T. Nejat Veziroglu

Hydrogen production by biological processes: a survey of literature

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.

21st Century's Energy: Hydrogen Energy System

Abstract 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.

From hydrogen economy to hydrogen civilization

For the first time ever, the main aspects of a move by humankind into the era of an ecologically clean hydrogen energy civilization are being considered. It has been shown that energy and environmental problems can be averted by changing our energy carrier from fossil fuels to the environmentally clean energy carrier, hydrogen. The biospheric and noospheric consequences of this transition have been analyzed. The steps to be taken for the move to such a future hydrogen civilization have been discussed.

Quarter century of hydrogen movement 1974–2000☆

A quarter of a century has passed since the beginning of the Hydrogen Energy Movement. Over the past 25 years, there have been accomplishments on every front - from the acceptance of the concept as an answer to energy and environment related global problems - to research, development and commercialization. The Hydrogen Energy System has now taken firm roots. Activities towards the implementation are accelerating.

A step on the road to Hydrogen Civilization

Abstract The Third International Conference “Hydrogen Treatment of Materials” (HTM-2001), Donetsk, May 14–18, 2001 was the first international hydrogen meeting held under the effect of a new conception “From a Hydrogen Economy to a Hydrogen Civilization”, which was first developed by V.A. Goltsov and T.N. Veziroglu. That was a meeting of the representatives of three subcommunities of the world hydrogen movements: the hydrogen energy subcommunity, the hydrogen-materials subcommunities and the subcommunity of industrialists ensuring safety and efficiency of hydrogen use in terms of the up-to-date industry. More than 130 members from 60 organizations in the USA, Great Britain, Spain, Poland, Russia, Ukraine, Libya and Japan took part in the conference. Such a participation let the conference cover the achievements of hydrogen economy, hydrogen treatment of materials, and global subjects of a transition to Hydrogen Civilization of the future. At the final plenary meeting, the participants discussed and adopted the memorandum calling upon the world community, peoples and states to unite their efforts and to contribute with all the expertise attained to the transition of the humankind to the era of Hydrogen Civilization.

A Solar-Hydrogen Energy System for Environmental Compatibility

Our Biosphere, the only one known to exist, is under attack by various factors. Major culprits amongst these include fossil-fuel-produced air pollution, acidic precipitation (acid rains), and CO 2 . As we run out of petroleum and natural gas, the question becomes: what should the new energy-system be, so that the damage to The Biosphere and life can be stopped? In view of the rapid depletion of the main energy sources of the present, the fluid fossil-fuels, this paper analyses the various primary energy-options (such as coal, breeder reactors, fusion reactors, and solar energy), and also considers such possible energy-carriers as synthetic fossil-fuels and hydrogen. In this analysis, the environmental effects of various options are considered both qualitatively and quantitatively. It is concluded that the Hydrogen Energy-system is the most efficient and economical energy-system possible, and that it results in the environmentally most compatible and permanent energy-system when coupled with solar energy as the primary energy-source. It is important now that this information be disseminated among the public in general, and environmentalists in particular, so that the implementation of the solar-hydrogen economy can be started without delay, in order to minimize any further damage to The Biosphere and its living components.

Solar–Hydrogen Energy System: The Choice of the Future

As a result of the foregoing study, the following conclusions are reached: (A) The solar–hydrogen energy system is environmentally far more compatible than the fossil-fuel system; it is actually the only solution for the carbon-dioxide-induced ‘greenhouse’ effect and its threatening consequences. (B) The utilization efficiencies of hydrogen are greater than those of fossil and synthetic fossil fuels; therefore, in the hydrogen-energy system, less energy will be required to perform the same services

Numerical investigation of heat and mass transfer in a metal hydride bed

This paper presents a mathematical model for hydrogen storage in a metal hydride bed. For this purpose, a two-dimensional mathematical model which considers complex heat and mass transfer during the hydriding process is developed. The coupled differential equations are solved with a numerical method based on integrations of governing equation over finite control volumes. The driving force is considered to be pressure difference because of the temperature distribution in the system. The numerical results showed that the hydriding performance depends on the temperature distribution in the hydride bed. Fluid flow enhances the hydriding rate in the system by driving the hot fluid to the colder regions. The numerical results were found to agree satisfactorily with the experimental data available in the literature.

A universal relationship for estimating clear sky insolation

An investigation of estimating clear sky insolation1 has been conducted. Some discrepancies have been found between the conventional method of estimation and the data. It has been noticed that the conventional method underestimates the insolation. A simpler, more elegant and more accurate “universal” relationship has been derived for estimating the annual mean daily clear sky insolation as a function of the latitude and altitude of a given location. As part of this derivation, two simple and accurate correlations have been obtained, i.e. for extraterrestrial insolation and for atmospheric attenuation.

THERMAL CONDUCTANCE OF TWO-DIMENSIONAL CONSTRICTIONS

Thermal conductance of two dimensional constrictions using symmetrical and eccentric configurations