Publications

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.

This study assessed the feasibility of integrating a green hydrogen value chain into the local industry examining two case studies by comparing four scenarios. The optimization focused on generating electricity from stationary renewable sources such as solar or through Power Purchase Agreements to produce sufficient hydrogen in electrolyzers. Current demand profiles renewable participation targets electricity supply sources levelized costs of energy and hydrogen and technology options were considered. The most cost-effective scenario showed a levelized cost of energy of 0.032 and 0.05 US$/kWh and a hydrogen cost below 1.0 US$/kgH2 for cases 1 and 2 respectively. A sensitivity analysis highlighted the critical influence of fuel cell technology on cost modification underscoring the importance of focusing cost reduction strategies on these technologies to enhance the economic viability of the green hydrogen value chain. Specifically a high sensitivity towards reducing the levelized costs of energy and hydrogen in the port sector with adjustments in fuel cell technology costs was identified indicating the need for specific policies and supports to facilitate their adoption.

After the Paris Agreement was signed in 2015 many countries worldwide focused on the hydrogen economy aiming for eco-friendly and renewable energy by moving away from the existing carbon economy which has been the primary source of global warming. Hydrogen is the most common element on Earth. As a light substance hydrogen can diffuse quickly; however it also has a small risk of explosion. Representative explosion accidents have included the Muskingum River Power Plant Vapor Cloud Explosion accident in 2007 and the Silver Eagle Refinery Vapor Cloud Explosion accident in 2009. In addition there was an explosion in a hydrogen tank in Gangneung Korea in May 2019 and a hydrogen refueling station (HRS) in Norway exploded in 2018. Despite this risk Korea is promoting the establishment of HRSs in major urban centers including downtown areas and public buildings by using the Regulatory Sandbox to install HRSs. This paper employed the Hydrogen Risk Assessment Model (HyRAM) of Sandia National Laboratories (SNL) a quantitative risk assessment (QRA) program specialized in hydrogen energy for HRSs installed in major urban hubs. A feasibility evaluation of the site conditions of an HRS was conducted using the French land use planning method based on the results obtained through evaluation using the HyRAM and the overpressure results of PHAST 8.0. After a risk assessment we confirmed that an HRS would be considered safe even if it was installed in the city center within a radius of influence of jet fires and overpressure.

Economical offshore wind developments depend on alternatives for cost-efficient transmission of the generated energy to connecting markets. Distance to shore availability of an offshore power grid and scale of the wind farm may impede export through power cables. Conversion to H2 through offshore electrolysis may for certain offshore wind assets be a future option to enable energy export. Here we analyse the cost sensitivity of offshore electrolysis for harvesting offshore wind in the North Sea using a technology-detailed multi-carrier energy system modelling framework for analysis of energy export. We include multiple investment options for electric power and hydrogen export including HVDC cables new hydrogen pipelines tie-in to existing pipelines and pipelines with linepacking. Existing hydropower is included in the modelling and the effect on offshore electrolysis from increased pumping capacity in the hydropower system is analysed. Considering the lack of empirical cost data on offshore electrolysis as well as the high uncertainty in future electricity and H2 prices we analyse the cost sensitivity of offshore electrolysis in the North Sea by comparing costs relative to onshore electrolysis and energy prices relative to a nominal scenario. Offshore electrolysis is shown to be particularly sensitive to the electricity price and an electricity price of 1.5 times the baseline assumption was needed to provide sufficient offshore energy for any significant offshore electrolysis investments. On the other hand too high electricity prices would have a negative impact on offshore electrolysis because the energy is more valuable as electricity even at the cost of increased wind power curtailment. This shows that there is a window-of-opportunity in terms of onshore electricity where offshore electrolysis can play a significant role in the production of H2 . Pumped hydropower increases the maximum installed offshore electrolysis at the optimal electricity and H2 prices and makes offshore electrolysis more competitive at low electricity prices. Linepacking can make offshore electrolysis investments more robust against low H2 and high electricity prices as it allow for more variable H2 production through storing excess energy from offshore. The increased electrolysis capacity needed for variable electrolyser operation and linepacking is installed onshore due to its lower CAPEX compared to offshore installations.

Hydrogen is seen as a prime choice for complete replacement of gasoline so as to achieve zero-emissions energy and mobility. Combining the use of this alternative fuel with a circular economy approach for giving new life to the existing fleet of passenger cars ensures further benefits in terms of cost competitiveness. Transforming spark ignition (SI) engines to H2 power requires relatively minor changes and limited added components. Within this framework the conversion of a small-size passenger car to hydrogen fueling was evaluated based on 0D/1D simulation. One of the methods to improve efficiency is to apply exhaust gas recirculation (EGR) which also lowers NOx emissions. Therefore the previous version of the quasi-dimensional model was modified to include EGR and its effects on combustion. A dedicated laminar flame speed model was implemented for the specific properties of hydrogen and a purpose-built sub-routine was implemented to correctly model the effects of residual gas at the start of combustion. Simulations were performed in several operating points representative of urban and highway driving. One of the main conclusions was that highpressure recirculation was severely limited by the minimum flow requirements of the compressor. Low-pressure EGR ensured wider applicability and significant improvement of efficiency especially during partial-load operation specific to urban use. Another benefit of recirculation was that pressure rise rates were predicted to be more contained and closer to the values expected for gasoline fueling. This was possible due to the high tolerance of H2 to the presence of residual gas.

