Germany

Within the European Green Deal the European industry is summoned to transform towards a green and circular economy to reduce CO2-emissions and reach climate goals. Special focus is on the chemical industry to boost recycling processes for plastics exploit resource efficiency potentials and switch to a completely renewable feedstock (defossilization). Despite common understanding that drastic changes have to take place it is yet unknown how the industrial transformation should be accomplished. This work explains how a cost-optimal defossilization of the chemical industry in the context of national greenhouse gas (GHG) mitigation strategies look like. The central part of this investigation is based on a national energy system model to optimize the future energy system design of Germany as a case study for a highly industrialized country. A replacement of fossil-based feedstocks by renewable feedstocks leads to a significant increase in hydrogen demand by þ40% compared to a reference scenario. The resulting demand of hydrogen-based energy carriers including the demand for renewable raw materials must be produced domestically or imported. This leads to cumulative additional costs of the transformation that are 32% higher than those of a reference scenario without defossilization of the industry. Fischer-Tropsch synthesis and the methanol-to-olefins route can be identified as key technologies for the defossilization of the chemical industry.

Hydrogen produced via water electrolysis from renewable electricity is considered a key energy carrier to defossilize hard-to-electrify sectors. Solid oxide cells (SOC) based reactors can supply hydrogen not only in electrolysis but also in fuel cell mode when operating with (synthetic) natural gas or biogas at low conversion (polygeneration mode). However the scale-up of SOC reactors to the multi-MW scale is still a research topic. Strategies for transient operation depending on electricity intermittency still need to be developed. In this work a unique testing environment for SOC reactors allows reversible operation demonstrating the successful switching between electrolysis (− 75 kW) and polygeneration (25 kW) modes. Transient and steady state experiments show promising performance with a net hydrogen production of 53 kg day− 1 in SOEL operation with ca. − 75 kW power input. The experimental results validate the scaling approach since the reactor shows homogenous temperature profiles.

As part of the United Nations’ (UN) Sustainable Development Goal 7 (SDG7) SDG target 7.1 recognizes universal electrification and the provision of clean cooking fuel as two fundamental challenges for global society. Faltering progress toward SDG target 7.1 calls for innovative technologies to stimulate advancements. Hydrogen has been proposed as a versatile energy carrier to be applied in both pillars of SDG target 7.1: electrification and clean cooking. This paper conducts a semi-systematic literature review to provide the status quo of research on the application of hydrogen in the rationale of SDG 7.1 covering the technical integration pathways as well as the key economic environmental and social aspects of its use. We identify decisive factors for the future development of hydrogen use in the rationale of SDG target 7.1 and by complementing our analysis with insights from the related literature propose future avenues of research. The literature on electrification proposes that hydrogen can serve as a backup power supply in rural off-grid communities. While common electrification efforts aim to supply appliances that use lower amounts of electricity a hydrogen-based power supply can satisfy appliances with higher power demands including electric cook stoves while simultaneously supporting clean cooking efforts. Alternatively with the exclusive aim of stimulating clean cooking hydrogen is proposed to be used as a clean cooking fuel via direct combustion in distribution and utilization infrastructures analogous to Liquid Petroleum Gas (LPG). While expected economic and technical developments are seen as likely to render hydrogen technologies economically competitive with conventional fossil fuels in the future the potential of renewably produced hydrogen usage to reduce climate-change impacts and point-of-use emissions is already evident today. Social benefits are likely when meeting essential safety standards as a hydrogen-based power supply offers service on a high tier that might overachieve SDG 7.1 ambitions while hydrogen cooking via combustion fits into the existing social habits of LPG users. However the literature lacks clear evidence on the social impact of hydrogen usage. Impact assessments of demonstration projects are required to fill this research gap.

