User:Amanda WellsRCBC/sandbox

Assignment 7 (Draft for article contribution)
The current-voltage characteristic (I-V characteristic) as defined by James Dunlop is "the basic electrical output profile of a PV device." The I-V characteristic acts as a representation of all operating points for a module of an entire PV system. The current-voltage curve (I-V curve) is a graph that shows how the current and voltage affect module output. It shows current (I) in relation to voltage (V) and how when I decreases and V increases, the power output of the module changes proportionately. The variables and parameters used in the I-V curve graph are the open-circuit voltage ( Voc ), short-circuit current ( Isc ), maximum power current (Imp), and maximum power (Pmp). The "knee" of the I-V curve is where the maximum power point, or where the current and voltage relationship begins to turn downward on the graph, of the module is found. The maximum power point can also be calculated using the formula Pmp = (Vmp)(Imp). However, the I-V curve is not only used to find the maximum power point. Any point on the line of an I-V curve is an acceptable operating condition for a module or PV device. These graphs can also give a visual representation of all the important variables that affects a module's performance. The main line of the graph is typically constructed using the variables open-circuit voltage and short-circuit current. The open-circuit voltage is found when measured with a multimeter set to measure DC voltage. The same can be done for the short-circuit current, except the multimeter must be set to measure current. Both the I-V characteristic and I-V curve are created using specified conditions, typically those of standard testing. By utilizing the basic form of an I-V curve graph, other graphs can be generated in order to visually represent the relationships between variables such as the short circuit current and the open circuit voltage, as shown in an I-V curve in relation to power. Another graph that visually represents the variables that affects the quality of module performance is the fill factor graph. The fill factor (FF), as defined by James Dunlop, is "the ratio of maximum power to the product of the open-circuit voltage and short-circuit current" and it represents the performance quality of the module It is typically expressed as a percentage and uses the formula: FF = Pmp/(Voc)(Isc). For example, a module with a Pmp of 3 Watts, an Isc of 7 Amps, and a Voc of 0.6 Volts, the calculated fill factor would be 71.4%. The typical PV module (crystalline silicon) will have a high fill factor and will exceed the percentage given in the example. Comparatively, thin-film PV materials have a fill factor percentage that is slightly less than that of traditional modules. The fill factor and its related graph can be used in order to determine if the efficiency of a PV system or module has changed over time or has gone through module degradation. The graph of a fill factor also takes the shape of an I-V curve. This allows for comparison between the two graphs.

Assignment 8
Amanda Wells peer-reviewed Andrew ferdetta's article.