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Posted by tallex on September 29, 2006, 7:56 pm
 


Hi all,

I just caught up on the discussions here. I've been looking into
innovative alt energy cooling solutions myself. I need about 1.5 ton of
cooling for
a small office in the city. I have a 4-5 foot fresnel that I want to
use for a concentrator
and have access to a part of the (flat) roof for mounting anything.
Like many of you,I have a lot of prototyping experience  so pending the
final project, I can build it. This is a rental unit so I can't be
tearing down walls or anything but channelling for heat exchangers are
no problem. We were discussing this exact topic a while back,
absorbtion chillers etc
<
http://tech.groups.yahoo.com/group/next_generation_grid/message/619?threaded=1&l=1
  >
but I haven't decided on a final system yet. Geothermal  ground source
would be cool (no pun intended) but is out of the question. With
summers getting hotter and searing humidity
ond increased  climate change, we need to develop alt. energy  cooling
systems much further.
Anyway, maybe we can compare notes. Here is a link to some of what we
were discussing.

<
http://tech.groups.yahoo.com/group/next_generation_grid/message/619?threaded=1&l=1
  >


regards
tallex




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bromide

stage

temperatures

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Posted by Joe Fischer on September 29, 2006, 8:59 pm
 


          Sorry to say that more like 100 to 200 square feet
of collector would probably be needed for 1.5 ton, maybe
more if cooling after the sun goes down is wanted.
          
           Thermal solar can provide up to 1000 watts
per square meter (3500 BTU/hour), but that is
maximum ideal, and without really high tech
vacuum tube concentrators, that 1000 watts
would be only available at very low temperature
and high volume, like for heating a swimming pool.

           Higher temperatures are much less efficient,
and absorption coolers are rather complex.

           The fresnel probably would degrade in the
sun anyway fairly rapidly.

           Parabolic troughs with second surface mirror
would be the best way to go, but perhaps the idea
will depend totally on finding a local contractor and
source for a working unit in that capacity range.

           But a heat pump or A/C would still be
needed for backup on hot cloudy days.

Joe Fischer


Posted by doug on September 25, 2006, 9:33 pm
 willbanks wrote:

I say you're on the right track Will, solar cooling is the ultimate
challenge. When I was in college I studied the Servel ammonia
refrigerator system with the intent of driving it off of a solar
concentrator system. I got as far as understanding the basic principle
and here's what I remember:

The key to the system is the boiling point of your working liquid. In
the Servel, the ammonia was heated in a reservoir vessel. There was a
small (say " ) tube that allowed the warm ammonia gas (boils at a
low temperature) to travel up to the top of the unit. The gaseous
ammonia then spirals down a cooling coil (say "). As the ammonia
cools some of it turns back into a liquid. The liquid trickles down
into the mid section of the unit into the absorber coil (say " ).
Since liquid ammonia boils at -28F any heat energy inside the fridge
will cause a small portion of the liquid to turn back into a gas.
It's this State change of a substance (ammonia in this case) that
requires an input in energy to transition from a liquid to a gas
that's responsible for the cooling action.

I have to admit, I built a working steel model of this system that cost
about $00 in 1982, got a gallon of ammonia but never had the guts to
fire it up. The ammonia was pretty scary stuff. What we need is a safer
working fluid with the right properties.

Good luck on your project,

Doug Sherman
US Davis, Physics 1983


Posted by FukUSpamer@fukspamer.com on September 26, 2006, 10:33 pm
  The ammonia was pretty scary stuff. What we need is a safer
working fluid with the right properties.

Good luck on your project,

Doug Sherman
US Davis, Physics 1983

Could you elaborate more why it is scary stuff  ? and any precautions ?
Sorry I admit I am an Ass in Chemistry ..... :-)



Posted by Anthony Matonak on September 27, 2006, 2:40 am
 FukUSpamer@fukspamer.com wrote:

Ammonia is toxic at fairly low levels. Even if it doesn't kill you
outright, it can burn your lungs, eyes, skin and so forth. The whole
"it can kill or maim you for life" is the scary part.

Anthony

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