Appendix A
Fresnel Lens Stand - New Version
A Bit about Fresnel Lenses
First, before talking about the stand, it’s good to talk a bit about what Fresnel Lenses are ( pronounced Fruh-nel ). Basically all that these are, are very large magnifying glasses that focus the sun’s light and energy to a certain point. There are also two types of these Lenses. One is called a Spot Lens that focuses all of that light to a very tiny point, around an inch wide, and the other type of lens is called a Linear Lens that focuses that light to a spot around 5 or so inches. This difference in how small of a point the light is focused also then changes how hot that point can get. Probably the best video that shows this is one that can be found here: https://www.youtube.com/watch?v=xExXjXm0YV0, where the person demonstrates a variety of lenses and how quickly, or not quickly, the pieces of wood catch on fire.
Another really great video to watch, if even just to gain a healthy respect for how dangerous these can be if you’re not careful, is one that can be found here: https://www.youtube.com/watch?v=drE54ctrHBY, where the person uses a spot lens and the focal point is up around 3800 degrees, hot enough to then melt steel, as well as sand into glass!
After watching those two videos, you will be able to see that there is kind of a range of maximum heat you can pick from with Fresnel Lenses, depending on the size of the Fresnel Lens, and whether the lens is a Linear Lens or not. In contrast to Spot Lenses that can be up to 3800 degrees, the largest Linear Lenses only get to around 700 degrees at their focal point, which is better for cooking type applications. You can see a list of Fresnel Lenses here, where they can also be bought: https://greenpowerscience.com/SHOPFRESNELHOME.html. We ourselves bought the 54” Linear Lens shown here: https://greenpowerscience.com/FRESNELSHOP/54INCHLINEAR.html. The heat it outputs is similar to the fourth and fifth lenses shown in that first video mentioned above.
A Bit about Their Uses
So that’s a bit about what Fresnel Lenses are. As far as why Fresnel Lenses might be useful, or why you might want to get one or not, it will mostly depend on what you might need, but I think probably their greatest strength is in their versatility. And in that vein, probably the best way to find out if they would be useful to you is to share some of the things that other people have done with them.
One of the ways people have used them is to heat water. Because of the way these lenses can get so hot in a small space, you can put that Focal Point on a pipe, and as water goes through the pipe, it heats up very quickly. So it’s basically like you are using the Fresnel Lens as a heating element on a pipe, creating your very own Tankless Water Heater like these, except using Solar energy: https://duckduckgo.com/?q=tankless+water+heaters&t=ffab&atb=v173-1&iax=videos&ia=videos. This is something that we haven’t tried doing yet, but from the videos we have seen from others, it looks like it would work well. I’m sure it would never work as well as the units in the link above, but you would still be able to get hot water from it, just at a reduced flow rate. This idea can be seen here: https://www.youtube.com/watch?v=C_yhi_fy-Q0, here: https://www.youtube.com/watch?v=rrGMidc_P7s, and here: https://www.youtube.com/watch?v=mFtD8_ejqsM. In each example, the people using them are trying to fill a tank or pool with hot water, but you wouldn’t have to do this. You could also just use the water coming directly out of the pipe, and if you let the water run slowly out of the pipe, it should be quite hot. Going this route, you could also use the stand that is shown in “Appendix E_Solar Water Heater” to have gravity fed water going through the pipes, instead of relying on a pump or city water pressure. Even if doing a tank idea, in the first video linked to above, it only took about an hour to get 6 and ½ gallons of water up to 120 degrees. So that is pretty quick for 6-1/2 gallons of water compared to other options out there. It’s probably the cheapest solar option as well, even if you had to use 2 Fresnel Lenses to get the water temperature you are looking for.
