Development of a mathematical model for area sizing and performance estimation of a Parabolic Troughs Solar Field

CSP technology is a powerful and smart way that allows to produce power by using mirrors to concentrate solar beams on a small area. This thesis work is focused on theorizing and estimating the performance of a parabolic trough solar field not only from a theoretical point of view but also from a practical one through a Matlab model developed with the help of two professors from department of Water, Energy and Environment of the Cranfield University. Such technology is already in use, and a new one is currently under construction Solar field in NEOM, Saudi Arabia, intended to fuel a Multiple Effect Desalination Water Plant with the help of a thermal storage system. A preliminary analysis, along with the processing of the weather data (specifically, from the meteorological years between 2005 and 2017) has been done in order to gather the necessary information that will allow to develop the best tracking strategy. Along with the yearly weather data, the other main parameters taken into consideration for the development of the model have concerned the inherent features proper of the material and the structure, specifically: geometrical and materials specifications of the collector, the temperature difference between inlet and outlet, number of parallel collector’s rows, the spacing between each one of them and the tracking strategy adopted. The same model with a proper different code setup can predict and estimate the reflective area needed to achieve specific design user’s requests. The model can estimate the concentrated power Q ̇_conc along with all the losses involved in the process. As a consequence it is possible thus to calculate the actual useful power (the one absorbed by the heat transfer fluid) Q ̇_use. For this purpose, a very detailed sun tracking model has been implemented as well as another one for the shading losses which depends on the collectors’ movements. Optical performances and inaccuracies have been also taken into account and estimated, and in particular a delicate step was the evaluation of the so-called “Intercept Factor” through a statistical approach. Another very detailed approach has been necessary for the evaluation of the heat exchange involved at the receiver: for this purpose a non-linear equation system has been implemented, to be solved with a proper Matlab function. At first, this system is solved multiple times (iteratively, using the Bisection method) for the calculation of the mass flow rate needed to achieve a correct temperature difference, then for the actual performance. The sizing calculation led to results very close to the initial rough estimations, with the user requirements having been the following ones: the temperature difference between the inlet and the outlet section of the field (300° inlet,380°C outlet), some working power value for a specific percentage time the year. Several parametrical studies have been made, a very important one is the spacing sensitivity analysis: the effect of the distance between each row on the annual energy collected has been analyzed. Results showed that by increasing too much this distance no significative gains are obtained. In conclusion, results has been satisfactory and suitable for the sizing and optimization of the Solar Field in NEOM under construction.