I made a passive solar heater using aluminum cans. The results are better than I expected.
(preppers)This is the heater![]()
This is the general way to make one (Not my video) though I'll leave out for now largely useless details like whether or not to use glass or an acrylic pane ($76 for the size I needed but the price drops rapidly as you get smaller) and so on.
Mine has a little bit more and a bit more attention to detail. For example, silicone caulk and metal tape, reflective insulation board, two 12 volt solar panels to panel 2 12 volt CPU fans to push air a little more. $20 per panel, $12 for 4 fans though I only used two ($6 total).
Total cost was definitely less than $200 since I had most of the parts lying around anyway but I don't have a solid price on how much I spent since it's been a "back project" I piddled with for the last 4, maybe 5 years. This spring I kind of kicked it into higher gear - call it a gut instinct plust tired of it taking up so much space in the workshop - and now we're looking at a much higher cost for natural gas (at least) this winter which is what heats the main part of my house.
Using an extremely scientific and not-prone-to-errors meat thermometer, the temperature air I get out of it is between 150 and 160 degrees. The fans kicked on and provide a bit more push on the air than I initially expected and this doesn't seem to lower the temperatures any since it's still outputting about the same heat as smaller units you see people showing you how to make. The benefit I hope for with a larger unit is to still put out more heat in colder weather with less sunlight than smaller units can handle because I'm using this to heat living space and not a greenhouse or workshop.
The solar panels aren't as sensitive to light as I'd really like but I still get about 6 hours of push out of them and by the time the light is dim or not direct enough to power them, it's not really heating the cans inside either so that's fine. The fans kick on around 10 AM and cut off around 4.
I've had it up three days by this point and the day/night temps finally got to a point where I thought I could get you some good numbers. The part of the house it's heating is the first floor, somewhere around maybe 1500 square feet (seven rooms total). The house is "L" shaped so one part of the house (study, living room, dining room) benefit more than the rest (kicthen, foyer, bathroom, 2 bedrooms) but the difference between the two parts stays at just 1 degree.
This morning, at 7 am, it was 27 outside and the heater had already kicked on for the morning schedule to heat the house to 68. I turned off the heater and did periodic temp readings throughout the day.
7 AM -> 27 outside, 68 inside
9 AM -> 36/66
10 AM -> no reading but solar kicks on and the heater is still off.
11 AM -> 44/66
12 PM -> 48/66
2 PM -> 52/65
5 PM -> 51/66
It would seem that at least for early winter, late spring, this heater is going to be very useful for holding the house temperature high enough that I don't need to use the house heater. This does not indicate that it will be as useful when temperatures are sustained in the 30s or lower though I suspect that as long as I have enough sunlight that it will cut into how much I need to use the heater.
I plan to insulate the output hoses with corrugated plastic pipes, maybe wrap it in some thin insulation as I do this though I'm not sure about that part. It's not permanently mounted to the house and the hoses go to a window frame insert for a portable AC unit which is basically thin but stout plastic and that is a source of heat loss that I could stand to insulate.
In any case, the heater allowed me to go all day without using the house heater. With natural gas and other heating fuel costs predicted to hit sky high prices this winter, I should be cutting a lot off of my heating cost.
The bastard might be ugly and people driving by might wonder "WTF IS that??" but it works.
