This device is very good at demonstrating the potential power of sunlight.  Before I go into the details, I must place some warning notices here.

DANGER!  This device is extremely dangerous.  It should not be constructed or operated by anyone who does not observe proper safety precautions.  It will instantly destroy flesh.  It will melt metals, ceramics, and most any other material.

Always wear welding goggles when operating this device!  DO NOT leave this device unattended.

   The main component of this furnace is a large Fresnel lens.  These can be found as surplus or removed from broken large screen televisions.  Note that there are two types of lenses in these televisions.  One has a "bias" and will blur the focus right to left into a line.  This is not suitable for the furnace, although it can be used as a heat source for small heat engines (even small steam engines).

   The proper type of Fresnel lens has no bias and will reduce the sunlight to a small area (roughly a centimeter squared).  This type of lens will provide the highest concentration of sunlight into the smallest possible area.  That is the goal here- placing the most energy into the smallest space.

   A suitable lens can concentrate the energy to a density of roughly 6 megawatts per square meter- on par with the "Star Wars" weapons or laser weapons.  Because of this, I cannot stress adequately the need for safety.

To start the project out, I purchased the lens at a local surplus outlet as "sheet plastic" for $2.00.  I saw that they had 5 of these lenses and bought them all.    Once I had the lenses (in various sizes) I constructed a frame made of aluminum channel stock.  This was also surplus and cost about $15 for everything.    I used "Alumalloy" aluminum welding rods that can be welded with a small propane bottle torch.  You might use a TIG or other inert gas aluminum welding system.  You could even bolt things together and it will not affect the operation of the device.    This view does not show the angle braces that were later added to make the stand more durable.  (Please excuse the messy shop- this was before I moved into my larger warehouse location.)

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