Solar panels work best when there’s no shade cast upon them. In fact, a shadow falls on even simply a part of one solar panel in your solar array will probably compromise the output of the full system
Effect of shading on the solar power plant?
Solar PV systems comprise of a number of solar panels wired into arrays depending on the electric power demand from each of those panels, which in turn, composed of many solar PV cells that are the essential units involved in capturing energy from the sun and converting them into electricity. Now, if a shadow falls even only on one part of the solar panel in your array, the output from the complete system may be potentially compromised, this can be referred to as shading of PV panels.
Picture showing difference in output from shaded and unshaded solar panel
For better understanding,
Consider a string of panels as a piece of pipe, and the solar energy is like water flowing through that pipe. In conventional solar strings, a shade is something that blocks that flow. If, as an example, shade from a tree or a chimney falls on even one in all the panels within the string, the output of the whole string reduced to just about zero for as long as the shadow sits there. If there’s a separate, unshaded string, however, this string can still turn out power as per usual.
Graphical representation of effect of shading on solar system
What are the factors causes shading?
Shading, typically caused because of clouds, environmental obstructions such as trees or nearby buildings, self-shading between panels in parallel rows, dirt, dust and different other trash like bird droppings, etc. These shading effects are also static as a result of the position of the obstruction or in some cases dynamic, as an example, a shadow cast by moving clouds.
How does it affect the performance of solar power system?
Solar panels are connected into series-parallel combination depending on the inverter input voltage range. If shade from a tree or chimney is falling even on one panel of the string, the output of the whole string will nearly be zero for the period of the shade. This is because the panels are wired together in such a way that the output is reduced to a level of current passing through the weakest panel. If there’s a separate, unshaded string, it’ll still turn output power as usual. The impact of shade on the whole system depends on however the panels are wired together.
How to tackle shading problem?
Positioning of PV systems
Before installing a solar PV system you must do a careful analysis of the site considering all time of the day for all seasons of the year to avoid shade. A nearby growing tree or building that may come up in future also need to be considered before finalizing the location for PV System.
Now a day panel manufacturers are providing bypass diodes for the entire panels so that if one panel gets shaded it will not affect the performance of the entire array, but if we use bypass diodes for each cell of the solar panel, the power output from the solar panels isn’t dropped at zero simply because one single cell is shaded. Here the shaded cells are merely bypassed and not allowed to impact the output of the whole panel. The power output of the panel might reduce, however, it won’t be directly based on the power output of the lowest performing cell.
String inverter with MPP tracking capability
Maximum Power Point Tracking (MPP Tracking or MPPT) technology is now a standard among string inverter manufacturer. String inverters with MPP Tracker are able to squeeze the most usable energy possible out of a string of solar panels (even when shaded) by adjusting the input voltage. In a nutshell, an MPP Tracker helps to minimize output losses associated with partial shading and other output mismatches. Inverters without MPPT technology lose the output from the weaker string when it passes below the desired output threshold.
Micro Inverter and power optimizers
Both Microinverters and power optimizers are used to overcome the problem of partial shading. It allows every solar panel to work individually so that the system energy production is not disproportionately affected by just one or two shaded panels.