Another idea we have seen is using them for water distillation. This can be seen here: https://www.youtube.com/watch?v=aXjMAItCMl0, and another one in Spanish here: https://www.youtube.com/watch?v=wygFrqXI44I. I don’t know how well it would work for large quantities of water because of the way the sunlight, and therefore heat, comes from above instead of below. So you probably wouldn’t be able to heat up a pan of water very well because the heat would be hitting the lid instead of the bottom of the pan where the water is. However, heating up something small and transparent like what is in the videos would work. As a note, if you want to try to heat up a pan of water for distilling it, there is a way to use a polished piece of metal or a mirror to bounce the light from this lens onto the bottom of what you are heating. This is shown in the cooking links below, but this is a more complicated way of doing things than using a fireplace or a parabolic cooker like this: http://www.solarcooker-at-cantinawest.com/parabolic_solar_cooker_solar_burner.html. So even though this Fresnel Lens would work, using a fireplace or parabolic cooker would probably be better suited for distilling larger amounts of water in larger pans.
As mentioned above, yet another use for these Fresnel Lenses is cooking with them. This would be an application where the Linear lens would be quite useful because you don’t need all of the light going to a tiny spot, and it’s actually better if it doesn’t so your food cooks evenly. This is also another thing where the fireplace or parabolic cooker would work easier than this, however, these lenses do still work. There are a few videos that you can find on YouTube of people doing this. This one shows cooking a roast by just putting one glass bowl on top of another glass bowl with the roast inside, creating a crock pot: https://www.youtube.com/watch?v=7RMdvMvsjdI. There is another one here showing cooking eggs, where you heat the cast-iron skillet up first, then put the eggs in: https://www.youtube.com/watch?v=45NgOfr2k1k. Here is another video showing cooking eggs, however this one shows a way that you can use a mirror or polished piece of metal to bounce the light on to the bottom of your pan: https://www.youtube.com/watch?v=MhZrZ7Naw_c. Another video also shows this mirror idea to heat up spaghetti sauce, as well as a way that you can use a metal box with water in it to cook spaghetti: https://www.youtube.com/watch?v=ncswYjG93To. With this same mirror idea again, this video shows cooking popcorn: https://www.youtube.com/watch?v=uD2GmrT7pLQ. And lastly, here are two more videos showing cooking meat on basically a piece of metal: https://www.youtube.com/watch?v=OmlXR2nsis4, and cooking cornbread in a cast iron skillet: https://www.youtube.com/watch?v=k2X7nohhAS4.
We ourselves have also tried using our Fresnel Lens for cooking, even during the winter. Quite amazingly, it did still work, even though the air temperature was in the 30’s outside! Here are some pictures showing that, cooking eggs in a pan.
These first two pictures shows the setup we started out with, where we had the pan sitting on some rock wool insulation. This was to keep the bottom of the pan warm and prevent any heat loss by conduction through the bottom of the pan. We were just experimenting with the idea in the images below, so you'll see the insulation is still exposed. If you were using this idea long term, you would probably want to wrap the insulation in aluminum foil so no insulation would get in your food. Then between the pan and rock wool insulation, there is a piece of tin foil. This is to keep another type of heat loss from occurring, called radiant heat. This is the kind of heat you feel when standing next to a fire, or that comes to us from the sun, or the type of heat loss emergency blankets stop. Basically, this type of heat is a bit like light. So if you have something reflective, like aluminum foil, it will bounce off that surface and back into the pan.
All together, this worked fairly well. The eggs were cooking like this and would have eventually cooked all the way like this. The main problem though is that we didn’t have any kind of lid for the cast iron skillet. So the cold air blowing across the pan prevented it from getting really hot, and the water in the pan didn’t ever simmer, even though it did steam. About midway through though, we added a Pyrex bowl on top of the eggs, seen below. This really helped a lot. With that on there, a small part of the eggs would actually start smoking if left in the focal point for a couple minutes because of getting too hot. You can see in the second picture below, the air temperature was about 38 degrees when doing all of this.
