Publications

Background: Synthetic fuels based on renewable hydrogen and CO2 are a currently highly discussed piece of the puzzle to defossilize the transport sector. In this regard CO2 can play a positive role in shaping a sustainable future. Large potentials are available as a product of biogas production however occurring in small scales and in thin spatial distributions. This work aims to evaluate suitable synthetic fuel products to be produced at farm sites.<br/>Methods: A thermodynamic analysis to assess the energetic efficiency of synthesis pathways and a qualitative assessment of product handling issues is carried out.<br/>Results: Regarding the technical and safety-related advantages in storage liquid products are the superior option for fuel production at decentralized sites. Due to the economy of scale multi-stage synthesis processes lose economic performance with rising complexity. A method was shown which covers a principle sketch of all necessary reaction separation steps and all compression and heat exchanger units. The figures showed that methanol and butanol are the most suitable candidates in contrast to OME3-5 for implementation in existing transportation and fuel systems. These results were underpin by a Gibbs energy analysis.<br/>Conclusions: As long as safety regulations are met and the farm can guarantee safe storage and transport farm-site production for all intermediates can be realized technically. Ultimately this work points out that the process must be kept as simple as possible favoring methanol production at farm site and its further processing to more complicated fuels in large units for several fuel pathways.

Hydrogen (H2 ) is the most abundant element in the universe and it is also a neutral energy carrier meaning the environmental effects of using it are strictly related to the effects of creating the means of producing of that amount of Hydrogen. So far the H2 generation by water electrolysis research field did not manage to break the efficiency barrier in order to consider H2 production as a technology that sustains financially its self-development. However given the complexity of this technology and the overall environmental impacts an up-to-date research and development status review is critical. Thus this study aims to identify the main trends achievements and research directions of the H2 generation using pure and alkaline water electrolysis providing a review of the state of the art in the specific literature. Methods: In order to deliver this a Systematic Literature Review was carried out using PRISMA methodology highlighting the research trends and results in peer review publish articles over more than two years (2020–2022). Findings: This review identifies niches and actual status of the H2 generation by water and alkaline water electrolysis and points out in numbers the boundaries of the 2020–2022 timeline research.

Diesel generators are currently used as an off-grid solution for backup power but this causes CO2 and GHG emissions noise emissions and the negative effects of the volatile diesel market influencing operating costs. Green hydrogen production by means of water electrolysis has been proposed as a feasible solution to fill the gaps between demand and production the main handicaps of using exclusively renewable energy in isolated applications. This manuscript presents a business case of an off-grid hydrogen production by electrolysis applied to the electrification of isolated sites. This study is part of the European Ely4off project (n◦ 700359). Under certain techno-economic hypothesis four different system configurations supplied exclusively by photovoltaic are compared to find the optimal Levelized Cost of Electricity (LCoE): photovoltaic-batteries photovoltaic-hydrogen-batteries photovoltaic-diesel generator and diesel generator; the influence of the location and the impact of different consumptions profiles is explored. Several simulations developed through specific modeling software are carried out and discussed. The main finding is that diesel-based systems still allow lower costs than any other solution although hydrogen-based solutions can compete with other technologies under certain conditions.

Equinor has in recent years focused on low carbon technologies in addition to conventional oil & gas technologies. Clear strategic directions have been set to demonstrate Equinor’s commitment to longterm value creation that supports the Paris Agreement. This includes acceleration of decarbonization by establishing a well-functioning market for carbon capture transport and storage (CCS) as well as development of competitive hydrogen-based value chains and solutions. The specific properties of hydrogen must be taken into account in order to ensure safe design and operation of hydrogen systems as these properties differ substantially from those of natural gas and other conventional oil & gas products. Development projects need to consider and mitigate the increased possibility of high explosion pressures or detonation if hydrogen releases accumulate in enclosed or congested areas. On the other hand hydrogen’s buoyant properties can be exploited by locating potential leak points in the open to avoid gas accumulation thereby reducing the explosion risk. The purpose of this paper is to introduce Equinor’s hydrogen-based value chain projects and present our approach to ensure safe and effective designs. Safety strategies constitute the basis for Equinor’s safety and risk management. The safety strategies describe the connection between the hazards and risk profiles on one hand and the safety barrier elements and their needed performance on the other as input to safe design. The safety strategies also form the basis for safe operation. Measures to control the risk through practical designs follow from these strategies.

