My 2nd solar furnace just finished with video.

Bossrox

Solar tinkerer
My 1st solar furnace is doing so good, I made a 2nd 1 for my shed I just finished & put online today. 50 degrees right now @ 1pm & the box temp is maintaining a steady 97 degrees with the blower running non stop.
Once I got the shed up to temp with my heaters, it's holding a temp inside my 10x20 mostly uninsulated shed of 71 degrees on it's own.
The cost for lumber, insulation, hdwr, blower motor, electrical stuff & misc about $400 not counting the glass which I had on hand. From a glass shop would be about $150 each x 4 but much cheaper salvaging glass from some old sliding glass doors.
I slapped together a video of how this was made.
 

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sunshine_eggo

Happy Breffast!
Not trying to be a critic....

Did you consider adding barriers to channel the flow, e.g.?

1637782114761.png

I'm sure it would come down to a balance between flow and temp, but I bet there's some efficiency gains to be had.

Regardless, if it gets the job done, that's all that matters. :)

Very cool.

What's the power consumption on the blower?
 

Bossrox

Solar tinkerer
Not trying to be a critic....

Did you consider adding barriers to channel the flow, e.g.?

View attachment 73410

I'm sure it would come down to a balance between flow and temp, but I bet there's some efficiency gains to be had.

Regardless, if it gets the job done, that's all that matters. :)

Very cool.

What's the power consumption on the blower?
I did something like that on my 1st experimental furnace & you're right, it's more efficient but my second cabin furnace doesn't use that, just an open box but puts out so hot I have my door open today @ 50 degrees & it's toasty in here. Blower I'm guessing is about a quarter amp.
 

markansas

New Member
My 1st solar furnace is doing so good, I made a 2nd 1 for my shed I just finished & put online today. 50 degrees right now @ 1pm & the box temp is maintaining a steady 97 degrees with the blower running non stop.
Once I got the shed up to temp with my heaters, it's holding a temp inside my 10x20 mostly uninsulated shed of 71 degrees on it's own.
The cost for lumber, hdwr, blower motor, electrical stuff & misc about $400 not counting the glass which I had on hand. From a glass shop would be about $150 each x 4 but much cheaper salvaging glass from some old sliding glass doors.
nice you could cut up pieces of black stove pipe and place in there for heat exchange or paint rain gutter pipe black.. the pipe will heat up around the whole edge might get you some more heat. and low cost. low cost important..
 

Bossrox

Solar tinkerer
nice you could cut up pieces of black stove pipe and place in there for heat exchange or paint rain gutter pipe black.. the pipe will heat up around the whole edge might get you some more heat. and low cost. low cost important..
I don't believe that would improve it that much, the backing is solid black, that will absorb & transfer just as much heat in my estimation.
 

Bossrox

Solar tinkerer
Another idea I was thinking about was getting some 1" thick stone pieces & liquid nailing them to the backing, painting them black to hold the heat longer after the sun wanes.
 

markansas

New Member
Another idea I was thinking about was getting some 1" thick stone pieces & liquid nailing them to the backing, painting them black to hold the heat longer after the sun wanes.

thin metal heats up faster and transfers the heat along the metal. now a brick behind it would hold the heat once it got hot.. tic for tac i like thin metal pipe and yes it would get cold fast with no sun.. there has to be others here doing the same thing.. any ideas people?
 

Bossrox

Solar tinkerer
I did something like that on my 1st experimental furnace & you're right, it's more efficient but my second cabin furnace doesn't use that, just an open box but puts out so hot I have my door open today @ 50 degrees & it's toasty in here. Blower I'm guessing is about a quarter amp.
Another thing I did was put a Y on the air blowing into the box, this way air is blowing in different directions & creating enough turbulence to mix up any standing heat pockets.
 

Dhasper

Solar Addict
Another thing I did was put a Y on the air blowing into the box, this way air is blowing in different directions & creating enough turbulence to mix up any standing heat pockets.
Do we have any estimate of efficiency with this arrangement? I take it this is much more efficient than inverting to ac and using regular heater.
 

markansas

New Member
Do we have any estimate of efficiency with this arrangement? I take it this is much more efficient than inverting to ac and using regular heater.
just air heats up box fan pushs hot air out into room.. so simple.. yet effective could also use a computer fan and run it on a small 12v panel..
 

