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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 novel configuration of hybrid wind-solar PV based cascaded ammonia synthesis is proposed in this article. A comprehensive dynamic analysis is conducted in this study which is substantial to explore the system functionality under different atmospheric conditions as the power achieved by the wind farm source is dependent on the wind speed and power extracted from the solar PV source depends upon solar radiation intensities. The system is designed to supply the electrical output extracted from the wind-solar PV sources to the proton exchange membrane electrolyser after meeting the system work requirements for hydrogen production. The produced hydrogen reacts with nitrogen separated from pressure swing adsorption to synthesize ammonia. A cascaded ammonia synthesis system is employed in this study to achieve high fractional conversion and simulated using Aspen Plus V11. Toronto is chosen as the geographical location for the dynamic simulation. The minimum exergetic efficiency is found to be 19.21% during the month of December and maximum exergetic efficiency is determined as 26.06% during the month of April. Similarly, the minimum energetic efficiency is found to be 18% during December and maximum energetic efficiency was determined as 24.42% during the month of April. In addition, the results obtained from comprehensive dynamic analyses are presented and discussed. • A novel hybrid wind-solar PV based cascaded ammonia synthesis is proposed. • A comprehensive dynamic analysis is conducted to explore the system functionality. • Toronto is chosen as the geographical location for dynamic simulations. • The maximum efficiency is determined for the month of April. [ABSTRACT FROM AUTHOR]

In this study, a novel Ocean Thermal Energy Conversion (OTEC) based tri-generation system that produces ammonia, cooling and power is developed and analysed. This OTEC plant operates on the naturally existing temperature difference that exists in various depths of the ocean. The OTEC plant used in this study is operated using a single-stage ammonia Rankine cycle. The discharge seawater from the condenser in the organic Rankine cycle is used to provide district cooling. Two different operation cases of the analysed system are considered, where for the first case 50% of the power produced is stored in the form of ammonia during the off-peak hours. The second case is for complete power production proposed for peak hours. For the case where 50% of the power produced (case 1) is used to produce ammonia the highest energy and exergy efficiency is found to be 1.37% and 56.17% respectively. As for the case where, only power is produced (case 2) the maximum energy and exergy efficiency of the OTEC plant is found to be 1.83% and 78.02% respectively. The corresponding maximum power production was 6612 kW and 13,224 kW for cases 1 and 2. The maximum hydrogen and ammonia production rate is found to be 94.35 kg/h and 534.7 kg/h at peak efficiency values. The cooling duty at the peak energy and exergy efficiency is found to be 64.4 MW where the condenser temperature is 11.38 °C. • A comprehensive study for the cooling duty associated with OTEC is performed. • Energy and exergy efficiencies of the system are found to be 1.37% and 56.17% (Case 1). • Energy and exergy efficiencies of the system are found to be 1.83% and 78.02% (Case 2). • The maximum hydrogen and ammonia production rates are 94.35 kg/h and 534.7 kg/h. [ABSTRACT FROM AUTHOR]

A novel idea of solar driven steam-autothermal hybrid reforming system (SAHRS) is proposed with onboard carbon capturing system in the existence of carbon emissions taxes. The CO 2 produced by the steam methane reforming is employed to the autothermal reforming as input and cryogenic air separation unit is integrated to provide autothermal reforming with oxygen and ammonia synthesis with nitrogen. The autothermal reforming is modified with further integration of water gas shift reactor (WGSR) which converts carbon mono-oxide into carbon dioxide by reacting with steam and this CO 2 is captured in the carbon capturing system using aqueous ammonia. Some amount of hydrogen produced by the autothermal reforming is employed to the ammonia synthesis reactor to achieve onboard ammonia for CO 2 capture. The system generates enough power to overcome the required power and supply power as a final commodity as well. The present system is essentially designed for cleaner production and industrial applications. The performance indicator for the designed system is defined in terms of energy and exergy efficiencies which are found to be 53.4% and 45.0% respectively. The carbon emissions produced by the system and tax saving by the aqueous ammonia based CO 2 capturing are also calculated in the proposed study. [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 biomass and solar energy based system is developed and comparatively evaluated. • The proposed system is analysed thermodynamically by energy and exergy approach. • Hydrogen, electricity, hot water for fish farming and cooling are major commodities. • The hydrogen production rate of 59.45 mol/s and power of 8.3 MW is produced. • The overall energy and exergy efficiencies are found to be 29.9% and 31.5%. A biomass and solar energy based system consisting of a gas turbine cycle, a reheat Rankine cycle, a solar heliostat field, four-step copper-chlorine cycle and absorption cooling system is newly proposed, analyzed and comparatively evaluated through energy and exergy approaches. The proposed system is designed for the multiple useful commodities of hydrogen, electricity, hot water for fish farming and cooling. The effects of different operating conditions and parameters, namely air flow rate, biomass flow rate, working fluid flow rate, direct normal irradiance, number of heliostats, evaporator exit temperature and ambient temperature are investigated for the performance of the designed system defined in terms of energy and exergy efficiencies, and energy and exergetic coefficients of performance. The combined system, excluding solar heliostat field and absorption cooling system, is simulated using the Aspen Plus while the subsystems are modeled using the engineering equation solver package. Heating and cooling are produced for community usage, and hydrogen can be employed for industrial purposes. Both design and cost analyses are also conducted using the Aspen Plus v9 and Aspen Plus economic analyzer v9. The energy efficiency of the overall system is determined as 29.9% while the corresponding exergy efficiency is obtained to be 31.5%. The additional findings and outcomes are also presented and discussed comprehensively. [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]