Airlines are faced with the challenge of reducing their environmental footprint in an effort to push for climate-neutral initiatives that comply with international regulations. In the past the aviation industry has followed the approach of incremental improvement of fuel efficiency while simultaneously experiencing significant growth in annual air traffic. With the increase in air traffic negating any reduction in Greenhouse Gas (GHG) emissions more disruptive technologies such as hydrogen-based onboard power generation are required to reduce the environmental impact of airline operations. However despite initial euphoria and first conceptual studies for hydrogen-powered aircraft several decades ago there still has been no mass adoption to this day. Besides the challenges of a suitable ground infrastructure this can partly be attributed to uncertainties with the associated maintenance requirements and the expected operating costs to demonstrate the economic viability of this technology. With this study we address this knowledge gap by estimating changes towards scheduled maintenance activities for an airborne hydrogen storage and distribution system. In particular we develop a detailed system design for a hydrogen-powered fuel-cell-based auxiliary power generation and perform a comparative analysis with an Airbus A320 legacy system. That analysis allows us to (a) identify changes for the expected maintenance effort to enhance subsequent techno-economic assessments (b) identify implications of specific design assumptions with corresponding maintenance activities while ensuring regulatory compliance and (c) describe the impact on the resulting task execution. The thoroughly examined interactions between system design and subsequent maintenance requirements of this study can support practitioners in the development of prospective hydrogen-powered aircraft. In particular it allows the inclusion of maintenance implications in early design stages of corresponding system architectures. Furthermore since the presented methodology is transferable to different design solutions it provides a blueprint for alternative operating concepts such as the complete substitution of kerosene by hydrogen to power the main engines.

During a severe accident in a nuclear power plant one of the potential threats to the containment is the occurrence of energetic combustion events. In modern plants Severe Accident Management Guidelines (SAMG) as well as dedicated mitigation hardware are in place to minimize/mitigate this combustion risk and thus avoid the release of radioactive material into the environment. Advancements in SAMGs are in the focus of AMHYCO an EU-funded Horizon 2020 project officially launched on October 1st 2020. The project consortium consists of 12 organizations (from six European countries and one from Canada) and is coordinated by the Universidad Politécnica de Madrid (UPM). The progress made in the first two years of the AMHYCO project is here presented. A comprehensive bibliographic review has been conducted providing a common foundation to build the knowledge gained during the project. After an extensive set of accident transients simulated both for phases occurring inside and outside the reactor pressure vessel a set of challenging sequences from the combustion risk perspective for different power plant types were identified. At the same time three generic containment models for the three considered reactor designs have been created to provide the full containment analysis simulations with lumped parameter models 3-dimensional containment codes and CFD codes. In order to further consolidate the model base combustion experiments and performance tests on passive auto-catalytic recombiners under explosion prone H2/CO atmospheres were performed at CNRS (France) and FZJ (Germany). Finally it is worth saying that the experimental data and engineering models generated from the AMHYCO project are useful for other industries outside the nuclear one.

Cryogenic liquid is often stored in a vacuum insulated Dewar vessel for a high efficiency of thermal insulation. Multi-layer insulation (MLI) can be further applied in the double-walled vacuum space to reduce the heat transfer from the environment to the stored cryogenic fluid. However in loss-of-vacuum accident (LOVA) scenarios heat flux across the MLI will raise to orders of magnitudes larger than with an intact vacuum shield. The cryogenic liquid will boil intensively and pressurize the vessel due to the heat ingress. The pressurization endangers the integrity of the vessel and poses an extra catastrophic risk if the vapor is flammable e.g. hydrogen. Therefore safety valves have to be designed and installed appropriately to make sure the pressure is limited to acceptable levels. In this work the dynamic process of the heat and mass transfers in the LOVA scenarios is studied theoretically. The mass deposition - desublimation of gaseous nitrogen on cryogenic surfaces is modeled as it provides the dominant contribution of the thermal load to the cryogenic fluid. The conventional heat convection and radiation are modeled too although they play only secondary roles as realized in the course of the study. The temperature dependent thermal properties of e.g. gaseous and solid nitrogen and stainless steel are used to improve the accuracy of calculation in the cryogenic temperature range. Presented methodology enabling the computation of thermodynamic parameters in the cryogenic storage system during LOVA scenarios provides further support for the future risk assessment and safety system design.

