An assessment on hydrogen production using central receiver solar systems

An assessment is presented on hydrogen production using a dedicated central receiver solar system concept coupled to two types of hydrogen producing processes, electrolysis and thermochemical. The study on solar electrolytic hydrogen was carried out using solar electricity and four different electrolytic technologies, namely industrial unipolar 1980 and 1983 technologies, industrial bipolar and solid polymer electrolyte technology. The thermochemical process was the sulphur/iodine cycle which is being developed by General Atomic Co. Systems which is capable of producing about 10⁶ GJ hydrogen per year were developed at the conceptual level and site specific computations were carried out. A general mathematical model was developed to predict the optical and thermal performance of the central receiver system coupled directly to the chemical plant. Cost models were developed for each sub-system based on the database published in the literature. Levelized and delevelized costs of solar hydrogen were then computed.     

An assessment of large-scale solar hydrogen production in Canada

This study presents an assessment on the hydrogen production using a central receiver system coupled to either an electrolyser plant or a thermochemical plant. Systems which are capable of producing 10⁵ and 10⁶ GJ per year thermal energy or about half of this as hydrogen were developed at four locations in Canada: Fort McMurray, London, Moncton and Victoria. For central receiver systems of 10⁵ and 10⁶ GJ per year thermal energy capacity, heliostat fields arranged to the north of the receiver and tower were developed. A code consisting of optical and thermodynamic performance models was developed to simulate the system. For chemical plants, both electrolysis and thermochemical, codes were developed to simulate their thermodynamic performances. Cost models were developed for each subsystem based on the data published in the literature. Two scenarios were used for the heliostat prices: the first with a limited time and production capacity and the second with a quasi-optimized production capacity and production time. Estimates for the costs of hydrogen were then developed. The results indicated that levelized thermal energy costs ranged from $ 17 to $ 55 per GJ, electricity costs ranged from $ 0.2 to $ 0.5 per kWh and hydrogen costs from $ 57 to $ 157 per GJ.     

An overall assessment of hydrogen production by solar water thermolysis

Major schemes in process designs for water thermolysis are described, thermodynamically modelled and rated in view of certain process evaluation parameters. The process in which the product gases are quenched with water and separated at low temperature by solid diffusion methods is found to have the highest overall efficiency. This process is further studied to find the most suitable operating conditions to reach a satisfactory level of hydrogen yield avoiding material problems generally encountered at high temperature levels. Solar self sufficiency is achieved through heat recovery within the process. Hydrogen production rate is increased by 100% upon converting the recovered heat into electricity in a steam turbine and performing water electrolysis. A feasibility analysis is carried out for an industrial size plant module for thermolysis only at a yearly capacity of 172 GJ, and for hybrid operation coupled with unipolar electrolysis at a total capacity of 344 GJ. Experimental results are reported for the study of a reactor module using the solar furnace at the École Polytechnique. The first and second law efficiencies and the cost of hydrogen are determined as 4.11%, 3.39% and $68 GJ⁻¹ for thermolytic operation and as 5.39%, 4.44% and $46 GJ⁻¹ for hybrid operation.     

Feasibility study for hydrogen production using hybrid solar power in Algeria

Hydrogen demand as a clean energy is one of the new energy challenges in the future. Being a very controlled technology, the water electrolysis is more efficient at high temperature level than at low one. This is because of the use of thermal energy which is less expensive than the use of electricity power to produce the hydrogen; the chemical reaction is more activated in these conditions. In this paper, the feasibility of hydrogen production at high temperature electrolyser, using a hybrid solar resource, thermal energy (parabolic trough concentrators) to produce high temperature, steam water and photovoltaic energy for electricity requirements of the HTE, is presented. The described here-after presented in this document guarantees the production of an important quantity of hydrogen at 900 °C. The production rate depends on geographic position, on climatic conditions and on sun radiation. The optimization of the process is strongly related to what preceded these three parameters. Then, we suggest the set up construction in any region allowing maximum extraction of energy based in our simulation results.     

