Hydrogen production from methane and solar energy – Process evaluations and comparison studies

Three conventional and novel hydrogen and liquid fuel production schemes, i.e. steam methane reforming (SMR), solar SMR, and hybrid solar-redox processes are investigated in the current study. H₂ (and liquid fuel) productivity, energy conversion efficiency, and associated CO₂ emissions are evaluated based on a consistent set of process conditions and assumptions. The conventional SMR is estimated to be 68.7% efficient (HHV) with 90% CO₂ capture. Integration of solar energy with methane in solar SMR and hybrid solar-redox processes is estimated to result in up to 85% reduction in life-cycle CO₂ emission for hydrogen production as well as 99–122% methane to fuel conversion efficiency. Compared to the reforming-based schemes, the hybrid solar-redox process offers flexibility and 6.5–8% higher equivalent efficiency for liquid fuel and hydrogen co-production. While a number of operational parameters such as solar absorption efficiency, steam to methane ratio, operating pressure, and steam conversion can affect the process performances, solar energy integrated methane conversion processes have the potential to be efficient and environmentally friendly for hydrogen (and liquid fuel) production.     

Metallic and carbonaceous –based catalysts performance in the solar catalytic decomposition of methane for hydrogen and carbon production

Solar catalytic decomposition of methane (SCDM) was investigated in a solar furnace facility with different catalysts. The aim of this exploratory study was to investigate the potential of the catalytic methane decomposition approach providing the reaction heat via solar energy at different experimental conditions. All experiments conducted pointed out to the simultaneous production of a gas phase composed only by hydrogen and un-reacted methane with a solid product deposited into the catalyst particles varying upon the catalysts used: nanostructured carbons either in form of carbon nanofibers (CNF) or multi-walled carbon nanotubes (MWCNT) were obtained with the metallic catalyst whereas amorphous carbon was produced using a carbonaceous catalyst. The use of catalysts in the solar assisted methane decomposition present some advantages as compared to the high temperature non-catalytic solar methane decomposition route, mainly derived from the use of lower temperatures (600–950 °C): SCDM yields higher reaction rates, provides an enhancement in process efficiency, avoids the formation of other hydrocarbons (100% selectivity to H₂) and increases the quality of the carbonaceous product obtained, when compared to the non-catalytic route.     

Hydrogen as an export commodity – Capital expenditure and energy evaluation of hydrogen carriers

In this paper, we describe a case-study exploring the use of 600 MW of power from New Zealand's Manapouri Power Station to produce hydrogen for export via water electrolysis. Three H₂ carriers were considered: liquid H₂, ammonia, and toluene hydrogenation/methylcyclohexane dehydrogenation. Processes were simulated in Aspen's HYSYS for each of the carriers to determine their associated energy and annualised capital expenditure costs. We found that the total capital investment for all carriers was surprisingly consistent, but with quite different splits between the electrolysis and carrier formation plants. Based on our analysis the energy availability for liquid H₂ ranged from 53.9 to 60.7% depending on the energy cost associated with cryogenic H₂ liquefaction. The energy availability for liquid ammonia was 37.5% after conversion back to H₂, or 53.6% if the ammonia can be used directly as a fuel. For toluene/methylcyclohexane the energy availability was 41.2%. The total of the electricity and annualised capital costs per kg of H₂ ranged from NZ$5.63 to NZ$6.43 for liquid H₂, NZ$6.24 to NZ$8.91 for ammonia and was NZ$7.86 for toluene/methylcyclohexane, using a net electricity cost of NZ$70/MWh. The cost of hydrogen (or energy in the case of direct use ammonia) was more strongly influenced by the efficiency of energy retention than on capital investment, as the electricity costs contributed approximately two thirds of total costs. In the long-term, liquid hydrogen looks to be the most versatile H₂ carrier, but significant infrastructure investment is required.     

Estimation of Hong Kong’s solar energy potential using GIS and remote sensing technologies

This paper studies the use of Remote Sensing (RS) technologies and Geographic Information Systems (GIS) for estimation of city-wide photovoltaic (PV) potential in Hong Kong. It investigates the spatial distribution of cloud coverage through geostationary satellites from the Multi-functional Transport Satellite (MTSAT). The results indicate that a non-prominent spatial variation of cloud cover presides over a majority of Hong Kong territories. Appropriate locations for deploying solar PV panels, such as rooftops, were delineated using RS, GIS, and existing ancillary data. Extraction and filtering of pixels based on a set of criterions were used to identify optimal PV rooftops. This study shows that the summarization of PV potentials in Hong Kong is 2.66 TWh on building rooftops. The methodologies and findings from this study permits detailed spatial estimation of city-wide solar energy potential, and assists the policy-decision process on the use of renewable energy in Hong Kong.     

