Publications

Due to the random fluctuations in power experienced by high-temperature green electric hydrogen production systems further deterioration of spatial distribution characteristics such as temperature voltage/current and material concentration inside the solid oxide electrolysis cell (SOEC) stack may occur. This has a negative impact on the system’s flexibility and the corresponding control capabilities. In this paper based on the SOEC electrolytic cell model a comprehensive optimization method using an adaptive incremental Kriging surrogate model is proposed. The reliability of this method is verified by accurately analyzing the dynamic performance of the SOEC and the spatial characteristics of various physical quantities. Additionally a thermal dynamic analysis is performed on the SOEC and an adaptive time-varying LPV-MPC optimization control method is established to ensure the temperature stability of the electrolysis cell stack aiming to maintain a stable efficient and sustainable SOEC operation. The simulation analysis of SOEC hydrogen production adopting a variable load operation has demonstrated the advantages of this method over conventional PID control in stabilizing the temperature of the stack. It allows for a rapid adjustment in the electrolysis voltage and current and improves electrolysis efficiency. The results highlighted that the increase in the electrolysis load increases the current density while the water vapor electrolysis voltage and H2 flow rate significantly decrease. Finally the SOEC electrolytic hydrogen production module is introduced for optimization scheduling of energy consumption in Xinjiang China. The findings not only confirmed that the SOEC can transition to the current load operating point at each scheduling period but also demonstrated higher effectiveness in stabilizing the stack temperature and improving electrolysis efficiency.

Replacing the energy density and convenience of diesel fuel for all forms of fossil fuel-powered trains presents significant challenges. Unlike the traditional evolutions of rail which has largely self-optimised to different fuels and cost structures over 150 years the challenges now present with a timeline of just a few decades. Fortunately unlike the mid-1800s simulation and modelling tools are now quite advanced and a full range of scenarios of operations and train trips can be simulated before new traction systems are designed. Full trip simulations of large heavy haul trains or high speed passenger trains are routinely completed controlled by emulations of human drivers or automated control systems providing controls of the “virtual train”. Recent developments in digital twins can be used to develop flexible and dynamic models of passenger and freight rail systems to support the new complexities of decarbonisation efforts. Interactions between many different traction components and the train multibody system can be considered as a system of systems. Adopting this multi-modelling paradigm enables the secure and integrated interfacing of diverse models. This paper demonstrates the application of the multi-modelling approach to develop digital twins for rail decarbonisation traction and it presents physics-based multi-models that include key components required for studying rail decarbonisation problems. Specifically the challenge of evaluating zero-emission options is addressed by adding further layers of modelling to the existing fully detailed multibody dynamics simulations. The additional layers detail control options energy storage the alternate traction system components and energy management systems. These traction system components may include both electrical system and inertia dynamics models to accurately represent the driveline and control systems. This paper presents case study examples of full trip scenarios of both long haul freight trains and higher speed passenger trains. These results demonstrate the many complex scenarios that are difficult to anticipate. Flowing on from this risks can be assessed and practical designs of zero-emission systems can be proposed along with the required recharging or refuelling systems.

This study presents a comprehensive optimization of a tri-generation system that integrates dual geothermal wells Liquefied Natural Gas (LNG) cold energy recovery and hydrogen production using an advanced Response Surface Methodology (RSM) approach. The system combines two geothermal wells with different temperature profiles power generation via an Organic Rankine Cycle (ORC) and hydrogen production through a Proton Exchange Membrane (PEM) electrolyzer enhanced by integrated LNG regasification for improved energy recovery. The primary novelty of this work lies in the first application of RSM for multi-objective optimization of geothermal-based tri-generation systems moving beyond the conventional single-objective approaches. A 40-run experimental design is employed to simultaneously optimize three critical performance indicators: exergy efficiency power-specific cost and hydrogen production rate considering six key operating parameters. The RSM framework enables systematic exploration of parameter interactions and delivers statistically validated predictive models offering a robust and computationally efficient optimization strategy. The optimized system achieves outstanding performance with an exergy efficiency of 44.60% a competitive power-specific cost of 19.70 $/GJ and a hydrogen production rate of 5.15 kg/hr. Comparative analysis against prior studies confirms the superiority of the RSM-based approach demonstrating a 1% improvement in exergy efficiency (44.60% vs. 44.16%) a significant 44.1% increase in hydrogen production rate (5.15 kg/hr vs. 3.575 kg/hr) and a 0.81% reduction in power-specific cost compared to genetic algorithm-based optimization.

