Byproducts and reaction pathways for integration of the Cu–Cl cycle of hydrogen production

The impact of exit streams containing byproducts of incomplete reactions in an integrated thermochemical copper–chlorine (Cu–Cl) cycle of hydrogen production is studied in this paper. In the hydrolysis reaction, CuCl₂reacts with steam to produce solid copper oxychloride. If the hydrolysis reaction does not proceed to completion, particles of un-reacted CuCl₂ will be transferred to a downstream molten salt reactor where oxygen is released from copper oxychloride decomposition. Undesirable chlorine may also be released as a result of CuCl₂ decomposition together with oxygen, resulting in a mass imbalance of the overall cycle. This paper also examines the implications of incomplete hydrolysis reactions on the kinetics and thermodynamics of the oxygen reactor in the Cu–Cl cycle, specifically the spontaneity of CuCl₂ decomposition and parameters that minimize the release of chlorine. Theoretical analysis of the decomposition of a mixture of CuO and CuCl₂ is also performed in this paper. It is found that usage of copper oxychloride is preferable over a mixture of CuCl₂ and CuO in the oxygen production reaction of the Cu–Cl cycle.     

Comparative assessment of greenhouse gas mitigation of hydrogen passenger trains

This paper examines a comparative assessment in terms of CO₂ emissions from a hydrogen passenger train in Ontario, Canada, particularly comparing four specific propulsion technologies: (1) conventional diesel internal combustion engine (ICE), (2) electrified train, (3) hydrogen ICE, and (4) hydrogen PEM fuel cell (PEMFC) train. For the electrified train, greenhouse gases from electricity generation by natural gas and coal-burning power plants are taken into consideration. Several hydrogen production methods are also considered in this analysis, i.e., (1) steam methane reforming (SMR), (2) thermochemical copper–chlorine (Cu–Cl) cycle supplied partly by waste heat from a nuclear plant, (3) renewable energies (solar and wind power) and (4) a combined renewable energy and copper–chlorine cycle. The results show that a PEMFC powertrain fueled by hydrogen produced from combined wind energy and a copper–chlorine plant is the most environmentally friendly method, with CO₂ emissions of about 9% of a conventional diesel train or electrified train that uses a coal-burning power plant to generate electricity. Hydrogen produced with a thermochemical cycle is a promising alternative to further reduce the greenhouse gas emissions. By replacing a conventional diesel train with hydrogen ICE or PEMFC trains fueled by Cu-Cl based-hydrogen, the annual CO₂ emissions are reduced by 2260 and 3318 tonnes, respectively. A comparison with different types of automobile commuting scenarios to carry an equivalent number of people as a train is also conducted. On an average basis, only an electric car using renewable energy-based electricity that carries more than three people may be competitive with hydrogen trains.     

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.     

Life cycle evaluation of hydrogen and other potential fuels for aircrafts

In the present study, hydrogen and some other alternative fuels (such as ammonia, methanol, ethanol, liquefied natural gas) are considered for aviation applications under a comprehensive life cycle assessment study and are evaluated comparatively with the conventional kerosene based jet fuel for various impact categories. Therefore, this study is performed with a well-to-wake approach to evaluate the overall life cycle of an aircraft running on these conventional and alternative fuels. Both conventional and renewable fuel routes are considered for the production of ammonia and hydrogen fuels. Although there are modifications required to fulfill the aviation fuel specifications for such alternative fuels, the long term viability and environmental sustainability make them attractive solutions for the future of aviation industry. This study uses a life cycle assessment of an average aircraft utilizing various alternative aviation fuels to determine the relative environmental impact of each life cycle phase. The life cycle phases included in the analyses are as follows: (i) production, operation and maintenance of the aircraft, (ii) construction, maintenance and disposal of the airport, (iii) production, transportation and utilization of the aviation fuel in the aircraft. The results show that hydrogen and liquefied natural gas represent more environmentally benign alternatives although fuel costs are higher compared to ammonia, jet fuel and methanol. The total GHG emissions from hydropower based ammonia and hydrogen are calculated to be about 0.24 kg CO₂ eq. per traveled tonne-km and 0.03 kg CO₂ eq. per traveled tonne-km, respectively. Renewable based ammonia and hydrogen fueled aircrafts can further decrease the overall environmental impact in many categories allowing a brighter future for aviation industry.     