Prediction,investigation, and assessment of novel tidal–solar hybrid renewable energy system in India by different techniques

In the present scenario, all over the world, electrical energy is produced by conventional or non-renewable energy supply system. These systems produce a large amount of atmospheric pollution. This predicament is principally conquered by the concentrated use of alternative or renewable energy system. The research work reported in the paper shows the profoundness of performance prediction and investigation of solar–tidal integrated renewable energy system using a different optimisation technique. The works on macro-level include a novel tidal–solar system in the coastal area of Cochin, India and modelling of tidal-solar energy system by the HOMER software. Duration of the project is assessed by a project management technique critical path method, optimisation of the HOMER software cost assessment result for the study area using teaching, learning-based optimisation, cuckoo optimisation and through the grasshopper technique, further reliability and life-cycle analysis of the system and result are validated by regression analysis.     

Hydrogen production by Escherichia coli growing in different nutrient media with glycerol: Effects of formate,pH, production kinetics and hydrogenases involved

The Escherichia coli BW25113 or MC4100 wild type parental strains growth and H₂ production kinetics was studied in batch cultures of minimal salt medium (MSM) and peptone medium (PM) at pH of 5.5–7.5 upon glycerol (10 g L^?1) fermentation and formate (0.68 g L^?1) supplementation. The role of formate alone or with glycerol on growth and H₂ production via hydrogenases (Hyd) was investigated in double hyaB hybC (lacking large subunits of Hyd 1 and 2), triple hyaB hybC hycE (lacking large subunits of Hyds 1-3) and sole selC (lacking formate dehydrogenase H) mutants during 24 h bacterial growth. H₂ production was delayed and observed after 24 h bacterial wild type strains growth on MSM. Moreover, it reached the maximal values after 72 h growth at the pH 6.5 and pH 7.5. Biomass formation of the mutants used was inhibited ～3.5 fold compared with wild type, and H₂ production was absent in hyaB hybC hycE and selC mutants upon glycerol utilization on MSM at pHs of 5.5–7.5. Formate inhibited bacterial growth on MSM with glycerol, but enhanced and recovered H₂ production by hybC mutant at pH 7.5. H₂ evolution was delayed at pH 7.5 in PM, but observed and stimulated at pH 6.5 upon glycerol and formate utilization in hyaB hybC mutant. H₂ production was absent in hyaB hybC hycE and selC mutants upon glycerol, formate alone or with glycerol fermentation at pH 6.5 and pH 7.5; formate supplementation had no effect. The results point out E. coli ability to grow and utilize glycerol in MSM with comparably high H₂ yield: as well as they suggest the key role of Hyd-3 at both pH 6.5 and pH 7.5 and the role of Hyd-2 and Hyd-4 at pH 7.5 in H₂ production by E. coli during glycerol fermentation with formate supplementation. The results obtained are novel and might be useful in H₂ production biotechnology development using different nutrient media and glycerol and formate as feedstock.     

Enhancement of energy generation efficiency in industrial facilities by SOFC – SOEC systems with additional hydrogen production

Industry is one of the highest energy consumption sector: some facilities like steelworks, foundries, or paper mills are highly energy-intensive activities. Many countries have already implemented subsidies on energy efficiency in generation and utilisation, with the aim of decreasing overall consumption and energy intensity of gross domestic product. Meanwhile, researchers have increased interest into alternative energy systems to decrease pollution and use of fossil fuels. Hydrogen, in particular, is proposed as a clean alternative energy vector, as it can be used as energy storage mean or to replace fossil fuels, e.g. for transport.This work analyses the re-vamping of the energy generation system of a paper mill by means of reversible solid oxide cells (RSOCs). The aim is not only to increase efficiency on energy generation, but also to create a polygeneration system where hydrogen is produced. Application on a real industrial facility, based in Italy with a production capacity of 60000 t/y of paper, is analysed. First, the current energy system is studied. Then, a novel system based on RSOC is proposed. Each component of the systems (both existing and novel) is defined using operational data, technical datasheet, or models defined with thermodynamic tools. Then, the interaction between them is studied. Primary energy analysis on the novel system is performed, and saving with respect to the current configuration is evaluated. Even if the complexity of the system increases, results show that saving occurs between 2 and 6%. Hydrogen generation is assessed, comparing the RSOC integrated system with proton exchange membrane (PEM) electrolysis, in terms of both primary energy and economics. Results exhibit significant primary energy and good economic performance on hydrogen production with the novel system proposed (hydrogen cost decreases from 10 €/kg to at least 8 €/kg).     

