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Despite its shortcomings, fossil-based fuels are still utilized as the main energy source, accounting for about 80% of the world's total energy supply with about one-third of which comes from coal. However, conventional coal-fired power plants emit relatively higher amounts of greenhouse gases, and the derivatives of air pollutants, which necessitates the integration of environmentally benign technologies into the conventional power plants. In the current study, a H 2 –CO synthesis gas fueled solid oxide fuel cell (SOFC) is integrated to the coal-fired combined cycle along with a concentrated solar energy system for the purpose of promoting the cleaner energy applications in the fossil fuel-based power plants. The underlying motivation of the present study is to propose a novel design for a conventional coal-fired combined cycle without altering its main infrastructure to make its environmentally hazardous nature more ecofriendly. The proposed SOFC integrated coal-fired combined cycle is modeled thermodynamically for different types of coals, namely pet coke, Powder River Basin (PRB) coal, lignite and anthracite using the Engineering Equation Solver (EES) and the Ebsilon software packages. The current results show that the designed hybrid energy system provide higher performance with higher energy and exergy efficiencies ranging from 70.6% to 72.7% energetically and from 35.5% to 43.8% exergetically. In addition, carbon dioxide emissions are reduced varying between 18.31 kg/s and 30.09 kg/s depending on the selected coal type, under the assumption of 10 kg per second fuel inlet. [Display omitted] • A novel coal-fired energy system integrated with solar and solid oxide fuel cell subsystems is proposed. • The designed system is simulated for four different types of coals. • The proposed system is analyzed through energy and exergy approaches. • The highest energetic and exergetic efficiencies are found to be 72.7% and 43.8%, respectively. [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]

A thermodynamic model is proposed to study the exergetic content of incident solar radiation reaching on the Earth’s surface which can be used to produce work through a dually cascaded thermodynamic cycle. The “topping” cycle is an ad hoc engine created by nature that connects the outer shell of the terrestrial atmosphere (which is in equilibrium with the extraterrestrial solar radiation) to the collector of a solar heat engine operating on the Earth’s surface. The work produced by the topping cycle is dissipated in form of scattering, absorption, heat, movement of air masses (wind), etc. The “bottoming” cycle is a heat engine operating between the collector and surrounding temperatures, and delivers useful work. It is shown that the maximum work extractable from this system as exergy is obtained when both cycles operate reversibly. An expression for this maximum work, which represents the exergy of incident solar radiation on the Earth’s surface, is proposed. The application of the present model is illustrated and validated by calculating the exergy of solar radiation based on some measurements. The results obtained by the present model are compared to the ones obtained through other models available in the open literature. [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 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]

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]

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]

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]

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]

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 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]

The current study presents an experimental investigation of a hybrid photo-electrocatalytic hydrogen production reactor for aiming to replace the electrolysis component of the Cu–Cl cycle. The glass material is used to manufacture the lab scale device, consisting of the anolyte and the catholyte compartments separated by the membrane. In the anolyte compartment, a solution of CuCl, HCl and water is used, whereas, in the catholyte compartment, a solution of ZnS, NaOH, Na 2 S, and water is used. In the present study, ZnS is used as the photocatalyst to generate an additional potential in the catholyte compartment to produce hydrogen by breaking water molecules. Multiple operating parameters, such as applied voltage, solar light intensity, the mass of CuCl and mass of ZnS are varied to observe their effects on the hydrogen production rate. The results obtained from this study show that the rate of hydrogen production varies from 0.73 to 1.61 μg/s with an increase in applied voltage and mass of CuCl from 2.5 to 3.5 V and 5–10 g, respectively. It is also observed that the rate of hydrogen production varies from 1.37 to 1.64 μg/s with an increase in applied voltage and mass of ZnS from 2.5 to 3.5 V and 2–4 g, respectively. [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]

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 study, we perform experimental investigations of a novel hybrid photocatalytic hydrogen production reactor for a Cu–Cl cycle. The effects of different operating conditions, such as solar light intensity, mass of zinc sulfide and mass of Cu–Cl on rate of hydrogen production are studied. The experimental results show that the photocatalytic hydrogen production rate increases from 0.21 to 0.50 μg/s with an increase in solar light intensity, mass of CuCl and mass of ZnS from 400 to 500 W/m 2 , 5–10 g and 2–4 g, respectively. It is also observed that increasing the solar light intensity and the mass of ZnS from 400 to 500 W/m 2 and 2–4 g, respectively results in increase in hydrogen production rate from 0.28 to 0.48 μg/s. The experimental results further show that replacing the electrolyzer component of Cu–Cl with the studied hybrid photocatalytic reactor can help in making the Cu–Cl cycle more environmentally benign. [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]

