Publications

The growing need for hydrogen indicates that there is likely to be a demand for transporting hydrogen. Hydrogen pipelines are an economical option but the issue of hydrogen damage to pipeline steels needs to be studied and investigated. So far limited research has been dedicated to determining how the choice of inspection method for pipeline integrity management changes depending on the presence of a coating. Thus this review aims to evaluate the effectiveness of inspection methods specifically for detecting the defects formed uniquely in coated hydrogen pipelines. The discussion will begin with a background of hydrogen pipelines and the common defects seen in these pipelines. This will also include topics such as blended hydrogen-natural gas pipelines. After which the focus will shift to pipeline integrity management methods and the effectiveness of current inspection methods in the context of standards such as ASME B31.12 and BS 7910. The discussion will conclude with a summary of newly available inspection methods and future research directions.

The regional parliament of Tyrol in Austria adopted the climate energy and resources strategy “Tyrol 2050 energy autonomous” in 2014 with the aim to become climate neutral and energy autonomous. “Use of own resources before others do or have to do” is the main principle within this long-term strategic approach in which the “power on demand” process is a main building block and the “power-to-hydrogen” process covers the intrinsic lack of a long-term large-scale storage of electricity. Within this long-term strategy the national research and development (R&D) flagship project WIVA P&G HyWest (ongoing since 2018) aims at the establishment of the first sustainable business-case-driven regional green hydrogen economy in central Europe. This project is mainly based on the logistic principle and is a result of synergies between three ongoing complementary implementation projects. Among these three projects to date the industrial research within “MPREIS Hydrogen” resulted in the first green hydrogen economy. One hydrogen truck is operational as of January 2023 in the region of Tyrol for food distribution and related monitoring studies have been initiated. To fulfil the logistic principle as the main outcome another two complementary projects are currently being further implemented.

Due to having zero carbon emissions and renewable advantages hydrogen has great prospects as a renewable form of alternate energy. Engine load and hydrogen substitution rate have a considerable influence on a hydrogen–diesel dual-fuel engine’s efficiency. This experiment’s objective is to study the influence of hydrogen substitution rate on engine combustion and emission under different loads and to study the impact of exhaust gas recirculation (EGR) technology or main injection timing on the engine’s capability under high load and high hydrogen substitution rate. The range of the maximum hydrogen substitution rate was determined under different loads (30%~90%) at 1800 rpm and then the effects of the EGR rate (0%~15%) and main injection timing (−8 ◦CA ATDC~0 ◦CA ATDC) on the engine performance under 90% high load were studied. The research results show that the larger the load the smaller the maximum hydrogen substitution rate that can be added to the dual-fuel engine. Under each load with the increase of the hydrogen substitution rate the cylinder pressure and the peak heat release rate (HRR) increase the equivalent brake-specific fuel consumption (BSFCequ) decreases the thermal efficiency increases the maximum thermal efficiency is 43.1% the carbon dioxide (CO2 ) emission is effectively reduced by 35.2% and the nitrogen oxide (NOx) emission decreases at medium and low loads and the maximum increase rate is 20.1% at 90% load. Under high load with the increase of EGR rate or the delay of main injection timing the problem of NOx emission increases after hydrogen doping can be effectively solved. As the EGR rate rises from 0% to 15% the maximum reduction of NOx is 63.1% and with the delay of main injection timing from −8 ◦CA ATDC to 0 ◦CA ATDC the maximum reduction of NOx is 44.5%.

Of all the alternatives to hydrocarbon fuels hydrogen offers the greatest long-term potential to radically reduce the many problems inherent in fuel used for transportation. Hydrogen vehicles have zero tailpipe emissions and are very efficient. If the hydrogen is made from renewable sources such as nuclear power or fossil sources with carbon emissions captured and sequestered hydrogen use on a global scale would produce almost zero greenhouse gas emissions and greatly reduce air pollutant emissions. The aim of this work is to realise a traceability chain for hydrogen flow metering in the range typical for fuelling applications in a wide pressure range with pressures up to 875 bar (for Hydrogen Refuelling Station - HRS with Nominal Working Pressure of 700 bar) and temperature changes from −40 °C (pre-cooling) to 85 °C (maximum allowed vehicle tank temperature) in accordance with the worldwide accepted standard SAE J2601. Several HRS have been tested in Europe (France Netherlands and Germany) and the results show a good repeatability for all tests. This demonstrates that the testing equipment works well in real conditions. Depending on the installation configuration some systematic errors have been detected and explained. Errors observed for Configuration 1 stations can be explained by pressure differences at the beginning and end of fueling in the piping between the Coriolis Flow Meter (CFM) and the dispenser: the longer the distance the bigger the errors. For Configuration 2 where this distance is very short the error is negligible.