Uncertainty quantification in a hydrogen production system based on the solar hybrid sulfur process

Water splitting through the Hybrid Sulfur (HyS) process powered by solar energy is a promising pathway to the production of green hydrogen. The main challenges to the development of this process are related to the intrinsic variability of the solar resource, which, besides requiring the deployment of innovative process solutions, introduces significant elements of uncertainty in the plant design.In this paper, the Polynomial Chaos Expansion (PCE) method is applied for the uncertainty quantification (UQ) in this kind of systems. In particular, a forward analysis dealing with the evaluation of the output probability distributions is performed. This is carried out in terms of the input probability distributions, and the analysis is focused on how uncertainty is propagated from the input to the output. Moreover, a comparison between the PCE method and the standard Monte Carlo analysis (using the Latin Hypercube Sampling method) is performed. The obtained results show the advantage of the PCE approach in terms of convergence rate and the number of function evaluations. Finally, a sensitivity analysis through Sobol’ indices has been carried out, which highlighted the influence of each variation in the input on the output.     

Exergetic assessment of solar hydrogen production methods

Hydrogen is a sustainable fuel option and one of the potential solutions for the current energy and environmental problems. Its eco-friendly production is really crucial for better environment and sustainable development. In this paper, various types of hydrogen production methods namely solar thermal (high temperature and low temperature), photovoltaic, photoelecrtolysis, biophotolysis etc are discussed. A brief study of various hydrogen production processes have been carried out. Various solar-based hydrogen production processes are assessed and compared for their merits and demerits in terms of exergy efficiency and sustainability factor. For a case study the exergy efficiency of hydrogen production process and the hydrogen system is discussed in terms of sustainability.     

The solar Cristina process for hydrogen production

Hydrogen production using the Cristina process coupled to a dedicated central receiver solar system has been studied. The Cristina process was originally conceived and developed at the Joint Research Center of the European Communities in Ispra to decompose the sulfuric acid and produce the sulfur dioxide necessary for hydrogen production. In the present study, the process has been adopted to an intermittently operating solar heat source to produce the sulfur dioxide during sunshine hours and operate in reverse as a sulfuric acid synthesis process at a required rate to produce high temperature heat during night operation by using a small part of the stored sulfur dioxide. In this manner, the chemical process is operated continuously, hence, thermal inertia and start-up problems have been eliminated.A system has been conceived to produce 10⁶ mole SO₂ per hour, which is coupled to a central receiver solar system producing 10⁶ GJ per year heat operating 2333 hrs per year. The system produces 0.62 × 10⁶ GJ hydrogen per year when coupled to a hydrogen producing step such as Mark 11 or 13 operating 7000 hrs per year and using electric energy supplied from outside.It has been found that the cost of sulfuric acid decomposition by the solar Cristina process is approximately 31 $ per GJ hydrogen. Including the cost of solar heat (approximately 32 $ per GJ hydrogen) and that of hydrogen producing step (approximately 5 $ per GJ hydrogen), the total cost has been estimated to be 68 $ per GJ hydrogen.     

Life cycle assessment of three types of hydrogen production methods using solar energy

A comprehensive life cycle assessment (LCA) is carried out for three methods of hydrogen production by solar energy: hydrogen production by PEM water electrolysis coupling photothermal power generation, hydrogen production by PEM water electrolysis coupling photovoltaic power generation, and hydrogen production by thermochemical water splitting method using S–I cycle coupling solar photothermal technology. The assessment also contains an evaluation of four environmental factors which are global warming potential, acidification potential, ozone depletion potential, and nutrient enrichment potential. After conducting a quantitative analysis of all three methods with environmental factors being considered, a conclusion has been drawn: The global warming potential and the acidification potential of the thermochemical water splitting by S–I cycle coupling solar photothermal technology are 1.02 kg CO₂-eq and 6.56E-3 kg SO₂-eq. And this method has significant advantages in the environmental impact of the whole ecosystem.     

