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 1 of 4      1   2   3   4   Next
dbc

Registered:
Posts: 282
Reply with quote  #1 
I've been working on a new zero pass hot air collector.  I sure don't need another collector (the 4x8 turaround ZP did pretty well last winter), but I had some ideas I wanted to try out, so here we go.

The main goals of the new project are:

1) Little bit bigger, hence the 4x11 size.  A bit more heat would be welcome.  I concluded 4x11 is the biggest size that will fit inside my work area during construction.

2) Light weight, as light as I can make it without being too flimsy.  The collector will go in a somewhat sheltered location - where the 4x8 unit sits now.  it needs to be light so I can move it around during construction.

3) Simplified construction (yeah, right).  More on this subject below.

The new project will be a conventional 1-piece, 1-way ZP.  Transit time through the enclosure

The frame is constructed from standard 3.625 in. metal stud track.  Sections of metal stud will nest inside the track frame to join the sections and where things attach (mounting brackets, glazing cross-bars, handles).

The back sheet is 1 inch polyisocyanurate insulation board, with aluminum sheet metal panels glued/taped on where something has to attach (ducts, snap-disc bracket, j-box).  I plan to forgo wood reinforcement inside the frame or any cladding on the back.  I may live to regret that decision, but I'm trying to push ultra-light to the safe limit.  More polyiso will fit into the frame sides, with wood blocks glued in to support the screen frames.

I plan to use aluminum screen frames (with metal corners), with high-temp foil tape covering the splines.

The idea that really spurred me into action was to build the components beforehand, and join everything together quickly, at one time.  The previous projects always suffered the most damage from banging into things while moving them around half-built.  The bigger size would only make it worse.

Time for some pictures.  Here are the end pieces.  They are 4 feet long (high) with 6-inch legs.  The corners are riveted:

2) End pieces, 051419.jpg 

Full 10 foot lengths of track will fit between the corner legs, glued and riveted to inset pieces of stud, to create the 11 foot length.  I bent the curled edge of the stud pieces flat, so the back sheet will lie against the frame.  Here are the pieces loose to show how it goes together:

1) Corner assembly, 051419.jpg 

The stud piece is longer towards the center because it also will serve as reinforcement for the glazing cross-bar brackets.  This photo is of the upper right corner.  The upper left corner piece will also span to the left-side mounting tab for the frame.

Here is the assembly, dry-fit:

6) Top right corner, 051419.jpg 

Here is a smaller stud section that fits in where the center glazing cross bar will go.  It's glued in, but will also be through-bolted when the cross-bar bracket is added:

4) Center insert, 051419.jpg 

The end pieces have handles bolted through inset stud sections and a small metal plate:

1) End pieces, 060819.jpg   

2) End pieces closeup, 060819.jpg 

Here is one of the collector mounting tabs installed on the top piece to tie the collector to the mounting frame on the south wall:

3) Mtg Bracket, inside, 053019.jpg   

Finally, here are a couple photos of the completed top and bottom frame pieces, with the splicing stud pieces riveted, mounting tabs on the top, two handles near the center of the top, and cross-bar brackets mounted to top and bottom.  The cross bar angle brackets have a 1/8 inch aluminum flat plate inserted between the angle and the collector frame, so the future glazing hold-down angles can get into position without interfering with the cross-bar brackets:

3) Top and bottom, 060819.jpg 

4) Top and bottom closeup, 060819.jpg 

Next up is the back sheet assembly.

dbc

Registered:
Posts: 282
Reply with quote  #2 
I made some progress on the back sheet too.  Most of the 'office staff' is out of town this week, so I occupied the front porch area to do some layout work.

Here is a picture of the completed frame.  The corners are just loose-fit, the back sheet needs to go inside before I can rivet the corners.  You're looking from the top right corner:

2) Frame 02, 061519.jpg 

I cut four 12-inch square pieces of aluminum sheet, with 6 inch holes for the in/out ducts.  There will be a plate on front and back for each duct port.  I've tried everything from a utility knife to a saber saw to cut these holes before, and usually made a mess of it, so this time I drilled a bunch of little holes around the perimeter, and finished off with a half-round file.  It was slow going, but I ended up with a still-flat sheet and a smooth hole:

4) Plate + duct, 061519.jpg 

When I install the duct sections, I will cut 'tabs' on the inside end, fold them flat, and glue + screw to the sheet.  This is the same technique I used last time; it seemed to work OK.

