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.
[ + ] SparklingWiggle
[ - ] SparklingWiggle 8 points 3.6 yearsNov 14, 2021 23:16:38 ago (+8/-0)
You should also wrap the exposed tubing in foam insulation.
Congratulations on being self-sufficient and resourceful.
[ + ] totes_magotes
[ - ] totes_magotes [op] 1 point 3.6 yearsNov 15, 2021 07:34:11 ago (+1/-0)
This is an air system, no water at all. The sun heats the cans and convection (and the fans) move the air. I know it wouldn't seem like it would be all that efficient because the heating "tubes" are just... open. But it works. At 40 degrees, I was still getting hot enough air despite the hoses being uninsulated though, as I said, I expect that efficiency to drop at colder temps and for it to be a source of heat loss until that insulation is added.
[ + ] PotatoWhisperer
[ - ] PotatoWhisperer 0 points 3.6 yearsNov 15, 2021 11:55:50 ago (+0/-0)
[ + ] WhiteCollarCriminal
[ - ] WhiteCollarCriminal 4 points 3.6 yearsNov 15, 2021 01:32:14 ago (+4/-0)
[ + ] totes_magotes
[ - ] totes_magotes [op] 0 points 3.6 yearsNov 15, 2021 07:35:34 ago (+0/-0)
[ + ] beece
[ - ] beece 4 points 3.6 yearsNov 14, 2021 22:25:05 ago (+4/-0)
[ + ] 3Whuurs
[ - ] 3Whuurs 3 points 3.6 yearsNov 14, 2021 23:33:14 ago (+3/-0)
I looked into making one of these a few years back and found a few guys claiming a design that just uses a few layers of aluminum screen painted black, with franell lenses instead of glass, and worked better the tin cans, and was WAY easier to make. With the franell lenses it looked like they made the box from sheet metal cause it was pumping WAY more heat then the house needed.
I was trying to design one for a cousin in the prairies for the -22° winters, and some guys had units utilizing the excess heat by blasting it at a cpl 45gal water drum (solar batteries), then recirculating that air at night with the latch closed to the solar heater outside.
It looked like a bunch of plumbing, but cheap enough to do, and it looked almost possible heat 24/7 in cold climate that way.
[ + ] PostWallHelena
[ - ] PostWallHelena 1 point 3.6 yearsNov 15, 2021 10:06:26 ago (+1/-0)
Found this head to head comparison of screen v can. The screen is a little more efficient.
My question is, if the fresnel area covers the same area as the regular glass or acrylic and your absorbers take up the same area, how is the fresnel an improvment? They are collecting the same amount of solar energy right? Maybe if you did a convex curved array you might be more efficient at getting the sun from different angles. What am I missing?
@totes_magotes
[ + ] totes_magotes
[ - ] totes_magotes [op] 1 point 3.6 yearsNov 15, 2021 17:53:44 ago (+1/-0)
Also interesting to note that he tested airflow and came up with about what I was just kind of "head experiment" figured... that the middle and ends would have more airflow. Hence, in the photo, you can see that my outlet hoses are in between, where he identified the slow spots. The block above it is just a kind of "empty baffle" to "connect" all the tubes into a common place to suck the air out (and hold the fan wiring).
But curving the lens is an interesting idea. Seems it would give you maybe an hour or two extra heat by allowing a wider field of sunlight to be collected and pointed to the cans.
I do have to wonder what would happen if I painted the sun-side of the cans with Black 2.0 - https://culturehustle.com/products/black-v1-0-beta-the-world-s-mattest-flattest-blackest-art-material
I have a bottle of it. I could mix it up, hit it with an airbrush.
