Review and comparison of various hydrogen production methods based on costs and life cycle impact assessment indicators

Hydrogen is a clean, renewable secondary energy source. The development of hydrogen energy is a common goal pursued by many countries to combat the current global warming trend. This paper provides an overview of various technologies for hydrogen production from renewable and non-renewable resources, including fossil fuel or biomass-based hydrogen production, microbial hydrogen production, electrolysis and thermolysis of water and thermochemical cycles. The current status of development, recent advances and challenges of different hydrogen production technologies are also reviewed. Finally, we compared different hydrogen production methods in terms of cost and life cycle environmental impact assessment. The current mainstream approach is to obtain hydrogen from natural gas and coal, although their environmental impact is significant. Electrolysis and thermochemical cycle methods coupled with new energy sources show considerable potential for development in terms of economics and environmental friendliness.     

A comparative life cycle analysis of hydrogen production via thermochemical water splitting using a Cu-Cl cycle

In this paper, a comparative environmental study is reported of the Cu-Cl water-splitting cycle with various other hydrogen production methods: the sulphur-iodine (S-I) water-splitting cycle, high temperature water electrolysis, conventional steam reforming of natural gas and hydrogen production from renewable resources. The investigation uses life cycle assessment (LCA), which is an analytical tool to identify and quantify environmentally critical phases during the life cycle of a system or a product and/or to evaluate and decrease the overall environmental impact of the system or product. The LCA results for the hydrogen production processes indicate that the thermochemical cycles have lower environmental impacts while steam reforming of natural gas has the highest.     

Life cycle assessment of various hydrogen production methods

A comprehensive life cycle assessment (LCA) is reported for five methods of hydrogen production, namely steam reforming of natural gas, coal gasification, water electrolysis via wind and solar electrolysis, and thermochemical water splitting with a Cu–Cl cycle. Carbon dioxide equivalent emissions and energy equivalents of each method are quantified and compared. A case study is presented for a hydrogen fueling station in Toronto, Canada, and nearby hydrogen resources close to the fueling station. In terms of carbon dioxide equivalent emissions, thermochemical water splitting with the Cu–Cl cycle is found to be advantageous over the other methods, followed by wind and solar electrolysis. In terms of hydrogen production capacities, natural gas steam reforming, coal gasification and thermochemical water splitting with the Cu–Cl cycle methods are found to be advantageous over the renewable energy methods.     

Hydrogen production from offshore wind power in South China

Wind power hydrogen production is the direct conversion of electricity generated by wind power into hydrogen through water electrolysis hydrogen production equipment, which produces hydrogen for convenient long-term storage through water electrolysis. With the development of offshore wind power from offshore projects, construction costs continue to rise. Turning power transmission into hydrogen transmission will help reduce the cost of offshore wind power construction. This paper analyses the methods of producing hydrogen from offshore wind power, including alkaline water electrolysis, proton exchange membrane electrolysis of water, and solid oxide electrolysis of water. In addition, this paper outlines economic and cost analyses of hydrogen production from offshore wind power. In the future, with the development and advancement of water electrolysis hydrogen production technology, hydrogen production from offshore wind power could be more economical and practical.     

Life cycle assessment of hydrogen supply chain with special attention on hydrogen refuelling stations

The controversial and highly emotional discussion about biofuels in recent years has shown that greenhouse gas² (GHG) emissions can only be evaluated in an acceptable way by carrying out a full life cycle assessment (LCA) taking the overall life cycle including all necessary pre-chains into consideration. Against this background, the goal of this paper is it to analyse the overall life cycle of a hydrogen production and provision. A state of the art hydrogen refuelling station in Hamburg/Germany opened in February 2012 is therefore taken into consideration. Here at least 50% hydrogen from renewable sources of energy is produced on-site by water electrolysis based on surplus electricity from wind (mainly offshore wind parks) and water. The remaining other 50% of hydrogen to be sold by this station mainly to hydrogen-fuelled buses is provided by trucks from a large-scale production plant where hydrogen is produced from methane or glycerol as a by-product of the biodiesel production. These two pathways are compared within the following explanations with hydrogen production from biomass and from coal. The results show that – with the goal of reducing GHG emissions on a life cycle perspective – hydrogen production based on a water electrolysis fed by electricity from the German electricity mix should be avoided. Steam methane reforming is more promising in terms of GHG reduction but it is still based on a finite fossil fuel. For a climatic sound provision of hydrogen as a fuel electricity from renewable sources of energy like wind or biomass should be used.     

