Notes from designing my first cabinet type solar drier

[Bubu]

I have posted this on another forum where I think more people will benefit from it. But of course my dear friends on avalon should not be left out. Read this if you are interested in solar drying it will help you to design a much better one than the currently popular ones.

https://permies.com/t/111457/kitchen...lar-dehydrator

Just some quick notes as I am on the move again.

So I was reading this morning on solar driers. I have modified my sawdust fired drier to a combo or alternate. Meaning I can use solar alone or saw dust alone or use them simultaneously. I was looking for some brilliant tips to incorporate it on my project. I notice that everything you were doing about solar dehydrators SD, Is wrong except for this brilliant one.

Sorry cant find it. The one I read this morning. Its the one that uses soda cans


I admire how this friend of ours, uses his senses. He was able to arrive at the correct route. Without the aid of schooling. I am not as adept. I just lucky that I got the schooling and decades of playing with fire. Without it I would likely have copied all the wrong thing I have read from internet, just as everyone is doing.
He uses his senses akin to this:
Get a long and wide piece of metal and wood and put it on a wall facing the sun. But first paint the wood black. Finish a cup of coffee and place your cheek next to the wood panel without touching it. Do the same to metal. Did you feel the heat? Where? Remember that we are only imagining. But you felt the heat. Now touch the skin of your arm to both alternately as long as you can. Did it burn? Where? Experience will tell you where. Most 15 year old boy can already tell. So what does it tell us?
-Wood is a poor conductor metal is very good conductor. Therefore it is better to use metal than wood next to your herbs, your herbs will be heated as your cheek.
- color does not absorb heat but the material. Maybe it conducts better when painted black and dull. point is; color is not the main thing.
Another from experience:
If I put a glass of water on a whistling kettle and put a small fire under it. The water will dry up. Without air passing over the surface of water. Therefore air molecules fly the moment they have absorb enough heat. They fly with the air molecules and not the popular mantra that air carries moisture, the more heated it is the more water it can carry. That’s BS science. The heavier water molecule carried by the lighter one? I don’t think that’s possible. Anything that’s heavier than water will sink and anything that’s lighter will float.
This is what I can afford this time. will tell more if I have time, but I will leave a nutshell.
Gather the radiation of the sun in a metal and transfer it to air by conduction. Do not heat the air by radiation. Its like a marriage between moron that produces an idiot. Just trying to be funny. Do not use a fridge with its insulation on unless you are putting the sun inside with the herb
I am not yet complete with the project but I have test burn it already. This is good news for everyone obsessed with solar drying Top shelf at 65C, bottom temp. 40C, sun radiation at 70C, when fully loaded 14 trays 30 X 30 inches. Dried 7 trays of morringa when the sun is out all day. The other 7 is half dried. Dried it couple of hours the next day.
If you want plans for this project send me a purple moose I will accept donations for the plans. But you can also wait until I am finish explaining everything here then make your project.

[Constance]

Bubu, keep up the great work! I'm going to have to link this to my natural homes thread.



Constance

[Bubu]

More;

with your car park in the open on a hot day touch your skin on it. I accidentally touch my SD already painted black and I was taken aback by surprise in a split second.

Conclusion. Heat transfer by conduction is much faster than heat transfer by radiation. Because obviously the heated cannot be hotter than the heater and I am expose to the sun but was not burned. That's why I said that that collecting suns heat in air is a marriage between morons. Poor heat transfer system and poor conductor, in fact air is considered insulator. I have not done the math yet but I am sure, heat transfer by radiation to metal is much faster than heat transfer by radiation to air because metal has a much higher coefficient of thermal conductivity. And also heat transfer from metal to air is much faster than heat transfer from sun to air because conduction heat transfer is much faster than radiation heat transfer. The lower or slower rate will apply because obviously the faster will be able to supply the heat needed by the slower. The soda can is brilliant because aluminum has higher thermal conductivity than steel, its cheap and very thin meaning you can pack a lot of surface area for contact.

I have some concern though which is out of my expertise so I am putting up the question.

I remember reading somewhere that above 50C some of the nutrients will be destroyed. As I have said top shelf is 65C. Is it true? If its true I might put a thermal switch on the top shelf that operates a computer fan whenever 50C is exceeded. Hope someone can help me with this temperature and nutrition thing.

¤=[Post Update]=¤

Posted by Constance (here)
Bubu, keep up the great work! I'm going to have to link this to my natural homes thread.



Constance

Yes please its intended for everyone interested.

[Bubu]

By the way this project is ongoing. The drier is not constructed according to plan as it is an experiment to verify concepts. I use scrap sheet metals and aluminum screen salvage from previous projects. Already there are modifications in the head. I will appreciate if someone can double check if there are flaws with the concepts or maybe have some wild ideas to incorporate on modifications.

[Bubu]

Was trying to upload photo so I can explain further but "failed" notice is on. requesting help from mod.

[Daozen]

Good work Bubu. Solar drying could save masses of food. Check out Samuel Saraiva.

You could try and put your photo on imgur, but there may be other options.

[Bubu]

to give you a visual. This dryer is constructed more like a solar oven plus the air. Really hot inside. No need for a fan Although I will try to experiment with a solar powered, humidistat controlled fan and see if I can improve the efficiency. But I'm sure I can improve capacity with the addition of more metal conductors. I'm still wrestling with the maths as to how much or what percentage of the metal shall be exposed to the sun and air to get the optimum heat per unit area of collector. I will report back but can take time so just watch this thread if you are interested.

[Ron Mauer Sr]

Some construction ideas and pictures of solar food dehydrators are on my blog

Some say 125F is the max temperature for dehydration to prevent loss of nutrition If the temperature is too high, the food surface may dry too quickly and prevent the interior from complete dehydration. A tiny solar electric system to power a fan would be useful for temperature control if grid power is not available.

http://ronmauer.net/blog/?page_id=2383