Norway

Replacing fossil fuels with energy sources and carriers that are sustainable environmentally benign and affordable is amongst the most pressing challenges for future socio-economic development. To that goal hydrogen is presumed to be the most promising energy carrier. Electrocatalytic water splitting if driven by green electricity would provide hydrogen with minimal CO2 footprint. The viability of water electrolysis still hinges on the availability of durable earth-abundant electrocatalyst materials and the overall process efficiency. This review spans from the fundamentals of electrocatalytically initiated water splitting to the very latest scientific findings from university and institutional research also covering specifications and special features of the current industrial processes and those processes currently being tested in large-scale applications. Recently developed strategies are described for the optimisation and discovery of active and durable materials for electrodes that ever-increasingly harness first principles calculations and machine learning. In addition a technoeconomic analysis of water electrolysis is included that allows an assessment of the extent to which a large-scale implementation of water splitting can help to combat climate change. This review article is intended to cross-pollinate and strengthen efforts from fundamental understanding to technical implementation and to improve the ‘junctions’ between the field’s physical chemists materials scientists and engineers as well as stimulate much-needed exchange among these groups on challenges encountered in the different domains.

Ammonia is an industrial chemical and the basic building block for the fertilizer industry. Lately attention has shifted towards using ammonia as a carbon-free energy vector due to the ease of transportation and storage in liquid state at − 33 ◦C and atmospheric pressure. This study evaluates the prospects of blue and green ammonia as future energy carriers; specifically the gas switching reforming (GSR) concept for H2 and N2 co-production from natural gas with inherent CO2 capture (blue) and H2 generation through an optimized value chain of wind and solar power electrolysers cryogenic N2 supply and various options for energy storage (green). These longer term concepts are benchmarked against conventional technologies integrating CO2 capture: the Kellogg Braun & Root (KBR) Purifier process and the Linde Ammonia Concept (LAC). All modelled plants utilize the same ammonia synthesis loop for a consistent comparison. A cash flow analysis showed that the GSR concept achieved an attractive levelized cost of ammonia (LCOA) of 332.1 €/ton relative to 385.1–385.9 €/ton for the conventional plants at European energy prices (6.5 €/GJ natural gas and 60 €/MWh electricity). Optimal technology integration for green ammonia using technology costs representative of 2050 was considerably more expensive: 484.7–772.1 €/ton when varying the location from Saudi Arabia to Germany. Furthermore the LCOA of the GSR technology drops to 192.7 €/ton when benefitting from low Saudi Arabian energy costs (2 €/GJ natural gas and 40 €/MWh electricity). This cost difference between green and blue ammonia remained robust in sensitivity analyses where input energy cost (natural gas or wind/solar power) was the most influential parameter. Given its low production costs and the techno-economic feasibility of international ammonia trade advanced blue ammonia production from GSR offers an attractive pathway for natural gas exporting regions to contribute to global decarbonization.

Hydrogen as a carbon-free energy carrier has emerged as a crucial component in the decarbonization of the energy system serving as both an energy storage option and fuel for dispatchable power generation to mitigate the intermittent nature of renewable energy sources. However the unique physical and combustion characteristics of hydrogen which differ from conventional gaseous fuels such as biogas and natural gas present new challenges that must be addressed. To fully integrate hydrogen as an energy carrier in the energy system the development of low-emission and highly reliable technologies capable of handling hydrogen combustion is imperative. This study presents a ground-breaking achievement - the first successful test of a micro gas turbine running on 100% hydrogen with NOx emissions below the standard limits. Furthermore the combustor of the micro gas turbine demonstrates exceptional fuel flexibility allowing for the use of various blends of hydrogen biogas and natural gas covering a wide range of heating values. In addition to a comprehensive presentation of the test rig and its instrumentation this paper illuminates the challenges of hydrogen combustion and offers real-world operational data from engine operation with 100% hydrogen and its blends with methane.

