if you want a surprise, try the screen with a foil background rather than flat black, I saw a 15 degree gain using the reflective surface instead of flat black for the back of the panel. It was a side by side comparison with the same screen.. also the same length of screen folded back and forth in a wave profile instead of stretched in three flat layers also gave about a 15 degree gain over three flat layers.
@@symonvanrisjel9959 sadly no, it was just a throw together for my own amusement. Looking back at it I am going to say the gains from the different way of laying the screens was probably just a trade off of heat gain vs air flow. But the foil vs black background I think was a true gain as more light, thus energy was reflected back onto the screen absorber which seems to be pretty efficient at transferring the energy to the air. There is some interesting reading on boundary layers and laminar flow if you google "The Zen of Passive Solar Heating Panel Design Morris R. Dovey"
Right on point. Like the virtually side-by-side comparisons with the thermo gun. This helps decide on what to build. For the cost of the aluminum downspouts, they aren't worth the money considering the screen gets just about as hot and is much cheaper. And then the channel is even cheaper and gets hotter. Thanks for the video!
Absorbers that have air flowing across the glazing lose a ton of efficiency. None of these are actually getting to their theoretical efficiency since they all circulate air past the glazing, which causes a lot of heat loss. It may not be an issue if you live in Arizona, where outdoor temperatures never get much below freezing, but in somewhere like Canada where temps regularly hit -40, the efficiency will drop way off. The ones where the air flow is kept inside tubes like the can and downspout units will work much better, but the open plenum design on these kind of negates any gains you get from the sealed airflow. The plenums on both ends of the tubes need to be sealed and insulated so that air flow only goes down the center of the tubes, not around the outside. This is also a poor efficiency design with the screen and flat plate absorbers, tube type absorbers have a much higher efficiency at low external temperatures. Also, drawing in cold outside air really knocks down efficiency, you need to recycle the cold air from inside the house, not try to heat outdoor air.
I have followed many of your builds and the "channel" box worked well for ME. Free shower door from craig's list and scrap lumber. Free computer fan and magnets. I'll upgrade to a timer when I get the bug. Thank you for posting this comparison.
Nice comparison. I like the idea of using the downspouts for a super easy build but the metal cans are a great up cycle project. I was surprised to see how effective the aluminum cans were.
Did you ever do the follow up video on the channel heater where you tacked the sheet metal into it, I can't find it and would love to see how it affects things. Great videos, thank you!
Nice succinct comparitive...good work. Have watched many tests. Thermodynamically speaking it is a ratio game of surface area of absorbtion, rate of dissipation and baffling of airflow over the surfaces. The best tweek of quick hack is the downspout build with baffles. Cut backside bend in tabs. Another alternative is to put screen inside tubes. The aluminum cans will always out perform steel....cans just slower to accumulate, to build and paint. Thanx for great content!
i built a large one a few years ago..it was the size of a sliding glass door..That was free glass, so i made mine huge.. the temperatures were hot, but you really needed a more powerful fan to make them worthwhile. I happened to have a blower fan. It moved a good amount of air. I used a variable fan controller and adjusted it for the desired temperature i wanted.. so it would speed up as it got hotter, and slowed down as it got cooler.. I used aluminum cans, I had a header at the top and bottom..and i think i had 11 towers of cans, and I can't remember how many tall.. My only issue was that i couldn't find any flex duct that would last. so after a few years, i decommissioned.. but it was great when i had it,,
Hi Desert Sun! I am in the process of making passive solar heaters completely out of found materials for less fortunate members of my community. The only things I will need to purchase are the fan and solar panel. What is the cheapest fan and solar panel I could use outdoors? I notice that you vent your panels from the back. Any particular reason? Have you considered venting it out from the top? Thank you.
hi there. i think it's great that you are helping your community! you could vent it out the top if you wanted too. the best place to get the fans and the solar panels is amazon. they have lots of both of those. nearly all solar panels are made to be used outdoors and most if not all computer case fans will hold up fine. i've noticed that even the cheapest solar panels on amazon are pretty sturdy.
I think I would not drill the holes at the bottom of the frame but have a gap between bottom of the cans and the frame, then drill lots of little holes on the back so that the fan draws the air in and channels the air through the bottom of the can tube. If it's cold and windy outside you don't want cold air forced up the tubes and into the house. This way the fan has to pull air in. Whether or not it makes a difference to the outlet temperature being drawn into a cosy environment first I'm not sure as it might have some cooling effect on the upper cans
Yes they work during the day ….not so much at night …… but it could keep your heating from running during the day, here where I live its been cloudy alot …
In order to really compare the heaters it must be done based on the energy extracted. It is a combinaison of air volume and temperature. So you must be able to measure the air volume and its temperature. BTU = CFM x (Tout - Tin) x 4.5
Todos tus videos de los distintos modelos y de como lo hacen estan muy bien. Pero no dices cuanto tiempo tarda en calentar una habitación y de cuantos metros cuadrados es esa habitación
They work in any temperature so long as you have a bit of sunshine on the panel. Loss in the ducting I think would be minimal. The fan is pumping it straight into the house. You could probably run the ducting to eight metres in the roof void if you wanted the ventilation somewhere central. Bear in mind the primary function of these devices is to reduce relative humidity, dry air is much quicker and cheaper to heat. Then if your home is well sealed, you don't need to open windows and you get fresh warm air through your house changed every hour or so.