I also made some smaller plates with a 1/2 inch hole in the center for the snap-disc bracket (inside) and a plastic j-box immediately behind on the outside.  I glued all the plates to the polyiso with silicone and taped the edges with Nashua brand 324A high-temperature (300 F) premium foil tape:

1) Backsheet with alum pates closeup, 062119.jpg 

To make the 4x11 back sheet, I glued a 4x8 and a 4x3 piece end-to-end with silicone.  That's a strip of wax paper underneath the joint.  Here's the 'high-tech' gluing station:

2) Backsheet glue-up, 062119IMG_0888.jpg 

I got a nice, tight glue joint by pushing the CMU blocks tight to the end, then giving them a gentle kick.

After the silicone cured for a day, I covered the joint with more 324A tape.  Here's the flip side (the unpainted side is the back):

3) Backsheet, taped, 062110.jpg 

It came out pretty solid; it feels like one piece.

I'm going to wait to attach anything to the back sheet until after it is installed in the frame.  I figure it will be easier to get it in flat without stuff sticking out.  The next part is sort of the moment of truth for this build - whether I can put the back sheet in the frame and finish gluing and riveting the corners without wrecking something.  We will see.

gbwillson

Avatar / Picture

Super Moderator
Registered:
Posts: 2,352
Reply with quote  #3 
Nice update Don!

It's more than a bit hard to think of solar heat being the first day of summer. The last two years I had thought I started my build with plenty of time before heating season begins. And we either had a very early fall,(no outdoor paining) or more health issues. So I'll probably try and start this year next month after I finally get back to work. I wanted my last collector to be built without anything but insulation on the back to keep it as light as possible since it has to be moved twice each year. And yes, they DO take a beating each time they are moved even after they are fully assembled. The reason I added a thin plywood back was because the entire collector is exposed to the strong winds out for the North. I was afraid the wind would deflect the large panel enough to dramatically alter the flow inside the collector. Too bad you had to limit yourself in the size of the unit. I want my new collector to be a single 4x12, which won't fit up the stairs from the basement workshop. 

Another issue I had with the stud track frame was that I attached a large 10" caster to the bottom of each 8' section to help with seasonal moving. It really does help as no lifting is required, but maneuvering a 4x8 collector section with a single wheel must be like learning to ride a unicycle, especially if it is windy. Another issue was that the wheel was an afterthought, so the frame, while reinforced with plywood around the entire perimeter, simply isn't strong enough to resist the forces that are trying to twist the frame where it attaches to the caster fork. A lightweight panel with the proper reinforcement would be a big help. As it is, the wheels allow me to roll the sections into position and simply lean the now assembled collector back to the proper angle. 

Your reinforcement plates for the openings are very nicely done. I wonder if I could somehow use a few thin straps attached to the backing insulation to keep it  from deflecting??! Another idea was to add an additional inch or two of insulation to the back not only for stiffness, but to better insulate against the frigid winter winds. I'm just not sure about storage and moving durability with noting but foam insulation for the back of the collector.

Again, great to see the update on the build and keep posting as you go along. I check in every day, even during the summer where heating is the LAST thing I'm thinking about.

Greg in MN

PS:I remember how flimsy the stud track frames were before you stared putting everything together.


dbc

Registered:
Posts: 282
Reply with quote  #4 

Thanks, Greg.

I doubt I could do what I'm doing if the collector was more exposed from the back, like where you have your 4x16 unit.  Being close to the wall and under the roof overhang, I'm hoping I can get away with it.  Time will tell.  I skinned the back with aluminum flashing last time, which worked really well at protecting the foam from dings and added some stiffness; it was just expensive.  I can still do that if I have second thoughts.

I had a little bit of the 20 inch roll left over from last time, which I am using to make 3 straps to span back of the frame, top to bottom.  The main purpose is to keep the frame from spreading when I pick it up. I cut 6 inch wide strips, which I bent over twice to make a 2-inch wide straps.  I was originally planning to make these a single thickness, glue them to the back of the polyiso, and rivet them to the frame after the back sheet was in, but then I thought they might tear the foil surface.  So instead, I doubled them over for added strength and decided to fasten them to the frame afterwards on the outside.  I'm bending the last one right now; I'll post a picture in the next update.  I also have some 12 inch long, 20 ga. Simpson straps to triangulate the corners.

