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A pressurized gasification combined system is studied in a novel integration with geothermal energy to produce hydrogen-enriched syngas. This system utilizes dewatered sludge, which leaves the biological wastewater treatment facility during the wastewater treatment process and is used as a feedstock to produce hydrogen as a useful output. The hydrogen produced is transformed in a proton-exchange fuel cell to electricity for community use. This system also incorporates a wind farm with a hydrogen storage system to meet societies' energy need when the energy demand fluctuates. The integrated system is then analyzed with thermodynamic-based energy and exergy approaches. The Greater Toronto area is chosen as the case study location and comprehensive thermodynamic analysis and simulation are completed on the Aspen Plus and Engineering Equation Solver softwares while the annual wind speed data are obtained from the RETScreen software. The daily total energy delivered to the community from this proposed system is recorded to be 2.1 GWh. In addition, the hydrogen production ratio at the gasification system is observed to be 0.12 through the sludge utilization where the energy and exergy efficiencies of the integrated gasification combined cycle were calculated to be 24% and 28%, in this order. The highest energy and exergy efficiency with 38.6% and 42.2%, respectively, are observed in January where the wind farm operated at a capacity of 41.7% and the average wind speed was 6.3 m/s for Greater Toronto Area. The overall energy and exergy efficiencies of this waste-to-energy system are calculated as 32.7% and 36.6%, respectively. • The highest volumetric hydrogen rate at the outlet of gasifier was seen to be 62.4% where the steam feed rate was 5 kg/s. • The hydrogen to dewatered sludge ratio was found to be 0.078 and 0.12 at the gasifier and water-gas shift reactor. • The highest energy and exergy efficiency with 38.6% and 42.2%, were observed in January when the wind speed was 6.3 m/s. • The daily energy delivered to the community was found to be 2.1 GWh through waste energy recovery and waste utilization. [ABSTRACT FROM AUTHOR]

In this study, thermal energy management systems with the choices of three different thermal insulating materials are experimentally investigated for robotic applications. These insulating materials are stone wool, fiberglass and extruded polyurethane with air cooling and heating system which are evaluated in the low and high temperature environments to really assess the thermal behavior and performance in such extreme ambient conditions. In this regard, thermodynamic and heat transfer modeling studies are undertaken to investigate various performance parameters, including energy and exergy efficiencies. The experimental results showed that energy efficiencies of the thermal management methods are obtained 46.34% for stone wool, 31.15% for fiberglass, and 44.3% for air cooling system at 40°C. Moreover, the exergy efficiencies are 12.6% for stone wool, 15.08% for fiberglass, 18.91% for extruded polyurethane, and 3.86% for air cooling system. [ABSTRACT FROM AUTHOR]

A new configuration of solar energy-driven integrated system for ammonia synthesis and power generation is proposed in this study. A detailed dynamic analysis is conducted on the designed system to investigate its performance under different radiation intensities. The solar heliostat field is integrated to generate steam that is provided to the steam Rankine cycle for power generation. The significant amount of power produced is fed to the PEM electrolyser for hydrogen production after covering the system requirements. A pressure swing adsorption system is integrated with the system that separates nitrogen from the air. The produced hydrogen and nitrogen are employed to the cascaded ammonia production system to establish increased fractional conversions. Numerous parametric studies are conducted to investigate the significant parameters namely; incoming beam irradiance, power production using steam Rankine cycle, hydrogen and ammonia production and power production using TEGs and ORC. The maximum hydrogen and ammonia production flowrates are revealed in June for 17th hour as 5.85 mol/s and 1.38 mol/s and the maximum energetic and exergetic efficiencies are depicted by the month of November as 25.4% and 28.6% respectively. Moreover, the key findings using the comprehensive dynamic analysis are presented and discussed. • A new solar energy driven integrated system for ammonia synthesis is proposed. • A detailed modelling is conducted on the solar-assisted cascaded ammonia synthesis. • The additional heat from ammonia synthesis is recovered using thermoelectric generators. • Maximum H 2 and NH 3 flowrates are found in 17th hour of June as 5.85 and 1.38 mol/s. • Maximum energetic and exergetic efficiencies are found in Nov as 25.4% and 28.6%. [ABSTRACT FROM AUTHOR]

