This thesis aims to present the research conducted during the Ph.D. period comprehensively. As the title suggests, the work encompassed various aspects related to the overarching theme of solar energy and modelling, characterized as a holistic investigation into diverse practical issues concerning solar energy. The first part of the thesis introduces the 3D raytracing model FresnelSim, developed and refined throughout the Ph.D. program from previous research activities by the same author and research group. This model specializes in simulating and parametrically analyzing linear Fresnel solar systems. The simulation algorithm, implemented in Matlab, was validated against results from the open-source software Tonatiuh, a prominent tool for raytracing analyses. Following a presentation of the constitutive relationships and key equations governing raytracing, parametric analyses are presented focusing on optimizing geometric design parameters to maximize energy available to the receiver and/or to the heat transfer fluid flowing into an evacuated tube; these analyses include investigations into real plant geometries, notably those in Ben Guerir, Morocco, and Partanna, Italy. Another aspect examined is the impact on plant productivity due to orientations different from the optimal north-south alignment: notably, it is well-known that higher annual peaks can be achieved with plant orientations aligned along the north-south axis, while comprehensive analyses on the implications of alternative orientations, which are often necessitated by space constraints, are lacking in the literature. Additionally, leveraging the computational capabilities of FresnelSim, a new correlation for analytically calculating the Incidence Angle Modifier is proposed, departing from the conventional factored relationship, which often happens to be inaccurate. A second research thread concerns the estimation of optimal tilt angles for photovoltaic modules to maximize their annual productivity. The mathematical model that was developed integrates geographic and climate considerations to establish correlations between these parameters and the best tilt and has been applied to case-study locations in France and Italy. Particularly, while real-world applications often employ a tilt angle equal to latitude, possibly decreased by 5°-10°, the optimal value is contingent upon deviations from ideal clear sky conditions: after the identification of such dependencies and computation of optimal angles for over 200 locations, an analytical equation is derived for tilt angle calculation across ideally both national territories. Furthermore, for a comprehensive analysis, distinct coefficients were identified based on the orientation angle of the capturing surface, yielding multiple angle sets for non-South facing surfaces. The same approach, which accounts for both isotropic and anisotropic diffuse insolation relationships, has been also applied to a set of Canadian cities with the aim of identifying the best tilts across the country and comparing results with those from available online resources with reference to locations characterized by completely different climate conditions with respect to the European ones. A third aspect herein addressed involves the integration energy systems, including photovoltaic ones and thermal storages, into urban settings. A model was developed for a sensible heat thermal storage system to be integrated into the existing smart grid at the University of Genova campus located in Savona, Italy: based on a stepped two-zone approach, the model was embedded within the broader Energy Management System of the grid, allowing the optimization of storage tank size considering economic parameters as well as greenhouse gas reductions associated to the thermal storage beneficial effect. Input data for the analysis are based on 2-year records of thermal and electrical loads and photovoltaic energy production. A further research topic is the study of the photovoltaic potential of Genova rooftops: to assess the number and area of available surfaces for photovoltaic installations within the urban environment, a GIS-based 3D model of the built environment has been developed including proper hourly solar energy availability. The solar yield analysis has been carried out by building a cumulative 3D tiled sky to identify the most profitable surfaces in terms of size and expected annual insolation and near and far obstacles have been taken in consideration. Statistical processing of a reduced number of suburbs' rooftop surfaces have been calculated concerning their dimensions and reasonable insolation thresholds for considering profitable photovoltaic installation. Lastly, during the Ph.D. period, a model was developed for predicting temperature and relative humidity parameters in an underwater greenhouse as part of the Nemo Garden® project. Although not directly aimed at energy production, this activity incorporates solar energy considerations in the model’s governing energy balance equations: indeed, the analytical model, which accounts for attenuated insolation due to the water column overlying the greenhouses, was validated against available measurements for a real installation in Noli, Italy, demonstrating high accuracy in estimating the aforementioned parameters of interest.
