What are hotspots on solar panels and how are they caused?

What is a hotspot on my panel?

Hot spots on a solar panel are basically small areas or spots on a solar panel that is operating at a significantly higher temperature than the cells around it. Hot spots are essentially a spot on a solar panel of high temperature. That affects the solar cell by consuming energy rather than producing energy. This eventually results in the solar panel overloading, leading to a short circuit. Eventually reducing the overall output and efficiency of the panel. While also accelerating the panel’s degradation rate. Hotspots result from increased resistance or a restriction in the flow of electricity. The energy that is created has to be converted to heat as it cannot flow through the panel and create electricity for the home.

What causes hotspots?

There is a range of causes for hotspots in a solar panel which can either be caused by issues in the manufacture of a poor quality solar panel. Or operational circumstances in the installation or life of the panel. Manufacturing issues that can cause hot spots in solar panels are.

Manufacturing Issues

  • Cell mismatch – Where solar cells are not sorted and matched to ensure similar current characteristics. The difference in current between cells can cause resistance as they are
    connected in series. Leading to the generation of heat and hotspots.
  • Poor quality soldering and connections – If there is uneven soldering of the conductor ribbons/fingers and connection on and between cells. The imperfect/uneven point in the
    conductor or connection will again create resistance and develop into a hotspot.
  • Damaged cells – Solar cells are fragile if the handling is imperfect in manufacturing. This can lead to cracking and damage to cells which may not be visible to the naked eye. Once they are installed and working, these cracks will be exacerbated by electricity generation. Creating create resistance and hot spots.
Solar Panels in Tip
Efforts to mitigate hotspots through quality assurance in manufacturing can help reduce the number of lost panels

Situational Factors

Hot spots can also be created by situational factors in the operation of the solar panels once installed, as detailed below:

  • Shadows on solar panels – If there is regular/systematic shading of solar panels, whether this is caused by other solar panels, roof gables, ridges or other fixtures on the roof, aerials, trees etc. The shade cast across the panel restricts the current flow, which will again dissipate as heat. If this is recreated on a regular/daily basis due to the shading. This will lead to the degradation of the solar cell at that point in the solar cell/panel. Reducing the panel performance, leading to eventual burnout and failure of the panel.
  • Dirt, sand and bird droppings – Over time, solar panels can get dirty due to dust and sand in the air settling on the panels. Mainly where the panels are installed almost flat, there is reduced opportunity for the sand and dirt to be washed off. This can then accumulate at the corners and bottom of the solar panels and effectively shade the solar cells. Therefore creating resistance and risk of hotspots. Bird poo is also an issue, as the bird poo is concentrated and can stick to a concentrated point on the panel. This will create a resistance point that, if left over time, can create a hotspot that permanently damages the solar panel.

How can I avoid hotspots?

To minimise the risk of hot spots, there are a number of things to consider;

  • The first is to make sure that you use quality panels. Stick to the well-known, large manufacturer premium brands. This ensures the panels’ quality control and processes are in place. Ensure they are packed, transported, and stored correctly.
  • Choose a quality installer that takes good care of the panels. Solar panels should be handled carefully to minimise the risk of cell damage. Nor pressure should be put on the cells from the back of the panels as this can easily lead to cracks. Similarly, no weight or force should be placed on the front of the panel. Panels cannot be walked on and no pressure should be applied to the glass including supporting installers’ weight while tightening clamps or sitting on panels (I have seen this done!)
  • Ensure that shading is minimised or eliminated on the panels, regularly check for growing trees etc that may create shade on the panels and prune/ maintain them to prevent shading.
  • The final way you can avoid hotspots is through bypass diodes. A lack of bypass diodes often causes hotspots. Hotspots can often be caused by a lack of bypass diodes which means there is a lack of current flow in case of shading or a defect.
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