Shading of photovoltaic cells

 

The electrical output of photovoltaic cells is very sensitive to shading. Even when a small portion of the panel is shaded and the rest remains in sunlight the electrical output decreases drastically.

 

Shading from trees, poles, aerials, chimneys, existing or future buildings in the neighborhood all have a major impact on photovoltaic energy production.

 

A preliminary survey of the location and the arrangement of the PV array is important. A location with full sun light on the 21st of December (northern hemisphere) is probably the best place to install solar panels. You can find the minimum solar angle in the solar path diagram for you specific location.

 

The decreasing energy production due to shading has it?s electronic explanation in the series connection of solar panels. Due to a reduced flow of electrons or worst case electrons reversing course through the shaded portion of the p-n junction the power production of the whole PV array suffers.

 

The current (I) that flows in a series circuit - i.e. the number of electrons - will flow through every component in the circuit. Therefore, all of the components in a series connection carry the same current.

However, the total voltage (V) of the PV arrray is the sum of the voltages across all the components. Electric current (I) multiplied by the total Voltage (V) ios the total electric power (P) of the system.

 

To utilise partly shaded areas and minimize the impact onto the complete PV array, shaded photovoltaic modules need to be arranged in an independant array using a separate inverter.