The power of drone-based fault detection

As the inventor of photoluminescence imaging, Professor Thorsten Trupke has spent his career making significant contributions within the field of global photovoltaic research and development. His innovative technology, which identifies hidden defects affecting the performance of solar cells in one second or less, has been embraced by leading solar cell manufacturers and research labs across the globe.

Daylight Photoluminescence image of a section of an Australian utility scale farm. The arrows highlight various device and system faults. Credit: School for Photovoltaic and Renewable Energy Engineering.

As our reliance on photovoltaics increases and solar becomes the dominant source of electricity over the next 30 years, it’s more important than ever to ensure that quality control of silicon wafers, solar cells and modules remains high. “In 15 years’ time, more than 80% of Australia’s electricity will come from solar and wind, and that’s what makes solar cells and solar modules such an important technology,” says Prof. Trupke.

“We’re at the beginning of a really fundamental transformation of the entire energy sector, and that is the motivation for our work.”

Solar is now the cheapest way of generating electricity in many parts of the world, including Australia, and has seen massive increases in use across residential rooftops, industrial rooftops and large utility-scale solar farms. When it comes to large utility scale solar farms, these panels are typically mounted on single-axis tracking systems, which improves the electricity output of each panel per day. While the cost for these modules continues to drop, manufacturers need to make them faster and with ever higher performance, which can lead to occasional faults. “The throughput in the factories has to go up and up, and at the same time, the efficiencies of the panels are also going up – this has associated risks,” explains Prof. Trupke. “Any product that you make millions or billions of times, in any industry, will likely experience occasional problems, so we have developed a quality testing technology which can be used for solar panels in the field.”

The new technology ensures small issues don’t become big problems, and that any faults can be captured early and then appropriately managed. “Our imaging technology generates pictures of solar cells or solar modules, which look into the material of the solar panels,” he adds. “From those pictures, we can see a whole range of potential material and device problems.”

While failure of modules is typically linked to natural degradation processes, these issues should normally occur at a very slow rate of typically <1% (relative) per year. Occasionally, however, this degradation happens significantly faster, which is problematic, not least from a financial perspective for the solar farm owners. “It’s not black and white – it’s not like a panel works today and then tomorrow it’s dead,” explains Prof. Trupke.

“Our technology enables quantifying module performance losses on a large scale and will have a large public impact as it will help solar become a much more reliable and therefore bankable source of electricity in the future.”

Back to the beginning

The technology was initially developed by Prof. Trupke at UNSW alongside UNSW colleague, Adjunct Associate Professor Robert Bardos in 2005. Together, they established the first demonstration of the technology by setting up small proof of concept systems in the optical laboratories in UNSW’s Electrical Engineering building.

“It was a remarkable time because there was a lot of fundamental research going on at the University into making solar cells better and improving their efficiencies. The first demonstration of photoluminescence imaging was like an eye opener for all the researchers,” explains Prof. Trupke.

“They didn't have any comparable techniques at the time, and all of a sudden they could come into our lab, bring a sample, put it into the black box and get this picture of their solar cell – telling them exactly what was wrong with it.”

A new way forward

Once word spread that this technology was available, Prof. Trupke and Prof. Bardos formed their company BT Imaging in 2007, for which they served as Chief Technology Officer and as VP Operations, respectively, for 15 years, and which still operates out of its Sydney headquarters to date and was later acquired by Canadian company, Aurora Solar Technologies. “As a small high tech company it has been successful. We developed photoluminescence imaging measurement systems – products that we would ship to China, to Europe, to America, in fact everywhere around the world.” This gave research labs and many factories throughout the world access to photoluminescence imaging tools. During this time, Prof. Trupke remained a part time academic at UNSW, continuously developing the fundamental side of the technology with his PhD and post-doc students.

A customised aerial drone during luminescence image acquisition in an Australian utility scale solar farm. Credit: School for Photovoltaic and Renewable Energy Engineering.

The daytime photoluminescence imaging team during field testing. From left to right: Dr Oliver Kunz, Juergen Weber, Alexander Slade, Thorsten Trupke and Ouyang Zi during field testing. Credit: School for Photovoltaic and Renewable Energy Engineering.

Developing a new image

The original technology has since developed significantly further, now allowing the technology to move from lab to solar farms for field inspection of modules in full daylight. “Measuring photoluminescence images in full sunlight is technically very challenging. If you had asked me even just10 years ago, I would have said this was absolutely not doable,” says Prof. Trupke. “In the beginning we had a specially designed laser lab where measurements were conducted inside a custom-made black box with all kinds of methods to avoid any ambient light getting in, and now we're saying – ‘let's do the exact opposite – let’s put the sample right into the sun’.”

This ongoing innovation now allows Prof. Trupke and his team to take images of panels already installed in operational solar systems.

“Our equipment involves flying large drones with very specialised cameras and optics that take aerial photos of the solar farms.”

- Professor Trupke

“We see remarkable things in these pictures and start learning more and more about what these patterns actually mean. It’s very fulfilling.”

Prof. Trupke and members of his team have recently started a new company, which will commercialise this innovative technology by offering drone-based photoluminescence measurements and associated data analytics as a commercial service. “We will come in and measure the quality of entire solar farms,” he adds. “It’s part of our plan to develop our technology into a suite of market ready commercial products and services.

As Thorsten and his team strive to contribute to solar energy becoming the most reliable and bankable energy solution in the world, Prof. Trupke is keen to attribute the growing success of solar to those working towards the same common goal. “Everyone in this entire industry is a little cog in a big machine, including us, and it is great to know that our work will have some impact.”

Hero image: Dr. Oliver Kunz during drone test flights in an Australian utility scale solar farm.
Credit: School for Photovoltaic and Renewable Energy Engineering.