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Publication Date: 2025
Applied Energy (03062619)
Borehole thermal energy storage systems are emerging as a promising technology for storing intermittent renewable thermal energy sources. BTES systems utilize the underground as a thermal reservoir, where heat is stored during periods of excess energy production and retrieved when needed. This enables these systems to address the challenge of matching the supply of renewable energy with the demand for heating and cooling in buildings. This approach not only enhances the efficiency of renewable energy systems but also contributes to reducing greenhouse gas emissions and reliance on fossil fuels. This study introduces a novel approach to literature analysis in the BTES field by employing bibliometric and qualitative analysis tools, including SciMAT, VOSviewer, and NVivo, providing a systematic alternative to traditional manual review methods. The goal is to identify key publications, summarize their findings, and track the evolution of research directions over time, enhancing the understanding of the field. The paper is structured into six sections. The first section provides an overview of analytical and numerical models used to simulate the performance of BTES systems. The second section discusses the differences between traditional literature review methods and those employing bibliometric and qualitative analysis tools, highlighting their respective limitations and benefits. Additionally, it compares studies that have analyzed the BTES field using traditional review methods, explaining why a literature review with bibliometric and qualitative analysis tools is necessary and what advantages they offer. The third section outlines the research structure and employs bibliometric metrics to identify significant publications in the BTES field, while the fourth section uses SciMAT, VOSViewer, and NVivo to create scientific maps and networks of keywords, documents, publication sources, and active countries, revealing major research themes and influential publications. The fifth section organizes BTES publications into seven groups, reviewing selected studies within each to highlight recent developments, while the final section evaluates the dispersion of these studies to pinpoint well-researched areas as well as areas that require further exploration within the BTES field. The study highlights a growing interest in BTES research and identifies gaps in areas such as regulatory frameworks, market status, environmental impacts, and integration with smart energy systems. It also emphasizes the need to further investigate the thermal effects of groundwater, grout, ground thermal properties, and ground temperature imbalances on BTES system performance, underscoring the importance of continued research to address challenges and advance the development of BTES systems. © 2025 Elsevier Ltd
Publication Date: 2025
International Journal of Hydrogen Energy (03603199)
To decrease carbon emissions in energy production systems, a new system has been introduced and investigated that utilizes solid oxide fuel cells (SOFC), a closed Bryton cycle (CBC), and a carbon dioxide capture unit (CCU). An extensive mathematical model has been created to evaluate the thermodynamic efficiency of this combined system. Findings show that the exergy efficiencies of the separate components, including SOFC and SOFC-CBC, are 39% and 79%, respectively, and the integrated system exhibits a total cost rate of 109.3 $/hr. The system is equipped with a CO2 capture unit, allowing it to efficiently separate the carbon dioxide produced during combustion and store it in a designated tank. The system is designed to effectively absorb 90% of carbon dioxide, successfully separating an impressive 221.94 kg/h. The exergy analysis of the system reveals that the afterburner has the greatest exergy destruction. Therefore, this component has the potential for system improvement from a thermodynamic perspective. Furthermore, a comprehensive study on the influence of the system's key parameters has been conducted to understand the system's performance. Maximum efficiency is realized when the SOFC functions at a temperature of 600 K with a fuel utilization ratio of 3.7. © 2025
Publication Date: 2025
Journal of Thermophysics and Heat Transfer (08878722) (1)
In general, for installing multilayer insulation (MLI) blankets on curved spacecraft equipment, creating a pattern that has multiple sectors is necessary because of the impossibility of establishing a single piece of MLI. The sector area of the MLI contains numerous seams and sewing. Therefore, prediction of overall performance or effective emittance is not simply possible, and they need to be tested in some experimental ways. The aim of the current research is to present a methodology for determining the conductivity between layers in both nonsewing and sewing regions of MLI to correctly estimate the effective emittance coefficient and the thermal behavior of MLI. Firstly, by conducting two experimental tests, both sewn and nonsewn square MLIs’ effective emittance coefficients are computed. In the second step, the conductive thermal coupling coefficients of nonsewing and sewing regions are determined as 1.615 and 1.95 W∕)m2 . K) respectively, utilizing experimental data. In the third step, a spherical geometry fuel tank is selected as a case study, and these coefficients are utilized in the simulation process of an MLI tank. Finally, the overall effective emittance coefficient of that tank is determined. The results indicate that the effective emittance is reduced by about 8%. © 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Parvanian A.M. ,
Baniasadi, E. ,
Lalpour A. ,
Lalpour, N. ,
Abanades S. Publication Date: 2025
Fuel (00162361)
