Steps toward the hydrogen economy

The hydrogen economy is defined as the industrial system in which one of the universal energy carriers is hydrogen (the other is electricity) and hydrogen is oxidized to water that may be reused by applying an external energy source for dissociation of water into its component elements hydrogen and oxygen. There are three different primary energy-supply system classes which may be used to implement the hydrogen economy, namely, fossil fuels (coal, petroleum, natural gas, and as yet largely unused supplies such as shale oil, oil from tar sands, natural gas from geo-pressured locations, etc.), nuclear reactors including fission reactors and breeders or fusion nuclear reactors over the very long term, and renewable energy sources (including hydroelectric power systems, wind-energy systems, ocean thermal energy conversion systems, geothermal resources, and a host of direct solar energy-conversion systems including biomass production, photovoltaic energy conversion, solar thermal systems, etc.). Examination of present costs of hydrogen production by any of these means shows that the hydrogen economy favored by people searching for a non-polluting gaseous or liquid energy carrier will not be developed without new discoveries or innovations. Hydrogen may become an important market entry in a world with most of the electricity generated in nuclear fission or breeder reactors when high-temperature waste heat is used to dissociate water in chemical cycles or new inventions and innovations lead to low-cost hydrogen production by applying as yet uneconomical renewable solar techniques that are suitable for large-scale production such as direct water photolysis with suitably tailored band gaps on semiconductors or low-cost electricity supplies generated on ocean-based platforms using temperature differences in the tropical seas.     

Integrated hydrogen production options based on renewable and nuclear energy sources

Due to varied global challenges, potential energy solutions are needed to reduce environmental impact and improve sustainability. Many of the renewable energy resources are of limited applicability due to their reliability, quality, quantity, and density. Thus, the need remains for additional sustainable and reliable energy sources that are sufficient for large-scale energy supply to complement and/or back up renewable energy sources. Nuclear energy has the potential to contribute a significant share of energy supply with very limited impacts to global climate change. Hydrogen production via thermochemical water decomposition is a potential process for direct utilization of nuclear thermal energy. Nuclear hydrogen and power systems can complement renewable energy sources by enabling them to meet a larger extent of global energy demand by providing energy when the wind does not blow, the sun does not shine, and geothermal and hydropower energies are not available. Thermochemical water splitting with a copper–chlorine (Cu–Cl) cycle could be linked with nuclear and selected renewable energy sources to decompose water into its constituents, oxygen and hydrogen, through intermediate copper and chlorine compounds. In this study, we present an integrated system approach to couple nuclear and renewable energy systems for hydrogen production. In this regard, nuclear and renewable energy systems are reviewed to establish some appropriate integrated system options for hydrogen production by a thermochemical cycle such as Cu–Cl cycle. Several possible applications involving nuclear independent and nuclear assisted renewable hydrogen production are proposed and discussed. Some of the considered options include storage of hydrogen and its conversion to electricity by fuel cells when needed.     

Nuclear hydrogen: An assessment of product flexibility and market viability

Nuclear energy has the potential to play an important role in the future energy system as a large-scale source of hydrogen without greenhouse gas emissions. Thus far, economic studies of nuclear hydrogen tend to focus on the levelized cost of hydrogen without accounting for the risks and uncertainties that potential investors would face. We present a financial model based on real options theory to assess the profitability of different nuclear hydrogen production technologies in evolving electricity and hydrogen markets. The model uses Monte Carlo simulations to represent uncertainty in future hydrogen and electricity prices. It computes the expected value and the distribution of discounted profits from nuclear hydrogen production plants. Moreover, the model quantifies the value of the option to switch between hydrogen and electricity production, depending on what is more profitable to sell. We use the model to analyze the market viability of four potential nuclear hydrogen technologies and conclude that flexibility in output product is likely to add significant economic value for an investor in nuclear hydrogen. This should be taken into account in the development phase of nuclear hydrogen technologies.     