Bossrox

Solar tinkerer
Do we have any estimate of efficiency with this arrangement? I take it this is much more efficient than inverting to ac and using regular heater.
This is my best idea. Without the furnace I'd be running a 1500 watt heater to do the same thing the furnace is doing running a 150 watt blower. If you can figure out the efficiency ratio, you're smarter than me.
 

markansas

New Member
Another thing I did was put a Y on the air blowing into the box, this way air is blowing in different directions & creating enough turbulence to mix up any standing heat pockets.
ya know its a empty box play with it and lets us know which kicked up your heat output.. i was thinking the same lines and using rain gutter for the traping of heat.. so ya play away have fun.. kinda interesting to keep it low cost
 

Bigtruckin85

New Member
My 1st solar furnace is doing so good, I made a 2nd 1 for my shed I just finished & put online today. 50 degrees right now @ 1pm & the box temp is maintaining a steady 97 degrees with the blower running non stop.
Once I got the shed up to temp with my heaters, it's holding a temp inside my 10x20 mostly uninsulated shed of 71 degrees on it's own.
The cost for lumber, hdwr, blower motor, electrical stuff & misc about $400 not counting the glass which I had on hand. From a glass shop would be about $150 each x 4 but much cheaper salvaging glass from some old sliding glass doors.
Your solar furnace and Solar hot water builds are very cool. I watched some of your youtube videos a few days ago as I work out my first off grid build. My brain is completely worn out from trying to piece together a solar array, I feel like it's similar to learning a new language, so the simpler more tangible alternative energy devices are kind of relaxing to think about.

Along the lines of sunshine_eggo, I was wondering about some kind of baffles in the box, not necessarily to direct flow, but more like heatsinks to create more surface area and potentially hold heat longer. Maybe chunks of black painted 2x4 or something to give some extra area, and maybe a little bit of restriction. (I'm typing slow, I see you thought about this in your replies).

On your other build, if I remember correctly (brain fried from solar math), I believe you had the fan blowing from under the house up through to the higher entry into the house. I'm not an expert on this stuff at all, I have some experience with how I currently heat my house with a similar duct system from a wood stove in my garage, but I'm really just experimenting with what works and doesn't. It may not be possible in your situation, but I'd be curious to know what affect switching the fan orientation would have. Example, moving the blower to pull the heat through the box from the top and natural air return from below. Do you know what kind of temps and CFM you get on the output side now and how that is different from what's in the box?

To give you some reference of my current experience, I have been heating my regular house for about 5 years with a small wood stove in my garage. I built a small room around the wood stove (basically my room is your solar box), built a hood system over the woodstove which goes to about 12ft of 8 or 10" duct pipe across the ceiling, to a variable speed (600 CFM max) duct fan that has a thermostat built in, to about 12 more feet of pipe into the house. When the warm air heats the blower enough, it turns on at whatever I have it set at (usually on around 85F). I have a wireless thermometer in the duct and typical temp coming out when keeping a nice burn going is around 100-115F. Blower is supposed to be rated to 140f from my memory. I don't know what the exhaust CFM ends up being as I don't know how to measure other than "feels pretty good". For return air, I just leave the door between the garage and house open. I can keep 1400 SqFt in the high 60's pretty easily all winter as long as I'm home. Temps here usually average in the 20's during worst part of winter I would guess.
Always great to see new ideas since the more options people come up with, the less dependent on grid resources we will be.
 

Bossrox

Solar tinkerer
Your solar furnace and Solar hot water builds are very cool. I watched some of your youtube videos a few days ago as I work out my first off grid build. My brain is completely worn out from trying to piece together a solar array, I feel like it's similar to learning a new language, so the simpler more tangible alternative energy devices are kind of relaxing to think about.

Along the lines of sunshine_eggo, I was wondering about some kind of baffles in the box, not necessarily to direct flow, but more like heatsinks to create more surface area and potentially hold heat longer. Maybe chunks of black painted 2x4 or something to give some extra area, and maybe a little bit of restriction. (I'm typing slow, I see you thought about this in your replies).

