Institution of Gas Engineers & Managers

Globally reducing CO2 emissions is an urgent priority. The hydrogen economy is a system that offers long-term solutions for a secure energy future and the CO2 crisis. From hydrogen production to consumption storing systems are the foundation of a viable hydrogen economy. Each step has been the topic of intense research for decades; however the development of a viable safe and efficient strategy for the storage of hydrogen remains the most challenging one. Storing hydrogen in polymer-based carriers can realize a more compact and much safer approach that does not require high pressure and cryogenic temperature with the potential to reach the targets determined by the United States Department of Energy. This review highlights an outline of the major polymeric material groups that are capable of storing and releasing hydrogen reversibly. According to the hydrogen storage results there is no optimal hydrogen storage system for all stationary and automotive applications so far. Additionally a comparison is made between different polymeric carriers and relevant solid-state hydrogen carriers to better understand the amount of hydrogen that can be stored and released realistically.

Energy supplies that are safe environmentally friendly dependable and cost-effective are important for society's long-term growth and improved living standards though political social and economic barriers may inhibit their availability. Constantly increasing energy demand is induced by substantial population growth and economic development putting an increasing strain on fossil fuel management and sustainability which account for a major portion of this rising energy demand and moreover creates difficulties because of greenhouse gas emissions growth and the depletion of resources. Such impediments necessitate a global shift away from traditional energy sources and toward renewables. Aside from its traditional role is viewed as a promising energy vector and is gaining international attention as a promising fuel path as it provides numerous benefits in use case scenarios and unlike other synthesized carbon-based fuels could be carbon-free or perhaps even negative on a life-cycle criterion. Hydrogen ( ) is one of the most significant chemical substances on earth and can be obtained as molecular dihydrogen through various techniques from both non-renewable and renewable sources. The drive of this paper is to deliver a technological overview of hydrogen production methods. The major challenges development and research priorities and potential prospects for production was discussed.

The future of a carbon-free society relies on the alignment of the intermittent production of renewable energy with our continuous and increasing energy demands. Long-term energy storage in molecules with high energy content and density such as ammonia can act as a buffer versus short-term storage (e.g. batteries). In this paper we demonstrate that the Haber–Bosch ammonia synthesis loop can indeed enable a second ammonia revolution as energy vector by replacing the CO2 intensive methane-fed process with hydrogen produced by water splitting using renewable electricity. These modifications demand a redefinition of the conventional Haber–Bosch process with a new optimisation beyond the current one which was driven by cheap and abundant natural gas and relaxed environmental concerns during the last century. Indeed the switch to electrical energy as fuel and feedstock to replace fossil fuels (e.g. methane) will lead to dramatic energy efficiency improvements through the use of high efficiency electrical motors and complete elimination of direct CO2 emissions. Despite the technical feasibility of the electrically-driven Haber–Bosch ammonia the question still remains whether such revolution will take place. We reveal that its success relies on two factors: increased energy efficiency and the development of small-scale distributed and agile processes that can align to the geographically isolated and intermittent renewable energy sources. The former requires not only higher electrolyser efficiencies for hydrogen production but also a holistic approach to the ammonia synthesis loop with the replacement of the condensation separation step by alternative technologies such as absorption and catalysis development. Such innovations will open the door to moderate pressure systems the development and deployment of novel ammonia synthesis catalysts and even more importantly the opportunity for integration of reaction and separation steps to overcome equilibrium limitations. When realised green ammonia will reshape the current energy landscape by directly replacing fossil fuels in transportation heating electricity etc. and as done in the last century food.

Hydrogen addition can improve the performance and extend the lean burn limit of gasoline engines. Different hydrogen injection strategies lead to different types of hydrogen mixture distribution (HMD) which affects the engine performance. Therefore the present study experimentally investigated the effects of hydrogen injection strategy on the combustion and emissions of a hydrogen/gasoline dual-fuel port-injection engine under lean-burn conditions. Four different hydrogen injection strategies were explored: hydrogen direct injection (HDI) forming a stratified hydrogen mixture distribution (SHMD); hydrogen intake port injection forming a premixed hydrogen mixture distribution (PHMD); split hydrogen direct injection (SHDI) forming a partially premixed hydrogen mixture distribution (PPHMD); and no hydrogen addition (NHMD). The results showed that 20% hydrogen addition could extend the lean burn limit from 1.5 to 2.8. With the increase in the excess air ratio the optimum HMD changed from PPHMD to SHMD. The maximum brake thermal efficiency was obtained with an excess air ratio of 1.5 with PPHMD. The coefficient of variation (COV) with NHMD was higher than that with hydrogen addition since the hydrogen enhanced the stability of ignition and combustion. The engine presented the lowest emissions with PHMD. There were almost no carbon monoxide (CO) and nitrogen oxides (NOx) emissions when the excess air ratio was respectively more than 1.4 and 2.0.

