Appendix F
A Family Size Solar Oven for Winter
About the Solar Oven
To talk a bit about this solar oven, and why it was made, in many ways this oven is the end of a quest, you might say, of trying to make an oven that might function much more as a real oven does, but also an oven that could be used to feed a whole family. One of the big things about a lot of solar ovens is just how small they are, and usually can only hold one or two pans at a time. This works great if you are only cooking for one or two people, or if you need something portable, but if you have a whole family, you really need something a bit larger to cook many things at once in, because you do have to cook so many things to feed a family each day. You could also use many small ovens to do this, but the problem with this is just how expensive that can get if you buy them. Also, if you live in a more northern latitude, small ovens tend to not get as hot because, being small, there isn't as much sun, or energy, actually going into the oven. Even though you do have a smaller space to heat, in the end, they just don't seem to get as hot as larger ovens.
This really brings up the next issue this oven aims to solve is being able to cook food at high temperatures, around 300 degrees, even during the winter. With most ovens, you can usually get them over 200 all right, and maybe a little over 300 degrees during the summer, but during the winter, when it's maybe only 40 degrees outside and the sun only gets 30 degrees high at it's highest point, you usually can't get your oven much above 200. So the difficulty with a lot of ovens is that your food takes a long time to cook, while you don't have very much daylight to cook it in. There are also some foods that you just wouldn't be able to cook, like meat, because on some days the oven just never gets hot enough to do that safely. You also have the previous problem that, because it takes so long, if you're trying to feed a family, you could really only cook one meal in it each day, when you need to be able to cook quite a few things each day. Being in a more northern climate, these are all things we have faced during the winter with all of the solar ovens we have tried to build, and they just usually don’t work super well during the winter.
Another smaller issue this oven tries to solve is creating an oven that is also easy to use, even with how big it would be.
So in the end, this oven is really the end and culmination of that "quest," to find a way to have a solar oven that you could really cook a lot of food in, and cook food quickly even in the dead of winter. It's also kind of a mixing together of a lot of solar oven ideas, as well as new ideas I hadn't ever thought of before. In the end, I have to say that God really did outdo Himself with this one with all the ideas I know He gave for it :), and it actually has solved all of those above issues. I'm sure there are ways it could be improved upon if you had the know how and/or the money, but for my limited knowledge, ability, and funds, I couldn't ask for a better oven. Just to mention here, you can see all about the performance of the oven in the section further below named “Oven Performance.”
Now to go through some of the reasons why it works and how it solved those issues, the first really neat idea was to basically have the oven rotate around a pole that goes through it, that also has the rack for pans on it. The usual way of doing a sort of pivoting rack in solar ovens is to have a rack that kind of hangs from a pivot point higher in the oven. While this works, the issue is the rack tends to hit the glass if you rotate the oven too far forward, and you have to stop rotating the oven if you still want your food to be level. What was so neat about the idea for this oven is that, instead of the rack rotating as the oven rotates, the actual oven rotates around a pole, as well as the rack, that are in a fixed position. You can see that comparing these two pictures, and the way that the rack stays level as the oven rotates backward:
The great thing about this is that you can rotate the oven as far forward as you want, and the rack never gets in the way because the actual oven is rotating around the rack like a circle. This means you can start using the oven right when the sun comes up, or still be using it as the sun is going down. With that, it also means that during the winter you can cook from sunup to sundown, making the cooking time the very most it can be.
Another really awesome thing about the oven is that, because during the winter the oven has to be rotated so far forward to line it up with the sun, the heat in the oven will try to rise up through the back of the oven that is insulated. instead of the glass part of the oven that isn't insulated. So as you go further into winter, the oven actually starts to work more efficiently because less heat is trying to escape through the glass and more heat is trying to escape out of the back of the oven instead. This is also where the five inches of insulation in the door of the oven come in, because a lot of the heat will try to escape through that area during the winter and get trapped by all the insulation in the door. You can see how the back of the oven would become the top during the winter in this picture:
To help this happen further, unlike most solar ovens that have an angled top, this oven is flat on top, because it means you have to rotate the oven further to get it lined up with the sun, which also means more of the heat will try to escape through the back of the oven instead of the glass
One last thing that is also really great about this is that a lot of the weight of the oven is on that pole, instead of having to try to lift the back of the oven to line it up with the sun, as I have had to do in previous designs I have made, as well as what you have to do in a lot of other designs out there.