• A new CSP-geothermal based integrated system with an ejector-absorption cooling cycle is developed. • Parametric energy and exergy analyses are conducted. • Both energetic and exergetic efficiencies and COP values are studied. • Exergy destruction rates are calculated for comparative evaluation. • Optimum operation of the proposed system is identified. A concentrated solar-geothermal integrated system with a combined ejector-absorption refrigeration cycle is proposed and analyzed thermodynamically for a small community application. A detailed thermodynamic model is established for analysis and performance evaluation. A case of a small community in the Yukon Territory is chosen and the system provides all the necessary demands of electric power, space heating and cooling and domestic hot water at high performance. The overall energetic and exergetic efficiencies are 53.33% and 37.07%, respectively, while the COP en and COP ex of the combined cooling cycle are 1.033 and 0.1131, respectively. In addition, numerous parametric studies are presented to illustrate the effects of several energy sources parameters on the overall performance of the integrated system and the combined cooling cycle. Furthermore, ejector parameters are controlled to get the highest COP en value of 1.164. Lastly, the integrated system is optimized exergetically to reach a value of 55.98%, while the overall energetic efficiency becomes 63.60%. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• A novel hybrid solar-wind based system with energy storage via ammonia is developed. • Dynamic simulation and thermodynamic analyses performed to study system performance. • Overall energy and exergy efficiency vary between 46.1 and 53.3% and 34–41.5% annually. • Peak energy output potental of the ammonia based system determined to be 28,463 kWh. In this study, a new renewable energy based integrated system is developed where it stores the excess power generated in the form of ammonia. The developed system integrates both solar and wind energy resources. A dynamic simulation is performed considering the variations in solar radiation intensities as well as wind speeds across the year. The proposed methodology utilizes excess power available during periods of high solar radiation or wind speeds to synthesize and store ammonia that can be utilized for power generation during periods of low energy availability, through ammonia fed solid oxide fuel cells. Further, a reverse osmosis desalination system is also utilized for producing fresh desalinated water during periods of high energy availability. The system performance is simulated and analyzed thermodynamically on the average days of each month. The overall energy efficiency of the developed system is determined to vary between 46.1% and 53.3% across the year. Also, the overall exergy efficiency is found to vary between 34% and 41.5%. The ammonia fed solid oxide fuel cell is observed to have an energy efficiency in the range of 51.9%–80.8% and the exergy efficiency is observed to vary between 51.9% and 91.5%. The energy output potential of the proposed ammonia and solid oxide fuel cell based energy storage system is determined to be 28,463 kWh at the peak value, and the maximum daily fresh water production is evaluated to be 20891.5 tonnes/day. [ABSTRACT FROM AUTHOR]

Abstract This paper examines the performance and viability of a cement slag waste heat recovery system combined with a thermochemical copper-chlorine cycle for hydrogen production combined with hydrogen compression and a reheat Rankine cycle. The waste heat from the cement slag is recovered as a heat source for high-temperature reactions in the copper-chlorine cycle. The clean hydrogen production from waste heat recovery is examined with respect to both energy and exergy efficiencies. The integrated system is simulated and modeled in Aspen Plus. The multigeneration system utilizes the industrial waste heat and significantly reduces operating costs from the waste heat recovery. The overall energy efficiency of the integrated system is obtained as 32.5% while the corresponding exergy efficiency becomes 31.8%. Highlights • A new approach for clean hydrogen production via waste heat recovery. • Hydrogen and electricity are the two major outputs of the designed system. • The compressed H 2 production rate of the system is 19.6 mol/s. • The system overall energy and exergy efficiencies are 32.5% and 31.8%, respectively. [ABSTRACT FROM AUTHOR]

Abstract The thermochemical Cu Cl cycle has received greater attention by numerous researchers during the past decade as a promising hydrogen production method because of some operational advantages. The present paper analyzes three different configurations of the Cu Cl thermochemical cycle, namely three, four and five step ones thermodynamically. Some comparative parametric studies are conducted in order to investigate the overall energy and exergy efficiencies of the cycles considered. The Aspen plus is the software tool employed for the modeling and simulation of the cycles. The energy and exergy efficiencies of the five-step CuCl cycle are found to be 38.8% and 70.2% while the three-step CuCl cycle has an energy efficiency of 39.6% and an exergy efficiency of 68.1%, respectively. On the other hand, the four-step CuCl cycle provides the highest energy and exergy efficiencies of 41.9% and 75.7%. A parametric study is also conducted to investigate the effect of varying ambient temperature on the exergy efficiencies of all three cycles. The present study results further reveal that the cycle performance can be enhanced by improving the thermal management and reducing the exergy destructions. Highlights • Comparative assessment of the three different Cu Cl cycles for hydrogen production. • Numerous factors for heat and work requirements, operating conditions and exergy destructions are considered for analysis. • Aspen plus software tool is employed for the simulations of the cycles. • Four-step CuCl cycle offers the highest energy and exergy efficiencies. [ABSTRACT FROM AUTHOR]

Abstract In the current study, a novel hybridized system for vehicle applications is proposed, analyzed thermodynamically through energy and exergy approaches and evaluated through energy and exergy efficiencies. The current system comprises gas turbine set running on compressed natural gas (CNG), Li-ion battery, CNG tank, two generators, electric motor, power control unit (PCU), thermoelectric generator (TEG), organic Rankine cycle (ORC) and an absorption chiller system (ACS). The overall energy and exergy efficiencies of the proposed system are found to be 38% and 34% respectively at net output power of 63.6 kW from the turbine set. The maximum exergy destruction rate is found in the combustion chamber followed by the TEG unit. For a detailed analysis of the proposed system, a comprehensive parametric study is further carried out to detect the effect of varying the operating and ambient conditions on the system performance. [ABSTRACT FROM AUTHOR]

