This device is capable of melting brick and boiling steel
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The next step was to add proper counterweight and a work stand at the focus of the lens. I will post more detailed pictures of these in the near future. Meanwhile, let's look at the focus frame that I added to the stand.
| Once I had the frame
constructed, I installed the lens and measured the focal distance. I
then made a frame that was slightly larger than this distance so I could
place a crucible or other apparatus at the focus.
This image shows the square aluminum focus frame. Once I had the center marked, I installed a platform that could be adjusted and used to hold the work piece at the proper focal point. I operate the furnace on a stone or concrete surface so stray light will not ignite the grass or other vegetation. |
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| 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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| To illustrate the extreme
temperature, I have moved the brick into the shadows. This allows
you to see that it is still glowing red hot.
By placing a crucible of red earth at the focus and blowing a stream of hydrogen gas through it, I was able to reduce a small amount of molten iron directly from the ore. This works because the hydrogen "steals" the oxygen from the iron oxide, leaving plain iron behind. A small continuous process furnace could in theory be made that uses local red earth (iron ore) and a bottle of hydrogen gas to supply raw iron in small quantities. In space (such as on the Moon) this concept can be used to produce metals for industry, although on a much larger scale. |
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Now, if you were to apply a "biased" lens (one that will not focus sharply) to a small steam engine, it could operate a small generator or alternator for charging batteries. The size of the lens in this example allowed a collection of roughly 750 watts of power. This was concentrated down to just over a square centimeter in area. With losses (the plastic is not perfectly transparent and the lens is not perfectly efficient at focusing) I estimate that the energy density is about 6 megawatts per square meter equivalent.
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.