Assessment of feasible strategies for seasonal underground hydrogen storage in a saline aquifer

Renewable energies fluctuate, resulting in temporary mismatches between demand and supply. The conversion of surplus energy to hydrogen and its storage in geological formations is one option to counteract this energy imbalance. This study evaluates the feasibility of seasonal storage of hydrogen produced from wind power in Castilla-León region (northern Spain). A 3D multiphase numerical model is used to test different extraction well configurations during three annual injection-production cycles in a saline aquifer. Results demonstrate that underground hydrogen storage in saline aquifers can be operated with reasonable recovery ratios. A maximum hydrogen recovery ratio of 78%, which represents a global energy efficiency of 30%, has been estimated. Hydrogen upconing emerges as the major risk on saline aquifer storage without using other cushion gases. However, shallow extraction wells can minimize its effects. Steeply dipping geological structures are key for an efficient hydrogen storage.     

Hydrogen storage in saline aquifers: The role of cushion gas for injection and production

Hydrogen stored on a large scale in porous rocks helps alleviate the main drawbacks of intermittent renewable energy generation and will play a significant role as a fuel substitute to limit global warming. This study discusses the injection, storage and production of hydrogen in an open saline aquifer anticline using industry standard reservoir engineering software, and investigates the role of cushion gas, one of the main cost uncertainties of hydrogen storage in porous media.The results show that one well can inject and reproduce enough hydrogen in a saline aquifer anticline to cover 25% of the annual hydrogen energy required to decarbonise the domestic heating of East Anglia (UK). Cushion gas plays an important role and its injection in saline aquifers is dominated by brine displacement and accompanied by high pressures. The required ratio of cushion gas to working gas depends strongly on geological parameters including reservoir depth, the shape of the trap, and reservoir permeability, which are investigated in this study. Generally, deeper reservoirs with high permeability are favoured. The study shows that the volume of cushion gas directly determines the working gas injection and production performance. It is concluded that a thorough investigation into the cushion gas requirement, taking into account cushion gas costs as well as the cost-benefit of cushion gas in place, should be an integral part of a hydrogen storage development plan in saline aquifers.     

Challenges towards hydrogen economy in China

The increasingly serious energy crisis and environmental pollution caused by the excessive use of fossil fuels have been prompting China to aggressively seek a clean and self-sufficient energy source in the future. In the past decades, hydrogen has emerged as a promising alternative due to its advantages of cleanliness, abundance, high energy density, and high conversion efficiency. However, several challenges have to be overcome for China's successful transition to hydrogen economy. In this paper, the hydrogen supply chain is firstly described to help the readers to clearly understand the hydrogen economy. Subsequently, the feasibility of hydrogen economy is discussed by reviewing viewpoints from the literature. Finally, the challenges of China's transition to hydrogen economy are detailed summarized and discussed, and the strategies for China to develop hydrogen economy were compared with that of Japan and Australia.     

Clean hydrogen for mobility – Quo vadis?

Achieving complete combustion of fossil fuels has long been thought of as a sufficient remedy for tackling vehicular emissions and the ensuing environmental effects. However, thanks to the increasing awareness around the climate change, the global dialogue has now shifted to realizing a carbon-free economy, which has set stricter curbs on the energy source that can power the future mobility. Therefore, the idea of “clean combustion” requires rethinking. Of the many choices for alternative clean fuels that are both energy-efficient and environment-friendly, hydrogen has always been eyed as the best clean alternative there is. This article reviews various available approaches to utilizing hydrogen for mobility applications with a discussion of their relative merits and shortcomings. In addition to well-discussed methods like fuel cell electric vehicles, hydrogen-based IC engines, and dual-fuel operation with hydrogen, this review also assesses the technical and economic feasibilities of using hydrogen in e-fuels and their implications for our existing infrastructure and future energy demands.     

Energy system aspects of hydrogen as an alternative fuel in transport

Considering the enormous ecological and economic importance of the transport sector the introduction of alternative fuels—together with drastic energy efficiency gains—will be a key to sustainable mobility, nationally as well as globally. However, the future role of alternative fuels cannot be examined from the isolated perspective of the transport sector. Interactions with the energy system as a whole have to be taken into account. This holds both for the issue of availability of energy sources as well as for allocation effects, resulting from the shift of renewable energy from the stationary sector to mobile applications. With emphasis on hydrogen as a transport fuel for private passenger cars, this paper discusses the energy systems impacts of various scenarios introducing hydrogen fueled vehicles in Germany. It identifies clear restrictions to an enhanced growth of clean hydrogen production from renewable energy sources (RES). Furthermore, it points at systems interdependencies that call for a priority use of RES electricity in stationary applications. Whereas hydrogen can play an increasing role in transport after 2030 the most important challenge is to exploit short–mid-term potentials of boosting car efficiency.     