Abstract In the present study, the solid anion exchange membrane and molten electrolyte entailing direct type ammonia fuel cells are uniquely developed, and their performances are investigated through energy and exergy efficiencies at varying operating conditions and state properties, based on the presently conducted experiments and datasets obtained. Both energy and exergy efficiencies are determined to be 12.1 ± 0.4% and 13.8 ± 0.4% respectively at the maximum power density value of 6.4 ± 0.2 W m−2 for the membrane based cell. Higher humidifier temperatures are observed to improve the performance of the fuel cell. The energy and exergy efficiencies of the molten alkaline electrolyte based cell are found to be 20.6 ± 0.6% and 23.3 ± 0.7% respectively at a temperature of 220 °C. The open circuit voltages are found as 278 ± 8 mV and 520 ± 16 mV for the anion exchange membrane and molten alkaline electrolyte based cells respectively. The open circuit voltage decreases and the short circuit current density increases with increasing electrolyte temperatures. Highlights • Membrane and molten electrolyte based direct ammonia fuel cells uniquely developed. • Membrane based cell has energy and exergy efficiencies of 12.1% and 13.8%. • Molten electrolyte based cell has energy and exergy efficiencies of 20.6% and 23.3%. • Open circuit voltages of 520 mV and 278 mV obtained for the two cells respectively. [ABSTRACT FROM AUTHOR]

A novel multi-generation integrated energy system is presented in this paper, consisting of a gas-steam combined cycle, four-step thermochemical copper-chlorine (Cu Cl) cycle, proton exchange membrane fuel cell (PEMFC) and a reverse osmosis (RO) desalination unit. Effective thermal management of waste heat is recognized as a key objective in the steel industry. Hydrogen, electricity, fresh water and heat are the useful outputs of the integrated system. The produced electricity supplies the electricity load required by the electrolyzer, compressor and pumps while the supplementary electricity is an additional system product. Aspen Plus and Engineering Equation Solver (EES) are used for modeling and simulation of the multi-generation system. The overall hydrogen production rate of the designed system is 51.8 kg/hr and the net power production is 1.7 MW. The overall energy efficiency of the multi-generation system is 63.3% and the exergy efficiency is 58.8%. Further sensitivity studies and outcomes are presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

A novel integrated system for the production of hydrogen at a high pressure utilizing steel furnace waste heat is presented and analyzed in this paper. The system utilizes a hybrid thermochemical copper-chlorine (Cu-Cl) cycle. This study integrates the industrial waste heat source with the thermochemical Cu-Cl cycle combined with a hydrogen compression system. The electrical energy required by the system is provided by a supporting Rankine cycle. The hydrogen compression system compresses hydrogen to a pressure of 750 bars. The integrated system is simulated with Aspen Plus software. Energy and exergy analyses are performed for the integrated system. Results from the simulations are presented and discussed. The overall energy efficiency is 38.2% and overall exergy efficiency is found to be 39.8%. [ABSTRACT FROM AUTHOR]

In the current study, a new carbon-free ammonia-hydrogen internal combustion engine is integrated with thermoelectric generator and ammonia electrolyte cell and proposed for green vehicles. This integrated system aims to produce hydrogen onboard to enhance the combustion characteristics of the ammonia fuel and enhance internal combustion engine performance. The proposed system is analyzed both energetically and exergetically. Also, a dynamic analysis is provided to investigate the dynamic performance of the proposed system during vehicle operation. The overall energy and exergy efficiencies of the integrated system are found to be 31.1% and 28.94% respectively. The highest exergy destruction rates are found for the internal combustion engine followed by the thermoelectric generator system and ammonia electrolyte cell. Furthermore, hydrogen produced from ammonia electrolyte cell was sufficient to provide the internal combustion engine with the required hydrogen for better combustion and engine performance. [ABSTRACT FROM AUTHOR]

In the current study, two different integrated systems for vehicular applications are presented and thermodynamically analyzed. The first system consists of liquefied ammonia tank, dissociation and separation unit (DSC) for decomposition of ammonia and an internal combustion engine (ICE) to power the vehicle. The second system is a hybrid system consisting of liquefied ammonia tank, DSC unit, a small ICE and a fuel cell system. In the second system, the main power unit is fuel cell and a supplementary internal combustion engines is also utilized. The exhaust gasses emitted from the ICE are used to provide the required heat for the thermal decomposition process of ammonia. The ICE is fueled with a mix of ammonia and hydrogen generated from the DSC unit that is installed in the two systems. Hydrogen generated from DSC unit will be utilized to operate fuel cell installed in system 2. The proposed systems are analyzed and assessed both energetically and exergetically. A comprehensive parametric study is carried out for comparative assessments to determine the influence of altering design and operating parameters such as the amount of ammonia fuel supplied to the two systems on the performance of the two systems. The overall energy and exergy efficiencies for system 1 and system 2 are found to be 61.89%, 63.34%, 34.73% and 38.44% respectively. The maximum exergy destruction rate in the two systems occurred in the ICE. [ABSTRACT FROM AUTHOR]

