Call me a physicist, but I'd like to see calculations on the static heat level of your insulated crucible given expected heat input from the sun vs. the loss through insulation and the heat input port. 

I'm very interested in a larger scale multi-purpose solar furnace.  The idea is to have a general purpose heat source for: cement making, metal foundry, heating to forging temperature for metals, glass making, etc  It would consist of a field of heliostats (mirrors) and a stationary target building.  The building has a safety wall facing the mirrors, with an opening for light to enter, and an insulated target chamber behind the opening.  Depending what task you are doing, you change out what goes into the target chamber and how many mirrors you focus on the target.  You can start out with only some of the mirrors built, and add more over time.  For extra high heat, or on cloudy days, you can have a gas burner or electric heater in the target chamber.  You have a lid or door to the chamber to access whatever you are heating.  This is tied to a shutter that closes the sunlight opening, so you are not blinded when you handle whatever you were heating.

Besides the safety wall protecting you from concentrated sunlight, the other reason to work indoors is to judge the temperature of the heat.  A solar furnace necessarily operates on a sunny day, and from experience doing blacksmithing, you need a shaded place to work to see the color the metal is glowing so you know what temperature it is.  To know what energy input you need, look up the Stephan-Boltzmann law.  Generally, any object will radiate energy per area as the 4th power of the Kelvin temperature times some constants: The Stephan-Boltzman constant, and the emissivity.  A black body has an emissivity of 1.00, and other materials you look it up.  Your crucible will be trying to radiate energy out by that formula.  So the best arrangement is to have an insulated chamber with a small opening that you feed in sunlight.  The hot crucible will try to radiate in all directions, but only the radiation in the direction of the opening gets out.  The rest falls on the chamber walls, which radiate back.

See solar sintering....

Another update.

I have the model mostly done, I'm now focused on wiring it together. The wiring is very simple, just four solar cells wired to two Tamiya Worm Gear gear boxes. I bought 10 tabbed cells and thought I would use them, but I am having a hard time getting them wired correctly. All the instructions I have found have been for soldering them together, whereas I need four individual cells wired separately. When My camera is done charging Ill post a photo.