You can’t see it in the picture very well, but at the bottom of this picture where it is wet, you can see that the Pyrex bowl also started doing that spitting kind of thing that crock pots do, where the steam builds up in the crock pot and releases a little bit at a time, sort of spitting out at you. So the temperature inside would have had to be pretty warm to do this.
And here you can sort of see the final eggs all cooked. I think if we had added the Pyrex bowl from the beginning, it probably would have only taken 15 minutes or so for the eggs to cook. So that is one thing to note: if you want to use these to cook in the winter, you probably want to get a cast iron skillet with a glass lid on it like these: https://www.amazon.com/cast-iron-skillet-glass-lid/s?k=cast+iron+skillet+glass+lid.
About a week before that, we also tried cooking flat bread that was about an inch thick with the Fresnel Lens. It was basically just a very thick pancake. You can’t see the bread in the picture below, but you can still see the setup we used for it. All we did was put one cast iron skillet on top of another one. Then when the skillet on top got hot, we would flip them over, so the skillet that was on top, was now on the bottom. The bread would also flip over in doing this and cook on the hot pan that was now on the bottom. Doing this over and over again, the bread then eventually cooked after about 45 minutes. We also used some aluminum flashing to do the same thing as in the previous images, trying to bounce the radiant heat back into the pan:
So those are some of the different ways you can cook food with Fresnel Lenses.
Now for one last use, as shown in one of the videos mentioned at the very top of this whole description, another use for Fresnel Lenses is melting metal and being able to possibly do limited blacksmithing type work. I don’t know how well this would actually work, but the possibility is there. In addition to the video link at the top of this description: https://www.youtube.com/watch?v=drE54ctrHBY, there is also this video that shows some limited knife making ability out of zinc: https://www.youtube.com/watch?v=QwXe2sK-SOI, and this video showing making a key out of zinc: https://www.youtube.com/watch?v=iMfkgBvQ8ig.
So altogether, probably the greatest strength of these Fresnel Lenses is their versatility, and the rather large amount of applications you can use them for. There are some options out there that work better than these Fresnel Lenses for specific things, but so far, I don’t think we have run into anything that could be used for such a variety of things like these can.
About This Stand
Now that you know about Fresnel Lenses, it’s time to talk about why this particular stand might be useful for you, and in the end, why I made it the way it turned out. One of the main difficulties I found with trying to use these lenses is in the way that their focal point is usually about 25 – 35 inches away from the actual lens. The other difficulty is in the way that the sun travels across the sky in a circular or arc pattern. When you put these two things together, depending on how the stand is built, it can make it difficult to keep the lens lined up with the sun throughout the day. Probably the best way to explain why is through the image below on the next page.
This is a very crude image :), but it shows two versions of stands, as well as how things change with them while trying to use the Fresnel Lens as the sun gets higher in the sky from Morning to Afternoon. In the Image, you can see the Focal Point represented by the green lines, the Pivot point for the stand represented by the Blue circle, and what you are heating up represented by the red box. For the first row, we can see a very basic stand where the pivot point for the Fresnel Lens is at the middle of both the stand and the Lens. The difficulty with this stand though is that the Fresnel Lens is fixed at a certain height. So as the sun gets higher in the sky, in order to keep whatever you are heating in the focal point, you have to lower what you are heating throughout the day. This can be time consuming to constantly have to re-setup what you are trying to heat, especially if cooking something. The other difficulty I found is that it can be a bit hard to actually find the focal point again each time what you are heating has to be lowered. If you only had to realign things once or twice in a day, it’s not so bad, but if you are trying to use the lens from Morning to Evening, you would have to adjust everything at least 10 or 15 or so times in one day. You could make a stand where the Fresnel Lens slides up and down instead of what you are heating, which is the idea I initially had when making a stand for mine, but this too runs into the same problems that it’s very time consuming to constantly have to find the Focal Point throughout the day.