This paper deals with a new hybridly powered photovoltaic- PEM fuel cell – Li-ion battery and ammonia electrolyte cell integrated system (system 2) for vehicle application and is compared to another system (system 1) that is consisting of a PEM fuel cell, photovoltaic and Li-ion battery. The paper aims to investigate the effect of adding photovoltaic to both systems and the amount of hydrogen consumption/production that could be saved/generated if it is implemented in both systems. These two systems are analyzed and assessed both energetically and exergetically. Utilizing photovoltaic arrays in system 1 is able to recover 177.78 g of hydrogen through 1 h of continuous driving at vehicle output power of 98.32 kW, which is approximately 3.55% of the hydrogen storage tank used in the proposed systems. While, using the same photovoltaics arrays, system 2 succeeds to produce 313.86 g of hydrogen utilizing the ammonia electrolyzer system 2 appeared to be more promising as it works even if the car is not in operation mode. Moreover, the hydrogen produced from the ammonia electrolyzer can be stored onboard, and the liquefied ammonia can be used as a potential source for feeding PEM fuel cell with hydrogen. Furthermore, the effects of changing various system parameters on energy and exergy efficiencies of the overall system are investigated. [ABSTRACT FROM AUTHOR]

In the current study, a combined steam and gas turbine system integrated with solar system is studied thermodynamically. In addition, an electrolyzer is added to the integrated system for hydrogen production which makes the current system more environmental friendly and sustainable. This system is then evaluated by employing thermodynamic analysis to obtain both energetic and exergetic efficiencies. The parametric studies are also conducted to investigate the effects of varying operating conditions and state properties on both energy and exergy efficiencies. The present results show that while gas turbine can generate 312 MW directly, 151.72 MW power is generated by steam turbine using solar collectors and exhausted gases recovered from the gas turbine. Furthermore, by adding electrolyzer to the integrated system, a total of 131.3 g/s (472.68 kg/h) hydrogen is generated by using excess electricity which leads to more sustainability system. [ABSTRACT FROM AUTHOR]

A potential cascaded vapor compression heat pump is proposed to address the high temperature heat demand in the copper chlorine (Cu-Cl) thermochemical cycle for hydrogen production. The configuration studied is a cuprous chloride CuCl vapor compression heat pump cascaded with a biphenyl (C 6 H 5 ) 2 heat pump. Such cascaded heat pumps is meant to upgrade heat from nuclear power plants with a heat input temperature of approximately 300 °C or industrial waste heat to meet the Cu 2 OCl 2 decomposition reactor heat demand. Energy and exergy analyses are performed to understand the performance of the heat pump. It is determined that the CuCl-biphenyl heat pump exhibits a high coefficient of performance for certain operating conditions relating to the compressor isentropic efficiency and the excess CuCl feed temperature. The base energetic and exergetic coefficient of performances of the CuCl-biphenyl heat pump are 1.76 and 1.15 respectively. [ABSTRACT FROM AUTHOR]

The current study discusses the first and second laws analyses of a multi-commodity solar energy-based integrated energy system. The system produces hydrogen in a sustainable manner and supplies 500 MW of electricity, hot water, and hot air for space heating for various applications in sectors. Energy and exergy losses of the plant components are calculated based on a thermodynamic model. Based on the total output work, both energy and exergy efficiencies of the overall system are determined. A parametric study is performed by varying inlet air temperature, air-to-fuel ratio, throttling temperature, and condenser temperature. The results show that increasing pressure ratio increases the efficiency from 66% to 68% over a range of 8–25. Increasing the air-to-fuel ratio increases the energy efficiency from 0.60 to above 0.80, respectively. [ABSTRACT FROM AUTHOR]

In this study, we examine an integrated coal based gasification system developed for hydrogen production and power generation. The proposed plant consists of air separation unit, gasification unit, gas cooling and cleaning unit, pressure swing absorption (PSA) for hydrogen production, high temperature electrolyzer for hydrogen production, Brayton cycle, steam Rankine cycle and organic Rankine cycle (ORC) system for power generation. We investigate this system through energy and exergy analyses for hydrogen production. Six coal types, such as Beypazari, Tuncbilek, Can, Yatagan, Elbistan and Soma are considered in this study and energy and exergy efficiencies of these coals are compared to each other for assessment and evaluation. The Aspen Plus and Engineering Equation Solver (EES) software packages are used for system simulation and system analyses. The results show that the overall energy and exergy efficiencies of the entire system become 41% and 36.5%, respectively. [ABSTRACT FROM AUTHOR]

In this article, energy and exergy analyses are conducted for two integrated systems which can be used in HVAC applications. These two systems are analyzed for the cases of single generation, cogeneration and trigeneration, and their performances are evaluated through energy and exergy efficiencies. The parametric studies are performed to investigate the effects of using cogeneration and extended to trigeneration on the system performance. To perform the comparisons between the systems for multiple options, the same amounts of outputs (in terms of electricity, heating, cooling) are produced for all systems. The energy analyses of systems 1 and 2 show a great benefit for moving from single generation to trigeneration, with the trigeneration efficiencies of 83.5% and 87.2%, respectively, and single generation efficiencies of 47% for both systems. However, the exergy analyses show that trigeneration may not always become more efficient than single generation, particularly for system 1, due to the fact that the trigeneration exergy efficiency is 38.7% and the corresponding single generation efficiency is 44.3%. For system 2, the trigeneration exergy efficiency is 52.7% while the single generation efficiency becomes 44.3%. Depending on the type of cogeneration or cogeneration design, the system can be more efficient. [ABSTRACT FROM AUTHOR]

