Article written by
Reinaldo Burcon Junior – Industrial Development Engineer Pl
The sizing of photovoltaic structures is a complex process that requires consideration of several factors to ensure both the safety and efficiency of the installation.
This process involves not only compliance with specific standards and regulations, but also the application of engineering principles and detailed analyses to predict the behavior of the structure under different environmental and operational conditions.
In this article, our Industrial Development Engineer Pl – Reinaldo Burcon Junior, details everything about the Sizing of Photovoltaic Structures.
Issues to be considered:
Standards and Regulations:
NBR-6123 and ASCE7-22
These standards deal with the sizing of structures in relation to the action of wind. NBR-6123 is the Brazilian standard, while ASCE7-22 is an American standard. In many cases, using both standards in parallel can provide a more comprehensive and accurate view of the conditions that the structure will face.
It may be necessary to consider both, as each standard may offer specific guidelines and coefficients for different situations and geographic regions.
Types of Loading:
STATIC AND DYNAMIC LOADING:
Static loading refers to constant and predictable forces applied to the structure, while dynamic loading involves variable and unpredictable forces, such as wind gusts. Both forms of loading must be considered.
PREDOMINANCE OF LOADING
The predominance of one type of loading over the other depends on the environment and the location of the installation. In regions subject to strong winds, dynamic loading may be more critical.
Image of the equivalent static wind load survey on the arrays of panels (example of the work to be done):
Analysis and Modeling:
STROUHAL NUMBER AND DIMENSIONAL ANALYSIS:
The Strouhal number is crucial to understand the effects of vortices and oscillation frequencies on the wind behavior around the structure. Dimensional analysis helps to scale the results of reduced models to the real structure.
CFD ANALYSIS (COMPUTATIONAL FLUID DYNAMICS)
The use of CFD is essential to simulate the behavior of air flow around PV structures. Methods such as RANS (Reynolds-Averaged Navier-Stokes), URANS (Unsteady RANS) and LES (Large Eddy Simulation) have different levels of accuracy and computational demands.
RANS: Suitable for medium flow and less computationally intensive analyses.
·URANS: Considers short-term fluctuations, useful for analyzing transient behaviors.
·LES: Provides more accurate details of turbulences, but requires greater computational power.
Computational Time vs. Response Accuracy:
BALANCING TIME AND ACCURACY:
Finding a balance between computational time and analysis accuracy is crucial.
More accurate methods, such as LES, can provide detailed results, but at a high computational cost.
Choosing the appropriate method depends on the specific needs of the project and the resources available.
Importance of Technical Understanding
It is essential that the engineer has a deep understanding of the physics and mathematics behind the CFD software tools used.
Effective use of these tools requires technical knowledge to interpret the results correctly and make precise adjustments to the model as needed. The approach cannot be simplistic, as an inadequate analysis can lead to serious errors in the dimensioning of the structure, compromising the safety and efficiency of the photovoltaic system.
All of these issues are essential to ensure the safety and efficiency of photovoltaic structures. Detailed consideration of standards, load types, wind behavior, analysis techniques and computational limitations allows engineers to develop robust and optimized designs capable of withstanding the most challenging environmental conditions while maintaining the operational efficiency of solar panels.
