Examples of Results in 2011
@In the Winter Sciece Camp 2011, we made three concentrator type, three box type and five panel type solar cookers. I would like to introduce you some interesting results and facts clarified through the analyses. These knowledge are new to me and I enjoyed them a lot. Do not try to mimic the successful ones but try a new improvement. I'm not expecting an old success but new findings by you!
It looks like a panel type Educooker002 at the first sight, but it has a concentrator in the center. Considering the size of the concentrotor, it does not seem to increase the lights on the pot. Of course, the cooker itself has a sufficient cooking power even without the concentrator, the students were able to enjoy their curry.
The shape of the concentrator of this cooker is a polyhedral pyramid. They checked the concentration and the position of the pot using our laser matrix light source. Because the pot does not contact with the surface of the cooker, the heat loss by the conduction was suppressed. They also succeeded to cook their curry.
They thought over and over to determine this shape but as a result it looks very much like Educooker002. They also raised the position of the pot to prevent the loss by heat conduction and at the same time, to utilize the reflected light coming from the bottom of the cooker.
This is a very simple panel type cooker consisting of only three panels basically. If you combine two panel in the form of "V" with the angle less than 45 deg., the light entering the combined reflector from the front will never come out even after any times of reflections. So eventurally, all the light will be absorbed by the pot. Their shape is effective only in winter season but showed a very good performance in the test.
They insisted that they had made a panel type although it looked very much like a concentrator type.@They also said that it was foldable.
This one has a pretty flower-like shape. Of course they knew that the outer ornaments were not necessary as a reflector, but they thought a solar cooker had to be attractive. Unfortunately, because of the large area of the reflector, the resistance to the wind became to large for the cooker to keep the precise angle and direction of the concentrator, and the temperature of the food did not rise so much.
They tried to make a parabolic shape but contrary to their intension, it became a perfect half sphere! Spherical reflector can work and has an interesting characteristics if it has a enough size. Yes, because of the size which was too small, it could not perform well. Please refer to our large spherical solar cooker for more information.
Our Large Half Spherical Solar Cooker.
This one is another enlarged Educooker004. Because they made the reflector precisely, their result was the best among the concentrator type solar cookers but all the foods cooked by concentrator type solar cookers were not eatable. It was mid-winter and was very windy. Even without the wind, the heat loss by convection becomes 35-40%. To compensate the loss, you need to make a very good concentrator with adequate size.
This one has a typical shape of box type, but by the advice from our student helper, they made the depth of the inner box shallow and the temperature rised good enough to cook the food. See the results of 2009 Science Camp.
This box has a tranparent front wall. I like their idea and if you employs a double-glazing, I'm sure it will work. But for their method, they needed to sacrifice the insulation and it did not result in the outperformance. Anyway, it cooked the curry perfectly.
To tell the truth, I did not expect a good performance for this box type. I thought the size is too large. If you enlarge the box type (or panel type) solar cooker two times in length, the projectional area of the cooker becomes four times as large.@As a result the energy of the sun the cooker can utilize will be four times as large. But if you use the pot which is two times as large in length, the volume will be 8 times as large. So you need to reduce the size of the pot. Usually this makes the cooker to aim the pot with reflected light difficult and the efficiency will drop. In their case, they reduced the volume of the inner box by putting a reflector inside the box and making the depth very shallow. By this improvement, the performance of the cooker was one of the best.
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