Optimization of Plant Size and Heliostat Field for UAE Atmospheric Turbidity Regimes

Abstract

Atmospheric conditions pose a great impact on the performance of concentrated solar power (CSP) towers. The presence of aerosols leads to scattering and absorption of direct beam radiation, which reduces the intensity of direct normal irradiance reaching the receiver. This study builds on preexisting methods such as the study presented by Elias and He, to model the extinction coefficient of the atmospheric boundary layer in the United Arab Emirates. This involves utilizing on-site Aerosol Optical Depth (AOD) measurements at Masdar Institute Solar Platform (MISP) in Abu Dhabi, recorded using a Cimel sun photometer. Radiosonde measurements are also utilized from the Integrated Global Radiosonde Archive (IGRA) in order to obtain the height of the atmospheric boundary layer (ABL) from Abu Dhabi International Airport which is used to obtain the extinction. The derived extinction is further utilized in optimizing the modelling of a CSP tower model by using the software tools SolarPILOT and TracePro. SolarPILOT is used to assess the impact of extinction on CSP tower plants, while TracePro is used to model the beam down geometry introduced by Rabl in 1979. A Matlab code used to build the Beam Down Optical Experiment at MISP from previous theses is optimized to create a virtual commercial sized beam down plant with user defined input variables, and test the impact of extinction through raytracing. The final model comprises of a CSP tower plant with a naïve estimation of the extinction caused by aerosols in the ABL. Five CSP tower plants with the same tower optical height to field radius ratio are analyzed in order to study the total beam attenuation efficiency and its relationship with plant size. The final result display a decrease in total beam attenuation efficiency of 6.83% in December, and 47.7% in May between the 78:560 model and 234:1690 model. This indicates the heavy impact of beam attenuation on the total optical efficiency of a CSP tower plant. Additionally, a comparison between the beam attenuation efficiency of a CSP tower system, a multi-tower system, and a beam down CSP system with the same incident field power is carried out. The results assert the importance of relying on multi-tower systems in arid regions similar to the UAE in order to mitigate the effects of atmospheric attenuation. Finally, a basic miniature CSP tower plant model is also imported onto NREL's SolarPILOT software, where the performance of this model will be compared to the same model on TracePro in order to verify the results of the TracePro model. The advantages of using TracePro over SolarPILOT is the flexibility of TracePro, and the ability to model a beam down geometry which is unavailable on SolarPILOT. TracePro will also be used to demonstrate an optimized version of the Beam-Down optical experiment at MISP. Previous research done on the beam down optical experiment will be utilized for further optimization done to the preexisting model, such as the addition of D & E rings, as well as filling any spaces in the preexisting A, B & C rings. The following study is of importance for the gulf region as the number of planned CSP tower projects & issued tenders is increasing, and no sufficient data is available to estimate & simulate the optical losses introduced by the dusty, arid and humid environment of the UAE. This model will allow industrial professionals to develop a CSP tower plant model with ease, while also obtaining a naïve model on the impact of aerosols on its performance.

Date of Award	Jul 2020
Original language	American English