Impact of hydrogen on the environment

The present work considers the impact of hydrogen fuel on the environment within the cycles of its generation and combustion. Hydrogen has been portrayed by the media as a fuel that is environmentally clean because its combustion results in the formation of harmless water. However, hydrogen first must be generated. The effect of hydrogen generation on the environment depends on the production process and the related by-products. Hydrogen available on the market at present is mainly generated by using steam reforming of natural gas, which is a fossil fuel. Its by-product is CO₂, which is a greenhouse gas and its emission results in global warming and climate change. Therefore, hydrogen generated from fossil fuels is contributing to global warming to the similar extent as direct combustion of the fossil fuels. On the other hand hydrogen obtained from renewable energy, such solar energy, is environmentally clean during the cycles of its generation and combustion. Consequently, the introduction of hydrogen economy must be accompanied by the development of hydrogen that is environmentally friendly. The present work considers several aspects related to the generation and utilisation of hydrogen obtained by steam reforming and solar energy conversion (solar-hydrogen).     

Nanometallic fuels for transportation: a well‐to‐wheels analysis

Nanometallic iron and aluminium, along with hydrogen and electricity, are among the proposed alternatives to the petroleum‐based fuels for future transportation. The advantages of the metallic fuels appear to be high volumetric energy densities and zero greenhouse gas emissions during the operation of the vehicle. However, nanometallic fuels do not exist in nature, and a well‐to‐wheel analysis of the fuel manufacture‐utilization system is required to quantify the energy consumption and assess the true environmental impact of the proposed alternative. The three‐component nanometallic fuel system consisting of a metal production process, a nanoparticle formulation process and the metal combustion process is analysed in this paper. The energy balance and the environmental impact are estimated for nanometallic iron and aluminium based systems. The sustainability of once‐through systems that do not involve recycle of combustion products is questionable because of resource limitations. A viable system for satisfying the transportation fuel demands will involve the reduction and recycle of the combustion products. A comparison of these nanometallic fuels with gasoline and hydrogen indicates that nanometallic fuels are the least efficient, with primary energy consumption greater than 11 MJ km^?1 compared to 0.625 MJ km^?1 for gasoline and 8.6 MJ km^?1 for hydrogen. The nanometallic fuels will also have the most severe impact of the three, with CO₂‐equivalent emissions of 13.44 billion tons year^?1 for iron and 21.1 billion tons year^?1 for aluminium as compared to approximately 0.8 billion tons year^?1 for gasoline. These emissions from nanometallic fuels are at least an order‐of‐magnitude higher than those for gasoline and hydrogen. The results of the analysis emphasize the need for well‐to‐wheel assessment for determining the true impact of technologies proposed as replacements for the current technologies. Copyright © 2006 John Wiley & Sons, Ltd.     

An overview of solar decarbonization processes,reacting oxide materials,and thermochemical reactors for hydrogen and syngas production

Solar decarbonization processes are related to the different thermochemical conversion pathways of hydrocarbon feedstocks for solar fuels production using concentrated solar energy as the external source of high-temperature process heat. The main investigated routes aim to convert gaseous and solid feedstocks (methane, coal, biomass …) into hydrogen and syngas via solar cracking/pyrolysis, reforming/gasification, and two-step chemical looping processes using metal oxides as oxygen carriers, further associated with thermochemical H₂O/CO₂ splitting cycles. They can also be combined with metallurgical processes for production of energy-intensive metals via solar carbothermal reduction of metal oxides. Syngas can be further converted to liquid fuels while the produced metals can be used as energy storage media or commodities. Overall, such solar-driven processes allow for improvements of conversion yields, elimination of fossil fuel or partial feedstock combustion as heat source and associated CO₂ emissions, and storage of intermittent solar energy in storable and dispatchable chemical fuels, thereby outperforming the conventional processes. The different solar thermochemical pathways for hydrogen and syngas production from gaseous and solid carbonaceous feedstocks are presented, along with their possible combination with chemical looping or metallurgical processes. The considered routes encompass the cracking/pyrolysis (producing solid carbon and hydrogen) and the reforming/gasification (producing syngas). They are further extended to chemical looping processes involving redox materials as well as metallurgical processes when metal production is targeted. This review provides a broad overview of the solar decarbonization pathways based on solid or gaseous hydrocarbons for their conversion into clean hydrogen, syngas or metals. The involved metal oxides and oxygen carrier materials as well as the solar reactors developed to operate each decarbonization route are further described.     

Feasibility study for the transition towards a hydrogen economy: A case study in Brazil

Fossil fuels use has caused serious environmental impacts worldwide, mainly related with the greenhouse effect intensification. One strategy to mitigate such impacts is the use of hydrogen in combustion processes. Additionally, hydrogen can be utilized as an energy vector for storage purposes and is also classified as a fuel of the future, due to the low emission of pollutants into the atmosphere. The present paper shows results of a computational simulation carried out for the state of Ceará, Brazil, considering scenarios for the use of electrolytic hydrogen obtained with the use of photovoltaic (PV) modules and wind energy converters, as a substitute of fluid fossil fuels.     

A solar–wind hydrogen energy system for the Ceará state – Brazil

In this paper, a program of electrolytic hydrogen energy for the Ceará state in Brazil is proposed. Hydrogen will be produced through the assistance of photovoltaic cell panels and wind turbines. The generated hydrogen will serve as an energy carrier and will be used in every application where fossil fuels are being used today. The scenarios of fast and slow introduction of hydrogen and of no introduction of hydrogen were envisaged. Results indicate that the introduction of renewable energy hydrogen will increase the energy consumption and the gross internal product per capita of the Ceará state. In the same time it will reduce pollution originated from fossil fuels combustion and consequently will increase the quality of life of the population of such federal state of Brazil.     

Wind energy–hydrogen storage hybrid power generation

In this theoretical investigation, a hybrid power generation system utilizing wind energy and hydrogen storage is presented. Firstly, the available wind energy is determined, which is followed by evaluating the efficiency of the wind energy conversion system. A revised model of windmill is proposed from which wind power density and electric power output are determined. When the load demand is less than the output of the generation, the excess electric power is relayed to the electrolytic cell where it is used to electrolyze the de‐ionized water. Hydrogen thus produced can be stored as hydrogen compressed gas or liquid. Once the hydrogen is stored in an appropriate high‐pressure vessel, it can be used in a combustion engine, fuel cell, or burned in a water‐cooled burner to produce a very high‐quality steam for space heating, or to drive a turbine to generate electric power. It can also be combined with organic materials to produce synthetic fuels. The conclusion is that the system produces no harmful waste and depletes no resources. Note that this system also works well with a solar collector instead of a windmill. Copyright © 2001 John Wiley & Sons, Ltd.     

Combined hydrogen production and power generation from aluminum combustion with water: Analysis of the concept

In this paper the combined production of hydrogen and power based on the aluminum combustion with water is investigated. Furthermore, a concept system is proposed that is potentially able to provide pressurized hydrogen and high temperature steam along with heat and work at the crankshaft. The system demonstrates high energy conversion efficiency, and it fully complies with environment sustainability requirements.     

Effect of hydrogen supplementation on engine performance and emissions

Vehicular Pollution and environmental degradation are on the rise with increasing vehicles and to stop this strict regulation have been put on vehicular emissions. Also, the depleting fossil fuels are of great concern for energy security. This has motivated the researchers to invest considerable resources in finding cleaner burning, sustainable and renewable fuels. However renewable fuels independently are not sufficient to deal with the problem at hand due to supply constraints. Hence, advanced combustion technologies such as homogeneous charge compression ignition (HCCI), low-temperature combustion (LTC), and dual fuel engines are extensively researched upon. In this context, this work investigates dual fuel mode combustion using a constant speed diesel engine, operated using hydrogen and diesel. The engine is operated at 25, 50 and 75% loads and substitution of diesel energy with hydrogen energy is done as 0, 5, 10 and 20%. The effect of hydrogen energy share (HES) enhancement on engine performance and emissions is investigated. In the tested range, slightly detrimental effect of HES on brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) is observed. Comparision of NO and NO₂ emissions is done to understand the non-thermal influence of H₂ on the NO_x emissions. Hence, HES is found beneficial in reducing harmful emissions at low and mid loads.     

