Solar Heater

Step 6 Install Glazing and Vent Valves

Install glazing and seal it. I used corrugated PVC; it comes in 8' x 24" sheets for about $12/sheet (2007 pricing.)

On the top vents in the building you'll need to put a flapper valve made from plastic sheeting or a trash bag, this keeps the warm air from leaving at night as the heater would work in reverse. Also put some screen on the vents to keep most of the critters out and to keep the plastic valves from sucking into the vent.

Extra notes
Using recycled wood and some on-hand hardware, I spent around $100 for this; now I'm enjoying free heat.

Ducting with a fan and a thermostat switch is what they use on commercial versions installed on homes. That works well for precise heat control. I like convection, no moving parts; and I will just close the vents when the weather gets warmer with some cardboard stapled to the wall.

Comments

[crazylikeacharger]

can anyone direct me to where i can get some of the pvc sheets like the ones used in this. i want to upgrade

[cv11njrep]

PVC Sheets at Home Depot or Lowes should work for crazylikeacharger

[Greencrafter]

Lowe's sells Tuftex. It's is advertised to be perfect for extreme temperatures of 270 degrees F to -40 degrees F, 100% UV protected and hail resistant.

[bretgillian]

Home Depot has them. Go on their website and search for "Suntuf 8 Ft. Clear Roofing Panel".

[crazylikeacharger]

if i got to home depots website i search and only get the flashing for the sheets not the actual panels

menards has some panels but the ones they call clear are more like bathroom glass and the only other ones that would work are smoke colored and i dont think that would allow all the light waves in to the heater and therefore may not allow it to heat as much

[jefeweiss]

Based on what I have seen with similar designs, you could probably get big gains by using sheets of foam insulation to insulate the sides and back of your heater. I recall seeing a design that was used to heat a church and they discovered that this made a big difference in the temperature of air exiting the box.

[robbtoberfest]

Double glazing and insulation on the sides works for improvement, but insulation on the back won't do anything because the heat energy is going into the building through the wall too. Unless that energy is reflecting back out from the wall to the outside.........hmmmm; I don't really know.

[jefeweiss]

If the wall behind the panel is insulated, then a lot of the heat that is going out the back would actually be radiated outwards along the outside of the wall. Insulation in the wall would keep the heat from going into the building. If the wall is not insulated, then the heat would indeed go right into the building. Of course this would cause the wall to lose a great deal of the heat when the sun wasn't' shining. IIRC the designs that saw for the solar heater used by the church that I was talking about above were actually not attached to a wall, they were tilted at an optimum angle to collect the sun. They used 6 inch thick! polyisocyanurate foam board insulation on the 5 sides of the box that were not glass.

[Greencrafter]

I agree with you jefeweiss, and the polyisocyanurate foam board has a higher R-value than foil faced styrofoam. I have only been able to find 3/4" for sale at Lowe's near me. I read an article last week where someone was using 6" polyisocyanurate foam board in Alaska. Any insulation is better than none.

[crazylikeacharger]

i built one last year based on this design last year and i have noticed a few things. my unit is a 5' wide by 4' tall unit to help heat my 2 stall garage. 1. i have put a few holes in the side to vent the hot air out during the summer but i still got alot of heat entering the garage so i removed the storm windows i used so it isnt sealed during the summer. 2. if you use a fan to help push the air in you can actually get a garage pretty warm. 3. i am going to use solar power panels to power my fans so that they will kick on when there is enough sun to heat the collector so its completely automatic

[avid0g]

You may need to provide some shade for the collector.  The summer sun is higher in the sky than the other seasons, so an overhang to provide shading of the collector during the summer season should still allow full solar heating during the winter season.   Another possible problem is if the collector has concrete or asphalt in front of it; these can reflect/emit heat into the collector even if it is shaded...   Good luck!

[gtgilbert]

I'm interested in this project, but I don't have enough space to get a big enough capture area from the cited article. Would I be able to increase heat capture if I used multiple layers of the window screen a couple of inches apart?

[avid0g]

 "...I don't have enough space..."   I think part of the appeal of this particular project was that the back of this panel was the house, reducing the need to insulate the panel back.  However, if properly insulated, you could mount solar panels suspended vertically above the snow on your roof.  Snow can be an excellent solar reflector, concentrating energy on the collector, but you don't want it to cover the panel face.  Keeping the panel vertical, and suspending it in the air will minimize snow accumulation on an inaccessible winter roof.

[BobDody]

The hot air is going to rise.  You need to stir the air for it to pick up more heat before exiting the top of the box.  One way is to have the interior wall not be just the existing siding of the house but add corrugated tin roofing, installed with the waves horizontal, and paint it flat black for maximum absorption.  FWIW

[avid0g]

I think the big idea behind using screen is that if the screen is stretched across the air stream, All the air must pass through the screen so heat transfer is excellent.  No stirring required.

[island_hackster]

Check out You Tube for pop can heaters. If need be, you could even add a couple mirrors to concentrate rays. Also, that sunhotbox (posted below) looks like it would be a great option for you.

[robbtoberfest]

Nope, that won't work. Area of collection is very important; more screen layers in the same area doesn't improve heat output on this system. That only way to get more heat is to tilt/angle the heater, but then you have problems with summer heat control.

[raymccullie]

Reminds me of our hot water when I was a kid. My dad built something similar with a wood box and glass cover. Small copper pipes ran out of the tank, through the box and back. We had hot water 3 out of four seasons. And the pipes never froze.

Do you have any (water) leaks now that you've used it awhile? And how hard is it to shut off in the summer?

 

[robbtoberfest]

 No liquid here, just air. Yes I close the vents in the summer sometimes.