Prospects and challenges for green hydrogen production and utilization in the Philippines

The Philippines is exploring different alternative sources of energy to make the country less dependent on imported fossil fuels and to reduce significantly the country's CO₂ emissions. Given the abundance of renewable energy potential in the country, green hydrogen from renewables is a promising fuel because it can be utilized as an energy carrier and can provide a source of clean and sustainable energy with no emissions. This paper aims to review the prospects and challenges for the potential use of green hydrogen in several production and utilization pathways in the Philippines. The study identified green hydrogen production routes from available renewable energy sources in the country, including geothermal, hydropower, wind, solar, biomass, and ocean. Opportunities for several utilization pathways include transportation, industry, utility, and energy storage. From the analysis, this study proposes a roadmap for a green hydrogen economy in the country by 2050, divided into three phases: I–green hydrogen as industrial feedstock, II–green hydrogen as fuel cell technology, and III–commercialization of green hydrogen. On the other hand, the analysis identified several challenges, including technical, economic, and social aspects, as well as the corresponding policy implications for the realization of a green hydrogen economy that can be applied in the Philippines and other developing countries.     

Examination of the effect of combustion chamber geometry and mixing ratio on engine performance and emissions in a hydrogen-diesel dual-fuel compression-ignition engine

The fact that fossil fuels, which supply a large amount of the energy need, are limited in the world and can be only found in certain regions, have led humankind to seek alternatives. In addition, the use of fossil fuels generates wastes detrimental to humans and nature, which has led this search to alternative, clean and renewable energy sources. The use of hydrogen, which is a clean energy source, in internal combustion engines is very important in terms of reducing emission values as well as providing an alternative to petroleum-derived fuels. This study presents a literature review on the effect of the hydrogen ratio and combustion chamber geometry on the engine performance and emissions in a compression-ignition engine operating in the hydrogen diesel bi-fuel mode. As a result of the study, it was concluded that the hydrogen energy ratio should be between 5 and 20% and the combustion chamber should be designed by considering the combustion characteristics. The main purpose of the study is to highlight the functionality of the use of hydrogen in dual fuel mode in compression ignition engines and to be a resource for researchers who will work on this subject.     

Underground hydrogen storage to balance seasonal variations in energy demand: Impact of well configuration on storage performance in deep saline aquifers

Grid-scale underground hydrogen storage (UHS) is essential for the decarbonization of energy supply systems on the path towards a zero-emissions future. This study presents the feasibility of UHS in an actual saline aquifer with a typical dome-shaped anticline structure to balance the potential seasonal mismatches between energy supply and demand in the UK domestic heating sector. As a main requirement for UHS in saline aquifers, we investigate the role of well configuration design in enhancing storage performance in the selected site via numerical simulation. The results demonstrate that the efficiency of cyclic hydrogen recovery can reach around 70% in the short term without the need for upfront cushion gas injection. Storage capacity and deliverability increase in successive storage cycles for all scenarios, with the co-production of water from the aquifer having a minimal impact on the efficiency of hydrogen recovery. Storage capacity and deliverability also increase when additional wells are added to the storage site; however, the distance between wells can strongly influence this effect. For optimum well spacing in a multi-well storage scenario within a dome-shaped anticline structure, it is essential to attain an efficient balance between well pressure interference effects at short well distances and the gas uprising phenomenon at large distances. Overall, the findings obtained and the approach described can provide effective technical guidelines pertaining to the design and optimization of hydrogen storage operations in deep saline aquifers.     