This paper deals with a new hybridly powered photovoltaic-fuel cell - Li-ion battery integrated system and is compared to a base system, consisting of PEM fuel cell and Li-ion battery. It investigates the effects of adding photovoltaic arrays to the base system and further effects on the overall energy and exergy efficiencies and hence hydrogen consumption. These two systems are analyzed and assessed both energetically and exergetically. The study results show that the overall energy and exergy efficiencies become 39.46% and 56.3%, respectively at a current density of 1150 mA/cm 2 for system 1 (fuel cell-battery). Moreover, energy and exergy efficiencies are found to be 39.86% and 56.63% at current density of 1150 mA/cm 2 for system 2 (fuel cell-battery-photovoltaics). Utilizing photovoltaic arrays in system 2 would recover 561 g of hydrogen through 3 h of continuous driving at max power of 98.32 kW, which is approximately 11.2% of the hydrogen storage tank used in the proposed systems. The effects of changing various system parameters on energy and exergy efficiencies of the overall system are also examined. [ABSTRACT FROM AUTHOR]

This paper presents an artificial neural network (ANN) approach of a smart grid integrated proton exchange membrane (PEM) fuel cell and proposes a neural network model of a 6 kW PEM fuel cell. The data required to train the neural network model are generated by a model of 6 kW PEM fuel cell. After the model is trained and validated, it is used to analyze the dynamic behavior of the PEM fuel cell. The study results demonstrate that the model based on neural network approach is appropriate for predicting the outlet parameters. Various types of training methods, sample numbers and sample distribution methods are utilized to compare the results. The fuel cell stack efficiency considerably varies between 20% and 60%, according to input variables and models. The rapid changes in the input variables can be recovered within a short time period, such as 10 s. The obtained response graphs point out the load tracking features of ANN model and the projected changes in the input variables are controlled quickly in the study. [ABSTRACT FROM AUTHOR]

The present study investigates the impact of various discharge rates on the thermal (temperature and heat generation profiles) and electrical performance of the Li-ion battery for electric vehicles and hybrid electric vehicles. For this, a prismatic Li-ion phosphate (LiFePO 4 ) battery with 20 Ah capacity is tested under constant current discharge rates of C/10, C/5, C/2, 1C, 2C, 3C, and 4C and surface temperatures and voltage distributions during both charging and discharging are measured. In addition, IR images were also captured during experiments with a Flir Therma CAM S60 IR camera at various discharge rates and are reported in this study. Furthermore, a thermal model is created and validated for a particular battery using a MATLAB Simulink in terms of temperature, voltage, heat generation, and internal resistance. The results of this study demonstrate that the increased C-rates from C/10 to 4C result in increased temperatures on the principal surface of the battery. Also, at the lower discharge rates (below 1C), the surface temperature remains close to the ambient temperature, but at higher discharge rates (above 1C); the surface temperature quickly increases for all C-rates. The most noteworthy surface temperature distribution is observed to be 58.1 °C towards the end of 4C discharge. [ABSTRACT FROM AUTHOR]

An integrated system for converting carbon dioxide to methanol is proposed, and four of its main components (carbon capture absorber, carbon capture stripper, photoreactor, and methanol synthesis reactor) are analyzed thermodynamically, focusing on exergy destruction. The carbon capture unit provides carbon dioxide extracted from industrial flue gas while the photocatalysis unit produces hydrogen from visible light via photocatalytic water splitting. Both, carbon dioxide and hydrogen are supplied to a methanol synthesis reactor at a specific feed rate, temperature and pressure. The thermodynamic analysis shows that the largest exergy destruction rate occurs in the photoreactor (706 kW). The second largest exergy destruction rate occurs in the methanol synthesis reactor (24.7 kW), while the exergy destruction rates are smaller in the carbon capture stripper (23.5 kW) and absorber (17.9 kW). [ABSTRACT FROM AUTHOR]

A multigeneration system based on solar thermal energy associated with hot and cold thermal storage is designed and analyzed energetically and exergetically. The system produces electricity, a heating effect, a cooling effect, hydrogen, and dry sawdust biomass as outputs by means of organic Rankine cycles, a heat pump, two absorption chillers, an electrolyser, and a belt dryer. The intermittent behavior of the renewable energy source is addressed through the incorporation of hot and cold thermal storage systems to operate an organic Rankine cycle and provide cooling at night. The performance assessment indicates that the overall (day and night) energy and exergy efficiencies are 20.7% and 13.7%, respectively. The majority of the total exergy destruction is attributable to the sawdust belt dryer, at about 64.0%. [ABSTRACT FROM AUTHOR]

