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 2 of 6      Prev   1   2   3   4   5   Next   »
Scott Davis

Avatar / Picture

Super Moderator
Registered:
Posts: 697
Reply with quote  #11 
Hi Dan,

Gary and I both made our backpass collectors to 1" as recommended in Gary's reference book.  The backpass collectors had much too high a pressure drop at 1" and did not perform as well as the screen.

__________________
Take care, Scott MD

solardan1959

Avatar / Picture

Registered:
Posts: 1,845
Reply with quote  #12 
Scott,
   I know you used one inch but the baffles seemed to be the biggest problem in your build restricting the flow.  That's why I stated that I thought it would work well because he would not need baffles.  The bigger collector I think would be well suited for a backpass and since I already have the metal sheeting  that may be my next project.  I was going to build a 20 X 1.5 or 2 downspout since I have those also, maybe I'll have to flip a coin.
Dan
solardan1959

Avatar / Picture

Registered:
Posts: 1,845
Reply with quote  #13 
I had sun for the first time lately yesterday on my pole barn heater test bed. This is a good time to give you some numbers to compare to.
Quick recap
I have polycarbonate twin wall, I have three types of collectors that are 4 feet by 8 feet each and got the following outputs at 100 cfm each.
I was getting full sun today with an outside temp of 15 degrees F or about -9 C.
(Input air 25 degrees, I was getting outside air above but added a 8 inch duct shown on the left)
black box with downspouts 60 degrees out, 15 C
Black box with 2 layer screen 70 degrees out 20 C
reflective foil with three layer screen 80 degrees out, 26 C

Probably real efficient right now but I wish I had more time so I could have dropped the voltage to the fan and see if I could get the temp up about 15 degrees each.  Also should get out my lazer thermometer and measure the glazing temp.  We did  have a good layer of snow to reflect light.   Not enough full sun right now to really heat the barn, It's too big and it's too cold out.  I'ts been 0 at night and 15 to 20 during the day.  It is keeping the workshop above freezing though. Need more collectors and a little higher to get more sun.  I figure things will start to improve about this time next month but we only seem to be getting one sunny day a week right now if we are lucky.
Dan

Attached Images
jpeg winter_sun_12_10_12.jpg (61.79 KB, 320 views)

Scott Davis

Avatar / Picture

Super Moderator
Registered:
Posts: 697
Reply with quote  #14 
Hi Dan,

Thanks for the update!  Did you have balanced, equal airflow through each collector?

__________________
Take care, Scott MD
solardan1959

Avatar / Picture

Registered:
Posts: 1,845
Reply with quote  #15 
Scott,
   Being a "shoot from the hip" kinda of guy, I always shoot first, look for a target later.  I did check the flow before and posted the results on simply solar and they were pretty close, the foil faced was slightly higher due to the shortest run.  They were all between 100-110 cfm, but...
   As I mentioned above I did add an eight inch duct for an input and it goes into a long plenum also shown in the simply solar photo section for my pole barn heater test bed.  I have not rechecked my air flow since I did that but the difference/output from the collectors has not really changed since I last modified the panels and added more screen to the center one.
   The lack of sun and work when there is any has kept me from more detailed testing but I am hoping for more sun and data before I jump to any real conclusions.  I also need to get those adjustable draft flaps like you have so I can better regulate/equalize the flow.
Dan
solardan1959

Avatar / Picture

Registered:
Posts: 1,845
Reply with quote  #16 

This is a comparison of my three Long Small Collectors for hot air.  Each of the three collectors can be separately found under the hot air collector section for more information on each collector.  The Idea behind these collectors are to build a small low profile collector that could be mounted anywhere that somebody does not want a large unsightly, (in some peoples opinion), collector, or may not have the large area required to mount one.

It was a nice day and I had it off so I did some output comparisons for my long small collectors with interesting results.  Currently having a heat wave so the outside temps were a balmy 32 degrees and this is also my input temps.

I stacked up my two downspout collectors about 10:00 and set he flow for them at 2.8 MPH, The output settled down at about 67 degrees for both downspouts at 10 CFM. 

I went to finish my screen collector and got back to find the dual downspout reading 80 degrees and the reflective downspout to read 85 degrees.  I set up the screen collector and quickly found the fans were to small for the screen collector it would only put out air at about 1.3 MPH.  But was putting out nice heat!  I looked around for a larger fan and was able to adjust it to 2.8 MPH right around noon.  I was quite surprised, though I should not have been, but the screen collector started putting out at 102 degrees.  The reflective collector was putting out at 93 degrees and the double downspout was putting out 81 degrees, (it never really put out more than that though it stayed pretty consistent at that level).