Generation of green hydrogen using self-sustained regenerative fuel cells: Opportunities and challenges

The ever-increasing energy demand, depleting fossil fuel reserves, and rising temperatures due to greenhouse gas emissions have necessitated the transition towards the generation of green and clean energy through renewable energy sources. Solar energy is one such renewable energy source that has received significant attention owing to its abundance and inexhaustibility. However, solar energy alone cannot replace fossil fuels in the energy portfolio. There exists a need to develop another clean energy source that can potentially act as an alternative to conventional fuels. Hydrogen proves to be an ideal candidate in this domain and can be sustainably generated by water electrolysis by powering the electrolyzer using solar energy. The hydrogen thus synthesized has net zero carbon emissions and is a suitable asset for decarbonizing the environment. This review encompasses the generation of hydrogen using PV-Electrolyzer systems and addresses the challenges associated with the same. Overcoming these drawbacks can ensure a strong position for hydrogen as an alternative fuel in the energy infrastructure. By employing electrolyzers that are fueled by renewable energy and then using that hydrogen to feed a fuel cell, this study aims to clarify the potential and constraints of producing green hydrogen. Since this area of research has not yet been fully investigated, a review article that enables and encourages academics to develop original solutions is urgently needed.     

A green hydrogen credit framework for international green hydrogen trading towards a carbon neutral future

Hydrogen as a low-carbon clean energy source is experiencing a global resurgence and has been recognized as an alternative energy carrier that can help bring the world to a carbon neutral future. However, getting to scale is one of the main challenges limiting the growth of the hydrogen economy. In particular, the high cost of transporting green hydrogen is bottlenecking the international trading and wider adoption of hydrogen for global carbon natural objectives. In order to explore incentives for the global hydrogen economy and develop new pathways towards the carbon neutral future, the concept of hydrogen credit is proposed by this research and a framework of trading hydrogen credits similar to carbon credits in the international market is established. This research aims to contribute to the overall uptake of green hydrogen financially rather than relying on the physical production, transportation, and storage of hydrogen. Case studies are presented to demonstrate the feasibility and efficiency of the proposed hydrogen credit framework, as well as the great potential of a global hydrogen credit market.     

Carbon black and hydrogen production process analysis

The adoption of new environmentally responsible technologies, as well as, energy efficiency improvements in equipment and processes help to reduce CO2 rate emission into the atmosphere, contributing in delaying the consequences of intensive use of fossil fuels. For more effective actions, it is necessary to make the transition from the fossil-based to the renewable source economy. In this context, hydrogen fuel has a special role as clean vector of energy. Hydrogen has the potential to be decisive in mitigating greenhouse gas emissions, but fossil fuels high profitability due to global energy dependency actually drives the global economy.While renewable energy sources are not worldwide fully established, new technologies should be developed and used for the recovery of energetic streams nowadays wasted, to decarbonize hydrocarbons and to improve systems efficiency creating a path that can help nations and industries in the needed energy economy transition. Hydrogen gas can be generated by various methods from different sources such as coal and water. Currently, almost all of the hydrogen production is for industrial purpose and comes from the Steam Reforming, while the use of hydrogen in fuel cells is only incipient.The article analysis the plasma pyrolysis of hydrocarbons as a decarbonization option to contribute as a step towards hydrogen economy. It presents the Carbon Black and Hydrogen Process (CB&H Process) as an alternative option for hydrogen generation at large scale facility, suitable for supplying large amounts of high-purity carbon in elemental form. CB&H Process refers to a plant with hydrogen thermal plasma reactor able to decompose Hydrocarbons (HC's) into Hydrogen (H2) and Carbon Black (CB), a cleaner technology than its competing processes, capable of generating two products with high added value. Considering the Brazilian context in which more than 80% of the generated electricity comes from renewable sources, the use of electricity as one of the inputs in the process does not compromise the objective of reducing greenhouse gas emissions. It is important to consider that the use of renewable energy to produce two products derived from fossil fuels in a clean way represents integration of technologies into a more efficient system and an arrangement that contributes to the transition from fossil fuels to renewables.The economic viability of the CB&H process as a hydrogen generation unit (centralized) for refining applications also depends on the cost of hydrogen production by competing processes. Steam Methane Reforming (SMR) is a widespread method that produces twice the amount of hydrogen generated by natural gas plasma pyrolysis, but it emits CO2 gas and consumes water, while CB&H process produces solid carbon. For this reason, the paper seeks the carbon production cost by plasma pyrolysis as a breakeven point for large-scale hydrogen generation without water consumption and carbon dioxide emissions.     

