Hydrogen versus synthetic fossil fuels

The fuels most considered for the post petroleum and natural gas era, hydrogen (gaseous and liquid) and synthetic fluid fossil fuels, have been compared by taking into account production costs, utilization efficiencies and environmental effects. Three different cost bases have been used for hydrogen depending on the primary energy sources used in its production. The results show that hydrogen is a much more cost effective energy carrier than synthetic fossil fuels. In addition to its environmental and efficiency benefits, hydrogen causes resource conservation, savings in transportation and capital investment, and reduction in inflation.     

Replacement of fossil fuels by hydrogen

Up to the end of the century, an export business for photovoltaic solar power stations with an accumulated total power of more than 300 gigawatts could be build up. The profit from the export of these solar-electrical power stations could finance the, at that time, accumulated total costs for the project of $200 billion(US). Included in this financial investment would also be the construction of so-called solar plantation families. After the year 2000, a total of 10 plantation families (each with 10 family members) situated in suitable deserted zones of the world would be capable of reproducing themselves. With this aim, each plantation would use its output of electrical energy to produce solar cells and materials for the construction of 10 new plantations within a decade. This highly technological growth process for identical solar plantation units could be completed in the fourth generation of each plantation family, i.e. about 50 years after the start of construction of the first plantation. From this time on, all 10 plantation families could together, by using their electrical energy for the electrolysis of water, generate an amount of hydrogen per year which would represent four to five times the energy of the world's present annual consumption of oil.     

Hydrogen production from fossil fuels with carbon capture and storage based on chemical looping systems

This paper analyzes innovative processes for producing hydrogen from fossil fuels conversion (natural gas, coal, lignite) based on chemical looping techniques, allowing intrinsic CO₂ capture. This paper evaluates in details the iron-based chemical looping system used for hydrogen production in conjunction with natural gas and syngas produced from coal and lignite gasification. The paper assesses the potential applications of natural gas and syngas chemical looping combustion systems to generate hydrogen. Investigated plant concepts with natural gas and syngas-based chemical looping method produce 500 MW hydrogen (based on lower heating value) covering ancillary power consumption with an almost total decarbonisation rate of the fossil fuels used.The paper presents in details the plant concepts and the methodology used to evaluate the performances using critical design factors like: gasifier feeding system (various fuel transport gases), heat and power integration analysis, potential ways to increase the overall energy efficiency (e.g. steam integration of chemical looping unit into the combined cycle), hydrogen and carbon dioxide quality specifications considering the use of hydrogen in transport (fuel cells) and carbon dioxide storage in geological formation or used for EOR.     

Progress of renewable electricity replacing fossil fuels

Dramatic fall in costs of renewable energy in the last 24 months has not only accelerated the replacement of fossil fuels by renewable energy in electricity generation. The low cost renewable electricity is now starting to replace fossil fuels in other sectors.One reason is that renewable electricity is now cheaper per unit energy than oil, about the same price as fossil methan but, still, more expensive than coal. Another reason is that electricity often offer other opportunities, such as cheaper transport, better control, higher energy efficiency in final production of energy services and lower local environmental costs.     

A preliminary infrastructure design to use fossil fuels with carbon capture and storage and renewable energy systems

This paper proposes a design methodology for energy infrastructure to address the recent economic and environmental challenges. The proposed energy infrastructure was based on the recognition that fossil fuels will be used for some time with renewable energy sources because renewables are currently unable to replace fossil fuels entirely. A two-fold strategy for the energy infrastructure design is proposed. One is to minimize the negative impact of fossil fuel systems by installing carbon capture and storage (CCS) facilities to reduce greenhouse gas emissions. The other is to accelerate the introduction of renewable energy systems in their place. The design of integrated energy infrastructure is transformed as a Mixed Integer Linear Programming (MILP) problem. Cases of installing CCS and H₂ as a renewable energy source in Korea are illustrated with a discussion of the systematic design of energy infrastructure.     

Carbon dioxide from fossil fuels: Adapting to uncertainty

If present scientific information is reasonable, the world is likely to experience noticeable global warming by the beginning of the next century if high annual growth rates of fossil fuel energy use continue. Only with optimistic assumptions and low growth rates will carbon-dioxide-induced temperature increases be held below 2°C or so over the next century. Conservation, flexible energy choices and control options could lessen the potential effects of carbon dioxide. Though perhaps impractical from the standpoint of costs and efficiency losses, large coastal centralized facilities would be the most amenable to carbon dioxide control and disposal. Yet no country can control carbon dioxide levels unilaterally. The USA, however, which currently contributes over a quarter of all fossil fuel carbon dioxide emissions and possesses a quarter of the world's coal resources, could provide a much needed role in leadership, research and education.     

Strategies for a transition from fossil to nuclear fuels

Most countries now wish to reduce their dependence on fossil fuels. In this paper, Professors Häfele and Manne discuss transition away from the current situation where virtually all demands for primary energy are met by fossil fuels. Assuming that this transition is to be based upon nuclear fission, they examine the interplay between natural resource scarcities, economics costs and the assessment of alternative technologies for the production of synthetic fuels.     

