Wednesday, July 27, 2011

Parabolic solar cooker

 Today I want to quickly tell you about a new technology that we are considering in our community development project.  It is called a parabolic solar cooker.  We have worked with solar technologies before.  In this first picture you see a solar oven that was made by foreign organizations here in the late 90’s.  This cooker depends on dark colors and direct sun exposure to absorb heat.  There are 2 lids to this cooker, the top lid has a reflective inside, and the lower lid is glass.  Inside the glass lower lid the oven cavity is painted black.  Likewise the thin tin pots to be used in this cooker are painted black.  Heat is kept inside the glass lid.  We have cooked a variety of things in this cooker, and love it.  Baked potatoes take about 6 hours, chicken 3 hours, and you can also bake bread or cakes in it.  The great thing about this is that it does not burn food.  Unfortunately because it cooks slowly, it requires a lot of planning.  This cooker was promoted in local markets, for around $20, but it never took off like the creators hoped.  We are sure glad to have one, however, because it’s a lot better than lighting an oven in your house when it’s already 93 degrees!

The other solar technology that we have been using is a simple solar water heater.  These were produced by a renewable energies project until recently.  They also did not take off in the local market, but again, we love ours.  We used this every day when we lived in the mountains and did not have indoor plumbing.  It holds over 10 gallons, and with the amount of sunlight we get here we could heat water warm enough for a bath from February to November.  The heater again depends on direct sunlight and dark colors to absorb the heat, and a glass cover (which was broken by a small boy) to keep the heat in.  The simple solar water heater is pictured below.

Now I will tell you about the parabolic solar cooker, which is pictured below.  This device is unique from the previous two, in that it reflects and focuses a beam of light onto the bottom of the pot you want to heat.  Any pot under the sun will get warm, and warmer still if you paint it black and cover it with glass.  This, however, is something altogether different.  Notice the gleaming light at the bottom edge of the kettle- that’s the focused beam of light that is heating the water from the bottom up.  The base of this satellite-dish-like thing is fully adjustable so that the user can face the sun and focus the beam of light right on the bottom of their pot.  When it is in focus, you cannot even look at the bottom of the pot because it is too bright.  The demonstration we saw boiled water from a deep well in less than 20 minutes.  The demonstrators were also showing how intense the heat source was by putting pieces of cardboard in line with the beam of light- and they would immediately catch fire!  Chinese companies are making these cookers now, and local organizations have started to bring them in and sell them for $80.  Much more expensive than the older cookers, but from the reports we hear, they are selling.  The speed of cooking and boiling water is perhaps the reason.  I would like to see if local steelsmiths could make a similar shaped dish out of old barrels, and fit it on a concrete well-ring as a base.  Then if we could get the reflective tape, I bet we could produce these for less than half the cost.  Here is a list of some of the problems that would be eased if this technology spread across this country:
  • ·      Less respiratory illness from indoor open-fire cooking.
  • ·      Less eye problems for the same reason.
  • ·      Less small children suffering life-altering burns from falling into firepits.
  • ·      Animal manure could be used as field fertilizer rather than cooking fuel.
  • ·      Less harvest of brush and trees, so less erosion and better farming environment.

Anyone want to come help me figure out a more affordable design?

1 comment:

  1. Wow, this is fascinating! Once again, thanks for posting. We love to learn!