Publications

Recently worldwide the attention being paid to hydrogen and its derivatives as alternative carbon-free (or low-carbon) options for the electricity sector the transport sector and the industry sector has increased. Several projects in the field of low-emission hydrogen production (particularly electrolysis-based green hydrogen) have either been constructed or analyzed for their feasibility. Despite the great ambitions announced by some nations with respect to becoming hubs for hydrogen production and export some quantification of the levels at which hydrogen and its derived products are expected to penetrate the global energy system and its various demand sectors would be useful in order to judge the practicality and likelihood of these ambitions and future targets. The current study aims to summarize some of the expectations of the level at which hydrogen and its derivatives could spread into the global economy under two possible future scenarios. The first future scenario corresponds to a business-as-usual (BAU) pathway where the world proceeds with the same existing policies and targets related to emissions and low-carbon energy transition. This forms a lower bound for the level of the role of hydrogen and its penetration into the global energy system. The second future scenario corresponds to an emission-conscious pathway where governments cooperate to implement the changes necessary to decarbonize the economy by 2050 in order to achieve net-zero emissions of carbon dioxide (carbon neutrality) and thus limit the rise in the global mean surface temperature to 1.5 ◦C by 2100 (compared to pre-industrial periods). This forms an upper bound for the level of the role of hydrogen and its penetration into the global energy system. The study utilizes the latest release of the annual comprehensive report WEO (World Energy Outlook—edition year 2023 the 26th edition) of the IEA (International Energy Agency) as well as the latest release of the annual comprehensive report WETO (World Energy Transitions Outlook—edition year 2023 the third edition) of the IRENA (International Renewable Energy Agency). For the IEA-WEO report the business-as-usual situation is STEPS (Stated “Energy” Policies Scenario) and the emissions-conscious situation is NZE (Net-Zero Emissions by 2050). For the IRENA-WETO report the business-asusual situation is the PES (Planned Energy Scenario) and the emissions-conscious situation is the 1.5◦C scenario. Through the results presented here it becomes possible to infer a realistic range for the production and utilization of hydrogen and its derivatives in 2030 and 2050. In addition the study enables the divergence between the models used in WEO and WETO to be estimated by identifying the different predictions for similar variables under similar conditions. The study covers miscellaneous variables related to energy and emissions other than hydrogen which are helpful in establishing a good view of how the world may look in 2030 and 2050. Some barriers (such as the uncompetitive levelized cost of electrolysis-based green hydrogen) and drivers (such as the German H2Global initiative) for the hydrogen economy are also discussed. The study finds that the large-scale utilization of hydrogen or its derivatives as a source of energy is highly uncertain and it may be reached slowly given more than two decades to mature. Despite this electrolysis-based green hydrogen is expected to dominate the global hydrogen economy with the annual global production of electrolysis-based green hydrogen expected to increase from 0 million tonnes in 2021 to between 22 million tonnes and 327 million tonnes (with electrolyzer capacity exceeding 5 terawatts) in 2050 depending on the commitment of policymakers toward decarbonization and energy transitions.

This report lays out roadmaps for the nine technology families identified in the UK Hydrogen Innovation Opportunity. The content in these roadmaps has been developed through a combination of extensive industrial engagement and aggregation of existing sector and technology roadmaps. This document also signposts to reports that highlight innovation challenges and opportunities for two underpinning technology families - materials and digital. The technology roadmaps in this document each include the following:

♦ UK and global market forecast for 2030 and 2050 for the respective technology family.

♦ Key technologies that make up the technology family.

♦ The associated innovation opportunities associated with each key technology together with development and industrialisation timelines and the sectors that will benefit from the innovation.

The list of innovation opportunities on each roadmap is by no means exhaustive but they are a sample that were selected because they highlighted some key innovation actions for the UK. To make this selection a range of factors were considered including global and UK economic demand the UK political imperative and UK potential to win market share. The development and industrialisation timelines are recommendations only and do not signify that this work is already planned or funded.

This report can also be downloaded for free on the Hydrogen Innovation Initiative website.