Research and development on membrane IS process for hydrogen production using solar heat

Thermochemical hydrogen production has attracted considerable interest as a clean energy solution to address the challenges of climate change and environmental sustainability. The thermochemical water-splitting iodine-sulfur (IS) process uses heat from nuclear or solar power and thus is a promising next-generation thermochemical hydrogen production method that is independent of fossil fuels and can provide energy security. This paper presents the current state of research and development (R&D) of the IS process based on membrane techniques using solar energy at a medium temperature of 600 °C. Membrane design strategies have the most potential for making the IS process using solar energy highly efficient and economical and are illustrated here in detail. Three aspects of membrane design proposed herein for the IS process have led to a considerable improvement of the total thermal efficiency of the process: membrane reactors, membranes, and reaction catalysts. Experimental studies in the applications of these membrane design techniques to the Bunsen reaction, sulfuric acid decomposition, and hydrogen iodide decomposition are discussed.     

Development of the once-through hybrid sulfur process for nuclear hydrogen production

The Once-through Hybrid Sulfur (Ot-HyS) process, proposed in this work, produces hydrogen using the same Sulfur dioxide Depolarized water Electrolysis (SDE) process found in the original Hybrid Sulfur cycle (HyS). In the process proposed here, the Sulfuric Acid Decomposition (SAD) process in the HyS procedure is replaced with the well-established sulfur combustion process. First, a flow sheet for the Ot-HyS process was developed by referring to existing facilities and to the work done by the Savannah River National Laboratory (SRNL) under their reasonable assumptions. The process was then simulated using Aspen Plus with appropriate thermodynamic models. It was demonstrated that the Ot-HyS process has higher net thermal efficiency, as well as other advantages, over competing benchmark processes. The net thermal efficiency of the Ot-HyS process is 47.1% (based on LHV) and 55.7% (based on HHV) assuming 33.3% thermal-to-electric conversion efficiency of a nuclear power plant with no consideration given to the work for the air separation. Hydrogen produced through the Ot-HyS process would be used as off-peak electricity storage, to relieve the burden of load-following and could help to expand applications of nuclear energy, which is regarded as a ’sustainable development’ technology.     

Methanol production using hydrogen from concentrated solar energy

Concentrated solar thermal technology is considered a very promising renewable energy technology due to its capability of producing heat and electricity and of its straightforward coupling to thermal storage devices. Conventionally, this approach is mostly used for power generation. When coupled with the right conversion process, it can be also used to produce methanol. Indeed methanol is a good alternative fuel for high compression ratio engines. Its high burning velocity and the large expansion occurring during combustion leads to higher efficiency compared to operation with conventional fuels. This study is focused on the system level modeling of methanol production using hydrogen and carbon monoxide produced with cerium oxide solar thermochemical cycle which is expected to be CO₂ free. A techno-economic assessment of the overall process is done for the first time. The thermochemical redox cycle is operated in a solar receiver-reactor with concentrated solar heat to produce hydrogen and carbon monoxide as the main constituents of synthesis gas. Afterwards, the synthesis gas is turned into methanol whereas the methanol production process is CO₂ free. The production pathway was modeled and simulations were carried out using process simulation software for MW-scale methanol production plant. The methanol production from synthesis gas utilizes plug-flow reactor. Optimum parameters of reactors are calculated. The solar methanol production plant is designed for the location Almeria, Spain. To assess the plant, economic analysis has been carried out. The results of the simulation show that it is possible to produce 27.81 million liter methanol with a 350 MW_th solar tower plant. It is found out that to operate this plant at base case scenario, 880685 m² of mirror's facets are needed with a solar tower height of 220 m. In this scenario a production cost of 1.14 €/l Methanol is predicted.     