So all of that together makes the oven very easy to use, gives a lot of cooking space, and makes it able to get quite hot, and you can see where this one idea alone of having the oven rotate around the food rack on a pole was one of the biggest things that led to the oven working so well. To give credit where it’s due, the first place I saw this idea of having a pivot for the oven to rotate around: https://www.omick.net/solar_ovens/current_solar_oven.htm. and it’s really a fantastic design, but the main problem for me in trying to make something like it was that I needed a way that the oven could be on wheels and on pavement. From their design, I also couldn’t really figure out a way to keep the oven locked in position in a way that the reflectors could still fold down for storage, or in a way that you could still reach it with the way the oven is so low to the ground when it is on wheels. So for a while I had pretty much given up on the idea of being able to create something like it that would work for what we needed. Then one day, the idea just kind of came to me of having a pole going through the entire oven, and having the rack sit on top of that pole, and the oven could then rotate around all of that in a circular motion. This idea then allowed for being able to make a stand on wheels that would be pretty sturdy still, and also allowed the idea for keeping the oven locked at a certain angle to work. So it was kind of from there, eventually, by God’s grace :), I had ideas for what is seen above.
A few other small things to mention about it is that the whole oven can come apart in separate pieces, making is easier to transport it if you need to. Here are some pictures of assembling the different pieces:
As mentioned above, the other nice thing is that the oven is on wheels, which means if you have a garage with extra room in it, you can just wheel it out of the garage when using it, then wheel it back in at night, making it easy to set up. The wheels also make it very easy to align with the sun.
So altogether, those are some of the main things about the oven.
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.
Oven Performance
As I’m sure you are wondering by now how well the oven works, it’s a good time to talk about the performance of the oven and how hot it gets. The first thing to mention about the performance is, you can find a rather large amount of data I have gathered about it in the Download section of the website, in the file labeled, "Prepping List_Appendix F_Family-Winter Solar Oven_Data_Performance." Some of the times I use the oven, I’ve been keeping track of not only the oven temperature throughout the day, but also the sun’s angle in the sky, and things like how warm it is outside, how windy it is, and how cloudy it is. I’ve also kept notes about anything I change with the oven, as I have experimented with different things, and kept notes about things like whether anything was in the oven or not. So there is a lot of data that can be compared to see just how well it works in a lot of different situations. One thing to mention when looking at the data is that you will want to compare the sun angle, rather than the time of day, when comparing different times the oven was used. With solar ovens, the thing that has the most effect on temperature is how high or low the sun is, because the lower the sun is, the more of the earth’s atmosphere acts as a filter for the sunlight. So as far as the actual amount of light, or energy, that is going into the oven will be very different when comparing 9:00 in August versus 9:00 in October, simply because the sun won’t be as high in October at that time. Because of this, the better way is to compare the sun’s angle. The outside temperature also plays a role in how hot the oven gets, but not as much as the sun’s angle.
It is also worth mentioning that the temperatures I talk about below are without anything inside of the oven. I have found if you let the oven heat up first for maybe 45 minutes or so, then fill the oven with pans, the temperature seems to be about 50 degrees less than when there is nothing inside. So just to say when actually cooking, the temperatures would be anywhere between 0 and around 50 degrees less than what I mention below, depending upon how full the oven is. It's also worth mentioning that if you don't let thee oven heat up first and fill it with pans right when you start using it, the temperature seems to be between 0-100 degrees less. I don't know why it's so different, but it does seem to be different.
As for the performance, the hottest it has gotten so far was 370 degrees on September 26th when it was in the upper 80’s outside. It was really quite an amazing result because by that time, the sun was only getting 45 degrees high in the sky at it’s maximum, so the atmosphere was filtering out the light quite a bit more than in the summer when it gets about 65-70 degrees high in the sky. I also had not put anything black inside of the oven yet.
Again before putting anything black inside of the oven, another quite interesting result was on October 11th when it was only in the 30’s outside. For that day, the oven still got to 300 degrees by about 11:30. I had to then put some bread in the oven and the temperature went down, so I don’t know the highest it would have gotten that day to compare with other days. What’s intriguing though is in comparing this day to that September 26th day, a day that was almost 40 degrees warmer, and the sun was about 6 degrees higher at the times I took the reading. If you compare the times between 10:00 and 12:00 on both these days, you can see where on the day that it was only in the 30’s outside, it was only about 15-20 degrees cooler in the oven. So even though it was very cold, the oven was insulated enough that the air temperature didn’t seem to effect it very much. As said above, I also had to cook bread in it on that day and was able to quite easily.