The development of a Clean Hydrogen Standard based on life-cycle greenhouse gas (GHG) emissions is gaining prominence on the international agenda. Thus a framework for assessing life-cycle GHG emissions for clean hydrogen pathways is necessary. In this study the comprehensive datasets and effects of various scenarios encompassing hydrogen production carriers (liquid hydrogen ammonia methylcyclohexane) carbon capture and storage (CCS) target analysis year (2021 2030) to reflect trends of greening grid electricity and potential import countries on aggregated life-cycle GHG emissions were presented. South Korea was chosen as a case study region and the low-carbon alternatives were suggested for reducing aggregated emissions to meet the Korean standard (5 kgCO2e/kgH2). First capturing and storing nearly entire (>90%) CO2 from fossil- and waste-based production pathways is deemed essential. Second when repurposing the use of hydrogen that was otherwise used internally applying a penalty for substitution is appropriate leading to results notably exceeding the standard. Third for electrolysis-based hydrogen using renewable or nuclear electricity is essential. Lastly when hydrogen is imported in a well-to-point-of-delivery (WtP) perspective using renewable electricity during hydrogen conversion into a carrier and reusing the produced hydrogen for endothermic reconversion reaction are recommended. By implementing the developed calculation framework to other countries' cases it was observed that importing hydrogen to regions having scope of WtP or above (e.g. well-to-wheel) might not meet the threshold due to additional emissions from importation processes. Additionally for hydrogen carriers undergoing the endothermic reconversion the approach to reduce WtP emissions (reusing produced hydrogen) may conflict with the approach to reduce well-to-gate (WtG) emission (using external fossilbased fuel). The discrepancy highlights the need to set a broader scope of emissions assessment to effectively promote the life-cycle emission reduction efforts of hydrogen importers. This study contributes to the field of clean hydrogen GHG emission assessment offering a robust database and calculation framework while addressing the effects of greening grid electricity and CCS implementation proposing low-carbon alternatives and GHG assessment scope to achieve global GHG reduction.

Accurate evaluation of thermo‑fluid dynamic characteristics in tanks is critically important for designing liquid hydrogen tanks for small‑scale hydrogen liquefiers to minimize heat leakage into the liquid and ullage. Due to the high costs most future liquid hydrogen storage tank designs will have to rely on predictive computational models for minimizing pressurization and heat leakage. Therefore in this study to improve the storage efficiency of a small‑scale hydrogen liquefier a three‑ dimensional CFD model that can predict the boil‑off rate and the thermo‑fluid characteristics due to heat penetration has been developed. The prediction performance and accuracy of the CFD model was validated based on comparisons between its results and previous experimental data and a good agreement was obtained. To evaluate the insulation performance of polyurethane foam with three different insulation thicknesses the pressure changes and thermo‑fluid characteristics in a partially liquid hydrogen tank subject to fixed ambient temperature and wind velocity were investigated nu‑ merically. It was confirmed that the numerical simulation results well describe not only the temporal variations in the thermal gradient due to coupling between the buoyance and convection but also the buoyancy‑driven turbulent flow characteristics inside liquid hydrogen storage tanks with differ‑ ent insulation thicknesses. In the future the numerical model developed in this study will be used for optimizing the insulation systems of storage tanks for small‑scale hydrogen liquefiers which is a cost‑effective and highly efficient approach.