This study explores the enhanced efficiency of solar-driven redox reactions using ceria foams coated with Ca-doped lanthanum manganite (LCM) perovskite, focusing on sustainable fuel production. The effects of substrate pore density (10, 30 ppi) and coating thickness (3 and 6 perovskite layers) were investigated. The LCM perovskite was synthesized and uniformly coated onto porous ceria substrates, as confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dual-scale porous structure of ceria enhanced the coating's effectiveness and reactivity, with coating thicknesses ranging from 75-140 μm (three layers) to 100–400 μm (six layers). Thermogravimetric analysis (TGA) showed superior reduction extents for LCM-coated ceria samples, with O2 production up to 131 µmol/g, compared to 55 µmol/g for pure ceria. This led to a 20–40 % increase in total fuel production, with CO yields up to 141 µmol/g versus 98 µmol/g for pure ceria. Performance stability for CO2 and H2O splitting was confirmed through fifteen consecutive cycles in a high-temperature solar reactor. Solar thermochemical cycling tests showed that LCM-coated ceria foams produced up to 244 µmol/g CO, with a peak CO production rate of 6.22 mL·min-1·g-1, during reduction at 1450 °C and oxidation under pure CO2 below 900 °C. However, pure ceria exhibited faster oxidation kinetics. This research underscores the importance of material design and optimization in improving solar thermochemical processes for large-scale solar fuel production. © 2025 Elsevier Ltd
Baniasadi, E. ,
Rezk A. ,
Batista, Luciano ,
Tola, Tetenayet Bekele ,
Alaswad, Abed Publication Date: 2025
Energy Conversion and Management (01968904)
This study develops and optimises a renewable-driven hybrid refrigeration system to enhance food preservation in off-grid rural areas. The system integrates solar photovoltaic, solar thermal collectors, wind energy, and battery storage to provide a sustainable, cost-effective cooling solution. A comprehensive techno-economic analysis was conducted using Ethiopia as a case study to evaluate system performance, cost-effectiveness, and market feasibility. The optimised system meets 22.42 kW of thermal power demand and 2.82 kW of electrical power demand, reducing daily operational costs from $100 to $86.2. Optimisation improved system efficiency by increasing photovoltaic panels to 15, reducing battery storage from 11 to 7 units, and optimising solar collector area to 322 m2. The length of underground thermal storage piping was reduced to 1366 m, enhancing thermal efficiency. The system achieved near off-grid operation, with grid dependency reduced from 9.3 W to 3.2 W and auxiliary heater reliance below 1 % of total demand. A business model incorporating subscription-based and lease-to-buy financing supports adoption by smallholder farmers and cooperatives, with a five-year payback period. Survey results indicate that 90 % of farmers lack cooling facilities, while 48 % of cooperatives favour government incentives. The system's environmental benefits include zero on-site (operational) CO2 emissions and eco-friendly refrigerants. This research demonstrates the feasibility of hybrid renewable energy integration in sustainable cold storage, reducing post-harvest losses and enhancing food supply chains in off-grid communities. Sensitivity analysis against inter-annual resource variability and ± 20 % capital-cost dispersion confirms the robustness of the optimised configuration. © 2025 The Author(s)
Publication Date: 2025
Journal of Energy Storage (2352152X)
This study employs the finite line source (FLS) method, a fully analytical model, to evaluate thermal interactions, heat loss, and heat storage rates of borehole thermal energy storage (BTES) systems. The proposed model provides rapid and accurate simulations, in contrast with existing methodologies that rely on time-consuming numerical models. The model first assesses the temperature distribution within and around the boundaries of the BTES. Using the determined temperatures, Fourier's law is applied to calculate heat losses, and the principle of energy conservation is used to determine the thermal energy stored within the BTES. To account for variations in heat exchange rates among boreholes and over time, the FLS solution is superposed both spatially and temporally, and a specific load aggregation technique is employed to reduce computational cost. Further computational efficiency is achieved by approximating the error function required for the FLS solution with a Gaussian Q-function and by using hierarchical agglomerative clustering to categorize boreholes with similar temperatures and heat exchange rates. The proposed method is validated through several case scenarios of increasing complexity and compared against the publicly known duct ground storage (DST) model and simulations conducted using COMSOL software. The results demonstrate the effectiveness of the FLS method in assessing thermal interactions, heat loss, and heat storage rates of different BTES configurations with regular or irregular borehole arrangements, as well as various series-parallel connections. It is also observed that approximating the FLS solution and categorizing boreholes into groups can significantly reduce calculation time, depending on the size and complexity of the problem. An application of the proposed method is also presented, wherein the borehole spacing and length of a BTES are optimized to minimize heat losses and maximize heat storage over time. A grid independence analysis revealed that most inaccuracies of the proposed method occur during the early operational stages, particularly in the evaluation of heat storage rates. These inaccuracies can be mitigated by increasing the radial, axial, and angular segments around boreholes and refining time intervals. Alternatively, inaccuracies can be reduced by evaluating heat storage rates by subtracting heat loss rates from heat exchange rates, similar to the approach used in the DST model. © 2025
Publication Date: 2024
Case Studies in Thermal Engineering (2214157X)
