free heat. build a heat box for $6 and heat 500+sq feet, for free. during sunlight hours, i suppose.
does anyone have any experience or expertise on this claim?
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@holon42 The design on this one isnt the most efficient. I have 4 3 that fit in reg windows and one that sits on the ground 3'x4' there are lots of different designs. They have 12v thermostats and small fans. Using them last 2 winters I reduced heating gas by 66% both years. They do work the larger one so well I have to replace solar fan it had with a 220cfm air mover (6watt) to keep its internal temp below 200 - they draw air from inside & warm it
Id look at several videos before you decide to build one
I use 6' roll flashing which I bend into a V against a back plate of same flashing ( its cheap and AL has good thermal properties)
Painting the surfaces flat black enhance the amount of solar energy absorbed ( Missing in video you linked)
They do work but have to be setup and taken down seasonally.
Wwinters here have lots of gray days where they dont work - so back up heating is needed.
They dont work at night (duh)
I was fancinated by the idea and keep trying different things to make them better ( why there are 4 now) . Id take a picture but in my shed as I havent yet set them up ( do need to soon)
@holon42 I will , Ive tried for others posts when they were setup but the glare would never let me get a pic that showed inside. When setting them up will be able to get pics when not setup in full sun yet.
@holon42 Not the best pic - maybe as the flat black is meant to absorb light. Air comes in Top left two 6"vents board separating middle sect has 1" holes in it -1 inside each V one between each V - Bottom board same - bottom has no middle separation so air goes across to right side and up. thru more V heat exchangers and out the 2 6" vents. Flex ducting attached to those openings and to a board that fits in a window open 7 1/7 inches edges weather stripped so no drafts - <cont>
inside flex duct to two inline duct fans 6w rated 220cfm & 110cfm -org fan is still in top left opening but not nearly the air flow needed . measured output air w/ flow meter and area of output /temp in /temp out came up with 21000 Btu's w/full sun when 38 outside. I put a cheap thermo inside turns it on when internal reaches 90 inside box - - reaches temp inside box reaches 180 or 190 - air out 80-110 all 12V < 20W DC
Box itself is made from Some dog eared fence slats I had and backing 1/4 plywood box insulate 1 1/4" cheapo foam board - but its rated at 200 temps (dow pink stuff max is like 150) - they do work and its free heat . In 2022 when Nat gas spiked and prices did my heating cost went down. Made them as a hobby and to reduce methane use as greenhouse gas. Now sold on them. Smaller ones work similar but fit in windows and run with internal fans - 8"x11" solar in window runs each of those.
thanks for the update.
other folks interested in the heat box idea👀👀👀
here are some details 👌🏽
i suppose they need to get direct sun on them to work?
so as the sun moves, it activates different units?
@holon42 They face south on my house and part of reason for V shaped AL heat exchangers is it lets the sun hit them at more angles. The placement is a fairly big factor- not all sides of your house get the same hours of sun. Im fortunate that to the south of me is fairly open accept trees - So I get more hours of exposure. We had -15 temps last winter -20 prev from arctic blasts - with sun they still kept furnace from kicking on during the day.
@holon42 That one big unit with sun kics on 930-10am on south side of house and runs until 430-5pm - the times sort of shift as the season goes on. The others I have do run at slightly diff times but that more about placement one is SE another south one gets blocked by my deck until noon the other faces west and doesnt get sun until 4pm
right. thanks for that. i have several windows that could possibly be set up and follow the sun.
they're french windows, opening inward. so i wonder if the box could just replace the screen from the outside, leaving the window closed behind it instead of covering that space with plywood.
that's great at those temperatures. that's F?
@holon42 Yes all in F
wow, that's really impressive results 👏👏👏
@Lucky188
do tag me a photo when you get around to that. i'm sure others would love to know about them too👌🏽