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?

When a solar panel is shaded, the shaded cells do not produce as much power as the cells that are exposed to sunlight. In fact, the shaded cells can actually act as a load on the rest of the cells in the panel. This is because the shaded cells have a lower voltage than the other cells, which causes current to flow through them in the opposite direction.

As this current flows through the shaded cells, it heats them up, and the heat generated can cause damage to the cells.

This is especially true if the reverse voltage across the shaded cells exceeds their breakdown voltage. If this happens, the cells can experience thermal stress and can develop hotspots, which are areas of the cell that get significantly hotter than the rest of the cell.

Hotspots can cause damage to the cell and can also reduce the output power of the entire panel. This is because the hotspots can heat up adjacent cells, which can then also develop hotspots.

The overall effect is a decrease in the output power of the panel, which can be a significant problem for solar installations.

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 the heating of adjacent cells and cause a significant decrease in the output power.

Example Case Calculation for A Hotspot

Let's take an example to illustrate how hot spots occur on solar panels with some mathematical calculations:

Let's assume a solar panel has 60 photovoltaic cells connected in series. Each cell has a rated output of 0.5 volts and 1.5 amperes.

So, the total voltage of the solar panel would be:
60 cells x 0.5 volts/cell = 30 volts

And the total current of the solar panel would be:
60 cells x 1.5 amperes/cell = 90 amperes

Now, let's assume that a shadow covers 10 cells of the solar panel, which reduces the output of those cells to 0 volts and 0 amperes.

This means that the remaining cells have to compensate for the power loss of the shaded cells. So, the remaining cells will have to produce the same amount of power that was being produced by all 60 cells before the shadow.

The output power of a single cell is calculated as follows:
Output Power = Voltage x Current

So, the output power of each cell would be:
0.5 volts x 1.5 amperes = 0.75 watts

And the total output power of the 60 cells before the shadow would be:
60 cells x 0.75 watts/cell = 45 watts

Now, after the shadow, the remaining 50 cells will have to produce the same amount of power, which means that each cell will have to produce:
45 watts / 50 cells = 0.9 watts/cell

However, the shaded cells are still connected in series with the functioning cells, and they draw current from the functioning cells.

This causes the functioning cells to produce more current than they were designed to produce, leading to power dissipation and heat generation.

Let's assume that the shaded cells draw 0.5 amperes from the functioning cells. This means that the current produced by each functioning cell would increase to:
1.5 amperes + (0.5 amperes / 50 cells) = 1.6 amperes/cell

Now, the power dissipated in the shaded cells can be calculated as follows:
Power Dissipation in Shaded Cells = Voltage x Current
= 0 volts x 0.5 amperes
= 0 watts

However, this power has to go somewhere, and it ends up heating the shaded cells and the surrounding cells.

This heat can cause the shaded cells to reach a temperature higher than the functioning cells, which can cause thermal stress and eventually lead to hotspots.

So, in summary, a shadow on a solar panel can cause hotspots by creating power dissipation in the shaded cells, which leads to heating and thermal stress.

Are hotspots on solar panels visible to 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?

Mismatched Electrical Properties

Mismatched electrical properties are one of the leading causes of hotspots on solar panels.

It occurs when the electrical properties of the individual components of a solar panel are not well-matched. This can cause an imbalance in the electrical current, which can result in some areas of the panel getting hotter than others.

To prevent mismatched electrical properties, it's important to ensure that all panel components are well-matched during manufacturing.

This includes solar cells, wiring, and connectors. Manufacturers should implement strict quality control measures to ensure that all components meet the necessary specifications.

Regular inspections and testing of the electrical properties of panels can also help to identify and address any issues.

This includes testing the voltage, current, and resistance of each panel to ensure that they are functioning correctly. By identifying any issues early, it is possible to prevent any hotspots from developing and ensure that the panels are functioning at their best.

In addition to manufacturing and testing, regular maintenance is also crucial to ensure that the electrical properties of the panels remain well-matched.

This includes regular inspections of the wiring and connectors to ensure that there are no loose connections or damage.

Any faulty connections should be repaired or replaced promptly to prevent any issues from developing.

Overall, preventing mismatched electrical properties is essential to ensure that solar panels operate at their optimal efficiency and do not develop hotspots.

By taking the necessary steps during manufacturing, testing, and maintenance, it is possible to ensure that all panel components are well-matched and functioning correctly.

Manufacturing Defects

Manufacturing defects are another major cause of hotspots on solar panels. These defects can occur during the production process and can cause issues with the electrical components of the panel.

Examples of manufacturing defects include faulty wiring, damaged solar cells, and loose connections.

To prevent manufacturing defects, it's crucial to implement strict quality control measures during production.

This includes inspecting each component of the panel to ensure that it meets the necessary specifications. Manufacturers should also conduct thorough testing of each panel to ensure that it is functioning correctly and does not have any defects.

If a defect is identified, it's important to address it promptly. Any faulty panels should be replaced or repaired to ensure that they are functioning at their best. This can involve replacing damaged solar cells, repairing faulty wiring, or replacing connectors that are not functioning correctly.

Regular maintenance and inspections of the panels can also help to identify any manufacturing defects that may develop over time.

This includes inspecting the wiring and connections for any signs of wear or damage, as well as testing the electrical properties of the panel to ensure that it is functioning correctly.

In addition to preventing hotspots, addressing manufacturing defects can also help to ensure that the solar panels last for as long as possible. By identifying and addressing any defects early, it is possible to prevent further damage and extend the lifespan of the panels.

