Solar Kajigger

[GeeMac]

I made an experimental kajigger today.

I saved some tin cans and cut the bottom out of each one. Then I joined them together to form five tubes which I painted matt black. Then I scrounged some scrap metal siding and cut chunk to fit the plywood backing (24" x 24").  I painted the metal black too, then screwed it to the plywood. Then I attached 5 columns of cans and hung it in the back door window, which faces south. It's a sunny day and it didn't take long to start working. The metal backing and the cans became warmish-hot causing a vertical draft through the columns. As the air passed through the cans it was heated. Heat rises so it began to suck in the cooler room air from below and ejected the heated air from the top. Voile' -  Free heat.

Costs

24x24 scrap of 1/4 plywood - $0.00

Sheet metal siding         - $0.00

Cans                       - $0.00

Paint                      - $3.49

                             ___

Total                        $3.49

[FishbonzWV]

Good job GeeMac,

I love the word 'free'. :-}

[zap]

I wonder how many people will Google "kajigger"!

[Basil]

Could not help my self. Google sickness.

Kajigger: an, unspecified object, thingamajig

[wooferhound]

You have inspired me to make one for my only South Facing window.

I googled kajigger before I clicked on the story.

 

[gizmo]

I wonder how many cans you would have to stack to make enough flow to drive a PC powersupply fan? See where I'm headed? Talking milliwatts here, from a gutted PC fan.

[windy]

Years ago, I made a solar panel using three inch galvanized stove pipe and painted black. I covered the panel with plastic sheeting and put a fan on it to blow air through the pipes. It too was an experimental panel, but it produced a lot of heat. The only problem I had with it was when the fan started, the air would leak out of the pipes and the plastic would bow out when it got hot. Could never keep the plastic tight.

[windstuffnow]

  I guess I'm gonna start saving cans again... I have a south facing window in my battery room and just put up an aluminum sheet painted black about 2 weeks ago.  It's quite amazing how hot that sheet gets.   It made the room kind of dark, it's a big window - 4ft x 6ft - but it will heat the back room in a couple hours of sun and filters in to the house all day.

  I love the can idea... gotta try it !  Thanks for sharing.

  I've been collecting 8ft flourescent bulbs as they burn out, I've just about enough to cover an 8x8 area.   My plan is to tape them off close to the ends and sand blast through the glass removing the end caps on both ends.  Clean them out carefully and use black pipe inside them to heat water.   They may work well as an air heater also with strips of black sheet inserted.  Being careful with these being the key point while blasting and cleaning.  We'll see how it goes anyway...

.

[Norm]

I've heard of cutting the tops from glass

bottles with a a regular glass cutter....should

work on fluroescent tubes also....?

[zap]

Keep in mind the fluorescent tubes are filled with mercury!!!

[jimovonz]

If I get you right, you are hanging your 'array' of cans inside an existing window with the aim of heating the room. I don't dispute that you are getting warm air out of the top of this contraption but do you really think there is a net gain to the amount of energy in the room compared to having nothing in the window at all? Where do you think that the extra energy is coming from? Where is it going when your cans are not there? You are just concentrating the energy captured (already in the room!) into a smaller space creating a local 'hot spot' rather than letting it disperse over a wider area inside the room. Your typical south facing window already does a pretty impressive job of capturing most of the energy that falls on it and transfering it to the building containing it.

If you are looking to increase the temperature of your home using solar then you need to increase the capture area. This method covers up a perfectly good capture mechanism with another that can only ever capture what you already have... Enclose your contraption, put some form of transparent front  on it and place it somewhere that doesn't shade an existing window. Duct the heat you capture inside then you'll have a net gain.

[GeeMac]

You might have to improve it a bit. This is still in my experi(mental:) stage. A better way might be to put sides on it and a glass front. Then an intake hole in the bottom and a hole in the top. Thicker metal other than some siding will work better as well (I'm thinking something like a door panel from an auto wrecker might have more mass and therefore absorb and hold heat better). However in my case weight is a factor as I have hung the thing from the doorframe. Carry on having fun folks. Life is too short to waste on anger and stress.

[GeeMac]

Great idea. Ultimately, I want to get a solid metal backing and run a liquid through some copper pipes that would be attached to the backing. I also want to try diverting the hot liquid through an old car radiator that would be in my basement.

Being old and on a pension is a great motivator. My parents used to call this economizing. Personally I just like to beat the power and gas companies out of my limited dollars. heh heh heh.

[GeeMac]

You may very well be right, but the black surface tends allow for more solar input. I do not expect the thing to heat my house but it might suppliment the heat and assist in reducing the heating bill, which can sometimes be over $300.00 for a month. Local taxes are $200.00 amonth and then there are the bills. After that there isn't much for food. My pension is only a bit over $800.00 a month, so you can see why I am motivated to do this or any other inexpensive project that will fight back.

[spinningmagnets]

GeeMac, I am a fan of using what you have, and then improving your (left-handed Metric Frammis?) from there.

I would guess you are getting a significant net gain with your inside-the-window collector compared to just letting the sun shine on the floor and airspace. The black color will absorb more heat than light-colored carpet. The vertical tube shape will direct flow (as much as is possible) in the room much better than warmed air slowly rising near the window in a turbulent flow.

Rising air in the columns forms a "no-moving-parts" air pump, and GaryGary has shown many times that you will get more total heat collection with higher flow past the collector. A slow hot collector is less good, a fast warm collector is best.

Once the wife sees that there's actually a real benefit to your tinkering, she will be more patient with your junk collecting and RE improvement efforts.