The increasing carbon footprint associated with conventional cooling methods underscores the urgent need for sustainable alternatives. This study investigates the economic and environmental advantages of various solar-thermal cooling systems, with a focus on optimizing their performance across different climate conditions. Employing a multi-objective approach, the research emphasizes exergy-economic indices to optimize selected cycles. The analysis covers multiple refrigeration technologies, including liquid absorption, solid adsorption, and solid desiccant cycles. Results indicate that the liquid absorption cycle performs optimally in hot, arid climates, reducing the payback period to approximately 8 years when optimized. In hot and humid regions, the solid desiccant cycle proves most effective due to its superior humidity control, yielding a payback period of 5.3 years. For cold and mountainous areas, the solid adsorption cycle is preferred, with a payback period of 13.5 years, while moderate and humid climates benefit from the solid desiccant cycle for both cooling and humidity regulation. The exergy-economic factors for the solar refrigeration systems across semi-arid, hot and arid, hot and humid, cold and mountainous, and moderate and humid climates are 0.758, 0.602, 0.698, 0.74, and 0.575, respectively. © 2024 The Authors
Publication Date: 2024
Energy (03605442)
Steel production is a highly energy-intensive industry, responsible for significant greenhouse gas emissions. Electrification of this sector is challenging, making green hydrogen technology a promising alternative. This research performs a thermodynamic analysis of green hydrogen production for steel manufacturing using the direct reduction method. Four solid oxide electrolyzer (SOE) modules replace the traditional reformer to produce 2.88 kg/s of hydrogen gas, serving as a reducing agent for iron pellets to yield 30 kg/s of molten steel. These modules are powered by 37,801 photovoltaic units. Additionally, a thermal storage system utilizing 1342 tons of steel slag stores waste heat from Electric Arc Furnace (EAF) exhaust gases. This stored energy preheats iron scraps charged into the EAF, reducing energy consumption by 5 %. A life cycle assessment, conducted using open LCA software, reveals that the global warming potential (GWP) for the entire process, with a capacity of 30 kg/s, equates to 93 kg of CO2. The study also assesses other environmental impacts such as acidification potential, ozone formation, fine particle formation, and human toxicity. Results indicate that the EAF significantly contributes to global warming and fine particle formation, while the direct reduction process notably impacts ozone formation and acidification potential. © 2024 The Authors
Baniasadi, E. ,
Rezk A. ,
Tola, Yetenayet Bekele ,
Alaswad, Abed ,
Imran, Muhammad Publication Date: 2024
Energy Conversion and Management (01968904)
This study presents a new method for sustainable cooling systems using a hybrid refrigeration system powered by hybrid renewable energy sources. The system comprises a modular unit of vertical wind turbines integrated with bio-photovoltaic films to provide sustainable energy. The hybrid refrigeration system combines evaporative and solar thermal-driven adsorption cooling systems. In addition, a finite volume of soil is proposed for thermal energy storage. Experimental data inform the development of a digital twin for an integrated system, soil thermophysical characteristics, wind turbine performance, and technical specifications for other system components. This sustainable cooling package is cost-effective and space-efficient, particularly in remote or off-grid locations. Notably, the evaporative cooler and chilled water coil contribute to a cooling effect of 20.4 kW, and solar power generation reaches 12.38 kW at an intensity of 1053 W/m2. The annual electrical output averages 1.7 kW at a wind speed of 3.5 m/s. Under best conditions, wind power can surge to 7.99 kW at 9.88 m/s. The ratio of power generated by wind to solar energy ranges from 1.1 to 1.3. The system effectively meets a peak thermal energy demand of approximately 74 GJ/month, facilitated by solar collectors, underground thermal storage, and a renewable energy-fed auxiliary heater. This study paves the way for future techno-economic optimisation and advancements in sustainable energy solutions for remote cold storage facilities. © 2024 The Author(s)
Publication Date: 2024
International Journal of Hydrogen Energy (03603199)
Due to the widespread use of multi-generation systems utilizing renewable energy sources and the growing global demand for such systems from both economic and environmental considerations, numerous researchers have focused on the design and evaluation of their performance. To this end, this research presents a biomass-based multi-generation system with an innovative and practical design that can generate electricity, heat, and hydrogen. This system includes a modified gas turbine cycle, a supercritical CO2 (SCO2) cycle, a transcritical CO2 (TCO2) cycle, a proton exchange membrane (PEM) electrolyzer, and a PEM fuel cell unit. This study aims to evaluate the impact of various biomass sources (paper, wood, paddy husk, and municipal solid waste) on the system performance. The proposed system has been analyzed using the first and second laws of thermodynamics. This system uses the maximum capacity to produce power, heat and hydrogen. A fuel cell unit has been used to consume hydrogen and generate more electricity. In the basic mode, the system has energy and exergy efficiencies of 47.89% and 32.26%, respectively, and can produce 2.74 kg/h of hydrogen. The biomass fuel consumption rate within the system is 0.055 kg/s. The overall exergy destruction of the system amounts to 1240 kW, with the biomass boiler and the condenser being the components that experience the greatest exergy destruction, registering values of 535.5 kW and 432.3 kW, respectively. Notably, employing municipal waste as biomass increases the system's exergy efficiency to 33.16%. © 2024
Publication Date: 2023
Applied Thermal Engineering (13594311)