In this paper, a novel integrated system that combines photocatalysis, photovoltaics, thermal engine and chemical energy storage for better solar energy harvesting is assessed using energy and exergy methods. The system generates hydrogen and sulfur from sulfurous waters specific to chemical and petrochemical industries. The solar light is split into three spectra using optical surfaces covered with selected dielectric coatings: (i) the high energy spectrum, consisting of photons with wavelengths shorter than ~500nm, is used to generate hydrogen from water photolysis, (ii) the middle spectrum with wavelengths between ~500nm and ~800nm is used to generate electricity with photovoltaic (PV) arrays and (iii) the long wave spectrum of low energy photons with wavelengths longer than ~800nm is used to generate electricity with a thermally driven Rankine engine (RE). The electricity generated by PV and RE is employed to generate additional hydrogen by electrolysis and to drive auxiliary devices within the system. A model is developed based on conservation equations and transport equations applied for each essential component of the system. The model allows for assessment of system performance and the comparison with other solar hydrogen production systems. A case study for an oil sands exploitation area where sulfurous aqueous wastes and hydrogen demand exist - Calgary (Alberta) - is presented. A solar tower configuration is selected as the best choice for a large scale system with 500MW light harvesting heliostat field. Hourly predictions of system output are obtained. The devised system requires 5526acres of land for the solar field and produces 41.4t hydrogen per day. If a conventional solar tower would be used instead which generates power and is coupled to a water electrolysis system the hydrogen production is lower, namely 28.7t/day. An economic scenario is considered by assuming that the co-produced sulfur and hydrogen are both valorized on the market for 25years with a levelized price of 1.65$/kg out of which 10% represents operation and maintenance costs. It is shown that the system is feasible provided that the required equity investment of capital is inferior to M$ 500. [ABSTRACT FROM AUTHOR]

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]

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]

SUMMARY This paper performs a thermodynamic analysis of a modified dual photo-electrochemical cell for water electrolysis, previously developed by Grätzel. In a typical Grätzel cell, a semi-transparent photo-electrode is used in conjunction with a dye photo-sensitized cell to generate a bias voltage necessary to overcome the inherent over-potentials caused by irreversibilities within the cell. The modified method implements hybrid photo-catalysis instead of heterogeneous catalysis. In the hybrid photo-catalysis approach, both homogeneous and heterogeneous photo-catalysts are used to enhance the speed of the water splitting reaction and to widen the portion of the solar radiation spectrum for the process. The dual cell consists of two tandem units. The first unit is a photo-electrolysis cell exposed to solar radiation (at both cathodic and anodic sides) via a transparent window, whereas the second unit is a dye-sensitized solar cell, which assists the photo-electrolysis cell. In the cathodic solution, there are dissolved Brewer-type supra-molecular complexes for photo-catalytic water reduction to generate hydrogen. They absorb solar radiation in the upper visible spectrum and dislocate multiple electrons at the active center. The complexes accept electrons donated from a GaP-based semi-transparent photo-cathode. The remaining un-absorbed radiation (mainly in the infrared range) crosses the semitransparent counter-electrode and the back glass. It is absorbed by a solar thermal collector for enhancing the solar radiation utilization by co-generating low-grade heat. The tandem cell with hybrid photo-catalysis has promising potential of improved solar radiation utilization. This paper analyzes the system efficiency and shows that 4% energy efficiency can be obtained for hydrogen generation. About 20% of the incident solar spectrum can be captured by the cell and used for hydrogen generation. Around 60% of solar radiation is recovered in the form of heat on a flat plate solar thermal collector placed behind the cell. The influence of catalyst concentration and pH also is studied. The device forms a four-gap solar absorber system, which is coupled to a cogeneration sub-system for heating, so the solar energy utilization is maximized. The four-gap system absorbs photons at 1.6, 2.1, 2.3, and 2.7 eV and generates five reversible potentials of 0.42, 0.9, 1.6, 2.1, and 2.3 V. Based on the predicted results, the reaction rate appears to be enhanced with respect to other solar electrolysis cells (such as photo-electrolyzers and a dual photo-electrochemical cell) because homogeneous catalysis enhances the electrode kinetics. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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]

