I left some fresh-brewed hot coffee in an insulated carafe yesterday and this morning found it still piping hot–exactly 24 hours after it was brewed.
Why aren’t refrigerators designed to insulate so well? Though I know considerable R&D has gone into designing super-insulated refrigerators, my carafe’s performance rather inspired me. BTW, the carafe is perhaps 1 1/2 inches thick.
What is the feasibility–and the downside–of this?
[ul][li]The added weight of thicker, better insulated walls would make the refridgerator impossible to drag up three flights of stairs;[/li][li]The development costs of superfridges would be higher, resulting in a more expensive product (yeah, I know, initial cost vs. long-term savings. You try and tell John Q. Public that);[/li][li]A fridge has a door, which means it will always lose energy to some degree. Unless you’d like a fridge with a screw-on cap, just like your thermos. Also, when you open the fridge for even ten seconds, it loses a colossal amount of energy compared to its normal use when closed: a problem that the superfridge would have as well;[/li]Fridges these days ARE superfridges when compared to their ancestors of 3 decades ago. Energy consumption has decreased enormously.[/ul]
Actually, more insulation wouldn’t make the fridge that much heavier. The insulation is styrofoam or fiberglass, neither of which is very dense.
I think that part of the problem is that more insulation would either make the refrigerator bigger or would reduce the storage space. For example, if you doubled the thickness of the insulation, the added insulation would only be half as effective as the original thickness and your fridge would either be three inches thicker or would have a couple of cubic feet less capacity.
You could increase the efficiency by creating a vacuum in the space in the walls, but the entire fridge would have to be more strongly built and would be heavier as a result.
Besides, at some point you probably reach the point of diminishing returns. Even if you had a perfectly insulated fridge, you would still be pulling one side off every time you opened the door, allowing all the cool air to dump out across the kitchen floor. It would help to have the door on top, but this would be pretty awkward-who would want to rummage through the stuff on top to pull out the gallon of milk on the bottom.
Actually modern refridgerators ARE bigger than they used to be. My current refridgerator is 21 years old and is 27 inches deep (including door but not the handle). This seams pretty much normal for older 'fridges. Modern 'fridges are closer to 32 inches deep and use almost half the energy of units made less than a decade ago due to improved insulation and better engineering of the various components and improvements in the door seal.
yup, I have studied this in some depth as it relates to refrigeration on boats.
Insulation is very light and not expensive but it takes up space. Either you make the refrigerator (please notice the correct spelling as it is a pet peeve of mine) bigger or you lose usable space inside.
Once you have a certain amount of insulation your losses through other causes become a bigger portion of the pie and adding insulation is not going to make a big difference. Your major gain of heat is by (a) opening the door and (b) putting warm stuff you want to cool. Regarding (a) you can have a chest type (opens at the top) which is what most boats have. This avoids dumping all the cold air and taking in warm air. Regarding (b) there is not much you can do except not use the fridge.
And let’s get real, not many people are willing to have a bulky, ugly, inconvenient refrigerator, which costs more, so they can save $15 a year. Some times you can have too much of a good thing. On a boat saving energy is a concern of the highest magnitude and it justifies high investments but at home energy is much cheaper and it does not make sense to invest dollars in order to save cents.
There is the common held view of “buy a newer, energy-efficient, refrigerator and it will pay for itself in savings”. I have done several financial studies and in most cases this is just not true. Besides, it’s not like manufacturing and delivering a refrigerator has no cost in terms of energy.
Well, aren’t thermoses vacuum-insulated? My awesome Thermos™-Brand thermos died recently — it saddened me — because I dropped it and the glass broke.
It’d be a shame to drop your Super-Frige, break the glass, and be out $1,000 (I’m out $50 for the thermos, and it’s a shame!).
Thermoses are the best invention predating sliced bread. I use them all the time on the boat and have broken a few. In China you can buy them for close to nothing so I always bring a couple.
My thermos is vacuum walled and made from steel. I don’t think it’s quite as efficient as the older glass ones but it’s a price I’m willing to pay for the extra durability.
As for the OP, I think sailor is correct, the losses through the walls of the refrigerator are minimal compared to the losses upon opening the door and cooling warm foods. Feel the side of your fridge…does it feel cold? Mine doesn’t (at least it’s no colder than any other metal surface in the kitchen). This suggests to me that there’s no great energy loss through the walls
I think the same kind of logic can be applied to other items such as saucepans or bathtubs, the fact is that heat loss through the walls is negligable compared to the other modes of loss.
There’s still a lot of 70’s vintage refrigerators around. When I replaced mine, it cut my electricity usage by a massive seven kilowatts per day. I was shocked.
Sorry sailor. I accidentally bumped the ‘d’ 4 times! 
I’ll watch it next time.
