Simulation of LNG-Battery hybrid tugboat under the influence of environmental loads and manoeuvre

Abstract

This paper presents a system modelling approach aimed at designing and simulating real-time conditions, with a specific focus on extreme scenarios to assess the impact on the annual CO₂ emissions and the consumption of LNG and batteries in a hybrid tugboat. Environmental variables such as wave period, wave height, current speed, and wind speed are considered. The tugboat system model is validated using manually logged historical operational data from a similar tugboat profile using both AMESIM and MATLAB\Simulink to simulate diverse environmental conditions and estimate annual fuel operational costs and emissions. A comparative analysis of the different system configurations is then conducted between traditional diesel, LNG and several control configurations of LNG-battery hybrid. Results demonstrate a significant reduction of 96.5% in CO₂ emissions and a 95.3% decrease in annual fuel operational costs with the adoption of LNG-battery hybrid propulsion with the rule-based control system. The study notes a slight increase in vessel operational time by 10.8%  due to higher wave heights and a 0.97% rise in added resistance from increased wind speed. Insignificant differences are observed in variations of wave period and current speed.  Additionally, the CII ratings of the different system configurations were then compared and concluded with the LNG-battery hybrid with a rule-based control system being the most environmentally and economically sustainable.