Wednesday, March 28, 2012

My experiments with Solar Cooking - part I

It all started off with a post by Dr. Gananath on sukhijeevana if anyone was interested in making Parvati solar cooker. So I started reading up about solar cookers and thought that it was trying out since it did not look too complicated and needed only simple easily available materials to make a low cost version.
My first version did not work. The rice and water remained pretty much the same after more than 4 hours in the sun. I have to admit that I did not follow the instructions precisely as mentioned on the website (angles of different pieces, aligning system etc.) Also figured out that I had not used a black vessel and had not covered the vessel.
I was reluctant to paint a vessel black (issues of which is a safe paint, the vessel may become useless for other purposes). Luckily there was a teflon coated black pan at home which was the candidate for iteration 2. This was covered with a plastic sheet to retain the heat inside. There seemed to be some more activity this time as water vapour condensed on the sheet. However raw rice remained as it is. The temperature inside the cooker was around 50degC. My questions to the inventor Sri Ravindra Pardeshi received prompt responses. I felt that the
precision of construction plus the mechanism for aligning the cooker to the sun would be critical. I was not ready to take up these steps. Further my reading up (this site is a good reference) revealed that while the panel type to which the Parvati cooker belonged to is one type of simple solar cooker the better option would be to build a box type. This need not be turned to follow the sun while cooking, can reach higher temperatures etc. After discussions with friends Vasant Jajoo who directed me to his friend Rakesh who had been using one finally led me to build a box type which I would say is a mix of Maria Telkes type with the Heaven's Flame. Two carton boxes were used (one inside the other). I used black color paper inside the inner box. An old glass sheet was available which was reused for the top lid. It was a little thin and unfortunately cracked during use. The top reflector portion was a spatial geometry project figuring out t
he angles and sizes! Pieces of cardboard were used with aluminium foil pasted inside.
With this version we were able to finally "cook" rice. More on the results and operational challenges in a separate post!

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