Hydrogen production costs of a polymer electrolyte membrane electrolysis powered by a renewable hybrid system

In this work, a novel approach related to the production of hydrogen using a polymer electrolyte membrane electrolysis powered by a renewable hybrid system is proposed. The investigation is carried out by establishing energy balances in the different components constituting the combined renewable system. A mathematical model to predict the production of electricity and hydrogen is proposed. The discrepancies between the numerical results and those from the literature review do not exceed 7%. The results show that the overall efficiency and the capacity factor of the combined renewable system without thermal storage are 20 and 34%, respectively. The levelized cost of hydrogen also is 6.86 US$/kg. The effect of certain physical parameters such as optical efficiency, water electrolysis temperature, unit electrolysis capital cost and solar multiple on the performance of the combined system is investigated. The results show that the performance of hydrogen production is optimal when the solar installation is three times oversized. The results also show that the levelized cost of hydrogen for the optimal sized is 4.07 US$/kg. Finally, the proposed combined system can produce low cost hydrogen and compete with hybrid sulfur thermochemical cycles, conventional photovoltaic installations, concentrated photovoltaic thermal systems and wind farms developed in all regions of the world.     

Life cycle assessment of nuclear-based hydrogen and ammonia production options: A comparative evaluation

In this study, nuclear energy based hydrogen and ammonia production options ranging from thermochemical cycles to high-temperature electrolysis are comparatively evaluated by means of the life cycle assessment (LCA) tool. Ammonia is produced by extracting nitrogen from air and hydrogen from water and reacting them through nuclear energy. Since production of ammonia contributes about 1% of global greenhouse gas (GHG) emissions, new methods with reduced environmental impacts are under close investigation. The selected ammonia production systems are (i) three step nuclear Cu–Cl thermochemical cycle, (ii) four step nuclear Cu–Cl thermochemical cycle, (iii) five step nuclear Cu–Cl thermochemical cycle, (iv) nuclear energy based electrolysis, and (v) nuclear high temperature electrolysis. The electrolysis units for hydrogen production and a Haber–Bosch process for ammonia synthesis are utilized for the electrolysis-based options while hydrogen is produced thermochemically by means of the process heat available from the nuclear power plants for thermochemical based hydrogen production systems. The LCA results for the selected ammonia production methods show that the nuclear electrolysis based ammonia production method yields lower global warming and climate change impacts while the thermochemical based options yield higher abiotic depletion and acidification values.     

Dynamic simulation and lifecycle assessment of hydrogen fuel cell electric vehicles considering various hydrogen production methods

In this research study, a real model of a hydrogen fuel cell vehicle is simulated using Simcenter Amesim software. The software used for vehicle simulation enabled dynamic simulation, resulting in more precise simulation. Furthermore, considering that fuel cell degradation is one of the significant challenges confronting fuel cell vehicle manufacturers, we examined the impact of fuel cell degradation on the performance of hydrogen vehicles. According to the findings, a hydrogen vehicle with a degraded fuel cell consumes 14.3% more fuel than a fresh fuel cell hydrogen vehicle. A comprehensive life cycle assessment (LCA) is also performed for the designed hydrogen vehicle. The results of the hydrogen vehicle life cycle assessment are compared with a gasoline vehicle to fully understand the effect of hydrogen vehicles in reducing air emissions. The methods considered for hydrogen production included natural gas reforming, electrolysis, and thermochemical water splitting method. Furthermore, because the source of electricity used for electrolysis has a significant impact on the life cycle emission of a hydrogen vehicle, three different power sources were considered in this assessment. Finally, while a hydrogen vehicle with a degraded fuel cell emits lower carbon dioxide (CO₂) than a gasoline vehicle, the emitted CO₂ from this vehicle using hydrogen from electrolysis is approximately 25% higher than that of a new hydrogen vehicle.     