With the unprecedented development of green and renewable energy sources the proportion of clean hydrogen (H2 ) applications grows rapidly. Since H2 has physicochemical properties of being highly permeable and combustible high-performance H2 sensors to detect and monitor hydrogen concentration are essential. This review discusses a variety of fiber-optic-based H2 sensor technologies since the year 1984 including: interferometer technology fiber grating technology surface plasma resonance (SPR) technology micro lens technology evanescent field technology integrated optical waveguide technology direct transmission/reflection detection technology etc. These technologies have been evolving from simply pursuing high sensitivity and low detection limits (LDL) to focusing on multiple performance parameters to match various application demands such as: high temperature resistance fast response speed fast recovery speed large concentration range low cross sensitivity excellent long-term stability etc. On the basis of palladium (Pd)-sensitive material alloy metals catalysts or nanoparticles are proposed to improve the performance of fiberoptic-based H2 sensors including gold (Au) silver (Ag) platinum (Pt) zinc oxide (ZnO) titanium oxide (TiO2 ) tungsten oxide (WO3 ) Mg70Ti30 polydimethylsiloxane (PDMS) graphene oxide (GO) etc. Various microstructure processes of the side and end of optical fiber H2 sensors are also discussed in this review.

This paper focuses on the potential use of ammonia as a carbon-free fuel and covers recent advances in the development of ammonia combustion technology and its underlying chemistry. Fulfilling the COP21 Paris Agreement requires the de-carbonization of energy generation through utilization of carbon-neutral and overall carbon-free fuels produced from renewable sources. Hydrogen is one of such fuels which is a potential energy carrier for reducing greenhouse-gas emissions. However its shipment for long distances and storage for long times present challenges. Ammonia on the other hand comprises 17.8% of hydrogen by mass and can be produced from renewable hydrogen and nitrogen separated from air. Furthermore thermal properties of ammonia are similar to those of propane in terms of boiling temperature and condensation pressure making it attractive as a hydrogen and energy carrier. Ammonia has been produced and utilized for the past 100 years as a fertilizer chemical raw material and refrigerant. Ammonia can be used as a fuel but there are several challenges in ammonia combustion such as low flammability high NOx emission and low radiation intensity. Overcoming these challenges requires further research into ammonia flame dynamics and chemistry. This paper discusses recent successful applications of ammonia fuel in gas turbines co-fired with pulverize coal and in industrial furnaces. These applications have been implemented under the Japanese ‘Cross-ministerial Strategic Innovation Promotion Program (SIP): Energy Carriers’. In addition fundamental aspects of ammonia combustion are discussed including characteristics of laminar premixed flames counterflow twin-flames and turbulent premixed flames stabilized by a nozzle burner at high pressure. Furthermore this paper discusses details of the chemistry of ammonia combustion related to NOx production processes for reducing NOx and validation of several ammonia oxidation kinetics models. Finally LES results for a gas-turbine-like swirl-burner are presented for the purpose of developing low-NOx single-fuelled ammonia gas turbine combustors.

To reach climate neutrality by 2050 a goal that the European Union set itself it is necessary to change and modify the whole EU’s energy system through deep decarbonization and reduction of greenhouse-gas emissions. The study presents a current insight into the global energy-transition pathway based on the hydrogen energy industry chain. The paper provides a critical analysis of the role of clean hydrogen based on renewable energy sources (green hydrogen) and fossil-fuels-based hydrogen (blue hydrogen) in the development of a new hydrogen-based economy and the reduction of greenhouse-gas emissions. The actual status costs future directions and recommendations for low-carbon hydrogen development and commercial deployment are addressed. Additionally the integration of hydrogen production with CCUS technologies is presented.

Hydrogen as a clean energy carrier is of great potential to be an alternative fuel in the future. Proton exchange membrane (PEM) water electrolysis is hailed as the most desired technology for high purity hydrogen production and self-consistent with volatility of renewable energies has ignited much attention in the past decades based on the high current density greater energy efficiency small mass-volume characteristic easy handling and maintenance. To date substantial efforts have been devoted to the development of advanced electrocatalysts to improve electrolytic efficiency and reduce the cost of PEM electrolyser. In this review we firstly compare the alkaline water electrolysis (AWE) solid oxide electrolysis (SOE) and PEM water electrolysis and highlight the advantages of PEM water electrolysis. Furthermore we summarize the recent progress in PEM water electrolysis including hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts in the acidic electrolyte. We also introduce other PEM cell components (including membrane electrode assembly current collector and bipolar plate). Finally the current challenges and an outlook for the future development of PEM water electrolysis technology for application in future hydrogen production are provided.