Well-to-wheel study of passenger vehicles in the Norwegian energy system

For the evaluation of potential routes for production and application of hydrogen in a future energy system, well-to-wheel (WtW) methodologies provide a means of comparing overall impacts of technologies and fuels in a consistent and transparent manner. Such analysis provides important background information for decision makers when implementing political incentives for the conversion to more environmentally friendly energy production and consumption. In this study, a WtW approach was applied in order to evaluate the energetic and environmental impacts of introducing hydrogen in the transportation sector, in terms of energy efficiency and emissions of CO₂ and NO_x, under conditions relevant for the Norwegian energy system. The hydrogen chains were compared to reference chains with conventional fuels.     

Latest concepts for combustion and waste heat recovery systems being considered for hydrogen engines

A more sustainable transportation calls for the use of alternative and renewable fuels, a further increase of the fuel energy conversion efficiency of internal combustion engines as well as the reduction of the thermal engine energy supply by recovering the braking energy. The paper presents two concepts being developed to improve the fuel conversion efficiency of internal combustion engines for transport applications. The first concept works on the combustion evolution to increase the amount of fuel energy transformed in piston work within the cylinder. The second concept works on the waste exhaust and coolant energies to be recovered through a power turbine downstream of the turbocharger turbine on the exhaust line and a steam turbine feed with the steam produced by a boiler/super heater made of the coolant passages and a heat exchanger on the exhaust line. The concepts work with hydrogen (and in this case a water injector is also necessary) as well as lower alkanes (methane, propane, butane). Preliminary simulations show improvement of top fuel conversion efficiencies to above 50% in the high power density operation. The waste heat recovery system also permits faster warm-up during cold start driving cycles.     

Potential of renewable hydrogen production for energy supply in Hong Kong

Hong Kong is highly vulnerable to energy and economic security due to the heavy dependence on imported fossil fuels. The combustion of fossil fuels also causes serious environmental pollution. Therefore, it is important to explore the opportunities for clean renewable energy for long-term energy supply. Hong Kong has the potential to develop clean renewable hydrogen energy to improve the environmental performance. This paper reviews the recent development of hydrogen production technologies, followed by an overview of the renewable energy sources and a discussion about potential applications for renewable hydrogen production in Hong Kong. The results show that although renewable energy resources cannot entirely satisfy the energy demand in Hong Kong, solar energy, wind power, and biomass are available renewable sources for significant hydrogen production. A system consisting of wind turbines and photovoltaic (PV) panels coupled with electrolyzers is a promising design to produce hydrogen. Biomass, especially organic waste, offers an economical, environmental-friendly way for renewable hydrogen production. The achievable hydrogen energy output would be as much as 40% of the total energy consumption in transportation.     

Alternative energy development strategies for China towards 2030

The purposes, objectives and technology pathways for alternative energy development are discussed with the aim of reaching sustainable energy development in China. Special attention has been paid to alternative power and alternative vehicle fuels. Instead of limiting alternative energy to energy sources such as nuclear and renewable energy, the scope of discussion is extended to alternative technologies such as coal power with carbon capture and sequestration (CCS), electric and hydrogen vehicles. In order to take account of the fact that China’s sustainable energy development involves many dimensions, a six-dimensional indicator set has been established and applied with the aim of comprehensively evaluating different technology pathways in a uniform way. The analysis reaches the following conclusions: (a) in the power sector, wind power, nuclear power and hydro power should be developed as much as possible, while R&D of solar power and coal power with CCS should be strengthened continuously for future deployment. (b) in the transportation sector, there is no foreseeable silver bullet to replace oil on a large scale within the time frame of 20 to 30 years. To ease the severe energy security situation, expedient choices like coal derived fuels could be developed. However, its scale should be optimized in accordance to the trade-off of energy security benefits, production costs and environmental costs. Desirable alternative fuels (or technologies) like 2nd generation biofuels and electrical vehicles should be the subject of intensive R&D with the objective to be cost effective as early as possible.     

