Solar energy has proven to be a reliable source of electricity for the world. However, many people do not understand its performance and how it works. Module performance is determined by use of a standard test. This includes irradiance of 1000W/m^2, a solar spectrum of about AM 1.5 and a module temperature of 25°C. On the other hand, electrical characteristics are determined using terms like nominal power, short circuit current, open circuit voltage, maximum power voltage, maximum power current, peak power and module efficiency.
Terms of electrical characterization
Nominal voltage is the voltage that can be termed as a classification voltage. This is the voltage that is carried over from the days when battery systems were the only things going. Technically, it means that if the module is charging a 12v battery, then the nominal voltage is 12v. The nominal voltage in turn serves as a guide to ensure that systems are compatible with a module.
Open circuit voltage is the maximum voltage that the module can produce when it is not connected to a load. This voltage can be measured with a voltmeter or a multimeter. This specific voltage is clearly stipulated on the specification sheet and sticker. The voltage is used as a testing value once the package with the solar module has been opened. It is also used to test the temperature calculation in a system design.
Peak power module is a term to describe the maximum output measured under a standard test condition. Most modules in the market fall between measurements of 1×2 meters and may have ratings of between 75 watts and 350 watts. It depends a lot on the efficiency of the module and how it has been designed.
It is vital for solar modules to be able to withstand rain, snow, hail and all types of weather conditions. That is why manufacturers of solar modules and the ones making crystalline silicon modules have a 10-year warranty for their solar modules which have 90% output rates. A good module should have the capacity of 80% output rate even if it is as old as 25 years old.
One form of degradation which solar modules has is potential induced degradation (PID). This is an induced performance degradation that is brought on by stray currents. It causes power yield and an output of up to 30%.
Photovoltaic modules are also affected mostly by the efficiency of the cell. This is because the amount of activation energy that has to be overcome by a photon do that it can excite an electron and thus the electric formation to take place. Scientists came up with a solution known as doping. This involves chemicals like boron being applied to semiconductors. Boron, being an impure element, reduces activation energy from 1.12eV to 0.05 eV.