In recent years new chemical release agents based on silane are being used in the tire industry. Silane is an inorganic chemical compound consisting of a silicon backbone and hydrogen. Silanes can be thermally decomposed into high-purity silicon and hydrogen. If silane is stored and transported in Intermediate Bulk Containers (IBCs) equipped with safety valves in vented semi-confined spaces such as ISO-Containers hydrogen can be accumulated and become explosive mixture with air. A conservative CFD analysis using the GASFLOW-MPI code has been carried out to assess the hydrogen risk inside the vented containers. Two types of containers with different natural ventilation systems were investigated under various hypothetical accident scenarios. A continuous release of hydrogen due to the chemical decomposition of silane from IBCs was studied as the reference case. The effect of the safety valves on hydrogen accumulation in the container which results in small pulsed releases of hydrogen was investigated. The external effects of the sun and wind on hydrogen distribution and ventilation were also evaluated. The results can provide detailed information on hydrogen dispersion and mixing within the vented enclosures and used to evaluate the hydrogen risks such as flammability. Based on the assumptions used in this study it indicates that the geometry of ventilation openings plays a key role in the efficiency of the indoor air exchange process. In addition the use of safety valves makes it possible to reduce the concentration of hydrogen by volume in air compared to the reference case. The effect of the sun which results in a temperature difference between two container walls allows a strong mixing of hydrogen and air which helps to obtain a concentration lower than both the base case and the case of the pulsed releases. But the best results for the venting process are obtained with the wind that can drive the mixture to the downwind wall vent holes.

In this work real scale experiments involving hydrogen dispersion inside a road tunnel have been modelled using the Computational Fluid Dynamics (CFD) methodology. The aim is to assess the performance of the ADREA-HF CFD tool against full-scale tunnel dispersion data resulting from high-pressure hydrogen leakage through Thermal Pressure Relief Device (TPRD) of a vehicle. The assessment was performed with the help of experiments conducted by the French Alternative Energies and Atomic Energy Commission (CEA) in a real inclined tunnel in France. In the experiments helium as hydrogen surrogate has been released from 200 bar storage pressure. Several tests were carried out examining different TPRD sizes and release directions (upwards and downwards). For the CFD evaluation two tests were considered: one with downwards and one with upwards release both through a TPRD with a diameter of 2 mm. The comparison between the CFD results and the experiments shows the good predictive capabilities of the ADREA-HF code that can be used as a safety tool in hydrogen dispersion studies. The comparison reveals some of the strengths and weaknesses of both the CFD and the experiments. It is made clear that CFD can contribute to the design of the experiments and to the interpretation of the experimental results.

The large deployment of hydrogen technologies for new applications such as heat power mobility and other emerging industrial utilizations is essential to meet targets for CO2 reduction. This will lead to an increase in the number of hydrogen installations nearby local populations that will handle hydrogen technologies. Local regulations differ and provide different safety and/or separation distances in different geographies. The purpose of this work is to give an insight on different methodologies and recommendations developed for hydrogen (mainly) risk management and consequences assessment of accidental scenarios. The first objective is to review available methodologies and to identify the divergent points on the methodology. For this purpose a survey has been launched to obtain the needed inputs from the subtask participants. The current work presents the outcomes of this survey highlighting the gaps and suggesting the prioritization of the actions to take to bridge these gaps.

A series of unconfined hydrogen detonation bench-mark experiments are analyzed with respect to CFD code validation and safety measures development. 1-Dimensional in-house code COM1D was applied for validation against experimental data for unconfined detonation of a hemispherical envelope of about 3- and 5-m radius with hydrogen-air mixtures from 20 to 30% hydrogen in air. The code demonstrates a very good agreement with experimental data and allows an adequate simulation of the unconfined hydrogen detonation. All calculated data were scaled in Sachs coordinates to compare with experimental data and to approximate the data for practical evaluation of safety distances. Numerical experiments with different hydrogen inventories from 50 g to 50 kg and different sizes of the cloud from 1 to 2 m radius of the same amount of hydrogen 50g were carried out to clarify the problem of energy of gaseous explosion responsible for the strength of blast wave. Additionally a comparison of hydrogen-air explosion pressure with blast wave properties from the hypothetical cloud of hot compressed combustion products (P=Picc; T=Ticc) and simply a hot air of the same initial pressure and temperature as combustion products showed very good agreement of shock wave strength at far distances beyond the cloud. This confirms the governing role of energy of combustion on blast wave propagation and its ability to scale the strength of blast waves. The dynamics of the explosion process and combustion product expansion were also analyzed experimentally and numerically to evaluate the dimension of the heat radiation zone and heat flux from combustion products. To demonstrate the capability of tested COM1D code the modeling and analysis of high-pressure hydrogen tanks rupture at 350 and 700 bar were conducted to investigate blast wave strength and evaluate the safety distances.