The combustion and emission characteristics of a hydrogen engine were investigated through experimental analysis using a GDI engine. To enable hydrogen in-cylinder direct injection a specialized hydrogen gas injector was employed. A comparative analysis of the combustion performance between gasoline and hydrogen fuels in a spark-ignited engine was conducted. Additionally the study experimentally explored the thermal efficiency and emission reduction potential of hydrogen engines in lean combustion modes. The results indicated a significant improvement in the combustion rate when hydrogen fuel was utilized in the spark-ignited engine. However the effective thermal efficiency was found to be lower than that of gasoline fuel due to the delayed MBF50 under stoichiometric conditions. Furthermore when compared to gasoline fuel the reduction of CO and THC emissions was accompanied by an increase in NOx emissions. Nevertheless optimizing the air dilution ratio in hydrogen engines led to an improvement in the effective thermal efficiency. Specifically under medium load conditions a Lambda value of 2.7 resulted in an effective thermal efficiency of 43.5%. Additionally under ultra-lean conditions (Lambda > 2.3) NOx emissions could be reduced to below 50 ppm reaching as low as 44 ppm. This study highlights the potential of improving combustion efficiency and reducing emissions by utilizing hydrogen fuel particularly in lean combustion modes. It contributes to the continuous development of hydrogen engine technology and promotes the implementation of cleaner and more efficient energy solutions.

Converting renewable electricity via water electrolysis into green hydrogen and hydrogen-based products will shape a global trade in power-to-x (PtX) products. The European Union's renewable hydrogen import target of 10 million tonnes by 2030 reflects the urgent need for PtX imports by sea to early high-demand countries like Germany. This study evaluates the cost efficiency and greenhouse gas (GHG) emissions of four hydrogen carrier ship import options considering a reconversion to H2 at the import terminal for a final delivery to offtakers via a H2 pipeline network in 2030. This includes ammonia a liquid organic hydrogen carrier (LOHC) system based on benzyltoluene (BT) and a novel CO2/e-methane and CO2/e-methanol cycle where CO2 is captured at the reconversion plant and then shipped back to the PtX production site in a nearly closed carbon loop. The GHG emission accounting includes well-to-wake emissions of the marine fuels and direct emissions of the carbon capture plant. Two GW-scale case studies reveal the impact of a short and long-distance route from Tunisia and Australia to Germany whereas the specific PtX carriers are either fuelled by its PtX cargo as a renewable marine fuel or by conventional heavy fuel oil (HFO). Ammonia outperforms the other PtX routes as the total hydrogen supply cost range between 5.07 and 7.69 for Australia (low: NH3 HFO high: LOHC HFO) and 4.78–6.21 € per kg H2 for Tunisia (low: NH3 HFO high: CH4 HFO) respectively. The ammonia routes achieve thereby GHG intensities of 31 % and 86 % below the EU threshold of 3.4 kg CO2(e) per kg H2 for renewable hydrogen. LOHC though unless switching to low-emission fuels and the CO2/e-methanol cycle exceed the GHG threshold at shipping distances of 12300 and 16600 km. The hydrogen supply efficiencies vary between 57.9 and 78.8 %LHV (low: CH4 PtX-fuelled high: NH3 HFO) with a PtX marine fuel consumption of up to 15 % LHV for the Australian methanol route whereas high uncertainties remain for the ammonia and methanol reconversion plant efficiencies. The CO2 cyle enables a cost-efficient CO2 supply easing the near-term shortage of climate-neutral CO2 sources at the cost of high GHG emissions for long-distance routes.

Proton exchange membrane electrolytic cells (PEMECs) have the potential to provide green Hydrogen as a sustainable energy source. PEMEC has already been applied at an industrially relevant scale. However it still faces challenges regarding reliability and durability especially in long-term operation. This review emphasizes the need for standardizing the cell configuration the testing protocols and the evaluation procedures to attain the optimum operation settings and eventually precisely evaluating the degradation rate. Potential physicochemical and electrical operational health indicators are described to identify the degradation of a distinct cell component in a running PEMEC. The reliable evaluation of degradation rate via operational health indicators with a robust supervisory system under stringent operating conditions is likely to diagnose the degradation mechanism. By developing incremental empirical degradation models via mapping a correlation between the history of proposed operational health indicators the instantaneous degradation rate can be quantified. This approach in turn enables us to determine the state-of-operation of an electrolyzer during service thereby benchmarking the durability of PEMEC. Finally with the target of scaling up and fulfilling the commercial demands for PEMEC the significance and literature contributions regarding operation management and prog nostics are expressed.

