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A brain teaser question about solar energy ? - Page 3

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Posted by jf on July 5, 2006, 11:17 pm
 
Jeff, I agree PV is certainly cheaper ...
Making solar concentrators is not that hard, which may be attractive since
it seems PV is being rejected ...
I have an old satellite dish which I am thinking of experimenting with and
adding in a TEG just for fun ...
jf



Posted by Mike on July 6, 2006, 3:47 am
 
Would a generic pelter device as used for cpu coolers, work in reverse so
that if one side is heated and the other cooled, put out any useful power.
??

Mike






Posted by Jeff on July 6, 2006, 5:10 am
 Mike wrote:

   Hi Mike!


Same principle, but I think much cheaper. Perhaps with a concentrating
dish it would be practical. Who knows what the temp limit would be!

There's a bunch of thermal electric beer coolers for the car on the
market also.

   Still tracking down materials for my solar water space heater. SunTuf
easy to find but twinwall elusive. Perhaps the SunTuf with a sheet of
lexan film siliconed to the back, open on the bottom edge for vapor escape.

  Box will be 2' by 8' 1/2" fir plywood 6" deep.  Furring strip recessed
  slightly into bottom of box with TyPar roof wrap stapled/caulked onto
that forming the recessed box bottom. A few cross braces. Foil faced
insulation stapled into box and exterior of box painted with aluminum
paint, interior untreated. Perhaps I should just TyPar the box!

Plumbed as discussed before but copper very pricey now. I've considered
steel conduit with inside swabbed with etching primer. Thermal loss due
to steel is a fraction of a degree C.

Probably will just make a single collector and test it for a few months
before adding the rest. One mistake is better that ten!

   Cheers,
Jeff


Posted by Mike on July 6, 2006, 9:21 am
 Hi Jeff

I would have thought twinwall would be readily available in the UK,
specially from places that manufacture conservatories and hot-houses. If you
use suntuf, make sure it is a version that doesn't have embedded
micro-sphere reflectors inside it. If you cannot get twinwall then can you
get the thin single layer 1 to 1.5mm polycarbonate sheeting, we can get it
here in rolls approx 1m width and any length from the local hardware store.
Two layers spaced 1/2" apart one sitting on packing blocks with the other
covering the outside would work. My current panels only have 1 layer and
work well, its flexible though so the outside edges have to be securely
clamped to stop it being sucked out by wind pressure, when it heats up as it
expands it buckles somewhat but being flexible doesn't seem to hurt it.

I wouldn't paint the inside of the box, as long as the exterior is well
primed and given 2-3 coats of good quality exterior house paint, it should
be fine

Never thought of using steel conduit, its cheap enough, be ok in a closed
loop heat-exchanger with glycol or similar as all the oxygen would get used
up in the first few days, so rusting wouldn't be a problem. Use a non
conductive jointer (rubber hose) to your HWC so you don't get galvanic
action due to dissimilar metals and a conductive fluid.

Ive got one of those small beer coolers, runs off 12 volts dc, seeing as its
winter here wont be using it for a while, might rip it to bits get the
pelter device out. If  I bolt it to a water cooled heatsink on one side and
direct a focused source of sunlight from a curved 1m dia mirror, I wonder
what will happen ??

Best of luck with you panels..

Mike



Posted by Jeff on July 6, 2006, 1:47 pm
 Mike wrote:

Hi Mike,

I need to change my munged email as I did that one quickly.
dont_bug_me_@all.com would not fly when I tried to use it. As it is I've
got spammers hijacking my real email as a "from". What are you going to
do when they are in China!

  I'm in Atlanta, Ga, USA, sometimes in Cleveland, Ohio, USA. There's
little interest in solar in my country and a government that cares
little more than the freedom to consume freely.


I can get that in sheets. What about the UV coating (or lack of)?

  we can get it

That's cool.

   Sounds right.

I'm thinking drainback and figured the draining would re-gas the fluid,
could be wrong! Using conduit would cut cost of collector to less than half.

  Use a non

It might melt, but it would be spectacular! Theoretically there are
thermionic, read that like a vacuum tube where electrons are boiled off
a  cathode to create a current. That would work at very high temps.
Trouble with theory is that working devices are hard to come by!

As a youth my Dad had given me a number of different thermocouples and I
remember generating enough current to run a small oscillator.
Iron/Constanton makes a good thermocouple. Now, I wonder how Iron/Copper
would do as constanton is 60% copper and 40% nickel. The nickel is
probably in there to keep it from electrolysing...


   Sigh, it's been taking longer that I would have thought!

   Cheers,
Jeff


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