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lmidgitd

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Reply with quote  #1 
I've been researching solar air heaters for quite some time, however I have not seen how you guys are tying multiple panels together. My system will have to have an underground run of ~15ft into my basement. I'll be planning on building four 4'x8' panels. 

Should I run one 10" insulated duct and feed all panels at the same time in parallel? If I do this, what if one panel is not to temperature due to shading when the snap switch kicks on? If the fan pulls air from one of the shaded panels then I'll be introducing cold air to the house. Running individual fans, sensors and ductwork will be expensive not to mention the amount of holes that will have to be cut into the house.

Any ideas or links to how people have handled this problem would be greatly appreciated.

Bert

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Reply with quote  #2 
I think that 10" may be enough to handle the airflow.

You could have the main snap disk at the output set at your chosen temperature. Have backup snap switches in each of the panels set at a higher temp. Enough that that they only come on if the temps get high enough to do damage.

The snap switches would be in parallel. This may be a simple way of doing it without being too complicated.

You could run the collectors  in series also if the duct-work  is big enough. 


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gbwillson

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Reply with quote  #3 
Hi Imidgitd-

Welcome! Where are you located? 128sf of collector(s) will give you an awful lot of cheap heat!

There aren't many multi-part collectors out there. I have a 4x16 collector that is made up of 2-4x8 panels connected end to end. I built it this way as there was no way a single 4x16 collector would fit up the basement stairs from the workshop. I also was thinking of the need to make the collector easier to manage as it has to be moved seasonally. Any future builds will be single piece, regardless of size. I didn't like some of the issues that a sectional collector has to go through. I just have to start my build outside early enough to finish before the weather changes.

So you are building 4-4x8 units. Why separate units, and what will be the final dimension once they are all connected? There are a few ways to connect units together, the simplest being screwed or bolted. My collector uses a couple of latches for easy disconnect before moving. 

Check Don's post #82 to see my latches:
http://simplysolar.supporttopics.com/post/don-cs-new-2x16-zeropass-collector-8071547?highlight=latch&trail=90

A few posts later he shows how he connected the sections. Biggest difference is his connections are for a permanent install, mine are not. Connecting sections can create a few headaches as the connecting faces must be smooth, strong and create a tight seal. 

As far as how to feed your panel(s), it depends on how the 4 units will be configured. Ducting the 4 units in parallel involves more work, parts, and materials. It will also likely give you LESS heat overall than a single large unit. Could you post a photo of where you plan to install your heaters and maybe explain some of the issues with shading you mentioned.

Greg in Minneapolis[wave]

lmidgitd

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Reply with quote  #4 
Thanks for the great questions.

I live in lower Wisconsin in a partly shaded area (Zip 53548). The house is 1550sq/ft with the front of the house facing to road due south. The bush underneath the front windows has been removed. I was thinking about mounting the panels to the top side of my deck railing (with supports) so that the rear of my house roof does not shade the panels. The large tree at the northeast part of the house has been taken down so that shade is no longer there. I do have a pine tree due south that will shade for an hour a day, but it's not too bad. The house is a ranch and the deck railings are ~5ft in height. It's a big deck so my sun angle of ~28° should be sufficient in regards to the roof not casting shade on the panels. I will need to double check that. The rear edge of my deck is shown by the gray arrows in the attached pictures. I've thought about putting panels under my front roof and to the left of my door in the frontal house picture. This would make routing the incoming/outgoing air much easier, but the neighbors might have something to say about that.

The deck panels would be a traditional double screen with the air inlet at the bottom and exhaust at the top. I was going to run an insulated underground air plenum into the house. (I saw a previous member had done that with only a 2°F drop)

I'm planning separate units so that I can remove them in the summer months that way I have view of my backyard in the warmer months from the deck. I'd use rubber weatherstripping to connect the panels if I needed to run them in series, but I was hoping there was an easier way of running the panels individually so that I don't have as much efficiency losses. Sounds like that is not the case. I'd have to have a variable fan setup to compensate for when all the panels are producing compared to just a couple panels producing, and plus electronically controlled dampers on each panel to shut down airflow to the panels that aren't up to temp.

Perhaps it'd be smart to just make a couple of panels at first to see what kind of output I'm getting before I get too carried away.

If the pictures aren't good enough I can take better photos tonight.

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gbwillson

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Reply with quote  #5 
Imidgitd-

If I understand your description, you want to have 4 separate 4x8 collectors mounted vertically on top of the deck railing. This would make the highest point of the collector roughly 13' above the surface of the deck. That's a heck of a tall collector mount. You want the units separate, or at least detachable from one another for easier moving seasonally. You want to duct the intake underground to the basement/lower level. How do you plan to bring the heat into the home? The top of the collector will be 13' above the ground and the ducts will attach to either the back or side of the collectors. That seems awfully cumbersome. Not to mention having the warm air duct fully exposed to the frigid winter winds the 15-20' to the house. Did I get any of that correct?

In ideal circumstances, a 4x8 basic two screen collector would produce roughly 4,000BTU's per hour. Compare that to a 1,300 watt electric space heater which produces 5,200 BTU's per hour. I say ideal, because every build is different, and you have a very tough situation for an install on your deck. 

A couple of suggestions... I like the idea of building two collectors, but build two 4x16' horizontal collectors, with one on the back deck railing, and the other in the front. As long as the unit looks nice and is removed seasonally it should be no problem with the neighbors. It does help to get them interested in what the heck you are doing. If you do build 4x16' units, you can split them in the middle as I mentioned earlier for easier transport. I mounted my sections on 10" pneumatic wheels for easy transport.

Consider a 4x16'ZeroPass-type heater design. It will produce quite a bit more BTU's than the same sized basic 2-screen. Expect double the BTU output, or 16,000BTU's per hour or more (More than 3 electric space heaters) from a 4x16' ZP Collector. Build one as you suggested until you have a better grasp of things. You can always build more, bigger, better...

The fun never stops!

Greg in MN
stmbtwle

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Reply with quote  #6 
Suppose you were to mount them all on an old boat trailer. Out of season just hitch up and move them out of sight.
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lmidgitd

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Posts: 6
Reply with quote  #7 
Great ideas Greg. Yes you have a firm grasp on what I was planning on doing. The 13' in the air and the problems that it would incur are what I'm apprehensive about. Not only insulating the input and return ducts, but also the wind the the panels will be introduced to. Actually you mentioned what I was thinking, which is a lower collector of 4 feet rather than 8 feet tall. I was planning on insulating a currently uninsulated cantilever this summer, and I was planning on running the ducts into the cantilever and then into the basement. My hope is that (hopefully this is the case) the excess heat will be stored in the basement and floors to be released once the panels stop producing.
lmidgitd

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Posts: 6
Reply with quote  #8 
Quote:
Originally Posted by stmbtwle
Suppose you were to mount them all on an old boat trailer. Out of season just hitch up and move them out of sight.


Haha, This would be great to do, but not in the cards. I'll be storing the panels in my garage over the summer.
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