Building a Solar Furnace – Step By Step

I am only doing this as a hobby, I am not an expert. 

I have researched this online and over the years I have seen hundreds

of hobbyists claim to make these out of scrap wood and beer or soda cans.

Several companies offer commercial versions of this for over 2 500 $.

My goal is to build it under 100 $.

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Day One – Building the Frame

 I started by making an outline of these panes of glass I had lying around from an old sashless window that had been replaced. I have four panes, so there’s enough to risk using glass for now, I’ve got two extra panes.

 

Now I had an exterior frame nailed from the back of a piece of plywood with plenty of overlap. 

Remember, once the unit is sealed, you can’t open it to lag it to the roof or the side of the house.  The overlapping plywood will give me plenty of room to bolt this sucker down, hurricane proof!

 

A handful of SPDT and SPST switches, pilot lights and four 12v DC brushless microfans. All this stuff is from surplus stores. Total cost: 9 $

 

It still needs two small thermometers, and en electronic thermostat.   I will be using a surplus 12vDC power supply for now, until I get it completely solar.

 

Now I have a box that has an outer frame and inner skirt. The panes of glass sit on the inner skirt.

A brace in the center supports the two panes. It will also hold the fans and the electronics.

 

I’ve used tape on the glass, for illustration purposes.

 

Caulking, round one.   In order to be efficient, this baby has to be tight. This is round one of caulking.  The entire unit will be caulked again when the glass panes are placed for the last time.

 

Once in place the glass panes will be sealed to the inner skirt and nearly impossible to remove.

 

The four microfans mounted to holes drilled through the center brace. 

 

The fans will be connected to an electronic thermostat. When the temperature inside the unit is over 25 degrees Celsius, these tiny fans will gently move that warm air outside the solar furnace and into the house. When the unit can’t sustain 25 degrees, the fans will shut down and the unit will operate on convection alone.

 

Detail of the fans.   These were picked up for a buck each at a surplus store. They are not very high volume, which should help keep the air temperature up while moving it.

 

It’s important never to force hot air through a small opening. This creates a Venturi Effect, and the air looses its temperature from compressing and speeding up to fit in a confined space and then rapidly expanding and slowing down again.  

 

 

 

Click Here to see Day Two / Page 2 

Click Here to see Day Three/ Page 3 

Click Here to see Day Four/ Eureka Day 

Page 5 / More Results  

*NEW* Click Here to see Page 6 

Click Here to see the results page (once built and installed) 

 

Stay Tuned! Updates will be posted as this monster progresses.
In the meantime I can be contacted at adminATdrobicho.com