Now look I've been watching 👀 you for years and think you need to write ✍a book that is so pertinent to our world and would have it in my book case. I built a small cooler with small radiator, ice water and 12v pump and it works so I'll make a bigger one.
sir i have a suggestion toward developing the solar heater, why you don't make a loop of the Aluminium cans in the board , this loop have an open valves at end of a specific sides and this valves connected to the fan area directly, its about controlling the air circulation at a different distances for increasing or decreasing exposure of air to heat by the mentioned controlled open/closed valves, which make it more and more reliable. hope to hear your reply soon thank you.
To put this on a house couldn’t you use air from the floor of a room as the intake air and then have the outlet air be pumped out the top. Also any estimate on how much sqft this will heat?
I wish you would make more videos. Do you have reddit page? Would love to follow your projects! I am currently building a can solar heater (a mixture of steel and aluminium).
Just stumbled upon your channel....this definitely looks like the simplest yet smartest design yet!! Thanks for the informative video. I see it’s been a while since you posted. Hope you are planning to make more videos!!
Not long , depending on materials used , I built one for my 4x6 greenhouse, just wanted to preheat fresh air , do not want to kick on my heaters also solar power , but greenhouse stays at 70f degrees with outside air at 30 f and now can add fresh air without kicking on heaters , of course just need sun to stay out , but using every bit of Mother Nature is fun hobby
Something like zigzag (horizontally with little angle to prevent hot air getting trapped in high spots) metal pipes should heat better as air would get longer time to heat up.
air takes no time to heat up. Consider the heater core in your car, which is a small radiator. It flows hot coolant through the heater core and a fan blows air through the aluminum fins of the radiator. It takes a millisecond to heat the air flowing through. All you really need is a material like copper, aluminum, silver or gold that has a high thermal conductivity so it can take the heat and transfer it to the air, the key is surface area. Of course, if it's too efficient, then you need more thermal energy to transfer or it will become too cool too quickly. I had a friend who put a racing radiator on his car, and you couldn't get any heat in the winter because it was TOO efficient. The engine literally couldn't heat the coolant quickly enough, that radiator was great for the engine, not so great for the driver.
How could I use such a heater at night? Is there a kind of storage device one could add to the solar panel in order to use the heat charged during the day at night? I do not understand much of these things, so I apologize if my question seems way to farfetched.
hi there. one idea is you could store the heat it generates in thermal mass like sand or rocks. you'd have to rig it up so that the unit heats those up during the day and then at night they'd release the heat.
I tried the down-spout version. Full sun, temperature is 45 degrees outside. Hardly any heat at all when the fan is running. I have no idea what I did wrong :(
The output heat is dependent on the solar intensity (which is less during the winter), length (time) of solar exposure , & heat loss of the system. You'd therefore get less heat out on average during colder months.
A number of factors come into play. The sun's intensity is less in winter, so that's a start. Keep in mind that a small heater unit like any these will not give enough heat to warm a building. These are great examples of what can be done at home, but you'll want to build something quite a bit larger for more surface.
....another point to remember is that the intake air side will supply air from inside the structure, so it will not be frigid to start with... you're heating air that's probably already 60 or more degrees. Don't try to heat cold outside air.
Nice vid but I wish someone would do these different styles more scientific so you can really see the difference between them. Like all the boxes being the same size, same fan, all out simultaneously in the sun.
hi there. i've got a couple vids like that. they compare 3 different types of heaters (the steel can one, the screen absorber one and the downspout one) *they're made almost identical (the downspout one is a little different, but close)
I haven't seen a single design that show recycling the air. I'm building a greenhouse, so I need to take that air through a tube in from the bottom from the greenhouse and return it back to the greenhouse
It’s pretty easy just add return hose (duct ) to air intake on your design, I use this for fresh air that I reheat through solar collector as to not turn on heaters for my 4x6 greenhouse, my greenhouse is pretty tight and during 30 degree days need some fresh air without letting in all that cold air , any of these designs will increase temp from outside air so really adds to greenhouse hobby and vegetables love fresh air
Black roller blinds and table fan works just as well although the heat is not concentrated to a small diameter for temperature checks. okay so the rooms darker. But ur warm. But probably just as good without the construction, pipe work and hassle.
I built a beer can heater five years ago and it works better than any of these. Why? Because they are all lacking a thermoplane. You need to draw room air into the heater, heat it, and let convection blow the air out of the top. You start by finding out the elevation of the sun mid day during the middle of winter. Then you build an angled top piece that fits in the lower panel of a window in your home so your heater is at a 90 degree angle to the sun maximizing solar gain. Room air flows in the bottom plane all the way to the bottom of heater unit, gets pulled into the cans or sheet metal where it heats and convection rises and blows into the room without needing a fan. I built mine out of double layers of foil faced Styrofoam taped with metal duct tape. The top is a corrugated clear green house panel. Styrofoam layer between the cans and the lower air plenum. Normal input vs output temp differential is around 50 degrees and I get around 6 hours per day of heat. Weight of eight foot unit is around 30 lbs. Light enough for most seniors to handle.
hi. i generally like to pull in outdoor air because it's fresh but you can certainly recirculate if you want to. it gives the highest heat on the coldest days. my climate is not super cold like the midwest or eastern states