Search Results (143)

The aim of this study is to provide a comprehensive analysis of the outcome of two separate techno-economic studies that were conducted for the scaled-up and industrially relevant processes of a) synthetic natural gas (SNG) production from captured (cement-based) CO₂ and green-H₂ (via renewable-assisted electrolysis) and b) combined electricity and crude biofuel production through the integration of biomass pyrolysis, gasification, and solid oxide fuel cells. As was found, the SNG production process seems more feasible from an economic perspective as it can be comparable to current market values. Full article

The increase in power generation facilities from nonprogrammable renewable sources is posing several challenges for the management of electrical systems, due to phenomena such as congestion and reverse power flows. In mitigating these phenomena, Power-to-Gas plants can make an important contribution. In this paper, a linear optimisation study is presented for the sizing of a Power-to-Hydrogen plant consisting of a PEM electrolyser, a hydrogen storage system composed of multiple compressed hydrogen tanks, and a fuel cell for the eventual reconversion of hydrogen to electricity. The plant was sized with the objective of minimising reverse power flows in a medium-voltage distribution network characterised by a high presence of photovoltaic systems, considering economic aspects such as investment costs and the revenue obtainable from the sale of hydrogen and excess energy generated by the photovoltaic systems. The study also assessed the impact that the electrolysis plant has on the power grid in terms of power losses. The results obtained showed that by installing a 737 kW electrolyser, the annual reverse power flows are reduced by 81.61%, while also reducing losses in the transformer and feeders supplying the ring network in question by 17.32% and 29.25%, respectively, on the day with the highest reverse power flows. Full article

Approximately 20% of emissions from air travel are attributed to the auxiliary power units (APUs) carried in commercial aircraft. This paper proposes to reduce greenhouse gas emissions in international air transport by adopting proton-exchange membrane (PEM) fuel cells to replace APUs in commercial aircraft: we consider the design of three compressed hydrogen storage vessels made of 304 stainless steel, 6061-T6 aluminium, and Grade 5 (Ti-6Al-4V) titanium and capable of delivering 440 kW—enough for a PEM fuel cell for a Boeing 777. Complete structural analyses for pressures from 35 MPa to 70 MPa and wall thicknesses of 25, 50, 100, and 150 mm are used to determine the optimal material for aviation applications. Key factors such as deformation, safety factors, and Von Mises equivalent stress are evaluated to ensure structural integrity under a range of operating conditions. In addition, CO₂ emissions from a conventional 440 kW gas turbine APU and an equivalent PEM fuel cell are compared. This study provides insights into optimal material selection for compressed hydrogen storage vessels, emphasising safety, reliability, cost, and weight reduction. Ultimately, this research aims to facilitate the adoption of fuel cell technology in aviation, contributing to greenhouse emissions reduction and hence sustainable air transport. Full article

The proposed study incorporates a stochastic demand side management (SDSM) strategy for a self-sufficient residential system powered from a PV source with a hybrid battery–hydrogen storage system to minimize the total degradation costs associated with key components, including Li-io batteries, fuel cells, and PEM electrolyzers. The uncertainty in demand forecasting is addressed through a scenario-based generation to enhance the robustness and accuracy of the proposed method. Then, stochastic optimization was employed to determine the optimal operating schedules for deferable appliances and optimal water heater (WH) settings. The optimization problem was solved using a genetic algorithm (GA), which efficiently explores the solution space to determine the optimal operating schedules and reduce degradation costs. The proposed SDSM technique is validated through MATLAB 2020 simulations, demonstrating its effectiveness in reducing component degradation costs, minimizing load shedding, and reducing excess energy generation while maintaining user comfort. The simulation results indicate that the proposed method achieved total degradation cost reductions of 16.66% and 42.6% for typical summer and winter days, respectively, in addition to a reduction of the levelized cost of energy (LCOE) by about 22.5% compared to the average performance of 10,000 random operation scenarios. Full article