Abstract A solar-wind hybrid trigeneration system is proposed and analyzed thermodynamically through energy and exergy approaches in this paper. Hydrogen, electricity and heat are the useful products generated by the hybrid system. The system consists of a solar heliostat field, a wind turbine and a thermochemical copper-chlorine (Cu-Cl) cycle for hydrogen production linked with a hydrogen compression system. A solar heliostat field is employed as a source of thermal energy while the wind turbine is used to generate electricity. Electric power harvested by the wind turbine is supplied to the electrolyzer and compressors and provides an additional excess of electricity. Hydrogen produced by the thermochemical copper-chlorine (Cu-Cl) cycle is compressed in a hydrogen compression system for storage purposes. Both Aspen Plus 9.0 and EES are employed as software tools for the system modeling and simulation. The system is designed to achieve high hydrogen production rate of 455.1 kg/h. The overall energy and exergy efficiencies of the hybrid system are 49% and 48.2%, respectively. Some additional results about the system performance are obtained, presented and discussed in the paper. Highlights • Analysis of a solar, wind and hydrogen hybrid trigeneration system. • A novel system of an integrated solar and wind source with the Cu-Cl cycle. • The three commodities of hydrogen, electricity and heat are produced. • Energy and exergy analyses are conducted for the integrated system. • The overall energy and exergy efficiencies are 49% and 48%, 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 this study, both concentrated solar power and wind energy systems are integrated with electrolyser, fuel cell and absorption cooling subsystems to supply power, cooling, heating and hydrogen to residential applications in an environmentally benign and efficient manner. These subsystems are integrated in a unique way to manage the excess power through water electrolysis to produce and store hydrogen. Integrated systems are thermodynamically analyzed, and their performance is assessed comparatively. Solar radiation intensity, inlet temperature and wind velocity are taken into account, and hence their effects on the system performance are investigated. The results of this study show that the present system appears to be efficient, environmentally friendly and hence sustainable. [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]

This paper deals with a new multigeneration system which is primarily powered by renewable energy, geothermal energy and assisted with solar energy. This multigeneration system consists of a single flash geothermal cycle, heat pump system, single-effect absorption cooling system, thermal energy storage connected with auxiliary steam turbine, hot water system and drying system. The aim of this system is to produce five output commodities; refrigeration for industry, heating air for residential application, hot water for domestic use, drying food and finally electricity. The system is assessed both energetically and exergetically. The overall energy and exergy efficiencies are found to be 69.6% and 42.8% respectively. The effects of changing various system parameters on energy and exergy efficiencies of the overall system and its subsystems are examined accordingly. [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]

This paper develops and analyzes a new photo electrochemical reactor that uses zinc sulfide as a photo catalyst to produce hydrogen, chlorine and sodium hydroxide. The effects of different parameters on the rate of hydrogen, chlorine and sodium hydroxide production are experimentally studied. The parameters include the applied voltage, varied from 4 V to 5 V, amount of catalyst, varied from 1 g/425 mL to 5 g/425 mL and light intensity, varied from 20 W/m 2 to 55 W/m 2 . A factorial design of experiments is applied and an analysis of variance (ANOVA) is used to examine the experimental results. Energy and exergy efficiencies are also calculated. An optimization is performed to find the optimal catalyst concentration. At the optimized catalyst concentration, salt water is used to check its effect on the rate of hydrogen production. [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]

A solar based integrated system for hydrogen and methanol production is investigated. Energy and exergy analyses of a hydrogen production plant, thermodynamic assessment of a methanol synthesis plant, and exergy analysis of the integrated solar based system for hydrogen and methanol production, are performed. The analysis of hydrogen production is performed for the methanol synthesis procedure. The present analysis shows the effects of temperature and current density of the electrolyser on hydrogen production. The optimum temperature of methanol synthesis is obtained for the final design of the methanol plant. It is shown that increasing the pressure improves the methanol synthesis process. Methanol conversion takes place at 493 K . The energy and exergy efficiencies of the system are reduced by 30% if the electrolyser operates at 300 K . The efficiencies of the system are also highly dependent on the solar intensity. The system efficiencies can be tripled if the intensity of solar radiation is increased to 600 W/m 2 instead of 250 W/m 2 . [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]