Abstract: In this paper, an experimental study of photo-catalytic water splitting with cadmium sulfide and zinc sulfide photo-catalysts is performed in a dual-cell reactor to investigate the effects of radiation intensity and photo-catalyst concentration on hydrogen and oxygen production rates. Hybridization of the photo-catalytic process is examined with multi catalysts and electric potential bias to enhance the productivity of the reactor and sustain the reaction rate. The hydrogen production of 0.41mmolh−1 with 0.75% (v/v) ZnS is improved by almost 2 times higher than past studies due to illumination of 0.2% (v/v) CdS under 1 sun in a hybrid reactor. The productivity of the reactor is significantly enhanced at light intensities more than 1000Wm−2. The cadmium sulfide catalyst is found to be an inefficient absorbent of light energy, but it shows higher energy and exergy efficiencies compared with ZnS photo-catalysts in a light-driven water splitting process. [Copyright &y& Elsevier]

Abstract: In this paper, we propose an integrated system, consisting of a heliostat field, a steam cycle, an organic Rankine cycle (ORC) and an electrolyzer for hydrogen production. Some parameters, such as the heliostat field area and the solar flux are varied to investigate their effect on the power output, the rate of hydrogen produced, and energy and exergy efficiencies of the individual systems and the overall system. An optimization study using direct search method is also carried out to obtain the highest energy and exergy efficiencies and rate of hydrogen produced by choosing several independent variables. The results show that the power and rate of hydrogen produced increase with increase in the heliostat field area and the solar flux. The rate of hydrogen produced increases from 0.006 kg/s to 0.063 kg/s with increase in the heliostat field area from 8000 m2 to 50,000 m2. Moreover, when the solar flux is increased from 400 W/m2 to 1200 W/m2, the rate of hydrogen produced increases from 0.005 kg/s to 0.018 kg/s. The optimization study yields maximum energy and exergy efficiencies and the rate of hydrogen produced of 18.74%, 39.55% and 1571 L/s, respectively. [Copyright &y& Elsevier]

Abstract: In this paper, a new hybrid system for hydrogen production via solar energy is developed and analyzed. In order to decompose water into hydrogen and oxygen without the net consumption of additional reactants, a steady stream of reacting materials must be maintained in consecutive reaction processes, to avoid reactant replenishment or additional energy input to facilitate the reaction. The system comprises two reactors, which are connected through a proton conducting membrane. Oxidative and reductive quenching pathways are developed for the water reduction and oxidation reactions. Supramolecular complexes [{(bpy)2Ru(dpp)}2RhBr2] (PF6)5 are employed as the photo-catalysts, and an external electric power supply is used to enhance the photochemical reaction. A light driven proton pump is used to increase the photochemical efficiency of both O2 and H2 production reactions. The energy and exergy efficiencies at a system level are analyzed and discussed. The maximum energy conversion of the system can be improved up to 14% by incorporating design modification that yield a corresponding 25% improvement in the exergy efficiency. [Copyright &y& Elsevier]

SUMMARY In this paper, the exergy interactions, environmental impact in terms of CO2 mitigation, and the economics of small-capacity concentrated solar power-driven heat engines for power and heat generation are analysed for residential applications. Starting from a base case study that assumes mass production in Ontario, it is shown that the investment in such a system, making use of a heat engine and having 9 m2 of aperture area, could be about CN$10 000 for a peak electrical efficiency of 18% and thermal efficiency of 75%. The average CO2 mitigation due to combined savings in electricity and heat is ∼0.3 kgCO2 kWh−1, a figure 3-4 times larger than for photovoltaic panels. If 25% government subsidy to the investment is provided, the payback period becomes 21.6 years. Additionally, if the financing benefits from a feed-in-tariff program (at 25% electrical sell-back to the grid) and deductions from CO2 tax are realized, then the payback time drops to 11.3 years. These results are obtained for a conservative scenario of 5.5% annual incremental increase in energy price. For the moderate consideration of all factors, it is shown that within the financial savings over the entire lifecycle, 7% are due to carbon tax, 30% are due to electrical production and the largest amount, 63%, is the result of reducing the natural gas heating capacity with solar heating from the proposed system. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this research study, a new solar energy-based integrated system is developed for treating industrial brine wastewater. An integrated solar-powered evaporation and membrane-based water treatment technique is utilized. Both forced convection as well as falling film evaporators are incorporated to treat high-concentration rejected brine. The system performance is assessed through a comprehensive thermodynamic investigation at varying operating parameters. The energetic performance is evaluated to vary from 12.5% to 15.9% across the year. Furthermore, the peak efficiency in terms of exergy is found to be 11.1%. Also, the membrane-based wastewater treatment subsystem is found to entail an energetic performance of 73.3% and an exergetic performance of 34.6% in terms of efficiencies. Moreover, an energetic performance of 15.4% and an exergetic performance of 2.9% is found for the evaporation-based subsystem. The exergy destructions in each system component are evaluated and the power generation subsystem is determined to have the highest exergy destruction rate of 15.4 MW. To investigate the effects of varying design parameters and operating conditions on the system performance, several parametric studies are also performed. • A new solar energy-based system developed for treating industrial brine wastewater. • Both evaporation and membrane-based water treatment techniques utilized. • Energy efficiency of the overall system varies between 12.5% and 15.9% annually. • Peak exergy efficiency of the overall system found to be 11.1%. [ABSTRACT FROM AUTHOR]