Hybrid systems to address seasonal mismatches between electricity production and demand in nuclear renewable electrical grids

A strategy to enable zero-carbon variable electricity production with full utilization of renewable and nuclear energy sources has been developed. Wind and solar systems send electricity to the grid. Nuclear plants operate at full capacity with variable steam to turbines to match electricity demand with production (renewables and nuclear). Excess steam at times of low electricity prices and electricity demand go to hybrid fuel production and storage systems. The characteristic of these hybrid technologies is that the economic penalties for variable nuclear steam inputs are small. Three hybrid systems were identified that could be deployed at the required scale. The first option is the gigawatt-year hourly-to-seasonal heat storage system where excess steam from the nuclear plant is used to heat rock a kilometer underground to create an artificial geothermal heat source. The heat source produces electricity on demand using geothermal technology. The second option uses steam from the nuclear plant and electricity from the grid with high-temperature electrolysis (HTR) cells to produce hydrogen and oxygen. Hydrogen is primarily for industrial applications; however, the HTE can be operated in reverse using hydrogen for peak electricity production. The third option uses variable steam and electricity for shale oil production.     

Analysis of solar hydrogen production in Algeria: Case of an electrolyzer-concentrating photovoltaic system

The use of renewable energy and more particularly solar energy in hydrogen production is considered the most viable and the most environment protective. Electricity is required for water electrolysis to produce hydrogen. As photovoltaic modules enable the direct conversion of solar energy into electricity, photovoltaic systems are then the most indicated systems for this task.     

Hydrogen production by coupling pressurized high temperature electrolyser with solar tower technology

Solar hydrogen production by coupling of pressurized high temperature electrolyser with concentrated solar tower technology is studied. As the high temperature electrolyser requires constant temperature conditions, the focus is made on a molten salt solar tower due to its high storage capacity. A flowsheet was developed and simulations were carried out with Aspen Plus 8.4 software for MW-scale hydrogen production plants. The solar part was laid out with HFLCAL software. Two different scenarios were considered: the first concerns the production of 400 kg/d hydrogen corresponding to mobility use (fuel station). The second scenario deals with the production of 4000 kg/d hydrogen for industrial use. The process was analyzed from a thermodynamic point of view by calculating the overall process efficiency and determining the annual production. It was assumed that a fixed hydrogen demand exists in the two cases and it was assessed to which extent this can be supplied by the solar high temperature electrolysis process including thermal storage as well as hydrogen storage. For time periods with a potential over supply of hydrogen, it was considered that the excess energy is sold as electricity to the grid. For time periods where the hydrogen demand cannot be fully supplied, electricity consumption from the grid was considered. It was assessed which solar multiple is appropriate to achieve low consumption of grid electricity and low excess energy. It is shown that the consumption of grid electricity is reduced for increasing solar multiple but the efficiency is also reduced. At a solar multiple of 3.0 an annual solar-to-H₂ efficiency greater than 14% is achieved at grid electricity production below 5% for the industrial case (4000 kg/d). In a sensitivity study the paramount importance of electrolyser performance, i.e. efficiency and conversion, is shown.     

Large-vscale hydrogen production and storage technologies: Current status and future directions

Over the past years, hydrogen has been identified as the most promising carrier of clean energy. In a world that aims to replace fossil fuels to mitigate greenhouse emissions and address other environmental concerns, hydrogen generation technologies have become a main player in the energy mix. Since hydrogen is the main working medium in fuel cells and hydrogen-based energy storage systems, integrating these systems with other renewable energy systems is becoming very feasible. For example, the coupling of wind or solar systems hydrogen fuel cells as secondary energy sources is proven to enhance grid stability and secure the reliable energy supply for all times. The current demand for clean energy is unprecedented, and it seems that hydrogen can meet such demand only when produced and stored in large quantities. This paper presents an overview of the main hydrogen production and storage technologies, along with their challenges. They are presented to help identify technologies that have sufficient potential for large-scale energy applications that rely on hydrogen. Producing hydrogen from water and fossil fuels and storing it in underground formations are the best large-scale production and storage technologies. However, the local conditions of a specific region play a key role in determining the most suited production and storage methods, and there might be a need to combine multiple strategies together to allow a significant large-scale production and storage of hydrogen.     

