JPM:
The house air is circulated through the panel. I would eventually like to build enough heat that I can heat fresh air at the expense of 20-30F.
Thank you for the caution about wood, I thought I had considered everything. In that case I will try to come up with an alternative. I saw a guy use steel wall studs for his frame. I plan to use duct board for insulation on the next panels. The R value is 4+ while the temp rating is 250 degrees, rigid and has a mylar skin. Best of all it's inexpensive.
I could build a frame off the roof to rotate the panels 45 degrees, but I'm worried about wind then, which requires more bracing, more holes in the roof, more spacing between the panels to avoid the next panel's shadow, etc.etc. AH!
I see your point about facing the panels dead south. SE is covered with trees so I'd lose 2hrs of my energy window. I'll have to go SW which puts the panels off the roof at the front of the house, YUCK. or maybe on the wall of the attached garage with long duct. Or maybe I can rotate my entire house 45 degrees? Hmmmm.
I definitely planned on running the panels in parallel FOR efficiency. I could be wrong, but I figured four panels raising 70F to 120F was better than four panels in series raising 70F to 180F or 200F.
Albert:
I'll post pictures of the controller, MAYBE the panel but the panel's exterior isn't painted. It was intended as a test (with great results) rather than a permanent installation. I used 6in insulated flex duct run down the wall outside so it looks like a set from a cheesy science fiction movie. Heck I only have $40 in the panel, but since it works I will proceed with a nicer built unit.
For the controller I used Arduino Uno, a Seeed Ethernet controller, a 13.5V 3A wall wart, LM7805 for system power, a MOFSET driven by PWM from the Arduino to vary the fan speed to keep the incoming air a constant temp regardless of sun. I don't remember what temp sensor I used but it's a linear Fahrenheit-voltage. I can look if you want. I cut up a CPU heat sink and bonded that to the sensor to keep the temp reading more constant. The fan is the largest computer type fan I had on hand..... it's tool large for a computer, I dunno where I got it. I don't count the cost of the controller and related because I already had the stuff on hand from other projects.
I'll post a link to my monitor website once I remove the control buttons. I don't want people diddling with the fan controller y'know.
Thank you for your thoughts and your information.
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FWIW, sounds sorta familiar and nicely done. I'd easily believe 1000 BTU/hr. in sun, -->> ~ 25-40% thermal eff. maybe a fair amount more depending on flowrate, outside air temp. and other stuff. 850 BTU/day average seems a bit low. Is house air recirculated ? Does the ducting have a backflow damper ? Panels need not face dead south. I'm not sure this qualifies as a solution but, given a choice and weather patterns, facing more SE if possible may help take the chill off in the A.M. and you may wind up w/ ~~70% or so of the south orientation production. SW orientation will work but maybe create an overheat problem, the house probably being warmer by afternoon. The solar collector police won't come if the panels are off south some. For additional panels, ducting in parallel will get you lower pressure drop - smaller blower, lower pumping costs and probably quieter operation (which can be a big deal), but lower air velocity --->> less efficient heat transfer - less output -->>lower performance. It's the no free lunch thing and usually results in a bunch of design tradeoffs. A friendly caution which you probably know, or will soon learn, here first hopefully: Solar air heater boxes made of wood products dry out rather quickly. When they do, the kindling temp. of that wood based material is reduced. A stagnant collector may achieve temps. in excess of that reduced kindling temp. creating a fire hazard and /or an actual fire, especially if the controller decides to turn the blower on and light things up like a blast furnace.Good afternoon. I'd like a little advice please. I have referenced these and other forums many times to build what I would consider to be a very successful solar air heater panel. I've been lurking, reading and gathering information for some time.
The panel is 36x80 with single panel glass, two layers of black aluminum screen in an insulated box. I live in SC where it has been fairly cold recently. The panel has been running for one month. It noticeably warms the living room and kitchen (400sqft) which were previously the coldest rooms in the house. I built my own fan controller using Arduino which posts updates on the internet for me to watch from work during it's operation. Yea, I am proud of the controller
I calculate the panel makes about 850btu/hr of heat on an average day, ranging from 0btu on a cloudy day to near 1000btu/hr on a ~70degree say with full sun. I used a 13gal bag to estimate the airflow.
I installed the panel in the one location on the entire house that was reasonably accessible, would permit a temporary mount (since this is a prototype) and could be piped into a window to avoid drilling 5in holes through brick walls. Since the panel works so well I acquired three more panes of glass to build more panels and wish to permanently mount and duct them.
The trouble is, I have no south facing walls of roof. The house is near 45degrees off of south which makes mounting very difficult. I pretty much have to install the panels on the roof due to the layout, roof, trees, shadows etc. A south facing panel means it needs to be mounted off the roof on stilts which stinks.
Do y'all have any thoughts? Any links to people that have had the same problem with a solution?
Thank you.
I used spray painted steel wool for my original design many years ago. The next iteration used 4-6 layers of folded alum. screen sprayed flat black. 3d iteration used the screen, 2 glazings, and return flow to the collector ducted in a rather funky way that took it between the 2 glazings to preheat the air some on its way to the screen absorber material and also reduce the cover loss if the ambient temp. wasn't too cold. It worked well but was a bit impractical. Eff. improvement was slight but measureable, I think. Biggest unknown was flowrate, which I was never able to nail down beyond a swag. I had a lot of fun and learned some stuff. I found no right/wrong answers, the technology pretty forgiving, and I got a rush every time I felt the result of the warm power of the sun at the outlet.
Good luck. Stay curious. Regards,Leave a comment:
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Solar air heating NO south facing wall or roof - options
Good afternoon. I'd like a little advice please. I have referenced these and other forums many times to build what I would consider to be a very successful solar air heater panel. I've been lurking, reading and gathering information for some time.
The panel is 36x80 with single panel glass, two layers of black aluminum screen in an insulated box. I live in SC where it has been fairly cold recently. The panel has been running for one month. It noticeably warms the living room and kitchen (400sqft) which were previously the coldest rooms in the house. I built my own fan controller using Arduino which posts updates on the internet for me to watch from work during it's operation. Yea, I am proud of the controller I calculate the panel makes about 850btu/hr of heat on an average day, ranging from 0btu on a cloudy day to near 1000btu/hr on a ~70degree say with full sun. I used a 13gal bag to estimate the airflow.
I installed the panel in the one location on the entire house that was reasonably accessible, would permit a temporary mount (since this is a prototype) and could be piped into a window to avoid drilling 5in holes through brick walls. Since the panel works so well I acquired three more panes of glass to build more panels and wish to permanently mount and duct them.
The trouble is, I have no south facing walls of roof. The house is near 45degrees off of south which makes mounting very difficult. I pretty much have to install the panels on the roof due to the layout, roof, trees, shadows etc. A south facing panel means it needs to be mounted off the roof on stilts which stinks.
Do y'all have any thoughts? Any links to people that have had the same problem with a solution? I can't find a solution I'm especially fond of.
Thank you.
Leave a comment: