Publications

Aviation is a major contributor to transportation carbon emissions but aims to reduce its carbon footprint. Sustainable and environmentally friendly green hydrogen fuel is essential for decarbonization of this industry. Using the extremely low temperature of liquid hydrogen in aviation sector unlocks the opportunity for cryoelectric aircraft concept which exploits the advantageous properties of superconductors onboard. A significant barrier for green hydrogen adoption relates to its high cost and the immediate need for large-scale production which Proton Exchange Membrane Water Electrolyzers (PEMWE) can address through optimal dynamic performance high lifetimes good efficiencies and importantly scalability. In PEMWE the cell is a crucial component that facilitates the electrolysis process and consists of a polymer membrane and electrodes. To control the required production rate of hydrogen the output power of cell should be monitored which usually is done by measuring the cell’s potential and current density. In this paper five different machine learning (ML) models based on different algorithms have been developed to predict this parameter. Findings of the work highlight that the model based on Cascade-Forward Neural Network (CFNN) is investigated to accurately predict the cell potential of PEMWE under different anodic material and working conditions with an accuracy of 99.998 % and 0.001884 in terms of R2 and root mean square error respectively. It can predict the cell potential with a relative error of less than 0.65 % and an absolute error of below 0.01 V. The Standard deviation of 0.000061 for 50 iterations of stability analysis indicated that this model has less sensitivity to the random selection of training data. By accurately estimating different cell’s output with one model and considering its ultra-fast response CFNN model has the potential to be used for both monitoring and the designing purposes of green hydrogen production.

The decarbonization of the building stock in this paper focusing the single-family house sector in Germany is essential to achieve the climate goals. In fact as the largest part of the building stock it represents more than 65 % of the entire German residential building stock. Current strategies and regulations have demonstrated low impact on carbon emission reduction due to poor renovation rates particularly in the single-family house typology. The present study analyzes the potential of carbon emission reduction prioritizing local renewable energy generation and storage in combination with improved building energy systems. Through a simulation-based approach it considers reference buildings of different age classes and formulates variants for improving strategies with different levels of retrofit under the premise of a fully renewable locally generated energy supply. Based on the potential for solar energy supply the variants consider the seasonal shift that needs to be stored and particularly the role of hydrogen as an energy storage medium. The study´s goal is quantifying the impacts of the local renewable energy production its required storage capacity depending on the retrofit depth both for estimating the potential of transforming the single-family house stock to net zero carbon emissions.

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.

Solar hydrogen and electricity are promising high energy-density renewable sources. Although photochemistry or photovoltaics are attractive routes special challenge arises in sunlight conversion efficiency. To improve efficiency various semiconductor materials have been proposed with selective sunlight absorption. Here we reported a hybrid system synergizing photo-thermochemical hydrogen and photovoltaics harvesting full-spectrum sunlight in a cascade manner. A simple suspension of Au-TiO2 in water/methanol serves as a spectrum selector absorbing ultraviolet-visible and infrared energy for rapid photo-thermochemical hydrogen production. The transmitted visible and near-infrared energy fits the photovoltaic bandgap and retains the high efficiency of a commercial photovoltaic cell under different solar concentration values. The experimental design achieved an overall efficiency of 4.2% under 12 suns solar concentration. Furthermore the results demonstrated a reduced energy loss in full-spectrum energy conversion into hydrogen and electricity. Such simple integration of photo-thermochemical hydrogen and photovoltaics would create a pathway toward cascading use of sunlight energy.

Green hydrogen will play a key role in the transition to a carbon-neutral energy system. This study addresses the challenge of supplying baseload green hydrogen through an integrated off-grid alkaline water electrolyzer (AWE) plant wind and solar photovoltaic (PV) power a battery energy storage system (BESS) and a hydrogen storage system based on salt and rock cavern geologies. The capacities of the components and the hydrogen storage size are optimized simultaneously with the control of the AWE plant to minimize the levelized cost of hydrogen (LCOH2) of the gas supplied. The operation of the system is simulated over 30 years with a 15 min time resolution considering degradation operating expenses and component replacements. Power generation data collected from a wind farm and a solar PV installation both located in southeastern Finland are used for system simulation. A sensitivity analysis exploring different hydrogen demand rates discount rates and installation years is conducted for both systems considering rock and salt caverns providing the optimal configuration for each case. It is found that for the price scenario of the year 2025 for a combined 100 MW AWE and compressor the optimal hydrogen demand rate is 12 kg/min with an LCOH2 of 3.14 e/kg and 2.77 e/kg in systems including rock and salt caverns respectively.