On your other build, if I remember correctly (brain fried from solar math), I believe you had the fan blowing from under the house up through to the higher entry into the house. I'm not an expert on this stuff at all, I have some experience with how I currently heat my house with a similar duct system from a wood stove in my garage, but I'm really just experimenting with what works and doesn't. It may not be possible in your situation, but I'd be curious to know what affect switching the fan orientation would have. Example, moving the blower to pull the heat through the box from the top and natural air return from below. Do you know what kind of temps and CFM you get on the output side now and how that is different from what's in the box?

To give you some reference of my current experience, I have been heating my regular house for about 5 years with a small wood stove in my garage. I built a small room around the wood stove (basically my room is your solar box), built a hood system over the woodstove which goes to about 12ft of 8 or 10" duct pipe across the ceiling, to a variable speed (600 CFM max) duct fan that has a thermostat built in, to about 12 more feet of pipe into the house. When the warm air heats the blower enough, it turns on at whatever I have it set at (usually on around 85F). I have a wireless thermometer in the duct and typical temp coming out when keeping a nice burn going is around 100-115F. Blower is supposed to be rated to 140f from my memory. I don't know what the exhaust CFM ends up being as I don't know how to measure other than "feels pretty good". For return air, I just leave the door between the garage and house open. I can keep 1400 SqFt in the high 60's pretty easily all winter as long as I'm home. Temps here usually average in the 20's during worst part of winter I would guess.
Always great to see new ideas since the more options people come up with, the less dependent on grid resources we will be.
My cabin furnace draws air from inside. The other way around wouldn't be a good idea to me 'cuz you'd be drawing the hot air thru the blower which if it got too hot could curtail it's lifespan. I just use a simple thermal switch I got off ebay that monitors the box temp & fires up the blower when it reaches a good toasty temp, same for my new 1. The baffles you mention would only add marginal heat retention & since I'm into my 2nd furnace, it isn't a significant enough gain in effeciency to justify the extra build work. My cabin furnace puts out some serious heat so I'm not even thinking about modifying that but the shed furnace is drawing in much cooler air as it's not insulated as good as the cabin so I may tinker with some thin brick backing to see if it'll help but likely next winter. The blowers are bullet inline 4" ipower's I thought were 150 watts but just checked & it's only 90 watts @ 190 cfm. They move the air at a pretty brisk pace. I'm using 4" 3034 sewer line pipe for the ducts on both furnaces.
 

Bigtruckin85

New Member
My cabin furnace draws air from inside. The other way around wouldn't be a good idea to me 'cuz you'd be drawing the hot air thru the blower which if it got too hot could curtail it's lifespan. I just use a simple thermal switch I got off ebay that monitors the box temp & fires up the blower when it reaches a good toasty temp, same for my new 1. The baffles you mention would only add marginal heat retention & since I'm into my 2nd furnace, it isn't a significant enough gain in effeciency to justify the extra build work. My cabin furnace puts out some serious heat so I'm not even thinking about modifying that but the shed furnace is drawing in much cooler air as it's not insulated as good as the cabin so I may tinker with some thin brick backing to see if it'll help but likely next winter. The blowers are bullet inline 4" ipower's I thought were 150 watts but just checked & it's only 90 watts @ 190 cfm. They move the air at a pretty brisk pace. I'm using 4" 3034 sewer line pipe for the ducts on both furnaces.
I had thought about the heat being pulled into the blower and it's longevity, but this one has lasted all these years and has had no issues so far, so I'm pretty happy with it. I figure it saves me about $100 a month during the winter, so it more than paid for itself the first year and I really didn't know what to expect when I put the system together. I'm hoping to build your solar furnace and solar water heater eventually. I appreciate your work and videos. Thank you.
 

Bossrox

Solar tinkerer
I had thought about the heat being pulled into the blower and it's longevity, but this one has lasted all these years and has had no issues so far, so I'm pretty happy with it. I figure it saves me about $100 a month during the winter, so it more than paid for itself the first year and I really didn't know what to expect when I put the system together. I'm hoping to build your solar furnace and solar water heater eventually. I appreciate your work and videos. Thank you.
 
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