Hasan Ozcan

Thermodynamic modeling of a nuclear energy based integrated system for hydrogen production and liquefaction

Abstract A nuclear based integrated system for hydrogen production and liquefaction with a newly developed four-step magnesium–chlorine cycle is proposed. The system uses nuclear energy to supply heat for the Rankine cycle and Mg–Cl cycle, where the power produced by the Rankine cycle is used to run the electrolysis steps of the Mg–Cl cycle and liquefaction cycle compressors. The four-step Mg–Cl cycle is specifically designed to decrease the electrical work consumption of the cycle by capturing HCl in dry form with an additional step to conventional three-step cycle. A performance assessment study is undertaken based on energy and exergy analysis of the subsystems, and total energy and exergy efficiencies of the plant are found to be 18.6%, and 31.35%. The comparisons of the subsystem efficiencies and total exergy destructions show that highest irreversibility ratio belongs to the Mg–Cl cycle by 41%, respectively.

Comparative Assessment of Nuclear Based Hybrid Sulfur Cycle and High Temperature Steam Electrolysis Systems Using HEEP

Hydrogen is one of the most promising alternatives as a replacement for the fossil fuels, since it can be produced by several methods using numerous sources. Sustainable production of hydrogen is highly dependent on the energy source utilized. Nuclear and renewable energy resources are considered as the best candidates for sustainable hydrogen production. Although there are numerous methods possible for hydrogen production, cost and economic factors play a crucial role in the feasibility and applicability of such plants. In this study, cost assessment of nuclear hydrogen production methods can be comparatively evaluated using Hydrogen Economy Evaluation Programme (HEEP) provided by International Atomic Energy Agency (IAEA). HEEP software is a user friendly cost estimation package, including various nuclear reactor options, as well as hydrogen generation, storage and transportation facilities. Rather than the existing data, HEEP offers user defined options from energy source to end user. Futhermore, hybrid sulfur (HyS) thermochemical cycle and high temperature steam electrolysis (HTSE) hydrogen generation systems are compared using high temperature reactors by considering storage and transportation options. The results show that the cost of hydrogen from HyS is 20 % lower than that of HTSE. HTSE requires more power consumption than HyS cycle, which has the highest impact of plant and production costs.

Thermodynamic Analysis of a Solar Driven Tri-generation System for Building Applications

Energy and exergy analyses and sustainability assessment of a conceptual solar driven tri-generation system with thermal energy storage option for power, water heating and air cooling are performed. The present tri-generation system includes parabolic trough solar collectors (PTC), an organic Rankine cycle for power generation (ORC), an absorption chiller for cooling (AC) and a thermal energy storage system (TES). The effects of solar collector dimension variations, system parameters, environmental conditions and system integration on system energy and exergy efficiencies are parametrically studied. The largest irreversibility occurs in solar collectors due to very high exergy input to solar panels and less conversion of exergy to working fluid. Energy and exergy efficiencies of the present system become 77.1 % and 27 % during day time and 37.6 % and 18.7 % during night time, respectively. The proposed system performs better performance at lower ambient temperature and higher solar radiation and PTC concentration ratio.

Exergy Analysis and Environmental Impact Assessment of Solar-Driven Heat Pump Drying Systems

Exergy and sustainability analysis and environmental impact assessment of drying processes are performed for conventional and solar-driven two-stage evaporator heat pump drying systems. Some parametric studies are also undertaken to investigate the influence of environmental and system parameters on the overall efficiencies. Greenhouse gas (GHG) emissions, for electricity generation are comparatively evaluated under various options. Coal-based generation has the highest emissions for both conventional and solar-driven drying systems and lowest emissions are observed for nuclear and solar photovoltaic based electricity generation. The results show that solar thermal integration to the heat pump drying system brings an additional 32 gCO2/kWh carbon dioxide emission due to production, transportation, maintenance, and disposal of the solar thermal system. However, GHG emissions from conventional HPD system are 20.4–34.1 % higher than those of solar-driven HPD system for different generation resources.