Hydrogen quality from decarbonized fossil fuels to fuel cells

Increased focus on curbing carbon dioxide (CO₂) emissions and a limited and unstable supply of fossil fuel resources make diversification of energy resources a priority. Hydrogen has emerged as a promising energy vector for solving these issues. However, there are numerous challenges related to production, distribution and end use of hydrogen. Of particular importance is the link between hydrogen purity requirements for use in fuel cells and the capabilities of production. Impurities can adversely affect fuel cell performance and durability, and the fuel composition must therefore be carefully controlled. However, impurity specifications should be balanced against production and purification costs. This paper examines the effects of impurities on fuel cell performance and assesses the capabilities of hydrogen production from decarbonized fossil fuels to meet the purity requirements dictated by use in fuel cells. While carbon monoxide, hydrogen sulfide and ammonia impurities are shown to most negatively affect fuel cell performance, these species are also the most easily removed during purification. In hydrogen production from decarbonized fossil fuels, inert gases are the most limiting species in the separation. If inert gas specifications were relaxed, then carbon monoxide would become the most limiting factor.     

Sustainability of fossil fuels and alternative energies for Turkey

Reserves and production of fossil fuels in Turkey are discussed, as well as projections of production rates to the year 2010. Sustainability of fossil-fuel production has been estimated on the basis of presently known data. Fossil fuels will have a very limited lifetime. Bitumens, hydropower, geothermal energy, solar energy, wind power, biomass, and nuclear energy are appropriate alternative technologies. The potentials of these alternatives are given and recommendations are made to enhance their contributions.     

Constraints of fossil fuels depletion on global warming projections

A scientific debate is in progress about the intersection of climate change with the new field of fossil fuels depletion geology. Here, new projections of atmospheric CO₂ concentration and global-mean temperature change are presented, should fossil fuels be exploited at a rate limited by geological availability only. The present work starts from the projections of fossil energy use, as obtained from ten independent sources. From such projections an upper bound, a lower bound and an ensemble mean profile for fossil CO₂ emissions until 2200 are derived. Using the coupled gas–cycle/climate model MAGICC, the corresponding climatic projections out to 2200 are obtained. We find that CO₂ concentration might increase up to about 480 ppm (445–540 ppm), while the global-mean temperature increase w.r.t. 2000 might reach 1.2 °C (0.9–1.6 °C). However, future improvements of fossil fuels recovery and discoveries of new resources might lead to higher emissions; hence our climatic projections are likely to be underestimated. In the absence of actions of emissions reduction, a level of dangerous anthropogenic interference with the climate system might be already experienced toward the middle of the 21st century, despite the constraints imposed by the exhaustion of fossil fuels.     

Estimating dynamics of US demand for major fossil fuels

Long-run demand relationships among fossil fuels in the United States were investigated using annual data covering 1918 through 2013. Due to the endogeneity problem among the variables of interest, as indicated by the findings from the Granger Causality test, weak exogeneity test, and Directed Acyclic Graphs, the use of the seemingly unrelated regression (SUR) method was deemed appropriate. The SUR model demonstrated that there was low level of substitutability among fossil fuels, but the small magnitude of the estimated coefficient indicates that natural gas, oil, and coal are more properly classified as independent goods than as substitutes of each other within the US market. Income elasticities for all three fossil fuels indicate that they are normal goods. Several external shocks have significant impact on demand for each of the fossil fuels. Slightly lower explanatory power of oil demand equation may be explained with the fact that the model did not include US oil imports although the US economy has been dependent, to some degree, on imported oil.     

Hydrogen production via the solar thermal decarbonization of fossil fuels

Three hybrid solar/fossil-fuel endothermic processes, in which fossil fuels are used exclusively as the chemical source for H₂ production, and concentrated solar radiation as the energy source of high-temperature process heat, are considered: (1) the thermal decomposition; (2) the steam-reforming; and (3) the steam-gasification. A second-law analysis is performed for establishing their maximum exergy efficiency and CO₂ mitigation potential vis-à-vis the conventional combustion-based power generation. These hybrid solar thermochemical processes offer viable and efficient routes for fossil fuel decarbonization and CO₂ avoidance, and further create a transition path towards solar hydrogen.     

Thermodynamic analysis of fossil fuels reforming for fuel cell application

At present, the infrastructure of hydrogen production, storage and transportation is poor. Fuel reforming for hydrogen production from liquid fossil fuels such as kerosene, petrol and diesel is of great significance for wide application of on-board fuel cell and distributed energy resources. In this work, the produced and heat released of kerosene, petrol and diesel reformed by different reforming methods (autothermal reforming, partial oxidation, steam reforming) were studied by means of thermodynamic analysis. Based on the thermodynamic analysis, the effect of reforming methods on the system's ideal thermal efficiency are analysed. The results show that the hydrogen concentration of syngas obtained from steam reforming is highest regardless of the fuel types. The hydrogen yielded by per unit volume of diesel is largest under same reforming method. Autothermal reforming has the largest ideal thermal efficiency among three reforming methods.     