In this paper, the performance of solar-thermal cooling systems for air conditioning application is investigated in different climates of Iran. Diverse climate types are considered which makes the results applicable to other countries. Available commercial refrigeration cycles that are capable of integration with solar-thermal collector systems including the closed liquid absorption cycle, closed solid adsorption cycle, and desiccant cycle are studied. First, a solar and climatic map is proposed and the representative cities have been selected for each climate. Then, the climate parameters related to each region are extracted to create an hourly database. Also, the cooling load of a reference building is modeled based on the climate database, each refrigeration cycle is simulated using thermodynamic equations, and the dynamic model is generalized daily for the hot season in each city. In the last step, each cooling system is examined using an exergy-economic analysis, and technical and economic indicators are compared. The results show that the most suitable solar-thermal refrigeration cycle that can be installed in the central plateau and semi-arid areas of Iran is the closed-cycle liquid absorption system. The annual average exergy-economic factor and the annual solar fraction in this cycle are 0.7578 and 0.57, respectively. In the southern coastal areas, due to the high humidity and air temperature in summer, the solid desiccant refrigeration system with an exergy-economic factor of 0.6978 and a solar fraction of 0.2416 is preferred. The suitable solar-thermal refrigeration cycle in the cold and mountainous regions of Iran is a solid adsorption system with a silica gel absorber. The annual solar fraction and average annual exergy-economic factor in this cycle are 0.5158 and 0.7394. Also, in northern moderate regions, the solid adsorption refrigeration system with an average annual exergy-economic factor of 0.409 and average exergy efficiency of 0.12 is comparatively beneficial. © 2023 Elsevier Ltd
Publication Date: 2023
Green Energy and Resources (29497205) (4)
Energy storage is a crucial solution for the intermittency and instability of renewable energy. Carnot batteries, a novel electrical energy storage technology, promise to address the challenges of renewable electrical energy storage worldwide. Rankine-based Carnot batteries, which are geographically unconstrained and effectively store energy at low temperatures, have attracted considerable attention in recent years. In this study, a mathematical model was developed, and a multi-objective optimization with power-to-power-efficiency, exergy efficiency, and levelized cost of storage was performed. Moreover, the investment cost and exergy loss of the optimized system components were investigated in detail and analyzed. The results showed that the optimal power-to-power-efficiency, exergy efficiency, and levelized cost of the storage system can be achieved at 60.3%, 33%, and 0.373 $/kWh based on single-objective optimization, and the operating parameters of the proposed system are different. Therefore, there is a strong trade-off relationship between the three objective functions mentioned above. Under the same weighting for the two approaches, they are 25.8%, 23%, and 0.437 $/kWh, and 39.3%, 29.1%, and 0.549 $/kWh, respectively. Furthermore, this study observed that the exergy destruction in the charge mode was nearly 95 kW larger than that in the discharge mode, and the exergy destruction of the throttle valve was the largest at 95.83 kW, accounting for 28.32%. The expander was the component with the highest cost (35.84% of the total cost) in the proposed system, followed by the compressor. © 2023 The Author(s)
Publication Date: 2019
Journal of Energy Storage (2352152X)
Phase Change Materials (PCM) have been widely used in different applications. PCM is recognized as one of the most promising materials to store solar thermal energy in the form of latent heat. Utilization of PCMs for solar energy storage compensates for the intermittent characteristic of this energy source. Mathematical modeling and numerical simulation of solar energy storage systems provide useful information for researchers to design and perform experiments with a considerable saving in time and investment. This paper is focused on modeling and simulation of PCM based systems that are used in different solar energy storage applications. A thorough literature review is performed to investigate and compare the results and accuracy of different mathematical models, numerical methods and thermodynamic analysis of using different PCMs in different solar systems. Moreover, the potential research areas in numerical simulations and thermodynamic analysis of solar systems based on PCMs are determined considering the existing gaps in the literature. Although the main idea of using PCMs is storing thermal energy for different applications, PCMs can be used for other purposes such as cooling photovoltaic panels. Past studies have shown that utilization of PCMs in photovoltaic panels can improve the performance of panels by decreasing the average panel temperature by 9.7%. The results of simulations also showed that for each climate a specific PCM with a melting temperature should be used to reach the most uniform temperature distribution. © 2018 Elsevier Ltd
Publication Date: 2019
International Journal of Exergy (17428297) (1)
In this paper, energy, exergy and exergoeconomic analyses of a solar absorption refrigeration cycle with energy storage are conducted. In this cycle, nanofluid is used as the heat transfer fluid (HTF) in a flat plate collector to improve the performance of the cycle. Based on the results of the analyses, the type of nanofluid and working conditions that lead to lower cost of cooling effect and higher COP and exergy efficiency of the cycle are found. The results show that utilisation of CuO and Al2O3 nanofluids with 5% volume fraction increases the COP of the solar cycle by 17.98% and 14.51%, respectively, whereas the exergy-based cost rate of cooling decreases by 10.25% and 5.48%, respectively. Utilisation of the CuO nanofluid as the HTF is found to be more favourable for improving the performance of the cycle and decreasing the exergy-based cost of cooling. © 2019 Inderscience Enterprises Ltd.