Fortunately, I don't need to move the collector seasonally; I'm mostly worried about damage during construction.  I'll need to make a new larger cover before I install the collector permanently though.

That's a good idea about the caster.  I wonder if some smaller 'training wheels' at the ends would help?

Bert

Avatar / Picture

Registered:
Posts: 541
Reply with quote  #5 
That is looking good 
I think that the efficiency should be better with the air going straight through with a better flow.
Looking forward to the build.


__________________
Bert K.
Michigan

https://www.youtube.com/user/1thinkhealthy/playlists
dbc

Registered:
Posts: 282
Reply with quote  #6 
Thanks Bert.  I agree, airflow should be less restricted with one-way.  I guess the other question is whether I get enough temperature increase, but overall I hope it's an improvement.
gbwillson

Avatar / Picture

Super Moderator
Registered:
Posts: 2,352
Reply with quote  #7 
I think it's good to have both designs in case a certain location is limited. But given the choice, I agree that moving air in a single direction is more efficient. Being Don's new build is in the middle in size, I'm interested in the performance numbers compared to an 8' and 16' collector. My very first ZP had an 8' collection area, but had the manifolds as extensions. The performance numbers were okay, but you really didn't need to have a lot of airflow as the temps didn't rise much. At most CFM's tested, it compared far better than the 2 screen, but only at higher CFM's. I think the screen gap was also a bit narrow during tests as well. 

If I didn't have to move my unit seasonally, I'd have a single 4'x24' or even 4'x32'. A single unit of that length would need an ENORMOUS amount of air to keep it efficient. ZP collectors with 6" ducts need a minimum of 400 CFM. A 24' or 32' unit would need at least 8" ducts and more than 800CFM's of airflow. Given the limited amount of hours a collector runs in the heart of winter, say 4-6 hours it might not be a problem except early and late in the season where the available sunshine adds too much heat to a home. Not a huge problem if you are dumping the heat into the basement. But to add that much heat to the main living areas will raise the house temps to what many find more suited to summer, cool drinks and AC.

Bert, do you recall the normal temp rise on your ZP? My 16' unit had a deltaT of about 35-40 most of the winter with a minimum CFM of 400. 

Greg in MN
Bruce

Registered:
Posts: 141
Reply with quote  #8 
Interesting design and outstanding workmanship!  I will follow this build to see how it works with a 1-way pass.  I will wait to see the placement of the ducts, orientation of the glazing (twin-wall horizontally?) and other details you will post.  Keep up the good work and keep us posted.  Inquiring minds want to know! ;-)
Bert

Avatar / Picture

Registered:
Posts: 541
Reply with quote  #9 
Quote:
Bert, do you recall the normal temp rise on your ZP? My 16' unit had a deltaT of about 35-40 most of the winter with a minimum CFM of 400. 


I think it was around 40.

My big collector would come on with less sun then my small collector.

__________________
Bert K.
Michigan

https://www.youtube.com/user/1thinkhealthy/playlists
dbc

Registered:
Posts: 282
Reply with quote  #10 
Bruce - The ducts will be at center height.  You can probably get an idea from the earlier photo of the back sheet.  I can get twin-wall in 4x12 size, so I plan to trim length to match the box and install it as one piece, with the channels running horizontally.  I don't think this is recommended by manufacturers (Palram, etc.), but I did it this way twice before and it seems to work OK.  I didn't seal the ends, although they were covered by the angle hold-downs, and there was a gasket between the twin wall and the frame.

Greg - I would like to see a 4x32 with 800 CFM.  That could heat a small commercial building.  I think your system of routing the heat to the basement is a great idea.  The basement provides somewhat of a buffer, and even some storage capability if the basement is insulated (even if it isn't).  I don't remember - do you have transfer grilles in the 1st floor, or does the warm air just heat the floor?  I assume the floor joist cavities are not insulated in the second case.

Bert, Greg, I saw about 35 F increase on both the 4x8 turnaround and 2x16 2-section collectors with air flow about 200 CFM (4x8) and 180 CFM (2x16), so temp rise is a big unknown with the new project.  I will probably be using the same fan; might need a damper or speed control if output temps are too low.

I made more progress this week.  I should have another construction update tomorrow; have to get my pictures in order.
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics