While the dominant role of hydrogen in a sustainable energy future is widely accepted, the strategies for the transition from fossil-based to hydrogen economy are still actively debated. This paper ...emphasizes the role of carbon-neutral technologies and fuels during the transition period. To satisfy the world's growing appetite for energy and keep our planet healthy, at least 10
TW (or terawatt) of carbon-free power has to be produced by mid-century. Three prominent options discussed in the literature include: decarbonization of fossil energy, nuclear energy and renewable energy sources. These options are analyzed in this paper with a special emphasis on the role of hydrogen as a carbon-free energy carrier. In particular, the authors compare various fossil decarbonization strategies and evaluate the potential of nuclear and renewable energy resources to meet the 10
TW target. An overview of state-of-the-art technologies for production of carbon-free energy carriers and transportation fuels, and the assessment of their commercial potential is provided. It is shown that neither of these three options alone could provide 10
TW of carbon-neutral power without major changes in the existing infrastructure, and/or technological breakthroughs in many areas, and/or a considerable environmental risk. The authors propose a scenario for the transition from current fossil-based to hydrogen economy that includes two key elements: (i) changing the fossil decarbonization strategy from one based on CO
2 sequestration to one that involves sequestration and/or utilization of solid carbon, and (ii) producing carbon-neutral synthetic fuels from bio-carbon and hydrogen generated from water using carbon-free sources (nuclear, solar, wind, geothermal). This strategy would allow taking advantage of the existing fuel infrastructure without an adverse environmental impact, and it would secure a smooth carbon-neutral transition from fossil-based to future hydrogen economy.
21st Century’s energy: Hydrogen energy system NEJAT VEZIROGLU, T; SAHIN, Sümer
Energy conversion and management,
07/2008, Letnik:
49, Številka:
7
Journal Article, Conference Proceeding
Recenzirano
Fossil fuels (i.e., petroleum, natural gas and coal), which meet most of the world’s energy demand today, are being depleted fast. Also, their combustion products are causing the global problems, ...such as the greenhouse effect, ozone layer depletion, acid rains and pollution, which are posing great danger for our environment and eventually for the life in our planet. Many engineers and scientists agree that the solution to these global problems would be to replace the existing fossil fuel system by the hydrogen energy system. Hydrogen is a very efficient and clean fuel. Its combustion will produce no greenhouse gases, no ozone layer depleting chemicals, little or no acid rain ingredients and pollution. Hydrogen, produced from renewable energy (e.g., solar) sources, would result in a permanent energy system, which we would never have to change.
However, there are other energy systems proposed for the post-petroleum era, such as a synthetic fossil fuel system. In this system, synthetic gasoline and synthetic natural gas will be produced using abundant deposits of coal. In a way, this will ensure the continuation of the present fossil fuel system.
The two possible energy systems for the post-fossil fuel era (i.e., the solar-hydrogen energy system and the synthetic fossil fuel system) are compared with the present fossil fuel system by taking into consideration production costs, environmental damages and utilization efficiencies. The results indicate that the solar-hydrogen energy system is the best energy system to ascertain a sustainable future, and it should replace the fossil fuel system before the end of the 21st century.
Review: Biofuel production from plant and algal biomass Voloshin, Roman A.; Rodionova, Margarita V.; Zharmukhamedov, Sergey K. ...
International journal of hydrogen energy,
10/2016, Letnik:
41, Številka:
39
Journal Article
Recenzirano
Biofuels are the promising alternative to exhaustible, environmentally unsafe fossil fuels. Algal biomass is attractive raw for biofuel production. Its cultivation does not compete for cropland with ...agricultural growing of food crop for biofuel and does not require complex treatment methods in comparison with lignocellulose-enriched biomass. Many microalgae are mixotrophs, so they can be used as energy source and as sewage purifier simultaneously. One of the main steps for algal biofuel fabrication is the cultivation of biomass. Photobioreactors and open-air systems are used for this purpose. The formers allow the careful cultivation control, but the latter ones are cheaper and simpler. Biomass conversion processes may be divided to the thermochemical, chemical, biochemical methods and direct combustion. For biodiesel production, triglyceride-enriched biomass undergoes transetherification. For bioalcohol production, biomass is subjected to fermentation. There are three methods of biohydrogen production in the microalgal cells: direct biophotolysis, indirect biophotolysis, fermentation.
•Biomass of some microalgae contain more lipids than plant biomass.•Algal energetic does not compete for arable land with conventional agriculture.•Bioreactor design determines the rate of increase of the algal biomass and the biomass composition.
There is a general agreement about the consideration that the fossil fuels are a limited resource and the emission of carbon dioxide and other harmful products are the main cause of the global ...warming and climate change. The interest for decreasing the fossil fuels dependence and reducing the greenhouse gases emissions represents a top priority. The biomass is a renewable resource useful for biodiesel and bioethanol production. The latter, most plentiful, is currently considered as green ethanol produced from biomass by biological processes. Meanwhile, membrane reactors represent an innovative and intensified technology for the production and the simultaneous recovery of high-grade hydrogen in only one stage. Here, we describe an efficient medium-temperature (T = 400 °C) bioethanol steam reforming process in a thin (∼5 μm of metallic layer) supported Pd-based membrane reactor packed with a not commercial Co(10%)Pt (3%)/CeO2-ZrO2-Al2O3 bi-metallic catalyst at space velocity between 1900 h−1 and 4800 h−1 and reaction pressure between 1.5 and 2.0 bar. A real bioethanol mixture coming from industry is supplied to the membrane reactor for producing high grade hydrogen, reaching 60% of ethanol conversion (versus ∼ 40% of the equivalent conventional reactor) at 400 °C, 2.0 bar and 1900 h−1, meanwhile recovering almost 70% of the hydrogen produced during the bioethanol steam reforming reaction with a purity higher than 99%. This would make the delivery of hydrogen for PEM fuel cells supplying – and hence the use of green bioethanol as a practical hydrogen carrier – feasible.
•The 5.0 μm thick Pd-layer/Al2O3 membrane is fully H2-permselective.•The recovered H2 is > 99.5 pure.•Real bioethanol steam reforming is performed at 400 °C in the membrane reactor.
Using the Spin-Top Theory of the universe, and the available information about the universe, the characteristics of the universe-seed (or U-Seed), creation of the universe and its life cycle have ...been estimated. With the explosion of the U-Seed, made of hydrogen, hydrogen and its thermonuclear reaction products start spreading, and forming an ever growing ellipsoid on the way out, while circling the universe center (U-Center). Then, as a result of the gravitational pull, heavenly bodies start moving towards and eventually reaching the universe center (U-Center) to reform the U-Seed. During this expansion and contraction periods, the universe boundaries and the pertinent times have been calculated. It is shown that a universe cycle is about 148 billion years, and it repeats itself forever.
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•Spin-Top theory of the universe is developed using the available information about the universe.•It explains the observed features of the universe better than the Big Bang theory.•Universe consists of infinite number of cycles, with a cycle period of 148 billion years.•Universe is the only perfect perpetual motion machine.
Impact of hydrogen on the environment Nowotny, Janusz; Veziroglu, T. Nejat
International journal of hydrogen energy,
10/2011, Letnik:
36, Številka:
20
Journal Article
Recenzirano
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 CO
2, 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).
► Impact of hydrogen on the environment depends on the way of its generation. ► Hydrogen is environmentally friendly only when obtained using renewable energy. ► Hydrogen generated using steam reforming of natural gas is not environmentally friendly.
Biological hydrogen production processes offer a technique through which renewable energy sources like biomass can be utilized for the generation of the cleanest energy carrier for the use of ...mankind. Hydrogen intensive research work has already been carried out on the advancement of these processes, such as the development of genetically modified microorganism, metabolic engineering, improvement of the reactor designs, use of different solid matrices for the immobilization of whole cells, biochemical assisted bioreactor, development of two-stage processes, etc. for higher H
2-production rates. Maximum H
2 yield is found to be 7.1
mol H
2/mol glucose. However, major bottlenecks for the commercialization of these processes are lower H
2 yield and rate of H
2 production. Suitable microbial cultures are required to handle waste materials efficiently, which are usually complex in nature. This will serve dual purposes: clean energy generation and bioremediation. Scale-up studies on fermentative H
2-production processes have been done successfully. Pilot plant trials of the photo-fermentation processes require more attention. Use of cheaper raw materials and efficient biological hydrogen production processes will surely make them more competitive with the conventional H
2 generation processes in near future.
Hydrogen is the fuel of the future mainly due to its high conversion efficiency, recyclability and nonpolluting nature. Biological hydrogen production processes are found to be more environment ...friendly and less energy intensive as compared to thermochemical and electrochemical processes. They are mostly controlled by either photosynthetic or fermentative organisms. Till today, more emphasis has been given on the former processes. Nitrogenase and hydrogenase play very important role. Genetic manipulation of cyanobacteria (hydrogenase negative gene) improves the hydrogen generation. The paper presents a survey of biological hydrogen production processes. The microorganisms and biochemical pathways involved in hydrogen generation processes are presented in some detail. Several developmental works are discussed. Immobilized system is found suitable for the continuous hydrogen production. About 28% of energy can be recovered in the form of hydrogen using sucrose as substrate. Fermentative hydrogen production processes have some edge over the other biological processes.
This work is a survey of utilization of boron for hydrogen storage. Boron is a promising element for hydrogen storage with its chemical hydrides and nanostructural forms. It is also used as an ...additive in nickel metal hydride battery systems to enhance hydrogen compatibility and performance. This present study will be a brief summary of hydrogen storage technology in general and focus on possible uses of boron and its compounds.