Publication Date: 2019
Applied Thermal Engineering (13594311)
Cold energy storage during the off-peak hours to supply the cooling demand during the peak hours leads to reduction of the chiller size and energy expenses. In this paper, the performance of an ice bank system based on spherical capsules is experimentally analyzed and the effects of different parameters are investigated using a numerical model. The numerical simulation is performed for optimum design of the energy storage system and the results of numerical simulation are validated against the experimental data. Moreover, temperature distribution inside the ice bank is evaluated, experimentally and numerically, and heat transfer rate from the spherical capsules wall and the liquid fraction inside these spherical capsules are determined using numerical simulations during the charge and discharge processes. The results indicate that utilization of two inlets for heat transfer fluid (HTF) leads to decrease of charging time by 11 min and increase of the efficiency by 37%. Moreover, the best efficiency during the charge and discharge modes are 77% and 51% using 0.04 kg/s mass flow rate, respectively. Furthermore, the results showed that when the capacity of the system increases by increase of spherical capsules from 60 to 120, the system efficiency during the charge and discharge processes increase by 26% and 23%, respectively. © 2018 Elsevier Ltd
Mesforoush H. ,
Pakmanesh, M.R. ,
Esfandiary, H. ,
Asghari, S. ,
Baniasadi, E. Publication Date: 2019
Cryogenics (00112275)
Multi-layer insulation (MLI) blankets are one of the main components of satellite thermal control system. The past studies have considered infinite heat transfer coefficient in modeling the MLI shields due to the use of reflective thin films such as aluminized Kapton (Polyimide Film Developed by DuPont Company) or aluminized PET (Polyethylene Terephthalate) in MLI shields. Therefore, equal temperature was considered on two sides of a shield and the effect of thermal resistance has been ignored in the total thermal resistance. In the present study, the effects of thermal conductivity of thin film and shield thickness are analyzed. For this purpose, numerical analyses are performed on three types of blankets that are made of Kapton, PET and null shields. The results indicate that the difference in effective emittance of Kapton and PET blanket is 17% to 2% from the thinnest film to the thickest film, respectively. In order to confirm the numerical results, the effective emittance of two types of MLI blankets made of Kapton and PET films is measured under identical conditions. It is concluded that the Kapton blanket has lower effective emittance than PET. © 2019 Elsevier Ltd
Publication Date: 2017
Renewable Energy (09601481)
This paper presents a novel process for high efficiency production of hydrogen and desalination of brine water based on the concept of solar spectrum splitting. The advantage of this system is concurrent production of hydrogen and distilled water using a sustainable process at large scale. The harvested energy from the separated solar spectral bands is used to supply the required energy for high temperature steam electrolysis and a double-stage flash distillation system. The integrated solar system is designed to reduce the energy conversion deficiencies, considerably. In order to investigate the performance of this system, a process simulation code is developed. An exergy analysis is conducted and the economic feasibility of the plant is evaluated. The sensitivity of the integrated cycle performance on solar insolation, electrolyzer temperature, and pressure is analyzed, and the results indicate that utilization of concentrator cells, with a multi-band gap mirror can increase the productivity of the cycle, drastically. It is observed that hydrogen and distilled water production rate can be increased by more than 1.6 times, when the harvested solar power increases from 28 MW to 55 MW. It is concluded that the maximum energy and exergy efficiencies of the integrated solar cycle is about 45%. © 2016 Elsevier Ltd
Publication Date: 2017
International Gas Research Conference Proceedings (07365721)
The energy consumption, investment cost and operation cost of natural gas transmission pipelines can be optimized using the novel fabrication methods of producing higher strength and lower weight raw materials. Utilization of methods for producing steel with fine-grained structure to improve the weldability and formability characteristics of pipe material and to decrease the pipe thickness can lead to considerable saving in pipeline capital investment. An optimum design of transmission and distribution pipelines is investigated from the technical and economic aspects. The optimization method is presented to minimize the lifetime cost of natural gas transmission pipelines. All design parameters including thickness, grade, flow rate and working pressure are considered. The objective function is the total lifetime cost of a gas transmission system that includes investment and operation costs. All the technical and economic constraints are modeled as a mathematical function using a programming language. Optimization results is highly sensitive to pipeline class location and construction standards.