HyCARE project supported by the Clean Hydrogen Partnership of the European Union deals with a prototype of hydrogen storage tank using a solid-state hydrogen carrier. Up to 40 kilograms of hydrogen are stored in twelve tanks at less than 50 barg and less than 100 °C. The innovative design is based on a standard twenty-foot container including twelve TiFe-based metal hydride (MH) hydrogen storage tanks coupled with a thermal energy storage in phase change materials (PCM). This article aims at showing the main risks related to hydrogen storage in a MH system and the safety barriers considered based on HyCARE’s specific risk analysis.<br/>Regarding the TiFe MH material used to store hydrogen experimental tests showed that the exposure of the MH to air or water did not cause spontaneous ignition. Furthermore an explosion within the solid MH cannot propagate due to internal pore size. Additionally in case of leakage the speed of hydrogen desorption from the MH is self-limited which is an important safety characteristic since it reduces the potential consequences from the hydrogen release scenario.<br/>Regarding the integrated system the critical scenarios identified during the risk analysis were: explosion due to release of hydrogen inside or outside the container internal explosion inside MH tanks due to accidental mix of hydrogen and air and asphyxiation due to inert gas accumulation in the container. This identification phase of the risk analysis allowed to pinpoint the most relevant safety barriers already in place and recommend additional ones if needed to further reduce the risk that were later implemented.<br/>The main safety barriers identified were: material and component selection (including the MH selected) safety interlocks safety valves ventilation gas detection and safety distances.<br/>The risk management process based on risk identification and assessment contributed to coherently integrate inherently safe design features and safety barriers.

One of the significant safety concerns in large-scale storage and transportation of liquefied (cryogenic) hydrogen (LH2) is the formation of flammable hydrogen/air mixtures after leakages during storage or transportation. Especially in maritime transportation hydrogen accumulations could occur within large and congested geometries. The installation of passive auto-catalytic recombiners (PARs) is a suitable mitigation measure for local areas where venting is insufficient or even impossible. Numerical models describing the operational behavior of PARs are required to allow for optimizing the location and assessing the efficiency of the mitigation measure. In the present study the operational behavior of a PAR with a compact design has been experimentally investigated. In order to obtain data for model validation an experimental program has been performed in the REKO-4 facility a 5.5 m³ vessel. The test procedure includes two phases steady-state and dynamic. The results provide insights into the hydrogen recombination rates and catalyst temperatures under different boundary conditions.

Among the different hydrogen premixed combustion concepts direct injection (DI) is one of the most promising for internal combustion engine (ICE) applications. However to fully exploit the benefits of this solution the optimization of the mixture preparation process is a crucial factor. In the present work a study of the hydrogenair mixture formation process in a DI H2-ICE for off-road applications was performed through 3D-CFD simulations. First a sensitivity analysis on the injection timing was carried out to select the optimal injection operating window capable of maximizing mixture homogeneity without a significant volumetric efficiency reduction. Then different spray injector guiding caps were tested to assess their effect on in-cylinder dynamics and mixture characteristics consequently. Finally the impact of swirl intensity on hydrogen distribution has been assessed. The optimization of the combustion chamber geometry has allowed the achievement of significant improvements in terms of mixture homogeneity.

This study reviews existing simulation models and describes a selected model for analysing combustion dynamics in hydrogen and natural gas mixtures specifically within non-ferrous melting furnaces. The primary objectives are to compare the combustion characteristics of these two energy carriers and assess the impact of hydrogen integration on furnace operation and efficiency. Using computational fluid dynamics (CFD) simulations incorporating actual furnace geometries and a detailed combustion and NOx emission prediction model this research aims to accurately quantify the effects of hydrogen blending. Experimental tests on furnaces using only natural gas confirmed the validity of these simulations. By providing precise predictions for temperature distribution and NOx emissions this approach reduces the need for extensive laboratory testing facilitates broader exploration of design modifications accelerates the design process and ultimately lowers product development costs.

