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Freezer air conditioning? - Page 2

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Posted by Jeff on May 22, 2008, 1:49 am
 
Jeff wrote:

   As a follow up to  that, I've just gotten my current issue of "Sun &
Wind Energy" and they have a section on small scale solar 'sorption
chillers. These range down to 5.5 kW and are powered by solar thermal
(probably flat panel). COPs seem to be between .6 to .8.

   I would guess that most PV has an efficiency of under 20%. It would
appear that with a high efficiency conventional AC that the same amount
of solar thermal would yield the same cooling as the PV to AC. I would
think the PV approach would be several times as expensive... Of course,
you may already have the PV and the AC.

Not sure if that article is on the website, but the site is here:

http://www.sunwindenergy.com

Note that the desiccant models, which could be more easily home brewed,
would probably have COPs greater than 1.

   Jeff


Posted by j.soar.aero on May 23, 2008, 1:18 pm
 

I suspect some of you missed a main point. I want to use the energy
from the sun that shines during to day, for cooling during the night
when the sun does not shine.

I dont want to use a large battery bank, which is expensive, costly
in terms of co2 to make, and requires a lot of monitoring,
maintenance, and periodic replacement.

I want to keep it simple too.

For my idea the freezer would make ice during the day when the sun
shines. The heat from the freezer would be exhausted out the windows
during the day when the bed room is unused. There would be no heat
from it at all added to the room in the evening as the ice cools the
room.

The cold surface of the ice would also condense the humidity from the
air on to the ice which would then be captured and then frozen the
next day. (It takes a lot of  energy when cooling just to lower the
moisture content of the air.)

But if there are other reasonable cost, low maintenance  systems that
can do what I want, I would like to know about them.

Thanks,
JRB in central Illinois

Posted by Morris Dovey on May 23, 2008, 1:36 pm
 j.soar.aero@verizon.net wrote:


Would you be willing to do the cooling during the day so that the room
is already cool when the sun stops shining?

If yes, are you willing to spend /once/ (up front) for a cooling system
that'll do the job for only the cost of running a small circulator fan?

Can't/won't say more until you spell out what "reasonable cost" and "low
maintenance" mean...

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/

Posted by daestrom on May 23, 2008, 3:20 pm
 

I suspect some of you missed a main point. I want to use the energy
from the sun that shines during to day, for cooling during the night
when the sun does not shine.

I dont want to use a large battery bank, which is expensive, costly
in terms of co2 to make, and requires a lot of monitoring,
maintenance, and periodic replacement.

I want to keep it simple too.

For my idea the freezer would make ice during the day when the sun
shines. The heat from the freezer would be exhausted out the windows
during the day when the bed room is unused. There would be no heat
from it at all added to the room in the evening as the ice cools the
room.

The cold surface of the ice would also condense the humidity from the
air on to the ice which would then be captured and then frozen the
next day. (It takes a lot of  energy when cooling just to lower the
moisture content of the air.)

But if there are other reasonable cost, low maintenance  systems that
can do what I want, I would like to know about them.


--

Okay, the basic idea can work, but you may have some drain problems with the
moisture condensed each night.

A better idea is run a conventional A/C from your solar during the day and
keep the windows closed all the time.  That way, the moisture doesn't build
up during the day when the windows are open just be be lowered at night.  It
probably takes quite a bit less energy to *keep* the room cool all day
/night than it does to cool it down every night just to open the windows and
warm / humidify it again the next day.

If it takes an awful lot of energy to *keep* the room cool during the day,
you need to fix that with insulation / shading / weather-stripping.

daestrom


Posted by Jeff on May 23, 2008, 11:14 pm
 j.soar.aero@verizon.net wrote:

Just how do you plan on doing that? I've never seen a freezer that was
set up to do that.

You've got a lot going against this plan of yours.

Freezers operate over a larger temperature range than an AC does, they
will be less efficient because of that.

Then you have that little issue of capacity.

   Lets say you have a small 6000 BTU/hr window AC. By definition 6000
BTUs is 1/2 ton of air conditioning, that is how much cooling you would
get by melting 1000 pounds of ice.

  How many pounds of ice will your freezer make in a day?

  Try this little experiment. Freeze as much ice as you can in a day and
put that in your bedroom to cool it. I don't think you'll be very happy
with the results.

   Your best return on investment is to keep heat out of the room, as
daestrom has pointed out.

   Jeff

There would be no heat


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