Transmission, Distribution & Storage

Hydrogen has been studied extensively as a potential enabler of the energy transition from fossil fuels to renewable sources. It promises a feasible decarbonisation route because it can act as an energy carrier a heat source or a chemical reactant in industrial processes. Hydrogen can be produced via renewable energy sources such as solar hydro or geothermic routes and is a more stable energy carrier than intermittent renewable sources. If hydrogen can be stored efficiently it could play a crucial role in decarbonising industries. For hydrogen to be successfully implemented in industrial systems its impact on infrastructure needs to be understood quantified and controlled. If hydrogen technology is to be economically feasible we need to investigate and understand the retrofitting of current industrial infrastructure. Currently there is a lack of comprehensive knowledge regarding alloys and components performance in long-term hydrogen-containing environments at industrial conditions associated with high-temperature hydrogen processing/production. This review summarises insights into the gaps in hydrogen embrittlement (HE) research that apply to high-temperature high-pressure systems in industrial processes and applications. It illustrates why it is still important to develop characterisation techniques and methods for hydrogen interaction with metals and surfaces under these conditions. The review also describes the implications of using hydrogen in large-scale industrial processes.

Liquid organic hydrogen carriers (LOHCs) are considered a promising hydrogen storage technology. Heat must be exchanged with an external medium such as a heat transfer fluid for the required chemical reactions to occur. Batch reactors are simple but useful solutions for small-scale storage applications which can be modelled with a lumped parameter approach adequately reproducing their dynamic performance. For such reactors power is consumed to circulate the external heat transfer fluid and stir the organic liquid inside the reactor and heat transfer performance and power consumption are two key parameters in reactor optimisation. Therefore with reference to the hydrogen release phase this paper describes a procedure to optimise the reactor thermal design based on a lumped-parameter model in terms of heat transfer performance and minimum power consumption. Two batch reactors are analysed: a conventional jacketed reactor with agitation nozzles and a half-pipe coil reactor. Heat transfer performance is evaluated by introducing a newly defined dimensionless parameter the Heat Transfer Ratio (HTR) whose value directly correlates to the heat rate required by the carrier's dehydrogenation reaction. The resulting model is a valid tool for adequately reproducing the hydrogen storage behaviour within dynamic models of complex and detailed energy systems.

To achieve the shift to renewable energies efficient energy storage is of the upmost importance. Hydrogen as a chemical energy storage represents a promising technology due to its high gravimetric energy density. However the most efficient form of hydrogen storage still remains an open question. Absorption-based storage of hydrogen in metal hydrides offers high volumetric energy densities as well as safety advantages. In this work technical economic and environmental aspects of different metal hydride materials are investigated. An overview of the material properties production methods as well as possibilities for enhancement of properties are presented. Furthermore impacts on material costs abundance of raw materials and dependency on imports are discussed. Advantages and disadvantages of selected materials are derived and may serve as a decision basis for material selection based on application. Further research on enhancement of material properties as well as on the system level is required for widespread application of metal hydrides.

Hydrogen storage might be key to the success of the hydrogen economy and hence the energy transition in Germany. One option for cost-effective storage of large quantities of hydrogen is the geological subsurface. However previous experience with underground hydrogen storage is restricted to salt caverns which are limited in size and space. In contrast pore storage facilities in aquifers -and/or depleted hydrocarbon reservoirs- could play a vital role in meeting base load needs due to their wide availability and large storage capacity but experiences are limited to past operations with hydrogen-bearing town gas. To overcome this barrier here we investigate hydrogen storage in porous storage systems in a two-step process: 1) First we investigate positive and cautionary indicators for safe operations of hydrogen storage in pore storage systems. 2) Second we estimate hydrogen storage capacities of pore storage systems in (current and decommissioned) underground natural gas storage systems and saline aquifers. Our systematic review highlights that optimal storage conditions in terms of energy content and hydrogen quality are found in sandstone reservoirs in absence of carbonate and iron bearing accessory minerals at a depth of approx. 1100 m and a temperature of at least 40°C. Porosity and permeability of the reservoir formation should be at least 20% and 5 × 10−13 m2 (~500 mD) respectively. In addition the pH of the brine should fall below 6 and the salinity should exceed 100 mg/L. Based on these estimates the total hydrogen storage capacity in underground natural gas storages is estimated to be up to 8 billion cubic meters or (0.72 Mt at STP) corresponding to 29 TWh of energy equivalent of hydrogen. Saline aquifers may offer additional storage capacities of 81.6–691.8 Mt of hydrogen which amounts to 3.2 to 27.3 PWh of energy equivalent of hydrogen the majority of which is located in the North German basin. Pore storage systems could therefore become a crucial element of the future German hydrogen infrastructure especially in regions with large industrial hydrogen (storage) demand and likely hydrogen imports via pipelines and ships.