• New renewable hydrogen production system utilizing rice husk biomass. • Multigeneration of clean hydrogen, cooling, freshwater and electricity. • Peak hydrogen production rate reaches 0.3 kg/s. • Overall performance entails energetic and exergetic ratios of 46.8% and 47.8%. A new solar energy-based rice husk gasification system is introduced that produces renewable hydrogen as well as cooling, freshwater and electricity. The hydrogen production rate under design operating conditions is 0.0603 kg/s. Also, the peak rate of hydrogen production at a higher biomass feed rate of 5 kg/s is evaluated to be 0.3 kg/s. Moreover, the performance of the system introduced is evaluated through comprehensive thermodynamic analyses. The overall design efficiency considering energetic performance is 46.8% and the corresponding exergetic efficiency becomes 47.8%. In addition to this, the net rate of energy production attained by the combined cycle is 12.9 MW. Also, the system introduced provides a rate of cooling of 911.4 kW and a freshwater production rate of 410.9 kg/s. Higher steam to biomass and lower oxygen to feed ratios are found to improve system performances. Several other sensitivity analyses are conducted to investigate the performance under varying conditions. [ABSTRACT FROM AUTHOR]

This paper presents a novel system of adding clean hydrogen to the natural gas for more effective and more efficient combustion. The proposed system includes a wind-photovoltaic hybrid system where both wind and solar energy sources are simultaneously utilized. A partial amount of electrical power produced by the wind turbines, PEM fuel cell and PV array is fed to the PEM electrolyser while the additional electricity is supplied to the community for use. In the hydrogen-natural gas blends, the fraction of hydrogen is taken from 0% to 20%, respectively, and the natural gas is reduced from 100% to 80% simultaneously to explore hydrogen addition effect in the combustion process. Although natural gas is cleaner than other fossil fuels, adding hydrogen to the natural gas makes it much cleaner and more environmental friendly. The blends of natural gas and hydrogen helps increase the combustion efficiency, decrease oxygen and reduce the emissions, in particular CO 2. The results further reveal that the energetic efficiency of the combustion unit rises from 84.83% to 94.83% while the exergetic efficiency rises from 62.52% to 70.16% with the rise in hydrogen fraction from 0% to 20%. It is also found that the CO 2 emissions decrease with the rise in hydrogen fraction in hydrogen-natural gas blends. • It presents a novel system of adding hydrogen to the natural gas for combustion. • It includes wind-photovoltaic hybrid system where both solar and wind sources are used. • In the hydrogen-natural gas blends, the hydrogen fraction is taken from 0% to 20%. • The energy efficiency of combustion rises from 84.83% to 94.83% with hydrogen addition. • The CO 2 emissions decrease with the rise in H 2 fraction in hydrogen-natural gas blends. [ABSTRACT FROM AUTHOR]

In the present study, a new ammonia synthesis and fuel cell system integrated with solar energy is developed. The excess energy from a solar photo-voltaic plant is utilized for ammonia synthesis, which acts as an energy storage medium. Two different locations in Canada are considered for system modelling and simulation. The thermodynamic performance of the developed system is analyzed on a transient basis taking into account the variations in solar intensities across the year. The maximum energetic performance evaluated in terms of energy efficiency is 15.72%. Also, the peak exergetic efficiency of the solar-based system is determined as 16.55%. In addition, the daily discharge time capacity is found to reach 8.9 h at the peak. Furthermore, the ammonia synthesis rate obtains a value of 64.8 mol/s at the peak synthesis rate. The daily capacity of energy discharge entails the maximum value of 8502.4 kWh. The dynamic simulation results of each subsystem are discussed comprehensively presenting the applicability of the developed system for intermittency mitigation. Image 10 • A new ammonia synthesis and fuel cell system integrated with solar energy. • Maximum energetic performance in terms of efficiency reaches 15.72%. • The peak exergetic efficiency of the solar-based system is determined as 16.55%. • Daily discharge time and energy capacity found to reach 8.9 h and 8502.4 kWh [ABSTRACT FROM AUTHOR]