The paper focuses on comparative energy and exergy analyses of two solar based integrated systems namely (a) solar heliostat field system integrated with Cu–Cl cycle and Kalina cycle (as system 1) and (b) solar heliostat field system integrated with Cu–Cl cycle, Kalina cycle and photocatalytic reactor (as system 2) for producing hydrogen. A parametric study is conducted to investigate the effects of varying the operating conditions and system parameters on the performances of these integrated systems. The effects of variations in solar light intensity, ambient temperature and mass flow rate of the ZnS on the hydrogen production rate and overall energy and exergy efficiencies are studied and presented comparatively. The results show that hydrogen production rate increases from 126.9 L/s (986.0 kg/day) to 289.4 L/s (2248.6 kg/day) and 154.1 L/s (1197.4 kg/day) to 343.9 L/s (2672.1 kg/day), respectively, with rise in solar light intensity from 600 W/m 2 to 1200 W/m 2 . The overall exergy efficiencies of the integrated systems are found to be increasing from 45.6% to 47.79% for system 1 and from 54.94% to 56.41% for system 2, respectively with an increase in solar light intensity. It is also observed that the rise in ambient temperature has no effect on the energy efficiencies of systems 1 and 2, but the exergy efficiencies of systems 1 and 2 are found to be increasing from 47.98% to 50.82% and 56.87% to 59.64%, respectively. The hydrogen production rates of the photocatalytic reactor and system 2 are noticed to be decreasing from 47.2 L/s (366.74 kg/day) to 42.23 L/s (328.1 kg/day) and 282.5 L/s (2195 kg/day) to 277.5 L/s (2156.2 kg/day), respectively with increase in mass flow rate of zinc sulfide from 0.45 kg/s to 0.70 kg/s. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new integrated, solar and geothermal energy based system for multigeneration applications, which comprises two ORC (organic Rankine cycles) for power generation, an absorption chiller cycle for cooling production and a drying system to dry wet products. In addition, some useful heat is recovered from the condensers of the ORC for heating applications. In order to determine the irreversibilities, almost all the system components are examined energetically and exergetically. The overall energy and exergy efficiencies of the system are found to be 54.7% and 76.4%, respectively. Moreover, to analyze the system efficiently, parametric studies are also performed to observe the effects of different substantial parameters namely inlet pressure and temperature of the ORC turbine, and reference environment temperature in order to investigate the variations in the system performance in terms of the energy and exergy efficiencies. [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]

The dissociation of gaseous hydrogen sulphide (H 2 S) into its components is an energy intensive process. The process is studied in this paper with respect to the thermodynamic limits. The band gap of the catalyst and the nature of the solar radiation limit the proportion of incoming radiation that may be used for the reaction. The intensity of the incoming radiation and the reactor temperature are varied and the performance is studied. The exergy efficiency is determined as a function of the quantum efficiency of the photochemical process, and the catalyst band gap. It is shown that an optimum case exergy efficiency of up to 28% can be achieved for the process. With the current status of technology, an exergy efficiency value in the region of 0.4–1% is calculated, with a short-term improvement potential of up to 10%. Hydrogen sulfide has high energy content, but is not widely used due to its impact on environmental pollution. The proposed process in this paper is attractive as it allows that energy to be utilized, while degrading the highly toxic gas into less harmful products. [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]

In this paper, production of hydrogen from concentrated solar radiation is examined by a laboratory scale solar tower system that is capable of handling continuous flow photocatalysis. The system is built and studied under a solar simulator with an aiming area of 20 × 20 cm2. The fraction of solar spectrum useful for water splitting depends on the energy band gap of the selected photocatalyst. Two types of nano-particulate photocatalysts are used in this work: ZnS (3.6 eV) and CdS (2.4 eV). The effect of light concentration on photocatalysis performance is studied using Alfa Aesar 99.99% pure grade, 325 mesh ZnS nano-particles. An improved quantum efficiency of 73% is obtained as compared to 45% with the same sample under non-concentrated light in a previous study. Only 1.1% of the energy of the solar radiation spectrum can be used by ZnS catalyst. A mixture of CdS and ZnS nano-particulate photocatalysts (both Alfa Aesar 99.99% pure grade, 325 mesh) is used to conduct a parametric study for a wider spectrum capture corresponding to 18% of the incident energy. Hydrogen production increases from 0.1 mmol/h to 0.21 mmol/h when the operating conditions are varied from 25 °C and 101 kPa to 40 °C and 21 kPa absolute pressures. Furthermore, the implementation of a continuous flow process results in an improvement in the energy efficiency by a factor of 5.5 over the batch process. [ABSTRACT FROM AUTHOR]

Abstract: In present study, a new reactor configuration is developed which integrates photochemical hydrogen production with an electrochemical chloralkali process. The effects of different parameters on rate of hydrogen, chlorine and sodium hydroxide production are experimentally examined and discussed. The parameters include applied voltage, varied from 4 V to 5 V, amount of catalyst, varied from 1 g/425 mL to 4 g/425 mL, and light intensity, varied from 20 W/m2 to 55 W/m2. 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 examined. An optimization study is performed to find the optimal catalyst concentration. An optimized catalyst concentration in salty water is used to examine its effect on the rate of hydrogen production. [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]

Highlights: [•] Comparative study of novel renewable energy-based hydrogen production systems. [•] Thermodynamic analysis of the integrated systems through energy and exergy. [•] Performance comparison of the integrated systems through energy, exergy and sustainability. [Copyright &y& Elsevier]

Abstract: 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 &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]