a b s t r a c tThe present paper gives a numerical investigation of the effect of mirror curvature on optical performance of a Linear Fresnel Reflector solar field installed recently in Morocco. The objective is to highlight and discuss the effect of mirror curvature on the flux density distribution over the receiver and the system optical efficiency. For this purpose, a Monte Carlo-ray tracing simulation tool is developed and used to optimize the optical design taking into account the curvature degree of the heliostat field. In order to assess the accuracy of the numerical code developed and the validity of simulation results, a set of verification tests were developed and detailed within this article. Then, the optical performance of the system is evaluated as a function of mirror curvature and receiver height. The major challenge of this study is to find a trade-off between heliostat curvature and receiver height since lower and smaller receivers may reduce the system cost. It has been found that the flux distribution over the receiver and the optical efficiency of the system are relatively sensitive to the mirror curvature. We have demonstrated quantitatively how the use of curved mirrors can enhance the optical performance and reduce the required receiver size.

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Predicting the HAWT blades loads accurately is one of the most important parts in the wind turbine aerodynamics calculation, and is based on an accurate evaluation of the aerodynamic coefficients and of the upstream velocity field. However, these aerodynamic loads estimations remain a complicated task to perform due to the complex nature of the flow around the blades, and to their cyclical fluctuations, which can be a significant source of fatigue and vibration, resulting from the yaw, stall or turbulent conditions where the HAWT operate mostly. The main aim of the present paper is to develop a sophisticated computational model that can predict aerodynamic coefficients without using great amounts of computer time. This model is based on a strong viscous-inviscid interaction technique using the blowing velocity concept. The inviscid air flow around S809 is modeled using the potential theory of arbitrary wing sections and Prandtl-Glauert compressibility correction, the 2-D pressure potential coefficients calculations for any orientation and Reynolds number, were made. Whereas the viscous part is modeled by using the Von Karman momentum integral equation, which is resolved according to the flow regime, laminar or turbulent, the onset of flow transition governed by the viscous effects was determined by using Michel's criterion, and the boundary layer separation point location is determined from the shape factor by using Head's criterion. The numerical results of aerodynamic characteristics of HAWT blade S809 airfoil have been benchmarked against experiments for different angle of attack and Reynolds numbers, and generally a good agreement is obtained.

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