Publication Date: 2017
Renewable Energy (09601481)
In this study, the performance of a forced convection mixed-mode solar dryer with thermal energy storage is experimentally analyzed. The main goal was to develop an efficient and cost effective dryer that maintains drying process after sunset. The dryer mainly consists of a solar collector/absorber, drying chamber and a fan. A photovoltaic panel and battery storage are also integrated with the dryer to supply the required electrical energy. The experiments are carried out to dry fresh apricot slices at different working conditions. The effect of using phase change material to store thermal energy during daytime is analyzed. It is concluded that the performance of the solar collector is improved and the drying process is effectively extended when solar energy was not available. It is also observed that the rate of drying is almost constant along the drying chamber. The moisture pick-up efficiency and the overall thermal efficiency of the dryer are about 10% and 11%, respectively. © 2017 Elsevier Ltd
Publication Date: 2014
Solar Energy (0038092X)
In this paper a scale-up analysis of a dual cell photo reactor based on a kinetic, radiation model and mass balance of reactants is presented. A kinetic model that includes phenomenological based parameters is developed to evaluate the reaction rate under operational conditions of a photo-reactor. The analysis is performed for six different scale-up ratios with three different constraints for each case. With a constraint of pre-determined length to diameter ratio factor, a lower enhancement in productivity can be achieved at higher light intensities. The analysis is followed by an exergoeconomic study in which two case scenarios of a hydrogen production plant with and without oxygen production for three different production capacities are considered. It reveals the maximum hydrogen exergy price of 2.2, 0.88, and 0.51kg-1 for production capacities of 1, 100, and 2000tonday-1, respectively. © 2014 Elsevier Ltd.
Publication Date: 2013
Engineering Applications of Computational Fluid Mechanics (19942060) (1)
In this paper, a CFD study of two types of axial-flow automotive cooling fans was conducted to investigate the effects of upstream and downstream blockage on aerodynamic performance of each fan. The realizable k-ε turbulence model was applied and simulations were performed to represent an automotive engine bay and quantify performance changes as a function of blockage distance. Modeling was performed for two fan designs: one optimized for a low flow rate, high-pressure operation; and a second optimized for high flow rate, low-pressure operation. The results show that the pressure loss caused by engine blockage increases at higher vehicle speed, and decreasing blockage distance. A new relation between blockage to fan proximity and fan performance was established. It is determined that the pressure change follows a quadratic type dependence, but the coefficients may vary, depending on fan type. The fan efficiency can be improved by taking advantage of larger blockage distances at higher speeds of the vehicle. The blockage condition causes an increase in the reverse flow near the fan interface, and a dramatic increase in radial flow. © 2013 Taylor and Francis Group LLC.
Publication Date: 2013
International Journal of Hydrogen Energy (03603199) (6)
In this paper, a new seawater electrolysis technique to produce hydrogen is developed and analysed thermodynamically. Although hydrogen production occurs at high columbic efficiency, it causes a localized pH change. It leads to a higher cell voltage and solid deposition as significant challenges of seawater electrolysis. In this regard, the anolyte feed after oxygen evolution to the cathode compartment for hydrogen production is examined. The study aims to prevent the occurrence of a large pH difference on the cathode and anode in the electrolysis of a neutral solution if sufficient OH- ions are permeated through the membrane. The cell performance is evaluated with an anion exchange membrane for separation of the anode and cathode compartments. An inexpensive and efficient molybdenum-oxo catalyst with a turn-over frequency of 1200 is examined for the hydrogen evolving reaction. The flow rate and current density are parametrically studied to determine the effects on both bulk and surface precipitate formation. The effect of electrolyte circulation on the amount of precipitation is predicted based on a mass transfer approach. The mixing electrolyte volume and electrolyte flow rate are found to be significant parameters as they affect cathodic precipitation. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Publication Date: 2013
Applied Catalysis A: General (0926860X)
In this paper, an experimental study of photo-catalytic water splitting with cadmium sulfide and zinc sulfide photo-catalysts is performed in a dual-cell reactor to investigate the effects of radiation intensity and photo-catalyst concentration on hydrogen and oxygen production rates. Hybridization of the photo-catalytic process is examined with multi catalysts and electric potential bias to enhance the productivity of the reactor and sustain the reaction rate. The hydrogen production of 0.41 mmol h-1 with 0.75% (v/v) ZnS is improved by almost 2 times higher than past studies due to illumination of 0.2% (v/v) CdS under 1 sun in a hybrid reactor. The productivity of the reactor is significantly enhanced at light intensities more than 1000 W m-2. The cadmium sulfide catalyst is found to be an inefficient absorbent of light energy, but it shows higher energy and exergy efficiencies compared with ZnS photo-catalysts in a light-driven water splitting process. © 2013 Elsevier B.V. All rights reserved.
