Applications & Pathways

The global climate crisis necessitates the urgent implementation of sustainable practices and carbon emission reduction strategies across all sectors. Transport as a major contributor to greenhouse gas emissions requires transitional technologies to bridge the gap between fossil fuel dependency and renewable energy systems. Natural gas recognised as the cleanest fossil-derived fuel with approximately half the CO2 emissions of coal and 75% of oil presents a potential transitional solution through Natural Gas Vehicles (NGVs). This manuscript presents several distinctive contributions that advance the understanding of Natural Gas Vehicles within the contemporary energy transition landscape while synthesising updated emission performance data. Specifically the feasibility and sustainability of NGVs are investigated within the energy transition framework by systematically incorporating recent technological developments and environmental economic and infrastructure considerations in comparison to conventional vehicles (diesel and petrol) and unconventional alternatives (electric and hydrogen-fuelled). The analysis reveals that NGVs can reduce CO2 emissions by approximately 25% compared to petrol vehicles on a well-to-wheel basis with significant reductions in NOx and particulate matter. However these environmental benefits depend heavily on the source and type of natural gas used (CNG or LNG) while economic viability hinges largely on governmental policies and infrastructure development. The findings suggest that NGVs can serve as an effective transitional technology in the transport sector’s sustainability pathway particularly in regions with established natural gas infrastructure but require supportive policy frameworks to overcome implementation barriers.

Green hydrogen offers a sustainable alternative source of fossil fuels to compensate for the increasing energy demand. This study addresses the increasing energy demand and the need for sustainable alternatives to fossil fuels by examining the production of green hydrogen in an existing Egyptian oil refinery. The primary objective is to evaluate the technical economic and environmental outcomes of integrating green hydrogen to increase the refinery’s hydro processing capacity. The methodology involves the use of water electrolysis powered exclusively by renewable electricity from a 60 MW solar installation with a panel surface area of 660000 m². A simulation model of alkaline electrolyzer skids was developed to assess the production of an additional 1260 kg/h of hydrogen representing a 15% increase over the existing Steam Methane Reforming (SMR) capacity. The environmental impact was quantified by calculating the reduction in CO₂ and equivalent emissions while an economic forecasting analysis was conducted to project the production costs of green versus grey hydrogen. The main results indicate that the integration is technically feasible and environmentally beneficial with a significant reduction in the refinery’s carbon footprint. Economically the study projects that by 2028 the production cost of green hydrogen will fall to 1.56 USD/kg H₂ becoming more cost-effective than grey hydrogen at 1.65 USD/kg H₂ largely due to the influence of carbon taxes and credits. This study underscores the transformative potential of green hydrogen in decarbonizing industrial processes offering a viable pathway for refineries to contribute to global climate change mitigation efforts.

The reliability and sustainability of multi-energy networks are increasingly critical in addressing modern energy demands and environmental concerns. Hydrogen-based hybrid energy systems can mitigate the challenges of renewable energy utilization such as intermittency grid stability and energy storage by integrating hydrogen generation and electricity storage from renewable sources such as solar and wind. Therefore this review offers a comprehensive evaluation of the environmental economic and technological aspects of green hydrogen-based hybrid energy systems particularly highlighting improvements in terms of the economics of fuel cell and electrolysis procedures. It also highlights new approaches such as hybrid energy management strategies and power-to-gas (PtG) conversion to enhance the system’s dependability and resilience. Analyzing the role of green hydrogen-based hybrid energy systems in supporting global climate goals and improving energy security underscores their high potential to make a significant contribution to carbon-neutral energy networks and provide policymakers with useful recommendations for developing guidelines. In addition the social aspect of hydrogen systems like energy equity and community engagement towards a hydrogen-based society provides reasons for the continued development of next-generation energy systems.

