Enhancement of solar PV systems efficiency through changes in array configuration: The role of fluid dynamics in solar energy.*

Efficiency of solar PV cells is linearly dependent on its temperature. Per each degree Celsius above standard test conditions (STC, traditionally 25ºC), efficiency of traditional solar PV cells decreases by 0.5%. Depending on the installation site, operational temperature can be more than 50ºC above standard temperature, with a corresponding reduction in efficiency of more than 25%. Therefore, there is a strong interest not only to develop new solar PV cells made of materials with lower thermal sensitivity (i.e. minimization of the thermal sensitivity), but also to find strategies that can help mitigate the thermal losses.

In this work, we have focused our efforts to enhance convective cooling of solar PV systems with the design of innovative solar module arrangement strategies. The objective is to find new approaches to the installation of solar modules that boost energy harvesting efficiency through the reduction of thermal losses by simple and costless changes of arrangement. For this purpose, we have developed an array of field experiments, scaled wind tunnel measurements, and controlled numerical simulations. With these combined strategies we have quantified the effect on the convective cooling of changes in module row spacing, module height, module orientation, and the use of flow deflectors and vortex generators. The rich dataset has enabled us to develop a new scaling relation between the Nusselt, Prandtl, and Reynolds numbers that takes into consideration not only the flow momentum and thermal characteristics, but also the spatial arrangements of the system. To encapsulate all the variables defining the geometry of the PV system, we have developed a new length-scale based on the metric of lacunarity.

Results from this work illustrates the relevant role the fluid dynamics community can play in developing another prominent renewable energy system.