Welcome to the Solar Collector
Brainstorming and Development Page!


 

Home

Hot Air Collector

Hot Water Project 1

Hot Water & Space Heating

Solar Electric

Solar Construction 101

FAQs

Best Collectors

Simply Solar
Sign up Calendar Latest Topics
 
 
 


Reply
  Author   Comment   Page 9 of 11     «   Prev   6   7   8   9   10   11   Next
bje4709

Registered:
Posts: 1
Reply with quote  #81 
Scott, It's my first venture into solar. Question; I have a south facing wall made of metal (Morton building, barn) It's 40' long. I was thinking about your cpvc 8x8 panels along this length. Because the interior is insulated could I attache the risers to the exterior and box it in with an air gap (between the tubing and ribs in the metal) and still perform? 2. I wanted to air exchange and attache to the duct or run through pex in slab. Which would be most efficient? And will that amount of solar area and water be enough to totally heat about a 2300 sf house? Will I need to set up holding tanks?. 

Thanks for any insight
Bill E.
Nashville TN.

SolarInterested

Avatar / Picture

Moderator
Registered:
Posts: 1,074
Reply with quote  #82 
Welcome Bill. It might be a bit until Scott can reply.

I think you were asking about having the CPVC mounted directly on the building siding? I think that would be OK as the siding would take the place of the flashing which is normally used as 'fins'. Although Scott hasn't mentioned any problems with just using silicon to fasten the pipes to the backing (aluminum) it might be an idea to use additional fasteners as insurance. Also you would want some way to vent your collectors or cover them in the summer to prevent overheating (stagnation), especially with CPVC.

Is your slab insulated? Not sure about what square footage you'd need but a storage take allows you to store heat to regulate your heating and can provide domestic hot water too.

I'm sure others will chime in here with more ideas.

__________________
Both temperature rise and airflow are integral to comparing hot air collectors
stmbtwle

Avatar / Picture

Registered:
Posts: 2,955
Reply with quote  #83 
Building several cpvc water collectors that size is going to be a LOT of work. Look into an air collector with a heat exchanger, or a ARETHA (under air collectors).
__________________
Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
SolarInterested

Avatar / Picture

Moderator
Registered:
Posts: 1,074
Reply with quote  #84 
stmbtwle (Willie Tampa Bay) built a small cpvc panel which then suffered a stagnation event (no flow under sunlight). Excerpts of the relevant posts with links are shown below for reference,

The details of the panel are in the first post of  this thread (link) and were as follows:

"2' x 4' overall, glazing area 7.265 sq ft.  Both are pine, with 6mm twinwall glazing, 1/8" Thermoply backs and 3/4" Polyiso insulation on the back.  The sides are not insulated ...
The cpvc collector has 11 vertical tubes of 1/2" cpvc siliconed to aluminum flashing, and sprayed flat black."

The stagnation event and damage description are in several posts on pages 10&11 of the thread (link). Follow the link to see photos in the relevant posts.

"A few weeks ago I connected the cpvc tube "control" collector up to my hot tub...  It wasn't that long before the PV panel driving the pump got shaded, and the collector stagnated.   It's pretty much wrecked.  The tube grid is still watertight but the expansion of the tubing overstressed the silicone holding it to the aluminum fins, and the silicone let go.  IF I choose to repair it I'll wire or otherwise mechanically fasten the tubes to the fins."

"I did not observe any "ballooning" but I have observed some lengthening in CPVC hot water lines and in the pic it's apparent that at least a couple of the risers had lengthened and warped compared to the rest.  Maybe with time they might have also "ballooned", I don't know.  The end with the worst damage was also the exit (hotter) end of the collector, which was probably a contributing factor.  It's been my observation that CPVC deforms quite easily at temperatures attainable in a solar collector.  By itself, this should not be a problem as long as it is well supported.

"In this particular collector the silicone was the only thing holding the fins and the tubing together.  If the fins had been shaped to fit around the tubing I think it would have fared a little better.  Without shaped fins I think wiring the tube to the fins every few inches would help too, but that just adds to the work involved.
"


"The absorber assembly is not fastened down in the collector, it sort of "floats" on spacers that keep it off the polyiso insulation.  This was to allow for expansion and also to reduce heat loss to the back.  When connected to the hot tub it was in a horizontal position, so the "risers" became "hizers".  Whether this made any difference I don't know."

and finally:

"I brought the cpvc collector into the garage yesterday, and started to disassemble it for further inspection. It literally fell apart, the damage was much worse than even the photos had indicated. I would guess that 90-95% of the silicone had let go, and the only thing holding it together was gravity. As soon as I disturbed it, the rest of the silicone failed and there were pieces of aluminum flashing on the floor. I was thinking of rebuilding it as mentioned above, but at the moment I think I'll scrap it ..."