Publication Date: 2013
International Journal of Hydrogen Energy (03603199) (22)
In this paper, an experimental study is performed for hydrogen and oxygen production by new photo-catalytic and electro-catalytic water splitting systems. An effective method for hydrogen production by solar energy without consumption of additional reactants is a hybrid system which combines photo-chemical and electro-catalytic reactions. Experiments are performed in batch and dual cell quasi-steady operation with different light intensities and zinc sulfide photo-catalyst concentrations. The photo-reactor in batch operation achieves 6 mL h-1 of hydrogen production with 3% w/v of catalyst. The hydrogen production rate corresponds to a quantum efficiency of 75% as measured through illumination of zinc sulfide suspensions in a dual cell reactor. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Publication Date: 2013
International Journal of Hydrogen Energy (03603199) (14)
This paper examines the oxygen evolving reaction of water splitting under practical conditions which simulate those encountered in photo-initiated or electrochemical water oxidation processes. Most of the over-potentials are due to electrochemical processes at the anode, where oxygen evolution occurs. This paper investigates the oxygen evolving half cells for different complete systems including photoelectrochemical, photo-catalytic and electro-catalytic water splitting. An electrochemical model is developed to evaluate the over-potential losses in the oxygen evolving reaction and the effects of key parameters are analyzed. The transient diffusion of hydroxide ions through the membrane and bulk electrolyte are modeled and simulated for improved system operation. The results of the thermodynamic and electrochemical analyses show that for each water splitting configuration, there are optimal values of the operating parameters such as electrolyte concentration, current density, and membrane-electrode distance. The operating criteria of key parameters and the optimal working region of the oxygen evolving reactor are examined for assessment and optimization of a complete water splitting system. The analysis of the oxygen evolving reaction is performed for three variations of ruthenium based supramolecular complexes and molybdenum-oxo catalysts for catalytic hydrogen production. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Publication Date: 2012
Fuel Cells (16156854) (4)
An exergoeconomic study of an ammonia-fed solid oxide fuel cell (SOFC) based combined system for transportation applications is presented in this paper. The relations between capital costs and thermodynamic losses for the system components are investigated. The exergoeconomic analysis includes the SOFC stack and system components, including the compressor, microturbine, pressure regulator, and heat exchangers. A parametric study is also conducted to investigate the system performance and costs of the components, depending on the operating temperature, exhaust temperature, and fuel utilization ratio. A parametric study is performed to show how the ratio of the thermodynamic loss rate to capital cost changes with operating parameters. For the devices and the overall system, some practical correlations are introduced to relate the capital cost and total exergy loss. The ratio of exergy consumption to capital cost is found to be strongly dependent on the current density and stack temperature, but less affected by the fuel utilization ratio. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Publication Date: 2012
International Journal of Hydrogen Energy (03603199) (9)
In this paper, a new hybrid system for hydrogen production via solar energy is developed and analyzed. In order to decompose water into hydrogen and oxygen without the net consumption of additional reactants, a steady stream of reacting materials must be maintained in consecutive reaction processes, to avoid reactant replenishment or additional energy input to facilitate the reaction. The system comprises two reactors, which are connected through a proton conducting membrane. Oxidative and reductive quenching pathways are developed for the water reduction and oxidation reactions. Supramolecular complexes [{(bpy)2Ru(dpp)}2RhBr2] (PF 6)5 are employed as the photo-catalysts, and an external electric power supply is used to enhance the photochemical reaction. A light driven proton pump is used to increase the photochemical efficiency of both O2 and H2 production reactions. The energy and exergy efficiencies at a system level are analyzed and discussed. The maximum energy conversion of the system can be improved up to 14% by incorporating design modification that yield a corresponding 25% improvement in the exergy efficiency. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Publication Date: 2012
Chemical Engineering Science (00092509)
In this paper, a photocatalytic water-splitting system is designed and analyzed for continuous operation at a large pilot-plant scale. Performance of the photocatalyst and reaction system is discussed, as well as photon transfer and mass transfer limitations (in the case of liquid phase reactions). The optimization of these two processes is a main objective of this study. The system uses an external power source and two electrodes immersed in the catalyst solution to supply and transfer electrons inside two reactors to replace the need for electron acceptors and donors. A nano-filtration membrane, which is utilized to separate hydrogen and oxygen in the reactor, retains the catalyst on the cathode side while allowing passage of other species to the other half cell. A Compound Parabolic Concentrator (CPC) is presented for the sunlight-driven hydrogen production system. Energy and exergy analyses and related parametric studies are performed, and the effect of various parameters are analyzed, including catalyst concentration, flow velocity, light intensity, catalyst absorptivity, and ambient temperature. © 2012 Elsevier Ltd.