Thermodynamic analysis of an ice slurry thermal energy storage system for decreased size and cost of HVAC systems

Öz Performance assessment of a cold thermal energy storage (ITES – Ice Thermal Energy Storage) system with ice slurry generation for closed space air conditioning purposes is conducted. A detailed energy and exergy analysis are performed for the baseline system and some parametric studies are also presented for varying environmental conditions. Exergy definition is linked to sustainability and reported with graphical representations. A compressor & condenser unit linked to an ice slurry generator and generated ice is stored at storage tank for specific hours of a day. Stored energy is then discharged to the building through a flat-plate heat exchanger. Thermodynamic analysis results suggest that high capacity cooling can be conducted with low capacity vapor compression refrigeration systems (VCR) by integrating ITES systems, leading to a significantly lower size and lower cost HVAC systems. Bu çalışmada kapalı alanların iklimlendirilmesi için buz bulamaçı (ice slurry) üretimi yapan bir buz depolama (ITES-Ice Thermal Energy Storage) sisteminin performans değerlendirmesi yapılmıştır. Temel alınan model için detaylı bir enerji ve ekserji analizi yapılmış, değişen çevre ve sistem koşulları için parametrik çalışmalar rapor edilmiştir. Ekserji konsepti aynı zamanda sürdürülebilirlik ile bağıntılanarak grafiksel olarak sunulmuştur. Bir kompresör-kondenser ünitesi buz bulamaç üreteçine entegre edilmiş ve üretilen buz-glikol bulamaçı günün belirli saatlerinde depolanmıştır. Depolanan enerji daha sonra kapalı alana bir düz-plaka ısı değiştiricisi yardımıyla deşarje edilmektedir. Termodinamik analiz sonuçları, ITES yardımıyla düşük kapasiteli buhar sıkıştırmalı soğutma sistemleri ile yüksek kapasiteli soğutma yapılabileceğini göstermektedir ve bu entegrasyon düşük boyutlu ve düşük maliyetli iklimlendirme sistem kurulumuna öncülük etmektedir.

1.17 Geothermal Energy

This chapter focuses on geothermal energy, which is considered as one of the most abundant renewable energy resources with its wide availability throughout the world. In this regard, the chapter introduces some basic information about geothermal energy formation and potential as well as its uses. The chapter also discusses technical and environmental dimensions of energy, geothermal water composition and decomposition, direct and indirect use of geothermal energy sources and their applications in potentially attractive countries. A comprehensive thermodynamic analysis is presented for geothermal systems. Some examples and case studies are presented to introduce energy and exergy approaches accordingly for systems. World trends, as well as present and potential applications of geothermal energy use, are presented. Many configurations of geothermal energy transformations are presented, and several illustrative examples are performed to interpret the technical and thermodynamic aspects of geothermal energy transformation by defining energy and exergy efficiencies. The environmental and future aspects of geothermal energy use are also comprehensively discussed.

Energetic and Exergetic Performance Comparisons of Various Flow Sheet Options of Magnesium-Chlorine Cycle

During the past decade thermochemical and/or hybrid cycles using essentially heat (without/with some electricity) are preferred over conventional electrolysis where the electricity is the main energy input. Therefore, such cycles help significantly reduce the electrical work consumption by adapting some consecutive chemical reactions which utilize thermal energy at medium to low temperatures that can match with renewable and existing nuclear energy sources. The ideal magnesium-chlorine cycle consists of three steps, namely hydrolysis of MgCl2, chlorination of MgO, and electrolysis of HCl. In this particular study, we develop two newly proposed configurations to compare with the ideal version of this cycle. The first configuration uses an intermediate step through the hydrolysis reaction while a fourth step is introduced in the second configuration where HCl production is accomplished in dry form. Thermodynamic comparisons are carried out using energy and exergy analysis, and the four-step configuration practically shows the highest performance and can compete with the conventional splitting of water by electrolysis. In summary, the present options provide potential solutions for sustainable hydrogen production.

Comparative Thermodynamic Assessment of Various Super- and Trans-Critical Working Fluids for Low Temperature Power Generation Applications

Recently, energy need is exponentially increasing in the world while energy sources are decreasing rapidly. Therefore, this issue requires energy sources to be used more efficiently and urges professionals to utilize energy from low temperature energy sources such as waste heat and low temperature renewable sources. In this study, energy and exergy analyses of several clean working fluids are comparatively studied in several organic Rankine cycle configurations. CO 2 , N 2 O, and SF 6 fluids are compared with the conventional R23 in three ORC configurations, namely the basic ORC cycle, regenerative ORC cycle, and reheat and regenerative ORC cycle, respectively. Effects of various selected system and environmental parameters on the system performances are comprehensively investigated. Even though R23 shows the best energy and exergy performances than those of other investigated working fluids at low-temperature applications, N 2 O and CO 2 provide a clean solution to high GWP (global warming potential) R23 with similar performance characteristics at low and high temperature power generation applications.