__________________
Both temperature rise and airflow are integral to comparing hot air collectors
Garage_Hermit

Avatar / Picture

Registered:
Posts: 2,240
Reply with quote  #85 
Hi, Bill,

Guess I am late to the party ! but welcome aboard anyhow, and enjoy the ride !

Quote:
I wanted to air exchange and attache to the duct or run through pex in slab. Which would be most efficient?


The basic difference between air and water heating in your application, would be that with AIR, you get the heat "in real time", that is, when the sun is shining...

Therefore, if you are working in the shop during the day, you would benefit directly from warm-air heating.

If you use a heated slab, your hot water would be heating the slab (or more realistically, a storage tank...) during the day: the heat is not going to warm you up "directly" - it is going into "thermal mass".

The thermal mass will start to release the stored heat, several hours later...

So if you are working in the shop at night, it ought to be warmer...
Hopefully, the heat would keep the slab warmer of a cold night, so that the next morning the shop would be generally more welcoming...

The amount of time difference for the heat to come out, is called "thermal lag"... It basically means, "inertia" - the hydronic tubes would need to be placed correctly in the slab, and the slab would need to be insulated both underneath, and around the edges, to stop the heat leaking out to earth...

Just get back to us and shout for any more ideas or inputs !  folks on here are very knowledgeable and always ready to help !

To get an idea of "how much collector area to heat a given floor area", take a look here...


Best regards,

G_H

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

Avatar / Picture

Moderator
Registered:
Posts: 1,074
Reply with quote  #86 
Quote:
Originally Posted by bje4709
Question; I have a south facing wall made of metal (Morton building, barn) It's 40' long. I was thinking about your cpvc 8x8 panels along this length. Because the interior is insulated could I attache the risers to the exterior and box it in with an air gap (between the tubing and ribs in the metal) and still perform?

Bill one qualifier to my previous reply. Solar collectors can get hot enough to melt normal polystyrene insulation. You would have to check the temperature rating of your insulation.

Folks here generally use polyisocyanurate insulation  
http://en.wikipedia.org/wiki/Polyisocyanurate

__________________
Both temperature rise and airflow are integral to comparing hot air collectors
Garage_Hermit

Avatar / Picture

Registered:
Posts: 2,240
Reply with quote  #87 
just adding to the above...

Quote:
"STYROFOAM extruded polystyrene products will melt when brought into direct contact with high temperature heat sources.  The maximum recommended continuous operating temperature is 75 ̊C."


msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_003c/0901b8038003c56f.pdf?filepath=styrofoam/pdfs/noreg/716-00150.pdf&fromPage=GetDoc
G_H

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

Registered:
Posts: 3
Reply with quote  #88 
A question for Scott,

Thanks for posting your CPVC video on Youtube and hosting this site! Just in the final throws of completing an 8 X 8 CPVC collector to heat our in ground pool. I have done some tests this week and found I am only getting about  a 4 degree F gain. Using a  1/6 HP submersible pump in the shallow end of the pool, water starts at 70F, comes out at 74F.

Here are some of the improvements I believe I can still make -

a) Not all CPVC risers are touching the aluminum flashing completely
b) Glazing(Palruf brand....not SunTuf) is not completely sealed around frame

Do you think this will help with heat gain?

I believe you said you were getting a 15 degree F gain on your Youtube video...I'm hoping to achieve the same.

At the moment the unit is on the pool deck facing south, we had had several 75F days here with full sun so I expected a higher gain.. I eventually plan to mount it on the roof and tie it into the pool filter pump system but want to complete testing first.

Any advice wold be greatly appreciated.

Thanks

Gordon

Nanaimo, BC Canada



SolarInterested

Avatar / Picture

Moderator
Registered:
Posts: 1,074
Reply with quote  #89 
Hi Gord and welcome. It may be a while before Scott can reply but I'm sure others will chime in here to help. One question - what angle is your panel at? Generally it should be pointing at the sun (horizontally and vertically) at solar noon.

Edit to add a second question - what is flow rate through the panel?

__________________
Both temperature rise and airflow are integral to comparing hot air collectors
GMac

Registered:
Posts: 3
Reply with quote  #90 
HI SI,

Thanks for the reply. The angle is appx 67 degrees (8 foot collector, 3 feet out from wall)....hope I did the math right...lol

It is positioned fairly square to solar noon.

Flow rate of that pump is appx 700 GPH, although I read that flow rate has nominal impact on overall heating due to pool volume. 

I suspect that making better contact with the risers and aluminum flashing will increase the heat, and sealing the unit better will help as well. Caulking gun in hand, will report back.

Thanks

Gord

Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics