Open-source tool for CPV system modeling

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A research team led by the Universidad Politécnica de Madrid (UPM) in Spain has created an open-access modeling tool for the design of concentrating photovoltaic (CPV) systems.

Called cpvlib, the framework is described as a state-of-the-art tool to address the modeling of CPV systems. “The need for such a tool arises from the limitations observed in existing PV simulation tools, leading to the development of an adaptable and open-source solution,” the research's corresponding author, Rubén Núñez Júdez, told pv magazine. “The basis of cpvlib lies in the well-established pvlib framework, a collection of functions and classes designed for the simulation of PV power systems developed in Python supported by the open-source community. The code is hosted in a public repository, fostering a collaborative environment with features such as online documentation, issue tracking, code style guidelines, continuous integration development, and comprehensive test coverage.”

The cpvlib philosophy is configured as a modular tool that can accurately predict the energy production of various CPV configurations. “Unlike some PV simulation tools that incorporate CPV models as proprietary components, cpvlib stands out for its flexibility and adaptability,” Núñez Júdez said. “Traditional models are often unable to integrate state-of-the-art architectures and modeling methods, which hinders progress in this field. Examples of these innovations include integrated tracking, planar micro-tracking, and hybrid CPV-flat plate modules for efficient scattered light collection. The cpvlib library fills this gap by providing a flexible model designed for these novel architectures, with the ability to easily adapt to new developments.”

The new tool was presented in “cpvlib: A comprehensive open-source tool for modeling CPV systems,” published in Solar Energy Materials and Solar Cells, where the research group explained it can analyze complex behaviors like air mass impact on CPV performance, angle of incidence limits, and light spillage. The tool's library uses PVSyst's utilization factors to model deviations from the single-diode model, accounting for spectral and thermal effects.

The proposed tool was validated through long-term monitoring of hybrid CPV/flat-plate modules developed by Swiss startup Insolight.

The company developed these CPV panels for agrivoltaics applications and is currently planning to start commercial production. The product spec states the CPV panel has a 30% efficiency and power output of 160 W at standard conditions of 25 C and 1,000 W/m2 irradiance. The product can reportedly operate with a maximum system voltage of 500 V and at temperatures ranging from -40 to 85 degrees Celsius. The 1,141 mm x 595 mm x 50mm module weighs 20 kg and, according to its developer, is as easy to install as conventional solar panels. Its connector is MC4-compatible and its junction box has an IP 67 rating.

The panel relies on expensive III-V multi-junction solar cells from an undisclosed manufacturer. The cells cover only 0.5% of the panel surface and are covered with protective glass and optical lenses to concentrate and direct sunlight onto them at around 100 times the intensity of standard solar glass. The cells are reportedly able to track the sun through horizontal movement

The modeling tool reportedly achieved a root mean square error of 2.7% to 3.5 % in the testing.

“Conventional PV technology based on flat-panel silicon has currently such as low levelized cost of energy (LCOE) that not only other PV technologies but also other power generation technologies fail to reach,” Núñez Júdez stated. “That is why CPV technologies can have potential in niche environments where their characteristics are enhanced, such as in locations with high direct irradiation. Furthermore, CPV systems can make use of high-efficiency cells, which is an advantage in applications where space is constrained. This is the case for example with buried contact cell modules, which have found a niche in residential installations.”

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