From tgl@slee01.srl.ford.com Thu Jun 16 22:23:15 EDT 1994
Article: 9739 of misc.rural
Path: bigblue.unc.edu!concert!gatech!newsxfer.itd.umich.edu!jobone!slee01.srl.ford.com!tgl
From: tgl@slee01.srl.ford.com (Tom Leone)
Newsgroups: misc.rural
Subject: refrigerator ideas
Date: 14 Jun 1994 16:31:24 GMT
Organization: Ford Motor Co.
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I understand that refrigerators account for a large percent of a "typical"
home's electricity consumption (does anyone have a reliable breakdown?).
In the interest of conservation, wouldn't it be feasible to take advantage
of cold weather for refrigeration? (obviously only in winter, in cold
climates)

Here are some ideas I have played with:

1) Old-fashioned ice box, using snow and ice from outdoors.  Too much
hassle for a typical user.

2) Refrigerator built into outside wall of house, with the refrigerator's
coils exposed to outdoor air.  This would reduce the energy required to
reject waste heat from the coils during winter, and reduce air
conditioning load for living space during the summer.

3) Refrigerator built into outside wall of house, with only the door
exposed to the inside of the house.  This would give the benefits stated
above, plus reduce heat transfer losses from frig walls during winter.
However, it might make the refrigerator into a freezer in a very cold
climate.

4) During winter, turn off the refrigerator's vapor compression
refrigeration system, and use a simple thermostatically-controlled
circulating liquid heat exchange system.  There is no need for vapor
compression if ambient temperatures are lower than the desired
refrigerator temperature.  This system is probably impractical, because it
requires the additional expense of a duplicate heat exchanger system, plus
the user (or a microprocessor) would have to switch between systems as the
weather changes.  Efficiency gains may also be small (anyone have educated
guesses?).

5) On a different note: use a small refrigerator, if you don't need the
storage space of a big one!  I understand that this is common in Europe,
and I've noticed that many Americans don't use all the space available
because they don't cook at home much anymore.

Does 2) above actually seem feasible?  Are refrigerators efficient and
durable when the coil and compressor are exposed to below-freezing
temperatures?  What else have I overlooked? (besides the obvious need to
protect outdoor components from rain, dust, animals, etc.)

I invite comments and discussion (preferably with a copy to me by email,
in case I miss a posting).  I'm also curious if I am re-inventing
something which is already commercially available.

Tom Leone <tgl@slee01.srl.ford.com>


From tgl@slee01.srl.ford.com Thu Jun 16 22:25:43 EDT 1994
Article: 9792 of misc.rural
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From: tgl@slee01.srl.ford.com (Tom Leone)
Newsgroups: misc.rural
Subject: refrigerator ideas
Date: 16 Jun 1994 14:48:10 GMT
Organization: Ford Motor Co.
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Here is a summary of the 15 or so replies I have received on the topic of
improving refrigerator efficiency by taking advantage of cold winter
weather (many thanks to all who replied).


1) Refrigerators designed for residential use will not operate properly at
very low temperatures, so my idea of putting the coil outside won't work:

> Your refrigerator would not work in the cold weather. This is because 
> the condenser temperature is so low that there is insufficient pressure 
> in the liquid refrigerant to drive it across the expanison valve. The term 
> is "low head pressure." However, you can design around this.
(thanks to Kevin Chisholm, kchishol@fox.nstn.ns.ca)


2) Many people suggested using the waste heat to pre-heat water for the
water heater.  Another variation suggested was running all the house's
water past the coils, so they would effectively be rejecting heat to a
lower temperature.


3) The refrigeratore is not a major electricity user (thanks to
inferno@sytex.com):

  From Mother Earth News, April/May 94 issure:
        heating of space        57.5%
        water heating           14.9%
        refrigeration            6.0%
        cooking                  5.5%
        air conditioning         3.7%
        lighting                 3.7%
        television               3.0%
        food freezer             1.9%
        clothes dryer            1.7%
        others                   2.3%


4) A couple of people suggested a variation on the "icebox" idea, where
ice would be stored year-round in an insulated pit, and a circulating
fluid would keep the frig cold.


In summary, it looks like the frig is not a major electricity user, plus
taking advantage of cold weather would be difficult.  So the best route to
conservation is sensible usage and maintenance (thanks to John
MacConnachie): minimize the number of times you open the door to the frig,
keep the coils clean, and check that the door seals are airtight.

Also, the newer refrigerators are much more efficient than older ones, so
it may be worthwhile to investigate payback times for a new purchase.  One
reply quoted 700 kWh/year for a new frig vs 1200-1300 kWh/year for current
in-use average; another quoted 324 kWh/year for a miniature Sears frig.

Tom Leone <tgl@slee01.srl.ford.com>