So far though, the most amazing results happened after I started experimenting with adding pieces of black flashing inside of the oven. I talk more about this black flashing in a section down below. As for the results, the first one was on October 24th, when I had added one piece of black flashing into the oven, and it was again only in the 30’s to low 40’s outside, and the oven actually got up to 365 degrees by the afternoon, almost as much as the day that it was in the upper 80’s outside. From the testing I have done that is also talked about in that section about painting the oven black, if I had the other pieces of black painted flashing in the oven, the oven probably would have gotten up around 385 degrees. So this was really quite a phenomenal result that, depending on how much you were cooking, you could actually cook in temperatures over 350 degrees in such cold weather, and definitely temperatures over 300 degrees.
The next really amazing result was on October 30th. What was special about this day was that it was only in the single digits outside in the morning, and only got up to 20 degrees by the afternoon. So it was very cold outside. Amazingly though, with all of the black painted flashing in the oven, the oven actually got up to 335 degrees by 12:00 when it was only 15 degrees out, 365 degrees by about 1:30 when it had reached 20 degrees outside, and 370 by 2:15. What is so great about this is that, even in this weather too, by the afternoon, you would be able to have temperatures over 300 degrees to cook in. So in the end, I think these two results are probably the most amazing that have happened so far, and I guess you could say show potentially how hot the oven can get.
As far as actual cooking goes, so far we have been able to cook anything we have needed to cook as long as it wasn’t too cloudy. Even halfway cloudy days though, we have been able to cook things all right. Probably one of the neatest things we have cooked so far, that is also shown in that performance data spreadsheet mentioned above, was our Thanksgiving turkey. What was so neat about this is that, even though it was mostly cloudy that day and the air temperature was less than 20 degrees, we were still able to cook it all the way through. Even though the photos look like there was a little bit of pink from the lighting, when we were looking at it in person, we didn’t find any pink meat or juices anywhere on the turkey, which is one way of telling if it’s done or not. When we took the turkey out of the oven, we also checked the temperature, and it was around 165 degrees, which is another way of telling if it was done. So as far as we could tell, it had cooked all the way.
There are also quite a few other interesting things we’ve experimented with that you will see in that spreadsheet, mainly the different ways of doing the glass we have tried. I talk about these in a section below too, but for the performance side of things, one really interesting thing is that using two panes of glass instead of one, only gives about a 10 degree increase in temperature . I don’t have super good data on it because there are so many variables that change the temperature each day. As far as I could tell though, that was the only increase you seem to get.
I also tried using only oven plastic without any glass, and this too was quite surprising, just because it actually works quite well. I wasn’t able to get as much good data with this because there were a few days it was cloudy outside, but from what I could tell, the temperature with the oven plastic seems to only be about 30 degrees less compared to using one sheet of glass, or about 40 degrees less than using two sheets of glass. Which is a fair amount, but still, it’s just a thin piece of plastic. You can see this when comparing September 1st at 2:30 with September 15 at 1:47. At the time of doing the reading, the outside temperature on these days was less than 10 degrees different from each other, and the sun angle was almost the same. So it works as a pretty good comparison. Maybe in the future, if I have time, I’ll be able to get some better data on this. The important thing though is that, yes indeed, you can cook with only using oven plastic instead of glass!So that’s a summary of the performance of the oven so far.
Building the Oven
Preview of Instructions and Images of Real Life Build
Since these instructions are quite long and everything can already be downloaded for free in the "Downloadable PDFs" section to the left, here is just a preview of those instructions and some images showing what is involved with creating this. All of these images will also be in the PDF along with further explanations for things.
Also as another note, if you decide to build this oven, as will be mentioned in the PDF there is a spreadsheet with links to everything needed for building the oven in the Download section of the website, under the file labeled, "Prepping List_Appendix F_Family-Winter Solar Oven_Data_Cost." It "should" :), be a complete list of everything used in the oven, that also has the cost of everything used in the oven, as well as measurements for cutting most of the wood.
As also will be mentioned in the PDF, you can expect to spend around 50 hours or so building the oven. It will largely depend on what kinds of tools you might have. With how large it is, there are also going to be some times you will need other people’s help. Although, since it is a family sized oven, hopefully you will have family around to help :).
Lastly, it would also be very easy to make a smaller oven, if you would like to use the overall design, but don’t need the largeness of this oven. All you have to do is modify all of the horizontal measurements by the same amount. Currently the oven measures about 3 feet across, with about 30 inches across of cooking space. So if you would like to maybe have 10 inches less of cooking space, to make the cooking space about 20 inches across, you would just subtract 10 inches from every measurement going across the oven from left to right, or every measurement that is part of the width of the oven. This would go for reflectors, glass, and the stand too. In doing this, by the end you would have an oven that was 10 inches smaller across it’s width.