I ended up moving them and at 1:00 I got my max readings of 108 for the screen, 95 for the reflector downspout and 81 for the double downspout.  I did find out later the drill battery I used after I moved them was running the fan a little faster for the reflective so I think the 95 would have been higher if matched properly.

Then just to play around I hooked the two downspout collectors together and measured airflow around 2:00 PM.  I was getting 3.4 MPH using the drill battery from above through both downspout collectors.  The screen was putting out 99 degrees and both downspout collectors together were putting out 109 degrees.

Conclusion, screen is still the best, reflector was working better than the double downspout as the sun hit it more directly, closer to the same when the sun was at an angle. And most important of all, they all put out pretty good heat even with their small footprint.
Dan

Attached Images
jpeg downspout_comparison2.jpg (152.90 KB, 309 views)
jpeg downspout_screen_comparison1.jpg (164.74 KB, 319 views)
jpeg double_downspout_flow.jpg (76.68 KB, 317 views)
jpeg reflective_downspout_flow.jpg (74.97 KB, 316 views)
jpeg screen_flow.jpg (79.41 KB, 319 views)
jpeg max_outputs.jpg (209.30 KB, 322 views)
jpeg downspouts_together_versus_screen.jpg (148.11 KB, 325 views)

Scott Davis

Avatar / Picture

Super Moderator
Registered:
Posts: 697
Reply with quote  #17 
Very, very interesting Dan, especially using the screen horizontally with good performance! Is the screen in the traditional installation, with it against the back at the input, slanting up near the glazing at the output?
 
Thanks for the pictures!

__________________
Take care, Scott MD
solardan1959

Avatar / Picture

Registered:
Posts: 1,845
Reply with quote  #18 

Scott,
 Yes built to the standard design, details under the Forums > Solar Hot Air Collectors > Small Long Screen standard section

reflective collector details here: Forums > Solar Hot Air Collectors > New type of downspout collector with reflector

double downspout details here: Forums > Solar Hot Air Collectors > Small long double downspout collector

Now I need to try different things like vertical testing, with and without fans etc.  It is interesting how good these worked and they could be used anywhere a low profile collector is desired. But they were also cheap and easy to build, move, test, etc.
Thanks for your encouragement and ideas all along the way. Dan

solardan1959

Avatar / Picture

Registered:
Posts: 1,845
Reply with quote  #19 

We had another nice day so I followed up on Scott’s suggestion and stood the collectors on edge to see how they worked vertically.Left the fans off to see how they would do naturally and went shopping.

When I got back at 1:00 with 33 degree outside air the Reflector collector was putting out 114.6 at 1.3 MPH and the Screen collector was putting out 131 degrees at 1.7 MPH, the double downspout does not work in the configuration without a fan, (heat just collects at top).Using the efficiency calculator I get great numbers for the screen. Ok for the reflector.

Screen collector, in 33, out 131, MPH 1.7, 6.23 CFM, BTUs659, efficiency 62%

Reflector collector, in 33, out 114.6, MPH 1.3, CFM 4.77, BTUs 420, efficiency 43%

Turned on the fans and had to adjust them all for 1.8 MPH, 6.6 CFM because I could not get more than that out of the double downspout collector and dropped and broke one of my thermometers.

Once the temp stabilized the screen collector was putting out 96 degrees with the reflector downspout putting out 90, and the double downspout putting out 158 degrees, that’s when I found the broke thermometer.After I move another one there I was getting 80 degrees.As time went by the Screen always was a few degrees higher, the reflector a few degrees less, and the double downspout falling about ten degrees behind the reflector.

The collector on the wall goes to my garage and was doing pretty well I just ran the numbers and they came out too good, it’s 6X3, flat black backpass plate that I later vented to the front and added a layer of screen.I had 36 degrees going in, 91 degrees coming out, 2.3 MPH, 56.5 CFM, 3354 BTUs, efficiency 77% efficiency (vent size was 3.5X11.5) and has double glazed glass.

Dan

Attached Images
jpeg vertical_collectors1.jpg (150.55 KB, 306 views)
jpeg natural_thermosyphon_temp.jpg (105.38 KB, 300 views)

Jp27300

Registered:
Posts: 20
Reply with quote  #20 
So is a vertical configuration always better with fans than horizontal?

I'm in the mind design phase of a larger one for the house.

NH  Jeff
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics