Solar Irradiance Experiment

First, solar irradiance is really just a measure of the energy in sunlight.

Answering the following questions shows how you can use a few simple measurements to determine the solar irradiance (the questions are listed on p. 63 in the photocopied class notes).

1.  What are the units of solar irradiance, S:

basically how many calories of energy strike a 1 cm by 1 cm square area every minute.

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

An aluminum plate with large area will collect more energy than a plate with small area.  The longer you leave the plate in the sun the more energy it will collect.

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

This is an equation that we covered early in Chapter 2 (we were more worried about energy being absorbed by water and soil):

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

5.   Solve this equation for solar irradiance, S.

There is the equation you need.  If you know the mass of the aluminum plate, its crossectional area, the specific heat of aluminum, and measure how quickly the block warms with time, you can calculate the solar irradiance.