Real-time POD-CFD Wind-Load Calculator for PV Systems
Current status/problem: Wind loading calculations for structures are currently performed according to the ASCE (American Society of Civil Engineers) 7 Standard. The values in this standard were calculated from simplified models that do not necessarily take into account relevant characteristics such as those from full 3D effects, end effects, turbulence generation and dissipation, as well as minor effects derived from shear forces on installation brackets and other accessories. This standard does not have provisions to handle the majority of rooftop PV systems, and attempts to apply this standard may lead to significant design errors as wind loads are incorrectly estimated. Therefore, an accurate calculator would be of paramount importance for the preliminary assessments of the uplift and downforce loads on a PV mounting system, identifying viable solutions from available mounting systems, and therefore helping reduce the cost of the mounting system and installation. The challenge is that although a full-fledged three-dimensional computational fluid dynamics (CFD) analysis would properly and accurately capture the complete physical effects of air flow over PV systems, it would be unsuitable for this tool, which is intended to be a real-time web-based calculator. And that is because in order to arrive at solutions that can be deemed accurate and grid- independent, CFD routinely requires enormous computation times even in powerful and massively parallel computer platforms. Proposed solution: We propose a solution that would not only take advantage of the great detail and accuracy of a grid-converged 3D CFD analysis, but also calculate in real-time the loads that result from wind-induced drag and lift forces on PV systems. To that end, we intend to develop a real-time response framework based on the Proper Orthogonal Decomposition (POD) method. The key is to generate beforehand and off- line an extensive set of solutions using CFD within our defined design space (various module sizes, wind speed, topography, roof dimensions and pitch, etc.) and store them in a database. The web-based wind-load calculator would then access the database of known solutions and generate in real-time an approximated solution by means of the POD method, which can be thought of as a multifaceted interpolation that preserves the physics of the problem. Because the POD method can produce a low-order approximation of the solution field with minimal loss of accuracy and fidelity, it serves as a reliable, fast and accurate response surface within the design space that can enable a real-time web-based calculator. In addition, the POD method is favorable for this application as it provides many desirable numerical features such as model reduction, error filtration, and regularization. Furthermore, as the POD algorithms rely uniquely on algebraic manipulation of previously generated field data, the entire POD modeling framework can be implemented in modest platforms such as laptops and tablets while allowing for true real-time prediction of design parameters.
Small Business Information at Submission:
Central Technological Corporation
932 Larson Rd. Altamonte Springs, FL 32714-2036
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