Micro-mobility plays an increasingly important role in the current energy transition thanks to its low energy consumption and reduced contribution to urban congestion. In this scenario fuel cell hybrid electric vehicles have several advantages over state-of-the-art battery electric vehicles such as increased driving ranges and reduced recharge times. In this paper we study the conversion of a commercial electric moped (Askoll eS3 ®) into a fuel cell hybrid electric vehicle by finding the optimal design of the components through an optimization methodology based on backward dynamic programming. This optimal design and operation strategy can also be implemented with a rulesbased approach. The results show that a system composed of a 1 kW proton exchange membrane fuel cell a 2000 Sl metal hydride hydrogen tank and a 240 Wh buffer battery can cover the same driving range as the batteries in an electric moped (119 km). Such a hybrid system occupies considerably less volume (almost 40 L) and has a negligibly higher mass. The free volume can be used to extend the driving range up to almost three times the nominal value. Moreover by using a high-pressure composite tank it is possible to increase the mass energy density of the onboard energy storage (although compression can require up to 10% of the hydrogen’s chemical energy). The fuel cell hybrid electric vehicle can be recharged with green hydrogen that is locally produced. In detail we analyze a residential scenario and a shared mobility scenario in the small Italian city of Viterbo.

The main objective of this paper is to select the optimal configuration of a ship’s power system considering the use of fuel cells and batteries that would achieve the lowest CO2 emissions also taking into consideration the number of battery cycles. The ship analyzed in this work is a Platform Supply Vessel (PSV) used to support oil and gas offshore platforms transporting goods equipment and personnel. The proposed scheme considers the ship’s retrofitting. The ship’s original main generators are maintained and the fuel cell and batteries are installed as complementary sources. Moreover a sensitivity analysis is pursued on the ship’s demand curve. The simulations used to calculate the CO2 emissions for each of the new hybrid configurations were developed using HOMER software. The proposed solutions are auxiliary generators three types of batteries and a protonexchange membrane fuel cell (PEMFC) with different sizes of hydrogen tanks. The PEMFC and batteries were sized as containerized solutions and the sizing of the auxiliary engines was based on previous works. Each configuration consists of a combination of these solutions. The selection of the best configuration is one contribution of this paper. The new configurations are classified according to the reduction of CO2 emitted in comparison to the original system. For different demand levels the results indicate that the configuration classification may vary. Another valuable contribution of this work is the sizing of the battery and hydrogen storage systems. They were installed in 20 ft containers since the installation of batteries fuel cells and hydrogen tanks in containers is widely used for ship retrofit. As a result the most significant reduction of CO2 emissions is 10.69%. This is achieved when the configuration includes main generators auxiliary generators a 3119 kW lithium nickel manganese cobalt (LNMC) battery a 250 kW PEMFC and 581 kg of stored hydrogen.

The global transition to a clean and sustainable energy infrastructure does not stop at aviation. The European Commission defined a set of environmental goals for the “Flight Path 2050”: 75% CO2 reduction 90% NOx reduction and 65% perceived noise reduction. Hydrogen as an energy carrier fulfills these needs while it would also offer a tenable and flexible solution for intermittent large-scale energy storage for renewable energy networks. If hydrogen is used as an energy carrier there is no better device than a fuel cell to convert its stored chemical energy. In order to design fuel cell systems for passenger aircraft it is necessary to specify the requirements that the system has to fulfill. In this paper a statistical approach to analyze these requirements is presented which accounts for variations in the flight mission profile. Starting from a subset of flight data within the desired class (e.g. mid-range inter-European flights) a stochastic model of the random mission profile is inferred. This model allows for subsequent predictions under uncertainty as part of the aircraft design process. By using Monte Carlo-based sampling of flight mission profiles the range of necessary component sizes as well as optimal degrees of hybridization with a battery is explored and design options are evaluated. Furthermore Monte Carlo-based sensitivity analysis of performance parameters explores the potential of future technological developments. Results suggest that the improvement of the specific power of the fuel cell is the deciding factor for lowering the energy system mass. The specific energy of the battery has a low influence but acts in conjunction with the specific power of the fuel cell.