For PEM fuel cell operation, high-purity hydrogen gas containing only trace amounts of carbon monoxide is a prerequisite. The water–gas shift reaction (WGSR) is an industrially applied mature operation mode to convert CO with H₂O into CO₂ (making it easy to separate, if necessary) and H₂. Since the WGS reaction is an exothermic equilibrium reaction, low temperatures (below 200 °C) lead to full CO conversion. Thus, highly active ultra-low-temperature WGSR catalysts have to be applied. A homogeneous Ru SILP (supported ionic liquid phase) catalyst based on the precursor complex [Ru(CO)₃Cl₂]₂ has been identified to operate at such low temperature levels. However, in a hydrogen rich atmosphere, transition metal complexes are prone to form nanoparticles (NPs) when dissolved in ionic liquids (ILs). In this article, the behavior of an anionic SILP WGSR catalyst, i.e., [Ru(CO)₃Cl₃]⁻ dissolved in [BMMIM]Cl, in an H₂-rich CO environment is described. The data reveal that during the WGSR, Ru nanoparticles form in the catalyst when very low CO concentrations are reached. The Ru NPs formation has been confirmed by transmission electron microscopy imaging and X-ray diffraction (XRD). Full article

This study investigates the effects of anode and cathode inlet flow rates (ṁ) on the power performance of bipolar plates in a polymer electrolyte membrane fuel cell (PEMFC). The primary objective is to derive optimal flow rate conditions by comparatively analyzing concentration loss in the I−V curve and crossover phenomena at the anode, thereby establishing flow rates that prevent reactant depletion and water flooding. A single-cell computational model was constructed by assembling a commercial bipolar plate with a gas diffusion layer (GDL), catalyst layer (CL), and proton exchange membrane (PEM). The model simulates current density generated by electrochemical oxidation-reduction reactions. Hydrogen and oxygen were supplied at a 1:3 ratio under five proportional flow rate conditions: hydrogen (${\dot{m}}_{H_2}$ = 0.76–3.77 LPM) and oxygen (${\dot{m}}_{O_2}$ = 2.39–11.94 LPM). The Butler–Volmer equation was employed to model voltage drop due to overpotential, while numerical simulations incorporated contact resistivity, surface permeability, and porous media properties. Simulation results demonstrated a 24.40% increase in current density when raising ${\dot{m}}_{H_2}$ from 2.26 to 3.02 LPM and ${\dot{m}}_{O_2}$ from 7.17 to 9.56 LPM. Further increases to ${\dot{m}}_{H_2}$ = 3.77 LPM and ${\dot{m}}_{O_2}$ = 11.94 LPM yielded a 10.20% improvement, indicating that performance enhancements diminish beyond a critical threshold. Conversely, lower flow rates (${\dot{m}}_{H_2}$ = 0.76 and 1.5 LPM, ${\dot{m}}_{O_2}$ = 2.39 and 4.67 LPM) induced hydrogen-depleted regions, triggering crossover phenomena that exacerbated anode contamination and localized flooding. Full article

The decarbonization of offshore infrastructures is relevant to advancing global climate goals. This study presents a renewable-based energy system tailored for the Oceanic Platform of the Canary Islands (PLOCAN), designed to achieve full energy autonomy and eliminate greenhouse gas emissions. A hybrid configuration integrating photovoltaic panels, vertical-axis wind turbines, lithium-ion batteries, a proton exchange membrane (PEM) electrolyzer, and a PEM fuel cell was developed and evaluated through detailed resource assessment, system simulation, and techno-economic analysis under real offshore constraints. The results confirm that complete decarbonization is technically feasible, with a net present cost approximately 15% lower than the current diesel-based system and a total suppression of pollutant emissions. Although the transition entails a higher initial investment, the long-term economic and environmental gains are substantial. Offshore green hydrogen emerges as a key vector for achieving energy resilience and sustainability in isolated marine infrastructures, offering a replicable pathway towards fully decarbonized ocean platforms. Full article

The electrocatalytic hydrogenation (ECH) of biomass-derived phenolic compounds is a promising approach to the production of value-added chemicals and biofuels in a sustainable way under moderate reaction conditions. This study provides a comprehensive comparison of electrochemical and thermochemical hydrogenation processes, highlighting their relative advantages in terms of energy efficiency, product selectivity, and environmental impact. Several electrocatalysts (Pt, Pd, Rh, Ru), membranes (Nafion, Fumasep, GO-based PEMs), and reactor configurations are tested for the selective conversion of model compounds such as phenol, guaiacol, furfural, and levulinic acid. The contributions made by the electrode material, electrolyte composition, membrane nature, and reaction conditions are critically evaluated in relation to Faradaic efficiency, conversion rates, and product selectivity. The enhancement in the performance achieved by a new catalyst architecture is emphasized, such as MOF-based systems and bimetallic/trimetallic catalysts. In addition, a demonstration of graphite-based membranes and membrane-separated slurry reactors (SSERs) is provided, for enhanced ion transport and reaction control. The results illustrate the potential of using ECH as a low-carbon, scalable, and tunable method for the upgrading of biomass. This study offers valuable insights and guidelines for the rational design of next-generation electrocatalytic systems toward green chemical synthesis and emphasizes promising perspectives for the strategic development of electrochemical technologies in the pathway of a sustainable energy economy. Full article