[ + ] PostWallHelena
[ - ] PostWallHelena 0 points 3.6 yearsNov 15, 2021 19:27:47 ago (+0/-0)
[ + ] totes_magotes
[ - ] totes_magotes [op] 0 points 3.6 yearsNov 15, 2021 19:37:04 ago (+0/-0)
[ + ] PostWallHelena
[ - ] PostWallHelena 0 points 3.6 yearsNov 15, 2021 20:18:44 ago (+0/-0)
[ + ] totes_magotes
[ - ] totes_magotes [op] 1 point 3.6 yearsNov 15, 2021 21:21:36 ago (+1/-0)
[ + ] totes_magotes
[ - ] totes_magotes [op] 0 points 3.6 yearsNov 15, 2021 07:36:49 ago (+0/-0)
[ + ] toobaditworks
[ - ] toobaditworks 2 points 3.6 yearsNov 15, 2021 06:26:13 ago (+2/-0)
https://pic8.co/sh/VI3npG.jpg
[ + ] JudyStroyer
[ - ] JudyStroyer 2 points 3.6 yearsNov 15, 2021 05:56:03 ago (+2/-0)
[ + ] TheSimulacra
[ - ] TheSimulacra 2 points 3.6 yearsNov 15, 2021 03:53:27 ago (+2/-0)
[ + ] totes_magotes
[ - ] totes_magotes [op] 0 points 3.6 yearsNov 15, 2021 07:38:02 ago (+0/-0)
[ + ] Deleted
[ - ] deleted 2 points 3.6 yearsNov 14, 2021 22:50:59 ago (+2/-0)
[ + ] totes_magotes
[ - ] totes_magotes [op] 0 points 3.6 yearsNov 14, 2021 23:05:40 ago (+0/-0)
[ + ] PostWallHelena
[ - ] PostWallHelena 2 points 3.6 yearsNov 14, 2021 22:49:14 ago (+2/-0)
I did a little research into passive heating. We are really just building our houses stupidly and we’ll have to change our designs to absorb more heat from southern exposures and retain it in thermal masses—since our energy market is now totally jewed. Thanks jews. My southern exposure is blocked by the neighbor’s house. :(
[ + ] totes_magotes
[ - ] totes_magotes [op] 2 points 3.6 yearsNov 14, 2021 23:04:34 ago (+2/-0)
[ + ] paul_neri
[ - ] paul_neri 2 points 3.6 yearsNov 14, 2021 22:46:25 ago (+2/-0)
[ + ] totes_magotes
[ - ] totes_magotes [op] 2 points 3.6 yearsNov 14, 2021 23:05:19 ago (+2/-0)
[ + ] paul_neri
[ - ] paul_neri 2 points 3.6 yearsNov 14, 2021 23:09:59 ago (+2/-0)
[ + ] totes_magotes
[ - ] totes_magotes [op] 0 points 3.6 yearsNov 15, 2021 07:30:20 ago (+0/-0)
[ + ] PostWallHelena
[ - ] PostWallHelena 1 point 3.6 yearsNov 14, 2021 22:54:50 ago (+1/-0)
[ + ] thebearfromstartrack4
[ - ] thebearfromstartrack4 1 point 3.6 yearsNov 15, 2021 03:07:09 ago (+1/-0)
[ + ] totes_magotes
[ - ] totes_magotes [op] 1 point 3.6 yearsNov 15, 2021 07:40:23 ago (+1/-0)
[ + ] germ22
[ - ] germ22 1 point 3.6 yearsNov 14, 2021 23:30:10 ago (+1/-0)
I've build one myself last winter but ran into a few issues. I had massive heat loss from the pipes that ran from the heater into my house. Then at some point my little fan and solar panel stoped working. It got so hot in the solar heater it melted the insulation.
since then i have had not enough time to tinker with it again.
[ + ] totes_magotes
[ - ] totes_magotes [op] 1 point 3.6 yearsNov 15, 2021 07:39:58 ago (+1/-0)
[ + ] Kung_Flu
[ - ] Kung_Flu 0 points 3.6 yearsNov 15, 2021 20:45:23 ago (+0/-0)
Only getting heat during daylight seems less than ideal.
[ + ] totes_magotes
[ - ] totes_magotes [op] 0 points 3.6 yearsNov 15, 2021 21:24:39 ago (+0/-0)
[ + ] Kung_Flu
[ - ] Kung_Flu 0 points 3.6 yearsNov 16, 2021 02:58:47 ago (+0/-0)
Probably wouldn't be worth the effort as the specific heat of a small tub of water isn't comparable to the whole home but just an odd thought.