The shipping industry remains heavily dependent on heavy fuel oils which account for approximately 77% of fuel consumption and contribute significantly to greenhouse gas (GHG) emissions. In line with the IMO’s decarbonization targets ammonia has emerged as a promising carbon-free alternative. This study evaluates the strategic viability of ammonia especially green production as a marine fuel through a hybrid SWOT–Best–Worst Method (BWM) analysis combining literature insights with expert judgment. Data were collected from 17 maritime professionals with an average of 15.7 years of experience ensuring robust sectoral representation and methodological consistency. The results highlight that opportunities hold the greatest weight (0.352) particularly the criteria “mandatory carbonfree by 2050” (O3:0.106) and “ammonia–hydrogen climate solution” (O2:0.080). Weaknesses rank second (0.270) with “higher toxicity than other marine fuels” (W5:0.077) as the most critical concern. Strengths (0.242) underscore ammonia’s advantage as a “carbonfree and sulfur-free fuel” (S1:0.078) while threats (0.137) remain less influential though “costly green ammonia” (T3:0.035) and “uncertainty of green ammonia” (T1:0.034) present notable risks. Overall the analysis suggests that regulatory imperatives and environmental benefits outweigh safety technical and economic challenges. Ammonia demonstrates strong potential to serve as viable marine fuel in achieving the maritime sector’s long-term decarbonization goals.

The global shift towards cleaner energy sources is driving the adoption of hydrogen as an environmentally friendly alternative to fossil fuels. Among the forms currently available Liquid Hydrogen (LH2) offers high energy density and efficient storage making it suitable for large-scale transport by rail. However the flammability of hydrogen poses serious safety concerns especially when transported through confined spaces such as railway tunnels. In case of an accidental LH2 release from a freight train the rapid accumulation and potential ignition of hydrogen could cause catastrophic consequences especially if freight and passenger trains are present simultaneously in the same tunnel tube. In this study a three-dimensional computational fluid dynamics model was developed to simulate the dispersion and explosion of LH2 following an accidental leak from a freight train’s cryo-container in a single-tube double-track railway tunnel when a passenger train queues behind it on the same track. The overpressure results were analyzed using probit functions to estimate the fatality probabilities for the passenger train’s occupants. The analysis suggests that a significant number of fatalities could be expected among the passengers. However shorter users’ evacuation times from the passenger train’s wagons and/or longer distances between the two types of trains might reduce the number of potential fatalities. The findings by providing additional insight into the risks associated with LH2 transport in railway tunnels indicate the need for risk mitigation measures and/or traffic management strategies.

Solid oxide electrolysis (SOEL) is considered an efficient option for largely emission-free hydrogen production and thus for supporting the decarbonization of the process industry. The thermodynamic advantages of high-temperature operation can be utilized particularly when heat integration from subsequent processes is realized. As the produced hydrogen is usually required at a higher pressure level the operating pressure of the electrolysis is a relevant design parameter. The study compares pressurized and near-atmospheric designs of 126 MW SOEL systems with and without the integration of process heat from a downstream ammonia synthesis and the inefficiencies that occur in the processes. Furthermore process improvements by sweep-air utilization are investigated. Pinch analysis is applied to determine the potential of internal heat recovery and the minimum external heating and cooling demand. It is shown that pressurized SOEL operation does not necessarily decrease the overall power consumption for compression due to the high power requirement of the sweep-air compressor. The exergetic efficiencies of the standalone SOEL processes achieve similar values of = 81 %. Results further show that integrating the heat of reaction from ammonia synthesis can replace almost the entire electrically supplied thermal energy thereby improving the overall exergetic efficiency by up to 3.5 percentage points. However the exergetic efficiency strongly depends on the applied air ratio. The highest exergetic efficiency of 86 % can be achieved by employing sweep-air utilization with an expander. The results demonstrate that integrating downstream process heat and applying sweep-air utilization can significantly enhance overall efficiency and thus reduce external energy requirements.