Hydrogen,nitrogen and carbon dioxide production through chemical looping using iron-based oxygen carrier – A Green plant for H2 and N2 production

In order to simulate the performance of pure methane in chemical looping using iron-based oxygen carrier, simultaneously production of three pure streams of hydrogen, nitrogen and carbon dioxide has been investigated. For this purpose, proper operating conditions have been discussed for maximum production of hydrogen, complete consumption of oxygen of inlet air and complete combustion of methane. Professional software is used to simulate the chemical looping reactors and optimize their output streams. Results show that in this process each mole of methane fuel can produce 2.533, 2.65 and 0.99 mol of pure N₂, H₂ and CO₂, respectively which contributes 80.2% energy conversion of CH₄ to H₂. Moreover, in order to consume the whole input fuel and maximize hydrogen production, it is necessary to use a supportive material to improve mechanical property of oxygen carrier particles and optimize temperature of streams by thermal integration of three reactors. Also, due to controllable temperature of three reactors, more flow rate of oxygen carrier particles can be used instead of supportive material while the air flow rate should be justified to produce pure nitrogen. Hence, three chemical looping reactors, beside hydrogen and CO₂ production, can directly produce nitrogen, by means of a process simpler than the conventional technologies like air separation unit.     

The MIND method: A decision support for optimization of industrial energy systems – Principles and case studies

Changes in complex industrial energy systems require adequate tools to be evaluated satisfactorily. The MIND method (Method for analysis of INDustrial energy systems) is a flexible method constructed as decision support for different types of analyses of industrial energy systems. It is based on Mixed Integer Linear Programming (MILP) and developed at Linköping University in Sweden. Several industries, ranging from the food industry to the pulp and paper industry, have hitherto been modelled and analyzed using the MIND method. In this paper the principles regarding the use of the method and the creation of constraints of the modelled system are presented. Two case studies are also included, a dairy and a pulp and paper mill, that focus some measures that can be evaluated using the MIND method, e.g. load shaping, fuel conversion and introduction of energy efficiency measures. The case studies illustrate the use of the method and its strengths and weaknesses. The results from the case studies are related to the main issues stated by the European Commission, such as reduction of greenhouse gas emissions, improvements regarding security of supply and increased use of renewable energy, and show great potential as regards both cost reductions and possible load shifting.     

Energy,environmental and economic comparison of different powertrain/fuel options using well-to-wheels assessment,energy and external costs – European market analysis

The well-to-wheels assessment is widely used in the automotive sector to analyze the efficiency and competitiveness of different powertrain/fuel options. The paper proposes a global index that takes into account both the energy and environmental aspects on an uniform basis, through the assignment of the costs associated to the energy and to the pollutant emissions. The European market is analyzed and other pollutants (NO_x, PM and SO_x) are added to the traditional well-to-wheels evaluations (energy and GHG). The proposed well-to-wheels global index offers a useful place-list that takes into account both energy and environmental aspects and, at the current market conditions, it results that the energy cost prevails (70–85%) over the environmental costs, and among the analyzed external costs, the main contribution is due to the GHG emissions. Natural gas-derived fuels seem to be the most promising. The global index for battery electric vehicle from a European mix are closely linked to the driving range. Conventional biofuels are very critical at present, while significant improvement of the well-to-wheels global index is foreseen for when new generation biofuels will be mature (2030 forecast). In short, even though the proposed global index is not an exhaustive index, it could be a useful tool for decision makers.     

Design and fabrication of biphasic cellular materials with transport properties – A modified bidirectional evolutionary structural optimization procedure and MATLAB program

Heat and mass transfer in macellular materials signifies an important topic of research for a range of advanced applications such as in thermal, aerospace, geotechnical and scaffold tissue engineering etc. Based on the mathematical similarity of various transport problems, this paper proposes a modified bidirectional evolutionary structural optimization (BESO) method for design of biphasic microstructural composites with desirable transport properties. The cellular materials considered herein comprise periodic base cells and the homogenization technique is adopted to determine their effective (bulk) properties. The key is to optimize the topology of base cell model for minimizing the difference between the effective and target transport properties. Numerical examples agree well with the well-known benchmarking microstructures and some of them are prototyped using biphasic solid free-form fabrication (SFF) technology. To facilitate comprehension of the algorithm, a short MATLAB program is provided in the Appendix.     

