How much does solar panel productivity decrease in the long run? Research

A research team from the US Department of Energy's National Renewable Energy Laboratory (NREL) conducted a comprehensive review of the degradation of commercial and utility-scale photovoltaic (PV) sites across the United States from 2008 to 2022.

Their extensive dataset, considered the largest of its kind for such a project, included information from 25,000 inverters across nearly 2,500 commercial and utility-scale PV sites in 37 states and US territories, amounting to almost 8 gigawatts of solar capacity. The average age of the observed PV systems was five years.

The researchers identified a median loss in performance rate of 0.75% per year, aligning with similar values reported in previous studies. Their analysis revealed that systems in hotter temperature zones experienced twice as much performance loss compared to those in cooler climates, with rates of 0.88% per year and 0.48% per year, respectively. Overall, 90% of the studied systems showed performance losses of less than 2% per year.

Chris Deline, a group manager for PV field performance at NREL, emphasized the significance of the median loss in performance, stating that it indicates the PV systems, on the whole, are not failing catastrophically but degrading at a modest rate within expectations. He highlighted the importance of accurately quantifying this rate, as it is a crucial factor in financing agreements that fund solar projects and provides essential guidance for the industry.

The researchers found that the short-term impact of extreme weather, including flooding, high winds, hail, wildfires, and lightning, was generally minimal for most PV systems studied. The median outage duration after extreme weather events was two to four days, resulting in a 1% median loss in annual performance.

However, the study identified that when extreme weather events are powerful enough, they can accelerate long-term degradation. Hail larger than 25 mm in diameter, winds exceeding 90 km/h, and snow depths exceeding 1 meter were associated with greater annual performance losses in PV systems, such as mechanical stresses causing solar cell cracking.

NREL researcher Dirk Jordan stated that the analysis does not suggest that PV systems are unreliable or especially vulnerable to extreme weather. PV has demonstrated its capability to provide backup power and save lives when surrounding infrastructure is damaged by extreme weather events. Nevertheless, the researchers recommended further measures to improve equipment quality and installation best practices to enhance resilience to these weather events.

They suggested that module manufacturers and PV testing organizations understand the thresholds at which damage can occur. By doing so, the industry can design for these conditions and develop tests that subject panels to realistic stresses from wind, snow, and hail. Additionally, the researchers emphasized the importance of high-quality installations, proposing standardized practices such as using through-bolting and mounting modules at a sufficient distance from the edge of roofs in wind-prone areas to mitigate system performance impacts.

Earlier it became known that the glass of the solar power plants is widely cracking and the reason is still unknown.