To achieve deep decarbonization renewable energy generation must be substantially increased. The technologies with the lowest levelized cost of electricity (LCOE) are land-based photovoltaics (PVs) and wind energy. Agri-PVs offer the potential for dual land use combining energy generation with agricultural activities. However the costs of agri-PVs are higher than those of ground-mounted PV. To enhance the competitiveness of agri-PV we investigate the synergies between agri-PVs and hydrogen electrolysis through process simulation. Additionally we analyse current technological developments in agri-PVs based on a market analysis of start-up companies. Our results indicate that the levelized cost of hydrogen (LCOH) can be comparable for agri-PVs and ground-mounted PVs due to the somewhat smoother electricity generation for the same installed capacity. The market analysis reveals the emergence of a technology ecosystem that integrates agri-PVs with next-generation agricultural technologies such as sensors robotics and artificial intelligence (AI) agents along with localized electricity generation forecasting. The integrated agri-PV and hydrogen generation system has significant global scaling potential for renewable energy generation. Furthermore it positively impacts local economies and energy resilience may reduce water scarcity in agriculture and leverages advancements in AI robotics PV and hydrogen generation technologies.

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.

Hydrogen flight is one important part of the way to net zero aviation. However safety challenges around refuelling are not well understood but are paramount to enable airports to be more comfortable with using hydrogen in the airport environment. This study investigates safety considerations of hydrogen aircraft refuelling at airports. Technical and human factor risks are explored as well as risk assessment models. Two focus groups were conducted in 2022. Data was analysed using NVivo revealing major themes including the mental and physical performance of refuellers technical aspects of refuelling stations environmental factors and the use of risk assessment models. These findings contribute significantly to an understanding of hydrogen refuelling challenges in busy airport environments. Recommendations help airports preparing for hydrogen as a fuel source further supporting the transition towards net zero aviation. Future research could focus on carrying out experiments analysing chemical reactions between kerosene and hydrogen vapours and testing the identified risk assessment tools in different airport environments.

Quantitative Risk Assessments (QRA) is an important tool for enabling safe deployment of hydrogen technologies and is increasingly embedded in the permitting process. Following the framework developed in our companion paper we conducted a detailed QRA on the uncontrolled releases from a high-capacity hydrogen fueling station with liquid hydrogen (LH2) storage. We characterized gaseous and liquid hydrogen releases determined the causal pathways that led to them and the frequency of the potential hazardous outcomes. These hazardous scenarios were modeled to estimate their potential harm on station users. The analysis results reveal that the total frequency for a major hydrogen release is 1.48 × 10− 2 times per station-year. However considering the control barriers in the station the expected frequency of ignition events is reduced to 1.35 × 10− 5 ignition per stationyear. The expected fatality risk is within the tolerable limit for hydrogen fueling stations but still remains higher than that of conventional gasoline stations. The most severe scenario identified involves a high-pressure GH2 release leading to a jet fire with jet flames reaching up to 15 m in length. The most probable sources of GH2 releases are from the gaseous hydrogen filters while for LH2 releases cryogenic pumps are the primary contributors. To improve the accuracy of QRAs for LH2 systems we identified critical gaps including the need for improved reliability data that must be addressed.

This study investigates the techno-economic feasibility of a Power-to-X (PtX) system by integrating solarpowered hydrogen electrolysis with carbon capture and Fischer-Tropsch (FT) synthesis processes for e-fuel production in Basra Iraq. To this aim a comprehensive modeling framework is developed to cover the detailed simulation of E-fuel production along with the system cost analysis. The proposed PtX system is supposed to be located near the Hartha power plant which is one of the main sources of electricity in the Basra region allowing for the utilization of captured CO2 from the power plant’s exhaust gas. The PtX plant design shows significant potential producing 2.44 tonnes of (C12-C20) hydrocarbons and 3.36 tonnes of (C21-C40) heavy oils annually. This is achieved by utilizing 7.5 and 74.2 tonnes per year of hydrogen generated from solar electrolysis and captured CO2 respectively. A cash flow analysis covering 25 years shows that an E-fuel market price of $10 per liter is needed to achieve a positive cash flow within 15 years. The study also indicates that implementing a $200 per tonne carbon tax improves the economic feasibility of the project by allowing for earlier positive cash flows from 6 years and a quicker break-even point at the current E-fuel market price of $2 per liter with a NPV of $ 464 million. Sensitivity analysis reveals that higher carbon taxes and e-fuel prices enhance profitability by reducing payback periods and increasing the NPV. However an increase in hydrogen production costs introduces substantial risk with higher costs decreasing economic viability. The feasibility assessment suggests that despite the substantial initial investment needed for various system components the long-term advantages include reduced CO2 emissions and the potential for Iraq to emerge as a leader in renewable fuel production. Stable policies robust carbon taxes and cost-efficient hydrogen production are essential for the successful implementation of PtX project.