Energy and exergy analyses of hydrogen production step in boron based thermochemical cycle for hydrogen production

WOS: 000395842000059This study deals with a thermodynamic assessment of hydrogen production step of the boron based thermochemical cycle. In addition, this step is assessed for its merits and demerits in terms of energetic and exergetic performances for various reference environment temperatures. In this regard, the energy and exergy efficiencies of this step are calculated as 11.00% and 20.34% and also the hydrogen production step of the cycle inlet, outlet exergy rates and exergy destruction are calculated as 1653.32 kJ/mol, 336.31 kJ/mol and 317.02 kJ/mol while the reference environment temperature is kept constant at 298 K, respectively. The technical and economic problems of the hydrogen storage and transportation find a possible solution provided that the hydrogen production step of this cycle is performed on-board of a vehicle. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Energy and exergy analyses of integrated hydrogen production system using high temperature steam electrolysis

6th International Conference on Progress in Hydrogen Production and Applications (ICH2P) -- MAY 03-06, 2015 -- Oshawa, CANADAWOS: 000376695800033In this study, thermodynamic performance assessment of solar-driven integrated HTSE for hydrogen production is discussed in detail. The system consists of a solar tower, Brayton cycle, Rankine cycle, organic Rankine cycle (ORC) and high temperature steam electrolysis (HTSE). The required heat energy for power generation cycles are supplied from solar energy while produced electricity is used for the necessary energy demand of HTSE. For the analyses, the inlet and outlet energy and exergy rates of all subsystems are calculated and illustrated accordingly. From the results of the analyses, the overall energy and exergy efficiencies of the considered system are found to be 24.79% and 22.36% for power generation section and 87% and 88% for hydrogen production section respectively. Also it is found that without any auxiliary equipment, the considered hydrogen production process consumes 1.98 kWh(e) at 230 degrees C, generates 0.057 kg/s H-2. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved

Performance assessment of a geothermally heated building

WOS: 000264645300032This study deals with an exergetic performance evaluation of a geothermally heated building. This building used in the analysis has a volume of 1147.03 m(3) and a net floor area of 95.59 m(2), while indoor and exterior air temperatures are 20 and 0 degrees C, respectively. The geothermal heating system used for the heat production was constructed in the Ozkilcik heating center, Izmir, Turkey. Thermal water has a pressure of 6.8 bar, a temperature of 122 degrees C and a mass flow rate of 54.73 kg/s, while it is reinjected at 3.2 bar and 72 degrees C. The system investigated feeds three regions. Among these, the Ozkanlar region has supply/return pressure and temperature values of 4.6/3 bar and 80/60 degrees C, respectively. Energy and exergy flows are studied to quantify and illustrate exergy destructions in the overall system. Total exergy input rate to the system is found to be 9.92 kW and the largest exergy destruction rate occurs in the primary energy transformation at 3.85 kW. (C) 2008 Elsevier Ltd. All rights reserved

Development of sustainable energy options for buildings in a sustainable society

WOS: 000209553300003In this study, a building with a volume of 392 m(3) and a net floor area of 140 m(2) is considered as a case study with the indoor and exterior air temperatures of 20 degrees C and -15 degrees C, respectively. For heating applications, seven options are studied, namely (i) electric boiler, (ii) cogeneration, (iii) biomass/wood, (iv) ground heat pump water-water (v) heat pump borehole/glycol, (vi) standard boiler and (vii) solar collector as driven by renewable and non-renewable energy sources. Energy and exergy analyses are conducted to assess their performances and compare them through energy and exergy efficiencies and sustainability index. Energy and exergy flows are studied and illustrated accordingly. Also, the energetic and exergetic renewability ratios are employed here along with sustainability index. The results show that overall exergy efficiencies of heating systems are found to be 2.8%, 5.5%, 6.0%, 6.4%, 6.1%, 5.4% and 25.3%, while the sustainability index values for the seven cases considered are calculated to be 1.029, 1.058, 1.063, 1.069, 1.065, 1.057 and 1.338 for options 1 through 7, respectively. So, solar collector-based heating system gives the highest efficiency and sustainability index values. (C) 2011 Elsevier B.V. All rights reserved.Aksaray University; Ege University; University of Ontario Institute of Technology; Natural Sciences and Engineering Research Council of CanadaThe authors gratefully acknowledge the support provided by Aksaray University, Ege University and University of Ontario Institute of Technology, as well as the Natural Sciences and Engineering Research Council of Canada

