One solar cell will not be able to provide required output power, because its small device, with a tiny output power of approx. 0.2 watts up to 2 watts, so in order to increase the solar photovoltaic system output power, there will be a need to connect/combine number of solar cells together, and that is the solar module in which we connect a number of solar cell in series, so can get a standard output voltage and power from it.
Solar products are more and more widely used in our lives. The solar module is the basic block of building our solar photovoltaic system, we connect the solar cell together same like batteries bank system, we mean in series, and for more clarification, we connect the positive terminal of one solar cell to the negative terminal of the second solar cell, and so on, in that way the voltage and power of all solar cells will add to each other, and at the end, we got the module with a standard output voltage and power. For example, the solar cell output voltage is approx. 0.5V, so if we connect 300 solar cell in series, the module standard output voltage would be 0.5 x 300 = 150Volt.
The solar module output depends on 2 parameters which are the ambient temperature, and solar light intensity, so the solar module ratings should be specified under certain value of those 2 parameters. Its agreed as a standard practice to express solar module ratings at 1000W/M2 light radiation, and 25-degree celsius ambient temperature, and always the solar module is rated with 3 outputs as following:
- Open Circuit Voltage (Voc).
- Short Circuit Current (Isc).
- Peak Power (Pmax).
And that means those 3 rated values will be provided for any module by its manufacturer at 1000W/M2 light radiation, and 25-degree celsius ambient temperature, that is called standard test conditions measurements. Logically, the standard test conditions may not be achieved on your site in where the module is installed because the temperature and solar radiation will vary from time to time and from location to other.
One of important factors distinguished the module is the efficiency, it refers to the ratio between module output power to its input power at standard test conditions, and we have to know that solar module loses a certain ratio of its efficiency every year, the lose percentage is small approx. 0.6% per year, so it's around 16.4% max of its rated efficiency over the 25year (solar module life time).
