No shade for solar!
Summer is making its presence felt across the Indian subcontinent with hot, sweltering afternoons. Much like us, solar panels do not love this hot weather.
But there’s one key difference – while you and I can relax in the shade, solar modules also commonly referred to as solar panels, cannot! Here’s why...
In a standard solar panel, 72 cells are connected to each other in a series circuit, generally in three strings, with three bypass diodes.
As the name suggests, it has to do with the blocking from direct sunlight, of a part or of the whole, of the solar panel.
When an entire panel is under shadows or in the shade, it simply stops generating power.
If you look more carefully you will notice that shadows often cover portions of more than 1 cell.
Even if only one quarter, of the surface area of one cell, in a module, is under a shadow, the output will drop for 24 cells or one string in a 72 Cell module!
The presence of Bypass diodes in the structure of a solar panel, creates a separate way for the current from the strings with 'un-shaded' cells to pass, thus avoiding the passing of excess current through the part of the panel that is under shade. This is how it improves the solar panel's overall power generation output in the presence of shadows.
However, these diodes kick in only if the drop in the output is more than 50% like in the example above.
Shadows from objects in the vicinity like buildings, trees, and even the neighbouring panels can thus contribute to the loss of power generation output.
And these structures need not be located very close to your installation either, for them to cast a shadow...
The drop in output that the panel experiences even with a bypass diode could range from 1/5th of solar panels power to a maximum of 1/3rd of the power of the solar panels.
For E.g. for a 300 Wp the drop could range from 50 Wp to 100 Wp per panel.
In most cases, this gets more complicated as shadows cover uneven parts of several solar panels in an array.
The drop in power output is amplified further at the level of a solar array because one panel with a lower output causes the output of the entire array to drop.
Shading has another very significant drawback – it causes the formation of 'Hotspots'.
In the case of shadows, the cells free from shade are generating full power. The cells that are under shade cannot pass this entire power through, so this power is dissipated as heat causing small areas with high temperatures or 'hotspots' to be formed.
Simply put ‘Hotspots’ are zones at very high temperatures within a panel.
Hotspots in turn cause problems like the cracking of the solar cells in a panel, or the cracking of the glass, melting of soldering between cells, etc.
Hotspots could occur for a variety of reasons apart from shadows, which we will cover at length in our forthcoming posts.
So here’s how you can keep your solar system safe from the ‘shadows’…
1. Discuss with your installer the possibility of moving shadows through the day and identify an area with minimal or preferably NO shadows.
Seasonal shadows are just as harmful as constant ones.
We often observe shadows best in summer months, but observing changes in the angle and direction of light in winter is equally important.
2. Be vigilant about the growth of trees and other vegetation close to your roof that may cause new shadows to form. The same is true for new constructions around your home.
3. Keep tabs on the output pattern through the day that your system generates. If you find a reduction in output carry out a visual inspection or request your installer to visit and check your system.
4. While installing your system consider discussing a cleaning and maintenance contract with your installer or find out how you can service your panels frequently. This will ensure that the output of your system, and the panels themselves are routinely checked.