Although buying a new refrigerator probably won’t pay for itself over time, it could help justify buying a more expensive energy efficient model and the difference between that and a cheap one could be recoved in energy savings.
>> Although buying a new refrigerator probably won’t pay for itself over time, it could help justify buying a more expensive energy efficient model and the difference between that and a cheap one could be recoved in energy savings
Yes, yes yes! That is exactly the point. You are hereby absolved of all your ‘D’ sins 
But many “ecoconscious” people are preaching replacing appliances when it really does not make sense.
>> There’s still a lot of 70’s vintage refrigerators around. When I replaced mine, it cut my electricity usage by a massive seven kilowatts per day. I was shocked
I doubt the veracity of this. Let’s start with getting our units right, shall we? I assume you are meaning kilowatt-hours. My refrigerator, over the long term, consumes about 3Kwh/day (more in summer, less in winter). Now can you explain to me how much your old refrigerator was cnsuming and how much your new one consumes? BTW, my refrigerator is so old and inefficient, it is beyond belief. i’d like to see your numbers.
Perhaps he/she meant exactly that. It seems to me that a saving of 7KW per day is possible, equating to a difference of about 300W per hour over a 24 hour period. [Early 70s refrigerator, ca. 2000 KWH pa, most modern, 400-800 KWH pa]
On some sail boats the insulation on the ‘hull’ side of the “ICE” box/refridg. is double the rest of the box and still going into the ‘Stream’ will about double the amount of ice usage or power time to keep things cold. They will also have a small “hand” size plug for quickly getting small things out with minimum cooling loss. YMMV
>> Perhaps he/she meant exactly that. It seems to me that a saving of 7KW per day is possible, equating to a difference of about 300W per hour over a 24 hour period. [Early 70s refrigerator, ca. 2000 KWH pa, most modern, 400-800 KWH pa]
Andy, I hope you know more about chemistry that you know about electricity and energy/work units. Your units are wrong (as I posted already before). Furthermore, even if we correct the units, the numbers are pretty much impossible.
I will repeat that the claimed savings of 7KWh/day is impossible for the simple reason that no home refrigerator consumes anywhere close to that. Savings of 1/10th that would be extremely hard to believe. You have no idea of orders of magnitude.
What would you say if I said I tinkered with my car and increased its top speed by 300 MPH?? How deep would you have to analyse what I did to judge if my claim could be true? 30 MPH would be extremely difficult to believe… how about 300?
Please give me the the brand and model of a home refrigerator which consumes over 200 Kwh/month and I will give you the name of a refrigerator which does not exist. Please give me the specs of such unit. I’d like to see them.
Unless you have in your home an industrial size, walk-in, refrigerator or you are talking about air conditioners.
This site claims that a modern refrigerator has an annual energy consumption of 564 KWh. This translates to 1.55 KWh per day. Assuming someone saves 7 KWh per day by replacing his ancient fridge with a new one, it logically follows that the old appliance was using 8.55 KWh per day. That’s 5.5 times as much energy!
I, too, find that hard to believe. 0.7 KWh savings per day would make much more sense.
My refrigerator is probably over 30 years old and the door seals are awful so it runs way more than it needs. I have measured the consumption and it is about US$30/ year. If I buy a new one which cuts that in half I am saving a whopping $15/year or $1.25/mo.
A new fridge costs about $750. At zero interest it would take 50 years to pay for itself in savings, which is longer than the fridge will last. If you calculate some rate of interest it will never pay for itself in a million years and it would actually cost you more than keeping the old one.
For a new fridge to pay for itself in savings the cost of energy would have to be roughly 10 times what is is now and that is assuming you cut the energy consumption in half!
And let’s get this straight:
Kw is a unit of power = work/time
Kwh is a unit of work like the calorie and the joule
Your electric meter measures Kwh
The page mentioned by Coldfire says a modern refrigerator uses 564kWh/year while a chest freezer uses 724kWh/year. This is a clear case where the OP is right. A freezer has much greater conductivity heat gain due to the temperature differential and much less heat gain by door openings. Massive insulation here would indeed result in substantial savings (as a percentage). You could quite easily save 200 Kwh/year which would be about $12. But most people prefer to pay $12 more than to have a huge, bulky chest freezer with 6 or 8 inches of insulation. I have a little chest freezer which probably has 2", if that.
OK, I promise to remember in future that one watt = one joule per second. I am a dumbass. Furthermore I promise to not post before I am properly awake:)
Why not, Andy? It never seems to stop me. :rolleyes:
I think a Ceramic Thermal Mass Spray - Developed by NASA would do the trick in a fridge. A very high R value without very much mass. For that matter if it is safe to use indoors. Which I am not sure of. It would be a excellent alternative to batt insulation and 3M rigid board foam. 