I read that solar radiation gives approximately 1000 W per square meter. I am just curious how this was measured, since most of the radiation is usually not absorbed.

I don't think it's hard to absorb all effectively all radiation in a small area. A black cloth would be pretty good.

Try searching for info on radiometry.

I read that solar radiation gives approximately 1000 W per square meter. I am just curious how this was measured, since most of the radiation is usually not absorbed.

The probe (actually a little square-shaped device) used to take the measurement is black with a non-reflective coating and a convoluted surface - much like the foam used for acoustical dampening in a sound-deading room.

Solar collectors, for example, have known, measured efficiencies. So, you stick a solar panel in the sun and measure the wattage. Then divide by the efficiency of the panel and you have the wattage incident on the panel from the sun.

Easy.

Solar collectors, for example, have known, measured efficiencies. So, you stick a solar panel in the sun and measure the wattage. Then divide by the efficiency of the panel and you have the wattage incident on the panel from the sun.

Easy.

Mmmmm... Actually, that's exactly backwards.;) The measurement is made with the probe I just described and then compared to the PV cell's output and the efficency is then computed.:D