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
Register Calendar Latest Topics
 
 
 


Reply
  Author   Comment   Page 1 of 2      1   2   Next
Scott Davis

Avatar / Picture

Super Moderator
Registered:
Posts: 697
Reply with quote  #1 
This serpentine copper / aluminum design was my first solar project.  I set it up as a drain back system and it worked okay, but not as efficiently as my later projects.

I didn't use enough copper in this design and the thermal bond of the copper to the aluminum could have been much better.  Not really being a DIY guy (I'm an office manager and software developer) some of the projects I tried next were easier and worked better.  You'll find a lot more information about this project here:

http://www.n3fjp.com/solar/solarwater/solarhotwater.htm

Have you built a serpentine copper / aluminum solar collector? Please reply and tell us about it here! Please be sure to include pictures if you can!

Do you have questions about the serpentine copper / aluminum solar collector? Please reply, this is the place to ask about it! We will do our best to help!


__________________
Take care, Scott MD

LucidBuddha

Registered:
Posts: 43
Reply with quote  #2 
Hi,

I'm planning a solar water collector/storage tank/radiant floor project. I've been researching for months and am hoping to have the system completed by November or sooner. 

I'm hoping my collector will be serpentine copper so I don't have to worry about leaks or soldering T joints. I saw something about using serpentine collectors in parallel. [collector5]Something like this. Is there a reason the inlet in the picture is at the bottom and not the top? I was thinking of pumping to the top so any drain back would get heat from the collector on the way down to the tank. 

I also had a question on size. My south wall is about 18' x 12' and I had planned 4 4'x8' collectors. However, someone said a good estimate of energy is 1,000 BTU/hr per square foot of collector space. 4x8=32,000 BTU/hr for 1 panel? Is this accurate?

My calculations for my radiant floor show my space loses roughly 22,000 BTU/hr on 1 degree days. Again, paper calculations backed by LoopCAD software shows I may get between 11,000 and 14,000 BTU/hr from the radiant floor- which will be fine since we rarely get those really cold days here on the Front Range of the Rockies (Boulder/Denver Colorado). I can always supplement with a space heater. So, I guess I'm wondering if I need more than one collector if my radiant system is only going to be able to use maybe 1/2 of what's collected in a day. If anything, overkill will just provide more heat stored in the tank for the eventual domestic hot water loop. And I'm thinking I could start with 1 and add-on if needed.

Any thoughts/comments are appreciated.

__________________
-Jeff V.
Longmont, CO
SolarInterested

Avatar / Picture

Spam Stomper
Registered:
Posts: 1,001
Reply with quote  #3 
LucidBuddha welcome to our forum

Quote:
Originally Posted by LucidBuddha
... Is there a reason the inlet in the picture is at the bottom and not the top? I was thinking of pumping to the top so any drain back would get heat from the collector on the way down to the tank.

That's normal. I believe it insures that all piping is full maximizing heat transfer from the pipe to the water. Hopefully others will comment.

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

Avatar / Picture

Registered:
Posts: 2,239
Reply with quote  #4 
With an open-circuit collector, the idea with filling the collector from bottom-up, is that at the initial fill, air is expelled from the pipes, preventing vapor lock: the returning fluid flow takes the air with it, and as the flow falls into the tank, said air is expelled to atmosphere: the system is "primed". Now siphoning will occur, meaning that the weight of water in the collector will "pull" the feed along, thereby reducing the amount of head the pump has to deliver.

If the collector was filled from top-down, at the initial fill, water would drop down the tubes, and some of the air in those tubes would get compressed and thus prevent the water passing; some other air would manage to rise against the falling water, and would get entrapped in the system: this would cause "vapor lock", i.e. pockets of compressed air, preventing the tubes from getting filled completely.

As the collector started heating up, that air would expand and start producing all sorts of pressures, noises, irregular flows, and danger situations...

That device at the top looks suspiciously like it is meant to represent a pressure relief valve; on a drainback system it is not actually required...



G_H

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

Registered:
Posts: 43
Reply with quote  #5 
Thanks for the warm welcome and quick replies! 

That all makes sense to me so I'll fill from bottom up. Thanks and stay tuned!

__________________
-Jeff V.
Longmont, CO
eli

Registered:
Posts: 61
Reply with quote  #6 
just a thought but why wouldnt this work to have a drain back system with say 80' of pipe before it got to the top and 20' down to the tank. Pump it up and when the whole line is full turn the pump off and let it siphon back and have a free running system with no elect.  Just need to figure out how to stop it with a inline switch  
SolarInterested

Avatar / Picture

Spam Stomper
Registered:
Posts: 1,001
Reply with quote  #7 
Hi eli and welcome to our forum. A siphon will only work if the discharge is lower than the water level in the tank.

There are thermosyphon systems where the tank must be above the collector. See the following links for examples:

http://www.builditsolar.com/Experimental/ThermosyphonTest/PEXCol.htm

http://www.builditsolar.com/Experimental/ThermosyphonTest/CopperCol.htm

http://www.builditsolar.com/Projects/WaterHeating/ThermosyphonDIY/ThermosyphonDIY.htm

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

Registered:
Posts: 61
Reply with quote  #8 
Yes i agree with that. Just a idea to run the system with gravity and only elect to fill the system. Would need some kind of switch to let air into the line when the temp drops at the end of the day. Do you think this could work. Payback would be much faster with no pump using elect all the time. 
eli

Registered:
Posts: 61
Reply with quote  #9 
I would have my tank in the basement, so lower then all water lines and so the 20' rise on one line could create a suction with the 80' drop to create a self running system after the pump got all the water lines full. I understand the system would have to start filling from the 80' way and need to remove the air from the 20' drop before it could shut off and start running the other direction. just a thought and im not sure if it would be possible to get all the air out  
SolarInterested

Avatar / Picture

Spam Stomper
Registered:
Posts: 1,001
Reply with quote  #10 
No you will have to run the pump whenever you want to circulate water. The DIY drainback systems most folks here are building allow water to flow back through the pump when the pump is turned off. Also the return line from the panels to the the tank ends above the water level in the tank allowing the collector to fully drain.

http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm#Overview

__________________
Both temperature rise and airflow are integral to comparing hot air collectors
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics