Karim M.,Moroccan Foundation for Advanced Science Innovation and Research MAScIR Rabat |
Karim M.,Cadi |
Naamane S.,Moroccan Foundation for Advanced Science Innovation and Research MAScIR Rabat |
Delord C.,French National Solar Energy Institute |
Energy Procedia | Year: 2015
Solar mirrors are exposed, during their operation in Concentrated Solar Power plants -CSP-, to climatic stress factors that cause their degradation and therefore a decrease in the global efficiency of the plant. Sandstorms are among parameters that cause a decrease of mirrors optical performances by generating surface erosion. The intensity and the gravity of this erosion phenomenon is function of climatic, geological parameters and mirrors surface nature. To evaluate the effect of these parameters on the optical performance degradation, two approaches were adopted, namely the natural aging tests in two different sites in Morocco, and the aging tests in controlled environment in a sandblasting chamber. The objectives are, by monitoring the stress factors in natural aging sites, to define aging tests under controlled environment that reproduce similar degradation phenomenon that those observed on mirrors exposed in natural aging sites. Degradations observed in both natural and controlled aging tests are compared and correlated to validate the methodologies and the hypotheses on the analysis of the degradation phenomenon. The aging tests in controlled environment permits the evaluation of the effect of each influencing parameter separately from the others on the mirrors surface erosion, and eventually accelerate the apparition of surface erosion on mirrors. Under controlled environment, tests show that glass mirrors present maximum surface erosion at normal impact angle and that the loss in specular reflectivity is directly related to the wind speed. Exposed mirrors in natural aging sites present low loss in reflectivity which doesn't exceed 0.4% after 240 days of outdoor exposure. Concerning the effect of sand properties on erosion phenomenon, it was found that the sand hardness affect the roughness parameters, whilethe sharp forms influence on the impactsproperties(roughness parameters, impacts number, impacted area, impacts size diameter). By increasing the sand particle's size, the impacted area increase and the losses in relative specular reflectivity increase. © 2015 The Authors. Published by Elsevier Ltd.