Greenhouse gas emissions reduction by use of wind and solar energies for hydrogen and electricity production: Economic factors

This study addresses economic aspects of introducing renewable technologies in place of fossil fuel ones to mitigate greenhouse gas emissions. Unlike for traditional fossil fuel technologies, greenhouse gas emissions from renewable technologies are associated mainly with plant construction and the magnitudes are significantly lower. The prospects are shown to be good for producing the environmentally clean fuel hydrogen via water electrolysis driven by renewable energy sources. Nonetheless, the cost of wind- and solar-based electricity is still higher than that of electricity generated in a natural gas power plant. With present costs of wind and solar electricity, it is shown that, when electricity from renewable sources replaces electricity from natural gas, the cost of greenhouse gas emissions abatement is about four times less than if hydrogen from renewable sources replaces hydrogen produced from natural gas. When renewable-based hydrogen is used in a fuel cell vehicle instead of gasoline in a IC engine vehicle, the cost of greenhouse gas emissions reduction approaches the same value as for renewable-based electricity only if the fuel cell vehicle efficiency exceeds significantly (i.e., by about two times) that of an internal combustion vehicle. It is also shown that when 6000 wind turbines (Kenetech KVS-33) with a capacity of 350 kW and a capacity factor of 24% replace a 500-MW gas-fired power plant with an efficiency of 40%, annual greenhouse gas emissions are reduced by 2.3 megatons. The incremental additional annual cost is about $280 million (US). The results provide a useful approach to an optimal strategy for greenhouse gas emissions mitigation.     

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.     

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.     

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.     

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.     

Progress of international hydrogen production network for the thermochemical Cu–Cl cycle

This paper presents recent advances by an international team which is developing the thermochemical copper–chlorine (Cu–Cl) cycle for hydrogen production. Development of the Cu–Cl cycle has been pursued by several countries within the framework of the Generation IV International Forum (GIF) for hydrogen production with the next generation of nuclear reactors. Due to its lower temperature requirements in comparison with other thermochemical cycles, the Cu–Cl cycle is particularly well matched with Canada's Generation IV reactor, SCWR (Super-Critical Water Reactor), as well as other heat sources such as solar energy or industrial waste heat. In this paper, recent developments of the Cu–Cl cycle are presented, specifically involving unit operation experiments, corrosion resistant materials and system integration.     

Greenhouse gas emissions in the nuclear life cycle: A balanced appraisal

In order to combat global warming, a detailed knowledge of the greenhouse gas (GHG) emissions associated with different energy conversion technologies is important. For nuclear energy, GHG emissions result from different process stages of the whole fuel cycle. A life-cycle assessment offers the possibility to properly calculate these emissions. In the past, both indirect energy use and GHG emissions were studied by many researchers. Most of the studies result in low indirect emissions comparable to wind turbines. However, some of the studies in the literature obtain high results adding up to a significant fraction of the direct emissions from a CCGT.     

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.     

Life cycle assessment of hydrogen production by methane decomposition using carbonaceous catalysts

Methane decomposition to yield hydrogen and carbon (CH₄ ? 2H₂ + C) is one of the cleanest alternatives, free of CO₂ emissions, for producing hydrogen from fossil fuels. This reaction can be catalyzed by metals, although they suffer a fast deactivation process, or by carbonaceous materials, which present the advantage of producing the catalyst from the carbon obtained in the reaction. In this work, the environmental performance of methane decomposition catalyzed by carbonaceous catalysts has been evaluated through Life Cycle Assessment tools, comparing it to other decomposition processes and steam methane reforming coupled to carbon capture systems. The results obtained showed that the decomposition using the autogenerated carbonaceous as catalyst is the best option when reaction conversions higher than 65% are attained. These were confirmed by 2015 and 2030 forecastings. Moreover, its environmental performance is highly increased when the produced carbon is used in other commercial applications. Thus, for a methane conversion of 70%, the application of 50% of the produced carbon would lead to a virtually zero-emissions process.     

Life cycle analysis of energy use and greenhouse gas emissions for road transportation fuels in China

Life cycle analysis is considered to be a valuable tool for decision making towards sustainability. Life cycle energy and environmental impact analysis for conventional transportation fuels and alternatives such as biofuels has become an active domain of research in recent years. The present study attempts to identify the most reliable results to date and possible ranges of life cycle fossil fuel use, petroleum use and greenhouse gas emissions for various road transportation fuels in China through a comprehensive review of recently published life cycle studies and review articles. Fuels reviewed include conventional gasoline, conventional diesel, liquefied petroleum gas, compressed natural gas, wheat-derived ethanol, corn-derived ethanol, cassava-derived ethanol, sugarcane-derived ethanol, rapeseed-derived biodiesel and soybean-derived biodiesel. Recommendations for future work are also discussed.     