GaryGary's builditsolar.com site lists Polycarbonate (270F capable) or glass as the best solar air-heat collection box lens, so I have acquired two large glass windows from house demo's so far. The lens is only to seal the box to reduce heat loss back to the outside air as the inside-the-can air is rising. Also if you have a glassed-in box, you really don't have to get a perfect seal around each cans edge.

These collectors are in my top ten best things to do. You may not be able to bash several new windows into your south wall, but you can have several "near free" solar-heat boxes that you pull out of the garage in the winter, and duct them to the window.

[zap]

Free or nearly free is always good.

I tried a can collector but it took time.  I came up with this which also works well and is a quick build.

This is foil faced foam board, sometimes called Tuff-R.  Mine was free from building sites.  This is the side facing the sun, painted black using barbecue spray paint.

Here's the back, facing into the room.  The slots are covered with black plastic trash bags.  They were originally intended to act as reverse flow constrictors.  They work OK but could work better since they don't like to stay 'flat' but as they are now they add some privacy.  I figure this set up might add a smidgen of R value since the only covering to this window is aluminum blinds.  I've seen 130°F in the collector during the winter once the sun gets lower in the sky and the heat pours out!  As windstuff pointed out, you lose most of the light.



You could probably do this with thicker cardboard also... I might have to try that.

If you like cans and want to try liquid...





I've been playing with this since last spring.

Two aluminum cans silicon'ed together and spray painted black.  The reflector is an old snack chip bag turned inside out glued to a 5 gal. bucket half from old VAWT experiments.  The bag has a clear coat applied that started turning opaque in the sun.  After a few weeks this coat finally started flaking off.  Once it was gone the thing really started reflecting and the heat came up a lot.

During the summer, a few hours will bring the water up to 165°F.  Yesterday with the temperature at 49°F and a bit breezy, two hours of clear sky gave me 24 oz. of 127°F water.  Tea anyone?  I've also tried using 2 liter plastic pop bottles, dark green, which also heat up quite well.  I need to get some plastic spray paint for the pop bottles and give that a try.

The cat is naturally black, no animals were harmed producing this post.

[GeeMac]

Thanks for the very encouraging words. It should be possible to have a 'no moving parts' liquid version of this. The heated liquid would naturally want to rise and it could be passed through some sort of radiator device. As long as the bottom of the circuit does not pass lower than the lowest point on the unit the cycle should occur for free.  Ain't mother nature wonderful?

[jimovonz]

Your black surface may well absorb more energy than the carpet or what ever surface the majority of the light coming through the window initially falls on but any energy not captured at that point will be reflected and captured by something else. There may be multiple such reflections before all the energy is dispersed but in most situations precious little will make it back out the window it came in through. You have to realise that once the energy is in the room (which is where your collector is) unless it has a path out, it stays. You don't need to construct some fandangled mechanism to capture what you already have. You are better off taking measures to make sure you keep what is already there through improving insulation etc. If you have been inspired by the likes of those that use big black barrels (of significant thermal mass - trombe wall) inside the home then this is something different. In this case the thermal mass acts as a storage device that is utilised to provide heat at some later stage when the heat from the sun is no longer available.

[Bushwhacker]

Food for thought GeeMac...

The model T ford did not have a water pump and relied on convection to cool the thundering 12 HP engine. Think about how many model T's have been in how many parades moving along at walking speed without overheating. Convection does work, and well.

Cheers!

BW

[la7qz]

It took old Henry some time to figure out pumps. The model T also didn't have a fuel pump the first couple of years. The fuel was gravity fed from the tank just in front of the windshield. They used to stop on inclines of more than 5 degrees when the carburrator was above the tank. Drivers would routinely reverse them up hill to prevent that from happening...

Owen

[spinningmagnets]

In the "Maltese Falcon" it was a "Dingus", and in "North by Northwest" it was a "MacGuffin".

Ol' Man Ford never missed a penny on purpose. He specified that parts being shipped to the Model T factory had to made from wood slats of a specific shape and size with holes in certain spots. When the shipping crates with parts inside arrived, they were carefully pried apart, then the wood slats were screwed onto the beds of the trucks on the assembly line.

I don't understand how a black thing and a white thing right next to each other in the exact same sunlight will be two noticeably different temperatures. But, I have seen it in parked cars, and military airport runways (made black to be hotter so birds will stay off it at lunchtime when major operations are scheduled...)

I even saw a dark swimming pool that was warmer than the light blue ones (I was cleaning pools part-time, and none of them were using a heater)

I also agree with poster about sealing cracks and adding more insulation.

I haven't yet found a solution I like about covering windows at night, they are a terrible heat sink (even my double-paned windows)...one guy on Gary's site put a couple layers of clear bubble-wrap over the insides. Worked very well (on infrared sensor) but won't pass the "doesn't look goofy to the wife" test.

"My body went to prison, but my hair got the electric chair" -Don King

[wdyasq]

Jim,

You need to quit confusing these folks with the truth ....

In fact, the collector will heat the glass and more heat may be lost through the glass than normal while the sun is shining. Of course, the 'flip side' is there too. The back and what ever insulation it adds may keep the heat in a bit better at night. But, like you, I think the 'apparent gain' of feeling the heat is the boost felt, not any real gain.

You can't get any more blood from an onion than it has.

Ron

[ElSenator]

Take a look at this section of GaryGary's website...

http://www.builditsolar.com/Projects/SpaceHeating/Space_Heating.htm

Then have a look at this, too

http://www.engadget.com/2007/04/30/diy-solar-heater-constructed-with-aluminum-cans/

http://blog.hemmings.com/index.php/2007/04/26/almost-free-garage-heat-just-drink-a-lot-of-soda/

Pretty huge return on the cost...

Lee