Lay the solar panel on a vertical surface.

Measure the voltage from the solar panel once each hour by plugging a Mindstorms NXT brick into an outlet.  Use the following program to measure and record the data.

At the end of the day, download the data using Investigator mode in Robolab.

Have the students write out a description of the experiment, show the graph of the results, and explain their results in the journal section of Robolab.

Perform these measurements on a sunny day, cloudy day, and at night.