Portable Solar Power - Page 6

 



They may have different capacities from Mt. Best, and measure the energy
consumption at different room and fridge temps. It's 90 F and 0 F in the
US. What did Dr. Chalko use at Mt. Best?


No... 24x18 = 432 Wh/day.
 

http://www.aceee.org/consumerguide/ref_less_than_18cubic_feet.pdf  that

The 4 best 15 ft^3 versions on that site all used exactly 454 kWh/year.
How odd. Maybe Amana, Danby, Maytag and Whilpool are all the same chest
fridge. Or maybe they all wanted to meet the min DOE standard. For
conversion purposes, we might only look at the prices, or whether they
all have a cold left wall and a warm back wall.


I don't need another fridge, but I'd like to see someone do this in the US
and report on results in an HP story. It seems to me we can do better than
Mt. Best, with a small freezer compartment and extra foamboard over some of
the sides and (possibly) overnight ice storage vs more batteries.

Nick

 

On 30 Aug 2005 10:11:50 -0400, nicksanspam@ece.villanova.edu wrote:


The 4.5 cu.ft. (half the size of the Mt. Best conversion) custom-built
chest version (fridge only, manual defrost) with R43 insulation, used
180 Whrs per day at 70F. The closest comparable commercially available
model is the expensive Sunfrost R4 upright, 3.91 cu.ft., with a rated
energy consumption of 100 Whrs per day at 70F.
http://www.sunfrost.com/refrigerator_specs.html   After comparing those
two, we might accept that the Sunfrost numbers are about as low as are
likely.


Between 59 and 70F. Given that at 70F the Sunfrost R4 and the
custom-built Novacool chest fridge both use substantially more energy
per cu.ft. than the Mt. Best conversion, I'm guessing it's 59F at Mt.
Best much more often than it's 70.  ;-)

Someone posted here recently about fridge tests at 70F with very many
door openings per day. I can't find the reference now, but perhaps
testing methods have changed in recent years.


I was referring to the fridge spec. You wrote that the best available
fridge averaged 60 Watts. That's 1.44 kWhrs per day. My own 8 year-old
22 cu.ft. model is rated 1.2 kWhrs per day, an average of 50 Watts for
a 50% larger unit.


I count 15 models of combination fridge/freezers that are between 14.8
and 15.5 cu.ft., and use between 376 and 386 kWhrs per year. Ah, but
now I see what you're looking at tho... 15 cu.ft. *freezers* that are
*3*54 kWhrs per year.


Me too. And since you may be the perfect guy to do it, consider
yourself nominated.  ;-)  Perhaps someone who needs a fridge would
loan a chest freezer for you to convert. Spense, if you're reading,
can you find someone who'll loan the freezer in exchange for a good
ESSN article?


Sunfrost emphasizes efficiency over price, and their thick-walled RF
16 is rated at 700 Whrs per day at 90F (which IMO is the only
temperature that should be used when comparing to normally-rated
models, unless there's a specified number of door openings). Even
accounting for the top door, I'd expect a conversion's consumption to
be higher than Sun Frost's per cu.ft. But if you could even get close
to their numbers while using a cheap freezer, that would be a
worthwhile accomplishment, and an article describing it would be a
real service to off-gridders.

Wayne

 



I like the chest config cause like most people I open
up the upright fridge and stand there an look forever!
Ha!

I'm sure that's not energy efficient as hell. <G>

With chest fridge I could pop open that top and look
quite awhile with cold air spilling out. Yes?

 



If a 15 ft^3 fridge conversion uses 366 Wh/day at 36 F in a 70 F room,
with an equivalent cubical surface of 6x15^(1/3) = 36.5 ft^2, a 4.5 ft^3
version with an equivalent surface of 16.35 ft^2 would use 16.35/36.5x366
= 164 Wh/day.


...3.91 ft^3 sounds pretty useless for a home fridge.


We might more fairly compare energy as above. Having traded some email
with Dr. Chalko, who seems less than forthcoming, I suggest we just
proceed on our own.


No thanks, altho I might contribute a little money. Maybe Steve...


What's this Sunfrost capacity? Why would a conversion with the same
capacity use more energy? We can answer this question with numbers.

Nick

 

On 30 Aug 2005 17:44:52 -0400, nicksanspam@ece.villanova.edu wrote:


Or working up from a known quantity, if we use the custom-built chest
fridge as a benchmark, scale it up, add a freezer section, and imagine
that a conversion might not be as well insulated, then we're likely to
be well above that 366 Whrs/day, and probably at or above the 70F 480
Whrs/day rating of the Sunfrost RF16. Judging by the ratings here
http://www.sunfrost.com/refrigerator_specs.html , the energy
consumption increase going from 70 to 90F seems to be about 46%. So if
we assume that the conversion will use say, 550 Whrs/day at 70, then
we might expect ~800 Whrs/day at 90. That's still pretty good compared
to commercial offerings though, especially for the price.


I agree. The only point of mentioning it was to put some of the other
numbers in perspective.


3.9 freezer, 10.4 fridge, 14.3 cu.ft. total,


Because the Sunfrosts are purpose built to be the most efficient
models on the market, and they're very well insulated on all six
sides, probably better than the freezer conversion even with
additions. The chest configuration of the conversion is claimed to be
a key to much lower consumption than commercially available fridges,
and yet a top door didn't seem to help the custom-built chest model
fridge at all considering the Sunfrost R4 numbers.  


But not with a number of assumptions.  :-)

Wayne