4.3.5 Operation of solar cells

The amount of power available from a PV device is determined by:

- the type and area of the material;
- the intensity of the sunlight (insolation); and
- the wavelength of the sunlight.

The amount of current produced is a function of the voltage. Figure 4.6 is a typical I-V curve for a crystal silicon cell under standard testing conditions in bright sunlight. This shows a typical maximum power of about 1.5W, but this is only obtained for the right combination of current and voltage, and therefore the cells must be combined into the modules and overall system in such a way that there is a good match with the load using the power. If there is a low voltage on the cell or the current being taken is too small, the power delivered will be low however bright the sunlight.

Source : www.aurora.crest.org
Figure 4.6 I-V curve for a typical crystal silicon cell

 

4.3.6 Rating

The performance of PV products is specified in terms of the maximum power (Watts Peak or Wp) which can be delivered under idealised standard solar conditions and loading. Prices and installation statistics are based on this concept.