Life cycle assessment of nuclear-based hydrogen production via a copper–chlorine cycle: A neural network approach

A comparative environmental study is reported of nuclear-based hydrogen production using thermochemical water decomposition cycles. The investigation uses a life cycle assessment (LCA) as is an analytical tool to evaluate and reduce the environmental impact of the system or product. The LCA results are presented in terms of acidification potential and global warming potential. Since LCA often utilizes software to model and analyse the system, an artificial neural network (ANN) method can be advantageous. Here, an ANN method is applied to a nuclear-based hydrogen production system. Using an ANN method in this study eliminates the need to use LCA software separately and facilitates the determination of the impacts of altering input parameters of a system (e.g., heat, work, production capacity and plant lifetime). The neural network approach to identify the best system option, consistent with LCA software results, is developed here using ten neurons in the hidden layers.     

Life cycle assessment of hydrogen fuel cell and gasoline vehicles

A life cycle assessment of hydrogen and gasoline vehicles, including fuel production and utilization in vehicles powered by fuel cells and internal combustion engines, is conducted to evaluate and compare their efficiencies and environmental impacts. Fossil fuel and renewable technologies are investigated, and the assessment is divided into various stages.     

The cost analysis of hydrogen life cycle in China

Currently, the increasing price of oil and the possibility of global energy crisis demand for substitutive energy to replace fossil energy. Many kinds of renewable energy have been considered, such as hydrogen, solar energy, and wind energy. Many countries including China have their own plan to support the research of hydrogen, because of its premier features. But, at present, the cost of hydrogen energy production, storage and transportation process is higher than that of fossil energy and its commercialization progress is slow. Life cycle cost analysis (LCCA) was used in this paper to evaluate the cost of hydrogen energy throughout the life cycle focused on the stratagem selection, to demonstrate the costs of every step and to discuss their relationship. Finally, the minimum cost program is as follows: natural gas steam reforming – high-pressure hydrogen bottles transported by car to hydrogen filling stations – hydrogen internal-combustion engines.     

Incorporating uncertainty analysis into life cycle estimates of greenhouse gas emissions from biomass production

Before further investments are made in utilizing biomass as a source of renewable energy, both policy makers and the energy industry need estimates of the net greenhouse gas (GHG) reductions expected from substituting biobased fuels for fossil fuels. Such GHG reductions depend greatly on how the biomass is cultivated, transported, processed, and converted into fuel or electricity. Any policy aiming to reduce GHGs with biomass-based energy must account for uncertainties in emissions at each stage of production, or else it risks yielding marginal reductions, if any, while potentially imposing great costs.This paper provides a framework for incorporating uncertainty analysis specifically into estimates of the life cycle GHG emissions from the production of biomass. We outline the sources of uncertainty, discuss the implications of uncertainty and variability on the limits of life cycle assessment (LCA) models, and provide a guide for practitioners to best practices in modeling these uncertainties. The suite of techniques described herein can be used to improve the understanding and the representation of the uncertainties associated with emissions estimates, thus enabling improved decision making with respect to the use of biomass for energy and fuel production.     

Life cycle assessment study of solar PV systems: An example of a 2.7 kWp distributed solar PV system in Singapore

In life cycle assessment (LCA) of solar PV systems, energy pay back time (EPBT) is the commonly used indicator to justify its primary energy use. However, EPBT is a function of competing energy sources with which electricity from solar PV is compared, and amount of electricity generated from the solar PV system which varies with local irradiation and ambient conditions. Therefore, it is more appropriate to use site-specific EPBT for major decision-making in power generation planning. LCA and life cycle cost analysis are performed for a distributed 2.7 kW_p grid-connected mono-crystalline solar PV system operating in Singapore. This paper presents various EPBT analyses of the solar PV system with reference to a fuel oil-fired steam turbine and their greenhouse gas (GHG) emissions and costs are also compared. The study reveals that GHG emission from electricity generation from the solar PV system is less than one-fourth that from an oil-fired steam turbine plant and one-half that from a gas-fired combined cycle plant. However, the cost of electricity is about five to seven times higher than that from the oil or gas fired power plant. The environmental uncertainties of the solar PV system are also critically reviewed and presented.     

Environmental life cycle assessment of alternative fuels for city buses: A case study in Oujda city,Morocco

The road transport sector, particularly public transport, generates significant greenhouse gas emissions due to the excessive use of petroleum-based fuels. The use of alternative fuels with lower environmental impacts is therefore a major challenge to move towards a more sustainable public transport sector. In this context, the current study presents an environmental life cycle assessment of alternative buses, including hybrid (diesel-electricity), electric, and fuel cell buses at a city level in Oujda, Morocco. This study is perfromed according to three main outputs: total energy use by fuel type, GHG emissions, and criteria air pollutants. It is concluded that electric and fuel cell buses represent efficient and sustainable alternatives to public transport during the operational phase and their deployment in Oujda city can potentially offer significant environmental savings in terms of GHG emissions and air pollutants during both the WTT and TTW phases.