• New integrated solar-based ammonia synthesis and fuel cell system developed. • Transient simulation of the developed system performed at varying solar intensities. • Overall system energy efficiency varies between 15.68 and 15.83%. • Exergy efficiency of the overall system varies between 16.44 and 16.67%. • Discharge time capacities found to vary between 2.6 and 8.3 h across the year. Ammonia is considered to be a promising energy storage medium that can address the challenges associated with hydrogen. It is essential to investigate the usage of ammonia for energy storage, especially for the applications of intermittent energy resources. Hence, in the present study, a new integrated solar-based ammonia synthesis and fuel cell system is presented. The excess power generated by a solar photovoltaic system is utilized to synthesize ammonia. Furthermore, a direct ammonia fuel cell is employed for electricity production when low solar energy is available. The system is simulated dynamically on the average day of each month and the performance is investigated through thermodynamic energy and exergy tools. The overall exergy efficiency lies in the range of 16.44%-16.67% while the overall energy efficiency during the year varies between 15.68% and 15.83%, respectively. Also, the discharge time capacity is found to vary between 2.6 and 8.3 h. Moreover, the ammonia synthesis rate reaches a peak value of 64.8 mol s−1 during high solar energy availability. In addition, the maximum energy discharge capacity of the system is evaluated to be 7924.2 kWh. Several parametric studies are also conducted, and the performances are studied comprehensively through energy and exergy efficiencies under various conditions. The developed system entails the advantages of high energy density as well as longer storage times as compared to other energy storage methods. [ABSTRACT FROM AUTHOR]

• Concentrated photovoltaic and photoelectrochemical hydrogen reactors are examined. • A spectrum-splitting mirror allows simultaneous electricity and hydrogen generation. • Concentrator, spectrum-splitting mirror, and electrolyser performance is reported. This paper examines the transport phenomena and optimal performance of an integrated concentrated photovoltaic and photoelectrochemical hydrogen reactor. Individual components and the overall system are studied experimentally including the performance of the concentrator, spectrum-splitting mirror, electrolyser, reactor, and photovoltaic module. Integrating the solar concentration with a spectrum-splitting mirror allows simultaneous photovoltaic electricity generation and direct photonic energy conversion to produce hydrogen via electrolytic and photoelectrochemical water splitting. A multi-objective optimization of the integrated system is performed with machine learning and integration of a neural network. This yields a relationship between the system inputs and outputs. The neural network is used to optimize the overall system through a genetic algorithm. Numerical and experimental results are presented and discussed in the paper. [ABSTRACT FROM AUTHOR]

In this article, three different renewable energy methods are considered with wind, ocean thermal energy conversion (OTEC) and solar energy for clean hydrogen production, and Cu-Cl based thermochemical cycle is incorporated into systems to develop potential applications. In the proposed CuCl cycle configuration, the additional heat offered after the thermolysis reactor is recovered to heat the water before reaching the hydrolysis reactor. In the wind energy based hydrogen production system, the maximum exergy destruction rate is found to be 48.3 kW in the wind turbine. The turbine employed to the ocean thermal energy conversion system is found to be undergoing the highest exergy destruction rate of 143.3 kW. The energy and exergy efficiencies of the solar energy based thermochemical CuCl cycle are found to be 32.7% and 33.2% and the maximum exergy destruction rate of 350.69 kW is offered by the thermolysis reactor. The energetically improved configuration of the thermochemical CuCl cycle displays promising results compared to the earlier studies, such as lower heat requirements and higher efficiencies. The study indicates that there is a value to develop a clean OTEC based hydrogen production system and implement for practical applications. Furthermore, some sensitivity analyses are performed to investigate the performance of each system under different operating parameters and discussed. [ABSTRACT FROM AUTHOR]

