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)

@Lucky188

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

@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.

@Lucky188

thanks for the update.

other folks interested in the heat box idea👀👀👀

here are some details 👌🏽

@Lucky188

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

@Lucky188

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.

@Lucky188

that's great at those temperatures. that's F?

@holon42 Yes all in F

@Lucky188

wow, that's really impressive results 👏👏👏