Solar panels are getting cheaper, are new cell designs affecting longevity?

Solar cell technology has been constantly updated over the years, with conversion efficiencies increasing year on year, yet costs are also falling rapidly - will this affect the durability of solar panels? Based on five years of testing by a laboratory owned by the US Department of Energy, speculation estimates that new solar panels will still produce 80% of their initial power after 30 years of use.

The US Department of Energy's Sandia National Laboratories (SNL) embarked on a five-year study of the degradation of solar modules, purchasing 23 different solar systems from seven manufacturers in three climates and finally studying the performance of a total of 834 solar panels that had been installed.

Solar cell types have changed dramatically in recent years, with traditional aluminium-backed surface field (Al-BSF) designs dominating the market in 2018 with a 90% share, and gradually market attention shifting to cell designs such as PERL, PERT, SHJ or TOPCon after 2020, the report notes the lack of long-term field data on these new solar cell and module technologies.

Team leader Marios Theristis also points out that the solar market is changing rapidly and that without long-term field data on new technologies, it is impossible to answer questions about the durability of solar panels, so the team bought and analysed commercially available solar panels directly. The team therefore purchased and analysed commercially available solar panels directly and finally made the information publicly available on an anonymous basis. The team also worked with the National Renewable Energy Laboratory (NREL) and the University of Central Florida (UCF) to install the same systems in different climatic conditions.

The team conducted experiments in New Mexico, Colorado and Florida, testing the performance and initial power stability of the solar panels under standard conditions at the beginning of the experiment and periodically over the next five years to monitor degradation.

They found that the degradation rate over time was highly non-linear, and that the solar module type, although seasonally variable, was similar to past modules, with an average degradation rate of around -0.6% per year, and that out of a total of 23 different solar systems studied, six had degradation rates above the warranty limit and 13 showed the potential to exceed a 30-year lifetime (if degradation levels were stable). The potential to exceed 30 years (if degradation is stable) is shown by 13 solar systems.

As the number of solar panel installations increases, consumers and stakeholders will be interested to know if the durability of solar panels is consistent in the face of changes in solar cell technology and rapidly decreasing costs, Theristis believes the results are good, but also points out that 26% of solar systems are likely to exceed the warranty limit, and that the degradation rate needs to be reduced to the point where the life of the panels can be extended.

Overall, the solar degradation rate does not appear to have been affected, despite the rapid decline in costs over the past decade.