Discussion on the advantages and disadvantages of "out-of-axis solar cookers"

In the mid-1970s, there was a "single pole pot rack" solar cooker in China. This solar cooker was first made by Mr. Ren Hongjun in Gannan Prefecture of Gansu Province and was promoted to hundreds of units in the Liushun Commune of Lintan County. At present, in some provinces and regions in western China, most solar cookers are of this type.
This type of solar cooker is still a rotating paraboloid, but the pan supports are only connected to the support. When adjusting the elevation of the solar cooker, the pan support does not move with the solar cooker. Or, no matter how the solar cooker adjusts the elevation, the pan support is always relatively fixed to the ground. This type of solar cooker is an "out-of-axis condenser solar cooker." Ordinary we call the "parallelogram-shaped pot rack" solar cooker can be called "axis condenser solar cooker."
It is difficult to fully compare the advantages and disadvantages of the "out-of-axis concentrating rotating parabolic solar cooker" and the "axis concentrating solar cooker". This is due to the fact that most solar cookers are hand-manufactured and their production process levels are different. The performance requirements for solar cookers vary from person to person, from place to place and from time to time, and their respective advantages and disadvantages cannot be met on every solar cooker. Be reflected. Relatively speaking, off-axis concentrating solar cookers have the following advantages and disadvantages.
The advantages of this solar cooker are:
1, because the pot rack is not linked with the stove body, in the frequent adjustment, the pot rack does not oscillate back and forth, so that the pot rack "branch" produces less vibration, more safe and reliable when used;
2. The pan support rod is perpendicular to the ground, and is only connected with the bracket, and the weight of the pan utensils and the food will not act on the stove body, so the design of the stove body is relatively simple;
3. Under the same change of the solar elevation angle, the displacement of the spot on the bottom of the pan is small, and the work performed under the same conditions can have less adjustment times (for reasons omitted);
4. For an off-axis concentrating solar cooker with an off-axis cut-off surface, the area of ​​solar radiation received by the cooker is greater than the solar area's cut-off area when the oblique angle is negative;
5, the overall structure is simple, easy to disassemble, the cost is relatively low.
Of course, due to the off-axis concentrating solar cooker that allows the sun to splay, it also has the disadvantages that are insurmountable and often fatal:
1. In the use of solar cookers, the solar elevation angle at most moments is far from the “designed initial solar elevation angle”, the oblique angle is large, astigmatism is severe, and even a large amount of reflected light may not be intercepted by the bottom of the pot, so overall Poor thermal performance;
2, generally not suitable for use under a relatively small solar altitude;
3. When the angle of inclination is positive, the solar radiation received by the solar cooker is less than that of the solar cooker;
4. The design work is complex and it is difficult to obtain a design scheme with a wide range of applications.
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