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.
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.
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.
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.
This study is related to the electrochemical oxidation of NaBH
4 on Au, Pt, Pd and Ni electrodes by the use of cyclic and square wave voltammetry. The most effective metal for the oxidation of sodium ...borohydride was found to be Au. Pt and Pd electrodes also showed certain activity while Ni was not effective. The compound was observed to give two consecutive oxidation steps with 6 and 2 electron transfers. The experiments conducted while keeping the potential at
-
0.8
V
showed that the resulting compound is adsorbed upon the electrode surface and gradually decrease its catalytic activity.
The rejection of hydrogen as a solution to global warming by becoming the medium of wind and solar was made when gasoline was priced at $1/gallon.
From wind, H
2 would now cost (by electrolysis of ...water and steam) less than $3 for an amount equivalent in energy to that in a gallon of gasoline (“equivalent”). From solar photovoltaics (pv), H
2 would be sinking in price between $8 toward $5 equivalent as the efficiency of solar pv increases toward 20%.
1
1
Calculated price estimates stated here include 25% profit and the cost of piping H
2 1000
miles. Unless otherwise stated, prices are in 2006$.
Solar thermal's present prices offer about one-half the solar pv prices.
Prediction of the maximum of the delivery rate of world oil is Laherre's Oil Production Forecast, 1950–2150. Reprinted with permission from correspondence with William Horvath, U.S. Department of Energy, March 29, 2001 2010.
Future energy sources will develop inexhaustible energies from wind, solar, geothermal, tidal, and wave sources. The common media will be hydrogen and electricity. These sources yield energy at around one-half the cost of nuclear fission.
Growing corn to make alcohol involves a net loss of energy and need for a heating mechanism.
2
2
Growth of the plant fueled by solar light and CO
2, forming alcohol involves a heating stage and numerous operatives use fossil fuels, thus introducing CO
2. This ruins the “no CO
2” process. However, it is pointed out in this paper that one could use an excess of the first stage biofuel to provide heat and this would run on CO
2 and light, i.e., no net CO
2 in burning.
It may increase the Greenhouse.
Summary
In recent years, there has been considerable interest in incorporating naturally occurring components of the photosynthetic apparatus into man‐made solar cells, because of the high quantum ...efficiency of photosynthetic reaction centers. One hurdle to overcome regarding the use of native membranes in these devices is their limited lifespans. In this study, we used stabilizers to increase the long‐term viability of biomolecules in vitro, thereby alleviating this challenge. In this regard, it is known that osmolytes, such as glycine betaine (GB) and sucrose, preserve photosynthetic activity in isolated photosystems. Upon investigation of the thermal protection properties of GB and sucrose in thylakoid‐based dye‐sensitized solar cells, we report that the addition of GB and sucrose to the thylakoid photosensitizer maintains nonzero photocurrent in the thylakoid‐based solar cell upon heating to 50°C. At 50°C, the GB‐containing cell displayed about a fourfold increase in photocurrent than the control cell, in which the photocurrent was decreased to nearly zero. The addition of 0.5M and 1M sucrose has respectively caused nearly 40% and 70% increases in photoinduced electron transfer activity over the control at 35°С. Similarly, though to a lesser extent, 1M GB caused an approximate 40% increase in electron transfer activity as well. Moving forward, this approach will be extended to alternative membrane protein isolation strategies, allowing for an accurate comparison with traditional detergent‐isolated complexes, with the ultimate goal of developing a cost‐effective and sustainable solar cell.
Cosolutes that stabilize photosystems can increase the efficiency of thylakoid‐based solar cell. Cosolutes at high concentration hinder attachment of the thylakoids to the TiO2. Sucrose and GB increase the photocurrent of thylakoid‐based solar cells at elevated temperature.
Hydrogen from hydrogen sulphide in Black Sea Baykara, S.Z.; Figen, E.H.; Kale, A. ...
International journal of hydrogen energy,
06/2007, Letnik:
32, Številka:
9
Journal Article
Recenzirano
Hydrogen sulphide, an acid gas, is generally considered an environmental pollutant. As an industrial byproduct, it is produced mostly during fuel processing. Hydrogen sulphide occurs naturally in ...many gas wells and also in gas hydrates and gas-saturated sediments especially at the bottom of the Black Sea where 90% of the sea water is anaerobic.
The anoxic conditions exist in the deepest parts of the basin since nearly 7300 years, caused by the density stratification following the significant influx of the Mediterranean water through the Bosphorous nearly 9000 years ago. Here,
H
2
S
is believed to be produced by sulphur reducing bacteria at an approximate rate of 10
000 tons per day, and it poses a serious threat since it keeps reducing the life in the Black Sea. An oxygen–hydrogen sulphide interface is established at 150–200
m below the surface after which
H
2
S
concentration starts increasing regularly until 1000
m, and finally reaches a nearly constant value of 9.5
mg/l around 1500
m depth.
Hydrogen sulphide potentially has economic value if both sulphur and hydrogen can be recovered. Several methods are studied for
H
2
S
decomposition, including thermal, thermochemical, electrochemical, photochemical and plasmochemical methods.
In the present work,
H
2
S
potential in the Black Sea is investigated as a source of hydrogen, an evaluation of the developing prominent techniques for hydrogen production from
H
2
S
is made, and an engineering assessment is carried out regarding hydrogen production from
H
2
S
in the Black Sea using a process design based on the catalytic solar thermolysis approach. Possibility of a modular plant is considered for production at larger scale.
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.
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.
