D-Lab: Energy

Lab 2 Instructions

Power Module

In this module, we’re aiming to characterize the peak power output of the solar cell. As you may recall from our earlier class, as you change a resistive load in a circuit, the voltage and current that are outputted also change. Since we know that the P = I²R = V²/R, it is possible to find the maximum power output of the solar panel experimentally by measuring current and voltage at a variety of resistances. The procedure for generating this curve is as follows:

1. Choose an orientation for the solar panel

   As you will find in the other modules, changing the angle of the solar panel and the amount of light that is contacting the panel will affect the power outputted by the panel. In order to not confound your power measurements with these variables, fix the orientation of the solar panel for this portion of the lab. Note: avoid placing the panel close to shadows, since they will move and potentially block some light from the panel.

2. Measure the power of the cell

   A potentiometer is a variable resistor, and we will provide you with a fairly robust one that is able to handle the power being outputted by the panel. The resistance of the potentiometer changes as you turn the dial, so you should turn the dial and measure the resistance.

   NOTE: You cannot measure the resistance of the pot while it is hooked up to the circuit, so you have to disconnect it from the circuit before measuring. If you do try to measure the resistance, you will burn out the voltmeter.

   For several different resistances (I would like to see you take at least 15 different data points) across the range of the resistor, measure the voltage across the load. You will need to graph power vs resistance later for the lab write-up.

Angle Optimization

In this module you will be measuring how the power output of the solar panel changes with angle. The power output of the solar panel is determined by the angle of the light hitting the solar cell. For a given load, change the angle of the panel and measure the voltage across the resistor and the angle. Take at least 10 different data points, recording the angle and voltage (make sure you also write down the resistance you are using to calculate power later). We want to see how the power output changes when we angle the solar panel both ways, parallel and perpendicular to the individual solar cells.

Shading Module

In this module, you will examine how the efficiency of the solar panel drops when the solar panel is covered. You will be covering the solar panel in two ways, placing a cover that is perpendicular to the individual cells and then placing a cover that is parallel to them. Measure the exposed surface area and take at least 10 different data points, recording the exposed surface area and output voltage (make sure you also write down the resistance you are using to calculate power later).

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