In this study, an integrated gasification combined cycle based trigeneration system is proposed to produce power, hydrogen and various Fischer–Tropsch (FT) synthesis products. The proposed plant consists of an (a) air separation unit; (b) a gasification system with coal preparation and gas clean up units; (c) Fischer–Tropsch synthesis unit, (d) pressure swing absorption (PSA) unit for hydrogen production, (e) an integrated Brayton cycle, Steam Rankine Cycle, Organic Rankine cycle system for power production. The Aspen Plus software package is utilized to simulate this modified integrated gasification combined cycle (IGCC) plant for five different Turkish lignites. A case study is conducted for a large scale plant with 30 kg/s of lignite feed. The results of this study show that using such an integrated system for low-quality lignites will offer a more efficient, cost effective and environmental friendly option. The overall energy and exergy efficiencies of the system are found to be 53% and 46%, respectively. [ABSTRACT FROM AUTHOR]

In this review paper, some novel energy options for clean rail applications are discussed and evaluated. Rail transportation is of strategic importance and therefore a reliable, clean, sufficiently abundant and cost expensive fuel is required. It has been found that integration of selective catalytic reducer and increase of bio-diesel used (including blending with petrochemical diesel) may be an immediate solution which bring some benefits such as up to 50% reduction on environmental impact. However, accounting for the technical feasibility of the solution, the worldwide existence of a well-established infrastructure, high efficiency and lower emissions, the natural gas appears as a key potential option for the railway. Other reviewed technologies include the CNG, LNG-LPG, methanol, ammonia and hydrogen as fuels. Electrical railways represent a solution where large investment is available. Hydrogen, is most likely a solution for the far future, when an infrastructure could be set-up. The life cycle assessment shows high ecological advantages of NG with respect to the baseline diesel with average 15% decrease of environmental impact categories. A novel criterion has been used here to assess the environmental impact which is suitable for pollutant emitting applications such as railway transportation. This criterion is denoted as environmental impingement work of the polluting effluent which is calculated based on the chemical exergy of the polluting species. Chemical exergy is a true measure of the impingement (change, modification) produced by the pollutant on the environment. It is shown that the well-to-wheel environmental impingement of natural gas fuelled locomotive is inferior with at least 15% to diesel-electric locomotive equipped with a selective catalytic reducer. The environmental impact in terms of work impingement on the environment and environmental pollution cost are slightly similar for natural gas, ammonia, methanol and biodiesel fuels. The life cycle environmental impact categories of natural gas locomotive are overall 15% lower than for the conventional diesel-electric locomotive. According to our conclusion, liquefied natural gas is indicated as a prime potential option for clean rail transportation. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive steady state modelling and thermodynamic analysis of Direct Urea Solid Oxide Fuel Cell integrated with Gas Turbine power cycle (DU-SOFC/GT). The use of urea as direct fuel mitigates public health and safety risks associated with the use of hydrogen and ammonia. The integration scheme in this study covers both oxygen ion-conducting solid oxide fuel cells (SOFC-O) and hydrogen proton-conducting solid oxide fuel cells (SOFC-H). Parametric case studies are carried out to investigate the effects of design and operating parameters on the overall performance of the system. The results reveal that the fuel cell exhibited the highest level of exergy destruction among other system components. Furthermore, the SOFC-O based system offers better overall performance than that with the SOFC-H option mainly due to the detrimental reverse water-gas shift reaction at the SOFC anode as well as the unique configuration of the system. [ABSTRACT FROM AUTHOR]

This paper presents a thermodynamic analysis of a steam reformer coupled with a combined power plant to produce hydrogen from steam and hydrocarbon fuel. In the analysis, the steam reformer uses glycerol as a fuel and produces hydrogen for high temperature proton exchange fuel cells in which the catalyst is tolerant to the amount of carbon monoxide. The results show that increasing the steam to glycerol ratio increases the hydrogen production. However, it decreases the overall efficiency of the system because of the high heat input requirement to the system. Numerous operating conditions and plant parameters are varied and their effects on the overall energy and exergy efficiencies of the system are studied. An optimization study is performed in order to find the optimal system parameters for better performance. [ABSTRACT FROM AUTHOR]

In this paper, a conventional solid oxide fuel cell (SOFC) is modeled, and its performance is assessed to investigate the main challenges that limit low temperature operation. SOFCs have numerous advantages over other fuel cell technologies; however, a major drawback of SOFCs is the high operating temperature (over 600 °C) which significantly reduces SOFCs lifetime and constrains manufacturing materials to costly produced composites. Therefore, the development of a low temperature solid oxide fuel cell (LT-SOFC) will improve the cost effectiveness of this technology and thereby enhance efficient energy utilization and contribute to CO 2 emission reduction. In this regard, a model is employed to predict the conventional SOFC performance under different operating and design conditions, in general, and at low operating temperatures, in particular. Furthermore, the contribution of each of the polarizations is evaluated. The model results are validated through a comparison with published experimental data and found to be in a good agreement with a maximum possible error value of 10.3% in cell potential and power density output. The results show that conventional SOFCs are vulnerable to a significant performance reduction when operating at low temperatures (below 600 °C). In addition, the polarization that SOFCs experience at low operating temperatures is mainly attributed to electrolyte ohmic loss. [ABSTRACT FROM AUTHOR]