Hydrogen-powered aircraft constitute a transformative innovation in aviation motivated by the imperative for sustainable and environmentally friendly transportation solutions. This paper aims to concentrate on the design of hydrogen powertrains employing a system approach to propose representative design models for distribution and propulsion systems. Initially the requirements for powertrain design are formalized and a usecase-driven analysis is conducted to determine the functional and physical architectures. Subsequently for each component pertinent to preliminary design an analytical model is proposed for multidisciplinary analysis and optimization for powertrain sizing. A doublewall pipe model incorporating foam and vacuum multi-layer insulation was developed. The internal and outer pipes sizing were performed in accordance with standards for hydrogen piping design. Valves sizing is also considered in the present study following current standards and using data available in the literature. Furthermore models for booster pumps to compensate pressure drop and high-pressure pumps to elevate pressure at the combustion chamber entrance are proposed. Heat exchanger and evaporator models are also included and connected to a burning hydrogen engine in the sizing process. An optimal liner pipe diameter was identified which minimizes distribution systems weight. We also expect a reduction in engine length and weight while maintaining equivalent thrust.

Driven by the global energy transition and the dual carbon goals developing low-carbon and zero-carbon alternative fuels has become a core issue for sustainable development in the internal combustion engine sector. Ammonia is a promising zero-carbon fuel with broad application prospects. However its inherent combustion characteristics including slow flame propagation high ignition energy and narrow flammable range limit its use in internal combustion engines necessitating the addition of auxiliary fuels. To address this issue this paper proposes a composite injection technology combining “ammonia duct injection + hydrogen cylinder direct injection.” This technology utilizes highly reactive hydrogen to promote ammonia combustion compensating for ammonia’s shortcomings and enabling efficient and smooth engine operation. This study based on bench testing investigated the effects of hydrogen direct injection timing (180 170 160 150 140◦ 130 120 ◦CA BTDC) hydrogen direct injection pressure (4 5 6 7 8 MPa) on the combustion and emissions of the ammonia–hydrogen engine. Under hydrogen direct injection timing and hydrogen direct injection pressure conditions the hydrogen mixture ratios are 10% 20% 30% 40% and 50% respectively. Test results indicate that hydrogen injection timing that is too early or too late prevents the formation of an optimal hydrogen layered state within the cylinder leading to prolonged flame development period and CA10-90. The peak HRR also exhibits a trend of first increasing and then decreasing as the hydrogen direct injection timing is delayed. Increasing the hydrogen direct injection pressure to 8 MPa enhances the initial kinetic energy of the hydrogen jet intensifies the gas flow within the cylinder and shortens the CA0-10 and CA10-90 respectively. Under five different hydrogen direct injection ratios the CA10- 90 is shortened by 9.71% 11.44% 13.29% 9.09% and 13.42% respectively improving the combustion stability of the ammonia–hydrogen engine.

Dual-fuel engines are a way of transitioning the marine sector to carbon-neutral fuels like hydrogen and methanol. For the development of these engines accurate simulation of the combustion process is needed for which calculating the pilot’s ignition delay is essential. The present work investigates novel methodologies for calculating this. This involves the use of chemical kinetic schemes to compute the ignition delay for various operating conditions. Machine learning techniques are used to train models on these data sets. A neural network model is then implemented in a dual-fuel combustion model to calculate the ignition delay time and is compared using a lookup table or a correlation. The numerical results are compared with experimental data from a dual-fuel medium-speed marine engine operating with hydrogen or methanol from which the method with best accuracy and fastest calculation is selected.

Renewable energy systems are at the core of global efforts to reduce greenhouse gas (GHG) emissions and to combat climate change. Focusing on the role of energy storage in enhancing dependability and efficiency this paper investigates the design and optimization of a completely sustainable hybrid energy system. Furthermore hybrid storage systems have been used to evaluate their viability and cost-benefits. Examined under a 100% renewable energy microgrid framework three setup configurations are as follows: (1) photovoltaic (PV) and Battery Storage System (BSS) (2) Hybrid PV/Wind Turbine (WT)/BSS and (3) Integrated PV/WT/BSS/Electrolyzer/ Hydrogen Tank/Fuel Cell (FC). Using its geographical solar irradiance and wind speed data this paper inspires on an industrial community in Neom Saudi Arabia. HOMER software evaluates technical and economic aspects net present cost (NPC) levelized cost of energy (COE) and operating costs. The results indicate that the PV/ BSS configuration offers the most sustainable solution with a net present cost (NPC) of $2.42M and a levelized cost of electricity (LCOE) of $0.112/kWh achieving zero emissions. However it has lower reliability as validated by the provided LPSP. In contrast the PV/WT/BSS/Elec/FC system with a higher NPC of $2.30M and LCOE of $0.106/kWh provides improved energy dependability. The PV/WT/BSS system with an NPC of $2.11M and LCOE of $0.0968/kWh offers a slightly lower cost but does not provide the same level of reliability. The surplus energy has been implemented for hydrogen production. A sensitivity analysis was performed to evaluate the impact of uncertainties in renewable resource availability and economic parameters. The results demonstrate significant variability in system performance across different scenarios

