A Fresnel lens powered glass recycling contraption was born during the 2019 ATC. Unfortunately, we only got to it on the last couple days and the thing came out very ugly, not to mention that it did not work. I decided to stay on at Wheaton labs as a Boot and get in some additional tinker time!
Problem: Lack of local glass recycling services mean that glass goes to the landfill or is crushed and mixed as aggregate in concrete.
Solution: homestead scale glass recycling! Turn broken bottles and jars into tiles, bricks, dish ware, jewelry, fermenting weights and more. Your imagination is the limit!
Bonus: Make a permanent home for Paul’s ultra dangerous Fresnel lens and melt glass with concentrated sun juice
The first application caught many wood bits on fire, burned the sand, and managed to melt a 1/4 inch round puddle of molten glass.
The drastic temperature differentials rendered the cooled glass fractured and fragile.
Problems: Very difficult to adjust. The open air environment is not conducive to accumulating heat. It required constant adjustment to keep the focal point on the glass. The resting angle of the lens is 45 degrees, resulting in the front needing to be propped up to face the sun.
We learned that the focal point of the fresnel lens is 35”-36” perpendicular to the lens
SOLAR GLASS RECYCLER 0.2
I was given charge to design the second iteration of the glass recycler as Uncle Mud was occupied with the rocket stove forge project.
I wanted to design something that would be
- Easy to adjust by one person
- An open framework, allowing future modifications without needing to rebuild completely
- A closed and insulated furnace that accumulated heat
- Compatible with future addition of automatic sun tracking.
I decided to build a new wooden framework that would support micro adjustments of the lens height and angle while balancing on a narrow base of 3 legs for easy pivotability. The resting angle of the lens was increased to 60 degrees to match the height of midday sun during the summer here to minimize the need for adjustments. The Insulated closed furnace could then be mounted inside this framework.
It works as intended. The entire frame can be easily pivoted by one person using one hand, while also being very stable. The lens can be raised or lowered by turning the wing nuts on the mounting bolts.
With the frame built I can now move on to constructing the furnace bit. The current plan involves a steel framed, ceramic fiber insulated box with a glass lid that sits parallel to the fresnel lens. More on that later, I’m off to the shop to build the darn thing!
I think that the firebrick in the photo melted because the light was very tightly focused directly on it. This is creating too high of temperatures in too small an area as far as I see it.
The first test with the new furnace will be using a slightly diffused beam of concentrated light to try and melt a larger puddle of glass more slowly. We’ll try and use firebrick lined with clay slip for the crucible.
That video is inspiring for sure, I love the use of drills. I hope we can push the ball a little farther in making the lens useful in a practical homestead sense.
The frame is coming along well, a couple more welds and then comes the insulation. We should be able to test it in a few days!
In the 1970s when I was a really little kid, I used to receive the Edmund Scientific catalog, which was in those days full of weird military surplus optics plus a few "high tech" modern gadgets. Prominent in those catalogs were fresnel lenses along with plans to do all sorts of cool and destructive things with them. But they were expensive and not very big -- it seems to me that the biggest ones weren't much larger than dinner plates.
Obviously, the state of fresnel lens tech has advanced since then. I am in awe of the huge one being used for this project, and the manifest evidence of its destructive power. I'm really looking forward to seeing if/how/whether it can be harnessed into a practical kiln for melting scrap glass!
Over a decade ago my neighbor had one of these large fresnel lenses at their rummage sale.
It was supposed to sit in front of a small TV and make the screen look bigger, ha.
I bought it.
Haven't done anything with it and had no idea it could get so hot.
It'll start a flame on wood as soon as it touches it.
I think diffusing for a lower temperature is a good idea, get down to the temperatures that fused glass kilns use. Also, grind the glass first if you can to get a more uniform product to remelt.
I have glass tile, seconds, from a local place that was commercially selling glass tile made from recycled glass. They are no longer doing this, but did it for years, one of their lines was specifically CRT glass tiles so had the color imparted from the CRT screens, a nice smoky color.
They ground the glass and then it could be poured into molds, in many cases colorant was sprinked on top, but the clear ones are very cool too. each had an individual mold so the glass was melted in the molds, not melted and then poured in hot. They used I think styrafoam for the molds, not sure, likely a more eco mold could be made, but overall as the molds were used for a long time and all the glass was recycled glass, it was a more low energy/waste opperation than the typical glass tile operation
I have a bunch of fresnel lens sitting around waiting to be used for something. You can get very large ones for free nearly every day. Just go to Craigslist free stuff and look for projection TV's. No one wants them anymore because the quality isn't good and they are huge, but the fresnel lens is right on the front and very easy to remove. I heard of a guy that took one out, leaned it up against his garage in the sun, and burned his garage down, so be careful.
Could you "turn down" the heat by moving the crucible away from the focal point in either direction? Spreading would be the same as diffusion and reduce the problems caused by the concentration in the hot spot.
Yes, the shower looks good,even though it is far from perfect, all the tiles are seconds and we have "interesting" grout surfacing. But, it is almost done and will be nice to have a shower again. Shower floor is from a local non-profit, the manufacturer donated to them so we are all keeping it from teh waste stream, and same for the recycled glass tiles in the shower walls, the manufacturer was discontinuing that line, they were seconds, and they were moving the entire production facility so buying them kept them out of the waste stream, and they were locally made from recycled glass ( also it was all very affordable being extras and seconds, etc...) The rest of the tiles are about to go to a local lady who does mosaic work, so none should go to the waste stream, I hand picked the "best" of the flawed galss tiles for the shower, and she will make art with the rest.