The results are reported of an investigation of the effects of cascading air-source heat pumps on performance for hydronic residential systems. Three heat pump systems are modeled as single-stage, single-refrigerant cascaded, and two-refrigerant cascaded. Energy and exergy analyses are performed, and a comparative performance analysis is carried out, considering energy efficiency, refrigerant mass flow rates, evaporator pressure, exergy efficiency, and several other criteria. Three sets of source and supply temperatures, representing different climates and different water sink systems (low, medium and high temperature), are used to provide more comprehensive behavior assessments of the systems. Additionally, the optimum intermediate pressure of the cascaded systems for all working temperature pairs is found for the highest energetic COP and exergetic COP. Compared to a single stage heat pump, cascading improves the overall energy efficiency of the system for low-ambient temperatures, but not for high-ambient temperatures. Although this improvement is minor, the exergetic COP is increased by 67% for the single refrigerant cascaded system and 70% for a two-refrigerant cascaded system, at low ambient temperatures. Using refrigerant R404A in the low-pressure cycle marginally improves the energetic COP of the cascaded heat pump, but increases the evaporator working pressure, making it possible to use smaller compressors. However, the overall refrigerant mass flow rates increase with cascading. The two cascaded systems have higher exergy destructions (by almost four times) compared to the single stage system, mainly due to having more components, including an intermediate heat exchanger. Also, cascading shifts the major exergy destruction centers from the compressors and expansion valves to the evaporators. A comparison of cascaded and single-stage heat pumps shows that the exergy analysis results exhibit a different trend than energy analysis results with source and supply temperatures, highlighting the advantages of exergy methods in determining if cascading is appropriate for a given application. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents experimental investigation of the performance of an organic Rankine cycle (ORC) with scroll expander which utilizes renewable, process and waste heats. An ORC test bench is built with a scroll expander-generator unit modified from a refrigeration compressor-electrical drive unit. A detailed experimental investigation within the test bench is performed with the organic working fluid R134a. The results show that scroll expander can effectively be used in low-power ORC to generate mechanical work or electricity from low-temperature thermal sources (e.g. 80-200 °C, respectively). The experiments are performed under fixed intake conditions into the expander. The pressure ratio and the load connected to the expander-generator unit were varied. It is found that an optimum pressure ratio and an optimum angular speed co-exist. When operating optimally, the expander's isentropic efficiency is the highest. The optimum angular speed is around 171 rad/s which corresponds to a generated voltage of 18.6 V. The optimum pressure ratio is about 4. The isentropic efficiency at optimum operation is found in the range of 0.5 to 0.64, depending on the intake conditions. The volumetric efficiency overpasses 0.9 at optimum operation and degrades significantly if the load is increased over the optimum load. A regenerative ORC equipped with the studied expender-generator unit that operates under 120 °C heat source and has an air cooled condenser generates 920 W net power with efficiencies of 8.5% energetically and 35% exergetically. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A new integrated system, which combines three renewable energy sources and generates five different commodities as useful outputs, is proposed and analyzed energetically and exergetically. The mass, energy, entropy and exergy balance equations for the major components of the integrated system are written and analyzed. The energy and exergy efficiencies for the integrated system and its subsystems are defined and calculated. Parametric studies are conducted by varying dead state properties and operating conditions to investigate their effects on the system performance. Some meteorological and system data from various previous studies are used in the analyses and assessments. The results show that the energy and exergy efficiencies of the integrated system become 36.67% and 25.075% respectively. [ABSTRACT FROM AUTHOR]

In the present study, the effects of different processing parameters on rate of hydrogen, chlorine and sodium hydroxide production are experimentally studied in a newly designed chloralkali process reactor. It is a multi membrane reactor which can also be coupled with a photochemical hydrogen production process. The parameters, which are studied in the present study, include applied voltage varied from 3 V to 20 V, brine concentration varied from 150 g/L to 225 g/L, electrolyte concentration in catholyte compartment varied from 35.3 g/L to 58.8 g/L, electrode height, temperature and different anode materials. A factorial design of experiments is applied and an analysis of variance (ANOVA) is used to analyze the experimental results. Energy and exergy efficiencies are also determined and discussed. The results show that graphite appears to be the most stable anode material. Brine and electrolyte concentration do not affect the production rate of products. Increasing the temperature increases the production but also increases the energy input to the system. Varying electrode height changes the current density which has a significant effect on rate of hydrogen production [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a comparative energetic and exergetic study is conducted to analyze novel multi-flash (single to quintuple) geothermal power generating systems which are newly integrated with electrolyzers for hydrogen production. The effects of increasing the number of flashing from one to five for the system on its performance are carefully studied for practical applications. In addition, parametric studies are undertaken to investigate the effects of varying several operating conditions on the performance of the integrated multi-flash systems. The results show that increasing ambient temperature results in smaller exergy destruction rates and higher overall exergy efficiencies. Furthermore, the quintuple-flash system integrated with electrolyzer provides the largest power output and the highest energy and exergy efficiencies among the systems considered. The power generation, hydrogen production rate and overall energy and exergy efficiencies of the quintuple flash integrated system are found to be varying from 6.8 kW to 112.9 kW, 2.6 L s−1 to 44.21 L s−1, 2.8%–4.6%, and 46.5%–53.4%, respectively, by increasing the geothermal source temperature. [Copyright &y& Elsevier]

