The role of hydrogen in the road transportation sector for a sustainable energy system: A case study of Korea

This study analyzes the impact of the introduction of hydrogen as fuel in the road transportation sector of Korea. Since this sector is completely dependent on petroleum and alternative technologies such as fuel cell vehicles, hydrogen is one alternative fuel that could meet the challenges that Korea is facing due to rising oil prices. This study uses a scenarios-based energy economic model including the hydrogen path way as a sub-energy system to explore the energy system of Korea through 2044. This study also constructs six scenarios consisting of three government policies concerning carbon dioxide reduction and two oil price scenarios in order to assess the impact on hydrogen as fuel in the road transportation sector. The results of this study show that in a particular case (high Btu tax and oil prices) the share of hydrogen would reach 76% of the road transportation sector, and hydrogen would be produced mainly from renewable and nuclear resources via electrolysis facilities. It is also revealed that hydrogen is effective at reducing carbon dioxide, improving energy efficiency and contributing to the energy security of Korea.     

Partial substitution of hydrogen for conventional fuel in an aircraft by utilizing unused cargo compartment space

Options are being actively sought in aviation to switch from petroleum-based fuels to alternative fuels, of which hydrogen is a promising candidate, despite challenges associated with its production and storage. The possibility is demonstrated in this study of using hydrogen in place of some mission fuel without making substantial aircraft modifications and while utilizing only available unused baggage space in the lower-deck cargo compartments of aircraft. The environmental impact reduction and weight increase are obtained accounting for a broad range of factors including aircraft model, seat capacity, passenger and baggage load factors, annual landing and take off cycles, container type, and costs of metal hydride and gaseous hydrogen storage units of various sizes. It is found that, while there may be a cost increase, CO₂ emissions are substantially reduced, by 25,000–570,000 tonnes annually in several cases and by up to 1.1 million tonnes annually for the 10 types of aircraft considered. It is also determined that with present technology, despite the low density of hydrogen, the weight of storage systems constitutes more of a challenge than their volume in aviation. Large-body aircraft are found to have more difficulties than the narrow-body aircraft regarding storage system weight. For the most frequently used narrow- and large-body aircraft considered, the number of the available containers within the required limits of weight and volume respectively are found to be 3 and 4 for the B 737-800 aircraft and 2 and 10 for the A 340-300 aircraft. Overall, the combined usage of hydrogen and kerosene investigated here may be feasible in the future, but is a challenging option with present technology and aircraft due to various factors.     

Solar hydrogen production from the thermal splitting of methane in a high temperature solar chemical reactor

This study addresses the single-step thermal decomposition (pyrolysis) of methane without catalysts. The process co-produces hydrogen-rich gas and high-grade carbon black (CB) from concentrated solar energy and methane. It is an unconventional route for potentially cost effective hydrogen production from solar energy without emitting carbon dioxide since solid carbon is sequestered.A high temperature solar chemical reactor has been designed to study the thermal splitting of methane for hydrogen generation. It features a nozzle-type graphite receiver which absorbs the solar power and transfers the heat to the flow of reactant at a temperature that allows dissociation. Theoretical and experimental investigations have been performed to study the performances of the solar reactor. The experimental set-up and effect of operating conditions are described in this paper. In addition, simulation results are presented to interpret the experimental results and to improve the solar reactor concept. The temperature, geometry of the graphite nozzle, gas flow rates, and CH₄ mole fraction have a strong effect on the final chemical conversion of methane. Numerical simulations have shown that a simple tubular receiver is not enough efficient to heat the bulk gas in the central zone, thus limiting the chemical conversion. In that case, the reaction takes place only within a thin region located near the hot graphite wall. The maximum CH₄ conversion (98%) was obtained with an improved nozzle, which allows a more efficient gas heating due to its higher heat exchange area.     

Application of gas-turbine exhaust gases for brackish water desalination: a techno-economic evaluation

During the last 20 years, the electricity generation system of Crete Island has been actually based on the operation of several gas-turbines, presenting an annual utilization factor higher than 50%. Despite the undeniable advantages of modern gas-turbines, one cannot disregard the huge quantities of hot exhausted gases produced, containing almost two thirds of the chemical energy of fuel consumed. On the other hand, the island faces serious water resources insufficiency problems, especially during hot periods of the year. In this context, the island electricity generation utility (Public Power Corporation (PPC)) is planning to allocate the so far unexploited exhausted gases of a recently installed gas-turbine (LM-6000) at the Linoperamata–Heraklion power station to the neighboring municipality of Gaziou. The main idea elaborated in the present study is the techno-economic evaluation of a new desalination plant, utilizing a thermal desalination process and taking advantage of the heat content of the above-mentioned gas-turbine. According to the results obtained, it is almost certain that the proposed desalination plant is able to produce an amount of clean water adequate to cover the local habitants' needs at a moderate cost, not only saving almost 15,000 tones of imported oil per year but also alleviating the local environment from several flue gases.     