A grey-based group decision-making methodology for the selection of hydrogen technologies in life cycle sustainability perspective

The objective of this research is to develop a grey-based group decision-making methodology for the selection of the best renewable energy technology (including hydrogen) using a life cycle sustainability perspective. The traditional grey relational analysis has been modified to better address the issue of uncertainty. The proposed methodology allows multi-person to participate in the decision-making process and to give linguistic evaluation on the weights of the criteria and the performance of the alternative technologies. In this paper, twelve hydrogen production technologies have been assessed using the proposed methodology, electrolysis of water technology by hydropower has been considered to be the best technology for hydrogen production according to the decision-making group.     

Life cycle environmental impact comparison of solid oxide fuel cells fueled by natural gas,hydrogen, ammonia and methanol for combined heat and power generation

This study aims to provide a comprehensive environmental life cycle assessment of heat and power production through solid oxide fuel cells (SOFCs) fueled by various chemical feeds namely; natural gas, hydrogen, ammonia and methanol. The life cycle assessment (LCA) includes the complete phases from raw material extraction or chemical fuel synthesis to consumption in the electrochemical reaction as a cradle-to-grave approach. The LCA study is performed using GaBi software, where the selected impact assessment methodology is ReCiPe 1.08. The selected environmental impact categories are climate change, fossil depletion, human toxicity, water depletion, particulate matter formation, and photochemical oxidant formation. The production pathways of the feed gases are selected based on the mature technologies as well as emerging water electrolysis via wind electricity. Natural gas is extracted from the wells and processed in the processing plant to be fed to SOFC. Hydrogen is generated by steam methane reforming method using the natural gas in the plant. Methanol is also produced by steam methane reforming and methanol synthesis reaction. Ammonia is synthesized using the hydrogen obtained from steam methane reforming and combined with nitrogen from air in a Haber-Bosch plant. Both hydrogen and ammonia are also produced via wind energy-driven decentralized electrolysis in order to emphasize the cleaner fuel production. The results of this study show that feeding SOFC systems with carbon-free fuels eliminates the greenhouse gas emissions during operation, however additional steps required for natural gas to hydrogen, ammonia and methanol conversion, make the complete process more environmentally problematic. However, if hydrogen and ammonia are produced from renewable sources such as wind-based electricity, the environmental impacts reduce significantly, yielding about 0.05 and 0.16 kg CO₂ eq., respectively, per kWh electricity generation from SOFC.     

Preparation of hydrogen from metals and water without CO2 emissions

Considering the high calorific value and low-carbon characteristics of hydrogen energy, it will play an important role in replacing fossil energy sources. The production of hydrogen from renewable energy sources for electricity generation and electrolysis of water is an important process to obtain green hydrogen compared with classic low-carbon hydrogen production methods. However, the challenges in this process include the high cost of liquefied hydrogen and the difficulty of storing hydrogen on a large scale. In this paper, we propose a new route for hydrogen storage in metals, namely, electricity generation from renewable energy sources, electrolysis to obtain metals, and subsequent hydrogen production from metals and water. Metal monomers facilitate large-scale and long-term storage and transportation, and metals can be used as large-scale hydrogen storage carriers in the future. In this technical route, the reaction between metal and water for hydrogen production is an important link. In this paper, we systematically summarize the research progress, development trend, and challenges in the field of metal to hydrogen production. This study aim to aid in the development of this field.     

Harmonised life-cycle indicators of nuclear-based hydrogen

When comparing the life-cycle environmental performance of hydrogen energy systems, significant concerns arise due to potential methodological inconsistencies between case studies. In this regard, protocols for harmonised life cycle assessment (LCA) of hydrogen energy systems are currently available to mitigate these concerns. These protocols have already been applied to conventional hydrogen from steam methane reforming as well as to a large number of both fossil and renewable hydrogen options, allowing robust comparisons between them. However, harmonised life-cycle indicators of nuclear-based hydrogen options are not yet available in the literature. This study fills this gap by using the recently developed software GreenH₂armony® to calculate the harmonised carbon, energy and acidification footprints of nuclear-based hydrogen produced through different pathways (viz., low-temperature electrolysis, high-temperature electrolysis, and thermochemical cycles). Overall, the harmonised case studies of nuclear-based hydrogen show a generally good performance in terms of carbon footprint and acidification, but an unfavourable performance in terms of non-renewable energy footprint.     

