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Trigeneration energy systems have gathered considerable attention from energy specialists and energy economists. When adequately designed, trigeneration systems reduce the overall cost of energy production and lower the carbon footprint for every energy unit generated. However, their implementation in the buildings’ industry faced many obstacles such as the inefficient sizing of their capacities, and their sub-optimal operational scheduling, which have led to high investment and operational costs compared to conventional systems.
Accordingly, an optimization tool has been modeled to find optimal planning, sizing and scheduling of trigeneration systems. The tool is used in decision-making process in all project phases. This is done by applying the energy hub concept under the constraints of maximizing a formulated combined efficiency that contains annualized total cost saving ratio (ATCSR), exergy efficiency (EXEff), fuel saving ratio (FSR) and carbon dioxide reduction ratio (CO2RR) using a weighing factor method. This is made by comparing each indicator to a conventional system in GAMS. Moreover, economical parameters (net present value, internal rate of return and payback period) are used to guarantee proper decision-making process. Using part load effect and variable capital costs of components to simulate the real case, the tool provides optimal planning, sizing and scheduling of all trigeneration systems.
Three case studies have been adopted in this thesis as direct applications for the optimization tool. One of them has dealt with the quantification of error resulting from using simple (constant efficiency) and linearized models for simplicity instead of part load (variable efficiency) models which simulate the real case and to what extent this approximation is valid and whether it should be used in future studies or not. A novel contribution has been presented to compare between both models which the Root Mean Square Difference (RMSD). It depends on the deviations of the combined efficiency the economic parameters. Results assured the importance of using part load models in future studies to guarantee more accuracy as deviations of results between both models can’t be neglected.
The second one has dealt with the intervention of solar energy components such as: solar thermal collectors (SCs) and photovoltaics (PVs) into optimized trigeneration system by comparing a solar energy optimized trigeneration system to an optimized trigeneration system with no solar energy utilization. This thesis provides a system-comparison methodology to compare such systems. This optimal system-comparison gives a complete picture on the real effect of adding any solar component to a trigeneration system because it gives the solar system the freedom for more intervention with the system resulting in more enhanced performance. Results assured the importance of comparing energy systems based on the system-comparison methodology. Moreover, they came up with the conclusion that reducing the capital costs of solar energy systems will facilitate their deployment in future energy systems as they already prove their ability to increase overall combined efficiency of energy systems by decreasing the fuel used and emission produced.
The third one has dealt with the concept of Hybrid photovoltaic/ thermal collectors (PV/Ts) technology after they have evolved as a translation to the typical idea of the trigeneration because they produce both heat and electricity simultaneously with the same area decreasing the footprint needed by side-by-side photovoltaics (PVs) and solar thermal collectors (SCs). A methodology of real system-level comparison is presented in contrary to component-level comparisons that are available in the open literature. This methodology depends on comparing an optimized Solar-CCHP system with side-by-side PVs and SCs, against a PVT-CCHP with hybrid photovoltaic/thermal collectors (PV/Ts) instead under a constrained area. Results came up with the conclusion that using PV/Ts instead of side-by-side PVs and SCs will yield higher combined efficiency but with lower Net Present Value (NPV) at normal price mode but with increasing the selling prices of sold electricity, PV/Ts are favorable due to higher combined efficiency and Net Present Value (NPV).
Solar Thermal collectors
Hybrid photovoltaic/thermal collectors
Key Performance Indicators (KPIs)