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In this paper 3D simulations of four different horizontal axis wind turbine (HAWT) blade shapes with the same radius (0.65m) and airfoil profile (NACA4418) are presented. The first blade shape is optimal twist and tapered (OPT); this blade is designed using blade element momentum (BEM) theory. The second is un-tapered and optimal twist (UOT), this blade has the same twist distribution as the (OPT) but with a constant chord. The third is tapered un-twisted (TUT), this blade has the same chord variations as the OPT blade. The fourth is untapered un-twisted (UUT). The effect of nacelle, shaft and tower existence on the performance of the four designs has been investigated also in the present work.All simulations are performed by using shear stress transport (SST) k-ω turbulence model. The power coefficient of OPT blade reach to 0.317 at TSR = 5. Meanwhile, the maximum power coefficient (Cp=0.3348 at TSR=4) has been recorded in the UOT blade. The TUT and UUT blade recorded a lower power coefficient, this is due to their always operations in stall and turbulence conditions.

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This paper aims to present a new and novel experimental study for the usage of hydrogel beads with different bed configurations as a cooling attachment underneath solar panel. Four different bed configurations were studied using different layers and fins arrangements then compared with the un-cooled system. The best results were obtained using 3 rows of hydrogel beads with fins where the panel temperature dropped by approximately 10 ̊ C below the uncooled panel at 1000 W/m 2 (representing around 14% temperature drop comparing to the panels' initial temperature) leading to an increase in the electricity generation efficiency of 7.2 % compared with the un-cooled system.

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