A new multigeneration system is proposed to utilize solar energy and biomass sources in a combined manner for cleaner production. The useful commodities of electricity, freshwater, cooling, ammonia and hydrogen are produced. A biomass based integrated gasification combined cycle system is used that is integrated with a solar tower thermal power plant. Also, the reverse osmosis entailing saline water treatment system is incorporated. Furthermore, a thermoelectric generator is deployed to generate power through the excess heat contained in the syngas produced. The developed system is analysed and assessed through thermodynamic analyses. The proposed system provides an increase in the overall efficiencies of renewable energy systems through new waste heat recovery approaches. The energy efficiency of the overall system is evaluated as 20.1% and the exergy efficiency of the overall system is determined to be 21.1%. However, the energy efficiency of the solar tower power plant is determined to be 14.7% and the exergy efficiency is found to be 15.6%. The hydrogen and ammonia production rates are 20 g/s and 79 g/s, respectively. A parametric analysis is carried out to assess the effects of varying operating conditions and system parameters on the system efficiencies. • A new integrated system with biomass based integrated gasification combined cycle. • Multigeneration of electricity, cooling, freshwater, hydrogen and ammonia. • Hydrogen and ammonia production capacities of 20 g/s and 79 g/s respectively. • The overall energy and exergy efficiency of the system is 20.1% and 21.1%. [ABSTRACT FROM AUTHOR]

In this study, a novel hybrid thermal energy storage and ammonia fuel cell system is developed and investigated for a solar tower based power plant. An annual analysis of the developed system is performed by considering the monthly average days. Also, the actual power demands as well as the solar intensity changes are taken into account. Thermodynamic approaches of energy and exergy analyses are utilized for system analysis. The energetic efficiency of the proposed power plant varies between 5.3% and 37% while the exergy efficiency ranges between 5.7% and 39%, depending on the corresponding power demands as well as available solar energy. The system simulation results for each month are also described in terms of the specific exergies and enthalpies at the turbine inlets. Furthermore, energy efficiency of the direct ammonia fuel cell is evaluated to be 37% and the exergy efficiency is found to be 34% at the peak power density. At a temperature of 500 °C, a specific thermal energy storage capacity of 266 kJ kg−1 is determined for the hybrid system. • A novel solar tower based power generation system is developed. • A hybrid thermal energy storage and ammonia fuel cell system is introduced. • The energy efficiency of the developed system varies between 5.3% and 37%. • The exergy efficiency of varies between 5.7% and 39%. [ABSTRACT FROM AUTHOR]

In this study, a new solar-based fuel cell-powered oxygenation and ventilation system is presented for COVID-19 patients. Solar energy is utilized to operate the developed system through photovoltaic panels. The method of water splitting is utilized to generate the required oxygen through the operation of a proton exchange membrane water electrolyser. Moreover, the hydrogen produced during water splitting is utilized as fuel to operate the fuel cell system during low solar availability or the absence of solar irradiation. Transient simulations and thermodynamic analyses of the developed system are performed by accounting for the changes in solar radiation intensities during the year. The daily oxygen generation is found to vary between 170.4 kg/day and 614.2 kg/day during the year. Furthermore, the amount of daily hydrogen production varies between 21.3 kg/day and 76.8 kg/day. The peak oxygen generation rate attains a value of 18.6 g/s. Moreover, the water electrolysis subsystem entails daily exergy destruction in the range of 139.9–529.7 kWh. The maximum efficiencies of the developed system are found to be 14.3% energetically and 13.4% exergetically. • Solar and fuel cell-based oxygenation system is presented for COVID-19 patients. • Transient simulations and thermodynamic analyses conducted on the developed system. • Daily hydrogen production varies between 21.3 kg/day and 76.8 kg/day. • Maximum energy and exergy efficiencies of the developed system are 14.3% and 13.4%. [ABSTRACT FROM AUTHOR]

An Energetically Improved Steam-Autothermal Reforming (EISAR) novel concept is proposed in this study, and a novel idea to combine steam methane reforming with CO 2 and steam based autothermal reforming is introduced for practical applications. A urea synthesis unit is also integrated with the proposed system to justify the idea of clean hydrogen production. The CO 2 produced by the steam methane reforming is captured in CO 2 based autothermal reforming and CO 2 produced by the autothermal reforming is captured by urea synthesis system which converts CO 2 into urea by reacting is with ammonia. According to the designed heat management of molten salt, electric power of 4 MW is produced by the steam Rankine cycle which is supplied to a community of 400 households. During the night time, the community of 400 households is fed to be provided with electricity through PEM fuel cell which utilities a part of hydrogen from the storage tank. Both Engineering Equation Solver (EES) and Aspen Plus software packages are employed for system simulation. Several sensitivity studies, cost and carbon emission analyses and multi-objective optimization studies are undertaken for the designed system. The energy and exergy efficiencies for the present are found to be 59.1% and 31.1%, respectively. Furthermore, the results of current analyses and optimization studies are presented and discussed accordingly. • A novel concept of energetically improved steam-autothermal reforming is presented. • Steam methane reforming is combined with two types of autothermal reforming. • Urea synthesis unit in employed to capture produced CO 2 and conversion into urea. • Designed system meets the electrical load for a community of 400 households. • The overall energy and exergy efficiencies are 59.1% and 31.1% respectively. [ABSTRACT FROM AUTHOR]