Electricity in rural Alaska is provided by more than 200 standalone microgrid systems powered predominantly by diesel generators. Incorporating renewable energy generation and storage to these systems can reduce their reliance on costly imported fuel and improve sustainability; however uncertainty remains about optimal grid architectures to minimize cost including how and when to incorporate long-duration energy storage. This study implements a novel multi-pronged approach to assess the techno-economic feasibility of future energy pathways in the community of Kotzebue which has already successfully deployed solar photovoltaics wind turbines and battery storage systems. Using real community load resource and generation data we develop a series of comparison models using the HOMER Pro software tool to evaluate microgrid architectures to meet over 90% of the annual community electricity demand with renewable generation considering both battery and hydrogen energy storage. We find that near-term planned capacity expansions in the community could enable over 50% renewable generation and reduce the total cost of energy. Additional build-outs to reach 75% renewable generation are shown to be competitive with current costs but further capacity expansion is not currently economical. We additionally include a cost sensitivity analysis and a storage capacity sizing assessment that suggest hydrogen storage may be economically viable if battery costs increase but large-scale seasonal storage via hydrogen is currently unlikely to be cost-effective nor practical for the region considered. While these findings are based on data and community priorities in Kotzebue we expect this approach to be relevant to many communities in the Arctic and Sub-Arctic regions working to improve energy reliability sustainability and security.

Heavy-duty fuel cell trucks are a promising approach to reduce the CO2 emissions of logistic fleets. Due to their higher powertrain energy density in comparison to battery-electric trucks they are especially suited for long-haul applications while transporting high payloads. Despite these great advantages the fleet integration of such vehicles is made difficult due to high costs and limited performance in thermally critical environmental conditions. These challenges are addressed in the European Union (EU) funded project ESCALATE which aims to demonstrate high-efficiency zero-emission heavy-duty vehicle (zHDV) powertrains that provide a range of 800 km without refueling or recharging. Powertrain components and their corresponding thermal components account for a large part of the production costs. For vehicle users higher costs are only acceptable if a significantly higher benefit can be achieved. Therefore it is important to size these components for the actual vehicle mission to avoid oversizing. In this paper an optimization method which determines the optimum component sizes for a given mission scenario under consideration of multiple criteria (e.g. costs performance and range) is presented.

Hydrogen fuel cell vehicles (HFCVs) are vital for advancing the hydrogen economy and decarbonizing the transportation sector. However research on HFCV market dynamics in passenger vehicles is limited especially incorporating both market competition from other vehicle types and the comprehensive supply–demand market dynamics. To bridge this gap our study proposed a spatial agent-based model to simulate the HFCV market evolution with the aim of finding effective strategies and policy implications for breaking the diffusion dilemma of the HFCV market. We calibrated the model using survey data (N=1065) collected from Beijing and evaluated its performance across five “What-If” scenarios. Results indicate that HFCVs and hydrogen stations are difficult to penetrate under the current conditions despite HFCV applicants and market share growing by 37.5% and 15.63% respectively. Consumer perceptions on cost social and environment have greater impacts on HFCV proliferation than facility availability. The HFCV purchase subsidy has much greater impact than the technological learning rate greatly accelerating its market emergence timing. Finally HFCVs’ diffusion significantly influences the market of battery electric vehicles.