Solid air hydrogen liquefaction,the missing link of the hydrogen economy

The most challenging aspect of developing a green hydrogen economy is long-distance oceanic transportation. Hydrogen liquefaction is a transportation alternative. However, the cost and energy consumption for liquefaction is currently prohibitively high, creating a major barrier to hydrogen supply chains. This paper proposes using solid nitrogen or oxygen as a medium for recycling cold energy across the hydrogen liquefaction supply chain. When a liquid hydrogen (LH2) carrier reaches its destination, the regasification process of the hydrogen produces solid nitrogen or oxygen. The solid nitrogen or oxygen is then transported in the LH2 carrier back to the hydrogen liquefaction facility and used to reduce the energy consumption cooling gaseous hydrogen. As a result, the energy required to liquefy hydrogen can be reduced by 25.4% using N₂ and 27.3% using O₂. Solid air hydrogen liquefaction (SAHL) can be the missing link for implementing a global hydrogen economy.     

Safety aspects of future infrastructure scenarios with hydrogen refuelling stations

Hydrogen is currently gaining much attention as a possible future substitute for oil in the transport sector. Hydrogen is not a primary energy source, but can be produced from other sources of energy. A future hydrogen economy will need the establishment of new infrastructures for producing, storing, distributing, dispensing and using hydrogen. Hydrogen can be produced in large-scale centralized facilities or in small-scale on-site systems. Large-scale production requires distribution in pipelines or trucks. A major challenge is to plan the new infrastructures to approach an even safer society regarding safe use of hydrogen. The paper will, on the basis of some scenarios for hydrogen deployment, highlight and discuss safety aspects related to future hydrogen economy infrastructures.     

Viability analysis of centralized hydrogen generation plant for use in mobility sector

Nowadays, the use of renewable energy sources is one of the keys to achieve the sustainable development of societies. The intensive use of fossil fuels has caused effects in the environment and the human health. Greenhouse gas emissions and the carcinogenic effect of diesel are widely demonstrated. The production of clean energy based on renewable sources and the use of hydrogen as an energy vector in general and as an alternative fuel in particular represent a technically feasible reality. However, it is necessary to study the economic variables of centralized or distributed production of hydrogen as an alternative fuel. The aim of this paper is to analyze the technical and economic viability of a centralized generation hydrogen plant for mobility use. It was performed a sensitivity analysis of main parameters such as size of hydrogen production plant, operating hours of the plant, investment costs of the main equipment and electricity price. A NPV of 1,272,692 and a 9-year pay-back were obtained for a centralized hydrogen production plant of 2 MW, considering commercial values of the main evaluation parameters. The sensitivity analysis determines that the main variables affecting the NPV are the price of electricity and the operating hours of the plant. With 95% of confidence, the NPV will be positive with an 80.19% of certainty. Therefore, centralized hydrogen production represents a technically viable, environmentally friendly and economically attractive process that can rapidly position hydrogen as an alternative fuel for mobility.     

Experimental study of engine performance and emissions for hydrogen diesel dual fuel engine with exhaust gas recirculation

With an alarming enlargement in vehicular density, there is a threat to the environment due to toxic emissions and depleting fossil fuel reserves across the globe. This has led to the perpetual exploration of clean energy resources to establish sustainable transportation. Researchers are continuously looking for the fuels with clean emission without compromising much on vehicular performance characteristics which has already been set by efficient diesel engines. Hydrogen seems to be a promising alternative fuel for its clean combustion, recyclability and enhanced engine performance. However, problems like high NOx emissions is seen as an exclusive threat to hydrogen fuelled engines. Exhaust gas recirculation (EGR), on the other hand, is known to overcome the aforementioned problem. Therefore, this study is conducted to study the combined effect of hydrogen addition and EGR on the dual fuelled compression ignition engine on a single cylinder diesel engine modified to incorporate manifold hydrogen injection and controlled EGR. The experiments are conducted for 25%, 50%, 75% and 100% loads with the hydrogen energy share (HES) of 0%, 10% and 30%. The EGR rate is controlled between 0%, 5% and 10%. With no substantial decrement in engine's brake thermal efficiency, high gains in terms of emissions are observed due to synergy between hydrogen addition and EGR. The cumulative reduction of 38.4%, 27.4%, 33.4%, 32.3% and 20% with 30% HES and 10% EGR is observed for NOx, CO2, CO, THC and PM, respectively. Hence, the combination of hydrogen addition and EGR is observed to be advantageous for overall emission reduction.     