Sustainable hydrogen production from steam reforming of bio-oil model compound based on carbon deposition/elimination

Steam reforming of crude bio-oil or some heavy component present in bio-oil is a great challenge for sustainable hydrogen production due to the extensive coke formation and catalyst deactivation. Catalyst regeneration will be an unavoidable operation in this process. In this paper, m-cresol (a model compound derived from bio-oil) was steam reformed on commercial Ni-based catalyst. Two conventional carbon elimination methods for coked catalyst were applied and the results showed that sustainable hydrogen production can be obtained based on carbon deposition/elimination. The carbon deposition can be gasified easily under certain temperature. The activity of regenerated catalyst samples can be nearly recovered as the fresh ones. Under the reaction conditions of 850 °C and steam to carbon ratio 5:1, >66% hydrogen mole fraction, >81% hydrogen yield, and >97% carbon conversion can be achieved based on regenerated catalyst. Catalyst characterization indicated that the loss of active metal can be considered as the main reason for tiny activity drop. Ni redispersion and Fe contamination may be another two factors that influence catalyst activity.     

Cost evaluation of two potential nuclear power plants for hydrogen production

Hydrogen is recognized as one of the most promising alternative fuels to meet the energy demand for the future by providing a carbon-free solution. In regards to hydrogen production, there has been increasing interest to develop, innovate and commercialize more efficient, effective and economic methods, systems and applications. Nuclear based hydrogen production options through electrolysis and thermochemical cycles appear to be potentially attractive and sustainable for the expanding hydrogen sector. In the current study, two potential nuclear power plants, which are planned to be built in Akkuyu and Sinop in Turkey, are evaluated for hydrogen production scenarios and cost aspects. These two plants will employ the pressurized water reactors with the electricity production capacities of 4800 MW (consisting of 4 units of 1200 MW) for Akkuyu nuclear power plant and 4480 MW (consisting of 4 units of 1120 MW) for Sinop nuclear power plant. Each of these plants are expected to cost about 20 billion US dollars. In the present study, these two plants are considered for hydrogen production and their cost evaluations by employing the special software entitled “Hydrogen Economic Evaluation Program (HEEP)” developed by International Atomic Energy Agency (IAEA) which includes numerous options for hydrogen generation, storage and transportation. The costs of capital, fuel, electricity, decommissioning and consumables are calculated and evaluated in detail for hydrogen generation, storage and transportation in Turkey. The results show that the amount of hydrogen cost varies from 3.18 $/kg H₂ to 6.17 $/kg H₂.     

Thermodynamic evaluation of hydrogen production from methane

Exergetic and energetic analysis has been utilized to estimate the effect of process design and conditions on the hydrogen purity and yield, exergetic efficiencies and CO₂ avoided. Methane was chosen as a model compound for evaluating single stage separation. Simple steam reforming was considered as the base – case system. The other chemical processes that were considered were steam reforming with CO₂ capture with and without chemical looping of a reactive carbon dioxide removal agent, and steam gasification with both the Boudouard reaction catalyst and the reactive carbon dioxide removal agent with and without the solids regeneration. The information presented clearly demonstrates the differences in efficiencies between the various chemical looping processes for hydrogen generation. The incremental changes in efficiencies as a function of process parameters such as temperature, steam amount, chemical type and amount were estimated. Energy and exergy losses associated with generation of syngas, separation of hydrogen from CO_x as well as exergetic loss associated with emissions are presented. The optimal conditions for each process by minimizing these losses are presented. The majority of the exergy destruction occurs due to the high irreversibility of chemical reactions. The results of this investigation demonstrate the utility of exergy analysis. The paper provides a procedure for the comparison of various technologies for the production of hydrogen from carbon based materials based on First and Second Law Analysis. In addition, two figures of merit, namely the comparative advantage factor and the sustainable advantage factor have been proposed to compare the various hydrogen production methods using carbonaceous fuels.     

