Energy Effectiveness and Operational Safety of Low-Powered Ocean-going Cargo Ship in Various (Heavy) Operating Conditions

The shipping industry, which remains the backbone of international merchandise trade, is striving to reduce its operational cost and more importantly its environment impact. New ships need meet the EEDI (Energy Efficiency Design Index) requirements of IMO (International Maritime Organization). However, the current EEDI is not able to accurately evaluate the real lifetime carbon emissions of the ship. Under the guidance of current EEDI regulation, the ship designers, owners and policymakers could be misled to adopt the configurations that are underperforming or even leading to an increase of CO2 emissions in reality. A technically easy and effective solution to meet the EEDI requirement is to lower the installed engine power and thus the ship design speed. However, reducing the installed engine power could lead to an underpowered ship, which could have insufficient power for propulsion and steering in adverse weather conditions.
The main research question addressed in this dissertation is:
What is the transport performance of ocean-going cargo ships with small EEDI when sailing in realistic operating conditions; are these ships safe when sailing in heavy operating conditions; and, how to improve both the transport performance and operational safety of ocean-going cargo ships by using the short-term applicable ship propulsion options?
The ship transport performance investigated in this dissertation includes the energy conversion performance, fuel consumption performance and emissions performance. The influences of the operational ship speed reduction, propulsion control, PTO (power-take-off)/PTI (power-take-in), and using LNG (liquefied natural gas) as the fuel as well as the combination of these measures on the ship transport performance have been systematically investigated.
The operational safety investigated in this dissertation includes both engine operational safety and ship operational safety. The engine dynamic behaviour during ship acceleration, deceleration, crash stop, and turning in normal sea condition have been investigated. The ship propulsion and manoeuvring performance when sailing in head sea, accelerating in head sea and turning to head sea in adverse sea conditions have been investigated. The influences of propeller pitch and PTO/PTI on the ship thrust limit and engine behaviour have also been investigated.
As a reflection of the research in this dissertation, suggestions on amendments of IMO’s current EEDI has been provided. The proposal for amending the current EEDI formula tries to make the EEDI calculation more realistic and representative when evaluating ship transport performance at the design stage. Moreover, it can also partly solve the other weakness of the current EEDI with respect to the issues of underpowered ships.