So the much better way of doing things is what is shown in the second row, where the pivot point for the lens is wherever the Focal Point is at. What this means is that, basically the Lens pivots around the Focal Point, which means the Focal Point never moves. This way, you always know where the Focal Point is because it never changes. This also means you don’t have to move whatever you are heating very much, because the actual lens goes higher as the sun goes higher. It’s also the Lens that moves in a circular pattern with the sun, instead of whatever you are heating having to move in a sort of circle with the sun.
So in the end, that’s the idea behind this stand is having a very easy way to know where the Focal Point is throughout the entire day, and also a very easy way to keep whatever you are heating in that Focal Point, without adjusting things very much. This is the basic concept that you will also see in the instructions below for how to build the stand. Another great thing about the stand you will see below is that it is also able to rotate and lock in place without any kind of electricity either.
Lastly, as with all the things I build, I just want to give credit to God for all the amazing ideas He gives during the designing and building of these things, because it is so much because of Him that they even work as well as they do :). He really is an amazing person, and it is always such a fun thing and a treasure to get to build these things with Him. The truth is, I never could do it without Him, whether it be through direct ideas He gives, as He talks about doing in Exodus 31:1-6, when He gave people the wisdom and understanding to create the things He wanted them to create:
"Then the Lord spoke to Moses, saying: “See, I have called by name Bezalel the son of Uri, the son of Hur, of the tribe of Judah. And I have filled him with the Spirit of God, in wisdom, in understanding, in knowledge, and in all manner of workmanship, to design artistic works, to work in gold, in silver, in bronze, in cutting jewels for setting, in carving wood, and to work in all manner of workmanship.
And I, indeed I, have appointed with him Aholiab the son of Ahisamach, of the tribe of Dan; and I have put wisdom in the hearts of all the gifted artisans, that they may make all that I have commanded you:"
or it's just because of His ability to make me in a way that I could create these things, it is always because of Him in the end that they exist, and not because of my own amazingness to do them. With each of us, when we are born and given life, we don't know why or how we are able to do the things we do, or why we are just naturally better at some things versus other things. While it is true that throughout life we can learn new things and become good at things, even this ability to learn and grow is something that none of us know how we do. We just are who we are, and we don't have an explanation for it. But if none of us actually know how we are able to do what we do, how can we then take credit for it? It is only because of God's amazingness to create us in a way to do these things, that we can then do them. So is it not God, the one who made us able to do the things we do, the one who should have the glory for what we do? And in this way, even when He doesn't give ideas for things directly, it is still only because of Him that I can create these things.
The story of Nebuchadnezzar being turned into an animal in Daniel 4 really shows this as well, that without God's ability to make us understand life and how to create things, we never would be able to. Our understanding of things and ability to reason is only as much as what He gives us. I'll just quote a little bit of the chapter here:
"All this came upon King Nebuchadnezzar. At the end of the twelve months he was walking about the royal palace of Babylon. The king spoke, saying, “Is not this great Babylon, that I have built for a royal dwelling by my mighty power and for the honor of my majesty?” While the word was still in the king’s mouth, a voice fell from heaven: “King Nebuchadnezzar, to you it is spoken: the kingdom has departed from you! And they shall drive you from men, and your dwelling shall be with the beasts of the field. They shall make you eat grass like oxen; and seven times shall pass over you, until you know that the Most High rules in the kingdom of men, and gives it to whomever He chooses.” That very hour the word was fulfilled concerning Nebuchadnezzar; he was driven from men and ate grass like oxen; his body was wet with the dew of heaven till his hair had grown like eagles’ feathers and his nails like birds’ claws. And at the end of the time I, Nebuchadnezzar, lifted my eyes to heaven, and my understanding returned to me; and I blessed the Most High and praised and honored Him who lives forever:
For His dominion is an everlasting dominion,
And His kingdom is from generation to generation.
All the inhabitants of the earth are reputed as nothing;
He does according to His will in the army of heaven
And among the inhabitants of the earth.
No one can restrain His hand
Or say to Him, “What have You done?”