Comparative techno-economic assessment of a large-scale hydrogen transport via liquid transport media

A large-scale point to point hydrogen transport is one strategy for a prospective energy import scenario for certain countries. The case for a hydrogen transport from Australia to Japan has been addressed in several studies. However, most studies lack transparency and detailed insights into the made assumptions thus a fair evaluation of different transport pathways is challenging. To address this issue, we developed a model where a large-scale point to point hydrogen transport of liquid hydrogen is compared with the transport via liquid organic hydrogen carrier (LOHC), namely via methyl cyclohexane and hydrogenated dibenzyl toluene. We analyzed, where energy is required along the different pathways, where hydrogen losses do occur and how the costs are put together. Furthermore, the influence of hydrogen feed costs is also considered. For hydrogen production costs of 5 €₂₀₁₈/kg_H2 the total delivery costs are in the range of 6.40– 8.10 €₂₀₁₈/kg_H2.     

Idea,process and analyses of hydrogen production from atmospheric pollutant

With the considerable amounts of Sulfur dioxide (SO₂) discharged from the sulfuric acid production unit of the Tunisian Chemical Group (TCG), questions have arisen regarding the treatment of this very dangerous atmospheric pollutant which is crucial. Here, we used SO₂ to produce hydrogen. Sulfur dioxide was fed into a PEM electrolysis, the dissolved SO₂ was oxidized at the anode to produce sulfuric acid, whereas hydrogen was produced at the cathode. By measurements on site complemented by mass balances, we determined the quantities of sulfur dioxide regenerated in the atmosphere. We focused on the startup stage which is the most polluting as the amount of sulfur dioxide generated during this step is enormous. By simulation with Aspen Plus we found that two processes were possible to realize this idea; one with absorption and the other with compression. The same software was used to determine the operating parameters that can run the processes, taking into account the permissible level of SO₂ released into the atmosphere and the production of the highest amount of hydrogen. After a comparative study between the two processes, we selected the process with absorption. An exergetic study was conducted. The exergy loss of the absorption process was equivalent to 563 kJ/mol of H₂. This amount is low compared to other methods. The results show that the new process has the highest exergy efficiency (η_Ex = 90%). This was achieved through Life Cycle Analyses (LCA) which showed that the process with absorption had the highest impact on marine aquatic Eco-toxicity, whereas other impact categories were relatively insignificant.     

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.     

Modeling hydrogen production for injection into the natural gas grid: Balance between production,demand and storage

For hydrogen injection into the natural gas grid a model has been developed to obtain a balance between production, demand and storage. Due to the relation between atmospheric temperature and natural gas demand, the variation in the gas demand is very large. Consequently, in case of a more or less constant mole fraction of hydrogen in natural gas the demand for hydrogen will also vary considerably. Injection of ten percent hydrogen into the natural gas (in The Netherlands) requires already the production of about two billion cubic meters of hydrogen per year. Considering the variation in demand, most probably large-scale storage of hydrogen is needed because the flexibility in production is limited for economic and technical reasons. On the other hand, storage of hydrogen will also increase the costs. In this paper, we report on the balance between hydrogen production, demand and storage. A number of variables for controlling the production will be taken into consideration. Also the possibility of production without a buffer will be discussed.     

A study of combined biomass gasification and electrolysis for hydrogen production

An integrated system for the production of hydrogen by gasification of biomass and electrolysis of water has been designed and cost estimated. The electrolyser provides part of the hydrogen product as well as the oxygen required for the oxygen blown gasifier. The production cost was estimated to 39 SEK/kg H₂ at an annual production rate of 15?000 ton, assuming 10% interest rate and an economic lifetime of 15 years. Employing gasification only to produce the same amount of hydrogen, leads to a cost figure of 37 SEK/kg H₂, and for an electrolyser only a production cost of 41 SEK/kg H₂. The distribution of capital and operating cost is quite different for the three options and a sensitivity analyses was performed for all of these. However, the lowest cost hydrogen produced with either method is at least twice as expensive as hydrogen from natural gas steam reforming.     

A review of catalytic hydrogen production processes from biomass

Hydrogen is believed to be critical for the energy and environmental sustainability. Hydrogen is a clean energy carrier which can be used for transportation and stationary power generation. However, hydrogen is not readily available in sufficient quantities and the production cost is still high for transportation purpose. The technical challenges to achieve a stable hydrogen economy include improving process efficiencies, lowering the cost of production and harnessing renewable sources for hydrogen production. Lignocellulosic biomass is one of the most abundant forms of renewable resource available. Currently there are not many commercial technologies able to produce hydrogen from biomass. This review focuses on the available technologies and recent developments in biomass conversion to hydrogen. Hydrogen production from biomass is discussed as a two stage process – in the first stage raw biomass is converted to hydrogen substrate in either gas, liquid or solid phase. In the second stage these substrates are catalytically converted to hydrogen.     