A thermodynamic analysis of a compact hydrogen generation system for mobile fuel cell applications is presented. The system consists of a miniature autothermal steam reformer (ATR) and a water–gas shift (WGS) reactor, designed to produce hydrogen from hydrocarbon fuels for a 1 kW proton exchange membrane (PEM) fuel cell. Methane is used as the model fuel, and the study focuses on optimizing feed compositions and operational conditions to maximize hydrogen yield and purity. Feed compositions and operational conditions are optimized. In total, 0.7 Nm³ h⁻¹ H₂ is generated from 0.25 Nm³ h⁻¹ CH₄ with properly adjusted steam and air feeding. Issues with product purity and start-up procedures have been identified and discussed, along with feasible solutions. The system is suitable for remote and mobile applications. Full article

The turbocharging of hydrogen fuel cell systems (FCSs) has recently become a prominent research area, aiming to improve FCS efficiency to help decarbonise the energy and transport sectors. This work compares the performance of an electrically assisted variable-geometry turbocharger (VGT) with a fixed-geometry turbocharger (FGT) by optimising both the sizing of the components and their operating points, ensuring both designs are compared at their respective peak performance. A MATLAB-Simulink reduced-order model is used first to identify the most efficient components that match the fuel cell air path requirements. Maps representing the compressor and turbines are then evaluated in a 1D flow model to optimise cathode pressure and stoichiometry operating targets for net system efficiency, using an accelerated genetic algorithm (A-GA). Good agreement was observed between the two models’ trends with a less than 10.5% difference between their normalised e-motor power across all operating points. Under optimised conditions, the VGT showed a less than 0.25% increase in fuel cell system efficiency compared to the use of an FGT. However, a sensitivity study demonstrates significantly lower sensitivity when operating at non-ideal flows and pressures for the VGT when compared to the FGT, suggesting that VGTs may provide a higher level of tolerance under variable environmental conditions such as ambient temperature, humidity, and transient loading. Overall, it is concluded that the efficiency benefits of VGT are marginal, and therefore not necessarily significant enough to justify the additional cost and complexity that they introduce. Full article

Green hydrogen is increasingly recognized as a sustainable energy vector, offering significant potential for the industrial sector, buildings, and sustainable transport. As countries work to establish infrastructure for hydrogen production, transport, and energy storage, they face several challenges, including high costs, infrastructure complexity, security concerns, maintenance requirements, and the need for public acceptance. To explore these challenges and their environmental impact, this study proposes a hybrid sustainable infrastructure that integrates photovoltaic solar energy for the production and storage of green hydrogen, with PEMFC fuel cells and a hybrid Power-to-Electricity (PtE) and Power-to-Gas (PtG) configurations. The proposed system architecture is governed by an innovative energy optimization and management (EMS) algorithm, allowing forecasting, control, and supervision of various PV–hydrogen–Grid transfer scenarios. Additionally, comprehensive daily and seasonal simulations were performed to evaluate power sharing, energy transfer, hydrogen production, and storage capabilities. Dynamic performance assessments were conducted under different conditions of solar radiation, temperature, and load, demonstrating the system’s adaptability. The results indicate an overall efficiency of 62%, with greenhouse gas emissions reduced to 1% and a daily production of hydrogen of around 250 kg equivalent to 8350 KWh/day. Full article