Prospects for solar only operation of the hybrid sulphur cycle for hydrogen production

The hybrid sulphur process is one of the most promising thermochemical water splitting cycles for large scale hydrogen production. While the process includes an electrolysis step, the use of sulphur dioxide in the electrolyser significantly reduces the electrical demand compared to conventional alkaline electrolysis. Solar operation of the cycle with zero emissions is possible if the electricity for the electrolyser and the high temperature thermal energy to complete the cycle are provided by solar technologies.This paper explores the possible use of photovoltaics (PV) to supply the electrical demand and examines a number of configurations. Production costs are determined for several scenarios and compared with base cases using conventional technologies. The hybrid sulphur cycle has promise in the medium term as a viable zero carbon production process if PV power is used to supply the electrolyser. However, the viability of this process is dependent on a market for hydrogen and a significant reduction in PV costs to around $1/W_p.     

An overview of hydrogen gas production from solar energy

Hydrogen production plays a very important role in the development of hydrogen economy.Hydrogen gas production through solar energy which is abundant, clean and renewable is one of the promising hydrogen production approaches. This article overviews the available technologies for hydrogen generation using solar energy as main source.Photochemical, electrochemical and thermochemical processes for producing hydrogen with solar energy are analyzed from a technological environmental and economical point of view. It is concluded that developments of improved processes for hydrogen production via solar resource are likely to continue in order to reach competitive hydrogen production costs. Hybrid thermochemical processes where hydrocarbons are exclusively used as chemical reactants for the production of syngas and the concentrated solar radiation is used as a heat source represent one of the most promising alternatives: they combine conventional and renewable energy representing a proper transition towards a solar hydrogen economy.     

Exergetic life cycle assessment of a hydrogen production process

Exergetic life cycle assessment (ExLCA) is applied with life cycle assessment (LCA) to a hydrogen production process. This comparative environmental study examines a nuclear-based hydrogen production via thermochemical water splitting using a copper–chlorine cycle. LCA, which is an analytical tool to identify, quantify and decrease the overall environmental impact of a system or a product, is extended to ExLCA. Exergy efficiencies and air pollution emissions are evaluated for all process steps, including the uranium processing, nuclear and hydrogen production plants. LCA results are presented in four categories: acidification potential, eutrophication potential, global warming potential and ozone depletion potential. A parametric study is performed for various plant lifetimes. The ExLCA results indicate that the greatest irreversibility is caused by uranium processing. The primary contributor of the life cycle irreversibility of the nuclear-based hydrogen production process is fuel (uranium) processing, for which the exergy efficiency is 26.7% and the exergy destruction is 2916.3 MJ. The lowest global warming potential per megajoule exergy of hydrogen is 5.65 g CO₂-eq achieved a plant capacity of 125,000 kg H₂/day. The corresponding value for a plant capacity of 62,500 kg H₂/day is 5.75 g CO₂-eq.     

Operational strategy of a two-step thermochemical process for solar hydrogen production

A two-step thermochemical cycle process for solar hydrogen production from water has been developed using ferrite-based redox systems at moderate temperatures. The cycle offers promising properties concerning thermodynamics and efficiency and produces pure hydrogen without need for product separation.     

Development and assessment of a solar,wind and hydrogen hybrid trigeneration system

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.     

Performance assessment of an electrochemical hydrogen production and storage system for solar hydrogen refueling station

This paper investigates the performance of a hydrogen refueling system that consists of a polymer electrolyte membrane electrolyzer integrated with photovoltaic arrays, and an electrochemical compressor to increase the hydrogen pressure. The energetic and exergetic performance of the hydrogen refueling station is analyzed at different working conditions. The exergy cost of hydrogen production is studied in three different case scenarios; that consist of i) off-grid station with the photovoltaic system and a battery bank to supply the required electric power, ii) on-grid station but the required power is supplied by the electric grid only when solar energy is not available and iii) on-grid station without energy storage. The efficiency of the station significantly increases when the electric grid empowers the system. The maximum energy and exergy efficiencies of the photovoltaic system at solar irradiation of 850 W m-2 are 13.57% and 14.51%, respectively. The exergy cost of hydrogen production in the on-grid station with energy storage is almost 30% higher than the off-grid station. Moreover, the exergy cost of hydrogen in the on-grid station without energy storage is almost 4 times higher than the off-grid station and the energy and exergy efficiencies are considerably higher.     