Hydrogen production using thermochemical water-splitting Iodine–Sulfur process test facility made of industrial structural materials: Engineering solutions to prevent iodine precipitation

A thermochemical water-splitting iodine–sulfur process offers the potential for mass-producing hydrogen at high-efficiency levels, and it uses high-temperature heat sources, including high-temperature gas-cooled reactors, solar heat, and waste heat of industries. The raw material (H₂O) is split into H₂ and O₂ by combining three chemical reactions using sulfur and iodine. Currently, R&D tasks are essential to confirm the integrity of the components that are made of practical structural materials and the stability of hydrogen production in harsh working conditions. A test facility for producing hydrogen was constructed from corrosion-resistant components that are developed using industrial materials. In addition, for stable hydrogen production, technical issues for instrumental improvements (i.e., stable pumping of the hydrogen iodide (HI)–I₂–H₂O solution without locking the shaft seal, prevention of leakage by improving the quality control of glass-lined steel, prevention of I₂ precipitation using a water removal technique in a Bunsen reactor) were solved. The entire process was successfully operated for 150 h at the rate of ca. 30 L/h. The integrity of components made of practical structural materials and the operational stability of the hydrogen production facility in harsh working conditions were demonstrated.     

A 3E,hydrogen production,irrigation, and employment potential assessment of a hybrid energy system for tropical weather conditions – Combination of HOMER software,shannon entropy,and TOPSIS

The increasing threat to environmental sustainability as a result of greenhouse gas (GHG) emissions from fossil fuel base power plants has necessitated the need to find sustainable energy sources to meet the world's energy demands. This study focuses on assessing the potential of a hybrid power plant for the production of electricity, hydrogen for the production of fertilizer for agricultural activities, farmland irrigation, environmental impact as well as its employment potential in northern Ghana. The Shannon entropy weight and TOPSIS multi-criteria decision-making approach were adopted to rank and identify the optimal configuration out of five possible options for the study area. Results from the simulation show that the winning system, i.e., Hydro + Battery system would generate a total electricity of 1,095,679 kWh/year. A cost of electricity of 0.06 $/kWh with an operating cost (OC) of $18,318 was recorded for the winning system. The total produced hydrogen by the optimum configuration is 8816 kg/year at a levelized cost of hydrogen (LCOH) of 4.47 $/kg. The quantity of low-carbon fertilizer that can be produced from the produced hydrogen is also assessed. The optimum configuration also recorded an employment potential of 4 persons in 25 years. A total GHG equivalence of 383.49 metric tons of CO₂ equivalent indicating the level of emissions that will be avoided should the optimum system be used to meet the demands specified in this study was obtained.     

KNO3/NaNO3 – Graphite materials for thermal energy storage at high temperature: Part I. – Elaboration methods and thermal properties

Composites graphite/salt for thermal energy storage at high temperature (～200 °C) have been developed and tested. As at low temperature in the past, graphite has been used to enhance the thermal conductivity of the eutectic system KNO₃/NaNO₃. A new elaboration method has been proposed as an alternative to graphite foams infiltration. It consists of cold-compression of a physical mixing of expanded natural graphite particles and salt powder. Two different compression routes have been investigated: uni-axial compression and isostatic compression. The first part of the paper has been devoted to the analysis of the thermal properties of these new graphite/salt composites. It is proven that cold-compression is a simple and efficient technique for improving the salt thermal conductivity. For instance, graphite amounts between 15 and 20%wt lead to apparent thermal conductivities close to 20 W/m/K (20 times greater than the thermal conductivity of the salt). Furthermore, some advantages in terms of cost and safety are expected because materials elaboration is carried out at room temperature. The second part of the paper is focused on the analyses of the phase transition properties of these graphite/salt composites materials.     

Hydrogen and aromatic production by means of a novel membrane integrated cross flow CCR naphtha reforming process

In this study a new configuration i.e. membrane reactor with Pd/Ag membrane was proposed for catalytic naphtha reforming, and examined through mathematical modeling considering catalyst deactivation. According to complex kinetic of reforming process a new kinetic model including 32 pseudo components with 84 reactions is proposed. Mathematical modeling of this process in continuous catalyst regeneration mode of operation is accomplished in two dimensions (radial and axial) by considering cross flow pattern. To validate the competence of the conventional configuration model, its results are compared with the industrial data. Aromatics and hydrogen production were boosted as a result of hydrogen removal in AMR while light end production was diminished as a consequence of hydrogen separation and higher temperature drop in AMR.