This paper deals with energy and exergy analyses of a multi-flash integrated system and studies three efficiency definitions for system assessment. In this regard, a comparative performance evaluation is conducted to investigate the effects of using these energy and exergy efficiencies on the assessment of a triple-flash integrated system with an electrolyzer. Parametric studies are conducted to investigate the effect of rise in the ambient temperature and geothermal source temperature on these energy and exergy efficiencies. The results show that the efficiency definition plays a critical role as the efficiency value differs from one definition to another. Increasing the ambient temperature decreases both energy and exergy efficiencies based on the first definition, but increases them based on the second and third definitions. An increase in the geothermal source temperature reduces both energy and exergy efficiencies based on the first definition, but increases them based on the second and third definitions of efficiencies. The energy and exergy efficiencies of the overall system based on the third definition are found to be increasing from 0.6 to 2.2% and 6.5 to 47.29%, respectively. [ABSTRACT FROM PUBLISHER]

SUMMARY In this paper, a novel integrated solar photovoltaic thermal absorption desalination system for freshwater and cooling production is proposed and analyzed thermodynamically. Ammonia-water pair is considered as a working fluid for the absorption system. Effect of average solar radiation for different months, time period of solar radiation availability in Abu Dhabi, salinity of seawater, and temperature of the seawater on energetic and exergetic COPs, production rate of freshwater, and overall performance of the system are investigated under different operating conditions. It is found that energetic and exergetic COPs, production rate of freshwater, energetic and exergetic utilization factors, and performance ratios vary greatly from one month to another because of the dynamic variation in solar radiation and its time of availability. The highest amount of freshwater is produced in the month of July as calculated to be 152 kg/h for a collector area of 100 m2 and solar power of 4.8 kW. The highest energetic and exergetic COPs and utilization factors are also obtained for the month of July. Moreover, the highest performance ratio is found to be 0.056 as obtained in the month of July when solar radiation intensity is highest as available for more than half of a day. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A residential photovoltaic (PV)-based hydrogen fuel cell (FC) system is analyzed using exergoeconomic methods, and its monthly performance is investigated. Mathematical models for predicting the power outputs of the PV and FC systems are presented. The results reported include the PV output and the shares attributable to the battery and the SOFC in supplying the electrical demand. Moreover, to study the performance of the hybrid system in supplying the daily demand, results are presented for two typical days in summer and winter. An exergoeconomic analysis is performed to determine the electricity unit cost over the system lifetime. The PV-electrolyzer system is not able to produce a sufficient amount of hydrogen during winter days, so seasonal hydrogen storage is required to feed the FC. Power penetrations of the PV and the battery systems are at maxima during the summer months, while the penetration of the FC system reaches 67% in January and December. Due to its low efficiency (16%), the maximum exergy destruction occurs in the PV modules (86%). The unit cost of electricity varies on a monthly basis, reaching a minimum of 0.26 $ kWh-1 in July and a maximum of 1.8 $ kWh-1 in January and December. [ABSTRACT FROM AUTHOR]

Highlights: [•] Energy and exergy analyses of integrated solar heliostat-based Cu–Cl systems. [•] Parametric studies to investigate effect of different operating parameters. [•] Comparative study to show which system performs better. [Copyright &y& Elsevier]

Highlights: [•] Energy and exergy analyses of geothermal based integrated system. [•] Parametric studies to investigate effect of variation in operating parameters on the system performance. [•] Multi-generation system developed for producing power, hydrogen, hot water, heating, cooling and dried air. [Copyright &y& Elsevier]

Abstract: 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 &y& Elsevier]

Abstract: The study focuses on defining energy and exergy efficiencies based on three different types of approaches. For each of five key psychometric processes, such as heating or cooling, heating with humidification, cooling with dehumidification, evaporative cooling, and adiabatic mixing, parametric studies are carried out. Two efficiencies are newly proposed here in this study, and the third efficiency is taken from the literature for comparison purposes. The results show that for heating process exergy efficiency varies from 0.012 to 0.48 with rise in ambient temperature. Increasing ambient temperature results in variation of exergy efficiency from 0.014 to 0.29 for heating with humidification process. For cooling with dehumidification process exergy efficiency varies from 0.002 to 0.73 with rise in ambient temperature. The exergetic efficiency of evaporative cooling process varies from 0.64 to 0.03 with an increase in ambient temperature. For adiabatic mixing process, exergy efficiency varies from 0.65 to 0.94 with rise in ambient temperature. [Copyright &y& Elsevier]