Enhancing the Efficiency in Solar Systems: Time-Variant Modelling and Ray Tracing with Reference to Solar Energy Conversion Technologies in Concentration and Photovoltaic Systems
MEMME, SAMUELE
2024-12-06
Abstract
This thesis aims to present the research conducted during the Ph.D. period comprehensively. As the title suggests, the work encompassed various aspects related to the overarching theme of solar energy and modelling, characterized as a holistic investigation into diverse practical issues concerning solar energy. The first part of the thesis introduces the 3D raytracing model FresnelSim, developed and refined throughout the Ph.D. program from previous research activities by the same author and research group. This model specializes in simulating and parametrically analyzing linear Fresnel solar systems. The simulation algorithm, implemented in Matlab, was validated against results from the open-source software Tonatiuh, a prominent tool for raytracing analyses. Following a presentation of the constitutive relationships and key equations governing raytracing, parametric analyses are presented focusing on optimizing geometric design parameters to maximize energy available to the receiver and/or to the heat transfer fluid flowing into an evacuated tube; these analyses include investigations into real plant geometries, notably those in Ben Guerir, Morocco, and Partanna, Italy. Another aspect examined is the impact on plant productivity due to orientations different from the optimal north-south alignment: notably, it is well-known that higher annual peaks can be achieved with plant orientations aligned along the north-south axis, while comprehensive analyses on the implications of alternative orientations, which are often necessitated by space constraints, are lacking in the literature. Additionally, leveraging the computational capabilities of FresnelSim, a new correlation for analytically calculating the Incidence Angle Modifier is proposed, departing from the conventional factored relationship, which often happens to be inaccurate. A second research thread concerns the estimation of optimal tilt angles for photovoltaic modules to maximize their annual productivity. The mathematical model that was developed integrates geographic and climate considerations to establish correlations between these parameters and the best tilt and has been applied to case-study locations in France and Italy. Particularly, while real-world applications often employ a tilt angle equal to latitude, possibly decreased by 5°-10°, the optimal value is contingent upon deviations from ideal clear sky conditions: after the identification of such dependencies and computation of optimal angles for over 200 locations, an analytical equation is derived for tilt angle calculation across ideally both national territories. Furthermore, for a comprehensive analysis, distinct coefficients were identified based on the orientation angle of the capturing surface, yielding multiple angle sets for non-South facing surfaces. The same approach, which accounts for both isotropic and anisotropic diffuse insolation relationships, has been also applied to a set of Canadian cities with the aim of identifying the best tilts across the country and comparing results with those from available online resources with reference to locations characterized by completely different climate conditions with respect to the European ones. A third aspect herein addressed involves the integration energy systems, including photovoltaic ones and thermal storages, into urban settings. A model was developed for a sensible heat thermal storage system to be integrated into the existing smart grid at the University of Genova campus located in Savona, Italy: based on a stepped two-zone approach, the model was embedded within the broader Energy Management System of the grid, allowing the optimization of storage tank size considering economic parameters as well as greenhouse gas reductions associated to the thermal storage beneficial effect. Input data for the analysis are based on 2-year records of thermal and electrical loads and photovoltaic energy production. A further research topic is the study of the photovoltaic potential of Genova rooftops: to assess the number and area of available surfaces for photovoltaic installations within the urban environment, a GIS-based 3D model of the built environment has been developed including proper hourly solar energy availability. The solar yield analysis has been carried out by building a cumulative 3D tiled sky to identify the most profitable surfaces in terms of size and expected annual insolation and near and far obstacles have been taken in consideration. Statistical processing of a reduced number of suburbs' rooftop surfaces have been calculated concerning their dimensions and reasonable insolation thresholds for considering profitable photovoltaic installation. Lastly, during the Ph.D. period, a model was developed for predicting temperature and relative humidity parameters in an underwater greenhouse as part of the Nemo Garden® project. Although not directly aimed at energy production, this activity incorporates solar energy considerations in the model’s governing energy balance equations: indeed, the analytical model, which accounts for attenuated insolation due to the water column overlying the greenhouses, was validated against available measurements for a real installation in Noli, Italy, demonstrating high accuracy in estimating the aforementioned parameters of interest.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
