When considering a solar panel installation, engineers take into account a metric called the fill factor, or FF. This is one way of gauging the efficiency of a solar panel without measuring the irradiance from the sun at the location of the solar panel.
In this experiment, you will vary the load in the solar panel circuit to determine the fill factor. You will create a current-potential curve, also known as an IV curve. The letter I is the standard symbol used to represent current in equations.
IV curves show the maximum current, maximum voltage, and maximum power a solar cell can generate. The rectangle formed by the graph axes and a vertical line from the open circuit voltage (VOC) and a horizontal line extending from the short circuit current (ISC) extends over a large area of the graph. A smaller rectangle is defined by the graph axes and the current and voltage at maximum power output (IMP and VMP). The fill factor is the area of the smaller rectangle divided by the area of the large rectangle:
The open circuit voltage VOC is the voltage when the resistance is infinite (i.e., when there is no load connected to the system) and the circuit is open, therefore no current can flow. The short circuit current ISC is the current when the resistance is approximately 0 Ω and the voltage is 0 V. This case is measured by closing the circuit with a plain wire instead of a load.
- Use an Energy Sensor to determine current, potential (voltage), and power.
- Create an IV curve for a solar panel.