Sun Scoop converted to solar dehydrator.

The sun scoop is a parabolic "dish" tracking solar cooker.   It only uses one small section of the actual dish because otherwise the dish would get in the way of the target-focus-cookpot-solar oven.  I finally built a solar oven for the sunscoop and its first job is to solar dehydrate my windfall apples.  I know from previous work with it that it delivers over 600 Watts to the cook pot and it boils off water fairly quickly (more than a liter in a couple of hours when I was steaming soil),  and that it can easily char wood,  so I got to figure out how to get the right amount of draft or wind, to achieve this much evaporation, while not letting the apples, plums or whatever else is in it, get too hot.  I have ran it with the solar oven window  closed up, for about a week, and with the door open a little to let out excess heat and moisture.  Next, I might put something behind the glass to open it a crack,  and maybe air can come in around the window and exit at the back for better draught.  Another plan is to get some aluminum oven "trays"  (the ones from the dollar store) and cut them to make a "grill" (like on some cars in front of the radiator.  The grill would be little squares,  with sides around half  an inch and 2 or 3 inches deep.  Imagine something like a bee hive, except the cells are open at the bottom as well as at the top.   I am going to spray the grill black so it absorbs the light  and converts it to heat in the grill.   This is something that people will have to see to understand.  I don't know how well I can make this grill,  but anyways, I will give it a try.  I went off looking for something ready made that I could repurpose and I found nothing.   Anyways,  I did some very rough calculations,  The solar oven contains about 125 liters of air.  That is approximately 153 grams of air. The heat needed to raise a gram by a degree centigrade is 1.47 Joules.  So  if we could just heat the air in the solar oven (and not the metal from which it is made,  I calculate that 600 Watts would take 11 seconds to heat the air from 25 C to the more or less ideal temperature of 55 C.  I think this means to maintain this temperature (just with air in the Solar oven and no food) we need 11.4 liters per second of air flow!  That is a lot!  Of course, when there is food in, that much airflow is not needed because moisture is evaporating from the food pretty fast, and that process is absorbing a lot of heat.  Anyway,  as I see it,  I have a choice. The grill in place of the glass window to let in heated air,  and  how wide open the back door is, to control the speed of air flow or a fan  to circulate air in the oven, and maybe a valve to let out air and steam rapidly when it gets too hot or humid.    I hope this is fairly clear.   I have figs, tomatoes,  chunks of apples,  and 2 types  of plums in the solar oven right now.  Tomorrow,  I might get the new trays done.  (4 trays).  I think there is room for those 2 plus the additional 4 and maybe a couple more,  we shall see!

Cool idea.
Does the food get very hot while being dehydrated?

Benjamin Dinkel wrote:Cool idea.
Does the food get very hot while being dehydrated?

 It can get too hot now,  I am hoping to correct this soon.  One issue is that I can get a solar powered fan for inside the solar oven, but it has to have a long shaft so the motor is outside the oven. I haven't found one yet.

Frame for new trays is done. It took a long time because it needs to be removable and I am not good at carpentry.