Evaluating a low exergy heating system from the power plant through the heat pump to the building envelope

WOS: 000258768700003This study deals with an exergetic analysis and assessment of a low exergy heating system from the power plant through the ground-source heat pump to the building envelope. The methodology used is based on a pre-design analysis tool, which has been produced during ongoing work for the International Energy Agency (IEA) formed within the Energy Conservation in Buildings and Community Systems Programme (ECBCSP) Annex 37 to increase the understanding of exergy flows in buildings and to be able to find possibilities for further improvements in energy utilization in buildings. The analysis is applied to a room with a volume of 105 m(3) and a net floor area of 35 m(2) as an application place, while indoor and exterior air temperatures are 20 degrees C and -15 degrees C, respectively. The heat pump system used for heat production with a maximum supply temperature of 55 degrees C was designed, constructed and tested in Aksaray University, Aksaray, Turkey. In this context, energy and exergy flows were investigated, while exergy destructions in the overall system were quantified and illustrated. Total exergy input of the system was found to be 7.93 kW and the largest exergy destruction occurred in the primary energy transformation at 5.31 kW. (C) 2008 Elsevier B.V. All rights reserved.Scientific & Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)The authors gratefully acknowledge the valuable comments of the reviewers due to their contribution to the paper, while they also would like to thank the Scientific & Technological Research Council of Turkey (TUBITAK) for the incentive support given

Geothermal-based hydrogen production using thermochemical and hybrid cycles: A review and analysis

WOS: 000279971000002Geothermal-based hydrogen production, which basically uses geothermal energy for hydrogen production, appears to be an environmentally conscious and sustainable option for the countries with abundant geothermal energy resources. In this study, four potential methods are identified and proposed for geothermal-based hydrogen production. namely: (i) direct production of hydrogen from the geothermal steam, (ii) through conventional water electrolysis using the electricity generated through geothermal power plant, (iii) by using both geothermal heat and electricity for high temperature steam electrolysis and/or hybrid processes. and (iv) by using the heat available from geothermal resource in thermochemical processes. Nowadays, most researches are focused on high-temperature electrolysis and thermochemical processes. Here we essentially discuss some potential low-temperature thermochemical and hybrid cycles for geothermal-based hydrogen production. due to their wider practicality, and examine them as a sustainable option for hydrogen production using geothermal heat. We also assess their thermodynamic performance through energy and exergy efficiencies. The results show that these cycles have good potential and attractive overall system efficiencies over 50% based on a complete reaction approach. The copper-chlorine cycle is identified as a highly promising cycle for geothermal-hydrogen production. Copyright (C) 2009 John Wiley & Sons, Ltd.Ege UniversityEge University; Aksaray UniversityAksaray University; University of Ontario Institute of Technology; Natural Sciences and Engineering Research Council of CanadaNatural Sciences and Engineering Research Council of CanadaThe authors gratefully acknowledge the support provided by Ege University, Aksaray University, University of Ontario Institute of Technology and the Natural Sciences and Engineering Research Council of Canada. They would also like to thank the reviewers for their invaluable comments, which helped to improve the quality of the paper

Performance assessment of solar-driven integrated Mg-Cl cycle for hydrogen production

WOS: 000347017200092The present study develops a new solar energy system integrated with a Mg-Cl thermochemical cycle for hydrogen production and analyzes it both energetically and exergetically for efficiency assessment. The solar based integrated Mg-Cl cycle system considered here consists of five subsystems, such as: (i) heliostat field subsystem, (ii) central receiver subsystem, (iii) steam generation subsystem, (iv) conventional power cycle subsystem and (v) Mg-Cl subsystem. Also, the inlet and outlet energy and exergy rates of all of subsystems are calculated and illustrated accordingly. We also undertake a parametric study to investigate how the overall system performance is affected by the reference environment temperature and operating conditions. As a result, the overall energy and exergy efficiencies of the considered system are found to be 18.18% and 19.15%, respectively. The results show that the Mg-Cl cycle has good potential and attractive overall cycle efficiencies over 50%. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Aksaray University; University of Ontario Institute of Technology; Yasar UniversityThe authors gratefully acknowledge the support provided by Aksaray University, University of Ontario Institute of Technology and Yasar University