Full sun, half the yield - where is the energy lost?
Imagine: A sunny day, the display of your PV system shows a stable output – everything seems perfect. ☀
But when the bill arrives at the end of the month, you are in for a surprise:
The yields are significantly lower than expected.
No error, no warning – and yet valuable energy is lost day after day.
The reason? An idle string.
Silent, invisible, but with serious consequences for your yields.
Such errors often remain undetected for months, but can cause financial losses or even safety risks.
The solution? Drone thermography.
It makes invisible weak points visible – quickly, reliably and without long downtimes.
What is an “open-circuit string”?
A photovoltaic string consists of several solar modules connected in series, which together generate direct current.
A photovoltaic string consists of several solar modules connected in series, which together generate direct current.
If a string is idle, the circuit is interrupted – whether due to a faulty connection, a defective inverter or a damaged generator connection box.
The affected modules then no longer contribute to power generation.
Common causes of an idle string
- Damaged or loose plug connections – the current flow is interrupted.
- Defective string fuses – DC fuses that protect PV modules can fail.
- Short circuits or thermal overloads – components in junction boxes fail.
- Inverter faults – one or more strings may fail.
- Defective or deactivated generator junction boxes – faulty connections between strings & inverters can cause strings to run idle.
How do you recognise an idle string?
🔥Warmer temperature pattern – Non-working strings heat up more because less radiant energy is converted into electricity.
📷 Thermography as a solution – In thermography, they appear warmer than neighbouring, functioning strings. For clear temperature differences, an irradiation of > 600 W/m² is required.
Why is drone thermography ideal for fault diagnosis?
✅ Fast and large-scale inspection – Drones capture PV fields & roofs in just a few minutes.
✅ No plant failure – the inspection takes place during operation.
✅ Precise fault detection – empty strings are identified without time-consuming individual measurements.
Die Folgen eines Strings im Leerlauf
🚨 Performance loss – lower yields.
🔥 Security risks – defective cables or connections can lead to thermal problems or even electric arcs.