Large-scale production of hydrogen using clean electricity from renewable energy sources (RESs) is gaining more momentum in attempts to foster the growth of the nascent hydrogen energy market. However the inherited intermittency of RESs constitutes a significant challenge for the reliable and economic operation of electrolysers and consequently the overall hydrogen production plant. This paper proposes a power allocation control strategy to regulate the operation of a multi-unit electrolyser plant fed by a solar power system for improved efficiency and economic hydrogen production. Proper implementation of the proposed control strategy can decrease the number of switching times increase hydrogen production raise the efficiency and extend the operational lifespan of the utilised electrolyser units. A solar-hydrogen system comprising a 1 MW electrolyser plant and a battery system is designed and implemented in MATLAB/Simulink environment to validate the efficacy of the proposed control strategy in improving the performance and reliability of an Industrial Green Hydrogen Hub (IGHH). The simulation results showed an improvement of 52.85% in the daily production of hydrogen with an increase of 71.088 kg/day a 68.67% improvement in the efficiency and an enhancement of more than 80% in the utilisation factor of the IGHH compared to other control techniques (traditional choppy control).

In the field of rail transit the UK Department of Transport stated that it will realize a comprehensive transformation of UK railways by 2050 abandoning traditional diesel trains and upgrading them to new environmentally friendly trains. The current mainstream upgrade methods are electrification and hydrogen fuel cells. Comprehensive upgrades are costly and choosing the optimal upgrade method for trams and mainline railways is critical. Without a sensitivity analysis it is difficult for us to determine the influence relationship between each parameter and cost resulting in a waste of cost when choosing a line reconstruction method. In addition by analyzing the sensitivity of different parameters to the cost the primary optimization direction can be determined to reduce the cost. Global higher-order sensitivity analysis enables quantification of parameter interactions showing non-additive effects between parameters. This paper selects the main parameters that affect the retrofit cost and analyzes the retrofit cost of the two upgrade methods in the case of trams and mainline railways through local and global sensitivity analysis methods. The results of the analysis show that given the current UK rail system it is more economical to choose electric trams and hydrogen mainline trains. For trams the speed at which the train travels has the greatest impact on the final cost. Through the sensitivity analysis this paper provides an effective data reference for the current railway upgrading and reconstruction plan and provides a theoretical basis for the next step of train parameter optimization.

Green hydrogen a critical element in the shift towards sustainable energy is traditionally produced by electrolysis powered by solar photovoltaic (PV) systems. This research explores the potential of underexploited photovoltaic thermal (PV-T) systems for efficient green hydrogen generation. This paper compares this advanced technology performance and economic viability against conventional PV setups. This paper uses TRNSYS simulation software to analyze two distinct solar-based hydrogen production configurations – PV and PV-T – across diverse climatic conditions in Doha Tunis and Stuttgart. The paper’s findings indicate that PV-T significantly outperforms PV in hydrogen generation across diverse climates (Doha Tunis Stuttgart). For instance in Doha PV-T systems increase hydrogen output by 78% in Tunis by 59% and in Stuttgart by 25%. An economic assessment reveals PV panels as the most cost-effective option with hydrogen production costs ranging from $4.92/kg to $9.66/kg across the studied locations. For PV-T collectors the hydrogen cost range from $6.66/kg to $16.80/kg across the studied locations. Nevertheless this research highlights the potential of PV-T technology to enhance the efficiency and economic viability of green hydrogen production. These findings offer valuable insights for policymakers investors and researchers pursuing more efficient solutions for sustainable energy.

Fermentation is an oxygen-free biological process that produces hydrogen a clean renewable energy source with the potential to power a low-carbon economy. Bibliometric analysis is crucial in academic research to evaluate scientific production identify trends and contributors and map the development of a field providing valuable information to guide researchers and promote scientific innovation. This review provides an advanced bibliometric analysis and a future perspective on fermentation for hydrogen production. By searching WoS we evaluated and refined 62087 articles to 4493 articles. This allowed us to identify the most important journals countries institutions and authors in the field. In addition the ten most cited articles and the dominant research areas were identified. A keyword analysis revealed five research clusters that illustrate where research is progressing. The outlook indicates that a deeper understanding of microbiology and support from energy policy will drive the development of hydrogen from fermentation.

Hydrogen energy is a cornerstone of the future climate-neutral economy. Yet as undetected leaks easily generate dangerous atmospheres sensing systems must timely detect accumulated hydrogen to prevent ignitions and explosions. Eye-readable sensors (ERSs) displaying intuitive readouts promise to guarantee safe use and universal access to hydrogen-based technology. This review highlights the impact of reversible ERSs in hydrogen moni toring to contextualize their current and potential applicability. First sensing mechanisms for gasochromic tungsten oxide films and switchable metal hydrides are critically overviewed. Then pivotal strategies targeting real-time monitorization indoors and permanent leak recording outdoors are presented along with standard hydrogen leakage scenarios elucidating opportunities for ERSs. Finally important challenges and desirable userfriendly concepts are discussed with the purpose of narrowing the gap between this class of sensors and the forthcoming hydrogen society.