Applications & Pathways

This paper focuses on the potential use of ammonia as a carbon-free fuel and covers recent advances in the development of ammonia combustion technology and its underlying chemistry. Fulfilling the COP21 Paris Agreement requires the de-carbonization of energy generation through utilization of carbon-neutral and overall carbon-free fuels produced from renewable sources. Hydrogen is one of such fuels which is a potential energy carrier for reducing greenhouse-gas emissions. However its shipment for long distances and storage for long times present challenges. Ammonia on the other hand comprises 17.8% of hydrogen by mass and can be produced from renewable hydrogen and nitrogen separated from air. Furthermore thermal properties of ammonia are similar to those of propane in terms of boiling temperature and condensation pressure making it attractive as a hydrogen and energy carrier. Ammonia has been produced and utilized for the past 100 years as a fertilizer chemical raw material and refrigerant. Ammonia can be used as a fuel but there are several challenges in ammonia combustion such as low flammability high NOx emission and low radiation intensity. Overcoming these challenges requires further research into ammonia flame dynamics and chemistry. This paper discusses recent successful applications of ammonia fuel in gas turbines co-fired with pulverize coal and in industrial furnaces. These applications have been implemented under the Japanese ‘Cross-ministerial Strategic Innovation Promotion Program (SIP): Energy Carriers’. In addition fundamental aspects of ammonia combustion are discussed including characteristics of laminar premixed flames counterflow twin-flames and turbulent premixed flames stabilized by a nozzle burner at high pressure. Furthermore this paper discusses details of the chemistry of ammonia combustion related to NOx production processes for reducing NOx and validation of several ammonia oxidation kinetics models. Finally LES results for a gas-turbine-like swirl-burner are presented for the purpose of developing low-NOx single-fuelled ammonia gas turbine combustors.

In the last few decades the problem of pollution resulting from human activities has pushed research toward zero or net-zero carbon solutions for transportation. The main objective of this paper is to perform a preliminary performance assessment of the use of hydrogen in conventional turbine engines for aeronautical applications. A 0-D dynamic model of the Allison 250 C-18 turboshaft engine was designed and validated using conventional aviation fuel (kerosene Jet A-1). A dedicated experimental campaign covering the whole engine operating range was conducted to obtain the thermodynamic data for the main engine components: the compressor lateral ducts combustion chamber high- and low-pressure turbines and exhaust nozzle. A theoretical chemical combustion model based on the NASA-CEA database was used to account for the energy conversion process in the combustor and to obtain quantitative feedback from the model in terms of fuel consumption. Once the engine and the turbomachinery of the engine were characterized the work focused on designing a 0-D dynamic engine model based on the engine’s characteristics and the experimental data using the MATLAB/Simulink environment which is capable of replicating the real engine behavior. Then the 0-D dynamic model was validated by the acquired data and used to predict the engine’s performance with a different throttle profile (close to realistic request profiles during flight). Finally the 0-D dynamic engine model was used to predict the performance of the engine using hydrogen as the input of the theoretical combustion model. The outputs of simulations running conventional kerosene Jet A-1 and hydrogen using different throttle profiles were compared showing up to a 64% reduction in fuel mass flow rate and a 3% increase in thermal efficiency using hydrogen in flight-like conditions. The results confirm the potential of hydrogen as a suitable alternative fuel for small turbine engines and aircraft.

This study investigates the feasibility of using green hydrogen technology produced via Proton Exchange Membrane (PEM) electrolysis powered by a 200 MW wind farm for a commercial Greenhouse in Ontario Canada. Nine different scenarios are analyzed exploring various approaches to hydrogen (H2) production transportation and utilization for electricity generation. The aim is to transition from using natural gas to using varying combinations of H2 and natural gas that include 10 % 20 % and 100 % of H2 with 90 % 80 % and 0 % of natural gas to generate 13.3 MW from Combined Heat and Power (CHP) engines. The techno-economic parameters considered for the study are the levelized cost of hydrogen (LCOH) payback period (PBT) internal rate of return (IRR) and discounted payback period (DPB). The study found that a 10 % H2-Natural Gas blend using existing wired or transmission line (W-10H2) with 5 days of storage capacity and 2190 h of CHP operation per year had the lowest cost with a LCOH of USD 3.69/kg. However 100 % of H2 using existing wired or transmission line (W-100H2) with the same storage and operation hours revealed better PBT IRR and DPB with values of 6.205 years 15.16 % and 7.993 years respectively. It was found impractical to build a new pipeline or transport H2 via tube trailer from wind farm site to greenhouse. A sensitivity analysis was also conducted to understand what factors affect the LCOH value the most.