Shading

Shading is a complex issue that can significantly impact the efficiency of a solar panel system.

When a panel is shaded, it can cause a reduction in the overall output of the panel, which can lead to the development of hotspots.

This is because, in a photovoltaic (PV) solar panel, the cells are connected in series to form a string. If one cell is shaded, it can cause a drop in voltage that affects the entire string, leading to a reduction in overall output.

To minimize shading, optimal panel placement is critical. This means that the panels should be placed in an area that receives maximum sunlight throughout the day.

The optimal placement of the solar panel varies based on the latitude of the location, the orientation of the panel, the season, and the time of day.

The optimal angle for the panel varies throughout the year, based on the position of the sun.

For example, the optimal angle for a panel in the summer is different than the optimal angle in the winter.

In addition to optimal panel placement, it's important to regularly trim overgrown vegetation around the installation area.

Trees and bushes can grow quickly and cast shadows on the panels, so it's important to keep them trimmed back to ensure that they do not block any sunlight.

This can be especially important during the summer months when the sun is at a higher angle in the sky.

Another solution to shading is the use of microinverters or power optimizers. These devices are designed to limit the impact of shading on the panels by allowing each panel to operate independently of the others.

This means that if one panel is shaded, it will not affect the performance of the other panels.

For example, if a tree casts a shadow on one panel, the microinverter or power optimizer can adjust the output of that panel to ensure that it operates at its optimal level.

In addition to these measures, it's also important to consider the use of solar tracking systems.

These systems are designed to track the movement of the sun throughout the day and adjust the positioning of the panels accordingly. This can be especially useful in areas where shading is a persistent issue.

There are two types of solar tracking systems: single-axis and dual-axis. Single-axis trackers move the panels from east to west, while dual-axis trackers move the panels from east to west and up and down to optimize their angle to the sun.

Overall, preventing shading is essential to ensure that solar panels operate at their optimal efficiency and do not develop hotspots.

By taking the necessary measures to ensure optimal panel placement, trimming overgrown vegetation, utilizing microinverters or power optimizers, and considering the use of solar tracking systems, it is possible to minimize the impact of shading on the panels and maximize their performance.

Dirt and Debris

Dirt and debris accumulation is other common issue that can impact the efficiency of solar panels.

When dirt, dust, and debris accumulate on the surface of the panels, it can block sunlight and reduce the amount of energy that can be produced.

This reduction in energy production can lead to the development of hotspots and reduce the overall efficiency of the solar panel system.

To prevent dirt and debris accumulation, it's essential to regularly clean the panels.

This can involve using a soft brush or cloth to gently clean the surface of the panels and remove any dirt, dust, or debris.

It's important to avoid using harsh chemicals or abrasive materials that can scratch or damage the surface of the panels.

In addition to cleaning, it's also important to consider installing bird deterrents to prevent birds from leaving droppings on the panels.

Bird droppings can be especially problematic as they can contain acids that can damage the surface of the panels and reduce their efficiency.

Installing bird netting or spikes around the installation area can help to prevent birds from roosting on or near the panels.

Cracks or Damage to Solar Cells

Cracks or damage to solar cells is another common issue that can cause hotspots on solar panels.

Cracks or damage can occur due to a number of reasons, such as weather events, impacts, or poor handling during transportation or installation.

When a solar cell is damaged, it can cause a reduction in the overall output of the panel, which can lead to the development of hotspots.

To prevent cracks or damage to solar cells, it's important to regularly inspect the panels for any signs of wear or damage.

This can involve visually inspecting the panels for any cracks, chips, or other signs of damage. It's important to inspect all components of the panel, including the solar cells, wiring, and connectors.

If any damage is identified, it's crucial to address it promptly. Any damaged solar cells or panels should be repaired or replaced as soon as possible to prevent further damage.

This can involve replacing the damaged solar cell or panel with a new one. If the damage is minor, repairs may be possible, depending on the extent of the damage.

Regular maintenance and inspections can also help to prevent cracks or damage to solar cells.

Inefficient Cooling

Inefficient cooling is another factor that can lead to the development of hotspots on solar panels.

When solar panels get too hot, it can cause a reduction in their efficiency, which can lead to the development of hotspots.

Proper cooling is essential to ensure that solar panels operate at their optimal temperature and do not develop hotspots.

To prevent inefficient cooling, it's important to ensure that there is proper airflow around the solar panels.

This can involve installing the panels in an area that is free from any obstructions that may block airflow. It's also important to ensure that the panels are installed at the optimal angle to maximize airflow.

If necessary, active cooling systems can also be installed to improve the cooling of solar panels. This can involve installing fans or water-based cooling systems to help dissipate heat from the panels.

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 solar panels can indeed help prevent the development of hotspots.

Bypass diodes are designed to allow current to flow around any solar cells that are shaded or damaged, which can prevent the development of hotspots.

In a solar panel system, solar cells are typically connected in series to form a string.

If one cell is shaded or damaged, it can cause a drop in voltage that affects the entire string, leading to a reduction in overall output.

Bypass diodes can be used to prevent this by allowing current to flow around any shaded or damaged cells, which can maintain power output and prevent hotspots from developing.

Bypass diodes are typically installed on each individual solar panel, and there may be multiple bypass diodes on larger panels.

They are designed to activate automatically when there is a drop in voltage due to shading or damage, and they allow the current to flow through an alternate path around the affected cells.

In addition to preventing hotspots, bypass diodes can also help to extend the lifespan of solar panels.

By allowing current to flow around any shaded or damaged cells, they can prevent those cells from overheating and potentially causing further damage to the panel.

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.