Brian White

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

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.

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!

In another forum, on the topic of steaming soil and chopped weeds,  someone posted a link to terra preta and from that link  I found "Slash and Char"  and that was interesting, (actually a lot more like what happens when you solar cook the woody material).  It probably needs some sort of equipment to distill off the wood "steam" to collect the chemicals (methane and wood acid, etc.) in it.   Probably some are insecticidal, etc. I think that if you are using solar heat to do the job,  it can be more controlled and also more likely to get the carbon trading money that is on offer in some poverty stricken countries at the moment.   https://en.wikipedia.org/wiki/Slash-and-char  

Maieshe Ljin wrote:This is very interesting.

I was especially surprised when you mentioned the mushrooms growing in one batch! But we do steam mushroom media usually before adding spores or spawn.

My theory as to why it seems to work so well, despite what we know about soil microbes helping plants, is that the seed contains epiphyte and endophyte microbes that are able to colonise the soil more easily without competition. However, it might be beneficial to try adding a little soil in from the wherever the plant is growing very well unsterilized so that there are more of these beneficial microbes.

There is a similar system that used to be used in Europe. I forget what it is called but they burnt sod, mixed it with manure to compost, and then spread it on the fields. Apparently this built up an extremely rich soil that is still in existence to this day. However it was not highly sustainable because it stole the topsoil from heath-land.

Hi Maieshe,  ink caps came up in several places pretty quickly. I put lots of crumpled mushroom block in with steamed grass clippings into a half barrel  and so far, one ink cap (and I forgot to photograph it).  But you never know, fall is coming,  I might have a massive bloom of edible mushrooms under my tomatoes,  or maybe nothing at all.  Its the first time for me growing mushrooms. I was also helping my friend grow mushrooms and she is having good success.  BUT she is envious of my weed free planters!  And she would like a tracking solar cooker!  I can't make one for her because I don't have simple tracking yet. (If I do it long enough, someone in China will notice, and they will start making timing trackers for about 15 dollars each.  Anyway, she is not going to be around to swap out soil 2 or 3 times a day either, plus the neighbour children can get into her garden.    You can't have experimental stuff with kids around  until all the kinks are ironed out.  

I looked up on Wikipedia the other day and it turns out that  Slash and Burn is still used to some extent all the way from the polar regions of Finland to the tropics of India.  Even in Ireland where I grew up, they burn heather and gorse off the hills to let sheep graze on new shoots and on grass.  Millions of tonnes of peat has burned when they do this.  In agriculture, typically, they cut down trees and brush, dig up the roots and weeds and  pile it up to let it dry, and then burn it and spread it.  (or spread and burn it).  The ash and "biochar" improves the soil for a few years and the burning heats the soil and kills off significant amounts of weed seeds and pests and plant viruses in the first few inches of the soil.  So anyway, I started doing a solar cooking version of this last year.   This year, (to protect the reflective plastic tape on my solar cooker, I used less water so it didn't bubble out and spill and melt or damage the coating).   When I cooked  damp weeds and also when  I mixed damp soil and weeds, some of the weeds burned in the pot.  So, yeah, I got biochar.  BUT, the cooking was slow.  Next,  I put a small chamber in the pot with wire mesh over it so I could have water boiling in the chamber and a layer of chopped weeds over that then layers of soil and weeds till the pot was filled.  I reasoned that the steam from the boiling water would rise up through the soil, and very quickly transfer the heat and get faster cooking.  This worked! I have been using the soil weed mix for a few months now and plants do really well in it.  There are no weed seeds and that is a bonus. Saves a lot of time.  In my curved planter with  6 inches of solar cooked soil,  I was surprised because vetch seeds have grown up through the 6 inches! But it is easy to pull them because they have such long skinny stems.  The solar cooker that I used is approximately 0.9 horsepower,  and it has tracking and full sun from 11 am till 7 pm right now.  So its an 8 hour day for my little horse on sunny days, and days off when it is cloudy.  I steam 3 ten liter pots of soil per day now, and when the sun was higher and I got an extra hour or so, I was able to steam 4 pots a day.   Anyway, I made a video about the process.  I guess first crop can be stuff like lettuce, tomatoes,  onions, cabbage and later on, root crops.    

Rebecca Norman wrote:I've used a couple different kinds of solar cookers at our school in Ladakh, which is high desert, so it's ideal for solar power.

The reflector box cookers are great for the gee-whiz factor, but we never used them regularly. They can bake a small volume of items, and do better with sweet things than not, because I guess the sugar browns nicer. Baking is not a tradition here, and the box ovens we have had were too small to really produce much. I have met people who claim to cook other things in a box cooker, such as rice, but when we tried it, it fogged up the glass and the whole thing cooled down. We have two sitting around impressing people but not being used.

Parabolic reflector cookers that concentrate the sun's rays with a roughly parabolic disk of shiny material have been much more effective for us. The small ones, about 4 feet diameter, work pretty well, but you have to go outside and turn them every 15 minutes or so. They are too small for the numbers of people at our school, but they would be great for cooking for 2 or 3 people, I think. These are more like stovetop cooking and you can cook all kinds of pots of food on them. I've seen two models, one with the dish low to the ground and the pot raised, and one with the dish and the pot at about waist height. They are pretty affordable to put together from shiny aluminum or steel if you can make the frame. In your first week of having one, it is a rite of passage to burn holes in some clothing that you think will dry quickly by draping it on the solar cooker.

