A new study from Belgium shows the importance of assessing inverter reliability by considering the degradation rate of PV panels as a function of climate. Scientists have found that, especially in hot and arid climates, the design parameters of photovoltaic inverters must be higher than standard values.
Scientists at the University of Hasselt in Belgium have discovered that the rate of solar module degradation caused by climate change could have a significant impact on the power electronics in photovoltaic systems.
In a recent study published in the journal Heliyon, “Assessing the Impact of Climate-Driven PV Panel Degradation Rates on Inverter Reliability in Grid-Connected Solar Systems,” the scientists warn against using the same climate-driven degradation rates across all PV systems. Degradation rates in different climate zones around the world represent an “unrealistic approximation” that can lead to misleading results. “This may lead to overestimation or underestimation of the service life of PV modules, thereby affecting the reliability assessment of power electronics devices,” they added.
The research team assessed the rate of degradation of the panel based on climate stresses at three different geographical locations: Genk in Belgium, Accra in Ghana and Kabud in Kuwait. These places represent mild, hot and humid, hot and dry climates respectively.
It uses a physical approach that takes into account meteorological data such as ambient temperature, radiation intensity, wind speed and direction, as well as material properties such as optical, thermal and electrical constants, as well as the thickness of each layer in the module. It also takes into account panel parameters such as temperature coefficient, external quantum efficiency, and interconnect placement.
The researchers explain that insulated gate bipolar transistors (IGBTs), the switching devices in photovoltaic inverters, are extremely sensitive to high temperatures and can lead to failure or shortened lifespan if not handled properly.
“Every time an IGBT is turned on, there is a power loss inside the material layer, and this power loss generates heat inside the IGBT,” they explain. “So every activation starts a thermal cycle due to these power losses.”
The team analyzed the potential degradation rate of a standard 4 kW PV system consisting of a DC-DC boost converter and a single-phase inverter using four IGBTs rated at 700 V and 40 A. Solar module degradation rate and scenarios that consider the degradation rate of PV systems.
Through a series of simulations, the researchers found that the lifespan of the inverters in the PV system located in Kabda was much shorter than that of the inverters located in Genk and Accra.
They highlighted: “Kabd PV inverters have experienced significant thermal stress without the effects of photovoltaic degradation, and IGBTs can fail in as little as 5 years, resulting in PV inverter failure in as little as 3.8 years.” With linear degradation of PV systems, the service life of Kabd PV inverters will increase to 5.8 years, which is still lower than the other two sites. A physics-based PV degradation model will extend the lifespan of Kabd PV inverters to approximately 6.5 years.”
The team concluded that deploying PV systems in hot, dry climates may require different inverter design parameters. “These results demonstrate the importance of considering various factors and parameters when assessing the reliability of photovoltaic inverters and their switching devices,” it said.
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Post time: Feb-07-2024