Kind regards

Ghysels Claude ]]>

Not sure how you came up with the 300 Watt. If the concentration ration is the lens area/concentration area = 63 square inch / (1/8) square inch and the total concentrated power is the 38 watt x concentration ration that does not add to 300 watt. I only get 300 watt if I multiply (1/8)(36)(38), which does not make sense to me. Could you please help me understand your process?

Thank you

]]>Yes just change the distance between material to be heated & lens. The focal point will spread. Closer by 3-4″ should accomplish what your looking for. No need to reduce surface area of lens, that would just decrease overall thermal output.

]]>Hello Dr. Goel,

I am attaching the answer from Marty Sangendorf, the author of this post.

The easiest way to lower the temperature is to simply reduce the area of the Fresnel lens. A piece of opaque material (cardboard) with an opening centered on the lens center will do this. You’ll have to experiment to find the correct diameter opening for the day’s sunlight level.

I hope this helps!

~Tami

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