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September 29, 2008


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Do you know what gets me? Why doesn't every house in the world have a heat pump?

Gunnar Tveiten

You can do what you suggest. The only problem is it ends up costing SIGNIFICANTLY more, and may or may not end up saving you power.

You are forgetting that venting heat to the outside of the house is actually a LOSS in winther, because doing so will increase your heating-bill. Infact if you live in a part of the world where electric heating is the norm, the fridge consumes ZERO energy in the heating-season.

(it does eat some power, but it gives all of that back in the form of heat, so if you turned it off, the power you save would be spent on heating instead)

In the summer, venting to the outside IS a win, particularily if you're somewhere warm enough that you're running AC. But the nessecary building-work is expensive, much more so than mass-production of identical fridges in a factory, so it's not a given that you'll ever make back the invested money.

Rustin H. Wright

Uh, Gunnar, you seem to have a habit of not reading my posts very carefully.

First of all, re "winther" [sic] reuse of heat, please go back and read again where I wrote "The rest of the year that heat can go right into the house air vents, where that heat is a feature, not a bug.".

Secondly, you're wrong that a conventional fridge consumes "ZERO energy" at that time of year. There is such a thing as more or less efficient ways to generate heat electrically. Just go look at the BTU to wattage comparisons of different heaters to see how much. Since a fridge isn't designed to do this work, it not only doesn't have appropriate geometry or a blower, it is still releasing most of that heat up into the area that it is trying to chill.

As for "building-work" being more expensive, have you ever actually priced this out? I have and if this were being done on anything like the scale conventional systems are it would be considerably cheaper than how we do things now. Economies of scale aren't some magic thing that only applies to those who are using them on a given day. They would apply to this approach to an even greater degree since you would now have companies building and selling much smaller and more flexible components instead of trying to sell one massive device that integrated chiller, radiator, tubing, shelving, insulated box, hinges,door, etc., etc..

Since you would be replacing large heavy motors and chillers and assembled, massive boxes that need to be cast, assembled, shipped, etc, with much smaller ones that use far less material and can mostly literally just be snapped into place on site, having been shipped flat or even created on site to some degree (if, for example, the insulated ducting is made of cob lined with sheet plastic), costs have the very real potential to go down, not up.

Lastly, the very assumption that a house should need to use significant amounts of energy to be heated or cooled at any time of year has long since been disproven. People were building houses that didn't need dedicated heating systems in Vermont in the seventies and have been buildings that stay cool midsummer in the desert for even longer.

It is a common and very destructive fallacy to assume that residences need to use tons of fuel to stay at a desirable temperature and to then conclude that all sorts of wasteful systems are thus "harmless". People used to try that crap to denigrate replacing wasteful incandescent bulbs with better options, to attempt to trivialize energy-efficient computers, and on and on. It was bad logic then and it's bad logic here.

Rustin H. Wright

Ed, (should I be saying "Edmund?)

I couldn't agree more. The idea that we're just now seeing geothermal systems come in makes me a bit nuts. With the exception of fireplaces and certain stove types, the entire way we approach heating and cooling seems breathtakingly lunkheaded to me. But I guess that we shouldn't expect any better in a society with terribly reasoning skills, very little knowledge of physics, and a persistant tendency to choose cheap and fast over effective.



I'm finding this post very late, but wanted to comment on the reason to keep cold water jugs in the fridge.

Every time you open up the fridge, the cold air inside mixes with the warm are in the room. When you then close the fridge, it then has to cool the new air mix in the fridge to the previous levels. By keeping sealed gallons of water in the fridge, there is less air to be re-cooled each time you open the fridge.

The basic point is that the more full your fridge and freezer are, the less air the fridge will have to re-cool each time you open it, and the less energy your fridge will use. Full fridges use less energy than empty fridges.

Rustin Wright

Mish, actually it's more precise than "full" or "empty".

The reason to keep full jugs inside a fridge is to shift the net percentage of the mass, not just air, MASS, within the insulated area that has to be chilled all over again once the door has been opened.

We do this now with full jugs because we are expected to treat the fridge itself as an unmodifiable and sacred box to be left inviolate while we do nothing but move around what sits in the storage area. A massive block of stone or cement, especially one that was ridged to increase surface area, would do a far better job of shifting that percentage of mass that needs to be rechilled without taking up space in the area reserved for storage.

Yes, full fridges use less energy. In the sense that matters here, a block of cement even just six inches tall and stretching all the way from the front to the back and left to right would do far more to "fill" the fridge than any number of milk jugs. And would do so in a way that was easier to clean, put less stress per pound on the fridge, and wasn't subject to problems like microorganisms infecting the water and eventually spreading to other things being stored.

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