Extract

Roof-mounted unglazed solar collectors are one of the most promising low-cost renewable energy technologies. However, their application is limited due to wind-induced heat loss which reduces their performance. That said, the wind flow over roof surfaces, where solar collectors are typically mounted, can be affected by a host of parameters related to the surrounding terrain and building topology. Perimetric parapets have shown an ability to reduce wind loads on roofs, particularly in low- rise buildings, and it is conceivable that this may also benefit solar collectors. Studies related to the effect of parapets on roof-mounted solar technologies have however been limited to wind loads on roof-top equipment or structural support systems, rather than on the heat loss. In this study, the performance of an unglazed solar collector mounted on a low-rise building with perimetric parapets was examined through wind tunnel experiments and computational fluid dynamics (CFD) simulations. The average pressure coefficients determined from the wind tunnel measurements were used to validate steady-state 3D Reynolds Averaged Navier-Stokes simulations. Subsequently, simulations were carried out for different wind velocities and directions with variations in parapet height. When normalised with Reynold’s and Nusselt numbers, the results showed the quantitative effect of these parameters. It is shown how sensitive the thermal performance of the collector is to parapet height, wind velocity and collector mounting location.

Keywords: Solar Collector, CFD, Parapets. Keywords: Solar Collector, CFD, Parapets

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