At the same time my reason returned to me, and for the glory of my kingdom, my honor and splendor returned to me...Now I, Nebuchadnezzar, praise and extol and honor the King of heaven, all of whose works are truth, and His ways justice. And those who walk in pride He is able to put down."
So I really do give Him the glory for what He has done, whether it's giving direct ideas, or creating me in a way that makes it possible to think through these things, and I just hope that my expression of Him will be a blessing in your life that shines with the incredible love and goodness that is in His heart. Because this is the real and amazing purpose of why He does give these things. They aren't just for our own use, but to love others with them. This was really what John the Baptist was trying to say in Luke 3:7-14 when he talked about giving your extra things to others that don't have what you have:
"Then he said to the multitudes that came out to be baptized by him, “Brood of vipers! Who warned you to flee from the wrath to come?...And even now the ax is laid to the root of the trees. Therefore every tree which does not bear good fruit is cut down and thrown into the fire.” So the people asked him, saying, “What shall we do then?” He answered and said to them, “He who has two tunics, let him give to him who has none; and he who has food, let him do likewise.” Then tax collectors also came to be baptized, and said to him, “Teacher, what shall we do?” And he said to them, “Collect no more than what is appointed for you.” Likewise the soldiers asked him, saying, “And what shall we do? So he said to them, “Do not intimidate anyone or accuse falsely, and be content with your wages.”
As though to say, "Use the things of this earth to bear good fruit and love others with it, because it's all going to be destroyed anyway. Put a purpose to it and do something good with it. Use the things in this life as a tool to store up treasure in heaven instead of here on earth." As Yeshua (Original Hebrew name of Jesus) also says in Matthew 5:16, let your light shine so that others may see your good works, and glorify God, and come to know God, because of them:
"You are the light of the world. A city that is set on a hill cannot be hidden. Nor do they light a lamp and put it under a basket, but on a lampstand, and it gives light to all who are in the house. Let your light so shine before men, that they may see your good works and glorify your Father in heaven. "
So it is in that love He has given these things, for as He says in Matthew 6, He knows the things that we need in life, and as such a loving Father, is so glad to help, and it is also in that love and in His love that I give them as well, hoping that what He gives out of that love will be a help to you as it has been to us.
Instructions for Building the Stand
Before getting into the instructions, something to mention about building this stand is that; as mentioned at the top of this description, the specific Fresnel Lens we got can be found here: https://greenpowerscience.com/FRESNELSHOP/54INCHLINEAR.html. Because of that, this stand is also made specifically for that lens. So as the stand is currently shown in the instructions, it will only fit that particular lens.
However, this stand was intentionally made so that you should be able to modify it to fit any of the Fresnel Lenses found on that website. Instructions for how to do that can bee found towards the end of these instructions. So just to mention, you will want to take a look at those instructions if you are using a different lens than what we got.
Something else to mention is that you can also find most of the measurements provided for this particular stand in the file labeled, “Prepping List_Appendix A_Fresnel Lens_Data_Cost,” that can be found in the downloads section of the website. This spreadsheet also goes over all of the supplies you need to build the stand with links to those things, as well as their cost.
You can also find pictures of building the real life stand below the instructions.
And with all of that said, now here are the instructions. Enjoy!
Photos of Building the Real Stand
Here are the photos I took while building the stand. You will notice a few differences between these pictures and the stand in the instructions. This is because I modified a few things in the instructions to try to make it a little better after building my own stand. Even with the few differences though, hopefully they will help in understanding some of the steps that are in the instructions.
Photos of Adding Fabric or a Window Shade to the Back of the Fresnel Lens
Original Fresnel Lens Stand
I don’t know if it would ever be useful to anyone for ideas for anything, but here are some images of the original Fresnel Lens stand we had built where the Fresnel Lens could slide up and down instead of what you are trying to heat up having to move as the sun moves. It did sort of work, but the current stand shown above works much better.