Autothermal chemical looping reforming process of different fossil liquid fuels

The autothermal Chemical-Looping Reforming (a-CLR) is a process where syngas is produced with two main advantages; there are captured CO₂ emissions and the heat required for the syngas production is generated by the process itself. A Ni-based material is used as oxygen carrier circulating between two fluidized bed reactors: the fuel and air reactors. In this work, the auto-thermal conditions in a global H₂ production process, integrated by the a-CLR process and a Water Gas Shift reactor, using different liquid fossil fuels were theoretically determined. The hydrogen production per mol of carbon in the fuel was similar for all fossil fuels, taking a value of 2.2 at the optimal operating temperature (700 °C). In addition, the possibility of working at low temperature for a maximum H₂ production was experimentally demonstrated in a continuous 1 kW_th a-CLR unit.     

Solar decomposition of fossil fuels as an option for sustainability

This paper presents an overview on solar-thermal decomposition of fossil fuels as a viable option for transition path from today's permanent dependency on fossil fuels to tomorrow's solar fuels via solar thermochemical technology. The paper focuses on the thermochemical hydrogen generation technologies from concentrated solar energy and gives an assessment of the recent advancements in the hydrogen producing solar reactors. The advantages and obstacles of hydrogen generation via solar cracking and solar reforming are presented along with some discussions on the feasibility of industrial scaling of these technologies. Solar cracking and solar reforming processes are discussed as promising hybrid solar/fossil technologies to take considerable share during transition from fossil fuel dependency to clean energy based sustainability.     

Time-dependent climate benefits of using forest residues to substitute fossil fuels

In this study we analyze and compare the climate impacts from the recovery, transport and combustion of forest residues (harvest slash and stumps), versus the climate impacts that would have occurred if the residues were left in the forest and fossil fuels used instead. We use cumulative radiative forcing (CRF) as an indicator of climate impacts, and we explicitly consider the temporal dynamics of atmospheric carbon dioxide and biomass decomposition. Over a 240-year period, we find that CRF is significantly reduced when forest residues are used instead of fossil fuels. The type of fossil fuel replaced is important, with coal replacement giving the greatest CRF reduction. Replacing oil and fossil gas also gives long-term CRF reduction, although CRF is positive during the first 10-25 years when these fuels are replaced. Biomass productivity is also important, with more productive forests giving greater CRF reduction per hectare. The decay rate for biomass left in the forest is found to be less significant. Fossil energy inputs for biomass recovery and transport have very little impact on CRF.     

Is photovoltaic hydrogen in Italy competitive with traditional fossil fuels?

We have performed an evaluation of the end-use price of photovoltaically produced hydrogen. Our evaluation is optimistic as current estimates of photovoltaic energy costs by other authors generally correspond to higher figures, and evaluations of process and transportation costs have usually taken into acount only the main components. Hydrogen is considered to be tax-free. A more realistic evaluation should be based on a fractional tax reduction over the short term, followed by full taxation in later years. Under these conditions, photovoltaic hydrogen as a fuel has proved to be non-competitive except in the transport sector.     

Economic feasibility of advanced technology for hydrogen production from fossil fuels

Hydrogen synthesis gas, an important feedstock and energy component in the chemical and refining industries, is currently generated primarily from carbon fuels by one of the three well-known technologies: (1) steam reforming of light hydrocarbons, (2) partial oxidation of heavy hydrocarbons, (3) gasification of coal or other solid carbon compounds. Each of these three technologies has its own characteristics such as H₂:CO ratio without shifting; impurity levels of N₂, Ar, CH₄, H₂S, and COS; thermal efficiency; optimum operating pressure; and capital cost intensity. This paper compares the compositions and costs of these different hydrogen synthesis gas processes to provide a guide for the most economical utilization of carbon fuel resources. The major considerations in the economic selection are: relative feedstock cost over the life of the facility; the size of the facility; and co-production of products to achieve improved thermal efficiency and economy of scale.     

Hydrogen via methane decomposition: an application for decarbonization of fossil fuels

Fossil fuel decarbonization is an emerging technological approach for significant reduction of CO₂ emissions into the atmosphere. CO₂-free production of hydrogen via thermocatalytic decomposition of methane (natural gas) as a viable decarbonization strategy is discussed in this paper. The technical approach is based on a single-step decomposition (pyrolysis) of methane and other hydrocarbons over carbon-based catalysts in an air/water free environment. This approach eliminates the need for water–gas shift and CO₂ removal stages, required by conventional processes (e.g. methane steam reforming), which significantly simplifies the process. Clean carbon is produced as a valuable byproduct of the process. The experimental data on the catalytic activity of different carbon-based catalysts in methane decomposition reaction are presented in this work. The paper also discusses various conceptual designs for the reactor suitable for decomposition of methane with production of hydrogen-rich gas and continuous withdrawal of elemental carbon.