch on the north side of the house, about 10' x 20'. It's sort of an airlock that opens to the kitchen, so putting an ice-box there would not be inconvenient.

It sounds to me like the packed sawdust was used to hold the water that froze. Not having a convenient source of sawdust in bulk (I live in Central Ontario), I can do what I did with the house - reclaim batt insulation from houses being demolished - to build a super-insulated box that holds a permanent volume of water that I can freeze in the fall.

It can be very space-inefficient - the only real challenge is the coolant medium and how to keep it moving. I can imagine that plain air would work (albeit slowly - I don't think the heat-carrying capacity is high) and something as simple as a bicycle pump could be used to start the air moving...

Again, my theoretical and practical knowledge are lacking here - once moving, what are the chances that heat energy transfer will keep it moving? Inertia vs friction? (yes, I do understand that "You can't push on a rope!") But I've got -14c outside tonight - there should be some easy way to lose heat from water into that environment...

And I don't need the whole mass to be frozen early in the winter, just in the 4c range for the fall would work fine. The value of the ice is in the potential to cool food into the spring and summer, so if it takes most of the winter to cool the block down to -10 or -20, that's ok.

I really appreciate the discussion - sometimes I have to go over stuff a lot to figure out where my fundamental error is - so thanks for your patience.

Roger.

Mark:

Thanks for your reply and the information, especially the facts about venting.

I'm not sure I understand your point about "31°F is a lot warmer than -20°F" - are they the temps at which ammonia and butane change from vapour to liquid? The lower vapour/liquid temp. ("boiling point"?) makes sense to me to make circulation easier.

BTW, if I use propane/butane, what kind of pressures will there be in the system? Would it be different for ammonia? (This question is based on the notion that a system under less pressure would be more stable over longer periods - but I don't know if it's true or not...)

Roger.

Mark - Looking for a long-term, passive, petroleum-free solution so propane is out. Ammonia is a hazardous gas, but where I'm planning this installation any leak would go directly out-doors.

I wonder if the reason I'm nervous about just using air is the heat carrying capacity. Also, I guess, the "co-efficient of expansion" (if such exists <grin>) concerns me - something that contracts more in the cold will sink faster to encourage the rate of heat transfer.

Or maybe I'm just concerned that "air" isn't high-tech enough... The original plan calls for 1/2" copper - I wonder if 3/4 or 1" would be more effective. It wouldn't matter in the winter, but in the shoulder seasons (especially late summer/early fall) the ability to cool the water overnight might be important.

This is one of the few times that I wish I had done some more practical education than my degree in Music - I don't have either the science or the practical to figure it out.

TIA
Roger.