Solar thermochemical process for hydrogen production using ferrites

A two-step water splitting process using the ZnFe₂O₄/Zn/Fe₃O₄ reaction system was proposed for H₂ generation utilizing concentrated solar heat. The mixture of Zn and Fe₃O₄ was heated to 873 K in flowing steam with an Ar carrier gas, and the H₂ gas was generated at 93.4% of the theoretical yield for the reaction of 3Zn+2Fe₃O₄+4H₂O=3ZnFe₂O₄+4H₂ (H₂ generation step). The XRD and Mössbauer spectroscopy showed that the Zn‐submitted ferrite (Zn_xFe_3−xO₄; 0.2≤x≤1) (main solid product) and ZnO (minor) were formed in the solid products after the H₂ generation reaction. The ZnFe₂O₄ product, which was formed after the H₂ generation step during the two-step water splitting process with the ZnFe₂O₄/Zn/Fe₃O₄ system, could be decomposed into Zn (and ZnO) and Fe₃O₄ by the Xe beam irradiation at 1900 K after 3 min with a 67.8% yield for the reaction of 3ZnFe₂O₄=3Zn+2Fe₃O₄+2O₂ (O₂ releasing step=solar thermal step).     

An innovative approach for geothermal-wind hybrid comprehensive energy system and hydrogen production modeling/process analysis

In this paper, the energy, exergy, economic, environmental, steady-state, and process performance modeling/analysis of hybrid renewable energy (RE) based multigeneration system is presented. Beyond the design/performance analysis of an innovative hybrid RE system, this study is novel as it proposes a new methodology for determining the overall process energy and exergy efficiency of multigeneration systems. This novel method integrates EnergPLAN simulation program with EES and Matlab. It considers both the steady-state and the process performance of the modeled system on hourly timesteps in order to determine the overall efficiencies. Based on the proposed new method, it is observed that the overall process thermodynamic efficiencies of a hybrid renewable energy-based multigeneration system are different from its steady-state efficiencies. The overall energy and exergy efficiencies reduce from 81.01% and 52.52% (in steady-state condition) to 58.6% and 39.33% (when considering a one-year process performance). The integration of the hot water production with the multigeneration system enhanced the overall thermodynamic efficiencies in steady-state conditions. The Kalina system produces a total work output of 1171 kW with a thermal and exergy efficiency of 12.23% and 52% respectively while the wind turbine system produces 1297 kW of electricity in steady-state condition and it has the same thermal/exergy efficiency (72%). The economic analysis showed that the Levelized cost of electricity (LCOE) of the geothermal energy-based Kalina system is 0.0103 $/kWh. The greenhouse gas emission reduction analysis showed that the proposed system will save between 1,411,480 kg/yr and 3,518,760 kg/yr of greenhouse gases from being emitted into the atmosphere yearly. The multigeneration system designed in this study will produce electricity, hydrogen, hot water, cooling effect, and freshwater. Also, battery electric vehicle charging is integrated with process performance analysis of the multigeneration system.     

On the study of hydrogen production from water using solar thermal energy

Theoretical thermal efficiency of hydrogen production by one-step water splitting utilizing solar heat at high temperatures is calculated. Carnot efficiency is assumed for the conversion of effective work input, and the solar collection efficiency is considered for the total energy input. The overall efficiency shows its maximum in the range of temperature between 1500 and 2700 K depending upon the solar concentration ratio and the method of product separation. The technical feasibility of direct splitting method is discussed on the basis of those calculated results.