Jong Boon Ooi

Relying on fossil-fuel infrastructure creates environmental harm, price volatility, and geopolitical dependence that limit system efficiency. Accordingly, this work introduces a novel near-zero-emission biogas-based system in which the incorporation of a biogas combustor with a gas turbine, a transcritical CO2 power cycle, an LNG regasification and an electrolyzer enables electricity and hydrogen production along with useful hot and cold energy recovery. The configuration's primary innovation is the use of a CO2 capture method based on chemical absorption for post-combustion flue gas treatment and eventual sequestration. The proposed system is evaluated using a 5E assessment, parametric and sensitivity analysis and optimized using an intelligent beluga whale multi-objective optimization algorithm. According to the results, this system showcases impressive capabilities by registering reasonable energy and exergy efficiencies of 28.82% and 22.43%. A particularly noteworthy aspect of its operation is the substantial positive impact on environmental stewardship, which captures 5678 kg/h of CO₂ and significantly curtails the CO₂ released to only 141 kg/h. The economic viability of the system is also a strong point, so that the anticipated net present value (NPV of 27.103 M$) strongly suggests that this integrated configuration represents a sound economic venture for the future. The optimization framework finds the optimal configuration with an exergy efficiency of 28.18%, an NPV of 94.91 M$ and a unit cost of exergy product equal to 37.59 $/GJ. The sensitivity analysis indicates that the State 32 pressure (E-106 inlet pressure) is the most influential parameter and exerts a strong negative impact on system performance, such that increasing its value degrades efficiency and increases economic burdens.

Carbon-based quantum dots (CbQDs), encompassing carbon quantum dots (CQDs) and graphene quantum dots (GQDs), are an emerging class of nanomaterials with strong potential to serve as multifunctional fuel additives for compression ignition engines. This study presents the first focused critical review that consolidates and evaluates experimental findings reported in the literature on the combustion, performance, and emissions impacts of CbQDs in diesel-based fuels. Compared to broader carbonaceous nanomaterials, CbQDs offer unique advantages, including tunable surface functionality, nanoscale dispersion stability, and catalytic radical-generation potential. The review systematically analyzes experimental findings on the influence of CQDs and GQDs on ignition delay, fuel reactivity, brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), and key exhaust emissions including carbon monoxide (CO), unburned hydrocarbons (UHC), particulate matter (PM), and nitrogen oxides (NO _x ). Results indicate that CbQDs can reduce BSFC and emissions of CO, UHC, and PM by up to 6.8%, 31%, 45% and 90% respectively, while enhancing BTE by up to 6.6% depending on formulation and dosing. However, NO _x behavior remains formulation-dependent and often presents trade-offs. Despite encouraging outcomes, the review identifies major gaps in mechanistic understanding, standardization, long-term durability, and real-world validation. Key directions for future work are proposed, including deeper diagnostics, techno-economic analysis, and environmental risk assessments to support scalable deployment. This synthesis offers essential guidance for researchers and developers advancing next-generation, nanotechnology-enhanced diesel engine technologies.