The hydrogen economy is receiving increasing attention as a complement to electrification in the global energy transition. Clean hydrogen production is often viewed as a competition between natural gas reforming with CO2 capture and electrolysis using renewable electricity. However solid fuel gasification with CO2 capture presents another viable alternative especially when considering the potential of biomass to achieve negative CO2 emissions. This study investigates the techno-economic potential of hydrogen production from large-scale coal/ biomass co-gasification plants with CO2 capture. With a CO2 price of 50 €/ton the benchmark plant using commercially available technologies achieved an attractive hydrogen production cost of 1.78 €/kg with higher CO2 prices leading to considerable cost reductions. Advanced configurations employing hot gas clean-up membrane-assisted water-gas shift and more efficient gasification with slurry vaporization and a chemical quench reduced the hydrogen production cost to 1.50–1.62 €/kg with up to 100% CO2 capture. Without contingencies added to the pre-commercial technologies the lowest cost reduces to 1.43 €/kg. It was also possible to recover waste heat in the form of hot water at 120 ◦C for district heating potentially unlocking further cost reductions to 1.24 €/kg. In conclusion gasification of locally available solid fuels should be seriously considered next to natural gas and electrolysis for supplying the emerging hydrogen economy.

With the long-standing efforts of green transition in our society underground hydrogen storage (UHS) has emerged as a viable solution to buffering seasonal fluctuations of renewable energy supplies and demands. Like operations in hydrocarbon production and geological CO2 storage a successful UHS project requires a good understanding of subsurface formations while having different operational objectives and practical challenges. Similar to the situations in hydrocarbon production and geological CO2 storage in UHS problems the information of subsurface formations at the field level cannot be obtained through direct measurements due to the resulting high costs. As such there is a need for subsurface characterization and monitoring at the field scale which uses a certain history matching algorithm to calibrate a numerical subsurface model based on available field data. Whereas subsurface characterization and monitoring have been widely used in hydrocarbon production activities for a better understanding of hydrocarbon reservoirs to the best of our knowledge at present it appears to be a relatively less touched area in UHS problems. This work aims to narrow this noticed gap and investigates the use of an ensemble-based workflow for subsurface characterization and monitoring in a 3D UHS case study. Numerical results in this case study indicate that the ensemble-based workflow works reasonably well while also identifying some particular challenges that would be relevant to real-world problems.

This review explores recent advancements in hydrogen gas (H2 ) safety through the lens of artificial intelligence (AI) techniques. As hydrogen gains prominence as a clean energy source ensuring its safe handling becomes paramount. The paper critically evaluates the implementation of AI methodologies including artificial neural networks (ANN) machine learning algorithms computer vision (CV) and data fusion techniques in enhancing hydrogen safety measures. By examining the integration of wireless sensor networks and AI for real-time monitoring and leveraging CV for interpreting visual indicators related to hydrogen leakage issues this review highlights the transformative potential of AI in revolutionizing safety frameworks. Moreover it addresses key challenges such as the scarcity of standardized datasets the optimization of AI models for diverse environmental conditions etc. while also identifying opportunities for further research and development. This review foresees faster response times reduced false alarms and overall improved safety for hydrogen-related applications. This paper serves as a valuable resource for researchers engineers and practitioners seeking to leverage state-of-the-art AI technologies for enhanced hydrogen safety systems.

The cost of green hydrogen production is very dependent on the price of electricity. A control system that can schedule hydrogen production based on forecast wind speed and electricity price should therefore be advantageous for large-scale wind-hydrogen systems. This work presents a novel price-based control system integrated in a techno-economic analysis of hydrogen production from offshore wind. A polynomial regression model that predicts wind power production from wind speed input was developed and tested with real-world datasets from a 2.3 MW floating offshore wind turbine. This was combined with a mathematical model of a PEM electrolyzer and used to simulate hydrogen production. A novel price-based control system was developed to decide when the system should produce hydrogen and when it should sell electricity to the grid. The model and control system can be used in real-world wind-hydrogen systems and require only the forecast wind speed electricity price and selling price of hydrogen as inputs. 11 test scenarios based on 10 years of real-world wind speed and electricity price data are proposed and used to evaluate the effect the price-based control system has on the levelized cost of hydrogen (LCOH). Both current and future (2050) costs and technologies are used and the results show that the novel control system lowered the LCOH in all scenarios by 10–46%. The lowest LCOH achieved with current technology and costs was 6.04 $/kg H2. Using the most optimistic forecasts for technology improvements and cost reductions in 2050 the model estimated a LCOH of 0.96 $/kg H2 for a grid-connected offshore wind farm and onshore hydrogen production 0.82 $/kg H2 using grid electricity (onshore) and 4.96 $/kg H2 with an offgrid offshore wind-hydrogen system. When the electricity price from the period 2013–2022 was used on the 2050 scenarios the resulting LCOH was approximately twice as high.

