Sunlight in Watt?

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I need to measure the amount of sunlight that enters a room over a given period. I assume I'll need to get my hands on some device which can measure this, but in the meantime, is there a way to approximate how much light/energy enters the room at a given time? The best would be to get a Watt approximation...
 

chroot

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The power at noon on the equator is about 1 kW per square meter. However, sunlight is incredibly variable, owing to time of day, time of year, angle of the window, direction the window faces, latitude, cloud cover, trees or other obstructions, you name it.

- Warren
 
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Yeah, that's exactly what's making it hard...
 

Ivan Seeking

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Buy a solar cell having a known efficiency curve [data usually found online] and attach it to the glass in the window, facing outward. Apply a constant load the the solar cell - a resistor. Meausure the voltage across the load throughout the day and write down the data. Calculate the total power produced for any point in time, compensate for the efficiency, and scale up for the size of the window. You can do this for a few bucks though you may need to buy a $5 meter at Radio Shack. Also, if you want the total energy over a period of time then the final answer for would be in watt-hrs, not watts.
 
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