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It is really simple and cheap to build DIY solar panels for supplemental home heating, and it heats the air directly.
The most interesting is the fact that collector is almost entirely constructed out of empty aluminum cans!
Housing for solar collector is made of wood (plywood 15mm), while its front is 3 mm (0.12 inches) Plexiglas/polycarbonate (you can use tempered glass as well). The back of the case set is made of 20mm rock wool (or styrodur) as insulation.
Solar absorber is made out of beer and soda aluminum cans, painted in matte-black paint resistant to high temperature. The upper part (cover) of cans is specifically designed to provide more efficiency in heat exchange between the cans and the passing air.
details on : http://solar.freeonplate.com/solar_panel_DIY.htm
Double/triple glaze and well insulate it and have a vents at the top and bottom to restrict air flow during the day and open them up at night/when required, like an electric storage heater?
Mike
I live w-a--ay up north in Winnipeg, Canada and it gets down to -40c as well...
But I noticed my insulated, metal back door, with a outside storm door is warm, sometimes hot, to the touch even at real low temperatures.... [it faces South/west and is painted dark for that purpose]..
I wonder if I can rig something to attach to the door? This way I'm not drilling trough insulated walls etc..... and can just replace the door if it doesn't work as well???
I have a couple questions though.
I live in Canada, and we get temps down to -40. Would this still put out "hot" air?
I was also thinking if you put a reflective surface like a mirror or space blanket on the back of the inside of the box, you could push the temp up even further. Is there any reason you wouldn't do that?
I would be interested in knowing if you were to slow down air movement in the cans by using smaller holes so the air had more contact (wrong term I know) with the sun to make the air hotter, could you push the performance even further...
Yes, the faster the air flows through the can tubes, the less time there is to transfer that heat. And, as someone else mentioned there is only just so much total heat available [limited by the size of the collector], so "throttling" the air flow is sort of a trade-off on the amount of heat transfered to the room versus temperature of the air going into the room. The greatest AMOUNT of heat [not temperature] transfered from the collector to the room results in the greatest efficiency.
There are a couple of advantages of not using a too slow air flow rate:
1. If the flow rate is way too slow it may allow enough heat build up in the collector to damage the insulation, OR even cause a fire!.
Years ago [back in the 1970s] I read an article where this type of solar collector, in new houses somewhere in Colorado, that were vacant and waiting to be sold, and had the air circulating blowers turned off, allowed the "stagnated" air in the collectors to get so hot that the polyurethane insulation in the collectors caught on fire, resulting in roof fires on those houses.
2. IF the air flow rate is TOO slow, then you will only get the amount of heat that that air can carry, whereas a higher rate will allow the collection of more heat and adequate airflow will be able to carry all the heat collected.
Also, "tseay" [prior comment] made a good point about prevention of heat loss from the heat INSIDE the collector by creating a "dead" airspace at the glass interface.
This is commonly referred to as "double glazing" which creates a layer of non-circulating air which acts as an insulating blanket to reduce heat transfer "back" through the glass to the atmosphere.
Double, or even triple, glazing is a great efficiency improvement for any thermal type collector.
2. There is no space between cans for light to pass, so mirror in the back of the cans has no purpose (there would be no light to reflect from behind...). If you have spare mirror and open space around solar panel (and if it is low mounted), you can position mirror near it and reflect additional volume of light on panel. There is video on Youtube where some guy test this, and it have couple of degrees temp. increase...
3. "could you push the performance even further" - this is true in terms of max temp., but not in quantity of heat collected from device and added to living space. Yes, by slowing air flow, you will gain higher temperature, but less air to transfer it. There is calculation of volume of heat (energy) received from this kind device on net, where air temp, and air volume are included. Your goal is not to have small volume of air with max temp, but to heat the room as much as you can during sunny hours. Your goal is to transfer as much collected heat using max air-flow, into the room as possible. All heat (energy) which remains in collector and not transferred into the room is NO GOOD. :-)
I apologize for long sentences and bad English...
I didn't realize there was no space between the cans. That makes sense now.
Koliko je vremena potrebno da se zagrije prostorija od npr 30 m2 na nekih 25°C i da li mo~e da se od~ava ta temperatura ako je prete~no suncano, kua je termo izolovana.
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