Considering rising environmental concerns and the energy transition towards sustainable energy Singapore’s power sector stands at a crucial juncture. This study explores the integration of grid infrastructure with both generated and imported renewable energy (RE) sources as a strategic pathway for the city-state’s energy transition to reach net-zero carbon emissions by 2050. Employing a combination of simulation modeling and data analysis for energy trading and advanced energy management technologies we examine the current and new grid infrastructure’s capacity to assimilate RE sources particularly solar photovoltaic and energy storage systems. The findings reveal that with strategic upgrades and smart grid technologies; Singapore’s grid can efficiently manage the variability and intermittency of RE sources. This integration is pivotal in achieving a higher penetration of renewables as well as contributing significantly to Singapore’s commitment to the Paris Agreement and sustainable development goals. While the Singapore’s power system has links to the Malay Peninsula the planned ASEAN regional interconnection might alter the grid operation in Singapore and possibly make Singapore a new green energy hub. The study also highlights the key challenges and opportunities associated with cross-border energy trade with ASEAN countries including the need for harmonized regulatory frameworks and incentives to foster public–private partnerships. The insights from this study could guide policymakers industry stakeholders and researchers offering a roadmap for a sustainable energy transition in Singapore towards meeting its 2050 carbon emission goals.

Crude oil accounts for approximately 40% of global energy consumption and the refining sector is a major contributor to greenhouse gas (GHG) emissions particularly through the production of hard-to-abate fuels such as aviation fuel and fuel oil. This study disaggregates the refinery into its key process units to identify decarbonization opportunities along the entire production chain. Units are categorized into combustion-based processes— including crude and vacuum distillation hydrogen production coking and fluid catalytic cracking—and non-combustion processes which exhibit lower emission intensities. The analysis reveals that GHG emissions can be reduced by up to 60% with currently available technologies without requiring major structural changes. Electrification residual heat recovery renewable hydrogen for desulfurization and process optimization through digital twins are identified as priority measures many of which are also economically viable in the short term. However achieving full decarbonization and alignment with net-zero targets will require the deployment of carbon capture technologies. These results highlight the significant potential for emission reduction in refineries and reinforce their strategic role in enabling the transition toward low-carbon fuels.

Hydrogen is a promising fuel in the current transition to zero-net CO2 emissions. However most practical combustion equipment is not yet ready to burn pure hydrogen without adaptation. In the meantime blending hydrogen with natural gas is an interesting option. This work reports a computational study of the performance of swirl-stabilized natural gas/hydrogen flames in a novel combustion chamber design. The combustor employs an air-staging strategy introducing secondary air through a top-mounted plenum in a direction opposite to the fuel jet. The thermal load is fixed at 5 kW and the effects of fuel composition (hydrogen molar fraction ranging from zero to one) excess air coefficient (λ = 1.3 1.5 or 1.7) and primary air fraction (α = 50–100%) on the velocity temperature and emissions are analysed. The results show that secondary air changes the flow pattern reducing the central recirculation zone and lowering the temperature in the primary reaction zone while increasing it further downstream. Secondary air improves the performance of the combustor for pure hydrogen flames reducing NO emissions to less than 50 ppm for λ = 1.3 and 50% primary air. For natural gas/hydrogen blends a sufficiently high excess air level is required to keep CO emissions within acceptable limits.

Bioenergy is a promising alternative to fossil fuels-based energy with significant potential to transform global energy systems and promote environmental sustainability. This review provides a comprehensive overview of the evolution of bioenergy emphasizing its role in the global transition to sustainable energy. It explores a diverse range of biomass sources including forest and agricultural residues algae and industrial by-products and their conversion into energy via thermochemical biochemical and physicochemical pathways. The paper also highlights recent technological advancements and assesses the environmental sustainability of bioenergy systems. Additionally it examines key challenges hindering bioenergy development such as feedstock logistics technological limitations economic viability and policy gaps that need resolution to fully realise its potential. By synthesizing literature from 2010 to 2025 the review identifies strategic priorities for research and deployment aiming to inform efforts that align bioenergy utilization with global decarbonization goals.