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)
do tag me a photo when you get around to that. i'm sure others would love to know about them too👌🏽
@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 👌🏽