Assessing techno-economic uncertainties in nuclear power-to-X processes: The case of nuclear hydrogen production via water electrolysis

Nuclear assisted low carbon hydrogen production by water electrolysis represents a potential application of nuclear cogeneration towards deep decarbonization of several fossil fuel-dependent industrial sectors. This work builds a probabilistic techno-commercial model of a water electrolysis plant coupled to an existing nuclear reactor for base load operations. The objective is to perform discounted cash flow (DCF) calculations for levelized nuclear hydrogen production cost under input parameter uncertainty. The probability distributions of inputs are used with the Monte Carlo-Latin Hypercube (MC-LH) sampling technique to generate 10⁵ input scenarios and corresponding distribution of the levelized or life cycle hydrogen production cost instead of deterministic point values. Based on current techno-economic conditions, the levelized production costs of electrolytic hydrogen using electricity from large water-cooled nuclear reactors are determined to be US $ 12.205 ± 1.342, 8.384 ± 1.148 and 6.385 ± 1.051/kg H₂ respectively at rated alkaline water electrolyser capacities of 1.25 MW(e), 2.5 MW(e) and 5 MW(e). The corresponding values for PEM water electrolysers are US $ 13.162 ± 1.356, 8.891 ± 1.141 and 6.663 ± 1.057/kg H₂. The potential for flexible nuclear reactor operation and management of power demand uncertainties through nuclear hydrogen cogeneration is also examined through a case study.     

Environmental life cycle feasibility assessment of hydrogen as an automotive fuel in Western Australia

A life cycle assessment has been undertaken in order to determine the environmental feasibility of hydrogen as an automotive fuel in Western Australia. The criterion for environmental feasibility has been defined as having life cycle impacts equal to or lower than those of petrol. Two hydrogen production methods have been analysed. The first is steam methane reforming (SMR), which uses natural gas (methane) as a feedstock. The second method analysed is alkaline electrolysis (AE), a mature technology that uses water as a feedstock. The life cycle emissions and impacts were assessed per kilometre of vehicle travel.     

Hydrogen production via urea electrolysis using a gel electrolyte

A technology was demonstrated for the production of hydrogen and other valuable products (nitrogen and clean water) through the electrochemical oxidation of urea in alkaline media. In addition, this process remediates toxic nitrates and prevents gaseous ammonia emissions. Improvements to urea electrolysis were made through replacement of aqueous KOH electrolyte with a poly(acrylic acid) gel electrolyte. A small volume of poly(acrylic acid) gel electrolyte was used to accomplish the electrochemical oxidation of urea improving on the previous requirement for large amounts of aqueous potassium hydroxide. The effect of gel composition was investigated by varying polymer content and KOH concentrations within the polymer matrix in order to determine which is the most advantageous for the electrochemical oxidation of urea and production of hydrogen.     

Comparative LCA of methanol-fuelled SOFCs as auxiliary power systems on-board ships

Fuel cells own the potential for significant environmental improvements both in terms of air quality and climate protection. Through the use of renewable primary energies, local pollutant and greenhouse gas emissions can be significantly minimized over the full life cycle of the electricity generation process, so that marine industry accounts renewable energy as its future energy source. The aim of this paper is to evaluate the use of methanol in Solid Oxide Fuel Cells (SOFC), as auxiliary power systems for commercial vessels, through Life Cycle Assessment (LCA). The LCA methodology allows the assessment of the potential environmental impact along the whole life cycle of the process. The unit considered is a 20 kWel fuel cell system. In a first part of the study different fuel options have been compared (methanol, bio-methanol, natural gas, hydrogen from cracking, electrolysis and reforming), then the operation of the cell fed with methanol has been compared with the traditional auxiliary power system, i.e. a diesel engine. The environmental benefits of the use of fuel cells have been assessed considering different impact categories. The results of the analysis show that fuel production phase has a strong influence on the life cycle impacts and highlight that feeding with bio-methanol represents a highly attractive solution from a life cycle point of view. The comparison with the conventional auxiliary power system shows extremely lower impacts for SOFCs.     

