Simulation of Flow Over Flat Plates for PV Wind Loads Assessment
Date
2019-05-15
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Abstract
The ability to accurately predict wind loads on photovoltaic (PV) modules is becoming increasingly desirable in many aspects of engineering as the popularity of renewable energy grows. The decrease in cost of PV units and batteries, as well as the advancement in battery and PV power output are contributors to this surge in popularity, to name a few. These technological advancements, coupled with increases in urbanization and incentives to move towards clean energy have contributed to a rise in popularity of roof-mounted solar panels on buildings in city environments where buildings are exposed to strong winds phenomena, such as downwashing from surrounding buildings. In-situ full-scale measurements of these wind flows can be challenging, and it is common that loading values are desired in the design phase of construction. Historically, the most common method of replicating wind flows in an experimental environment has been with wind tunnels. However, this method can present drawbacks concerning instrumentation, scaling, labour intensity, cost and time consumption. As such, consultants and industry are looking towards computational fluid dynamics (CFD) to perform fast and cost-effective measurements. CFD simulations that involve solar panels and surrounding environments are typically performed using Reynolds Averaged Navier-Stokes (RANS) equations due to the complexity of the geometries involved. In RANS modelling, a number of the turbulence relationships must be modelled. This introduces the possibility of inaccuracy but it reduces the overall time of the simulation and can be applied to more complex geometries. The intent of this study was to examine the behaviour of steady state, incompressible flow around normal and inclined flat plates relative to the oncoming flow at a Reynolds number of 1200 using Reynolds Averaged Navier-Stokes (RANS) equations. The angled plates simulate PV modules in a variety of different environments. Three different turbulence models were used to close the RANS equations; the standard k-epsilon model (SKE), the shear stress transport k-omega model (SST k-ω) and the renormalization group k-epsilon model (RNG k-ϵ). Five Cases were created to validate the numerical setup of the current study, establish a baseline and explore the effects of common environments on the solar modules. The parameters that were collected for the various simulations were the drag (Cd) and lift (Cl) coefficients, the mean recirculation lengths behind the plate (Lw) and the streamwise velocities and turbulence kinetic energy readings along the centrelines of the plates. The simulations were completed using openFOAM, an open source CFD software. Case 1 focused on comparing Cd and Lw on flat plates to experimental data and to direct numerical simulations of the Navier-Stokes equations to ensure accuracy. Case 2 then established a baseline, similar to Case 1 but with angled plates. Cases 3 through 5 then introduced additional geometries for angled plates. The validation process in Case 1 was successful, with the results of the current study coinciding well with existing literature. Cd progressively declined in magnitude from Cases 1 through 4, but generally showed marginal increases in magnitude from Case 4 to 5 when a building step was introduced. Both Cl and Lw generally increased between Cases 2 through 5, while Case 1 showed larger values than Case 2. The SKE turbulence model usually showed larger turbulence kinetic energy values around the plate for all the Cases and the shortest Lw in Cases 4 and 5 when compared to the other turbulence models.
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Keywords
Fluid Dynamics, CFD
Citation
Brydges, J. (2019). Simulation of Flow Over Flat Plates for PV Wind Loads Assessment (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.