In this paper, the synergistic effects of advanced oxidization reactions in a combination of TiO 2 photocatalysis are comparatively investigated for hydrogen production and wastewater treatment applications. An experimental study is conducted with a photoelectrochemical reactor under a UV-light source. TiO 2 is selected as the photocatalyst due to the high corrosion resistant nature and ability to form hydroxyl radicals with the interaction with photons. The synergetic effects of advanced oxidization processes (AOPs) such as Fenton, Fenton-like, photocatalysis (TiO 2 /UV) and UV photolysis (H 2 O 2 /UV) are investigated individually and in a combination of each other. The Fenton type reagent in the reactor is formed by anodic sacrificial of stainless-steel electrode with the presence of H 2 O 2. The influences of various parameters, including pH level, type of the electrode and electrolyte and the UV light, on the performance of the combined system are also investigated experimentally. The highest chemical oxygen demand (COD) removal efficiency is observed as 97.9% for the experimental condition which combines UV/TiO 2 , UV/H 2 O 2 and photo-electro Fenton type processes. The maximum hydrogen production rate from the photoelectrolysis of wastewater is obtained as 7.0 mg/Wh for the experimental condition which has the highest rate of photo-electro Fenton type processes. The average enhancement with the presence of UV light on hydrogen production rates and COD removal efficiencies are further calculated to be 3% and 20%, respectively. • Investigation of synergistic effects of AOPs for H 2 production and wastewater treatment processes. • TiO 2 NPs utilization in combination with Fenton reactions for wastewater treatment. • Wastewater treatment systems with simultaneous hydrogen production. [ABSTRACT FROM AUTHOR]

A comparative assessment is presented of two integrated hydrogen energy systems for environmentally-benign houses. The proposed energy systems use a combination of solar photovoltaic arrays and wind turbines to meet the electricity demand of the house. Energy and exergy analyses are used to assess the performance of the proposed systems. The excess electricity produced by these systems is used in the production of hydrogen through water electrolysis. In system 1, the hydrogen produced by electrolysis is utilized via a turbine to produce power during peak periods. In system 2, the hydrogen produced is utilized via a proton exchange membrane hydrogen fuel cell. A comprehensive parametric study is conducted to investigate the effects of some important parameters such as wind speed, ambient temperature, and solar irradiation on the energy and exergy efficiencies of the systems. Cost assessments of these systems are also carried out in terms of the levelized cost of electricity, and net present cost, and the proposed systems are optimized based on these parameters. The overall energy and exergy efficiencies respectively are found to be 20.7% and 21.0% for system 1, and 24.7%, and 18.9% for system 2. The levelized cost of electricity for system 1 is $ 0.431/kWh while it is $ 0.387/kWh for system 2. [ABSTRACT FROM AUTHOR]

In this paper, sensible heat storage (SHS) systems and performance evaluation techniques are studied. A detailed investigation is presented of the availability of SHS techniques for solar thermal applications, selection criteria for SHS systems, the economics of SHS systems,the main issues in evaluating SHS systems, the viability of SHS systems, the environmental impacts of SHS systems and criteria for SHS feasibility studies, as well as energy saving options. In addition to energy and exergy analyses, several definitions of energy and exergy efficiency for the performance of SHS systems are provided with an illustrative example. [ABSTRACT FROM AUTHOR]