In the quest for a sustainable future energy-intensive industries (EIIs) stand at the forefront of Europe’s decarbonisation mission. Despite their significant emissions footprint the path to comprehensive decarbonisation remains elusive at EU and national levels. This study scrutinises key sectors such as non-ferrous metals steel cement lime chemicals fertilisers ceramics and glass. It maps out their current environmental impact and potential for mitigation through innovative strategies. The analysis spans across Spain Greece Germany and the Netherlands highlighting sector-specific ecosystems and the technological breakthroughs shaping them. It addresses the urgency for the industry-wide adoption of electrification the utilisation of green hydrogen biomass bio-based or synthetic fuels and the deployment of carbon capture utilisation and storage to ensure a smooth transition. Investment decisions in EIIs will depend on predictable economic and regulatory landscapes. This analysis discusses the risks associated with continued investment in high-emission technologies which may lead to premature decommissioning and significant economic repercussions. It presents a dichotomy: invest in climate-neutral technologies now or face the closure and offshoring of operations later with consequences for employment. This open discussion concludes that while the technology for near-complete climate neutrality in EIIs exists and is rapidly advancing the higher costs compared to conventional methods pose a significant barrier. Without the ability to pass these costs to consumers the adoption of such technologies is stifled. Therefore it calls for decisive political commitment to support the industry’s transition ensuring a greener more resilient future for Europe’s industrial backbone.

Hydrogen produced by renewable energy sources (green hydrogen) is at the centrepiece of European decarbonization strategies necessitating large imports from third countries. Egypt potentially stands out as major production hub. While technical and economic viability are broadly discussed in literature analyses of local acceptance are absent. This study closes this gap by surveying 505 locals in the Suez Canal Economic Zone (Port Said and Suez) regarding their attitudes towards renewable energy development and green hydrogen production. We find overall support for both national deployment and export to Europe. Respondents see a key benefit in rising income thereby strongly underlying the economic argument. Improved trade relationships or improved political relationships are seen as potential benefits of export but as less relevant for engaging in cooperation putting a spotlight on local benefits. Our study suggests that the local population is more positive than negative towards the development and scaling up of green hydrogen projects in Egypt.

This study introduces a hybrid energy storage system that combines advanced flywheel technology with hydrogen fuel cells and electrolyzers to address the variability inherent in renewable energy sources like solar and wind. Flywheels provide quick energy dispatch to meet peak demand while hydrogen fuel cells offer sustained power over extended periods. The research explores the strategic integration of these technologies within a hybrid photovoltaic (PV)-flywheel‑hydrogen framework aiming to stabilize the power supply. To evaluate the impact of flywheel integration on system sizing and load fluctuations simulations were conducted both before and after the flywheel integration. The inclusion of the flywheel resulted in a more balanced energy production and consumption profile across different seasons notably reducing the required fuel cell capacity from 100 kW to 30 kW. Additionally the integration significantly enhanced system stability enabling the fuel cell and electrolyzer to operate at consistent power during load fluctuations. The system achieved efficiencies of 71.42 % for the PEM electrolyzer and 62.14 % for the PEM fuel cell. However the introduction of the flywheel requires a higher capacity of PV modules and a larger electrolyzer. The overall flywheel's efficiency was impacted by parasitic energy losses resulting in an overall efficiency of 46.41 %. The minimum efficiency observed across various scenarios of the model studied was 3.14 % highlighting the importance of considering these losses in the overall system design. Despite these challenges the hybrid model demonstrated a substantial improvement in the reliability and stability of renewable energy systems effectively bridging short-term and long-term energy storage solutions.

Hydrogen is a versatile energy carrier which can be produced from variety of feedstocks stored and transported in various forms for multi-functional end-uses in transportation energy and manufacturing sectors. Several regional national and supra-national climate policy frameworks emphasize the need value and importance of Fuel cell and Hydrogen (FCH) technologies for deep and sector-wide decarbonization. Despite these multi-faceted advantages familiar and proven FCH technologies such as alkaline electrolysis and proton-exchange membrane fuel cell (PEMFC) often face economic technical and societal barriers to mass-market adoption. There is no single unified standardized and globally harmonized normative definition of costs. Nevertheless the discussion and debates surrounding plausible candidates and/or constituents integral for assessing the economics and value proposition of status-quo as well as developmental FCH technologies are steadily increasing—Life Cycle Costing (LCC) being one of them if not the most important outcome of such exercises.<br/>To that end this review article seeks to improve our collective understanding of LCC of FCH technologies by scrutinizing close to a few hundred publications drawn from representative databases—SCOPUS and Web of Science encompassing several tens of technologies for production and select transportation storage and end-user utilization cases. This comprehensive review forms part of and serves as the basis for the Clean Hydrogen Partnership funded SH2E project whose ultimate goal is the methodical development a formal set of principles and guardrails for evaluating the economic environmental and social impacts of FCH technologies. Additionally the SH2E projects will also facilitate the proper comparison of different FCH technologies whilst reconciling range of technologies methodologies modelling assumptions and parameterization found in existing literature.

