A research group from the European Commission’s Joint Research Center has developed a new PV climate classification, the first to take into account the annual yield and performance ratio. Their work resulted in 10 globally applicable clusters. “It challenges the assumption that many more classes are needed to capture the PV-relevant climate,” the researchers said.
A group from the European Commission’s Joint Research Center (JRC) has proposed a new classification of climate zones for PV systems. Unlike previous frameworks, the approach takes into account annual energy yield and performance ratio, making it directly relevant for simulations, forecasts, energy assessments and policies for PV operations.
“This study presents the first PV climatic classification covering annual yield and performance ratio, relevant for applications in PV resource allocation and energy assessment. It provides a technology-agnostic solution on a European and global scale,” said Ana Martinez, scientific team leader at the JRC’s Energy Efficiency and Renewables Division and corresponding author of the study. pv magazine. “It also presents a new solution based on a distribution-based classification, rather than summary statistics, that encapsulates the time-dependent variability of PV energy output and provides insight into the potential for robust PV around the world.”
According to Martinez, the team generated a globally applicable classification using just 10 clusters. “That is the best trade-off between granularity and interpretability. It challenges the assumption that many more classes are needed to capture PV-relevant climate diversity and strikes a good balance between the 6-class scheme of IEC 61853-4 and the 12-class scheme of the Köppen-Geiger PV classification,” Martinez added.
Classification development began with an extensive PVGIS simulation over all emerging land between latitudes of −60◦ and +75◦, with a temporal resolution of 1 hour and a spatial resolution of 0.1◦× 0.1◦. For Europe they used a spatial resolution of 0.05◦× 0.05◦; the continent was subjected to a more detailed analysis in the paper. In both cases, 19 years of historical climatological data were used, spanning the period 2005-2023. These simulations used equator-oriented ground-based crystalline silicon PV modules with optimized tilt for annual yield.
Given all these data points, the researchers wanted to identify climate variables that strongly correlate with the PV performance metrics PV array energy yield (YA) and module performance ratio (MPR), without relying on a specific module model. Based on their simulation, they found that annual irradiance (Hyear) shows strong correlations with YA. In contrast, the MPR was found to have a high correlation with a new radiation-weighted module temperature (TW).
Furthermore, the group developed a distribution-based approach to take into account the growing importance of variability in PV generation. To do this, they applied optimal transport theory to the distribution of daily irradiance, grouping locations with similar daily generation characteristics into ten clusters. “This method is better suited to applications where generation variability, rather than annual averages, is the key characteristic of interest, such as robust power generation,” the group explains.
“We observed that high altitude areas and the hottest deserts share a similar, uniformly high daily radiation profile, which causes them to be grouped together,” Martinez said. “This is surprising because these two environments have very different temperature regimes and have traditionally been treated as separate climate zones.”
In closing, Martinez added that the group decided to publish the book facts and models developed to enable other researchers to reproduce and also extend the analysis. “Proposed follow-up research could extend the classification framework to a broader range of PV setups (rooftop PV, vertical PV, single-axis tracking) and technologies (bifacial PV, perovskite/c-Si tandem), which will likely require the addition of new parameters such as albedo. Likewise, it would be worthwhile to include reliability considerations such as degradation or failure rates,” she added.
The new classification framework appeared in “Parametric and distribution-based definition of climate zones for photovoltaicss”, published in Solar energy. It was developed by researchers from Ispra (VA), Italy and the JRC University of GottingenGermany.
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