The present study focuses on transient energy and exergy analyses of an integrated heliostat field, gas-turbine cycle and organic Rankine cycle system capable of generating power and heat in a carbon-free manner. A parametric study is carried out to ascertain the effect of varying the exit temperature of salt and the pressure ratio (PR) on the network output, rate of heat lost from the receiver, and energy and exergy efficiencies for 365 days of the year and from 10:00 am to 2:00 pm. The results are obtained for the city of Toronto, Canada and indicate that the network output increases from 1481 to 3339 kW with a rise in the exit salt temperature from 1200 to 1600 K. The energy and exergy efficiencies of the integrated system vary from 0.72 to 0.78 and 0.36 to 0.46, respectively, with a rise in the exit salt temperature. The energy and exergy efficiencies vary from 0.68 to 0.73 and 0.35 to 0.39, respectively, with an increase in the PR from 10 to 20. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a method is proposed for reforming fuels to hydrogen using solar energy at distributed locations (industrial sites, residential and commercial buildings fed with natural gas, remote settlements supplied by propane etc). In order to harness solar energy a solar concentrator is used to generate high temperature heat to reform fuels to hydrogen. A typical fuel such as natural gas, propane, methanol, or an atypical fuel such as ammonia or urea can be transported to distributed locations via gas networks or other means. The thermodynamic analysis of the process shows the general reformation reactions for NH3, CH4 and C3H8 as the input fuel by comparison through operational fuel cost and CO2 mitigation indices. Through a cost analysis, cost reduction indices show fuel-usage cost reductions of 10.5%, 22.1%, and 22.2% respectively for the reformation of ammonia, methane, and propane. CO2 mitigation indices show fuel-usage CO2 mitigations of 22.1% and 22.3% for methane and propane respectively, where ammonia reformation eliminates CO2 emission at the fuel-usage stage. The option of reforming ammonia is examined in further detail as proposed cycles for solar energy capture are considered. A mismatch of specific heats from the solar dish is observed between incoming and outgoing streams, allowing a power production system to be included for a more complete energy capture. Further investigation revealed the most advantageous system with a direct expansion turbine being considered rather than an external power cycle such as Brayton or Rankine type cycles. Also, an energy efficiency of approximately 93% is achievable within the reformation cycle. [Copyright &y& Elsevier]

Abstract: The concept of probability density frequency, which is successfully used for analyses of wind speed and outdoor temperature distributions, is now modified and proposed for estimating solar radiation distributions for design and analysis of solar energy systems. In this study, global solar radiation distribution is comprehensively analyzed for photovoltaic (PV) panel and thermal collector systems. In this regard, a case study is conducted with actual global solar irradiation data of the last 15 years recorded by the Turkish State Meteorological Service. It is found that intensity of global solar irradiance greatly affects energy and exergy efficiencies and hence the performance of collectors. [Copyright &y& Elsevier]

Abstract: In this paper, an ammonia–water based Rankine cycle is thermodynamically analyzed for renewable-based power production, e.g. solar, geothermal, biomass, oceanic-thermal, and nuclear as well as industrial waste heat. Due to the nature of the ammonia–water mixture, changes in its concentration allow thermodynamic cycles to adapt to fluctuations in renewable energy sources, which is an important advantage with respect to other working fluids. The non-linearity of the working fluid’s behaviour imposes that each cycle must be optimized based upon several parameters. A model has been developed to optimize the thermodynamic cycle for maximum power output and carry out a parametric study. The lowest temperature state of the system is fixed, and three other parameters are variables of study, namely, maximum system temperature, ammonia concentration and energy ratio, which is a newly introduced parameter. Energy ratio indicates the relative position of the expansion state and is defined in terms of enthalpies. The study is conducted over a concentration range of 0–0.5, the maximum temperature studied varies between 75°C and 350°C for extreme cases, and the energy ratio from saturated liquid to superheated vapour. As a result, the optimal expansion energy ratio is predicted. The cycle efficiencies are drastically affected by the concentrations and temperatures. Depending on the source temperature, the cycle energy efficiency varies between 5% and 35% representing up to 65% of the Carnot limit. The optimal energy ratio has been determined for several concentrations and reported graphically. [ABSTRACT FROM AUTHOR]

Abstract: In this article, a solar-based method of generating hydrogen from the copper–chlorine water-splitting cycle is developed and evaluated. An analysis is performed for solar plants with different hydrogen production capacities at three locations across Canada. Operating parameters of the solar field and the storage units are presented. The thermal efficiency and cost parameters of the hydrogen plant are also examined. A binary mixture of 60% NaNO3 and 40% KNO3 is used as the molten salt for solar energy storage. Different hydrogen production rates are analyzed. Since the solar irradiation in Calgary is much less than Toronto and Sarnia in the winter, it is found that a larger storage unit is required. The size of the storage unit increases for larger hydrogen production rates. The results support the feasibility of solar thermochemical Cu–Cl cycle as a promising and efficient pathway for large-scale production of hydrogen. [ABSTRACT FROM AUTHOR]