Solar Glass Recycler (aka Fresnel Lens Glass Melter - FLeGM)

This thread might be of some help:

https://permies.com/t/85166/ungarbage/alternatives-recycling-glass

I fuse glass in kilns.  I have a few thoughts that may or may not help.  If the collector could be used to heat a plate of salt that could then be used to heat a kiln with an electric controller to take the temp to apx 1500 f it would grant you control. Keeping the glass at 950f for an hour after melting will anneal the product. I'd personally try to take an old ceramic kiln and retrofit it with a heating plate that could be accessed by a diagonally drilling into the kiln.  I'm not sure how a controller would work but being able to anneal the product when you're done is mandatory and keeping control over the glass temp is as well.  

Josiah: Nice work!!!  :D
Do you know if that's a fresnel off an old TV? The ones I have that came off TVs are some sort of plastic, am I dealing with the same things you are, or is that a nicer one than mine are? Curious if I'll get the same effect, wondering how much of your work I can avoid repeating :D

David,

I agree with you that standard glass or ceramic kilns work well and I think retrofitting one is a good idea. One of the questions that we are asking here is if we can build something relatively simple that works. Our design is a unique approach that I can’t find examples of elsewhere and it is so simple that it would be a shame to not give it a try. I suspect that we will not achieve “optimal” temperatures for fusing and annealing, however, we may still achieve success. Hopefully a future prototype will include a method for more precise temperature control.

Pearl,

Thanks! Paul’s Fresnel lens is made of plastic. It was acquired from the folks at green power science but I think they pulled it out of a TV. If I were you I would wait to see the results of our experiment before you do too much copying!

Got some time in today with the tile saw and the furnace is now lined. So many compound angles! Now we are ready for external insulation wrap and the glass lid.

Looks really nice Josiah!  How far will you keep the plastic Fresnel away from the cover glass?  Just thinking that you don't want to be close enough for thermal radiation from the cover glass to soften the plastic Fresnel.  Not sure how hot the glass will get.

Currently the setup will have a 3.5-5.5 inch gap between the two depending on how focused the lens is. I hope that’s enough for convection to cool the Fresnel. We shall find out

Ralf Siepmann wrote:

I think the lens requires constant precise tracking to keep the focal point heating a specific area for hours.

You are correct.
The sun moves one degree about every 4 minutes.

Trace Oswald wrote: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.  

Craigslist today in Minneapolis:

You are correct about that source of fresnel lenses.
I got my 18" by 36" fresnel lens out of an old projection TV.

Josiah Kobernik wrote: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

While it's always nice to faff around with a fresnel lens and the sun, are you looking in the right direction for a solution?
If the problem is a lack of local glass recycling, I might argue it's better to find out why and try to solve that so the whole region has a place to recycle glass instead of setting up a fresnel system to melt glass in a, let's be frank labour intensive and inefficient way.

Yes, why indeed is there no glass recycling in Western Montana? I didn’t bother to ask.

In reality this project is innovation for innovations sake, which is always a long shot. However, that‘s what the lab is for.

Is it labor intensive and inefficient? Isn’t innovation always that way? Even if there were glass recycling out here, it would need to be trucked hundreds of miles away for processing. Alternatively, if someone does successfully innovate a process by which glass can be recycled in their backyard using only the sun, that sounds very energetically efficient. If that process is worked out, then prototypes that reduce the operator labor will follow. Maybe in the future each town or community will have a solar glass recycler. Or maybe it will be a dead end, who knows?

TINKER ON INNOVATORS!!!

I like the concept that it’s worth the effort, even if it results in a dead end. What you never know is if your dead end (should that be the case) may be someone else’s inspiration. Here in Alaska there is also no glass recycling, due to the lack of processing, meaning the glass would have to be transported to the lower 48 (or Asia?), both cost prohibitive, despite many trucks returning down the Alcan empty and ditto for barges returning to Seattle. Which means it’s simply not profitable to anyone here, not that it’s not feasible or a good idea ecologically.
You initially mention it being used there in concrete. Not sure if that’s been considered here, but why is that not a good use for it? I’ve also seen it used in asphalt.

Glass as aggregate is becoming the "highest and best use" in a lot of places where sand and gravel are getting hard to come by. Globally, the construction binge of the past half century has made decent quality sand a rare and valuable commodity. Kind of crazy to think that we've spent the energy turning sand into glass only to turn it back into sand. Arguably, if all you had was beach sand and needed something better for building, turning it into low quality glass and then crushing it would make sense. Especially if you had lots of sun juice and some time on your hands....

Years ago I attended a conference on sustainability and one of the speakers message was on the myths of recycling, which was that for the most part recycling wasn't sustainable. It upset me and the audience but unfortunately it's true. So I added a 4th R to the recycling mantra. Refuse! Refuse to buy single use glass containers (etc.)!    

Josiah Kobernik wrote: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

This is amazing! What possibilities are there for large applications...solar power for homes, communities, etc?

Jon unless you are firing your own clay pots to put your home grown food into you are going to need some kind of container. Glass is better than plastic for a lot of things. I like the idea of minimizing consumption, but I find it often challenging. I am excited by this idea not because I think it is practical or that I think it will work how we are hoping it will work, but because we need to unnormalize the casual use of energy intensive materials and processes and really good way to do that is to understand the scale of our casual industrial use by comparing it to what we can gather naturally (like from the sun) with home made apparatus and scaling down much of our use to fit what we know we can produce nontoxicly while we learn to make better apparatus

When you do get the contraption melting glass well, you will need to anneal it to keep from cracking. The  possibilities of using a rocket stove to anneal are plausible. just thinking ahead

I have been a recycled glasd artist for over 10 years.  I have made tiles, jewelry (beads and pendants), and loads of stained glass items all out of re ycled glass of various types.   Anything over 1/2" in diameter will need to be annealed.  I worry about javing a glass top for the kiln as it to will heat up, but it will only heat up on one side and that uneven thermal expansion will most likely cause it to crack.  I would use a very small insulated kiln with a thick stainless steel  plate for the top. Use a pyrometer from an electric kiln to monitor the temp.  With your extreme  temperatures the plate should heat what is inside without direct contact with the light.  The best fusing kilns heat from the top anyway. Remember that when fusing glass you can't use different glasses from different sources because they won't have the same coefficient of expansion (look that up). If you want to combine different colors of glass bottles, the only way to do it is to crush the glass to sand size and mix it really well. That way the glass will all expand and contract evenly

Annealing glass of any significant thickness much over 1/4" thick requires relatively precise and constant temperatures and specific hold times at various temperatures depending on the type of glass. Not saying it can't be done with a rocket stove but I think it would be pretty hit or miss. The thicker the glass the more important all those parameters become.

From all the comments on the finicky specifics, it seems like this may not be a feasible way to recycle glass. Having done some brief research into this over the past couple hours (since I could have thousands of tons of it for free probably) it seems like the cost to crush and recycle glass, even if used as aggregate in concrete, is higher than the value of the end product. The most efficient path seems to be re-using the glass product for the same purpose as it was originally. The problem then becomes cost of handling, transporting, cleaning, inspecting for cracks/chips.
Hopefully better ideas are out there.