Technoeconomics of large-scale clean hydrogen production – A review

Hydrogen is widely used in many industries, yet its role in the clean energy transition goes beyond being an element of these industries. Near-term practical large-scale clean hydrogen production can be made available by involving nuclear, solar, and other renewable energy sources in the process of hydrogen production, and coupling their energy systems to sustainable carbon-free hydrogen technologies. This requires further investigation and assessment of the different alternatives to achieve clean hydrogen using these pathways. This paper assesses the technoeconomics of promising hydrogen technologies that can be coupled to nuclear and solar energy systems for large-scale hydrogen production. It also provides an overview of the design, status and advances of these technologies.     

Hydrogen production through solar energy water electrolysis

Various methods of making hydrogen from water have been proposed, but at the present time the only practical way to make hydrogen from water without fossil fuel is electrolysis. The development of a new, advanced, water electrolyser has become necessary for use in hydrogen energy systems and in electricity storage systems. All the new possible electrolysis processes, suitable for large-scale plants, are being analysed, in view of their combination with solar electricity source. A study of system interactions between large-scale photovoltaic plants, for electrical energy supply, and water electrolysis, is carried out. The subsystems examined include power conditioning, control and loads, as they are going to operate. Water electrolysis systems have no doubt been improved considerably and are expected to become the principal means to produce a large amount of hydrogen in the coming hydrogen economy age. Thus, the present paper treats the subject of hydrogen energy production from direct solar energy conversion facilities located on the earth's oceans and lakes. Electrolysis interface is shown to be conveniently adapted to direct solar energy conversion, depending on technical and economical feasibility aspects as they emerge from the research phases. The intrinsic requirement for relatively immense solar collection areas for large-scale central conversion facilities, with widely variable electricity charges, is given. The operation of electrolysis and photovoltaic array combination is verified at different insolation levels. Solar cell arrays and electrolysers are giving the expected results during continuously variable solar energy inputs. Future markets will turn more and more towards larger scale systems powering significantly bigger loads, ranging from hundreds of kW to several MW in size. Detailed design and close attention to subsystem engineering in the development of high performance, high efficiency photovoltaic power plants, are carried out. An overall design of a 50 MWp photovoltaic central station for electricity and hydrogen co-generation is finally discussed.     

The sustainability indicators of power production systems

One of the most important elements of economical and social development is to provide uninterrupted electric energy to consumers. The increasing world population and technological developments rapidly increase the demand on electric energy. In order to meet the increasing demand for sustainable development, it is necessary to use the consumable resources of the world in the most productive manner and minimum level and to keep its negative effects on human health and environment in the lowest level as much as possible. In this study, alignment of hydrogen fuel cells, hydroelectric, wind, solar and geothermal sourced electric energy systems, in addition to fossil fueled coal, natural gas and nuclear power plants, in respect to sustainability parameters such as CO₂ emission, land use, energy output, fresh water consumption and environmental and social effects is researched. Consequently, it has been determined that the wind and nuclear energy power plants have the highest sustainability indicators. The fuel cells that use hydrogen obtained by using coal and natural gas are determined as the most disadvantageous transformation technologies in respect to sustainability. This study contains an alignment related to today's technologies. Using of renewable energy resources especially in production of hydrogen, output increases to be ensured with nanotechnology applications in photovoltaic systems may change this alignment.     

