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Hotspot Effect on Solar Panels: Causes and Solutions

Solar PV systems need sunlight to produce energy. The panels are made of semiconductor material that produces power when photons strike the surface and activate electrons.

If a cell or group of cells on a solar panel cannot receive light, they cannot produce energy. However, the drop in energy production of the panel will not be proportionate to the number of cells that aren’t working.

Because solar cells are connected in series, a weak cell or group of cells will affect the energy production of all the cells on the same string. To prevent this, manufacturers will use bypass diodes that allow current to flow around weak cells.

However, not all solar panels are built equal. The same solar panel with four bypass diodes in four strings will perform better than the one with two bypass diodes and two strings under the different shading conditions.

What that means the more bypass diodes a solar array has, the fewer shading-related problems it will have.

But shading doesn’t only cause a drop in energy production. There is one more problem that can create significant safety problems and financial loss. It is the hotspot effect that we will be looking at in this post.

What is the hotspot effect?

The hotspot effect occurs when a solar panel is shaded and the current cannot flow around weak cells. Eventually, the current will concentrate in a few cells, causing them to overheat and potentially melt.

The hotspot effect is one of the most common causes of solar-panel failure or fire hazard. Therefore, when designing photovoltaic systems, it is critical to use bypass diodes to ensure that current can flow around weak cells while shading effects are minimized under various shading conditions.

Hotspots are still quite common in today’s PV modules, and this scenario is anticipated to endure as PV module technology evolves to thinner wafers, which are prone to forming micro-cracks during the processes of manufacturing, transportation, and installation.

How do hot spots occur on solar panels?

When a shade is cast on a solar panel, the current is not distributed evenly across all of the photovoltaic cells. The weak cells under the shadow will draw current from the functioning cells.

This power dissipation manifests itself as heat. If the reverse bias surpasses the cell’s breakdown voltage, the cell suffers from increased temperature and impacts surrounding cells.

This condition leads to thermal stress and eventually to hotspots. These hot spots cause heating of adjacent cells and cause a significant decrease in the output power.

Are hotspots on solar panels visible by the naked eye?

Hotspots are not visible to the naked eye unless if you can see an obvious color difference like a brown spot on the solar panel. However, even if you can’t see the hotspot, it doesn’t mean that it’s not there.

Therefore, the performance of the solar PV systems should be monitored always to determine the amount of power that is being generated by each module.

You cannot detect most hotspot problems efficiently without a specialized measurement technique. The most efficient way to detect hotspots is using thermography.

Using this technique, thermographic images of solar panels can be taken to see if there are any hotspots that need to be addressed.

A thermographic image is a picture or video that shows the temperature distribution of objects. In solar panel inspection, thermography spots hotspots on the surface of solar panels with a very high accuracy rate.

What are the sources that can create hotspots?

Hot spots on the surface of solar modules are very common and account for a significant portion of the module’s power consumption.

We know at this point that hotspots are caused by cast shadows. So what are the sources of cast shadows?

One source is shading by an object near or above a solar panel, such as trees, people, or equipment. Another common cause is a blockage due to dirt and debris on the glass surface that prevents light from getting into the cell through reflection.

Hot spots can also be caused by design defects of certain types of silicon cells known as multi-crystalline or poly-crystalline cells.

If the hot spots are not detected in a timely manner, they can have a significant impact on neighboring cells as well as affect/damage solar power generation.

How to prevent hotspot problems on solar panels?

It is not much you can do to fix existing hotspots on solar panels. Because of the nature of these defects, non-functioning cells are overheated and degraded to the point of damaging the entire solar panel.

However, there are several measures that can be taken to prevent and avoid hotspots and their negative effect on solar panels.

Good design matters

A good solar panel design will always take hotspot problems into consideration. Bad design can result in hotspots, especially if you have a large flat rooftop with few shading factors to work with.

People who install their own solar panel systems should always consult professionals so as not to make these mistakes by themselves.

Maintain good airflow

Hotspots do not appear out of anywhere. They are always the result of heat buildup, which can be a result of a number of factors. However, if you have low airflow in your solar panel system like a protective cover, then you have a higher chance of hotspots rising.

A good solar panel system will always ensure that there is adequate ventilation and airflow to avoid overheating the panels. The best way to prevent overheats is by installing a power optimizer that automatically reduces electricity output when temperatures rise too high.

This ensures your production levels are maintained without having to use any manual controls.

Use bypass diodes

Using bypass diodes on each solar panel can even prevent hotspots from being formed. Hotspot effects on solar panels are often caused by the lack of bypass diodes. Bypass diodes allow current flow in case of a defect or shading; thus, maintaining power output.

Glass & back sheet with good thermal properties

Manufacturers can also use types of glass with specific properties that can reduce the heat gain, rather than simply absorbing it. It is also a good practice to use a back sheet material with high thermal conductivity to allow the panel to dissipate heat more easily.

Remove dust & dirt

A dirty or dusty solar panel is likely to generate higher hotspot effects. Regularly cleaning the panels can help reduce this effect.

It is also a good idea to make sure that any trees, leaves, and other debris do not block sunlight from reaching your solar panels over time.

Use a solar tracking system

Solar tracking systems actually move solar panels to face the sun, instead of just letting them sit in one position.

These systems help reduce hotspot effects by always exposing your panel to direct sunlight throughout the day. The downside is that these tracking systems are expensive and will increase your electricity output costs due to the additional moving parts required for this system type.

Install panels at the right angle

Installing your panels at the right angle helps reducing hotspot effects. You can find the best angle to use for your location online.

Install panels without obstructions

A simple and effective way to reduce hotspot effects is by installing your panels without obstructions. This means that they should not be too close together or in the shade of anything else for this will likely cause shadows on each other.

Trees and buildings are the most common obstructions to be aware of. Installing your panels away from any shadows will be helpful as well.

Read Manufacturers’ instructions

Lastly, it is highly recommended to read the manufactures recommendations. The manufacturer typically knows what makes their product works the best without any problems, and will include information on how to get the best out of it.

Are there any hotspot-free panels on the market?

There are a few companies that have managed to create panels that are hotspot-free or at least hotspot-reduced.

However, there is a lot of controversy surrounding the notion of whether these products can be called 100% percent hotspot-free. In many cases, even with improved technology, it’s only possible to reduce hot-spotting by a certain percentage.