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re: charge fridge(with ice) not batteries?
24 jun 2004
antipodean bucket farmer wrote:
>> yesterday, john wiles did a pv nec code workshop in phila. he showed
>> a slide of a commercially-available fridge that worked that way, with
>> no batteries, just pvs and ice. some sailboat fridges have cold plates
>> that only store coolth when the engine is running.
>
>are you saying that the plates get and stay cold enough
>to keep the fridge interior temp down at night?
and a few cloudy days. this might work with an ordinary fridge with
a freezer on top and some 1 liter ice bottles in the freezer and some
extra holes in the freezer floor to let cool air drop into the fridge.
a 2'x3'x2' tall freezer would hold about 2x12x8x2.2 = 422 pounds of
ice and store 422x144 = 60.8k btu of ice-melting coolth. a 2'x3'x4'
fridge below would make the total exterior surface 72 ft^2. r10 walls
would make the thermal conductance 72ft^2/r10 = 7.2. in 70 f air, it
would lose about (70-32)7.2 = 274 btu/h, so the ice would all melt
after 60.8k/274 = 222 hours, ie 9.3 days.
>what are the plates made of?
the boat us catalog says
a holding plate system uses a plate containing eutectic fluid
similar to the gel used in "blue ice" packs. the compressor is run
until the fluid in the plate is frozen and then can be shut off
leaving the plate to keep the box cold. this type of system is
considered by some to be the best way to improve efficiencty and
reduce power consumption. instead of letting the system cycle,
the compressor can be run once or twice a day to freeze the holding
plate and then shut off for several hours. this running can be done
at the same time that the engine is run to charge batteries.
>do you have any references to manufacturers or
>suppliers?
waeco international? they make air- and water-cooled fridges
with danfoss bd50f compressors.
nick
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