How to make a Better solar dryer

[julian]

HI there, I was here sometime ago. I wanted to share to you my project. I notice that everyone seems to be doing this the wrong way. I did the wrong way myself. I copied but realize that it was wrong and was right on the realization:). I posted this on another forum so for ease I will just copy and paste here. You are welcome to ask questions. In fact I want you to because this is an ongoing project. And I could learn something else before I do the modifications.

These are my conclusions as of now but I could be wrong.

"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 everyone seems to be copying the wrong thing 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 be carried by water. 
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. "

"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."