This paper investigates innovative solutions to enhance the performance and lifespan of standalone photovoltaic (PV)-based microgrids with a particular emphasis on off-grid communities. A major challenge in these systems is the limited lifespan of batteries. To overcome this issue researchers have created hybrid energy storage systems (HESS) along with advanced power management strategies. This study introduces innovative multi-level HESS approaches and a related energy management strategy designed to alleviate the charge/discharge stress on batteries. Comprehensive Matlab Simulink models of various HESS topologies within standalone PV microgrids are utilized to evaluate system performance under diverse weather conditions and load profiles for rural site. The findings reveal that the proposed HESS significantly extends battery life expectancy compared to existing solutions. Furthermore the paper presents a novel energy management strategy based on the Reduced Fractional Gradient Descent (RFGD) algorithm optimization tailored for hybrid systems that include photovoltaic fuel cell battery and supercapacitor components. This strategy aims to minimize hydrogen consumption of Fuel Cells (FCs) thereby supporting the production of green ammonia for local industrial use. The RFGD algorithm is selected for its minimal user-defined parameters and high convergence efficiency. The proposed method is compared with other algorithms such as the Lyrebird Optimization Algorithm (LOA) and Osprey Optimization Algorithm (OOA). The RFGD algorithm exhibits superior accuracy in optimizing energy management achieving a 15% reduction in hydrogen consumption. Its efficiency is evident from the reduced computational time compared to conventional algorithms. Although minor losses in computational resources were observed they were substantially lower than those associated with traditional optimization techniques. Overall the RFGD algorithm offers a robust and efficient solution for enhancing the performance of hybrid energy systems.

This study addresses the optimization of urban integrated energy systems (UIESs) under uncertainty in peer-to-peer (P2P) electricity trading by introducing a two-stage robust optimization strategy. The strategy includes a UIES model with a photovoltaic (PV)–green roof hydrogen storage and cascading cold/heat energy subsystems. The first stage optimizes energy trading volume to maximize social welfare while the second stage maximizes operational profit considering uncertainties in PV generation and power prices. The Nested Column and Constraint Generation (NC&CG) algorithm enhances privacy and solution precision. Case studies with three UIESs show that the model improves economic performance energy efficiency and sustainability increasing profits by 1.5% over non-P2P scenarios. Adjusting the robustness and deviation factors significantly impacts P2P transaction volumes and profits allowing system operators to optimize profits and make risk-aligned decisions.

The transition from traditional aviation fuels to low-emission alternatives such as hydrogen is a crucial step towards a sustainable future for aviation. Conventional jet fuels substantially contribute to greenhouse gas emissions and climate change. Hydrogen fuel especially "green" hydrogen offers great potential for achieving full sustainability in aviation. Hybrid/electric/fuel cell technologies may be used for shorter flights while longrange aircraft are more likely to combust hydrogen in gas turbines. Liquid hydrogen is necessary to minimize storage tank weight but the required fuel systems are at a low technology readiness level and differ significantly from Jet A-1 systems in architecture operation and performance. This paper provides an in-depth review covering the development of liquid hydrogen fuel system design concepts for gas turbines since the 1950s compares insights from key projects such as NASA studies and ENABLEH2 alongside an analysis of recent publications and patent applications and identifies the technological advancements required for achieving zeroemission targets through hydrogen-fuelled propulsion.

This paper analyzes the hydrogen refueling process for heavy-duty vehicles according to the SAE J2601/2 protocol. Attention is paid to two key aspects of the protocol that affect the refueling process: treatment of the storage system from a thermodynamic and geometric point of view and the maximum deliverable flow rate of the station in the refueling process. The effect of the ratio of the inner diameter to the inner length of the total volume on the refueling process was then analyzed and it was shown how far the new approach results deviate from the results obtained by applying the SAE protocol. A total supply of 28 kg was simulated but with three different configurations: 14*2 kg tanks 7*4 kg tanks and 4*7 kg tanks. When analyzing the effect of varying the ratio of inner diameter to inner length it was noted that in the most conservative case there is an overestimation in terms of final temperature for the three configurations of about: 2.1 ◦C 1.4 ◦C and 1.1 ◦C respectively. This aspect has a significant impact on the refueling time which could be reduced by about 9.9% in the first case and about 7.1% and 5.4% in the other two. In addition refueling using the multi-tank approach was simulated for some case studies assimilated to heavy vehicles currently on the market in terms of the amount of hydrogen stored. These refuelings were carried out with stations capable of delivering a maximum flow rate of 120 g/s 180 g/s and 240 g/s. It is inferred that increasing the flow rate from 120 g/s to 180 g/s results in time savings for the three cases of: 35% 34% and 37%. On the other hand running up to 240 g/s results in time savings of: 54% 52% and 55%.

