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Re: Interesting Product - Page 2

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Posted by N. Thornton on May 5, 2004, 5:23 am
 

I share your hesitations. And also think concentrators show real
promise in principle.

$000 per collector: we can get the space heating plus light for a
fraction of that price by mounting a fixed parabolic reflector on the
wall by the bottom of a sloped roof, and having some glass blocks in
the wall with ss foil placed on them top and bottom during
construction.

The effect of the E-W movement of the sun is reduced with a long
parabolic strip, since most of the sun reflected off angle still hits
the glass blocks. This does not give tracking of course.

The effect of vertical angle movement of sun is reduced by
a) limiting the concentration factor
b) the height of the glass blocks
c) the use of reflecting foil on the blocks


Such a beast would give space heating wiht minimal complications. It
also acts as a light source, resulting in lighter brighter rooms,
later lighting switch on, and permitting satisfactory use of smaller
main windows if desired, with less heat loss.

I'm not sure if that the $000 modules really offer enough advantage
over this to justify $000 each module.

This built in trough idea is something I've never seen advocated: is
there a big problem with it?


Regards, NT

Posted by DJ on May 5, 2004, 12:38 pm
 
bigcat@meeow.co.uk (N. Thornton) wrote in message  


Cost of fabrication?


Cost of installation?


Cost of blocks and masonry work?


Cost of foil installation?
 
 Now, don't get me wrong. Solar construction is always a good idea.
But, as a tradesman myself (millwright), where you can be flip about
"just adding" this and that, I do work with stone masons and sheet
metal workers frequently, and I *KNOW* their efforts are not free, nor
are their materials ;-).
 

 Actually, here, anyway, Power Spar's research indicated that while
vertical tracking was worthwhile, lateral tracking wasn't.
 

 Ok, let me see if I understand this: you'd put a parabolic mirror
outside of a glass wall in a house, thereby magnify the light into the
house for lighting, and at the same time, with the interference of the
glass blocks, transfer much of that light into heat. Ok. But if you
wanted to turn off the heat, you'd have to turn off the light, too.
 Now, in say, a climate like Canada where the outside temperature may
well hit -40C for a cloudy week in February, what, exactly, is the
insulation value of a glass wall? ;-).


 1000 Canadian$, remember ;-). But, that said, the Power Spar is for
heating LIQUID, not reflecting light. Over here, radiant floor heating
is very popular, as is hydraunic "baseboard" heating. The Power Spar
excels at that, expecially in the low-light months (the dead of
winter), surpassing even the production of traditional flat plate
collectors.

 1000 CAN$, btw, is also the "rough" going price for a conventional
flat-plate collector.


By trough, do you mean the focal point of the parabolic dish?

DJ

Posted by N. Thornton on May 5, 2004, 9:44 pm
 dj_macintyre@hotmail.com (DJ) wrote in message

I dont know, I confess this is not something I've costed up or looked
into in any depth. Cost is going to depend a lot on whether we're
talking comercial kit or do-it-yourself.

I have made troughs from sheet metal myself on equipment I made for
under a tenner. That leaves the cost of the sheet metal and some heavy
brackets to mount it, in the DIY case.



the brackets would need screwing to the wall, very minor.



blocks IIRC about 50p each for a 6" block, so 1GBP per foot. Not much
extra masonry work cost, the blocks are put in the wall as it is
built. This is for new build rather than retrofit. I dont know how
much extra time/cost this would add to the build though.


IST about 1/ square foot for SS foil. Relying on the white cement to
reflect stray light in is another possibility.


of course. And I confess to not having worked this one out. I would be
surprised if it came even close to $000 per collector though. But who
knows.



no no, a trough mirror. I'll see if I can sketch:

 /  <--- trough reflector, 8-12" high
|        .'
 \ .'  <--- pitched roof
   : <--- glass blocks / shallow dg window
   | <--- wall
   |

This is on the north facing side of the house, the trough mirror
receives the direct sunlight that reaches it over the pitch of the
roof. This is reflected in through the glass blocks or dg window,
concentrated.



clear glass blocks are used, so most of the light gets in along with
its radiant heat.


indeed, you can have heat and light or heat, but not (so easily) light
alone. You get the usual solar benefit of the heat plus the extra
light, and the light can be turned off with a blind if desired.

If determined to have light alone there are way to do that, but it is
more cost.


Houses have windows. By concentrating the light coming in you need
less window area overall. So overall you get an improvement in
insulation level.



indeed. But its more financially efficient to have that heat shine
straight in: no plumbing, no UFH system, no baseboard radiators. And
you get the light too.



no, a long trough shaped reflector. Hopefully this has cleared a few
points up.


Regards, NT

Posted by DJ on May 6, 2004, 11:45 am
 bigcat@meeow.co.uk (N. Thornton) wrote in message  
 

 Thing is, though, you're comparing the costs of a simple mirror
reflector to a concentrator/fluid heater.
  

 Light, however, is cheap. Heat is the expense. Another regional
problem we'd have with your design is the lack of thermal storage. The
Spar, for instance, or any other fluid heating interface, creates a
great deal of thermal storage in water tanks, etc. Now, indeed, your
way would do that too, but you'd have to sacrifice the rooms with the
window exposure to the reflector to either allow the floor to get very
hot, or fill the room with water tanks or something.


 I think the problem is that it's more a solution to temperate
climates. It's a good idea; any idea that makes any use of renewable
energy is a good one. But your reflector, I think, is a totally
different concept to passive solar fluid heating, like the Spar and
flat plate collectors, when used for space heating.

DJ

Posted by N. Thornton on May 6, 2004, 10:19 pm
 dj_macintyre@hotmail.com (DJ) wrote in message

almost, its comparing a concentrator with a concentrator plus fluid
system. Hence the possible cost savings.



Daylight takes window area, and window area costs heat. So the light
does save at least something.



indeed. The light is just another fillip, which brings a small
advantage.



Heating is needed in the day, the trough will provide that. storage is
a nice extra but not a requirement: you still get payoff without it.
This is cheaper to install and the payback is lower.



that is not a smart suggestion.



of course!

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