Solar and wind opportunities for water desalination in the Arab regions

Despite the abundance of renewable energy resources in the Arab region, the use of solar thermal, solar photovoltaics, and wind is still in its technological and economic infancy. Great potential exists, but economic constraints have impeded more rapid growth for many applications. These technologies have certainly advanced technically over the last quarter century to the point where they should now be considered clean-energy alternatives to fossil fuels. For the Arab countries and many other regions of the world, potable water is becoming as critical a commodity as electricity. As renewable energy technologies advance and environmental concerns rise, these technologies are becoming more interesting partners for powering water desalination projects. We evaluate the current potential and viability of solar and wind, emphasizing the strict mandate for accurate, reliable site-specific resource data. Water desalination can be achieved through either thermal energy (using phase-change processes) or electricity (driving membrane processes), and these sources are best matched to the particular desalination technology. Desalination using solar thermal can be accomplished by multistage flash distillation, multi-effect distillation, vapor compression, freeze separation, and solar still methods. Concentrating solar power offers the best match to large-scale plants that require both high-temperature fluids and electricity. Solar and wind electricity can be effective energy sources for reverse osmosis, electrodialysis, and ultra- and nano-filtration. All these water desalination processes have special operational and high energy requirements that put additional requisites on the use of solar and wind to power these applications. We summarize the characteristics of the various desalination technologies. The effective match of solar thermal, solar photovoltaics, and wind to each of these is discussed in detail. An economic analysis is provided that incorporates energy consumption, water production levels, and environmental benefits in its model. Finally, the expected evolution of the renewable technologies over the near- to mid-term is discussed with the implications for desalination applications over these timeframes.     

Resource assessment for green hydrogen production in Kazakhstan

Kazakhstan has long been regarded as a major exporter of fossil fuel energy. As the global energy sector is undergoing an unprecedented transition to low-carbon solutions, new emerging energy technologies, such as hydrogen production, require more different resource bases than present energy technologies. Kazakhstan needs to consider whether it has enough resources to stay competitive in energy markets undergoing an energy transition. Green hydrogen can be made from water electrolysis powered by low-carbon electricity sources such as wind turbines and solar panels. We provided the first resource assessment for green hydrogen production in Kazakhstan by focusing on three essential resources: water, renewable electricity, and critical raw materials. Our estimations showed that with the current plan of Kazakhstan to keep its water budget constant in the future, producing 2–10 Mt green hydrogen would require reducing the water use of industry in Kazakhstan by 0.6–3% or 0.036–0.18 km³/year. This could be implemented by increasing the share of renewables in electricity generation and phasing out some of the water- and carbon-intensive industries. Renewable electricity potential in South and West Kazakhstan is sufficient to run electrolyzers up to 5700 and 1600 h/year for wind turbines and solar panels, respectively. In our base case scenario, 5 Mt green hydrogen production would require 50 GW solar and 67 GW wind capacity, considering Kazakhstan's wind and solar capacity factors. This could convert into 28,652 tons of nickel, 15,832 tons of titanium, and many other critical raw materials. Although our estimations for critical raw materials were based on limited geological data, Kazakhstan has access to the most critical raw materials to support original equipment manufacturers of low-carbon technologies in Kazakhstan and other countries. As new geologic exploration kicks off in Kazakhstan, it is expected that more deposits of critical raw materials will be discovered to respond to their potential future needs for green hydrogen production.     

Valuation and development of the solar hydrogen production

This article considers Algeria as a case study for the evaluation of the solar hydrogen production potential. The study relates to the design of a hydrogen generating station by water electrolysis whose energy resources are solar. The electricity supply is done by a solar tower power plant. The numerical simulation of the hydrogen production for the installation proposed is made while being based on the characteristic equations governing the electrolysis of water, hydraulic pumping system and the solar tower. The hydrogen production rate is given for various values of the solar radiation and several sites of Algeria. The results obtained by the established computer code, and of which the required goal is the determination of the most favorable conditions for a better production of hydrogen, are presented and discussed.     

Hydrogen: automotive fuel of the future

This work presents a perspective on the production and use of hydrogen as an automotive fuel. Hydrogen has been hailed as the key to a clean energy future primarily because it can be produced from a variety of energy sources, it satisfies all energy needs, it is the least polluting, and it is the perfect carrier for solar energy in that it affords solar energy a storage medium. Efforts are underway to transform the global transportation energy economy from one dependent on oil to that based on sustainable hydrogen. The rationale behind these efforts is that hydrocarbon-based automobiles are a significant source of air pollution, while hydrogen-powered fuel cell vehicles produce effectively zero emissions. Besides the transportation area, fuel cells can also reduce emissions in other applications such as the residential or commercial distributed electricity generation. Hydrogen is the perfect partner for electricity, and together they create an integrated energy system based on distributed power generation and use. A discussion on the sources of hydrogen in the near- and long-term future as well as the cost of hydrogen production is provided.     