This study proposes a novel hybrid solar-gas power and hydrogen-production system which is comprised by the solar tower thermal system gas-steam turbine combined cycle and organic Rankine cycle-based hydrogen-production system. Based on the Ebsilon code the operation processes of the hybrid system are simulated. The results show that the output power and electric efficiency of the hybrid system are 103.9 MW and 41.3% and the daily hydrogen output is 62.2 kg. The operation simulation results of the hybrid system reveal that the gas-steam combined cycle and solar island can both achieve stable operations and the power generation section and hydrogen-production device can both work effectively which means the hybrid system is technically feasible. The exergy estimate results of the hybrid system show that the combustion chamber and solar receiver have the two largest exergy destructions which are 56.5 MW and 45.3 MW. That means the performances of the two components can be further improved. For the hydrogen-production system the exergy destructions of the proton exchange membrane electrolyzer turbine condenser and evaporator of the organic Rankine cycle are 0.156 MW 0.111 MW 2.338 MW and 1.891 MW and the corresponding exergy efficiencies are 51.2% 92.6% 80.7% and 79.5% respectively.

Hydrogen futures are in the making right in front of our eyes and will determine socio-ecological path dependencies for decades to come. However expertise on the societal effects of the hydrogen transition is in its infancy. Future energy research needs to include the social sciences humanities and interdisciplinary studies: energy cultures have to be examined as well as  power relations and anticipation processes since the need for (green) hydrogen is likely to require a massive expansion of renewable energy plants.

Direct injection of alternative fuels (biomethane hydrogen) in the natural gas grid appears to be a promising solution to reach environmental objectives of CO2 emission reduction in the current energy scenario. This approach is justified by the large amount of biogas producible which can be upgraded to biomethane; while another proposed solution to increase renewable energy sources exploitation lies in producing hydrogen from excess wind energy followed by injection in the natural gas grid. Nevertheless compliance with composition limits and quality constraints in the resulting natural gas mixture has to be analysed in both stationary and dynamic operations tracking the gas quality downstream the injection point of the alternative fuels. A model was developed to simulate unsteady operation of a portion of gas grid dealing with realistic industrial and residential consumptions concentrated in offtake points. Two case studies were investigated focusing on the comparison between different amounts of hydrogen injection in the pure natural gas flow yielding composition flow rate and pressure profiles. The analysis shows how imposed quality thresholds can be respected although the hydrogen fraction within the natural gas mixture is highly sensitive to the profile and size of the loads connected to the gas pipeline.

The hydrogen permeation behavior of QP1180 high strength steel for automobile was studied in simulate coastal atmosphere environment by using Devanathan-Stachurski dual electrolytic cell the cyclic corrosion test (CCT) thermal desorption spectrometry (TDS) and electrochemical measurement methods. The current density of hydrogen permeation generally increases with reducing the relative humidity from 95% to 50% and periodically changes in the CCT process. These mainly result from the evolution of corrosion and rust layer on the specimen surface with the atmospheric humidity and intermittent salt spraying. The contents of diffusible hydrogen and non-diffusible hydrogen in the steel enlarge slightly in the CCT process. The plastic deformation about 11.3% results in much higher diffusible hydrogen content in steel but noticeably reduces the hydrogen permeation current and almost has no influence on the non-diffusible hydrogen content. The combination of double electrolytic cell and standard cyclic corrosion test can effectively characterize the hydrogen permeation of high strength steel in atmospheric service environments.

Hydrogen fuel cells have been installed in more than 100 facilities and numerous homes in Ulsan hydrogen town in the Republic of Korea. Despite the advantages of hydrogen accidents can still occur near residential areas. Thus appropriate risk mitigation plans should be established. In this study a computational fluid dynamics (CFD) model of natural and forced ventilation is presented as an emergency response to hydrogen leakages in pressure regulator equipment housing. The CFD model is developed and investigated using three vent configurations: UP CROSS and UP-DOWN. The simulation results indicate that the UPDOWN configuration achieves the lowest internal hydrogen concentration out of the three. In addition the relationship between the total vent size and internal hydrogen concentration is determined. A vent size of 12% of the floor area has the lowest hydrogen concentration. The use of nitrogen for forced ventilation during emergencies is proposed to ensure that the hydrogen concentration of the released gas is less than one-fourth of the lower flammability  2 / 25 limit of hydrogen. Compared to natural ventilation the time required to reach safe conditions is decreased when nitrogen forced ventilation is used.

In 2021 only 6 hydrogen fuelling station have been built in Italy of which 3 are not operational and only 1 is open to the public while the rest are built in private or industrial areas. While fuelling station which store more than 5000 kg of hydrogen are subjected to the “Seveso Directive” the permitting procedure for refuelling station which store less than the threshold is supervised by the fire brigade command of the province where the station is built. Recently in the effort to easy the permitting procedure to establish new stations a Ministerial Decree was published in the official gazette of the Italian Republic which lists minimum safety features and safety distances that if respected guarantee the approval by the authority. Nevertheless the imposed distances are such that the land required to build the station constitute a barrier rather than a facilitation. Exploiting the possibility introduced by the Decree to calculate safety distances following a Fire Safety Engineering approach a method is proposed for calculation of safety distances. The present paper presents the Italian regulation and describes an approach to calculate the safety distances including an example applied on the dispenser.