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Z0rb

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I am new to this forum, and right up front I will say I know very little about physics in general. That does not however limit my ability to question and ask for help from people in the know.

Here is my dilemma. I have a small Fresnel lens approx. 6 cm X 15 cm. Or 90 square centimeters. I would like to know how much power in Watts this is really focusing.

I did a little math under the assumption of each square meter receiving 1000 Watts of solar energy on a sunny day at the equator and came up with about 9 watts of calculated power at the focal point.

This of course is a figure that assumes there is no loss in the system. So to get a better idea of how much power is REALLY at the focal point, I want to make some measurements.

I have a K-Type thermocouple hooked into a meter that can read up to 750 degrees Celsius with moderate accuracy. I’ll place the thermocouple at the focal point. The focal point appears to be about 1 cm in diameter. The diameter of the thermocouple is about half of that.

Is it possible (and if so can I have it explained to me), to calculate how much wattage is at the focal point, by taking a temperature reading over time?

Any help or explanation would be great.

Thanks