By Lars Raakilde Jespersen

Back in 2004 AAU Energy installed 16 used solar panels on the roof of the high voltage lab building. It was part of a Green Power Lab programme, led by Professor Remus Teodorescu at that time. These BP Solar panels have been used for different research topics, one of them was focused on testing different maximum power point tracking algorithms. In later years the panels have served as a sustainable power supply, delivering around 1700kWh of green energy every year and their power production was monitored for validating performance models for PV systems, led by former colleagues, Associate Professor Dezső Séra and Associate Professor Sergiu Spătaru.

But then, Associate Professor Tamás Kerekes and his team, became curious and asked themselves, how effective those panels are 24 years after they were produced. Back then, the manufacturer, BP Solar, promised at least 80% efficiency after 20 years.

Tamas and colleagues compared with new, modern solar panels. They for sure from the beginning have a higher efficiency relative to size. Today you’ll get 20% of the available power, that is, one square meter of solar panel produces around 200 Watt if the Sun shines with 1000 Watt on a square meter. 24 years ago, it was 12%.

But do solar panels keep up performance?

During March, April and May, the AAU Energy researchers measured the energy created from five instalments of solar panels, having comparable orientation and tilt angle. They compared by calculating in energy produced relative to the performance (watt peak) for the panels. That is: kWh per kWp.

Result was that the old BP Solar panels in each of the three months produced more than average for the five instalments, delivering well beyond the 80% guaranteed datasheet values, even after 24 years under the Danish sunshine.