Economic,environmental, and social impacts of the hydrogen supply system combining wind power and natural gas

Hydrogen economy is one of the most attractive alternatives to the current carbon-based energy system, since it can be produced from diverse resources and used as a carbon-free energy carrier from the end-user's perspective. This study proposes a hybrid hydrogen supply system for the transport sector, which includes all the life stages from production, transport, and storage to final distribution (fueling stations). Particularly, we consider two types of resources for hydrogen production (i.e., renewable wind power and conventional natural gas) to identify the benefits and bottlenecks of hydrogen supply systems from the economic, environmental, and social perspectives. To achieve this goal, rigorous process models for the involved processes (i.e., hydrogen production by steam methane reforming from natural gas and water electrolysis using wind power, and hydrogen storage and transport) are developed. To illustrate the capability of the proposed system, we conducted a design problem within the hydrogen supply system in Jeju Island, Korea. In this case study, three scenarios were generated by combining different hydrogen production options: 1) wind power-based hydrogen production, 2) natural gas-based hydrogen production, and 3) integrated hydrogen production. As a result, we discussed the optimal hydrogen supply system, from the life cycle perspective, by identifying technical bottlenecks, major cost-drivers, and CO₂ burdens.     

Comparative assessment of hydrogen production methods from renewable and non-renewable sources

In this study, we present a comparative environmental impact assessment of possible hydrogen production methods from renewable and non-renewable sources with a special emphasis on their application in Turkey. It is aimed to study and compare the performances of hydrogen production methods and assess their economic, social and environmental impacts, The methods considered in this study are natural gas steam reforming, coal gasification, water electrolysis via wind and solar energies, biomass gasification, thermochemical water splitting with a Cu–Cl and S–I cycles, and high temperature electrolysis. Environmental impacts (global warming potential, GWP and acidification potential, AP), production costs, energy and exergy efficiencies of these eight methods are compared. Furthermore, the relationship between plant capacity and hydrogen production capital cost is studied. The social cost of carbon concept is used to present the relations between environmental impacts and economic factors. The results indicate that thermochemical water splitting with the Cu–Cl and S–I cycles become more environmentally benign than the other traditional methods in terms of emissions. The options with wind, solar and high temperature electrolysis also provide environmentally attractive results. Electrolysis methods are found to be least attractive when production costs are considered. Therefore, increasing the efficiencies and hence decreasing the costs of hydrogen production from solar and wind electrolysis bring them forefront as potential options. The energy and exergy efficiency comparison study indicates the advantages of biomass gasification over other methods. Overall rankings show that thermochemical Cu–Cl and S–I cycles are primarily promising candidates to produce hydrogen in an environmentally benign and cost-effective way.     

Life cycle assessment of high temperature electrolysis for hydrogen production via nuclear energy

A life cycle assessment (LCA) of one proposed method of hydrogen production—the high temperature electrolysis of water vapor—is presented in this paper. High temperature electrolysis offers an advantage of higher energy efficiency over the conventional low-temperature alkaline electrolysis due to reduced cell potential and consequent electrical energy requirements. The primary energy source for the electrolysis will be advanced nuclear reactors operating at temperatures corresponding to those required for the high temperature electrolysis. The LCA examines the environmental impact of the combined advanced nuclear-high temperature electrolysis plant, focusing upon quantifying the emissions of carbon dioxide, sulfur dioxide, and nitrogen oxides per kilogram of hydrogen produced. The results are presented in terms of the global warming potential (GWP) and the acidification potential (AP) of the system. The GWP for the system is 2000 g carbon dioxide equivalent and the AP, 0.15 g equivalents of hydrogen ion equivalent per kilogram of hydrogen produced. The GWP and AP of this process are one-sixth and one-third, respectively, of those for the hydrogen production by steam reforming of natural gas, and are comparable to producing hydrogen from wind- or hydro-electricity powered conventional electrolysis.     

Mass transport in PEM water electrolysers: A review

While hydrogen generation by alkaline water electrolysis is a well-established, mature technology and currently the lowest capital cost electrolyser option; polymer electrolyte membrane water electrolysers (PEMWEs) have made major advances in terms of cost, efficiency, and durability, and the installed capacity is growing rapidly. This makes the technology a promising candidate for large-scale hydrogen production, and especially for energy storage in conjunction with renewable energy sources – an application for which PEMWEs offer inherent advantages over alkaline electrolysis. Improvements in PEMWE technology have led to increasingly high operational current densities, which requires adequate mass transport strategies to ensure sufficient supply of reactant and removal of products. This review discusses the current knowledge related to mass transport and its characterisation/diagnosis for PEMWEs, considering the flow channels, liquid-gas diffusion layer, and polymer electrolyte membrane in particular.