Solar Cooker Trial

Alacrates's picture

I'm fairly new to sustainability/appropriate technology, overall - I only got inspired to get my hands dirty with JMG's Green Wizardry book, and I've kind of been using that as a template to learn from, along with whatever random inspirations I came across...

In the chapter he had on energy & cooking, he outlined haybox cookers first (I made one, and it worked well.) Solar cookers came after that. I found a model I liked on instructables.com that I liked, and made a version of that last year. I think I finished it on Sept. 8th last fall, but once I got it done, it turned out to be such a cold, cloudy autumn in the area I live in, I never got one sunny afternoon to try it out in until yesterday. (https://www.instructables.com/id/The-Solar-Baby-2-Solar-Oven/ the template I worked from)

Anyways, it worked alright, it hovered around 220F and cooked the beef roast I tried out (very slowly) to 140F, over about 3 hours. The solar collector lid didn't fit very tightly to the base, you could feel hot air seeping out through the gap. I'm hoping that if I add some more rubber gasket material between the two, that the temperatures in the oven will come up into the 300F range.

(If anyone is wondering how low oven temperatures can be to still ensure that pathogens are eliminated, I personally think that the research that Modernist Cuisine did under Nathan Myhrvold is the most informative, which I think basically showed that if you can sustain temperatures of 120F - 130F for long periods of time, you can rid the meat that you're cooking of pathogens. With pathogen reduction, it is always a matter of temperature and time duration for which that temperature is held. Goverment regulations are usually assuming that you are holding a temperature for less than 30 seconds.) https://modernistcuisine.com/recipes/low-temp-oven-steak/

The beef roast I tried out came out to 140F, and, once I allowed it to cool, came out medium rare and tender.

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Alacrates's picture

Cooker in the front yard.

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Alacrates's picture

Pan from the cooker...

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Alacrates's picture

... finished roast....

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ClareBroommaker's picture

That looks like a good sturdy solar oven. Really well made.

Our first solar oven was just a regular brown cardboard box lined with aluminum foil, including the flaps. There was a piece of glass from a picture frame. First thing we cooked was whole potatoes.

After leaving our little foil box in the rain, we decided to purchase a manufactured one, and have been happy with it.

Here is a pot of solar cooked vegetables to go with your roast. Butternut squash, celery, onions.

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Alacrates's picture

Thanks Clare! It might be a little bit over sturdy, haha, it is pretty heavy and large. The top solar collector does come off the base though.

I definitely hear you about buying manufactured models of various green wizardry apparatus. On one hand, for some projects like this one, I like that making them requires some ingenuity as how you are going to make your version, how you are going to find the materials, etc. On the other hand, for larger projects, I'm not really sure I end up saving all that much money (!) and certainly it takes a fair bit of time.

For instance, I was thinking of getting involved with vermicomposting, and I attended a workshop were they had make your own models with rubbermaid bins (which I may still do), but I was looking at some online for about $150, and they looked very nice and easy to use, so I'm wondering hehe.

Nice little pot of vegetables, I got to get one of those kind of pans, I remember using them camping when I was a kid.

Blueberry's picture

That is one fine looking roast! Something I remember from my past travels about heat. If you take a 2L soda bottle and fill with clear water and place in the sun for 5-7 hours will be safe to drink. Think the info was from WHO. The water never gets that hot but does the trick.

Alacrates's picture

I was a little worried when I couldn't get the temps up very high, but actually the long slow cook produced some very tender meat. In the future I might quickly sear it first, which should also speed up the cook time - I think one reason it took so long is that the meat had to come up from fridge temperatures first.

I hadn't heard about the soda bottle water method, but if it works I'm wondering if it works on UV radiation rather than heat? I know the UV units we install in water lines basically damage the DNA of bacteria (I believe) and makes it so they are unable to radiate.

I'm thinking the soda bottle method might be a good first step, in some sort of disaster scenario, followed by filtering it through some charcoal, gravel and sand layers?

dtrammel's picture

That's a tasty looking roast!

Its in the mid 70s here, but soon it will be back up in the 90s. When it does, 'm going to try my own experiment of making wax candles using solar heat. I figure a good reflector and a blackened large pot that I can fill with water and submerge pickle jars (have a ton of them), to melt solid wax and make emergency candles.

Alacrates's picture

Thanks Dtrammel!

Thats an interesting idea for making the emergency candles, definitely post a picture if it works out. I like the idea of saving energy whenever a person has a chance, if only to build up the habit.

Justin Patrick Moore's picture

Hat's off to you on that one. Looks good. The most I could do now if we lost gas to the old Chambers stove is use my coleman camp stove until I run out its fuel and then start making foil meals or cooking over coals out back in the fire pit or on the grill. A solar oven looks nice to have in an outdoor kitchen setup. (Temps here in the 70s today too-- last night it was in the 50s. )

Alacrates's picture

Thanks Justin! Yeah, I wasn't really even thinking about disaster type scenarios, I guess it might be useful for that - As it is, it is actually fairly impractical for me (!), for a working person for the time it takes to cook something and hours that I have to sun before it's shaded by other trees and buildings is pretty short, I think it's only going to be for weekend afternoons where the sun is out. (And its pretty cold here through a lot of the year!)

I suppose in some sort of disaster scenario, one might have more mid-day time for cooking though :) Nothing wrong with having some fuel stored up! But I guess that using a solar cooker could extend the use of stored fuel.

Justin Patrick Moore's picture

I guess it could be a kind of deindustrial slow cooker. Put your meal in before heading out to the ruins to salvage scrap for the day! Hope you are well!

Blueberry's picture

Your Coleman stove is it a backpack stove or a green suitcase stove? I still have my green stove from high school over the years have picked up a few more for spare parts, but with a good cleaning they are all working. Try an only run camp fuel you can run gasoline (petrol) if things went south.

Justin Patrick Moore's picture

The one we have is a green suitcase stove -and yup, got some extra camp "white" fuel for it. I could buy a few more just in case. Having some good camping gear often can double as bug-out or bug-in kit.

Blueberry's picture

Justin Patrick Moore's picture

Hey, thanks Blueberry. That sounds like a good project. Have you done this yourself?

Blueberry's picture

We have fire! The Converter will work with both the large and small 2 burner stove ( 413 series and 425 series also the dual fuel ) Have no idea if it will work with a three burner. Century also makes a converter.cost is like 4 times from the current seller on amazon Will try and post a picture.

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Blueberry's picture

The hose I linked is 7 feet you only need the 4. https://www.amazon.com/DOZYANT-FQ01-Converter-Replacement-Tank-Safety/dp...