Climate change and fossil fuel depletion are the main reasons leading to hydrogen technology. There are many processes for hydrogen production from both conventional and alternative energy resources such as natural gas, coal, nuclear, biomass, solar and wind. In this work, a comparative overview of the major hydrogen production methods is carried out. The process descriptions along with the technical and economic aspects of 14 different production methods are discussed. An overall comparison is carried out, and the results regarding both the conventional and renewable methods are presented. The thermochemical pyrolysis and gasification are economically viable approaches providing the highest potential to become competitive on a large scale in the near future while conventional methods retain their dominant role in H2 production with costs in the range of 1.34–2.27 $/kg. Biological methods appear to be a promising pathway but further research studies are needed to improve their production rates, while the low conversion efficiencies in combination with the high investment costs are the key restrictions for water-splitting technologies to compete with conventional methods. However, further development of these technologies along with significant innovations concerning H2 storage, transportation and utilization, implies the decrease of the national dependence on fossil fuel imports and green hydrogen will dominate over the traditional energy resources.

A comparative overview of hydrogen production processes

Fossil fuel consumption in transportation system and energy-intensive sectors as the principal pillar of civilization is associated with progressive release of greenhouse gases. Hydrogen as a promising energy carrier is a perfect candidate to supply the energy demand of the world and concomitantly reduce toxic emissions. This article gives an overview of the state-of-the-art hydrogen production technologies using renewable and sustainable energy resources. Hydrogen from supercritical water gasification (SCWG) of biomass is the most cost effective thermochemical process. Highly moisturized biomass is utilized directly in SCWG without any high cost drying process. In SCWG, hydrogen is produced at high pressure and small amount of energy is required to pressurize hydrogen in the storage tank. Tar and char formation decreases drastically in biomass SCWG. The low efficiency of solar to hydrogen system as well as expensive photovoltaic cell are the most important barriers for the widespread commercial development of solar-based hydrogen production. Since electricity costs play a crucial role on the final hydrogen price, to generate carbon free hydrogen from solar and wind energy at a competitive price with fossil fuels, the electrical energy cost should be four times less than commercial electricity prices.

Hydrogen production from renewable and sustainable energy resources: Promising green energy carrier for clean development

This paper provides an insight to the feasibility of adopting hydrogen as a key energy carrier and fuel source in the near future. It is shown that hydrogen has several advantages, as well as few drawbacks in using for the above purposes. The research shows that hydrogen will be a key player in storing energy that is wasted at generation stage in large-scale power grids by off-peak diversion to dummy loads. The estimations show that by the year of 2050 there will be a hydrogen demand of over 42 million metric tons or 45 billion gallon gasoline equivalent (GGE) in the United States of America alone which can fuel up 342 million light-duty vehicles for 51 × 1011 miles (82 × 1011 km) travel per year. The production at distributed level has also been discussed. The paper also presents the levels of risk in production, storage and distribution stages and proposes possible techniques to address safety issues. It is shown that the storage in small to medium scale containers is much economical compared to doing the same at large-scale containers. The study concludes that hydrogen has a promising future to be a highly feasible energy carrier and energy source itself at consumer level.

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Hydrogen as an energy carrier: Prospects and challenges

Hydrogen is often proposed as the fuel of the future, but the transformation from the present fossil fuel economy to a hydrogen economy will need the solution of numerous complex scientific and technological issues, which will require several decades to be accomplished. Hydrogen is not an alternative fuel, but an energy carrier that has to be produced by using energy, starting from hydrogen-rich compounds. Production from gasoline or natural gas does not offer any advantage over the direct use of such fuels. Production from coal by gasification techniques with capture and sequestration of CO₂ could be an interim solution. Water splitting by artificial photosynthesis, photobiological methods based on algae, and high temperatures obtained by nuclear or concentrated solar power plants are promising approaches, but still far from practical applications. In the next decades, the development of the hydrogen economy will most likely rely on water electrolysis by using enormous amounts of electric power, which in its turn has to be generated. Producing electricity by burning fossil fuels, of course, cannot be a rational solution. Hydroelectric power can give but a very modest contribution. Therefore, it will be necessary to generate large amounts of electric power by nuclear energy of by renewable energies. A hydrogen economy based on nuclear electricity would imply the construction of thousands of fission reactors, thereby magnifying all the problems related to the use of nuclear energy (e.g., safe disposal of radioactive waste, nuclear proliferation, plant decommissioning, uranium shortage). In principle, wind, photovoltaic, and concentrated solar power have the potential to produce enormous amounts of electric power, but, except for wind, such technologies are too underdeveloped and expensive to tackle such a big task in a short period of time. A full development of a hydrogen economy needs also improvement in hydrogen storage, transportation and distribution. Hydrogen and electricity can be easily interconverted by electrolysis and fuel cells, and which of these two energy carriers will prevail, particularly in the crucial field of road vehicle powering, will depend on the solutions found for their peculiar drawbacks, namely storage for electricity and transportation and distribution for hydrogen. There is little doubt that power production by renewable energies, energy storage by hydrogen, and electric power transportation and distribution by smart electric grids will play an essential role in phasing out fossil fuels.

The hydrogen issue

This paper examines the present status of hydrogen energy and looks at different approaches for technological advances. Some of the new developments in the progress of the recent directions of world hydrogen production and utilization are reported. The aim of this article is to inform the reader of hydrogen technology, economics, environmental impact, special system applications, hydrogen energy status around the world at the end of the 20 century as well as hydrogen organizations, associations, projects, periodicals and conferences.

Magdalena Momirlan

Papers

The properties of hydrogen as fuel tomorrow in sustainable energy system for a cleaner planet

Statistics of TiO2 crystal growth in air on a metallic surface heated at temperatures in the range of 900–1100°C

Structure of zeolites used in hydrogen evolution from water

The use of solar energy in hydrogen production

Pressure and temperature effects on water dissociation reaction for hydrogen production over zeolites