Canberk Hazar

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 carbon-free 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 “carbon-free 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.

Many different types of barriers have been developed because of ever-increasing environmental awareness and need to protect the marine environment from pollution. Most barriers comprise floating booms to block floating debris with a skirt or subsurface portion to trap oil. An alternative is air bubble barriers, which have several advantages over traditional booms for protecting permanent structures like harbor entrances and water intakes. This study investigates the use of air bubble barriers as an oil spill containment technique. Eleven marine professionals with an average of 15 years experience participated in a SWOT-Interval Type-2 Fuzzy Analytical Hierarchy Process (IT2-FAHP). In-depth interviews and literature review of studies of air bubble barriers were conducted to establish the SWOT critera and sub-criteria. The main critera identified was strengths, with a score of 0.459, while the top-prioritized sub-critera was “Unlike traditional oil containment booms, the fastest response to the spread of oil spills”, with a score of 0.187.

Timing is vital for oil spill response operations. However, deployment of the traditional response equipment, unfortunately, takes much more time. Therefore, innovative solutions are needed to minimize time losses. One of these innovative solutions is the air bubble barrier. Air bubble barrier creates a barrier to anything floating in the water, especially keeping the floating oil and petroleum in the area where it is spilled. Computational Fluid Dynamics simulation has grown in importance as a resource for air bubble barrier studies in recent years. Despite the extraordinary success of Reynolds Averaged Navier-Stoke applications on air bubble barriers, just a few studies concentrate on mesh sensitivity, one of the most fundamental issues with CFD methods. The main purpose of this study is to perform a mesh convergence study by simulating an air bubble barrier in the Simcenter STAR CCM+ software. In this context, in this simulation, a 2D numerical model is considered. The mesh convergence study has been performed by calculating the aperture inlet mean static pressure and the mean horizontal surface velocity. As a result, it is evident that the mesh base size and number of elements in mesh in case 10 can be employed to maintain the solution time-optimal state in the upcoming numerical simulations on the 2D and 3D air bubble barrier. Case 10 represents the mesh base size of 0.015 and the number of elements in mesh of 99042. Findings from this parametric study will be incorporated as mesh control rules into the subsequent 2D and 3D simulations of the air bubble barrier.

Because of the heat flow and temperature, marine diesel engine exhaust gas energy is by far the highest desirable among the waste heat sources of a ship. Waste heat recovery systems generate electrical power by using this exhaust gas energy. The goal of this study is to measure how much the power turbine generator improves the system's efficiency for 3 different engine loads and 3 different ambient conditions. This study presents a power turbine generator using a six-cylinder low-speed marine diesel engine. Analyses are performed by considering three different ambient conditions and three different diesel engine loads, and the exergy destruction of each component, exergy efficiency, exergy destruction rate, efficiency increases, and power output of the system is calculated. Besides that, the payback period is calculated according to the installation cost of the power turbine generator and the cost of the fuel saved annually. Based on the analysis, the highest power output for the power turbine generator occurred under 100% engine operating load and winter ambient conditions, and the lowest power output occurred under 75% engine operating load and tropical ambient conditions. On the other hand, for the same ambient conditions, the highest efficiency increase occurred at 90% engine operating load, and the lowest efficiency increase occurred at 100% engine operating load. In the power turbine generator, it is observed that the shortest payback period is 100% engine operating load and winter ambient condition.