Capacity assessment and cost analysis of geologic storage of hydrogen: A case study in Intermountain-West Region USA

Hydrogen is an integral component of the current energy transition roadmap to decarbonize the economy and create an environmentally-sustainable future. However, surface storage options (e.g., tanks) do not provide the required capacity or durability to deploy a regional or nationwide hydrogen economy. In this study, we have analyzed the techno-economic feasibility of the geologic storage of hydrogen in depleted gas reservoirs, salt caverns, and saline aquifers in the Intermountain-West (I-WEST) region. We have identified the most favorable candidate sites for hydrogen storage and estimated the volumetric storage capacity. Our results show that the geologic storage of hydrogen can provide at least 72% of total energy consumption of the I-WEST region in 2020. We also calculated the capital and levelized costs of each storage option. We found that a depleted gas reservoir is the most cost-effective candidate among the three geologic storage options. Interestingly, the cushion gas type plays a significant role in the storage cost when we consider hydrogen storage in saline aquifers. The levelized costs of hydrogen storage in depleted gas reservoirs, salt caverns, and saline aquifers with large-scale storage capacity are approximately $1.15, $2.50, and $3.27 per kg of H₂, respectively. This work provides essential guidance for the geologic hydrogen storage in the I-WEST region.     

A review of four case studies assessing the potential for hydrogen penetration of the future energy system

Hydrogen as an energy carrier allows the decarbonization of transport, industry, and space heating as well as storage for intermittent renewable energy. The objective of this paper is to assess the future engineering potential for hydrogen and provide insight to areas of research to help lower economic barriers for hydrogen adoption. This assessment was accomplished by creating top-level system models based on energy requirements for end-use services. Those models were used to investigate four case studies that provide a global view augmented with specific national examples. The first case study assesses the potential penetration of hydrogen using a global energy system model. The second applies the dynamic integrated climate–ecosystem–economics model to derive an estimate of the impact of the diffusion of hydrogen as an energy carrier. The third determines the required growth in renewable power and water usage to power transportation in the United States (US) with hydrogen. The fourth assesses the use of hydrogen for heating in the United Kingdom (UK). In all cases, there appeared to be significant potential for hydrogen adoption and net energetic benefit. Globally, hydrogen has the potential to account for approximately 3% of energy consumption by 2050. In the US, using hydrogen for on-road transportation could enable a reduction in rejected energy of nearly 10%. Also, hydrogen might provide the least cost alternative to decarbonizing space heating in the UK. The research highlights a challenge raised by widespread abandonment of nuclear power. It is currently unclear what the removal of nuclear would do to the cost of energy as nations attempt to limit global greenhouse gas emissions. Nuclear power has also been proposed as a source for large scale production of hydrogen. Finally, this analysis shows that with today's technological maturity making the transition to a hydrogen economy would incur significant costs.     

Silicon Fuel: A hydrogen storage material

Considerable effort is focused on developing alternative approaches to generating and storing energy to reduce the world's reliance on fossil fuels. Hydrogen offers one such alternative, which is zero-emission at the point of use when used to supply a fuel cell to generate electricity. However, the availability of hydrogen by methods that are both cost-effective and environmentally friendly remains a significant challenge.The formulation presented in this work, which we call Silicon Fuel, contains 90% silicon and can generate high hydrogen yields of 70% or more in just a few minutes. This means that the dry material effectively has a hydrogen content of at least 9 wt% and a realistic specific energy of at least 1.5 kWh/kg if the hydrogen supplies a fuel cell with 50% efficiency. As the hydrogen can be generated in a commercially useful time frame, it is suitable for applications such as automotive refuelling, where consumers expect to be able to refuel their vehicle within a few minutes.     

The importance of hydrogen for energy diversity of Turkey's energy production: 2030 projection

Hydrogen and hydrogen-related technologies will have an important role in world energy projection in the near future. Interest in hydrogen technologies will also increase, especially due to the smart cities concept and the increase in renewable energy supply. In addition to being a clean energy source, the tendency of hydrogen to 100% renewable energy supply makes it ahead of other alternative fuels. The share of hydrogen and related energy technologies in reducing global warming and emissions will continue to increase day by day. For this reason, projections and investment opportunities should be determined for the coming years. In energy projections, the evaluation of hydrogen in terms of energy diversity until 2030 is carried out with EnergyPlan software. Accordingly, the reduction in the amount of emissions and costs were determined by mixing hydrogen into the natural gas pipelines by 5–10, and 20% by volume by producing electrolyzers with photovoltaic systems and according to the number of vehicles with fuel cells in the transportation sector until 2030.     

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.