To meet the global climate goals agreed upon regarding the Paris Agreement governments and institutions around the world are investigating various technologies to reduce carbon emissions and achieve a net-negative energy system. To this end integrated solutions that incorporate carbon utilization processes as well as promote the transition of the fossil fuel-based energy system to carbon-free systems such as the hydrogen economy are required. One of the possible pathways is to utilize CO2 as the base chemical for producing a liquid organic hydrogen carrier (LOHC) using CO2 as a mediating chemical for delivering H2 to the site of usage since gaseous and liquid H2 retain transportation and storage problems. Formic acid is a probable candidate considering its high volumetric H2 capacity and low toxicity. While previous studies have shown that formic acid is less competitive as an LOHC candidate compared to other chemicals such as methanol or toluene the results were based on out-of-date process schemes. Recently advances have been made in the formic acid production and dehydrogenation processes and an analysis regarding the recent process configurations could deem formic acid as a feasible option for LOHC. In this study the potential for using formic acid as an LOHC is evaluated with respect to the state-of-the-art formic acid production schemes including the use of heterogeneous catalysts during thermocatalytic and electrochemical formic acid production from CO2 . Assuming a hydrogen distribution system using formic acid as the LOHC each of the production transportation dehydrogenation and CO2 recycle sections are separately modeled and evaluated by means of techno-economic analysis (TEA) and life cycle assessment (LCA). Realistic scenarios for hydrogen distribution are established considering the different transportation and CO2 recovery options; then the separate scenarios are compared to the results of a liquefied hydrogen distribution scenario. TEA results showed that while the LOHC system incorporating the thermocatalytic CO2 hydrogenation to formic acid is more expensive than liquefied H2 distribution the electrochemical CO2 reduction to formic acid system reduces the H2 distribution cost by 12%. Breakdown of the cost compositions revealed that reduction of steam usage for thermocatalytic processes in the future can make the LOHC system based on thermocatalytic CO2 hydrogenation to formic acid to be competitive with liquefied H2 distribution if the production cost could be reduced by 23% and 32% according to the dehydrogenation mode selected. Using formic acid as a LOHC was shown to be less competitive compared to liquefied H2 delivery in terms of LCA but producing formic acid via electrochemical CO2 reduction was shown to retain the lowest global warming potential among the considered options.

This report evaluates the main options to provide required hydrogen storage capacity including the relevant system-level considerations and provides recommendations for further actions including low-regrets actions that are needed in a range of scenarios.

Energy storage is an effective way to address the instability of renewable energy generation modes such as wind and solar which are projected to play an important role in the sustainable and low-carbon society. Economics and carbon emissions are important indicators that should be thoroughly considered for evaluating the feasibility of energy storage technologies (ESTs). In this study we study two promising routes for large-scale renewable energy storage electrochemical energy storage (EES) and hydrogen energy storage (HES) via technical analysis of the ESTs. The levelized cost of storage (LCOS) carbon emissions and uncertainty assessments for EESs and HESs over the life cycle are conducted with full consideration of the critical links for these routes. In order to reduce the evaluation error we use the Monte Carlo method to derive a large number of data for estimating the economy and carbon emission level of ESTs based on the collected data. The results show that lithium ion (Li-ion) batteries show the lowest LCOS and carbon emissions at 0.314 US$ kWh-1 and 72.76 gCO2e kWh-1 compared with other batteries for EES. Different HES routes meaning different combinations of hydrogen production delivery and refueling methods show substantial differences in economics and the lowest LCOS and carbon emissions at 0.227 US$ kWh-1 and 61.63 gCO2e kWh-1 are achieved using HES routes that involve hydrogen production by alkaline electrolyzer (AE) delivery by hydrogen pipeline and corresponding refueling. The findings of this study suggest that HES and EES have comparable levels of economics and carbon emissions that should be both considered for large-scale renewable energy storage to achieve future decarbonization goals.

