Tuesday, April 10, 2012

underground solar cooker

This is going to be one of those infamous “what I had for dinner last night” articles, but fear not my gentle minions, it all has a valid point.  This weekend I did three things you might be interested in.  I wrote some articles, I set up my batteries differently and I constructed a new and improved solar oven.  The articles are to cover the coming two days I won’t be able to post a regular article due to my extended weekend vacation going down to visit my dad ( I visit once in the spring and once in the fall ).  This coming Friday and the following Monday, you will get these two “better than nothing” articles.  They are only two thirds the regular length, and I can’t promise they will be all that great.  On Saturday, I sat down to write them and half way through the clouds started rolling in.  So I was in a bit of a hurry knocking them out.  It won’t be the worst I’ve ever written but I doubt it’s the best.  But as I said, better than nothing.  Come next Tuesday, it’s back to normal. 

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For the longest time I’ve wanted to improve my battery set-up.  The two 12v batteries set side by side in their designed RV compartment are very hard to work on.  You almost need three arms to hold them in place so they don’t tip out and fall down, tearing out wiring as they go.  Just topping off with distilled water is nearly impossible.  Which is why I took out one battery about a year ago.  I had two 450 amp marine/RV batteries.  When one went bad I took them both out, replaced them with a 600 amp, and used the surviving 450 as a back-up I topped off once a month with the generator.  Once the gennie died, I was unable to do that.  So, I’ve really been motivated to get that smaller battery hooked back up to the solar panels.  Yet, it was impractical to switch from one battery to another, or to put both back into the trailer.  So, this weekend I took a big Styrofoam cooler ( with lid ) and set that on the ground next to the trailer and the panels ( my panels are on the ground set on wood pallets that are at an angle set up on plastic totes and tied down with ropes ).  I placed both batteries in, wired them together, and then took extra wiring and hooked that up from the batteries to the contact wires in the trailer.  Actually, I couldn’t go into town, it being Sunday and nothing was open, so I Jerry-rigged it.  I took my old jumper cables out of the non-running truck and clamped them on the battery terminals and then on the trailer wires.  It works just fine, and now instead of 600 amps I have a 1000.  Remember, a good rule of thumb on 12v’s is that if you take the amp rating, that will be the same as the watts you can use before the battery is half drained ( on marine batteries, this isn’t a problem as they are designed for this.  Car batteries are not- that would quickly kill the thing.  Spend 10-20% more and buy marine/RV batteries ).  So, using fifty watts a day for lighting and a smidge of TV, I can now get through several weeks before I need to panic and soil myself.  The record ( for me ) for cloudy days is two weeks here in Elko, and six days is the average maximum.
With the other cooler I had, I made a new solar cooker.  As you might recall, my old cooker was a hunk of crap.  It was an old steel medicine cabinet with a wood back and a wood door, with a square cut out of the middle and glass glued on.  I put insulation on the inside sides, and the thing never worked very good.  I knew it was a poor design, but since I just used it to pre-heat water eight months of the year I didn’t care.  Even at minimum efficiency, the propane I saved doubled or tripled the time between fill-ups ( in the winter, with coffee, dinner and bath water heat-ups, I refilled the five gallon tank once a month.  Outside of winter, just getting the bath water 60-80% heated up in the solar cooker stretched out the refills to once every two to three months ).  In the summer, heating all day, the water got hot enough that it only took a few minutes on the stove to get to a boil.  But the new design is a vast improvement.  It took four hours with no clouds and the temperature only 60 degrees, and the water was so hot it was billowing steam.  I didn’t need to heat it on the stove at all.  But as a test, I put it on the stove and it immediately started to form bubbles on the bottom.  That’s how hot it was.  Talk about a fuel saver!  Now, not only does this work great, it is a retard friendly design.  No sawing or gluing or trying to screw wood to metal.  In fact, I can’t believe anyone would want an above ground cooker after they try this.
Dig a shallow hole, say a foot deep.  Leave a 45 degree angle so that the bottom of your Styrofoam cooler is tilted towards the sun.  In other words, your hole is a V, the south side of the cooler opening level with the ground.  Pile up dirt on every side of the cooler ( before you start, wrap the thing in tin foil.  If not the whole thing, at least the inside and any part exposed to the sun ).  Have the dirt on all sides of the opening, level with the parts that will be covered with the glass.  If the glass is long and extends east and west, have extra dirt on the east and west level with the glass.  You want the window laying flat with no openings for air.  I had an old piece of window glass still in its frame, and this makes it easy to just lift off the whole thing.  That is it, other than a piece of black metal behind the cooked item.  I placed three water filled Mason canning jars on a piece of wood ( the wood lifted the jars off the bottom to have direct sun exposure ) and hence my hot water heater was born.  I will be trying food cooking soon, but this was just a quick and dirty test.  Four hours, not the hottest day around, and boiling ( literally ) hot water.  I imagine you could do this without burying.  I didn’t test one buried and one not.  I know the cooler is the insulation.  But burying it surely makes it 100% insulated.  And, it does make for a cheap ( free ) stand and wind tie-down.  I love underground.

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  1. The solar cooker sounds like a great idea Jim, particulary in the desert where fuel is at a premium. I'm thinking of making one for myself?

    For times that you do not have sunlight, you may consider the soda can stove? There are several variations on this stove; here's one of them:


    But it's very cheap to make; the price of a soda can and some denatured alcohol.

    For bathing, I would get a couple of the solar showers from Walmart for $10.00. and perhaps, on very cold, sunny days, set them in you now defunct truck, that could be startegically repositioned facing southward.


    It's basically a black bag, with a shower spout on the end.

  2. Solar heater/cooker
    Lay a sheet of plywood on the ground.
    Place an old tire on the plywood.
    Place a pot of water inside.
    Cover with a sheet of glass.

  3. When on vacation, or if you just don't have time to write, you might post one of the Bison Newsletter essays, or long excerpt from an essay. That would be much BTN. It would be entertaining, instructive, and encourage the reader to buy the newletter. $4.00 is a bargain.

  4. Great idea on the underground solar cooker. It's these practical ideas that work that makes your blog the best out there.