The transition to clean energy has accelerated the pursuit of hydrogen as a sustainable fuel. Among various production methods, proton exchange membrane electrolysis cells (PEMECs) stand out due to their ability to generate ultra-pure hydrogen with efficiencies exceeding 80% and current densities reaching 2 A/cm². Their compact design and rapid response to dynamic energy inputs make them ideal for integration with renewable energy sources. This review provides a comprehensive assessment of PEMEC technology, covering key internal components, system configurations, and efficiency improvements. The role of catalyst optimization, membrane advancements, and electrode architectures in enhancing performance is critically analyzed. Additionally, we examine state-of-the-art numerical modelling, comparing zero-dimensional to three-dimensional simulations and single-phase to two-phase flow dynamics. The impact of oxygen evolution and bubble dynamics on mass transport and performance is highlighted. Recent studies indicate that optimized electrode architectures can enhance mass transport efficiency by up to 20%, significantly improving PEMEC operation. Advancements in two-phase flow simulations are crucial for capturing multiphase transport effects, such as phase separation, electrolyte transport, and membrane hydration. However, challenges persist, including high catalyst costs, durability concerns, and scalable system designs. To address these, this review explores non-precious metal catalysts, nanostructured membranes, and machine-learning-assisted simulations, which have demonstrated cost reductions of up to 50% while maintaining electrochemical performance. Future research should integrate experimental validation with computational modelling to improve predictive accuracy and real-world performance. Addressing system control strategies for stable PEMEC operation under variable renewable energy conditions is essential for large-scale deployment. This review serves as a roadmap for future research, guiding the development of more efficient, durable, and economically viable PEM electrolyzers for green hydrogen production. Full article

The power to weight ratio of power plants is an important consideration, especially in the design of Unmanned Aircraft System (UAS). In this paper, a UAS with an MTOW of 35.3 kg, equipped with a fuel cell as a prime power supply to provide electrical power to the propulsion system, is considered. A pressure vessel design that can estimate and determine the total size and weight of the combined power plant of a fuel cell stack with hydrogen and air/oxygen vessels and the propulsion system of the UAS for high-altitude operation is proposed. Two scenarios are adopted to determine the size and weight of the pressure vessels required to supply oxygen to the fuel cell stack. Different types of stainless-steel materials are used in the design of the pressure vessel in order to find an appropriate material that provides low size and weight advantages. Also, the design of a hydrogen pressure vessel and mass estimation are also considered. The estimated sizes and weights of the hydrogen and oxygen vessels of the power plant and propulsion system in this research offer a maximum of four hours of flying time for the UAS mission; this is based on a Horizon (H-1000) Proton Exchange Membrane (PEM) stack. Full article

Efficient hydrogen storage is critical for advancing hydrogen-based technologies. This study investigates the effects of pressure and surface area on hydrogen storage in three carbon-based materials: graphite, graphene oxide, and reduced graphene oxide. Hydrogen adsorption–desorption experiments under pressures ranging from 1 to 9 bar revealed nonlinear storage capacity responses, with optimal performance at around 5 bar. The specific surface area plays a pivotal role, with reduced graphene oxide and exhibiting a surface area of 70.31 m²/g, outperforming graphene oxide (33.75 m²/g) and graphite (7.27 m²/g). Reduced graphene oxide achieved the highest hydrogen storage capacity, with 768 sccm and a 3 wt.% increase over the other materials. In assessing proton-exchange fuel cell performance, this study found that increased hydrogen storage correlates with enhanced power density, with reduced graphene oxide reaching a maximum of 0.082 W/cm², compared to 0.071 W/cm² for graphite and 0.017 W/cm² for graphene oxide. However, desorption rates impose temporal constraints on fuel cell operation. These findings enhance our understanding of pressure–surface interactions and underscore the balance between hydrogen storage capacity, surface area, and practical performance in carbon-based materials, offering valuable insights for hydrogen storage and fuel cell applications. Full article

In the development of more electric aircraft, hydrogen powered fuel cells are one possible solution to progress towards emission reductions in aviation. Currently, there are numerous concepts for integrating fuel cells into future aircraft. The goal of this work was to develop a dynamic fuel cell model for simulations of the powertrain. The Modelica language together with the ThermoFluidStream (TFS) library from the German Aerospace Center (DLR) provided a suitable framework. The fuel cell model takes into account the electrochemical as well as thermodynamic behavior. Hence, the proposed multi-physics model allows simulating the whole fuel cell system, from the hydrogen tank to the electric grid. Under certain simplifications, this enables performing mission simulations of the complete powertrain of future aircraft. As such, polymer electrolyte membrane (PEM) fuel cells and solid oxide fuel cells (SOFC) were considered. The fuel cell models are checked for plausibility in a simple test case against data from the literature. Furthermore, two setups of possible applications are introduced: one for each fuel cell type, which come from two projects. The preliminary control systems of these architectures are presented. Afterwards, the first results of the fuel cell systems are discussed. These results show that the models ran robustly in various environments and operational states. They provided the desired accuracy to predict the behavior of a fuel cell, while maintaining low CPU times and being capable of enabling real-time simulations in the future. Full article