The decarbonization of sectors such as aviation maritime transport and heavy-duty mobility—where direct electrification is not yet feasible—requires alternative fuels with high energy density and compatibility with existing infrastructure. This review investigates the potential of liquid synthetic fuels known as liquid electrofuels (or e-fuels) to replace fossil fuels in these hard-to-abate sectors. The objective is to provide a comprehensive integrative assessment of liquid e-fuel development by analyzing production pathways feedstock demands regulatory frameworks and industrial implementation trends. The study reviews three major production processes—Fischer–Tropsch synthesis methanol synthesis and the Haber–Bosch process—used to produce six key synthetic fuels: e-kerosene e-diesel e-methanol e-dimethyl ether e-gasoline and e-ammonia. The methodology includes a systematic review of literature life cycle assessments for water and energy demand and analysis of over 30 large-scale projects worldwide in terms of plant capacity (10–200 MW) production volume capital investment and technology readiness level. Results show that process efficiencies range from 59 % to 89 % with current production costs for synthetic kerosene and methanol varying between 1200–4200 €/ton depending on the pathway and technology maturity. The study finds that polymer electrolyte membrane electrolysis and industrial point-source carbon dioxide capture are the most prevalent technologies among operational plants. Regulatory complexity high capital expenditure and the lack of harmonized sustainability criteria remain key barriers to commercial scaling. This review advances the scientific literature by presenting a novel multi-dimensional framework that connects technical environmental and policy considerations offering a strategic roadmap for accelerating the global deployment of liquid synthetic fuels.

To further optimize the low-carbon economy of the integrated energy system (IES) this paper establishes a two-stage P2G hydrogen-coupled electricity–heat–hydrogen–gas IES with carbon capture (CCS). First this paper refines the two stages of P2G and introduces a hydrogen fuel cell (HFC) with a hydrogen storage device to fully utilize the hydrogen energy in the first stage of power-to-gas (P2G). Then the ladder carbon trading mechanism is considered and CCS is introduced to further reduce the system’s carbon emissions while coupling with P2G. Finally the adjustable thermoelectric ratio characteristics of the combined heat and power unit (CHP) and HFC are considered to improve the energy utilization efficiency of the system and to reduce the system operating costs. This paper set up arithmetic examples to analyze from several perspectives and the results show that the introduction of CCS can reduce carbon emissions by 41.83%. In the CCS-containing case refining the P2G two-stage and coupling it with HFC and hydrogen storage can lead to a 30% reduction in carbon emissions and a 61% reduction in wind abandonment costs; consideration of CHP and HFC adjustable thermoelectric ratios can result in a 16% reduction in purchased energy costs.

One of the most important problems in the widespread use of electric vehicles is the lack of charging infrastructure. Especially in tourist areas where historical buildings are located the installation of a power grid for the installation of electric vehicle charging stations or generating electrical energy by installing renewable energy production systems such as large-sized PV (photovoltaic) and wind turbines poses a problem because it causes the deterioration of the historical texture. Considering the need for renewable energy sources in the transportation sector our aim in this study is to model an electric vehicle charging station using PVPS (photovoltaic power system) and FC (fuel cell) power systems by using irradiation and temperature data from historical regions. This designed charging station model performs electric vehicle charging meeting the energy demand of a house and hydrogen production by feeding the electrolyzer with the surplus energy from producing electrical energy with the PVPS during the daytime. At night when there is no solar radiation electric vehicle charging and residential energy demand are met with an FC power system. One of the most important advantages of this system is the use of hydrogen storage instead of a battery system for energy storage and the conversion of hydrogen into electrical energy with an FC. Unlike other studies in our study fossil energy sources such as diesel generators are not included for the stable operation of the system. The system in this study may need hydrogen refueling in unfavorable climatic conditions and the energy storage capacity is limited by the hydrogen fuel tank capacity.