Experimenting the Positioning of Cooking Pots in Solar Cookers

During visit to solarcooking.org site there is a topic requiring attention, i.e. whether to stack the cooking pots side by side or to stack them?

While experimenting with modified funnel cooker "Parvaticooker" we found that stacking works better. Details of our experiment are given below.

Our next goal was to cook 2-3 different dishes. For this purpose we used a large stand and placed three identical pots as above side by side, with 750 ml of water in each. We measured temperature in all three pots after 90 minutes and readings were 70 0C, 77 0C and 77 0C there was no improvement with different positioning pattern.

Then it was decided to work with pots stacked on each other. With available aluminum pots we were able to stack only two pots. We decided to work with stainless steel pots that come with pressure cookers. In aluminum pots we placed 750 ml of water while in SS pots we placed 1 litre water in large pot and 750 ml water in smaller pot. ( SS pots had diameter of 6.25 " , height of big pot is 2.75" small pot is 1.75")

Temperatures recorded after 80 minutes is given in table

	Aluminum	SS
Pot at top	85  0C	85 0C
Pot at Bottom	96 0C	85 0C

This test clearly showed that stacking of cooking pots works better than keeping them side by side in concentrator type cookers

We repeated same experiment with three SS pots stacked on each other.

Temperatures recorded after 90 minutes is given in a table below.  

Top pot	500 ml of water	83º C
Middle pot	500 ml of water	83º C
Bottom pot	750 ml of water	83º C

Three SS pots Stacked	Two aluminum solar cooker pots

From this result it is evident that solar cooker with does even heating of pots in stacked position.

Some friends advised us to use aluminum cooker pots which are used in box type cookers. We again repeated the above experiment by using these containers (Dimensions 6" diameter and 3" height). Temperatures recorded after 90 minutes are as given below.

Top container	750 ml of water	78º C
Bottom container	750 ml of water	95º C

Pressure cooker containers	Aluminum Solar cooker containers

While trying to find out the reason for this variation we found that even though aluminum is better conductor these containers have lids and contact between them is not perfect. SS cooker containers are made to fit tightly on each other. Getting similar aluminum containers has been difficult so far, since people tend to by only SS containers.

Ravindra Pardeshi