Alternative fuels such as hydrogen compressed natural gas and liquefied natural gas are considered as feasible energy carriers. Selected positive factors from the EU climate and energy policy on achieving climate neutrality by 2050 highlighted the need for the gradual expansion of the infrastructure for alternative fuel. In this research continuity equations and the first and second laws of thermodynamics were used to develop a theoretical model to explore the impact of hydrogen and natural gas on both the filling process and the ultimate in-cylinder conditions of a type IV composite cylinder (20 MPa for CNG 35 MPa and 70 MPa for hydrogen). A composite tank was considered an adiabatic system. Within this study based on the GERG-2008 equation of state a thermodynamic model was developed to compare and determine the influence of (i) hydrogen and (ii) natural gas on the selected thermodynamic parameters during the fast-filling process. The obtained results show that the cylinder-filling time depending on the cylinder capacity is approximately 36–37% shorter for pure hydrogen compared to pure methane and the maximum energy stored in the storage tank for pure hydrogen is approximately 28% lower compared to methane whereas the total entropy generation for pure hydrogen is approximately 52% higher compared to pure methane.

This contribution delves into the transformative effects of the Russian–Ukrainian war on the discourse surrounding German hydrogen. Employing structural topical modeling (STM) on a vast dataset of 2192 newspaper articles spanning from 2019 to 2022 it aims to uncover thematic shifts attributed to the Russian invasion of Ukraine. The onset of the war in February 2022 triggered a significant pivot in the discourse shifting it from sustainability and climate-change mitigation to the securing of energy supplies through new partnerships particularly in response to Russia’s unreliability. Germany started exploring alternative energy trading partners like Canada and Australia emphasizing green hydrogen development. The study illustrates how external shocks can expedite the uptake of new technologies. The adoption of the “H2 readiness” concept for LNG terminals contributes to the successful implementation of green hydrogen. In summary the Russian–Ukrainian war profoundly impacted the German hydrogen discourse shifting the focus from sustainability to energy supply security underscoring the interconnectedness of energy security and sustainability in Germany’s hydrogen policy.

To improve the renewable energy consumption capacity of integrated energy system (IES) and reduce the carbon emission level of the system a low-carbon economic dispatch model of IES with coupled power-to-gas (P2G) and hydrogen-doped gas units (HGT) under the stepped carbon trading mechanism is proposed. On the premise of wind power output uncertainty the operating characteristics of the coupled electricity-to-gas equipment in the system are used to improve the wind abandonment problem of IES and increase its renewable energy consumption capacity; HGT is introduced to replace the traditional combustion engine for energy supply and on the basis of refined P2G a part of the volume fraction of hydrogen obtained from the production is extracted and mixed with methane to form a gas mixture for HGT combustion so as to improve the low-carbon economy of the system. The ladder type carbon trading mechanism is introduced into IES to guide the system to control carbon emission behavior and reduce the carbon emission level of IES. Based on this an optimal dispatching strategy is constructed with the economic goal of minimizing the sum of system operation cost wind abandonment cost carbon trading cost and energy purchase cost. After linearization of the established model and comparison analysis by setting different scenarios the wind power utilization rate of the proposed model is increased by 24.5% and the wind abandonment cost and CO2 emission are reduced by 86.3% and 10.5% respectively compared with the traditional IES system which achieves the improvement of renewable energy consumption level and low carbon economy.

In the transition towards a more sustainable energy system hydrogen is seen as the key low-emission energy source. However the limited H2 volumetric density hinders its transportation. To overcome this issue liquid organic hydrogen carriers (LOHCs) molecules that can be hydrogenated and upon arrival dehydrogenated for H2 release have been proposed as hydrogen transport media. Considering toluene and dibenzyltoluene as representative carriers this work offers a systematic methodology for the analysis and the comparison of LOHCs in view of identifying cost-drivers of the overall value-chain. A detailed Aspen Plus process simulation is provided for hydrogenation and dehydrogenation sections. Simulation results are used as input data for the economic assessment. The process economics reveals that dehydrogenation is the most impactful cost-item together with the carrier initial loading the latter related to the LOHC transport distance. The choice of the most suitable molecule as H2 carrier ultimately is a trade-off between its hydrogenation enthalpy and cost.

This study proposes a multitype electrolytic collaborative hydrogen production model for optimizing the capacity configuration of renewable energy off grid hydrogen production systems. The electrolytic hydrogen production process utilizes the synergistic electrolysis of an alkaline electrolyzer (AEL) and proton exchange membrane electrolyzer (PEMEL) fully leveraging the advantages of the low cost of the AEL and strong regulation characteristics of the PEMEL. For the convenience of the optimization solution the article constructs a mixed linear optimization model that considers the constraints during system operation with the objective function of minimizing total costs while meeting industrial production requirements. Gurobi is used for the optimal solution to obtain the optimal configuration of a renewable energy off grid hydrogen production system. By comparing and analyzing the optimal configuration under conventional load and high-load conditions it is concluded that collaborative electrolysis has advantages in improving resource consumption and reducing hydrogen production costs. This is of great significance for optimizing the capacity configuration of off grid hydrogen production systems and improving the overall economic benefits of the system.