Publication Date: 2011
International Journal of Hydrogen Energy (03603199) (17)
In this study, both energetic and exergetic performances of a combined heat and power (CHP) system for vehicular applications are evaluated. This system proposes ammonia-fed solid oxide fuel cells based on proton conducting electrolyte (SOFC-H+) with a heat recovery option. Fuel consumption of combined fuel cell and energy storage system is investigated for several cases. The performance of the portable SOFC system is studied in a wide range of the cell's average current densities and fuel utilization ratios. Considering a heat recovery option, the system exergy efficiency is calculated to be 60-90% as a function of current density, whereas energy efficiency varies between 60 and 40%, respectively. The largest exergy destructions take place in the SOFC stack, micro-turbine, and first heat exchanger. The entropy generation rate in the CHP system shows a 25% decrease for every 100 °C increase in average operating temperature. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Publication Date: 2010
International Journal of Hydrogen Energy (03603199) (17)
Today's concern regarding limited fossil fuel resources and their contribution to environmental pollution have changed the general trend to utilization of high efficiency power generation facilities like fuel cells. According to annual reducing capital cost of these utilities, their entrance to commercial level is completely expected. Hot exhaust gases of Solid Oxide Fuel Cells (SOFC) are potentially applicable in heat recovery systems. In the present research, a SOFC with the capacity of 215 kW has been combined with a recovery cycle for the sake of simultaneous of electric power, cooling load and domestic hot water demand of a hotel with 4600 m2 area. This case study has been evaluated by energy and exergy analysis regarding exergy loss and second law efficiency in each component. The effect of fuel and air flow rate and also current density as controlling parameters of fuel cell performance have been studied and visual software for energy-exergy analysis and parametric study has been developed. At the end, an economic study of simultaneous energy generation and recovery cycle in comparison with common residential power and energy systems has been done. General results show that based on fuel lower heating value, the maximum efficiency of 83 percent for simultaneous energy generation and heat recovery cycle can be achieved. This efficiency is related to typical climate condition of July in the afternoon, while all the electrical energy, cooling load and 40 percent of hot water demand could be provided by this cycle. About 49 percent of input exergy can be efficiently recovered for energy requirements of building. Generator in absorption chiller and SOFC are the most destructive components of exergy in this system. © 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
In this entry, photo-reactors for catalytic solar hydrogen production are introduced and explained. To be an economical environmentally benign and sustainable pathway, hydrogen should be produced from a renewable energy source, i.e., solar energy. Solar driven water splitting combines several attractive features for sustainable energy utilization. The conversion of solar energy to a type of storable energy has crucial importance. In the first part of the entry, background information is presented regarding different photo-reactor configurations for water dissociation with light energy to generate hydrogen. The photo-electrochemistry of water splitting is discussed, as well as photo-catalytic reaction mechanisms. The design and scale-up of photo-reactors for photo-catalytic water splitting are explained by classification of light-based hydrogen production systems. At the end, a new photo-catalytic energy conversion system is analyzed for continuous production of hydrogen at a pilot-plant scale. Two methods of photo-catalytic water splitting and solar methanol steam reforming are investigated as two potential solar-based methods of catalytic hydrogen production. The exergy efficiency, exergy destruction, environmental impact, and sustainability index are investigated for these systems. The light intensity is found to be one of the key parameters in design and optimization of the photo-reactors, in conjunction with light absorptivity of the catalyst. © Springer Science+Business Media New York 2013. All rights reserved.
In this paper, an exergy-economic model is developed to analyze the performance of a direct steam solar tower - steam turbine - organic Rankine cycle (ORC) power plant under different working conditions. The solar power plant is connected to a power grid, and it is integrated with a hydrogen storage system. The hydrogen storage system is composed of an electrolyser, fuel cell, steam turbine and organic Rankine cycle. When solar energy is not available, electrical power is generated by the fuel cell, steam turbine and ORC using the hydrogen produced by the electrolyzer. The analyses are made for the maximum solar irradiation that is available in the city of YAZD in Iran. The effects of the current density and operating temperature on the performance of the solid oxide electrolyzer cell (SOEC) and solid oxide fuel cell (SOFC) are investigated. The effect of solar irradiation on the energy and exergy efficiencies of the cycle is investigated. The results indicate that increase of the solar irradiation leads to an increase of the energy and exergy efficiencies of the cycle. The solar tower has the highest exergy destruction and capital investment cost. © 2022 Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2. All rights reserved.
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