Performance evaluation of hydrogen production based on off-peak electric energy of the nuclear power plant

The article investigates the efficiency of commercial hydrogen production by water electrolysis on the base of NPP excess energy with its additional purification higher than 99.9999%, considering its transport. The competitive high purity hydrogen release price has been determined as compared to the market price. Besides, the use of high duty electrolysis plants has been suggested. Moreover, the advantages of water electrolysis cyclic operation while consuming electric energy from NPP as compared to the continuous mode have been presented in the paper.     

Efficient photocatalytic hydrogen production from water over a CuO and carbon fiber comodified TiO2 nanocomposite photocatalyst

An efficient composite catalyst, CuO/CF/TiO₂ (where CF represents catalytic grown carbon fiber and TiO₂ is the commercial product P25), is prepared with a wet impregnation and calcination process and is applied in the photo stimulated catalytic water splitting. The modification of TiO₂ with CuO, serving as the H₂ evolution cocatalyst, and carbon fiber, behaving as the electron transporter, enhances greatly the overall activity of the material. The activity of CuO/CF/TiO₂ with 1 wt% CF is 45 times higher than that of TiO₂ and 2 times higher than that of CuO/TiO₂. CF and CuO play a synergistic role in decreasing the recombination rate of the photogenerated carriers in TiO₂ bulk phase. The CF in the composite catalyst extends the reaction range, and makes the reaction proceeds on both the surface of CuO intimately contacting with TiO₂ particles and the surfaces of the CuO particles which do not in contact with TiO₂ but in contact with CF.     

Exergoeconomic analysis of hydrogen production using a standalone high-temperature electrolyzer

The conventional hydrogen production methods, primarily steam methane reforming and coal gasification, produce massive amounts of greenhouse gas emissions which significantly cause impacts on the environment. An alternative hydrogen production method is high-temperature electrolysis using Solid Oxide Electrolyzer that combines both high conversion efficiency and saleable high purity hydrogen production. The produced hydrogen can feed the various industrial processes at different scales in addition to offering an environmentally friendly storage option. The scope of this paper is to examine the economic feasibility of this technology through the utilization of the exergoeconomic concept, which traces the flow of exergy through the system and price both waste and products. Therefore, a standalone solid oxide electrolyzer of a 1MWe is considered for hydrogen production using renewably generated electricity. Having the detailed exergy analysis conducted in earlier studies, the focus of this article is on the costing of each exergy stream to determine the exergy cost and the potential changes outcomes as a result of the system operating or design parameters optimization. It is found that the cost of hydrogen production through the modular high-temperature electrolyzer varies between $3-$9/kg with an average of about $5.7/kg, respectively.     

Production of hydrogen by Enterobacter aerogenes in an immobilized cell reactor

The production of hydrogen from glucose by using Enterobacter aerogenes ATCC 13048 (E. aerogenes) in an immobilized cell reactor (ICR) was investigated. The effect of several factors, such as the glucose concentration, feed flow rate, and fermentation time were examined. The highest amount of hydrogen (9.44 mmol H₂/g glucose) was obtained at a glucose concentration of 8 g/L, flow rate of 0.5 mL/min, retention time of 24 h and at a temperature of 30 °C. Meanwhile, the highest amount of carbon dioxide (1.68 mmol CO₂/g glucose) was obtained at a glucose concentration of 10 g/L, flow rate of 0.7 mL/min, hydraulic retention time of 24 h and at a temperature of 30 °C. The hydrogen and carbon dioxide production were affected by glucose concentration, hydraulic retention time (HRT) and fermentation time. This study showed that the ICR was a very efficient method for the production of hydrogen and carbon dioxide gases.     

Plant sizing and evaluation of hydrogen production costs from advanced processes coupled to a nuclear heat source: Part II: Hybrid-sulphur cycle

Hydrogen demand is already strong. It should significantly increase in the next few years due to the refinery industry's growing needs and new applications such as synthetic fuel or biofuel production. To meet the demand advanced processes are being developed throughout the world in a sustainability context. Among the most studied ones are thermochemical cycles: the sulphur–iodine and hybrid-sulphur cycles.