An analysis of hydrogen production from renewable electricity sources

Three aspects of producing hydrogen via renewable electricity sources are analyzed to determine the potential for solar and wind hydrogen production pathways: a renewable hydrogen resource assessment, a cost analysis of hydrogen production via electrolysis, and the annual energy requirements of producing hydrogen for refueling. The results indicate that ample resources exist to produce transportation fuel from wind and solar power. However, hydrogen prices are highly dependent on electricity prices. For renewables to produce hydrogen at $2 kg⁻¹, using electrolyzers available in 2004, electricity prices would have to be less than $0.01 kWh⁻¹. Additionally, energy requirements for hydrogen refueling stations are in excess of 20 GWh/year. It may be challenging for dedicated renewable systems at the filling station to meet such requirements. Therefore, while plentiful resources exist to provide clean electricity for the production of hydrogen for transportation fuel, challenges remain to identify optimum economic and technical configurations to provide renewable energy to distributed hydrogen refueling stations.     

Cost and performance sensitivity studies for solar photovoltaic/electrolytic hydrogen systems

In previous work, we have investigated the implications of projected advances in thin film solar cell technology for producing electrolytic hydrogen from photovoltaic (PV) electricity. These studies indicate that if year 2000 cost and efficiency goals for thin film solar cells are achieved, PV hydrogen produced in the Southwestern U.S. could become roughly cost competitive with other synthetic fuels for applications such as automotive transport and residential heating, if efficient energy use is stressed. This suggests that PV hydrogen could potentially play a significant role in future energy supply.However, the estimated production cost of PV hydrogen depends on the cost and performance parameters assumed for the PV hydrogen system. In this paper we investigate the sensitivity of PV hydrogen production costs to changes in the system parameters and identify key conditions for low cost PV hydrogen production.     

Prospects of hydrogen production potential from renewable resources in Algeria

Hydrogen production from renewable energies is a key part in the energy transition to realize a sustainable energy economy for both developed and developing nations. For Algeria, successful energy transition toward a hydrogen economy will require the establishment of its potential. This study was conducted to estimate the potential for producing hydrogen from renewable resources in Algeria. The renewable energies considered are: solar photovoltaic and wind. To accomplish this objective, first, we analyzed renewable resource data both statistically and graphically using Geographical Information System (GIS), a computer-based information system utilized to create and visualize the spatial distribution of the geographic information. Then, the study will evaluate the availability of renewable electricity production potential from these key renewable resources. The potential for the hydrogen production, via the electrolysis process with wind and solar photovoltaic electricity, is described with maps showing it per unit area in each region. Finally, the results of the estimated hydrogen potential from both resources for each region are compared and significant conclusions are drawn.     

Nanocrystalline solar cells

The quality of human life depends to a large degree on the availability of energy sources. The present worldwide energy consumption exceeds already the level of 6000 Gigawatt. It is expected to further increase sharply from the rising demand of energy in the developing countries. This implies enhanced depletion of fossil fuel reserves. leading to further aggravation of the environmental pollution exerting adverse effects on the well being of man kind. Adding the dangers arising from the accumulation of plutonium fission products from nuclear reactors, the quality of life on earth is threatened unless renewable energy resources can be developed in the near future. Photovoltaics is expected to make important contributions to identify environmentally friendly solutions of the energy problem. One attractive strategy discussed in this lecture is the development of systems that mimic natural photosynthesis in the conversion solar energy for the fixation of carbon dioxide. The task to be accomplished by these systems is to harvest sun light to produce electricity or drive an uphill chemical reaction, such as the cleavage of water into hydrogen and oxygen. The hydrogen can be subsequently employed to reduce carbon dioxide to produce fuels and chemical feed stocks. Learning from the concepts used by green plants we have developed a molecular photovoltaic device whose overall efficiency for solar energy conversion to electricity has already attained 10%.. The system is based on the sensitization of nanocrystalline films by transition metal charge transfer sensitizers. In analogy to photosynthesis, the new chemical solar cell achieves the separation of light absorption and charge carrier transport. Extraordinary yields for the conversion of incident photons into electric current are obtained, exceeding 90% for transition metal complexes within the wavelength range of their absorption band. Conventional photovoltaic cells for solar energy conversion into electricity are solid state devices do not economically compete for base load utility electricity production. The low cost and ease of production of the new nanocrystalline cell should be benefit large scale applications in particular in underdeveloped or developing countries. These regions of the earth benefit from generous sun shine rendering the availability of a cheap solar cell technology important in view of improving the quality of life and preserving natural resources. Quite aside from its intrinsic merits as a photovoltaic device, the nanocrystalline films development opens up a whole number of additional avenues for energy storage ranging from intercalation batteries to the formation of chemical fuels. These nanocrystalline systems will undoubtedly promote the acceptance of renewable energy technologies, not least by setting new standards of convenience and economy.     

