R2: Reduce and Reuse
Keeping PV Panels out of Waste Streams
A real-world test of refurbished panels
Across Australia, growing volumes of solar panels are reaching the end of their first life. In most of the cases, these panels are either sent to landfill or shipped offshore. Panels sent overseas are not tested for safety or performance, raising concerns that we may be sending waste or even hazardous materials to developing countries.
The R2 Project tackles this challenge by focusing on two key strategies:
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Reduce – encouraging the procurement of higher-quality, longer-lasting panels from the outset.
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Reuse – giving older panels a second life through careful refurbishment and testing.
In order to assess the suitability of reused panels for continued use, we have developed an outdoor monitoring station to expose refurbished panels to real world conditions. This website provides regular, public-facing, performance reporting of the output of the refurbished panels.
Acknowledgements
With assistance from the ACT Government under the Renewable Energy Innovation Fund.
Based [in part] on data obtained through SPOTS, Solar PV Outdoor Testing System at Australian National University. We acknowledge the traditional owners of the land on which SPOTS operates, the Ngunnawal people, and pay our respects to elders past and present.
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Refurbished panels are packed and ready for delivery from PV Lab to the installation site at ANU
Construction of the array installation is underway on the roof of the ANU building
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Panels are installed and data gathering has commenced - see results below!
Baseline Panel Data
Panel Performance Data
The panels have been installed and generating since October 2025, and this analysis covers until end of July 2026.
The total energy produced by the panels in the project is shown below. Panel R2-006 has the highest energy, as expected given it also has the highest power rating. Similarly, R2-015 is the lowest energy as expected given its low test power.
To even out the different panel sizes, the figure below shows energy per watt of capacity. This changes the ranking from total energy: R2-015 is now the highest, even though it has a low test power. R2-021 has the lowest power per watt. The two identical panels in the test (R2-018 and R2-019) are very similar, however R2-019 has a slightly lower energy production per watt of panel capacity. Over time R2-018 has pulled slightly ahead of R2-019: in January panel R2-018 was 2.4% ahead of R2-019, now it is 3.1% ahead.
One of the main purposes of this project is to explore how the energy production varies with time. Declining energy production may indicate that panels are beginning to fail. The daily energy production of the panels per watt of test power is shown below.
As expected, the energy continues to decline due to the angle of the sun and reduced sun hours.
There were some outages that impacted the results, particularly around the end of November where all panels were not returning data for a period.
The average irradiance efficiency per month is shown in the picture below. Irradiance efficiency is a measure of how efficiently the panel converts sunlight into electricity and is calculated by the equation:
Missing data (days with efficiency less than 0.1) has been removed from the dataset.
A declining indicator could be evidence of panel degradation. Many panels showed a declining trend earlier in the dataset, but while some have begun to increase, some others have continued to decline.
One reason several panels may have shown lower performance around summer could be temperature. There are several papers that have shown temperature is a key contributor to output degradation[1]. December-February is the warmest period of the year so it may be expected that the test panels would have the lowest performance at this time.
However not all of the panels have behaved the same way. It may be expected that efficiency will also decline with time as the PV panel wears. Quickly declining output may be an indicator of a poor condition panel that is unsuitable for reuse.
The table below shows the average degradation per month for the test panels.​
To better understand the temperature and time effects, the efficiency decline per degree and per day is shown below. The per day degradation is far more variable than the per degree degradation. Panels R2-015, R2-016, and R2-021 appear to be degrading faster on a time basis, which may be the reason they do not see increasing efficiency now that the temperature is declining.
Exploring irradiance efficiency with time
For some panels, irradiance efficiency was the lowest in summer and has recovered since summer as temperatures have cooled. Some appear to have a stronger efficiency decline with time than temperature. To further understand this issue, the figures below shows the per day irradiance efficiency divided by month for each panel vs the mean of the minimum and maximum temperature for that day. Data is broken out per month and the red line in each plot shows how the monthly average has moved. Time-based degrading panels (R2-015, R2-016, R2-021) show a continually degrading performance per month. The temperature decline (i.e. the data points moving back toward the left of the X axis) in later months has not restored output closer to the performance in earlier months. However for temperature based degrading panels (R2-006, R2-018, and R2-019), April data is close to October data.
Intermittent outages of R2-018 and R2-019
Panels R2-018 and R2-019 have experienced intermittent outages. This is caused by a loose cable gland and internal connection. The internal connection issues have been improved by tightening the cable gland, but the connection still is intermittent. On a test system such as this where each panel is on an individual maximum power point tracker high open circuit voltage is less of an issue which reduces the risk of internal arcing caused by connection failure. It is likely these panels will remain intermittent as the connection issues are not fully resolved.