Alternative energy development strategies for China towards 2030

The purposes, objectives and technology pathways for alternative energy development are discussed with the aim of reaching sustainable energy development in China. Special attention has been paid to alternative power and alternative vehicle fuels. Instead of limiting alternative energy to energy sources such as nuclear and renewable energy, the scope of discussion is extended to alternative technologies such as coal power with carbon capture and sequestration (CCS), electric and hydrogen vehicles. In order to take account of the fact that China’s sustainable energy development involves many dimensions, a six-dimensional indicator set has been established and applied with the aim of comprehensively evaluating different technology pathways in a uniform way. The analysis reaches the following conclusions: (a) in the power sector, wind power, nuclear power and hydro power should be developed as much as possible, while R&D of solar power and coal power with CCS should be strengthened continuously for future deployment. (b) in the transportation sector, there is no foreseeable silver bullet to replace oil on a large scale within the time frame of 20 to 30 years. To ease the severe energy security situation, expedient choices like coal derived fuels could be developed. However, its scale should be optimized in accordance to the trade-off of energy security benefits, production costs and environmental costs. Desirable alternative fuels (or technologies) like 2nd generation biofuels and electrical vehicles should be the subject of intensive R&D with the objective to be cost effective as early as possible.     

Characterization and sustainability assessment of Canada's Hydrogen Highway™

This paper presents the characterization and sustainability assessment of an integrated scenario describing a number of demonstration projects currently planned along the proposed Hydrogen Highway™ in British Columbia (BC), Canada. The characterization reveals a large gap between the current activity and the projections of the Canadian National Energy Board Techno-Vert scenario for British Columbia in 2010. Insights from the technology diffusion literature are also discussed as it pertains to the diffusion of hydrogen and fuel cell technologies. The sustainability assessment reveals that the BC hydrogen energy scenario as a whole is more sustainable in terms of its CO₂(eq) emissions, air pollutant emissions and energy efficiency than a more conventional scenario, but costly in terms of its CO₂(eq) reduction potential. The paper discusses the limitations of the cost-effectiveness calculations as well as the sustainability assessment, and suggestions are made for future improvements in this area. Copyright © 2006 John Wiley & Sons, Ltd.     

S.I. engine fuelled with gasoline,methane and methane/hydrogen blends: Heat release and loss analysis

Experiments were carried out to investigate the performance of different fuels used in a internal combustion engine: gasoline, methane and fuel blends containing methane with 5%, 10% and 15% hydrogen by volume, respectively. A two-litre naturally aspirated bi-fuel engine with port fuel injection was used. The engine was operated stoichiometrically. For each fuel the spark advance for best efficiency was determined. Experiments were conducted at 2000 rpm and 2 bar brake mean effective pressure. A heat release analysis and a loss analysis were performed for all fuels. The main findings are that increasing the hydrogen fraction of the methane hydrogen fuel blend decreases the overall burn duration. This decrease is predominantly achieved by a shortened duration of the fist stage of combustion (ignition to 5% mass fraction burned). The faster combustion comes along with an increase in fuel conversion efficiency. The different losses for gasoline and pure methane operation interact such that equal fuel conversion efficiencies result. However, care has to be taken when comparing fuel conversion efficiencies among the different fuels as the relative error in fuel conversion efficiency for the gaseous fuels is 0.2% at most, whereas it is about 1% for gasoline.     

Study on waste heat recovery from exhaust smoke in cogeneration system using woody biomass fuels

In recent years, fossil fuels such as petroleum, coal, and natural gas have become limited resources. In addition, bad effects caused by excessive carbon dioxide (CO₂) emissions have now begun destroying our global environment seriously. Since current living and economical standards depend strongly on the fossil fuels, it is necessary to realize a new society that utilizes biomass as one of major sources of energy. In this background, we manufactured a practical Stirling engine using woody biomass fuels for the first time in Japan in 2005. Further we proposed a unique cogeneration system with the Stirling engine that uses woody biomass fuels such as sawdust, firewood, and wood pellets. In this cogeneration system, 43% of the input energy is wasted as heat loss from the exhaust smoke into the atmosphere. Therefore we tried to recover the waste heat by using a thermoelectric conversion module in this study. In this report, the results of basic performance test and demonstration experiment as a cogeneration system combined the waste heat recovery with a power generating system are reported. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20390     

Prospects for the production of green hydrogen: Review of countries with high potential