A thorough investigation of solar-powered hydrogen potential and accurate location planning for big cities: A case study

In recent years, hydrogen has constituted a clean energy carrier that can be gained by the use of renewable electricity. The most preliminary stage in the process of renewable hydrogen generation is to find the best place for exploiting the most energy. Thus, this study seeks to optimize the process of location selection for the construction of a solar power station. This evaluation is performed on 12 cities of Isfahan in Iran. After ascertaining 11 criteria of key importance, Window Data Envelopment Analysis (WDEA) Method is used to prioritize the cities according to the data for a period of 11 years. Consequently, the most promising site is technically and economically scrutinized as to hydrogen production using solar electricity. Results pertaining to the first part of the study showed that the city of Natanz was efficient over the entire studied period. Considering 4 cases of different performance rates, annual electricity generation using solar panel model X21-345 and hydrogen production using an alkaline electrolyzer were estimated for the city. The estimations indicated that hydrogen production under the worst and the best cases would be 2.22 kg and 5.55 leading to energy efficiency of between 2.5% and 7.1%, respectively. Finally, economic assessment proved promising results in which Levelized Cost of Electricity (LCOE) would be between 0.5317 and 1.6272 $/kWh and Levelized Cost of Hydrogen (LCOH) would vary from 0.7911 to 1.6778 $/kg.     

Political,economic and environmental impacts of biomass-based hydrogen

The purpose of this study is to assess the political, economic and environmental impacts of producing hydrogen from biomass. Hydrogen is a promising renewable fuel for transportation and domestic applications. Hydrogen is a secondary form of energy that has to be manufactured like electricity. The promise of hydrogen as an energy carrier that can provide pollution-free, carbon-free power and fuels for buildings, industry, and transport makes it a potentially critical player in our energy future. Currently, most hydrogen is derived from non-renewable resources by steam reforming in which fossil fuels, primarily natural gas, but could in principle be generated from renewable resources such as biomass by gasification. Hydrogen production from fossil fuels is not renewable and produces at least the same amount of CO₂ as the direct combustion of the fossil fuel. The production of hydrogen from biomass has several advantages compared to that of fossil fuels. The major problem in utilization of hydrogen gas as a fuel is its unavailability in nature and the need for inexpensive production methods. Hydrogen production using steam reforming methane is the most economical method among the current commercial processes. These processes use non-renewable energy sources to produce hydrogen and are not sustainable. It is believed that in the future biomass can become an important sustainable source of hydrogen. Several studies have shown that the cost of producing hydrogen from biomass is strongly dependent on the cost of the feedstock. Biomass, in particular, could be a low-cost option for some countries. Therefore, a cost-effective energy-production process could be achieved in which agricultural wastes and various other biomasses are recycled to produce hydrogen economically. Policy interest in moving towards a hydrogen-based economy is rising, largely because converting hydrogen into useable energy can be more efficient than fossil fuels and has the virtue of only producing water as the by-product of the process. Achieving large-scale changes to develop a sustained hydrogen economy requires a large amount of planning and cooperation at national and international alike levels.