Energy, exergy, economic and environmental-based design, analysis and multi objective optimization of novel solar tower-based gas turbine cycle multi-generation systems with new performance criteria

Abstract

Global demand for energy has been rising steadily with increasing population, industrialization, urbanization and life standards. In order to meet this demand, fossil fuels such as oil, coal, natural gas etc. have been utilized intensively. However, this intense use resulted in environmental issues caused by harmful emissions of fossil fuels. Therefore, utilization of renewable energy such as solar, wind, geothermal etc. have been proposed as a solution to cope with these problems caused by fossil fuels. Additionally, energy efficiency has also been considered as another pillar for decarbonization. Firstly, cogeneration systems which produce power and heating simultaneously from the same energy source evolved with a significant increase in total energy efficiency of the plant compared to only power generation. Later, tri-generation systems are evolved to further improve the efficiencies and to provide cooling in addition to heating and power. Recently, multi-generation (MG) systems which provide at least four utilities such as power, heating, cooling, fresh water, hydrogen, domestic hot water (DHW), drying, various chemicals etc. have become focus point for research due to higher efficiencies, compactness, product versatility, economic feasibility and ability to work with renewables. Among various renewable energy sources, solar energy has received increased attention, and several attempts to use concentrated solar energy as a primary energy source for MG systems have been observed. Despite several detailed analysis of other technologies-based MG systems, solar tower-based open air gas turbine cycle (SGTC)-driven MG systems lacked sound research, comprehensive analysis considering thermodynamic, economic and environmental performances simultaneously and multi-criteria multiobjective optimization. Furthermore, investigations of complicated Brayton cycle (BC) structures such as intercooling, regeneration, and reheat systems, as well as inclusion and extensive study of hydrogen production in such systems, were lacking. Moreover, proper evaluation criteria for comparison of such systems to each other were not considered thoroughly in literature. Therefore, fulfilling lack of research in these areas constitutes the motivation behind this PhD study. The present PhD thesis is composed of three (3) peer-reviewed international journal papers and one (1) international conference proceeding paper. In the first part, a novel MG system is developed for production of power, heating, cooling, green hydrogen and DHW. A unique power system structure is developed by using intercooling-regenerative (IR)-SGTC, organic Rankine cycle (ORC) and Kalina cycle (KC). By this thesis, intercooling waste heat is used for power generation in an IR-SGTC based MG system for the first time in the literature. MO optimization, environmental analysis and hydrogen production were introduced into such system analysis for the first time in addition to energy and exergy analyses. A novel thermodynamic performance criterion is coined as "exergetic quality factor" (EQF) to compare, analyze and maximize exergy content (quality) within energy quantity of MG products. Additionally, a significant contribution to literature is done by correcting a common misuse in exergy value calculation of solar energy in majority of other works in literature. This study is published in Energy Conversion and Management. In the second part, a unique MG structure is proposed with an intercooling-regenerative-reheat (IRR)-SGTC system for the first time in literature. Moreover, first time in literature, a MO optimization is performed for a multi-product IRR-SGTC system. Furthermore, an optimization by using thermodynamic, economic and environmental criteria simultaneously on IRR-SGTC system is performed first time in literature. The proposed system is designed to produce electricity, cooling, various temperature level heating purposes, green hydrogen, fresh water, hot air for drying and DHW. The study is published in ASME Journal of Energy Resources Technology. In the third part, a thermal energy storage (TES) is coupled to a MG system based on IRR-SGTC for the first time. Furthermore, a unique set of power cycles are formed by addition of RC and KC in series to the exhaust of IRR-SGTC. Effect of electrolyzer (EL) power size fraction to the total MG power size is investigated for the first time. Furthermore, first time in literature hydrogen is considered as the main product in MO optimization, and thermodynamic and economic analyses are performed. The proposed products are green hydrogen, power, cooling and DHW. The study is published in International Journal of Hydrogen Energy. In the fourth part, integration of two (2) ORCs into intercooling and exhaust waste heat streams of a MG system driven by an IR-SGTC is performed for the first time. Also, it is the first solar-based MG study in literature that investigates various climatic conditions and critical utilities of the Mediterranean region cities of Turkey. MO optimization and energy, exergy and environmental analyses are conducted. Proposed MG products are power, fresh water, green hydrogen, cooling, DHW and industrial process heating. The study is disseminated in the 11th International 100% Renewable Energy Conference (IRENEC 2021) and published in the proceedings book. In summary, within the scope of this PhD thesis, various novel MG systems based on IR- and IRR-SGTC are proposed with increased energy and exergy efficiencies, improved economical feasibilities and significant emission reductions. Furthermore, rigorous MO optimizations are performed by using these performance criteria simultaneously. A novel thermodynamic performance criterion is coined and a common misuse in literature is corrected in the present PhD study. Hydrogen production is introduced as the main product, fraction of EL power is introduced as a design parameter and investigated thoroughly and intercooling waste heat is recovered to produce power for the first time. Climatic conditions of Mediterranean region cities of Turkey are compared for the optimum performance of such systems. The present PhD study proposes a broader range of utilities as MG products of SGTC-based systems than any previous study in the literature, including power, green hydrogen, cooling, varied temperatures and purposes heating, DHW, hot air for drying, and fresh water.