Soil corrosion and hydrogen embrittlement are the main factors of hydrogen pipeline failure. The gas escapes diffuses and accumulating in the soil and entering the atmosphere when leak occurs. The mechanism of gas diffusion in buried pipelines is very complicated. Mastering the evolution law of hydrogen leakage diffusion is conducive to quickly locating the leakage point and reducing the loss. The leakage model of the underground hydrogen pipeline is established in this paper. Effect of leakage hole soil type pipeline pressure pipeline diameter on hydrogen leakage diffusion were investigated. The results show that when the hydrogen pipeline leaks the hydrogen concentration increases with the increase of leakage time showing a symmetrical distribution trend. With the pipeline pressure increase hydrogen leakage speed is accelerated and longitudinal diffusion gradually becomes the dominant direction. With the leakage diameter increases hydrogen leakage per unit of time increases sharply. Hydrogen diffuses more easily in sandy soil and diffusion speed concentration and range are higher than that in clay soil. The research content provides a reference and basis for the detection and evaluation of buried hydrogen pipeline leakage.

To cope with climate change emerging fuels- hydrogen ammonia and methanol- have been proposed as promising energy carriers that will replace part of the liquefied natural gas (LNG) in future maritime scenarios. Energy efficiency is an important indicator for evaluating the system but the maritime supply system for emerging fuels has yet to be revealed. In this study the energy efficiency of the maritime supply chain of hydrogen ammonia methanol and natural gas is investigated considering processes including production storage loading transport and unloading. A sensitivity analysis of parameters such as ambient temperature storage time pipeline length and sailing time is also carried out. The results show that hydrogen (2.366%) has the highest daily boil-off gas (BOG) rate and wastes more energy than LNG (0.413%) with ammonia and methanol both being lower than LNG. The recycling of BOG is of great importance to the hydrogen supply chain. When produced from renewable energy sources methanol (98.02%) is the most energy efficient followed by ammonia with hydrogen being the least (89.10%). This assessment shows from an energy efficiency perspective that ammonia and methanol have the potential to replace LNG as the energy carrier of the future and that hydrogen requires efficient BOG handling systems to increase competitiveness. This study provides some inspirations for the design of global maritime supply systems for emerging fuels.

Hydrogen is being included in several decarbonization strategies as a potential contributor in some hard-to-abate applications. Among other challenges hydrogen storage represents a critical aspect to be addressed either for stationary storage or for transporting hydrogen over long distances. Ammonia is being proposed as a potential solution for hydrogen storage as it allows storing hydrogen as a liquid chemical component at mild conditions. Nevertheless the use of ammonia instead of pure hydrogen faces some challenges including the health and environmental issues of handling ammonia and the competition with other markets such as the fertilizer market. In addition the technical and economic efficiency of single steps such as ammonia production by means of the Haber–Bosch process ammonia distribution and storage and possibly the ammonia cracking process to hydrogen affects the overall supply chain. The main purpose of this review paper is to shed light on the main aspects related to the use of ammonia as a hydrogen energy carrier discussing technical economic and environmental perspectives with the aim of supporting the international debate on the potential role of ammonia in supporting the development of hydrogen pathways. The analysis also compares ammonia with alternative solutions for the long-distance transport of hydrogen including liquefied hydrogen and other liquid organic carriers such as methanol.