Long-term and large-scale H2 storage is vital for a sustainable H2 economy. Research in underground H2 storage (UHS) in porous media is emerging but the understanding of H2 reconnection and recovery mechanisms under cyclic loading is not yet adequate. This paper reports a qualitative and quantitative investigation of H2 reconnection and recovery mechanisms in repeated injection-withdrawal cycles. Here we use microfluidics to experimentally investigate up to 5 cycles of H2 injection and withdrawal under a range of injection rates at shallow reservoir storage conditions. We find that H2 storage capacities increase with increasing injection rate and range between ~10% and 60%. The residual H2 saturation is in the same range between cycles (30e40%) but its distribution in the pore space visually appears to be hysteretic. In most cases the residually trapped H2 reconnects in the subsequent injection cycle predominantly in proximity to the large pore clusters. Our results provide valuable experimental data to advance the understanding of multiple H2 injection cycles in UHS schemes.

Hydrogen will be important in decarbonized energy systems. The primary ways to produce low emission hydrogen are from renewable electricity using electrolyzers called green hydrogen and by reforming natural gas and capturing and storing the CO2 known as blue hydrogen. In this study the degrees to which blue and green hydrogen are complementary or competitive are analyzed through a sensitivity analysis on the electrolyzer costs and natural gas price. This analysis is performed on four bases: what is the cost-effective relative share between blue and green hydrogen deployment how their deployment influences the price of hydrogen how the price of CO2 changes with the deployment of these two technologies and whether infrastructure can economically be shared between these two technologies. The results show that the choice of green and blue hydrogen has a tremendous impact where an early deployment of green leads to higher hydrogen costs and CO2 prices in 2030. Allowing for blue hydrogen thus has notable benefits in 2030 giving cheaper hydrogen with smaller wider socioeconomic impacts. In the long term these competitive aspects disappear and green and blue hydrogen can coexist in the European market without negatively influencing one another.

The large-scale deployment of technologies that enable energy from renewables is essential for a successful transition to a carbon-neutral future. While photovoltaic panels are one of the main technologies commonly used for harvesting energy from the Sun storage of renewable solar energy still presents some challenges and often requires integration with additional devices. It is believed that hydrogen – being a perfect energy carrier – can become one of the broadly utilised storage alternatives that would effectively mitigate the energy supply and demand issues associated with the intermittent nature of renewable energy sources. Current pathways in the development of green technologies indicate the need for more sustainable material utilisation and more efficient device operation. To address this requirement integration of various technologies for renewable energy harvesting conversion and storage in a single device appears as an advantageous option. From the hydrogen economy perspective systems driven by green solar electricity that allow for (photo)electrochemical water splitting would generate hydrogen with the minimal CO2 footprint. If at the same time one of the device electrodes could store the generated gas and release it on demand the utilisation of critical and often costly elements would be reduced with possible gain in more effective device operation. Although conceptually attractive this cross-disciplinary concept has not gained yet enough attention and only limited number of experimental setups have been designed tested and reported. This review presents the first exhaustive overview and critical examination of various laboratory-scale prototype setups that attempt to combine both the hydrogen production and storage processes in a single unit via integration of a metal hydride-based electrode into a photoelectrochemical cell. The architectures of presented configurations enables direct solar energy to hydrogen conversion and its subsequent storage in a single device which – in some cases – can also release the stored (hydrogen) energy on demand. In addition this work explores perspectives and challenges related with the potential upscaling of reviewed solar-to-hydrogen storage systems trying to map and indicate the main future directions of their technological development and optimization. Finally the review also combines information and expertise scattered among various research fields with the aim of stimulating much-needed exchange of knowledge to accelerate the progress in the development and deployment of optimum green hydrogen-based solutions.