The article provides a review of the current hydrogen production and the prospects for the development of the production of “green” hydrogen using renewable energy sources in various countries of the world that are leaders in this field. The potential of hydrogen energy in such countries and regions as Australia, the European Union, India, Canada, China, the Russian Federation, United States of America, South Korea, the Republic of South Africa, Japan and the northern countries of Africa is considered. These countries have significant potential for the production of hydrogen and “green” hydrogen, in particular through mining of fossil fuels and the use of renewable energy sources. The quantitative indicators of the production of “green” hydrogen in the future and the direction of its export are considered; the most developed hydrogen technologies in these countries are presented. The production of “green” hydrogen in most countries is the way to transition from the consumption of fossil fuels to the clean energy of the future, which will significantly improve the environmental situation, reduce greenhouse gas emissions and improve the energy independence of the regions.     

A numerical study of a methane-fueled gas engine generator with addition of hydrogen using cycle simulation and DOE method

Conventional fossil fuels for combustion systems, such as gasoline and diesel, have a number of problems related to energy security and emissions. Alternative fuels, such as methane, hydrogen, and mixtures of these two gases, are being promoted as clean energy substitutes for primary fossil fuels. Natural gas (which consists mainly of methane) is one of the most promising of these fuels, providing lower cost, cleaner emissions and is direct applicable to existing combustion systems. However, the use of natural gas as fuel can adversely affect engine performance. Therefore, hydrogen is sometimes used as an additive, as its higher burning rate often leads to enhanced combustion. In this study, cycle simulation was used to numerically investigate the performance and emission characteristics of an engine employed primarily to power a generator, and fueled with methane and methane - hydrogen blends. Dominant parameters such as excess air ratio, spark timing, and volume percent of hydrogen content, were investigated as independent variables. The fundamental effect of hydrogen on methane combustion was investigated for a fixed excess air ratio of 1.2 and a spark timing of 14CA(Crank Angle) BTDC (Before Top Dead Center), with an accompanying reduction in ignition delay. By varying the excess air ratio, hydrogen was demonstrated to play an important role in extending the lean operating limit. The DOE (Design of Experiment) method was applied to study MBT (Maximum Brake Torque) spark timing for various excess air ratios and hydrogen contents. When MBT spark timing was employed, maximum brake torque could be achieved under leaner burning conditions by increasing the hydrogen content.     

A global survey of hydrogen energy research,development and policy

Several factors have led to growing interest in a hydrogen energy economy, especially for transportation. A successful transition to a major role for hydrogen will require much greater cost-effectiveness, fueling infrastructure, consumer acceptance, and a strategy for its basis in renewable energy feedstocks. Despite modest attention to the need for a sustainable hydrogen energy system in several countries, in most cases in the short to mid term hydrogen will be produced from fossil fuels. This paper surveys the global status of hydrogen energy research and development (R&D) and public policy, along with the likely energy mix for making it. The current state of hydrogen energy R&D among auto, energy and fuel-cell companies is also briefly reviewed. Just two major auto companies and two nations have specific targets and timetables for hydrogen fuel cells or vehicle production, although the EU also has an aggressive, less specific strategy. Iceland and Brazil are the only nations where renewable energy feedstocks are envisioned as the major or sole future source of hydrogen. None of these plans, however, are very certain. Thus, serious questions about the sustainability of a hydrogen economy can be raised.     

Waste to liquid fuels: potency,progress and challenges

The valorization of municipal solid waste (MSW) into liquid fuels is a multi‐beneficial global option for ensuring environmental and energy sustainability. The paper critically reviewed a wide range of recent literature on the potency, progress, and challenges associated with MSW upgrading into liquid fuels. Concise details on the various upgrading technologies involved such as gasification, pyrolysis, and syngas‐to‐fuels (i.e., syngas to gasoline and diesel) via a Fischer–Tropsch process were documented. Emphasis was critically given to the recent literature updates. The paper explored the role of heterogeneous catalyst systems in achieving the various processes with special considerations for optimizing fuel yield. Prospective technologies such as plasma gasification and nanoscale catalyst design with potentials to revolutionize the industry were also discussed. Copyright © 2015 John Wiley & Sons, Ltd.