When Solar Panels are put on a (Hot) Spot!

The average annual temperature, for the vast majority of our country is above 30 degrees Celsius.

Solar panels, also commonly referred to as solar modules, are installed in the open and operate at 15-20 degrees Celsius higher than the ambient temperature.

This means that the solar panels are operating at temperatures above 45 degrees Celsius regardless of the season. Though this temperature varies throughout the day, they are fairly equal through out the panel.

However certain factors can cause small, specific parts of the solar panels, to heat up to

temperatures that are much higher than the rest of the panel!

These localized areas giving out intense heat are referred to as 'Hot Spots'. They cause irreversible damage, degradation, and loss in output.

Actual field image of a hot spot

Actual field image of a hot spot

Hot spots are caused either due to Internal Factors or External Factors

Internal Factors include: Poor quality of solder bonds, use of substandard components, defective diodes, micro-cracks in cells, etc.

External Factors include: Shadows, soiling, bird droppings, sitting/ standing on the panel during installation, damage during transportation, etc.

To know more about the damage that shading causes click here.

How to safeguard against Hot Spots:

• Choose the right solar panel manufacturer

• Choose the right solar panel/ system installer

• Be Vigilant

Choose the right solar panel manufacturer

Solar panel manufacturers have to account for several factors to ensure the prevention of the formation of hot spots.

Every component should be of the highest quality and every process strictly adhered to.

Here are some key steps that are necessary to avoid the formation of hot spots while manufacturing a panel.

1. Ensuring that the required 'creepage' and 'clearance' distances are maintained according to applicable standards while designing and manufacturing the panels.

2. Using high-quality Encapsulant material that creates a cushion and protective covering on both sides of the PV cell to prevent the formation of micro-cracks because of external/ internal stress on the module.

3. Quality, automated soldering to prevent breakage of solder bonds. When the power produced by the PV cell cannot be transported due to faulty or broken solder bonds the energy is released as heat into the environment.

4. A robust Backsheet, comprising of quality raw materials and a high melting point (≥ 250 deg C) can help temporarily moderate the effect of the hot spot and maintain the insulation requirements for safety.

5. Consistent lamination of the panel is crucial to protecting the delicate solar cells. It prevents the formation of air bubbles, cell breakage and de-lamination of the solar panel after installation.

6. 100% EL imaging (electro-luminescence) before and after lamination. EL imaging allows the panel manufacturer to quickly check for defects in the cells, stringing, and presence of micro-cracks if any. (See how modules are manufactured here.)

7. Ensuring that the module manufacturer is using Electrostatic Devices for the Junction Box assembly to prevent damage to the diodes. Bypass diodes help reduce the damage of hot spots caused due to shade. However, if the bypass diode is itself defective, the hot spot temperature could go beyond 200 degrees C, resulting in permanent damage to the panel.

Choose the right solar panel/ system install

Ask your prospective installation partner about how they choose solar panels for a project, both the type of panel and the manufacturer.

Visit/ review reference projects.

Make the time to understand how a solar installer will help address your specific requirements before making a choice.

For example: Standalone homes have ample rooftop space, but the roof itself may not be easily accessible. Hence you will need to discuss both installation and maintenance that includes frequent cleaning of the panels with your installer.

A panel subjected to shading due to the growth of plants

Be Vigilant

Solar panels are built to last 25 years.

Keeping track of your solar systems' output and performance is an effective way to ensure a quick response to any changes that may be detrimental to your investment!

It could be something simple like trimming a few branches or something that requires a little help like cleaning your panels.

The only corrective action if one or more solar panels have a hot spot is to replace them before further damage is caused, both to the panel and to the entire system.

Hot spots reduce output and may be a serious safety issue, but with the right panel and installation partner, they are avoidable...

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.

Shading

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.