At our school we use a big Scheffler reflector type cooker, with a parabolic dish about 8 or 10 feet in diameter, focused on a hole in the (non-flammable) wall and a secondary reflector shining up to the pot. This works very well, and we can cook big pots for 50 people on it. Ours have gone through two models of self-regulating mechanisms, where you'd weight the thing down with a stone, pull it over towards the east in the morning so the stone goes up, and a tick-tock pendulum mechanism would control its speed turning back to the west as the stone pulled down. Both mechanisms failed, and now we just turn it by hand every 15 minutes or so. Either way, you have to make a seasonal adjustment every few weeks. It's a bigger investment, and rather complex engineering to get the angles right, I think. I don't even know where the designs are; I hope they are online as Scheffler cooker. Ours was installed by a Swiss guy in the 1990s who came around and trained lots of local people in how to fabricate and install these, and we've been using both ever since. The others that were installed in our region are no longer used. User motivation is essential.

 Hi Rebecca,  are you still in the high desert?  My parabolic  "Sun Scoop" works a little similar to the Scheffler,  it's just a lot simpler to adjust  and you can DIY it. I cut mine from an 8 by 4 sheet of abs plastic,  and I made it to have an almost exactly 1.5 sq meter reflector.   There was some material left over from the ABS sheet,  but I still can use that to make a smaller parabolic dish, roughly of 1 sq meter collector size. I hope you look at my "waterwheel winch" method for rotating the dish,  you could probably use it to work your Scheffler too.     I would hate to turn my dish by hand! My seasonal adjustment is pretty easy.  Also, different from Scheffler,  the amount of light collected is the same in Winter as in Summer.   (Scheffler dishes collect a larger area of light in Winter than in Summer).   There is a huge need for a simple "timer",  ideally one that doesn't break down easily or a photodiode arrangement to tell my waterwheel winch when to stop and start.   Something like that could be made for under $20, and enables DIY tracking on equatorial mount everywhere in the world.  Thank you,  Brian

Today,  I have been steaming weeds to grow mushrooms in.   I don't know if it will work but it is worth a try.  It takes about 2 hours to steam up a batch.  I pick them,  then run the lawnmower over the weeds a few times and pack them into the 14 liter pot over the water chamber in the pot. On top I put a shovel of soil (because when I started doing it, the weeds at the very top were not getting so well steamed).  The soil seems to trap the steam better.  I guess I could just buy a steamer but that is a lot more expensive that a free pot.  Thermometer in the middle at the top is my guide.  If it is over 98 C, that is steamed enough for me.   I don't know how much energy the solar cooker is transferring to the pot,  but at least as it heats up, it is probably over 500 Watts.  I did a boil test (heating 10 liters of water) prior to setting the pot exactly at the focal area, and that was when I noticed that significant light was missing the pot!  The very best heat up from that test was  just under 600 Watts when the water heated up from 27C to 33 C in 7 minutes.  Then as the pot heated up,  the water and the pot started radiating heat, faster and faster so even though it was probably still 600 watts, the actual amount transferred to the water got lower and lower.  I have mushroom spawn in the soil in the greenhouse and I am also putting some spawn in cooked weeds in an old aquarium and in a half plastic barrel.   I will put pallet wood on the top with little gaps, then turn it on its side and hopefully the mushrooms can fruit between the gaps.  I might do something like that with the aquarium too. (Turn it on its side and let the mushrooms grow out the side).   I will much more heavily inoculate the cooked weeds in the half barrel and in the aquarium. Hopefully that will prevent undesirable fungi from establishing themselves.    But I'm a bit scared that the glass might break in the aquarium if the glass is on its side.   Today I did 4 batches of weeds and it is nearly enough to fill the half barrel (along with some of what I cooked up yesterday).   Tomorrow,  hopefully, it will be another nice day and I will get enough weeds steamed to fill the half barrel.   Anyway, here is a video from yesterday of where I dug mushroom spawn under steamed soil.

Ben Zumeta wrote:

Brian White wrote:

Anne Miller wrote:Hands down the compost tea is better.  




I like your idea for using a solar cooker, but this is a straw man argument about compost teas. I could give a long, redundant explanation of soil biology that has already been provided abundantly on this forum, including in the thread provided. It also appears that information is not welcomed by the OP though, so it would be a waste of time to repeat it here.

Anyone who has made really good compost, extract or teas would not say “it has no energy in it” .Especially if looking at it under a microscope, or its effect on plant growth. It has billions of living micro organisms cycling nutrients and energy, which the plants get looped into with application. These microbes live on and in the plants, greatly improving their ability to access and cycle nutrients, water and energy.

   Hi, Ben.  My argument is correct,  there is more biological energy (carbohydrates, etc.),  in the weed soup than in compost tea,   if you boil chopped up weeds,  juice is extracted from the weeds,  (just as spider mites, and aphids extract plant juice to live) and also some complex organic compounds get broken down and become part of the weed soup.  If you dilute weed soup and use it when you water your plants,  you are feeding the bacteria that are already there in the soil. No new bacteria needed. They will use the carbohydrate to multiply.  Protozoa already in the soil will eat the bacteria, worms will eat the bacteria,  die, decompose and nutrients will be released in forms available to the plants.  I think that fungi will especially benefit from weed soup carbohydrates, especially because they are already broken down somewhat.    So, yeah,  garden soil already contains a vast number and variety of bacteria and fungi.  It is easier to feed the ones that are there than to add more.   I don't know how things work with foliar applications of compost tea. People seem to be hyper critical of new stuff,   I did a compost tea brewery,  (actually have one going now),  so not sure why people think I am so against compost tea.