Overheating & fire damage – the invisible danger for PV systems

It sounds paradoxical: it is precisely where solar energy is collected that heat can become a weak point.

We are talking about so-called hotspots – areas within a PV module in which individual cells become very hot.

What begins inconspicuously can have a massive impact on the performance of entire systems.

Hotspots are among the most common and most dangerous faults in photovoltaic systems.

But how do they develop and how can they be recognised at an early stage?

🔍 How do hotspots develop?

A hotspot occurs when one or more solar cells restrict the current flow within a PV module and instead act as a resistor or load.

As a result, the affected area can become very hot – with temperatures of over 100 °C.

This overheating can not only lead to a loss of performance, but can also cause serious damage and, in the worst case, pose a fire danger.

What are the consequences of hotspots?

🔥 Yield losses – The energy yield of the entire module or string may decrease.

⚠️ Material damage – The high temperatures can damage the module.

🚨 Fire risk – Continued overheating increases the risk of fire.

Typical causes of hotspots

• Shading – Local, partial shading by leaves, dirt, bird droppings or objects can cause this error pattern.
• Solar cell defects – Mechanical loads or material defects can damage the solar cells installed in the module to such an extent that a hotspot occurs.
• Missing or open bypass diodes – Without functioning bypass diodes, the current cannot bypass faulty or shaded cells. Without the protective function of the bypass diodes, a hotspot is created.
• Material fatigue or production errors – Ageing processes or poor manufacturing quality favour defects that can result in hotspots.

📷 How do you recognise hotspots using drone thermography?

Hotspots cannot be recognised with the naked eye – but thermography makes them visible at an early stage, even before critical problems arise.

✅ Increased temperatures – Hotspots appear on a PV module as significantly warmer areas. Depending on the temperature difference, hotspots can be categorised into different degrees of severity.

✅ Multi-hotspots – If there are several defective cells within a module, a pattern of several hotspots can form.