Solar Irradiance Experiment

First, solar irradiance is really just a measure of the energy in sunlight.  To measure the solar irradiance, a flat black piece of aluminum is placed in full sunlight.  The piece of aluminum is oriented so that rays of sunlight strike it perpendicularly (the dowel will cast little or no shadow when that is true).  The temperature of the block is measured (with a thermometer stuck into a hole drilled in the side of the aluminum block) as the block warms up (and it will get pretty hot).

Answering the following questions shows how you can use these measurements to determine the solar irradiance (the questions are listed on p. 72a in the photocopied class notes).

1.  Units of solar irradiance, S:

basically how many calories of energy pass through a square centimeter per minute

2.    How much energy will a collector of area A collect in time delta t?

Doesn't it make sense that the larger the collector you have and the longer you leave it out in the sun the more energy you will collect?

3.   What temperature change, delta T, will delta E cause?

This is our "old friend" from early in Chapter 2:

4.   Replace delta E in (3) with the the equation in (2)

5.   Solve this equation for solar irradiance, S.