Assessing the sustainable development of green hydrogen and assessing its potential environmental impacts using the Life Cycle Assessment is crucial. Challenges in LCA like missing environmental data are often addressed using machine learning such as artificial neural networks. However to find an ML solution researchers need to read extensive literature or consult experts. This research demonstrates how customised LLMs trained with domain-specific papers can help researchers overcome these challenges. By starting small by consolidating papers focused on the LCA of proton exchange membrane water electrolysis which produces green hydrogen and ML applications in LCA. These papers are uploaded to OpenAI to create the LlamaIndex enabling future queries. Using the LangChain framework researchers query the customised model (GPT-3.5-turbo) receiving tailored responses. The results demonstrate that customised LLMs can assist researchers in providing suitable ML solutions to address data inaccuracies and gaps. The ability to quickly query an LLM and receive an integrated response across relevant sources presents an improvement over manually retrieving and reading individual papers. This shows that leveraging fine-tuned LLMs can empower researchers to conduct LCAs more efficiently and effectively.

The measurement of hydrogen concentration in fuel cell systems is an important prerequisite for the development of a control strategy to enhance system performance reduce purge losses and minimize fuel cell aging effects. In this perspective paper the working principles of hydrogen sensors are analyzed and their requirements for hydrogen control in fuel cell systems are critically discussed. The wide measurement range absence of oxygen high humidity and limited space turn out to be most limiting. A perspective on the development of hydrogen sensors based on palladium as a gas-sensitive metal and based on the organic magnetic field effect in organic lightemitting devices is presented. The design of a test chamber where the sensor response can easily be analyzed under fuel cell-like conditions is proposed. This allows the generation of practical knowledge for further sensor development. The presented sensors could be integrated into the end plate to measure the hydrogen concentration at the anode in- and outlet. Further miniaturization is necessary to integrate them into the flow field of the fuel cell to avoid fuel starvation in each single cell. Compressed sensing methods are used for more efficient data analysis. By using a dynamical sensor model control algorithms are applied with high frequency to control the hydrogen concentration the purge process and the recirculation pump.

Over 35% of the CO2 associated with cement production comes from operational energy. The cement industry needs alternative fuels to meet its net zero emissions target. This study investigated the influence of hydrogen mixed with biofuels herein designated net zero fuel as an alternative to coal on the clinker quality and performance of cement produced in an industrial cement plant. Scanning electron microscopy X-ray diffraction and nuclear magnetic resonance were coupled to study the clinker mineralogy and polymorphs. Hydration and microstructure development in plain and slag blended cements based on the clinker were compared to commercial cement equivalent. The results revealed a lower alite/belite ratio but a significant proportion of the belite was of the α’H-C2S polymorph. These reacted faster and compensated for the alite/belite ratio. Gel and micro-capillary pores were densified which reduced total porosity and attained comparable strength to the reference plain and blended cement. This study demonstrates that the investigated net zero fuel-produced clinker meets compositional and strength requirements for plain and blended cement providing a feasible pathway for the cement industry to lower its operational carbon significantly.

The global green hydrogen rush is prone to repeat extractivist patterns at the expense of economies ecologies and communities in the production zones in the Global South. With a socio-ecological risk analysis grounded in energy water and environmental justice scholarship we systematically assess the risks of the ‘green’ hydrogen transition and related injustices arising in 28 countries in the Global South with regard to energy water land and global justice dimensions. Our findings show that risks materialize through the exclusion of affected communities and civil society the enclosure of land and resources for extractivist purposes and through the externalization of socio-ecological costs and conflicts. We further demonstrate that socio-ecological risks are enhanced through country-specific conditions such as water scarcity historical continuities such as post-colonial land tenure systems as well as repercussions of a persistently uneven global politico-economic order. Contributing to debates on power inequality and justice in the global green hydrogen transition we argue that addressing hydrogen risks requires a framework of environmental justice and a transformative perspective that encompasses structural shifts in the global economy including degrowth and a decentering of industrial hegemonies in the Global North.