[raymccullie]

Sorry, I meant leaks as in rain getting in from outside.

[wsecomp]

Has anyone thought of adding suspended piping, with or without a reflective background?  Some heaters I've seen have pipes (not sure if metal or PVC) with about a 2-3" (51-72mm) gap on top and bottom with a v^v^v^ style reflective material (foil-covered cardboard?) behind it to reflect onto the back of the pipes.  It seems to me that this would be a "heat concentrator" of sorts, where there is still air flow around the pipes, but it would raise the temp of the pipes, and therefore warm up the air in the pipes even more.  The pipes seem to be spaced 4-6" (102-144mm) apart horizontally.

For this design, I would imagine that the length of pipes would be about equal to the space (maybe an inch or two less) in between the top and bottom vent holes.

[buteman]

If the design was slightly different I think it could be used for cooling in the summer. At the top I think that you could have a flap which was pivoted horizontally through it's center. In the winter the bottom would seal against the front of the frame and in the summer it would seal against the back. In the winter it would be as at present. In the summer air from the bottom of the unit would rise to the top and be expelled into the surrounding area. As it rose it would be slightly reducing the pressure in the room. This would cause air from outside to be drawn into the room at the top. The hotter it got the faster air would be circulated.
Well that's the theory if I have it right.

[robbtoberfest]

 Maybe a vent to redirect the air into the attic during the summer, I'm just brainstorming here. That reduced pressure would need a return vent in the house to let that fresh air in.

[buteman]

Here in the U.K the attic space usually has lagging on the floor so the roof space itself get very hot in the summer. This would mean the air in the panel would have to get very hot before it started to rise into it. Also the roof would need a vent in it, best near the top to allow the hot air to escape.

That has given me another idea. Why not use that heat input to the roof space to be used. Have a vent in the roof which can have a variable size exit and allow air to rise from inside the building at the same time allowing colder air in from low down in the building. A cheap air conditioner? Could even have the vent controllable by some thermostat system  if it was good enough.

[robbtoberfest]

 That sounds testable with some flexible ductwork. 

[buteman]

Well I will have to try it out, when we get some sunshine

[tgrundle]

As an idea for someone to try, what if strips of black plastic were placed against the wall under the netting with sections of the white wall behind showing like the stripes of a zebra (which they use to create air movement next to the body) to create currents of air to move through the netting. Also if you make it deep enough you could put a blind inside just behind the glass with the cords pulled inside so you could close off the light during the summer.

[robbtoberfest]

You know, I haven't had any summer heat problems in the garage. I don't even close off the vents anymore. The sun is high enough over the roof during the summer that it barely affects the heater.

[Matt4_16]

I like it but wouldn't you lose heat in the winter? with holes in the walls?

[thalden]

Remember, there's a giant glass window on the other side. The whole thing is really "inside." This works even better in the winter, actually, since the sun is at a lower angle and hits the wall more directly. See the comment in step 6 to understand how to close off the holes when necessary.

[jdix]

well thaught out, and my fave...simple, the screen, the screen is the key.

[jspence1]

What about a solar heater mounted somewhere besides on the wall? Many people don't have a southern wall but may have southern facing roof. Any ideas on how to pump the hot air (through some kind of duct) from and to the room? Maybe a solar powered fan? That would eliminate the "huge hot area on the wall". Of course the ducts would have to be insulated too.

[crazylikeacharger]

run ducting to the flow for the inlet and then have a fan pull air out of the heater toward the floor and you should be fine

[TheRevJester]

Without some system of forced air or somehow getting cool air from the bottom and warm air out the top, this system would no longer work passively. The air in the top part of the room (from the bottom of the panel to the ceiling) would quickly become the same temperature and cease to pull in the air from the floor and would stagnate. With a small fan, this could be remedied, but one of the beauties of this system is their passivity.

[robbtoberfest]

Roof would work, that's a whole different project with waterproofing, etc. It will have better performance on the roof, but summer heat would be a bear. You would have to cover the heater with something when it's hot. A water heating system on the roof is practical though.

[crazylikeacharger]

one thing you can do that should turn the heater into a cooling system for the summer is to have 2 openings near the highest point of the heater (capped off so heat doesn't escape during the winter) that during the summer you have open to let the hot air rise out of the heater. The air in the rafters of the garage would go into the heater, become hotter and be vented out of the heater into the open air above the garage thus causing airflow and eventually moving the air near the cool floor up higher into the garage

[TRIKER]

I get the holes at top to let the heat rise and go inside but aren't the holes at the bottom, being the same size as the top, pulling the cooler air out and therefore also taking some of the heat with it. I have a solar heater made from cans already working but too small and your idea seems like a much better idea. Thanks

[TheRevJester]

Your question is addressed by your own comment. The key is that the room is generally large enough to have thermoclines, or air temperature differences between the top and bottom of the room. When the sun is hitting the collector and heating it, cooler air near the bottom of the room is drawn into the collector and heated, blowing into the room near the top by the action of thermo-siphoning. This siphoning works so long as the top flaps allow air out of the collector, otherwise hot air stagnates at the top of the collector and no air is drawn into the bottoms because the air stops flowing. If the room reaches the temperature of the collector (that could be HOT!) then there wouldn't be enough of a temperature difference in the room to create a thermo-siphon and the circulation would stop, but without either a very small room, a very inefficient collector, or a super-insulated room, or some combination of those factors, it's very unlikely to occur.

[deputyjones]

Good idea MiniMoose. I was thinking one might want to add a fan to the building to help circulate that warm air through the building, but that idea might accomplish that.

[robbtoberfest]

Great ideas, I might still modify it for cooling.