This High Temperature Solar Furnace is a bit like a magnifying glass aimed at an ant:
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.
So how hot does it get?
Once the frame was completed, I tried a few experiments to see just how much heat the lens was capable of providing.Here is an image of a standard red brick that was held at the focus for about 20 seconds.
The spot at the bottom has been converted to glass in a matter of seconds. Normal brick firing temperatures fuse all the clay granules together without rendering them into a glass. The sunlight, however, quickly surpasses the normal kiln temperatures and completely melts the material.
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A U.S. quarter coin placed at the focus boiled in roughly 25 seconds. Copper melts in seconds, aluminum almost instantly. Wood or plastic at the focus will burst into flames immediately. Sand melts into glass and water will boil at once. Small ceramic items could be glazed at the focus but control would be tricky. Some of the bricks I tested would fracture and I suspect that the same fate would come about for ceramics, due to the expansion and contraction rate.