With the combustor burning hydrogen as well as the strongly coupled fuel and cooling system the configuration of a hydrogen-fueled aero engine is more complex than that of a conventional aero engine. The performance and especially the dynamic behavior of a hydrogen-fueled aero engine need to be fully understood for engine system design and optimization. In this paper both the transient modeling and performance analysis of hydrogen-fueled engines are presented. Firstly the models specific to the hydrogen-fueled engine components and systems including the hydrogen-fueled combustor the steam injection system a simplified model for a quick NOx emission assessment and the heat exchangers are developed and then integrated to a conventional engine models. The simulations with both Simulink and Speedgoat-based hardware in the loop system are carried out. Secondly the performance analysis is performed for a typical turbofan engine configuration CF6 and for the two hydrogen-fueled engine configurations ENABLEH2 and HySIITE which are currently under research and development by the European Union and Pratt & Whitney respectively. At last the simulation results demonstrate that the developed transient models can effectively reflect the characteristics of hydrogen burning heat exchanging and NOx emission for hydrogen-fueled engines. In most cases the hydrogen-fueled engines show lower specific fuel consumption lower turbine entry temperature and less NOx emissions compared with conventional engines. For example at max thrust state the advanced hydrogen-fueled engine can reduce the parameters mentioned above by about 68.5% 3.7% and 12.7% respectively (a mean value of two configurations).

Hydrogen is of great significance for replacing fossil fuels and reducing carbon dioxide emissions. The application of hydrogen mixing with natural gas in gas network transportation not only improves the utilization rate of hydrogen energy but also reduces the cost of large-scale updating household or commercial appliance. This paper investigates the necessity of a gas mixing device for adding hydrogen to existing natural gas pipelines in the industrial gas network. A three-dimensional helical static mixer model is developed to simulate the mixing behavior of the gas mixture. In addition the model is validated with experimental results. Parametric studies are performed to investigate the effect of mixer on the mixing performance including the coefficient of variation (COV) and pressure loss. The research results show that based on the the optimum number of mixing units is three. The arrangement of the torsion angle of the mixing unit has a greater impact on the COV. When the torsion angle θ = 120◦ the COV has a minimum value of 0.66% and when the torsion angle θ = 60◦ the COV has a maximum value of 8.54%. The distance of the mixing unit has little effect on the pressure loss of the mixed gas but has a greater impact on the COV. Consecutive arrangement of the mixing units (Case A) is the best solution. Increasing the distance of the mixing unit is not effective for the gas mixing effect. Last but not least the gas mixer is optimized to improve the mixing performance.

This work demonstrates the need for accurate thermodynamic models to reliably quantify changes in the thermophysical properties of natural gas when blended with hydrogen. For this purpose a systematic evaluation was carried out on the predictive accuracy of three well-known models the Peng−Robinson equation of state (EoS) the multiparameter empirical GERG-2008 model and the molecular-based polar softSAFT EoS in describing the thermodynamic behavior of mixtures of hydrogen with commonly found components in natural gas. Deviations between the calculated properties and experimental data for phase equilibria critical loci second-order derivative properties and viscosities are used to determine the accuracy of the models with polar soft-SAFT performing either equally or better than the other two examined models. The evaluation for the effect of H2 content on the properties of methane simulated as natural gas at conditions for transportation reveals higher changes in blend density and speed of sound with increasing H2 content within 5% change per 5 mol % H2 added while viscosity is the least affected property changing by 0.4% for every 5 mol % H2.