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solardan1959

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Reply with quote  #31 
Antonio,
   Maybe this?

AntonioDB

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Reply with quote  #32 

This seems a good solution !
What do you think about my reasoning on sucking an pushing air as low as possible ?
Garage_Hermit

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Reply with quote  #33 
Antonio, OK for the deflector, in fact I think you mean a baffle...
I have done another drawing !

Looks like you will need a lot of sheetmetal, going right across your bays from left to right, and almost from top to bottom.
I suspect zinc sheet might be best and cheapest option. Alternative, metal-tray roofing, but it is not flat, so is harder to work with...
Alternatively, black plywood (not very good but cheap). Otherwise a very tight polythene membrane.

You send your cold air up between the baffle and the glass, and bring the hot air down the back of the baffle, through your screen. that is why sheetmetal is best - it will conduct between baffle and screen...

I reckon you should be counting on several powerful fans for PUMPING your collector !  And as many inputs and offtakes as you can manage, for maximum passage flow...


Good luck,
G_H
sorry for the drawings, I still don't know how to inject a drawing into a post (-:

 
Attached Files
pdf Antonio_Backpass_Screen_Collector.pdf (542.67 KB, 120 views)


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(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...

solardan1959

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Reply with quote  #34 
Antonio,
 I'm afraid to comment, as we all know hot air rises and the reverse, cold air sinks.  While dropping the air in the lowest level it will rise but at the same time your talking about pushing and pulling from the same general area, (lower level).  I think, you would be better doing either what Hermit suggested or the opposite.  Sucking from the cold is the most natural option and releasing the hot air to the upper section makes more sense but that depends on you and how you live in the house.  Is the upper area the main living area or bedrooms?  What you suggested should work fine and the heat will naturally rise but some way to get some natural circular flow would be best.  Maybe a floor vent from the upper level near the intake?
Dan
AntonioDB

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Reply with quote  #35 
Here you are how my home is inside

upper level



lower level
solardan1959

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Reply with quote  #36 
Antonio, 
  It looks like you heat with electric or hot water.  Is there any air circulation in the house between the floors?  It still looks like what you originaly suggested will work, the vent by the spiral staircase should allow plenty of heat to go upstairs but those upstairs back rooms may not benefit much.  Still, this should provide most of your heat on a sunny day.  Have you thought about what to do when you don't want the heat? (like summer)
Dan
AntonioDB

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Reply with quote  #37 
I heat with mid hot water.
Let me explain: I have a centralized hot air distribution system about in the middle of the house with ducts to every room. The air is warmed by a water/air exchanger.
Every level has it's own exchanger, fan, and ducts.
I think that the solar collector have to be a separated heating system for more simplicity. Here where I live the heating system is shut down only in June, July and August.
During these month when the sun faces on the south wall is very high and the roof will make a good shadow on the collectors. If needed I will make some holes with a motorized closing on the top of the collectors in order evacuate the hot air.
AntonioDB

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Reply with quote  #38 
Ah, I forgot to say that the house will have a thermal protection (works will start the next month) on the walls and the roof. After these works the thermal dispersion will be very low (walls and roof will have a thermal trasmittance of about 0,18 W/m2K).
Garage_Hermit

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Reply with quote  #39 
Antonio, where is your main fresh air intake ?  Also, what is the cage structure, next to your stairase ? Is this an intake shaft ?  Also, what is above your top room ? Do you have an attic, or is it a terrace roof ?  (Also, with a spiral staircase, how do you get furniture, like a bed or a bathtub upstairs, I was just wondering !)

According to the way you want to configure your intakes & offtakes, it looks (to me...) like warm air *will* flow up your staircase, you might need a ceiling mounted fan in your upstairs space, to help it up...  (I'd recommend a reversible fan, with multiple speeds...).

However, you will also still need a downcoming airstream, which could perhaps be via the bathrooms?  Perhaps there is an existing service column, between these two rooms, that takes waste pipes, water pipes etc.  First check that the duct is not sealed at floor level, if it is, you would need to break it open... Then install an air intake grille in the top of the technical duct in the upstairs bathroom, and an extractor fan in the downstairs shower room, as well as an extraction grille in the bottom of the services duct in this same room. Make sure air can enter the upstairs bathroom, either through a ventilation grille, or one in the door, or through an under-door space like for CMV.

This system would then give you a vertical circulation pattern, dry air flowing up the stairs and stale air flowing out through the plumbed rooms, down into the basement, to be picked up and recycled through the collector.  You will still need to pull in fresh (cold) air from somewhere, to make the system work.

Also, I'm no specialist, but you are right to not mix the two heating systems - your existing warm-air system was no doubt sized to special criteria like flows and temperatures, not to mention hygrometry (humidity control).

In any case, I'd suggest trying to do a thermal balance, to see just how much heat you need to warm your house, this means calculating the volume - it looks to me like you have 120 sq.m = 1300 sq.ft. You said your house is modern and well lagged, so say, 35 BTU/sq.ft, this gives a heating requirement of around 45.000 BTU.

I have no idea on your temps, but supposing you are working with inside air at 20°C and pushing it to 40°C, this is a TD of 20°C or 36°F.   Assuming 5 hours a day collecting, you theoretically require 45/5 = 9000 BTU/hr.

We decided earlier that your panel as proposed requires a flowrate of say 500 cfm. 500 cfm x 60 = 30.000 cf.ft hr

Air Thermal calculations:
sp.ht = 0.24
13.3 cu.ft. = 1 lb.

BTUH = M x sp ht x T∆

BTU H  = 2250 lbs air /hr x specific heat (0.24 ) x 36°F
= 19.440 BTU/hr

So to me it looks like your collector is probably more than twice too big for your requirements, since it is producing say 20.000 BTU and you only require 9000.

It is not a problem, you can always open a window, but in terms of expense, you might be building a collector that is twice as costly as it needs to be…

Please check my maths, I am still pretty new to this myself !

Best regards,
G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
AntonioDB

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Reply with quote  #40 
Those maps are how my home will be after the renovation works (now I live at the upper level and no staircase is present).
The structure near the staircase is simply a wall (but probably I will modify my project and I will not make that wall).
The upper level is an attic suite.
I have your same doubt about hot air flux flowing to the upper level thought the staircase.
As you have explained, probably I will need to make a forced air flux from the upper level to the lower. The better places are the north east and north west corner of the house because far away from the staircase (my doors are always open, so I don't need grilles or under door space).
About your calculations, I'd like that someone more experimented than me would check them (Dan, Scott, ...).
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