The import of hydrogen and derivatives forms part of many national strategies and is fundamental to achieving climate protection targets. This paper provides an overview and technical comparison of import pathways for hydrogen and derivatives in terms of efficiency technological maturity and development and construction times with a focus on the period up to 2030. The import of hydrogen via pipeline has the highest system efficiency at 57–67 % and the highest technological maturity with a technology readiness level (TRL) of 8–9. The import of ammonia and methanol via ship and of SNG via pipeline shows efficiencies in the range of 39–64 % and a technological maturity of TRL 7 to 9 when using point sources. Liquid hydrogen LOHC and Fischer-Tropsch products have the lowest efficiency and TRL in comparison. The use of direct air capture (DAC) reduces efficiency and TRL considerably. Reconversion of the derivatives to hydrogen is also associated with high losses and is not achievable for all technologies on an industrial scale up to 2030. In the short to medium term import routes for derivatives that can utilise existing infrastructures and mature technologies are the most promising for imports. In the long term the most promising option is hydrogen via pipelines.

The need to reduce the carbon footprint of conventional energy sources has made green hydrogen a promising solution for the energy transition. The most environmentally friendly way to produce hydrogen is through water-based production using renewable energy. However the availability of fresh water is limited so switching to wastewater instead of fresh water is the key solution to this problem. In response to this issue the present review reports the main findings of the research studies dealing with the feasibility of hydrogen production from wastewater using various technologies including biological electrochemical and advanced oxidation routes. These methods have been studied in a large number of experiments with the aim of investigating and improving the potential of each method. On the other hand the maturity of solar energy technologies has led researchers to focus on the possibility of harnessing this source and combining it with wastewater treatment techniques for the production of green hydrogen. Therefore the present review pays special attention to solar driven hydrogen production from wastewater by highlighting the potential of several technologies for simultaneous water treatment and green hydrogen production from wastewater. Recent results limitations challenges possible improvements and techno-economic assessments reported by several authors as well as future directions of research and industrial implementation in this field are reported.

The defossilization of industry has far-reaching implications regarding the future demand for hydrogen and other forms of energy. This paper presents and applies a fundamental bottom-up model that relies on techno-economic data of industrial production processes. Its aim is to identify across a range of scenarios the most cost-effective low-carbon options considering a variety of production systems. Subsequently it derives the hydrogen and electricity demand that would result from the implementation of these least-cost low-carbon options in process industries in Germany. Aligning with the German government's target year for achieving climate neutrality this study’s reference year is 2045. The primary contribution lies in analyzing which hydrogen-based and direct electrification solutions would be cost-effective for a range of energy price levels under climate-neutral industrial production and what the resulting hydrogen and electricity demand would be. To this end the methodology of this paper comprises the following steps: selection of the relevant industries (I) definition of conventional reference production systems and their low-carbon options (II) investigation and processing of the techno-economic data of the standardized production systems (III) establishment of a scenario framework (IV) determination of the least-cost low-carbon solution of a conventional reference production system under the scenario assumptions made (V) and estimation of the resulting hydrogen and electricity demand (VI). According to the results the expected industrial hydrogen consumption in 2045 ranges from 255 TWh for higher hydrogen prices in or above the range of onshore wind-based green hydrogen supply costs to up to 542 TWh for very low hydrogen prices corresponding to typical blue hydrogen production costs. Meanwhile the direct electricity consumption of the process industries in the results ranges from 122 TWh for these rather low hydrogen prices to 368 TWh for the higher hydrogen prices in the region of or above the hydrogen supply costs from the electrolysis of energy from an onshore wind farm. Most of the break-even hydrogen prices that are relevant to the choice of low-carbon options are in the range of the benchmark purchase costs for blue hydrogen and green hydrogen produced from offshore wind power which span between €40 per MWh and €97 per MWh.